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Texas Instruments WiLinkT™ 8 WLAN Features (Rev. A) User guides
WiLink™ 8 WLAN Features
User's Guide
Literature Number: SWRU423A
July 2015 – Revised May 2016
Contents
1
2
3
4
5
2
Trademarks ......................................................................................................................... 5
Introducion .......................................................................................................................... 5
2.1
Scope ...................................................................................................................... 5
2.2
Acronyms Table .......................................................................................................... 5
2.3
WiLink 8 Specification ................................................................................................... 7
General Features.................................................................................................................. 8
3.1
Supported Rates ......................................................................................................... 8
3.2
High-Throughput (HT) Features ........................................................................................ 9
3.3
Quality of Service (QoS) ............................................................................................... 12
....................................................................................................... 13
................................................................................................. 14
3.6
WoW (Wake on WLAN) ................................................................................................ 14
3.7
Set TX Power ........................................................................................................... 15
3.8
5-GHz Antenna Diversity .............................................................................................. 15
3.9
Wi-Fi – Bluetooth/Bluetooth Smart Coexistence.................................................................... 16
3.10 Wi-Fi – ZigBee Coexistence........................................................................................... 16
3.11 Accurate Synchronization Over Wi-Fi ................................................................................ 17
Single Role: Station ............................................................................................................ 17
4.1
Scanning ................................................................................................................. 17
4.2
Connection............................................................................................................... 19
4.3
Disconnection ........................................................................................................... 21
4.4
DHCP Client ............................................................................................................. 22
4.5
Security .................................................................................................................. 22
4.6
Filtering................................................................................................................... 22
4.7
Auto ARP ................................................................................................................ 23
4.8
Preferred Networks (Profiles) ......................................................................................... 23
4.9
Power-Save Mode ...................................................................................................... 24
4.10 Power-Save Delivery Protocols ....................................................................................... 25
4.11 Keep-Alive Mechanism................................................................................................. 25
4.12 Smart Config ............................................................................................................ 25
4.13 Regulatory Domain ..................................................................................................... 26
4.14 DFS Slave (Channel Switch) .......................................................................................... 26
4.15 Roaming ................................................................................................................. 26
Single Role: AP .................................................................................................................. 28
5.1
Connection............................................................................................................... 28
5.2
Hidden SSID............................................................................................................. 28
5.3
Security .................................................................................................................. 28
5.4
Regulatory Domain ..................................................................................................... 29
5.5
AP Scan .................................................................................................................. 29
5.6
Automatic Channel Selection (ACS) ................................................................................. 29
5.7
Maximum Connected Stations ........................................................................................ 29
3.4
Protection Types
3.5
Suspend and Resume
Table of Contents
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6
7
8
9
5.8
Aging ..................................................................................................................... 30
5.9
DFS Master .............................................................................................................. 30
5.10
Access Control .......................................................................................................... 31
5.11
Extreme Low Power (ELP) ............................................................................................ 31
Single Role: P2P
................................................................................................................ 31
6.1
P2P Device .............................................................................................................. 32
6.2
PSP Client ............................................................................................................... 32
6.3
P2P GO .................................................................................................................. 33
Single Role: Mesh
.............................................................................................................. 33
7.1
Supported Modes ....................................................................................................... 34
7.2
Hardware and Software Requirements .............................................................................. 34
7.3
Capabilities .............................................................................................................. 35
Multi-Role .......................................................................................................................... 35
8.1
General Overview....................................................................................................... 35
8.2
Limitations ............................................................................................................... 36
Performance ...................................................................................................................... 36
9.1
Single-Role .............................................................................................................. 37
9.2
Multi-Role ................................................................................................................ 37
9.3
AP and mBSSID (Dual AP) Fairness ................................................................................ 39
........................................................................................ 41
Revision History .......................................................................................................................... 43
9.4
Bluetooth WLAN Coexistence
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List of Figures
1
A-MPDU Aggregation ...................................................................................................... 11
2
Legacy, Mixed and Greenfield Preamble Structures .................................................................. 12
3
5-GHz Antenna Diversity .................................................................................................. 15
4
Wi-Fi – Bluetooth/Bluetooth Smart Coexistence – Shared Antenna
5
Wi-Fi – ZigBee Coexistence – GPIOs Interface ........................................................................ 16
6
Mesh Network Topology................................................................................................... 33
................................................
16
List of Tables
1
WiLink 8 Family .............................................................................................................. 5
2
Acronyms Table .............................................................................................................. 5
3
WiLink 8 Specification ....................................................................................................... 7
4
RF Modes ..................................................................................................................... 8
5
Multi-Role Combinations .................................................................................................... 8
6
WiLink 8 802.11b Supported PHY Rates ................................................................................. 8
7
WiLink 8 802.11a/g Supported PHY Rates............................................................................... 9
8
WiLink 8 802.11n Supported PHY Rates ................................................................................. 9
9
QoS Access Categories ................................................................................................... 13
10
QoS TIDs .................................................................................................................... 13
11
Scan Types
12
One-Shot Scan ............................................................................................................. 18
13
OS Scan ..................................................................................................................... 18
14
Connection Scan ........................................................................................................... 19
15
Beacon Filtering Parameters
16
17
18
19
20
21
22
23
24
4
.................................................................................................................
.............................................................................................
Estimated Roaming Timing ...............................................................................................
DFS Time Requirements ..................................................................................................
Mesh Network Capabilities ................................................................................................
Supported Multi-Role Combinations .....................................................................................
Single-Role Performance..................................................................................................
Multi-Role Throughput Benchmark.......................................................................................
AP Fairness: 1-to-10 Stations Throughput Distribution ...............................................................
AP Fairness: 10 Stations Connected to AP Throughput Distribution ................................................
WLAN Single Role – Bluetooth Coexistence ...........................................................................
List of Figures
17
23
27
30
35
36
37
38
39
40
41
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User's Guide
SWRU423A – July 2015 – Revised May 2016
WiLink™ 8 WLAN Features Guide
This document provides detailed information about various WiLink 8 and Wi-Fi® features, as well as TI
proprietary enhancements. The document does not provide the complete application programming
interface (API) set, but a high-level overview of the features. The WiLink 8 Linux® software package
(NLCP) is based on the open source mac802.11 implementation; the complete API can be found in:
http://lxr.free-electrons.com/source/net/mac80211/.
1
Trademarks
WiLink is a trademark of Texas Instruments.
Bluetooth is a registered trademark of Bluetooth SIG, Inc.
Linux is a registered trademark of Linus Torvalds.
Wi-Fi is a registered trademark of Wi-Fi Alliance.
All other trademarks are the property of their respective owners.
2
Introducion
2.1
Scope
This document covers the entire WiLink 8 family, including WL1807MOD, WL1837MOD, WL1835MOD,
WL1831MOD, WL1805MOD, WL1801MOD, and WiLink8Q (Automotive) including WL180xQ, WL183xQ,
WL187xQ. For more information about WiLink8Q, contact your local FAE.
Table 1. WiLink 8 Family
2.2
WiLink8.0
Description
WL1807MOD
Industrial dual band combo, 2x2 MIMO Wi-Fi module
WL1837MOD
Industrial dual band, 2x2 MIMO Wi-Fi, Bluetooth® and Bluetooth Smart module
WL1835MOD
Single band combo 2x2 MIMO Wi-Fi, Bluetooth and Bluetooth Smart module
WL1831MOD
Single band combo Wi-Fi, Bluetooth and Bluetooth Smart module
WL1805MOD
Single band, 2x2 MIMO Wi-Fi module
WL1801MOD
Single band Wi-Fi module
Acronyms Table
Table 2. Acronyms Table
Acronyms
A2DP
Description
Advance Audio Distribution Protocol
AC
Access Catetory
ACL
Asynchronous Connectionless Link
ACS
Automatic Channel Selection
AP
APUT
ARP
BA
BSS
BR
Wi-Fi Access Point
Access Point Under Test
Address Resolution Protocol
Block Acknowledgment
Basic Service Set
Basic Rate (for Bluetooth)
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Introducion
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Table 2. Acronyms Table (continued)
Acronyms
BT
Bluetooth
CDMA
Code Division Multiple Access
COEX
Co-Existence
CTS
Clear-to-Send
DFS
Dynamic Frequency Selection
DPDT
Double Pole, Double Throw
DPMS
Dynamic Power Mode Switch
DSSS
Direct Sequence Spread Spectrum
DUT
EDCA
Device Under Test
Enhanced Distributed Channel Access
EDR
Extended Data Rate (for Bluetooth)
ELP
Extreme Low Power
ESS
Extended Service Set
GO
P2P Group Owner
GUI
Graphical User Interface
HWMP
LAN
Hybrid Wireless Mesh Protocol
Local Area Network
MIMO
Multiple Input, Multiple Output
MAP
Mesh Access Point
MP
MPP
MR
Mesh Point
MPP Mesh Point
Multi Role
MRMC
Multi-Role Multi-Channel
OFDM
Orthogonal Frequency-Division Multiplexing
P2P
Wi-Fi Peer-to-Peer
PS
Power Save
RSSI
Receive Signal Strength Indicator
SCB
Shared Control Block
SG
Soft Gemini
SSID
Simple Service Set (Wi-Fi Network Name)
STA
Wi-Fi Station
SUT
STA Under Test
TDM
Time-Division Multiplexing
TIM
Traffic Indication Map
TXOP
Transmit Opportunity
WLAN
Wireless Local Area Network
U-APSD
6
Description
Unscheduled Automatic Power-Save Delivery
UPSD
Unscheduled Power Save Delivery
WMM
Wireless Multi-Media
WPS
Wi-Fi Protected Setup
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Introducion
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2.3
WiLink 8 Specification
Table 3. WiLink 8 Specification
Role
Feature
Description
Configuration
General
802.11b/g
Supported
Not Configurable
802.11a
Supported (WiLink8.0 Platform Dependent)
Not Configurable
802.11n
Supported
hostapd.conf (AP only)
RF Modes
See Table 4
wlconf
A-MSDU
Supported for RX only
wlconf
RIFS
Supported for RX only
Not Configurable
BA Sessions
TX: 10 / RX: 10
Not Configurable
Greenfield
Supported
Not Configurable
QoS (WMM)
Supported
hostapd.conf (AP only)
TX Power
Supported
wlconf
5GHz Antenna Diversity
Supported (WiLink8.0 Platform Dependent)
wlconf
Wi-Fi–Bluetooth/Bluetooth Smart
Coexistence
Supported (WiLink8.0 Platform Dependent)
Not Configurable
Wi-Fi–ZigBee Coexistence
Supported (HW modification is required)
wlconf
Wi-Fi Protected Setup (WPS)
WPSv2 (PIN, PBC)
Not Configurable
Security
Personal: Open, WEP 40/128, WPA/WPA2PSK
Enterprise: EAP, EAP-TLS, EAP-TTLS,
PEAPv0
Not Configurable
Filtering
ARP, Beacon, Multicast, Data
wlconf
Auto ARP
Supported
Not Configurable
Preferred Networks
Supported
wpa_supplicant.conf
Power Save Modes
Active, Auto, Forced (Legacy, U-APSD)
wlconf
Extreme Low Power
Supported
wlconf
Keep Alive
Supported
wlconf
Suspend/Resume
Supported (Edge only)
wlconf
Wake On WLAN
Supported
Not Configurable
Smart Config
Supported
Not Configurable
Regulatory Domain
Supported
wpa_supplicant.conf
Dynamic Frequency Selection
Slave
Supported
Not Configurable
Roaming
Supported
Not Configurable
Time Synchronization
Supported (HW modification is required)
wlconf
Wi-Fi Protected Setup (WPS)
WPSv2 (PIN, PBC)
hostapd.conf
Hidden SSID
Supported
hostapd.conf
Security
Personal: Open, WEP 40/128, WPA/WPA2PSK
Enterprise: Not Supported
hostapd.conf
Regulatory Domain
Supported
hostapd.conf
ACS
Supported
hostapd.conf
Number of Remote Peers
Up to 10 connected peers
Not Configurable
Aging
Supported
wlconf
Dynamic Frequency Selection
Master
Supported
Not Configurable
Access Control
Supported
hostapd.conf
Extreme Low Power
Supported
wlconf
STA
AP
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Table 3. WiLink 8 Specification (continued)
Role
Feature
Description
Configuration
P2P
Device Name
Supported
wpa_supplicant.conf
See Table 5
Not Configurable
Client
GO
MR
Multi-Role Combinations
Table 4. RF Modes
Band
Role
STA
2.4GHz
5GHz
20 MHz SISO
20 MHz SISO
40 MHz SISO
40 MHz SISO
20 MHz MIMO
AP
P2P
20 MHz SISO
20 MHz SISO
20 MHz MIMO
40 MHz SISO
20 MHz SISO
20 MHz SISO
20 MHz MIMO
40 MHz SISO
Table 5. Multi-Role Combinations
Role
STA
AP
P2P CL
STA
AP
X
V
V
V
V
Same Channel
V
Same Channel
P2P CL
V
V
X
X
P2P GO
V
Same Channel
X
X
3
General Features
3.1
Supported Rates
P2P GO
WiLink 8 supports PHY rates according to the radio mode being used (SISO20/SISO40/MIMO20). The
expected RF performance (TX and RX) for the different rates is documented in the WL18xxMOD WiLink™
8 Single-Band Combo Module – Wi-Fi®, Bluetooth®, and Bluetooth Low Energy (BLE) Data Sheet
(SWRS152) and the WL18x7MOD WiLink™ 8 Dual-Band Industrial Module – Wi-Fi®, Bluetooth®, and
Bluetooth Low Energy (BLE) Data Sheet (SWRS170). For transmission, rates are selected by the rate
adaptation algorithm of the device to maximize the TP and minimize the power consumption of the device.
