WiLink 8.0™ Software Specification User's Guide Literature Number: SWRU423 July 2015 Contents 1 2 3 4 2 Introducion .......................................................................................................................... 5 1.1 Scope ...................................................................................................................... 5 1.2 Acronyms Table .......................................................................................................... 5 1.3 WiLink 8.0 Specification ................................................................................................. 7 General Features.................................................................................................................. 8 2.1 Supported Rates ......................................................................................................... 8 2.2 Supported Modes 2.3 High-Throughput (HT) Features ...................................................................................... 10 2.4 Quality of Service (QoS) ............................................................................................... 13 ........................................................................................................ 9 ....................................................................................................... 14 ................................................................................................. 14 2.7 WoW (Wake on WLAN) ................................................................................................ 15 2.8 Set TX Power ........................................................................................................... 15 2.9 5-GHz Antenna Diversity .............................................................................................. 15 2.10 Wi-Fi – BT/BLE Coexistence .......................................................................................... 16 2.11 Wi-Fi – ZigBee Coexistence........................................................................................... 17 Single Role: Station ............................................................................................................ 17 3.1 Scanning ................................................................................................................. 17 3.2 Connection............................................................................................................... 19 3.3 Disconnection ........................................................................................................... 21 3.4 DHCP Client ............................................................................................................. 22 3.5 Security .................................................................................................................. 22 3.6 Filtering................................................................................................................... 22 3.7 Auto ARP ................................................................................................................ 23 3.8 Preferred Networks (Profiles) ......................................................................................... 23 3.9 Power-Save Mode ...................................................................................................... 24 3.10 Power-Save Delivery Protocols ....................................................................................... 25 3.11 Keep-Alive Mechanism................................................................................................. 25 3.12 Smart Config ............................................................................................................ 25 3.13 Regulatory Domain ..................................................................................................... 26 3.14 DFS Slave (Channel Switch) .......................................................................................... 26 3.15 Roaming ................................................................................................................. 26 3.16 Accurate Synchronization over Wi-Fi ................................................................................ 28 Single Role: AP .................................................................................................................. 28 4.1 Connection............................................................................................................... 28 4.2 Hidden SSID............................................................................................................. 28 4.3 Security .................................................................................................................. 28 4.4 Regulatory Domain ..................................................................................................... 29 4.5 AP Scan .................................................................................................................. 29 4.6 Automatic Channel Selection (ACS) ................................................................................. 29 4.7 Maximum Connected Stations ........................................................................................ 30 2.5 Protection Types 2.6 Suspend and Resume Table of Contents SWRU423 – July 2015 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated www.ti.com 5 6 7 4.8 Aging ..................................................................................................................... 30 4.9 DFS Master .............................................................................................................. 30 4.10 Access Control .......................................................................................................... 31 4.11 Extreme Low Power (ELP) ............................................................................................