The different rates and their modulations are detailed in the following subsections.
3.1.1
11b Rates
The RF signal format used for 802.11b (see Table 6) is the complementary code keying (CCK). This is a
slight variation on code division multiple access (CDMA) that uses the basic direct sequence spread
spectrum (DSSS) as its basis.
Table 6. WiLink 8 802.11b Supported PHY Rates
8
Modulation
Bit Rate
Defined in
DBPSK
1 Mbps
802.11
DQPSK
2 Mbps
CCK
5.5 Mbps
CCK
11 Mbps
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3.1.2
11a/g Rates
The modulation scheme used in 802.11g is orthogonal frequency-division multiplexing (OFDM), copied
from 802.11a with data rates of 6, 9, 12, 18, 24, 36, 48, and 54 Mbit/s.
OFDM is a frequency-division multiplexing (FDM) scheme used as a digital multi-carrier modulation
method. A large number of closely-spaced orthogonal subcarrier signals are used to carry data on
several parallel data streams or channels. Each subcarrier is modulated with a conventional modulation
scheme (such as quadrature amplitude modulation or phase-shift keying) at a low symbol rate,
maintaining total data rates similar to conventional single-carrier modulation schemes in the same
bandwidth.
Table 7. WiLink 8 802.11a/g Supported PHY Rates
3.2
Data Rate [Mbps]
Modulation
Code rate
6
BPSK
½
9
BPSK
¾
12
QPSK
½
18
QPSK
¾
24
QAM-16
½
36
QAM-16
¾
48
QAM-64
½
54
QAM-64
¾
High-Throughput (HT) Features
The IEEE 802.11n task force defined a high-throughput (HT) extension to the legacy (a/b/g) WLAN
standards that increases transmission efficiency and throughput, and reduces compulsory overhead (by
adding a block-ack mechanism), packet aggregation to the MAC layer, and adopts higher rates. The
complete list of features is described in the following subsections.
3.2.1
11n Rates
WiLink 8 supports the PHY rates for both TX and RX (in Mbps) shown in Table 8.
Table 8. WiLink 8 802.11n Supported PHY Rates
2.4-GHz Band
SISO20
Index
(1)
(2)
LGI
(1)
5-GHz Band
MIMO20
SGI
(2)
Index
LGI
(1)
SISO20
SGI
(2)
Index
LGI
(1)
SISO40
SGI
(2)
Index
LGI
(1)
SGI
(2)
0
6.5
7.2
8
13
14.4
0
6.5
7.2
0
13.5
15
1
13
14.4
9
26
28.9
1
13
14.4
1
27
30
2
19.5
21.7
10
39
43.3
2
19.5
21.7
2
40.5
45
3
26
28.9
11
52
57.8
3
26
28.9
3
54
60
4
39
43.3
12
78
86.7
4
39
43.3
4
81
90
5
52
57.8
13
104
115.6
5
52
57.8
5
108
120
6
58.5
65
14
117
130
6
58.5
65
6
121.5
135
7
65
72.2
15
130
144.4
7
65
72.2
7
135
150
LGI – Long guard interval (800 ns) is the standard symbol guard interval used in 802.11 OFDM.
SGI – Short guard interval (400 ns) is an optional improvement of 11% to the data rate introduced in 802.11n.
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MIMO at 2.4 GHz
The use of multiple antennas and the antenna-based multiple input, multiple output (MIMO) technique is a
key feature of 802.11n equipment that sets itself apart from the earlier 802.11a/g equipment. This usage is
responsible for superior performance, reliability, and range.
MIMO systems (WiLink8.0 supports 2x2 MIMO) divide a data stream into multiple unique streams, each of
which is simultaneously modulated and transmitted through a different radio-antenna chain in the same
frequency channel. MIMO leverages environmental structures and takes advantage of multipath signal
reflections to improve radio transmission performance.
Through the use of multipath, each MIMO receive antenna-radio chain is a linear combination of the
multiple transmitted data streams. The data streams are separated at the receiver using MIMO algorithms
that rely on the estimates of the channels between each transmitter and receiver. Each multipath route
can then be treated as a separate channel creating multiple "virtual wires" over which to transmit signals.
MIMO employs multiple, spatially-separated antennas to take advantage of these "virtual wires" and
transfers more data. In addition to multiplying throughput, range is increased because of an antenna
diversity advantage as each receive antenna has a measurement of each transmitted data stream. With
MIMO, the maximum per channel data rate grows linearly with the number of different data streams
transmitted in the same channel.
3.2.3
40-MHz BW Operation
WiLink8.0 supports a practical approach of using 40-MHz channels, but in a 5-GHz band. Using 40-MHz
channels or the busy 2.4-GHz band is not advised; use the SISO20 or MIMO20.
Typically, 802.11n allows the configuration of 40-MHz wide channels. Because adjacent channels need a
slight gap between them (to separate them in the frequency band), a single 40-MHz channel has slightly
more than twice the bandwidth of two adjacent 20-MHz channels (because the inter-channel frequency
gap is now part of the actual channel space). Therefore, a 40-MHz 802.11n channel provides slightly
better than twice the throughput capacity of a single 20-MHz 802.11n channel. If an 802.11n transmitter is
operating in a 20-MHz channel and can establish a 72.2-Mbps connection, then a 40-MHz channel would
provide a 150-Mbps connection; double the channel width to double (plus about 4%) the capacity of the
resultant double-wide 802.11n channel.
3.2.4
A-MPDU and A-MSDU
There are two methods available to perform frame aggregation: aggregate MAC protocol service unit (AMSDU) and aggregate MAC protocol data unit (A-MPDU). The main distinction between MSDU and
MPDU is that the former corresponds to the information that is imported to or exported from the upper part
of the MAC sublayer from or to the higher layers, respectively, whereas, the later relates to the information
exchanged from or to the PHY by the lower part of the MAC. Aggregate exchange sequences are made
possible with a protocol that acknowledges multiple MPDUs with a single block ACK.
A-MSDU: The principle of the A-MSDU (or MSDU aggregation) is to allow multiple MSDUs to be sent to
the same receiver concatenated in a single MPDU. This improves the efficiency of the MAC layer,
specifically when there are many small MSDUs, such as TCP acknowledgments. The main motivations for
aggregation at the MSDU layer are:
• Ethernet is the native frame format for most clients
• Because the Ethernet header is much smaller than the 802.11 header, the multiple Ethernet frames
can be combined to form a single A-MSDU.
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WiLink8.0 supports A-MPDU for both TX and RX and A-MSDU for RX (see Figure 1).
Figure 1. A-MPDU Aggregation
The decision of using A-MSDU versus A-MPDU is a tradeoff between probability of error and
retransmission costs in an A-MSDU, versus MAC frame header overheads in an aggregate with A-MPDU.
In most real-world systems, the later wins and most systems implement A-MPDUs.
3.2.5
RIFS
Reduced interframe space (RIFS) was introduced in IEEE 802.11n to improve its efficiency. RIFS is the
time in microseconds by which the multiple transmissions from a single station are separated. RIFS is
used when no SIFS-separated response frames are expected from the receiver. The value of RIFS is 2 μs
for 802.11n phy.
WiLink8.0 supports RIFS in RX (mainly for Wi-Fi certification). For TX (like most other devices), WiLink8.0
uses A-MPDU, and chooses not to use RIFS.
3.2.6
BA Sessions
Block acknowledgment (BA) was initially defined in IEEE 802.11e as an optional scheme to improve the
MAC efficiency. Recently, ratified amendment 802.11n enhanced this BA mechanism, making support for
all 802.11n-capable devices (formally known as high throughput (HT) devices) mandatory.
Instead of transmitting an individual ACK for every MPDU (or frame), multiple MPDUs can be
acknowledged together using a single BA frame. Block-Ack (BA) contains a bitmap that accounts the
fragment number of the MPDUs to be acknowledged. Each bit of this bitmap represents the status
(success or failure) of an MPDU.
Block acknowledgment consists of setup and tear-down phases. In the setup phase, capability information
such as buffer size and BA policy are negotiated with the receiver. Once the setup phase completes, the
transmitter can send frames without waiting for an ACK frame. Finally, the BA agreement is torn down with
a DELBA frame.
WiLink8.0 supports BA session both for TX and RX.
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Greenfield
Greenfield mode is an operational mode of an 802.11n network that can maximizes the speed of data
transfers. The performance boost of the Greenfield mode comes with some significant costs in any
environment that includes pre-802.11n client radios.
WiLink8.0 supports all three possible modes: legacy, mixed, and Greenfield modes (see Figure 2).
Figure 2. Legacy, Mixed and Greenfield Preamble Structures
3.3
Quality of Service (QoS)
The purpose of WLAN QoS is to allow different types of traffic (voice, video, or normal traffic) to have
different priorities when approaching the air (trying to send a frame).
The WiLink8 device supports the enhanced distributed channel access (EDCA) QoS. With EDCA, highpriority traffic has a higher chance of being sent than low-priority traffic. On average, a station with highpriority traffic waits less time before it sends its packet than a station with low-priority traffic.
The levels of priority in EDCA are called access categories (ACs). The contention window (CW) can be
set according to the traffic expected in each access category, with a wider window needed for categories
with heavier traffic. The CWmin and CWmax values are calculated from aCWmin and aCWmax values,
respectively, that are defined for each physical layer supported by 802.11e.
EDCA provide four different ACs (from lowest to highest priority):
• Background (AC_BK)
• Best Effort (AC_BE)
• Video (AC_VI)
• Voice (AC_VO)
The WiLink8 devices (STA and AP) support the EDCA in both software and hardware: while the software
maintains the different AC queues, the hardware runs the “Air Approach” in real-time competition.
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Table 9 shows the default EDCA parameters.
Table 9. QoS Access Categories
AC
CWmin
CWmax
AIFSN
Max TXOP
Background (AC_BK)
15
1023
7
0
Best Effort (AC_BE)
15
1023
3
0
Video (AC_VI)
7
15
2
3.008 ms
Voice (AC_VO)
3
7
2
1.504 ms
The actual EDCA parameters are published by the AP side. When running a WiLink8 device as an AP
role, you can configure the EDCA parameters in the TI configuration file. There is no option to disable
QoS from the STA role (enabled by default), but there is an option in the hostapd.conf file to disable the
QoS.
A frame is handled as a QoS frame only if it arrived from the network with QoS information. Each frame
without QoS information is handled as a non-QoS frame. The default parameters of non-QoS frames are
the same as best-effort frames (that is also the case when the AP does not support QoS).
The EDCA QoS is compatible with the Wi-Fi Alliance WMM Certification, with a small modification. WMM
defines eight different TIDs (Traffic ID 0-7), while each traffic ID (TID) gets a specific AC handling.
In a WiLink8 solution, each TID is automatically assigned to its correlated AC (see Table 10).
Table 10. QoS TIDs
TID
AC
0
AC_BE
1
AC_BK
2
AC_BK
3
AC_BE
4
AC_VI
5
AC_VI
6
AC_VO
7
AC_VO
WiLink8.0 devices are fully compliant with Wi-Fi Alliance WMM requirements.
3.4
3.4.1
Protection Types
General
The protection mechanism preserves backwards-compatible interoperability with legacy devices
(802.11b/g) from over-the-air collisions as legacy devices cannot detect higher rate energy.
WiLink8 supports all protection methods using the standard mechanisms that are highlighted in
Section 3.4.2. For more information, see the 802.11n specification located at
https://en.wikipedia.org/wiki/802.11.
3.4.2
Protection Methods
When using 802.11g, RTS/CTS and CTS-to-self frames are used with legacy rates to protect 802.11b
stations higher rates transmissions.
When using 802.11n, The AP is responsible for the following Beacon Information Elements:
• ERP information element is added when the 802.11b station is part of the BSS and protection is
required.
• HT information element contains Operating Mode and Non-Greenfield STAs present fields to determine
whether or not to use protection
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Operating Mode has four possible settings:
– Mode 0: all stations in the BSS are 20/40-MHz HT capable, or if all stations in the BSS are 20-MHz
HT stations in a 20-MHz BSS
– Mode 1: there are non-HT stations or APs using the primary or secondary channels; also called HT
non-member protection mode.
– Mode 2: at least one 20-MHz station is associated to the HT BSS.
– Mode 3: at least one legacy station is associated to the HT BSS; also called non-HT mixed mode.
When using a 20- or 40-MHz HT channel, operating modes 1 or 3, and the Use Protection field is 1 in
the Beacon ERP IE, all HT transmissions must be protected using RTS/CTS or CTS-to-self sent legacy
rates. This can occur if there is a 802.11b/g/n device connected to the same AP.
There are two ways to protect the HT transmission:
• The device should send RTS/CTS or CTS-to-self prior to the HT transmissions in legacy rates.
• The device should use a non-HT/mixed mode preamble, with the first a transmitted PPDU.
The L-SIG value should protect the rest of the transmission. The remaining TXOP following the first PPDU
exchange may contain GF or RIFS sequences.
3.5
Suspend and Resume
The WiLink8.0 chip enters suspend mode when the host decides to enter suspend and sleep mode. In this
mode, the WiLink8.0 chip is turned off, allowing for power consumption efficiency. Before entering
suspend mode, all configurations are saved. Upon resume (usually triggered by pressing the keyboard or
touching the screen), the device is turned on, the wpa_supplicant starts a scan and reconnects to the AP
(assuming there is a saved profile).
Unlike Station mode (wpa_supplicant), Suspend/Resume in AP mode requires restarting the hostapd
application.
There is no resume due to any wireless activity, as the device is turned off.
3.6
WoW (Wake on WLAN)
WoW mode refers to the WLAN chip state when the host enters suspend. If WoW is enabled upon
suspend, the WiLink8.0 chip stays turned on, the Station remains connected, and AP keeps transmitting
beacons and preserves the links. In this state, a resume can also be triggered due to WLAN activity.
Use the following to configure the packet types to wake up:
1. Enable or disable broadcast frames
2. Configure filters on data packets, such as filter by source and destination MAC address, and so forth
3. Configure to wake up on the beacon IEs
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3.7
Set TX Power
WiLink8.0 has a TX power control mechanism for the STA mode in a 2.4-GHz band. TX power can be
reduced in case of a stable link. There are two potential advantages of reducing the TX power:
• Reducing current consumption
• Reduced interference range. Lower transmission power might interfere less with other devices. This
could lead to increased capacity of the network.
As a general guideline for WiLink8.0 current consumption, it is better to keep high TX power than to
decrease the TX rate and the throughput. Thus, TX power control is implemented only for the highest
supported rate per link. The decision to change the TX power level is based on the packet error rate
(PER) of the highest supported rate. If PER is low, then power can be reduced, otherwise power is kept
high.
3.8
5-GHz Antenna Diversity
WiLink8.0 supports two-antenna diversity on the 5-GHz band, using an external double pole, double throw
(DPDT) switch. This switch can be found on TI MOD1837.
The WiLink8.0 algorithm studies and analyzes the best signal path considering the reasons mentioned
earlier, choosing the better of the two paths for transmitting and/or receiving an RF signal to maximize the
likelihood that a packet will be correctly received, and increase throughput. The decision mechanism is
based on RSSI level. 5-GHz antenna diversity is mostly relevant for the following use-cases:
• In urban and indoor environments, there is no clear line of sight between the transmitter and receiver.
Instead, the signal is reflected along multiple paths before finally being received. Each of these
bounces can introduce phase shifts, time delays, attenuations, and distortions that can destructively
interfere with one another at the aperture of the receiving antenna.
• The antenna radiation pattern defines the variation of the power radiated by an antenna as a function
of the direction away from the antenna. This power variation as a function of the arrival angle is
observed at the antenna far field. Diversity between two antennas with different patterns can overcome
nulls.
• Improves performance for Airplay compliance (audio customers)
SoC
5GHz antenna port 1
WLAN 5GHz Tx
WLAN 5GHz Rx
5GHz antenna port 2
DPDT switch
control
Figure 3. 5-GHz Antenna Diversity
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Wi-Fi – Bluetooth/Bluetooth Smart Coexistence
Both WLAN and Bluetooth operate on a 2.4-GHz ISM band. Allowing the two technologies to work
simultaneously, especially when located on the same device, is a challenging task that requires special
treatment to keep performance quality on both sides. The advantage of having both Wi-Fi and
Bluetooth/Bluetooth Smart on a single combo device such as WiLink8.0 provides better correlation
between the different IPs to ensure good performance. WiLink8.0 uses a shared antenna for Wi-Fi and
Bluetooth.
This operation is accomplished by managing a time-division multiplexing (TDM) scheme; transmitting and
receiving independent signals over the shared antenna in an alternating pattern, using an external
controlled switch.
The WLAN both switches the antenna to the Bluetooth IP and protects BT traffic from any WLAN traffic by
other devices, using a number of different methods.
SoC
BT Tx/Rx
2.4GHz antenna port
WLAN BG2 Tx/Rx
RF switch
WLAN BG1 Tx/Rx
2 bit control
Figure 4. Wi-Fi – Bluetooth/Bluetooth Smart Coexistence – Shared Antenna
3.10 Wi-Fi – ZigBee Coexistence
WiLink8.0 introduces the Wi-Fi and ZigBee coexistence mechanism when using TI CC2530 for the
ZigBee. This coexistence is required when placing the WiLink8.0 and CC2530 on the same platform (for
example, ZigBee – Wi-Fi gateway). In that case, the isolation between the antennas of the two devices is
not enough to avoid impact on the performance. Without a proper coexistence mechanism, the RX of the
ZigBee device will be affected by the Wi-Fi TX and vice versa. The coexistence mechanism protects the
ZigBee RX using GPIOs interface between the devices. This allows the ZigBee visibility of the Wi-Fi
TX/RX activity, and also the ability to hold a Wi-Fi transmission.
Figure 5. Wi-Fi – ZigBee Coexistence – GPIOs Interface
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3.11 Accurate Synchronization Over Wi-Fi
For a variety of applications such as audio, industrial, and medical, there is a demand for accurate
synchronization between different Wi-Fi devices (for example, synchronization between left and right audio
speakers). The IEEE802.11 protocol does not allow a high level of synchronization due to its delays,
latency, and retries.
WiLink8.0 offers synchronization over Wi-Fi with an accuracy of less than 20 µs.
The WiLink8.0 solution for accurate time synchronization does not require the support of any dedicated
protocol such as 802.11V.
When used for AP mode, the time synchronization feature works in a way all WL8 connected devices will
be synchronized to the AP time domain. When used for Mesh role, the time is synchronized per zones. it
is required to determine in advance which mesh peer is the one that all other mesh peers in its zone need
to be synchronized to. The method can synchronize between as many devices as the AP can support.
The solution does not require a specific or a proprietary access point.
4
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4.1
Scanning
A transmitted signal is subject to reflections and refraction on walls, surfaces, and so forth. The receiving
node sees signals differing in phase and amplitude. All these signals superposition at the RX antenna,
causing an effect called “fading”. Using more than one antenna allows the evaluation of different multipath
scenarios to avoid or reduce the effects of fading and interferences.
Scanning is a process Wi-Fi devices use to detect other remote Wi-Fi devices (usually detection of access
points before connection). This process can also be used for environment status or other measurements.
There are three primary scan types: Table 11 describes their different purposes and execution. Each scan
completes in a different amount of time, depending on variables such as scan type, configuration, and
regulatory rules.
The scan execution in the system is independent and can be executed between other Wi-Fi activities.
When a scan is executed in parallel to those activities, it can impact things such as throughput or multirole (MR) scenarios.
Some typical examples:
• Multi-role scenario, where STA and AP roles run traffic to remote devices. Executing a scan impacts
the throughput by up to 80% (during the scan itself) each time a channel is scanned off.
• Multi-role scenario where STA is connected and AP is idle. Executing a scan could lower the
connection success rate of a remote STA to less than 100%.
This should be taken into account when frequently executing scans.
The examples in Table 11 describe the shortest, typical, and longest scan process.
Table 11. Scan Types
Scan
Approximate Duration
[msec]
Band
Channels
Type
Shortest
BG
1-11
Active
500
Typical
BG
1-11
Active
3000
A
36-161 (No DFS)
Active
Longest
BG
1-11
Active
A
36-161 (With DFS)
Active + Passive
J
12-14
Passive
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One-Shot Scan
The one-shot scan is a general name for non-periodic scan types.
Application Scan: The application configures all scan parameters, including the channel list and scan
type (active or passive).
Table 12. One-Shot Scan
Application Scan
Parameters
Scan type
Passive or active
SSID
ANY or specific
BSSID
ANY or specific, per channel
Band and Channel list
Up to 16 channel
Dwell time
Min, max per channel
Early termination conditions
Per channel
Scan logic
Firmware to scan the list of channels
Scan Results
Firmware filters according to SSID and BSSID parameter
Driver accumulates results during scan process
Driver issues scan complete to application
Driver provides API to read the results of scan (accumulated, with aging)
Operation System (OS) Scan: The supplicant configures SSID (usually ANY) and the WLAN driver
performs a one-shot scan on all allowed channels (according to the regulatory domain) in all relevant
bands according to the configured SSID.
This scan is typically used for a site survey by the graphical user interface (GUI), using the supplicant’s
control interface.
Table 13. OS Scan
OS Scan
Parameters
Scan type
Passive or active
SSID
ANY or specific
Scan Logic
Firmware to scan all allowed channels on all enabled bands
Scan Results
Firmware filters according to SSID parameter
Driver accumulates results during scan process
Driver issues scan complete to application
Driver provides API to read the results of scan (accumulated, with aging)
4.1.2
Connection Scan
This scan is also known as a Scheduled Scan.
The connection scan is a periodic process that scans a list of channels derived from a list of SSIDs, as
configured by the supplicant. The scan tries to find a matched SSID as part of the connection process.
The traditional approach of the host managing the periodic connection scans is not power efficient,
especially when no BSS networks are found and the host is forced to remain awake for the entire duration
of the connection scan cycles until an appropriate BSS is found.
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To solve this issue, the connection scan is performed and managed from the firmware, minimizing the
host involvement during the scan process, enabling the host to sleep for long periods.
Table 14. Connection Scan
Connect Scan
Parameters
Scan type
Passive, active, or active after passive (DFS), per channel
SSID List
Inclusion: up to 16 SSIDs (Each SSID is either public or hidden)
SNR, RSSI Filters
Threshold
Band and Channel list
Up to 41 channels
Dwell time
Min, max per channel
Termination conditions
On report, never or after number of cycles
Periodicity
Cycles list
Scan logic
In case of N (N=0 or more) hidden SSIDs, the firmware transmits, per cycle, per channel, 2*(broadcast_Probe_Request +
N*unicast_Probe_Request)
Scan Results
Firmware filters (optionally) the results according to SSID list and forwards the results that match an SSID
Driver stores the scan results and issues scan report event upon scan result
Driver issues scan complete to application
Driver provides an API to read the results of the scan (accumulated, with aging)
4.1.3
Background Scan
This scan is also known as a Continuous Scan.
The background scan maintains a list of BSS candidates for roaming purposes. Each time a scan is
finished or a roaming trigger is issued, the upper layer checks whether a roaming should be performed
and selects the best BSS in the list. The scan period is fully managed by the driver.
For more information, see Section 4.15.
4.2
Connection
A Wi-Fi connection is a process of establishing a link between two devices for further data exchange. The
Wi-Fi connection process usually consists of the following steps:
• Scanning
• Connection with or without privacy
• DHCP exchange
There are two methods to establish connection: manual and automatic. Each method has its own usage
and purpose.
4.2.1
Manual (Via Commands)
This connection type is established by invoking CLI commands. These CLI commands define a network
index, security type, SSID name, unicast scanning, and more.
More than one network might be defined, but only one will be enabled and selected for the connection.
Switch between the pre-defined profiles by selecting the known index.
The lifetime of these defined networks lasts until the next driver or platform restart. After the restart, no
network profile will exist.
This connection process is typical for systems with no upper application layer that can remember and
store all successful connections and record those as useful profile or preferred network (see
Section 4.2.2).
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Typically, this connection type requires a scanning operation to detect the neighbor APs, routers, or
hotspots to discover a required network for connection. However, the connection is also established as a
standalone action even if the scanning was not invoked. This is because the connection process itself has
its own inherent scanning (scheduled scan) that scans all channels and connects to the required network
if it exists, or continues to scan periodically until it sees the disconnect command or the role stop.
4.2.1.1
Connection Time
The connection time may vary between 50 msec to a few seconds. This variance is because the
connection process consists of a few independent processes, listed above, that have a duration that may
vary according to the configuration or network topology.
On top of the inherent components of the connection process, there are few environmental and system
reasons that impact the connection time, and cannot be expected or controlled.
The following three examples describe the shortest, typical, and longest connection process:
• Shortest connection process:
– No security usage, neither personal nor enterprise
– Highest RF modulation (PHY rate) usage
– No DHCP process for acquiring an IP address, but a usage of a pre-defined IP address
– Operation in a clean environment without any interference, such as WLAN, BT, and other
A usage of the above configuration is not recommended for the following reasons:
• The unsecured connection with unencrypted data may result in the system getting hacked, in
terms of stealing data or other damage to the network.
• The highest modulation usage during the connection process may lead to a less robust
connection, depending on the RF conditions.
• The static IP address usage may lead to an IP address conflict in the system, and block the
device from data exchange.
• Longest connection process:
– An Enterprise authentication process with certificates exchange
– Lowest RF modulation (PHY rate) usage
– Acquiring an IP address from a DHCP server located after a few routers within some enterprise
network
– Operation in a noisy environment, leading to a packet retransmission or to the whole process
repetition, if some packet is lost within the BT operation sharing the same antenna and operating
on a time-division basis. The antenna will be taken from the WLAN and packets might be lost.
In the above scenario, if the complete connection process must be repeated, it could take 3 to 5
seconds or more.
• Typical connection process:
– Non-enterprise environment, such as home, car, or other private networks
– Moderate RF modulation
– IP address acquisition from a local DHCP server (such as a router or a hotspot)
In this connection scenario, the typical connection time is 0.5 seconds, which consists of:
• 50-msec WLAN open connection
• 100-msec 4-way handshake for a private and a group key generation
• 300 msec for the IP acquisition using the DHCP process
4.2.1.2
Connection Success Rate
The connection success rate, or the number of successful connections out of the connection trials, is a
measure of system robustness and can indicate a system's ability to establish a WLAN connection once
invoked.
The expected rate of successful connections is 100% of the connection trials; however, it might be lower
due to environmental and system reasons. Often, those reasons cannot be controlled or expected.
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4.2.1.3
Connect to Best BSSID of the Configured SSID
In environments where few APs with the same SSID exist, such as an enterprise network or home
network that might have a router and repeater, the station may detect more than one AP. In this case, the
station selects an AP with a higher RSSI. The current AP's profile is temporarily stored and used by the
station for connection to any AP with the same SSID, in case of a disconnect from the original AP.
4.2.2
Automatic (Via Profiles)
Section 4.8 describes using the profiles in detail. Once one or more profiles are defined in the supplicant
responsible for the connection process, the device starts a process toward the connection. If an AP with
parameters suitable to one of defined profiles is detected, a connection is invoked.
4.2.3
Wi-Fi Protected Setup (WPS)
The WPS method is an additional way to establish a Wi-Fi connection. The WPS-capable devices declare
this capability in the beacons and probes. In this method, the connection is secured and the data
exchange encrypted. The WPS connection method is invoked in two ways: hardware and software. Both
the hardware and the software processes are invoked using one of two WPS connection methods: PBC or
PIN. When one device has started a WPS connection process, the second device has two minutes to
respond to the connection initiator device. After two minutes, the connection initiator stops the process.
An advantage in either WPS method is that the secured Wi-Fi network can be joined without knowing the
privacy key.
A disadvantage is that during the WPS connection process, no specific SSID is defined. This limitation can
result in a situation where two independent stations start a WPS process concurrently, for example, within
the two minute time frame, and the peer station will not know which of them to connect to. This situation is
called WPS overlapping. The peer station is only able to connect when one station terminates the WPS
connection process.
4.2.3.1
WPS PBC
The WPS push-button connection method is invoked by pushing a button on a device (the hardware
method), or by running a dedicated command or selecting an option from a menu (the software method).
In the Linux OS, the CLI command is used, and in the Android OS, the WPS connection is invoked by
selecting the WPS option in the menu. In both cases, the result will be the same; after a WPS-secured
negotiation process, a connection is established.
4.2.3.2
WPS PIN
A PIN method is another option for establishing the WPS connection. In this case, one Wi-Fi device has a
pre-defined PIN key printed on the label, usually 8 digits in length, while the other Wi-Fi device inserts this
key after starting the WPS connection process. The side with the pre-defined key is called Label and the
device inserting the key is called Keypad. Both relate to the PIN method. After inserting the key, the
connection process is the same as with the PBC method. An alternate method to the Label option is a
Display method. Usually, this case is used when the connection is established by commands, such as in
Linux OS, or from menu, such as in the Android OS.
4.3
Disconnection
Disconnection stops the connection between an AP and an STA.
It could occur for various reasons:
• In case of low RSSI, when the STA leaves the range and the signal is low, the STA cannot transmit or
receive data clearly, and disconnects.
• AP or router turn-off
• AP changes parameters such as SSID or authentication type
• Wrong security parameters or password
• Exceeded number of unacknowledged packets
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After the disconnection process, if the STA has any saved profiles, it starts to scan. If any candidate is
discovered, it connects.
4.4
DHCP Client
An IP address must be received for a network client (such as a station) to establish a connection with data
transfer to any WLAN network.
Unlike static IP configuration, where there is a set IP address, DHCP is a dynamic protocol that allows an
external server to lease IP configurations based on a defined pool of addresses. A DHCP process occurs
with every new connection, and an address is given to the station.
The advantage of DHCP over static IP is that addresses are not wasted and do not conflict with other
devices in the same network.
4.5
Security
Wireless encryption and authentication only allow devices with the corresponding authentication and
encryption types to be connected. To connect a wireless device to a certain router, the device also
requires the correct key (password).
4.5.1
Authentication Types
WiLink8 STA mode supports the following three authentication types: open, personal and enterprise.
The first is open, where it allows to authenticate only with open authentication AP.
The second is personal authentication, where the password is configured to the AP and the AP itself
authenticates the peer device using a password.
• Wi-Fi Protected Access (WPA)
• Wi-Fi Protected Access v2 (WPAv2)
The third is enterprise authentication, where a Radius server behind the AP authenticates the peer device.
• EAP
• EAP-TLS
• EAP-TTLS
• PEAPv0
• PEAPv1
4.5.2
Encryption Types
Each encryption type can be used with either authentication type.
• Open (no encryption)
• WEP (wireless equivalent protocol)
• TKIP (temporal key integrity protocol)
• AES (advanced encryption standard)
4.5.3
Broadcast Key Rotation (BKR)
Broadcast key rotation (also known as group key update) allows the access point to generate the best
possible random group key, and update all key-management capable clients periodically.
4.6
4.6.1
Filtering
Beacon Filtering
WLAN beacons are identical from one beacon to the other, in most cases, other than the timestamp (TSF)
and the Traffic Indication Map (TIM) information.
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The TSF and the TIM are handled by the firmware (for real-time purposes). The WiLink8 driver (and
supplicant) always receives one (first) beacon; the others are configurable. The host can configure to the
firmware which IEs are relevant and the firmware sends the driver only beacons with the configured IEs.
The host can configure for each relevant IE whether the Transfer, when there is a change in the IE's
content, or Relevant IE appears in the beacon. For the latter, the firmware saves the last beacon in its DB,
and compares the new beacon with the beacon from the DB. If there is a match, the entire beacon will be
sent to the host. Each IE that is not configured is handled as non-relevant and ignored.
Configure the IEs with TI wlconf file as shown in Table 15.
Table 15. Beacon Filtering Parameters
4.6.2
Parameter
Information
core.conn.bcn_filt_mode
Beacon Filter Enable and Disable
core.conn.bcn_filt_ie_count
Number of relevant IE’s in the table (up to 32)
core.conn.bcn_filt_ieXXX.ie
IE Id
core.conn.bcn_filt_ieXXX.rule
Action to be done
0 – Ignore
1 – Relevant IE (Check for Change)
2 – Transfer (if IE Exist send to host)
core.conn.bcn_filt_ieXXX.oui & type
Additional IE Information for Vendor Specific (221) IE
Multicast Filtering
Multicast filtering is done in the firmware level. On initialization, the multicast filter is disabled and all
multicast frames are sent to the host. To get only specific multicast frames, register to specific multicast
groups; only those groups will be filtered in, while all other multicast frames are dropped. The WiLink8
software supports up to eight different multicast groups that can be configured. The multicast filter should
only work for the STA role, as the AP role should distribute all multicast frames to all other devices.
4.7
Auto ARP
Address resolution protocol (ARP) translates IP addresses into MAC addresses and saves them in the
ARP table. Because network communication is done through MAC addresses, ARP is needed to
associate the specific IP address to its specific MAC address.
When any packet is sent and the destination IP address does not exist in the ARP table, an ARP request
packet is sent in broadcast to link the IP address and MAC address together. The relevant party of the IP
address answers with an ARP reply (not in broadcast).
Auto ARP is a mechanism that filters the ARP request packets sent in the network. These ARP request
packets are filtered from the Host in order to reduce the power consumption (The Host does not need to
wake up to send the reply).
When a packet is detected with an irrelevant IP address (not the station), the station drops the packet.
This is done by the firmware, and is not seen in the driver. When a packet is detected with a relevant IP
address, the firmware answers with an ARP reply, and no messages is seen on the driver level.
4.8
Preferred Networks (Profiles)
Preferred networks or profiles refer to Wi-Fi networks that you have explicitly pre-defined or that have
been learned and stored by WLAN-capable devices. A preferred network definition consists of a Wi-Fi
network name, security definition, hidden/non-hidden network, and a priority of network.
These networks are written in the WLAN supplicant configuration file and used for automatic connection
once one or more of them have been discovered during a scan phase initiated by an application that
intends to invoke connection. The decision to start a connection scan varies between operating systems
and applications that manage connection. Typically, once Wi-Fi is enabled on the device, and one or more
profiles are defined, the scanning starts.
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After getting a scan result, the device checks one or more networks that are suitable to one of stored
profiles that were detected. In case of suitability, the device will invoke a connection to this device. The
suitability is expressed in the same network name and security type. However, in case of a network with
security, if the profile's security type is correct - but the security key is wrong, the connection process will
start - but a complete connection will fail. After the scan cycle, if there is more than one match with the
stored profiles’ list, the user that manages the connection process will prefer the Wi-Fi network with the
higher RSSI. However, the selection depends on the user preferring to connect to the network with a
higher priority, actually, meaning to the last connected network.
4.8.1
Hidden Network
A Wi-Fi network might be defined so that it is invisible to Wi-Fi stations. A network's invisibility is
expressed by not advertising the network name in beacons and ignoring the received probe requests from
the Wi-Fi station. Such networks are called hidden networks. Their purpose is to avoid seeing or
connecting to undesirable Wi-Fi stations.
Practically, the only way to see or connect to a hidden network is with an explicit manual definition of a
profile suitable to this network. The exact name of the network and its security type must be known; the
profile's creation to this network will not be enough to permit connection to it. Such a profile must be
defined as a hidden network profile. The profile causes the connection manager to invoke a unicast scan,
which will look explicitly for a network with this name to broadcast a scan. When the hidden network
receives a scan request carrying its network name and responds to it, the scanning station is aware that
this network is available for connection.
The number of the unicast probe requests transmitted during each scan interval is derived from the
number of hidden networks that are defined.
4.9
Power-Save Mode
As long as the WLAN on the chip works, power is consumed. When working without a constant
connection to electricity, it is important to reduce the current consumption of the device. However, to save
power and maintain acceptable performance, there must be a power-saving mechanism.
When the STA enters power-save mode, the WLAN on the chip goes into sleep mode (extreme low-power
(ELP) mode), drastically decreasing power usage.
4.9.1
Active
In this mode, the WLAN on the chip always stays awake, even if there is no activity such as traffic, scans,
and so forth. This mode is not efficient for power consumption; however, it achieves the best
performance.
4.9.2
Auto Power-Save Mode
In this mode, the STA automatically switches between active and power-save mode.
When the STA is connected in idle mode and has no need to send or transmit any data, the STA is in
power-save mode. However, if the STA must perform any activity in the network, such as receiving traffic,
it sends a null data frame with the power save bit off. Thus, the STA is in active mode from that point until
the activity has been finished. After a pre-configured amount of time, the null data frame with the power
save bit on is sent to the access point, and the STA returns to power-save mode.
This ensures a balance between power consumption and best performance.
4.9.3
Forced Power-Save Mode
In this mode, the STA remains in sleep mode most of the time, even during intervals of receiving traffic.
The AP buffers the data destined to the STA in forced power-save mode and publicizes in its beacon that
it has data for the specific associated station. The STA is awakened by the predefined interval and
detected in the beacon of the AP if there is any data for the station in the AP’s buffer.
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When saved data is in the buffer, the STA sends a trigger packet that pulls the data from the AP. In the
data packets, the AP enables the bit that indicates “more data”, which lets the STA know it should stay
awake for more packets until it receives a frame from the access point indicating “no more data”. The
STA then returns to sleep and this cycle repeats itself.
4.10 Power-Save Delivery Protocols
There are two kinds of power-save delivery mechanisms when STA is configured to power save: legacy
power save and UPSD.
4.10.1
Legacy
In this mode, when the STA detects that the AP has data for it in the beacon frame, it sends a trigger
packet named PS-POLL to the AP. In response, the AP sends the first queued frame to the STA; if the
More Data field in this frame is on, it sends another PS-POLL frame to the AP. The STA continues to send
PS-POLL frames to receive all the queued frames, until there are no data packets left. After this, the
station returns to sleep until the next listening interval.
This method is suitable for very low data usage, as it is not efficient enough to pull each single packet.
4.10.2
U-APSD
The unscheduled automatic power-save delivery (U-APSD) mechanism is also known as wireless multimedia (WMM) power-save. Legacy power-save methods can decrease the quality of periodic bi-directional
traffic consisting of short frames as in VoIP. Because VOIP data should send data periodically on a fixed
time (20 msec. for VOIP call), the legacy mechanism is not efficient enough. The U-APSD mechanism
was built to optimize the legacy mechanism.
U-APSD is basically a polling scheme, similar to the legacy power-save delivery. However, in U-APSD
mode, any transmitted frame, while in power-save mode, acts as a polling frame and triggers the AP to
release a buffered frame from the same access category (AC) as the transmitted packet (the number of
frames that are released by the AP is configurable and determined during the connection phase). For
example, a voice packet releases only voice-buffered packets. If there are no transmitted packs, STA
sends QoS null data packets (after the AP publicizes in its beacon that it has data for the specific
associated station), which polls the buffered data. This is very efficient for bi-directional traffic streams,
such as VOIP call.
As the STA awakes from power save to transmit the data, the STA then takes advantage of it to get any
data buffered from the AP. This feature only works if the STA and AP are configured to WMM-enabled.
4.11 Keep-Alive Mechanism
In a network client (station), messages are sent to the current connected access point to keep the
connection during periods of idle activity. These messages are called Keep-Alive. Keep-Alive messages
are generated independently by the WLAN device (station) according to the host configuration, allowing
the host to optimize the length of its low power-time interval. The Keep-Alive messages are not sent from
the Host, thus, the mechanism improves the power consumption. Also, the frequency of messages have a
direct effect on power consumption; therefore, the longer the interval between Keep-Alive messages, the
more efficient in power consumption.
4.12 Smart Config
The Smart Config is a method to allow the WLAN device to be connected to the network without having to
configure the AP information on the device. This method is required for devices without a GUI or
keyboard. The main target of the procedure is to receive (over the air) the SSID and password of the AP
that the device should connect to, from a third-party device. Once the device gets these parameters, it
connects to the AP and obtains an IP address.
Use a third-party device to deliver the network parameters (SSID + password). Enter the WLAN device
into Smart Config mode by either pressing a button or simply turning on the device; the device then moves
to Sniff mode.
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The third-party device periodically transmits a SYNC pattern interlaced with the encoded SSID + password
of the AP. The WLAN device scans all channels, searching for the SYNC pattern. Once the WLAN device
finds the SYNC pattern, it tunes to the specific channel the pattern was found on, and starts receiving the
SSID + password. Once done, the device exits Smart Config mode and connects to the requested
network with the SSID + password.
4.13 Regulatory Domain
The regulatory domain feature implements the IEEE 802.11d specification. Each country has a different
list of channels in which it is allowed to operate. The AP is responsible to publish the country IE in its
beacons. This IE contains all the information regarding the country being operated in, the allowed
channels and allowed TX power on each channel. The STA must parse the country IE it receives (from
any beacon, even before a connection is established), and act according to its content. There are
separate IEs for 2.4-GHz and 5-GHz bands. The information from the country IE affects the way the STA
performs a scan on each channel (passive/active), and the TX power used on each channel.
4.14 DFS Slave (Channel Switch)
The dynamic frequency selection (DFS) channels are 5-GHz channels, 52 to 140, where radar can
operate. Channel switch is a mechanism implemented to avoid co-channel operation with radar systems.
This feature verifies that the STA does not transmit any packets in DFS channels upon radar detection.
The AP is the master and must detect the radar and notify the client-slave that should get the info from the
AP. The AP informs associated STAs that the AP is moving to a new channel and maintains the
association by advertising the switch using channel switch announcement elements (IE#37) in beacon
frames, probe response frames, and channel switch announcement frames, until the intended channel
switch time. The AP may force STAs in the BSS to stop transmissions until the channel switch takes
place, by setting the channel switch mode field in the channel switch announcement element to 1.
The channel switch should be scheduled so that all STAs in the BSS, including STAs in power-save
mode, have the opportunity to receive at least one channel switch announcement element before the
switch. An STA that receives a channel switch announcement element can choose not to perform the
specified switch and take alternative action instead. For example, it can choose to move to a different
BSS. An STA in a BSS that is not the AP must not transmit the channel switch announcement element.
4.15 Roaming
Roaming is a process of stations (SUT) switching from one BSS (AP) to another BSS within ESS (APs
with the same SSID within LAN). This behavior is used inside enterprise Wi-Fi networks to permit a
continuous and smooth usage of the network when moving within ESS boundaries. An enterprise network
can be an office, campus, airport, or any other environment that has more than one AP with the same
SSID, and connected to the common backbone. The roaming process should be seamless and as easy as
possible within the capabilities and limitations of the mechanism.
4.15.1
Roaming Mechanism
The roaming mechanism operates in station and connected states only. The mechanism might be enabled
only at the connection point. After connection, the process cannot be enabled or disabled.
The roaming process consists of a few segments:
1. Enabled mechanism (at the connection point)
2. Continuous searching for potential roaming candidates using a background scan
3. Decision to roam
4. Disconnect from the current connected AP
5. Connect to the candidate AP
4.15.1.1
Mechanism Enabling
The roaming mechanism might be enabled only at the connection point. The enabling of the mechanism is
done by defining parameters for the scan and a critical RSSI level.
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4.15.1.2
Roaming Candidates List
When a station is connected and the roaming mechanism is enabled, it starts to scan periodically; this
process is called a background scan. The scanning interval is defined during connection, and depends on
a customer's needs. The characteristic value is 10 seconds. During each scan instance, the station only
scans one channel. The purposes of the scan are to detect APs with SSID, like the currently connected
SSID of the AP, and to reveal its RSSI. Once an AP with the same SSID is detected, its channel is
scanned during each scan period, in addition to the regular one-by-one channel scan to get the updated
RSSI level information. The scan may be active, using probe requests and receiving probe responses, or
passive, by listening to AP beacons, depending on driver configuration and other aspects. All channels are
scanned according to a regulatory domain configuration.
If the RSSI level of the current connected AP decreases below the defined RSSI level threshold, the
station invokes a one-time scan instance on all channels within one scan interval. The purpose is to detect
a roaming candidate AP with a higher RSSI level, to avoid a performance degradation and a potential
disconnect. Then, it continues the one-by-one channel scanning.
4.15.1.3
A Decision to Roam
When a suitable AP is detected (with the same SSID), its RSSI level is compared with the RSSI level of
the currently connected AP. This comparison is done at any RSSI level of the currently connected AP and
regardless of the defined RSSI level threshold explained above.
Another reason to roam is if the currently connected AP disappears. In this situation, if a suitable AP was
detected beforehand, the station connects to it; otherwise, it invokes a scan to detect it. If no AP is
detected, the station disconnects and starts a periodic connect scan.
4.15.1.4
Connection to a Better AP
Once the station has decided to roam, due to one of the aforementioned reasons, it disconnects from the
currently connected AP, then connects to the candidate AP. The roaming process time varies between
150 ms and 800 ms, depending on security type, environmental congestion, and so forth. Table 16 shows
an example of roaming process time in a clean environment.
Table 16. Estimated Roaming Timing
4.15.2
Security
Estimated Roaming Time [msec]
Open
150
WPA2-PSK
200
WAP2-TLS (Enterprise)
200
Roaming Triggers
Roaming has two main triggers: low RSSI level and loss of AP beacons.
4.15.2.1
RSSI Level Delta
After detecting an AP with the same SSID, the RSSI level is compared to the RSSI level of the currently
connected AP. If the RSSI level of the detected AP is higher, the station will roam. This trigger is called
Low RSSI. The delta in the RSSI levels, between the currently connected AP and the candidate AP, varies
according to the RSSI level of the currently connected AP, with a variation between 1 to 5 dB.
4.15.2.2
APs Disappearing
The currently connected AP may disappear for different reasons, such as power interruption, unexpected
obstacles, or a very high interference. The disappearance is measured by a number of continuous, absent
beacons from the currently connected AP. If it crosses a defined threshold, the roaming is invoked. This
trigger is called BSS Loss.
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5.1
Connection
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The access point constantly transmits broadcast beacons with relevant information according to defined
configurations (security, SSID, PS, RSSI, SISO/MIMO, supported rates, regulatory domain IE, and WMM),
which allows other stations to know of its existence and capabilities. Once an external station detects the
beacons, the connection process can start.
The authentication process proceeds as follows:
1. Station sends an Auth packet to the AP.
2. AP replies with an Auth packet.
3. Station sends an Association Request packet that matches the capabilities of the AP.
4. AP accepts the connection, it sends an Association Response packet with a successful state.
If the AP is configured with security, the AP verifies the connection with keys.
1. AP sends an EAPOL-Key packet.
2. Station replies with an EAPOL-Key packet.
3. AP sends a third EAPOL-Key packet.
4. Station sends the fourth EAPOL-Key packet.
5. Connection is then established successfully.
6. If the key is incorrect, after a few EAPOLS from the AP, the AP sends a deauthentication packet.
At the end of the connection process, an IP is required. If the STA requests an IP address, the AP will
provide it.
The AP also supports a connection using Wi-Fi protected setup (WPS), as described for the STA role.
5.2
Hidden SSID
Hidden SSID is one method to provide wireless security by hiding the network name. When hidden SSID
is used, the network ID (SSID) is not broadcasted in the AP beacons.
The AP does not reply with a probe response to any device, other than from a probe request with the
specific SSID. This method is not secured, as it is possible to see the SSID of the specific AP from the
probe request, using the sniffer. When scanning the air with a wireless device, the AP with the hidden
SSID will not be found.
A connection scan must be performed for a wireless device to connect, which means transmitting a
unicast probe request with the SSID.
5.3
Security
Wireless encryption and authentication only allow stations with the correct key to connect to the wireless
router. The better the wireless encryption and authentication, the more difficult it is to connect and to
decrypt the data. When assigning a wireless router with a key, and assigning an encryption method, only
an STA with the same key can connect and decrypt the data. This prevents other stations from connecting
and accessing the data. Wireless routers support multiple wireless encryption and authentication methods.
As mentioned in Section 4, there are three main authentication categories: open, personal and enterprise.
The WiLink8.0 AP mode only supports open and personal authentication, where the password (if required)
is configured to the AP, and the AP itself authenticates the peer device using a password.
• WPA (Wi-Fi protected access)
• WPAv2 (Wi-Fi protected access v2)
AP mode also supports the below encryption types:
• Open (no encryption)
• WEP (wireless equivalent protocol)
• TKIP (temporal key integrity protocol)
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•
AES (advanced encryption standard)
AP mode also supports broadcast key rotation, which allows the access point to generate the best
possible random group key and periodically update all key-management capable clients.
5.4
Regulatory Domain
The regulatory domain feature implements the IEEE 802.11d specification.
Each country has a different list of channels in which it is allowed to operate. The AP is responsible for
publishing its beacons using the countries IE. This IE contains all the information regarding the country
being operated in, and the allowed channels and allowed TX power on each channel.
The AP takes this information from the CRDA file, which contains updated information on all allowed
channels and TX power in each country.
The country can be configured in the AP configuration file according to the configured country; the AP
reads the relevant information from the file and publishes it in its beacons.
5.5
AP Scan
The AP can detect other networks in parallel to its own operation. This scan is performed similarly to how
the STA executes a scan. The most common use for an AP scan is when the AP is started on a 40-MHz
channel, and it is required to find a suitable channel on the 5-GHz band.
5.6
Automatic Channel Selection (ACS)
Automatic channel selection (ACS) helps the AP choose the optimal channel for its operation. The
channel is chosen by scanning all channels on the configured band (survey), and filtering out channels
with the highest number of other APs. The mechanism tries to choose the channel with the least number
of APs, also taking into account the regulatory domain rules and other user-defined constraints.
5.6.1
40-MHz Operation
The mechanism uses the number of APs on a channel as a crude measure for the noise on that channel.
If 40-MHz operation is required, the ACS algorithm tries to choose an appropriate secondary channel
(above or below) by going over all of the channel pairs where the primary channel has a minimum number
of APs. If such a pair is found that satisfies all constraints, 40-MHz operation is enabled. Otherwise, the
AP is enabled with 20-MHz operation.
A further optimization has been added to choose the best 40-MHz secondary channel.
When choosing a channel, scan all available secondary channels to choose one with the minimum
amount of APs.
5.6.2
ACS Whitelist and Blacklist Channels
The user can limit the channels used by ACS. The solution supports both a whitelist and a blacklist of
channels. To use the channel blacklist, define a list of channels that will never be chosen when ACS
selects a channel. To use the channel whitelist, define a list of channels that will be chosen only among
those whitelisted.
Both whitelist and blacklist can be used simultaneously.
5.7
Maximum Connected Stations
The soft AP is capable of supporting up to a total of 10 connected STAs. The number of connected STAs
that are supported does not change when running multi-role with two soft APs (both of which support up to
a total of 10 STAs). The soft AP is capable of running equal traffic to all connected STAs. The AP also
maintains a Block-Ack session and aging mechanism for each link.
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Aging
The purpose of the aging mechanism is to deauthenticate an associated STA that is no longer connected,
to save AP resources. Aging mechanisms usually come into play when there is a sudden network loss of
an external connected station, thus, the mechanism frees up allocated space. It has default configurations,
but can also be altered according to need.
5.9
DFS Master
Worldwide, most of the 5-GHz band frequencies are used by radar systems. The same frequency bands
(or subsets) were allocated to unlicensed WLAN devices. A requirement arising from this frequency band
reuse is a method called dynamic frequency selection (DFS). A system that requires DFS must be
capable of avoiding interference with radar systems, according to the regulatory requirements as
described in each DFS standard.
5.9.1
DFS Standards
There are stringent government regulatory requirements that must be followed by Wi-Fi radios when
operating on 5-GHz band frequencies. The regulatory bodies specifying and enforcing these requirements
are:
• Federal Communications Commission (FCC) in North America
• European Telecommunications Standards Institutes (ETSI) in the European Union
• TELEC in Japan
The differences between these DFS standards are primarily in the methods to detect radars operating in a
channel that satisfy regulatory requirements. Each one defines different types of radio parameters such as
pulse width, PRF, modulation, and so forth, and measures the detection success rate.
Most tests regarding the DFS master way of operation, once radar is detected, are similar and focus on
the DFS timing requirements. These tests verify the timing on the parameters as summarized in Table 17.
Table 17. DFS Time Requirements
5.9.2
Parameter
Requirement
Channel Availability Check Time
60s (some have 10 minutes)
Channel Move Time
10s (maximum)
Channel Closing Time
260 ms (maximum)
Non-occupancy period
30 minutes (minimum)
DFS Mechanism
On detection, the AP must notify all connected stations and move to a different frequency. This is done
using channel switch announcement elements (IE#37) in beacon frames, probe response frames, and
channel switch announcement frames, until the intended channel switch time. This capability is known as
dynamic frequency selection or DFS master. DFS master capabilities allow a device to properly utilize the
5-GHz band in an AP role. A Wi-Fi device without DFS master capabilities is permitted to operate as an
AP, but only in a small subset of the 5-GHz band, and in certain countries it is limited to indoor
applications only.
Radar detection must be done in two scenarios:
• Channel Availability Check (CAC): When moving to a new channel, the DFS master must first
withhold any transmission for a period of 1 or 10 minutes (depending on the channel and the regulatory
domain). During this period, it tests the channel for radar signaling presence, and approves or
disapproves the channel.
• In-Service Monitoring: During any activity in a certain channel, the DFS master must identify any
radar signaling in the operating channel. Upon radar detection, the master device instructs all
associated slave devices to stop transmitting on this channel, which they do within the channel move
time, then switch to a different channel.
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After radar detection on a certain channel (during CAC or in-service monitoring), the channel is disabled
for any transmission for a predefined period of time. This period is referred to as the non-occupancy
period (usually 30 minutes). The device keeps a list of disabled channels and enables each channel when
its individual non-occupancy period has expired.
5.9.3
WiLink8.0 DFS Master Capabilities
WiLink8.0 possesses DFS master capabilities in all three regulatory domains: TELEC, FCC, and ETSI.
The active domain is configured according to the Region parameter.
5.10 Access Control
5.10.1
Blacklist
Blacklist refers to a list of MAC addresses from which connection will not be established. Use a blacklist to
deny access to a particular and defined MAC address for WLAN connection.
All MAC addresses that are predefined and placed in that specific folder cannot be accessed, and the
connection will not succeed. This can be used in addition to other security measures.
5.10.2
Whitelist
Whitelist refers to a list of MAC addresses from which connection or acknowledgment is permitted. Use a
whitelist to allow only particular and defined MAC addresses for WLAN connection.
All MAC addresses that are defined and placed in a specific folder can be accessed; connection will not
be established to MAC addresses that are not specified. This can be used in addition to other security
measures.
5.11 Extreme Low Power (ELP)
Unlike a conventional AP, portable devices implementing the software AP feature cannot be assumed to
be tethered to a power supply, and the role of a soft AP is much more demanding than the role of a legacy
STA. Therefore, there is an inherent requirement to reduce the power consumption of the device while
serving the role of soft AP, without any significant performance impact. This requires a standalone power
save mechanism at the soft AP that reduces the power consumption of this device without any explicit
messages to the STAs.
WiLink8 supports low-power consumption AP mode when running idle (no STAs are connected). In this
mode, the AP still has a high discoverability rate.
6
Single Role: P2P
The purpose of P2P is to establish a direct WLAN connection between two devices without involving a
router or AP for its operation. The P2P is known in Android devices as Wi-Fi Direct and can be operated
from the Wi-Fi menu. Usually, the P2P role exists concurrently with the WLAN station role, which causes
Android devices to operate in a WLAN multi-role state.
P2P is a WLAN role that typically has a short lifespan, in contrast to station or AP WLAN roles that exist
from the moment that they have been started until they are explicitly terminated by the user. The P2P role
is mainly used by a Miracast function in Android OS, for example, for mirroring the Android smartphone
screen on other device, such as a smart TV or smart phone that has a WLAN module and supports
Miracast functionality.
P2P may exist in three states: device, client, and GO. P2P functionality, after a connection, is similar to
the WLAN station and AP functionality. However, P2P has supplementary functional behaviors that
distinguish it from a standard station and AP operation, and allows different services to be used. P2P also
has its own power save behavior that allows an additional battery.
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P2P Device
When P2P is enabled, either by enabling the Wi-Fi Direct or the Miracast function, it starts in device state.
This state is used for discovering other P2P devices for further connection by looking for specific services
such as printers or smart TVs. The P2P connection is established while P2P is in a device state. After
connection, the P2P device operates as client or GO depending on a decision taken during the negotiation
process between two P2P devices. The P2P connection process consists of three steps: searching,
negotiation, and group formation
6.1.1
Searching Phase
During a searching phase, the P2P device discovers any device that supports P2P functionality and is
discovered by other P2P devices for further connection. If P2P functionality is used by some specific
application, such as Miracast, only devices that support Miracast capabilities appear in the list of devices
for connection. Such filtering is possible because of a service discovery function in P2P devices.
The P2P device does not have a static operating channel in which it can be detected. Thus, the search
phase consists of two phases: scan and listen. During the scan phase, the P2P devices scan all WLAN
channels on both 2.4 GHz and 5 GHz (if 5 GHz is supported), and wait for responses from devices that
support P2P functionality. During the listen phase, the P2P devices stay on specific channels called social
channels. The P2P device remains in the listen state for a time period that permits detection. P2P
detection during the search phase is statistical and depends on a proper combination of the scan and the
listen phases. When P2P devices are detected, they appear in the P2P devices list.
6.1.2
Negotiation
After detecting P2P devices, establishing a connection is possible. In most cases, the process of
establishing connection consists of two steps: selecting a target device from the list of devices on one P2P
device and allowing this device connection on the second P2P device. The order of initiation does not
have an impact on the role assigned after connection. In some cases, such as mirroring device display
using a Miracast connection, the connection establishment only requires the selection of the target device
on the source device. When the connection process has been invoked, the first phase toward connection
is negotiation about which device operates as GO in this connection by using a value between 0 and 15
that is usually predefined on each device. The device with a higher value operates as GO and the other
device operates as client.
6.1.3
Group Formation
In this phase, the Wi-Fi connection is established. During the negotiation phase, one of the P2P devices is
selected as GO. This GO device starts to transmit beacons on the operational channel and waits for the
connection from the second P2P device. The second P2P device knows the GO operational channel from
the search phase, which allows it to start the connection immediately after the negotiation phase. The
connection process is similar to the standard WPS connection process, which consists of two phases:
creating a security key and a connection using this key, as with WPA2-PSK authentication. When the
connection has been established, the devices operates similarly to a regular Wi-Fi station and AP, while
having additional P2P functionality and the power save capabilities, if needed.
6.2
PSP Client
Once the device has become a client as a result of the negotiation, it acts like a standard Wi-Fi station. An
additional P2P device cannot be connected to it. The P2P client is subject to the GO instructions, such as
starting a power save period. The client device may terminate the P2P connection similarly to the GO
device and return to the device state, while the GO device, if only connected to this client, continues to
operate as GO for the predefined period of typically two minutes.
When the devices wish to re-establish connection, they must complete the whole process staring from
negotiation, WPS provisioning, and WPA2 connection. However, if the P2P devices have a special P2P
“persistent” capability, they can omit the long WPS section and immediately use WPA2-PSK
authentication for the connection.
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6.3
P2P GO
The device that became group owner (GO) during the negotiation phase preceding the connection is a
coordinator of the group. It has the special capabilities of P2P and the standard capabilities of an AP. It
permits connection of additional P2P devices, as well as the connection of legacy Wi-Fi stations, such as
laptops, smartphones, and so forth; if they know the pre-shared security key for connection. Connecting
additional P2P devices to the GO is possible by joining the group, not by negotiation, as this device
already behaves as the GO and does not change its role during this connection.
Because the GO behaves like an AP and must transmit beacons periodically, it is mostly in the active
state, which requires a higher current consumption. However, unlike the limitation of the AP in entering
power save mode, the GO can invoke the power-save mode once or periodically, which leads to power
saving. Usually, devices that use a battery for operation tend to become a client during P2P connection,
for battery-saving considerations.
The lifetime of the GO, and P2P in general, is until one of the peers terminates the connection. When a
peer initiates a disconnect, the second peer also stops operation of the P2P device.
7
Single Role: Mesh
A wireless mesh network is a network topology in which each peer transmits its own data as well as
serves as a relay for other peers in the network. Unlike the standard star topology, where all peers are
connected to the AP and all the data between the peers is transmitted via a single point, in mesh topology
the data between source and destination has a dynamic route. Each peer periodically finds the best route
to each destination in the network. That way, there is no one bottleneck in the network and if a certain
peer is dropped, the network has the ability for self-healing. The mesh network also has the capability to
inter-operate with other networks as described below.
Figure 6. Mesh Network Topology
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Supported Modes
Mesh Point
A Mesh Point (MP) supports a Peer Link Management protocol, which is used to discover neighboring
nodes and keep track of them. Note that neighbor discovery is only limited to nodes which are in range of
an MP.
For communicating with nodes that are further than one hop, the MP uses Hybrid Wireless Mesh Protocol
(HWMP). This path selection protocol is very similar to routing protocols and was optimized to find the
best path to each remote MP in the mesh network.
7.1.2
Mesh Portal/Gate
An IEEE 802.11s mesh network could be used for a variety of purposes. For example, providing internet
access. In this case, at least one node and potentially some of the nodes are connected to the Internet.
Users connected to the mesh network can access the Internet via these gateway nodes called Mesh
Portals (MPP) which are connected to both the mesh network and the Internet.
The Internet connection can be set up by one of two options:
• Setting up Ethernet connection with bridge on one of the Mesh peers.
• Setting up MR use case of Mesh and STA using IP forwarding where the STA role can connect to
remote AP for Internet connection.
7.1.3
Mesh Access Point
A Mesh Access Point (MAP) is a combination of a traditional AP with mesh functionality by using the MR
use case of the AP running concurrently with Mesh. Thus, it can serve as an AP and also be a part of the
mesh network at the same time.
7.2
7.2.1
Hardware and Software Requirements
Hardware requirements
The Mesh Zone Time Synchronization (as the traditional time synchronization) implementation was done
using Sitara™ AM335 host processor. A general-purpose input/output (GPIO) line should be connected
between the AM335 device and the WL8 device:
• On WL8 side: COEX_MWS_FRAME_SYNC (GPIO11 on TI module)
• On AM335 side: GPIO 2_2 (TIMER4) This GPIO line is responsible for the synchronizing between two
different hardware devices.
7.2.2
Software Requirements
The Mesh Time Synchronization feature is fully supported starting from WL8 R8.7 software release.
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7.3
Capabilities
Table 18. Mesh Network Capabilities
Attribute
Value
RF bands
2.4GHz and 5 GHz
Data rates
All HT rates
Radio modes
20 Mhz SISO @2.4
20 Mhz MIMO @2.4
20 Mhz SISO @5
40 Mhz SISO @5
Maximum number of connected peers per single peer in the network
10
Maximum number of nodes in the entire network
32
Maximum number of hops in network
6
Path selection
Optimized HWMP
Self-healing (time to establish an alternate path once a peer have dropped)
500 ms-1500 ms with
active traffic
Security
AuthSAE via
wpa_supplicant
Multicast/broadcast distribution over the network
Supported
DHCP
Supported
IP Routing
Supported
Mesh power save (Light sleep/Deep sleep)
Not Supported
Mesh operating on DFS channel
Not Supported
Mesh zone time synchronization
<20 µsec
8
Multi-Role
8.1
General Overview
The TI WiLink8.0 device supports the multi-role multi-channel (MRMC) operation.
The WiLink8.0 supports the multi-channel operation as time division multiplexing (TDM)-based
concurrency. Each role gets a portion of the air time.
The core of the multi-role operation is the scheduler that decides on each given time what role should be
activated, and protects the role that should be suspended before moving to a new role.
The protection of the role will be defined according to the role type:
• Station: Use power-save mode prior to leaving the channel.
• Access Point: Send a clear-to-send (CTS) frame with the duration of the time out of the channel;
ensure no frames are sent while the receiver is absent.
• P2P: Use one of the above according to the role (P2P-CL similar to STA, P2P-GO similar to AP).
The scheduler prioritizes the activities of each role and resumes or suspends the roles according to the
system perspective of all role activities requests while trying to provide sufficient bandwidth per role to
avoid starvation.
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Limitations
Full concurrency is not supported due to hardware limitations (the need for two PHYs and two radios).
The performance is split between the roles and reduced due to the contact switch and role protection time.
The WiLink8.0 device supports up to two WLAN roles running simultaneously, as seen in Table 19.
Table 19. Supported Multi-Role Combinations
•
•
•
9
Role
STA
AP
P2P CL
STA
AP
P2P GO
X
V
V
V
V
Same Channel
V
Same Channel
Mesh
Same Channel
Same Channel
X
X
P2P CL
V
V
X
X
P2P GO
V
Same Channel
X
X
Dual AP mode must be started or stopped statically.
While operating as DFS master, no scans are allowed. This means MR combinations of DFS master
with STA or with P2P are not supported.
While operating as AP and P2P-GO (same channel) the P2P-GO channel should not be explicitly
given and the channel synchronization is automatically.
Performance
The performance results of the system described in Table 20 are based on real measurements using the
end-to-end system, including a host and the WiLink8.0 processors, and reflect the actual system
performance. These results should be used as a reference results. Note that the performance results are
directly dependent on processor abilities of the host. The results in Table 20 have been achieved using
the single-core Sitara processor with a CPU clock of 700 MHz. A faster and powerful processor will
achieve higher results, and vice versa.
Systems performance results are divided into three main sections: single-role, multi-role, Bluetooth-WLAN
coexistence.
The single-role results refer to the state of a system when only one Wi-Fi role is active, such as station,
AP, P2P client, or P2P GO. The combination of more than one Wi-Fi role is called multi role and the
performance results are described in Section 9.2. When Bluetooth is enabled, the WLAN changes its
behavior to the multi-role behavior, even if only one Wi-Fi role is activated. This combination of one Wi-Fi
role and activated Bluetooth is called Bluetooth-WLAN coexistence. Results for this scenario are
described in Section 9.4.
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9.1
Single-Role
Each Wi-Fi role can operate on either a 2.4-GHz or 5-GHz band using any RF mode, such as SISO20,
SISO40, or MIMO. One exception is SISO40 at 2.0 GHz, which is not supported in AP and GO roles.
Table 20. Single-Role Performance
WLAN TP [Mbps]
2.4 GHz
Role
STA
AP
Client
GO
9.2
5 GHz
Traffic
SISO20
SISO40
MIMO
SISO20
SISO40
TCP TX
48
73
73
48
75
TCP RX
48
85
88
48
88
UDP TX
58
105
105
58
105
UDP RX
58
105
105
58
105
73
TCP TX
46
70
48
TCP RX
48
88
48
85
UDP TX
58
100
58
105
UDP RX
58
105
58
105
TCP TX
48
72
48
72
TCP RX
48
75
48
75
UDP TX
58
105
58
105
UDP RX
58
105
58
105
TCP TX
48
72
48
72
TCP RX
48
75
48
75
UDP TX
58
105
58
105
UDP RX
58
100
58
105
Multi-Role
If more than one Wi-Fi role is activated, the scenario is called multi-role. A second role presence has an
impact on the behavior and performance of the system, the performance of each role is highly dependent
on the activity of the second role. As an example, consider an AP + station combination, with the AP role
as a victim and the station role as the aggressor. When the AP has one station connected and any kind of
traffic is running, its throughput performance depends on what the station role is doing. If the station role is
not connected and is invoking a periodic scan for detecting a suitable AP and router for connection, it will
impact the role performance of the AP at the point when it invokes a scan, but not between scan intervals.
If the station role runs high throughput traffic, it will equally share the bandwidth with the AP role.
However, it also depends on any peer AP and station devices they are connected to.
Additionally, the operation band and RF mode have an influence on system behavior and throughput
performance. Because each role is independent of the other in most role combinations, they can operate
on the same or different channel/band using the same or different RF mode, depending on the peer
device. Consider the AP + station example, the system is configured to MIMO RF mode, such that both
roles can use this role. However, the station role is connected to an AP that supports only SISO20 RF
mode, while a station that is connected to the AP role is able to operate in MIMO RF mode. As a result,
the throughput performance is not shared equally, as the MIMO RF mode has a higher throughput rate,
despite equal time sharing.
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Table 21 represents the typical combinations of WLAN roles and RF modes. The results may vary for
other combinations of WLAN roles and RF modes.
Table 21. Multi-Role Throughput Benchmark
Configuration
Role 1
38
Traffic
Measured [Mbps]
Role 2
Sum
Role
BW
Channel
Role
BW
Channel
Role 1
Role 2
Role 1
Role 2
R1 + R2
SUT
SISO40
36
APUT
SISO40
44
UDP TX
UDP TX
40
47
87
SUT
MIMO
6
APUT
MIMO
11
TCP TX
TCP RX
23
21
45
SUT
SISO40
36
APUT
MIMO
6
UDP TX
TCP RX
36
21
57
SUT
SISO40
36
GOUT
SISO20
6
UDP RX
UDP TX
36
23
59
SUT
MIMO
6
CLUT
SISO40
44
TCP RX
UDP TX
22
41
63
SUT
MIMO
1
CLUT
MIMO
11
TCP RX
UDP TX
22
24
46
SUT
MIMO
6
GOUT
SISO40
44
UDP RX
TCP TX
23
28
51
SUT
MIMO
1
GOUT
SISO20
11
UDP RX
UDP TX
23
24
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9.3
AP and mBSSID (Dual AP) Fairness
9.3.1
AP Fairness: 1-to-10 Stations Throughput Distribution
Table 22. AP Fairness: 1-to-10 Stations Throughput Distribution
Band
Traffic
AP1
RF Mode
No of
STAs
STA 1
2.4G
TCP RX
SISO20
1
57.3
5
STA 2
STA 3
STA 4
STA 5
10.7
10.7
10.5
10.8
10.8
10
5.0
5.0
5.0
5.0
5.0
1
88.4
5
18.1
17.9
18.2
18.0
18.1
10
7.9
7.9
7.9
7.9
7.9
1
48.3
MIMO
TCP TX
SISO20
5G
TCP RX
TCP TX
9.2
9.0
9.0
8.8
3.7
3.7
3.7
3.7
3.7
1
71.6
5
12.3
12.0
12.3
12.3
12.1
5.1
5.1
5.1
5.1
5.1
1
52.1
TP Total
53.5
5.0
5.0
5.0
5.0
5.0
50.0
90.3
7.9
7.8
7.8
7.9
7.9
78.8
45.3
3.7
3.7
3.7
3.7
3.7
37.0
61.0
5.1
5.1
5.0
5.1
5.1
50.9
52.1
5
10.0
10.0
10.1
10.2
10.6
10
4.8
4.8
4.8
4.9
4.8
1
88.9
5
17.7
18.0
18.3
18.5
18.4
10
7.9
7.9
7.9
8.0
7.9
1
48.1
5
8.8
8.7
9.2
9.4
8.9
10
3.7
3.7
3.7
3.7
3.7
1
73.0
5
12.6
12.6
12.6
12.6
12.6
10
5.3
5.3
5.3
5.3
5.3
SISO40
STA 10
71.6
10
SISO20
STA 9
48.3
9.3
SISO40
STA 8
88.4
5
SISO20
STA 7
57.3
10
MIMO
STA 6
50.9
4.8
4.8
4.8
4.8
4.8
48.1
88.9
90.9
8.0
8.0
8.0
7.9
8.0
79.5
48.1
45.0
3.7
3.7
3.7
3.6
3.7
36.9
73.0
63.0
5.3
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5.3
5.3
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mBSSID Fairness: 10 Stations Throughput Distribution
Table 23. AP Fairness: 10 Stations Connected to AP Throughput Distribution
Band
Traffic
AP1
RF Mode
AP1
STAs
AP2
STAs
STA 1
STA 2
STA 3
STA 4
STA 5
STA 6
STA 7
STA 8
STA 9
STA 10
TP Total
2.4G
TCP RX
SISO20
10
0
4.6
4.5
4.6
4.5
4.5
4.6
4.6
4.6
4.5
4.5
45.5
7
3
3.2
3.2
3.2
3.2
3.2
3.2
3.2
7.9
7.2
7.1
44.6
MIMO
TCP TX
SISO20
MIMO
5G
TCP RX
SISO20
SISO40
TCP TX
SISO20
SISO40
40
5
5
4.4
4.5
4.4
4.4
4.4
4.5
4.5
4.4
4.4
4.4
44.3
10
0
6.6
6.6
6.6
6.6
6.5
6.5
6.5
6.5
6.6
6.6
65.6
7
3
4.7
4.6
4.6
4.6
4.6
4.6
4.6
11.5
11.5
11.1
66.4
5
5
6.6
6.6
6.6
6.6
6.6
6.6
6.6
6.6
6.6
6.6
66.0
10
0
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
33.0
7
3
2.3
2.3
2.3
2.3
2.3
2.3
2.3
5.7
5.4
5.2
32.4
5
5
3.2
3.2
3.2
3.2
3.2
3.2
3.2
3.2
3.2
3.2
32.0
10
0
4.5
4.5
4.5
4.3
4.5
4.5
4.5
4.4
4.5
4.5
44.7
7
3
3.0
3.0
3.0
3.0
3.0
3.0
3.0
7.2
7.2
6.9
42.3
5
5
4.2
4.2
4.2
4.2
4.2
4.2
4.2
4.2
4.2
4.2
42.0
10
0
4.5
4.5
4.5
4.6
4.3
4.4
4.3
4.4
4.5
4.3
44.3
7
3
3.1
3.1
3.1
3.1
3.0
3.1
3.1
7.2
7.3
7.2
43.3
5
5
4.3
4.2
4.2
4.4
4.3
4.2
4.3
4.2
4.3
4.2
42.6
10
0
6.9
6.9
7.0
7.0
6.9
6.9
6.9
6.7
7.0
6.9
69.1
7
3
4.7
4.7
4.7
4.7
4.7
4.8
4.5
11.4
11.6
11.7
67.5
5
5
6.6
6.7
6.7
6.8
6.8
6.7
6.8
6.8
6.8
6.8
67.5
10
0
3.3
3.3
3.3
3.2
3.3
3.3
3.2
3.3
3.3
3.3
32.8
7
3
2.3
2.3
2.3
2.3
2.3
2.3
2.3
5.4
5.4
5.3
32.2
5
5
3.2
3.2
3.2
3.2
3.2
3.0
3.2
3.2
3.2
3.1
31.7
10
0
4.6
4.6
4.6
4.6
4.6
4.6
4.6
4.7
4.6
4.6
46.1
7
3
3.2
3.2
3.2
3.2
3.2
3.2
3.2
7.2
7.7
7.5
44.8
5
5
4.5
4.4
4.4
4.3
4.4
4.5
4.5
4.5
4.5
4.5
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9.4
Bluetooth WLAN Coexistence
WLAN and Bluetooth operate at the same RF band and must share it to exist concurrently for their
operation, despite using a different air access mechanism and modulation. As a result, a single radio at a
2.4-GHz band can be used and shared between them. This mechanism permits a full control of the
Bluetooth and WLAN IP air access.
The WLAN-BT coexistence performance results depend on several parameters, which can impact the
overall system behavior and performance. Bluetooth modulation, packet type, or bandwidth can impact
WLAN throughput performance. This is because Bluetooth, during eSCO and A2DP, has a higher priority
over WLAN. The A2DP rate, for example, also impacts WLAN performance.
All results in Table 24 relate to a specific system configuration, and will vary depending on Bluetooth and
WLAN parameters and peer device capabilities.
9.4.1
WLAN Single Role – Bluetooth Performance
Table 24. WLAN Single Role – Bluetooth Coexistence
WLAN TP [Mbps]
2.4GHz
DUT Role
Bluetooth/BLE
Traffic
Settings
SUT
Hands Free
2EV3 1 Retry
A2DP Sink
350 kbps
A2DP Source
350 kbps
FTP CLT TX
APUT
WLAN Traffic
SISO20
MIMO20
SISO20
TCP TX
22
26
50
SISO40
93
TCP RX
21
24
60
117
TCP TX
20
32
51
87
TCP RX
22
41
60
102
TCP TX
35
56
50
93
TCP RX
39
70
60
115
TCP TX
25
42
52
88
TCP RX
26
50
60
91
TCP TX
46
72
48
79
109
BLE Advertise
Every 110 mSec
TCP RX
57
76
59
BLE Discovery
Interval : 60 mSec
TCP TX
49
34
48
78
Window Size : 20 mSec
TCP RX
59
45
59
109
HF
2EV3 1 Retry
TCP TX
16
18
48
79
TCP RX
20
21
58
108
A2DP Sink
350 kbps
TCP TX
24
36
51
77
TCP RX
26
35
59
98
A2DP Source
350 kbps
TCP TX
27
40
50
80
TCP RX
31
42
61
109
TCP TX
25
37
50
74
TCP RX
29
39
58
87
TCP TX
48
83
49
93
TCP RX
56
105
60
118
Interval: 60 mSec
TCP TX
29
48
50
93
Window Size: 20 mSec
TCP RX
34
62
60
118
2EV3 1 Retry
TCP TX
17
21
50
80
TCP RX
23
20
60
111
FTP CLT TX
1 Mbps
BLE Advertise
Every 110 mSec
BLE Discovery
CLUT
1 Mbps
5GHz
HF
A2DP Sink
350kbps
A2DP Source
350kbps
FTP CLT TX
1Mbps
TCP TX
19
26
51
77
TCP RX
22
27
61
100
TCP TX
34
48
50
80
TCP RX
40
49
61
110
TCP TX
24
35
51
76
TCP RX
28
34
57
90
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Table 24. WLAN Single Role – Bluetooth Coexistence (continued)
WLAN TP [Mbps]
2.4GHz
DUT Role
Bluetooth/BLE
Traffic
Settings
GOUT
HF
2EV3 1 Retry
A2DP Sink
350kbps
A2DP Source
350kbps
FTP CLT TX
42
1Mbps
5GHz
WLAN Traffic
SISO20
MIMO20
SISO20
TCP TX
17
20
50
79
TCP RX
22
21
60
111
TCP TX
24
34
51
76
TCP RX
26
30
60
101
TCP TX
27
40
50
79
TCP RX
31
38
61
112
TCP TX
25
39
51
75
TCP RX
29
35
61
88
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Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Original (July 2015) to A Revision ........................................................................................................... Page
•
•
•
•
•
•
•
•
•
•
•
Changed title of this document. ......................................................................................................... 5
Updated Table 2. .......................................................................................................................... 5
Updated Table 3. .......................................................................................................................... 7
Updated Section 3.6. .................................................................................................................... 14
Section 3.11 was updated and moved to its current location in the document. ................................................. 17
Updated Section 4.5.1. .................................................................................................................. 22
Added new Section 7. ................................................................................................................... 33
Updated Section 7.1.1. .................................................................................................................. 34
Updated Table 18. ....................................................................................................................... 35
Updated Section 8.2. .................................................................................................................... 36
Updated Table 19. ....................................................................................................................... 36
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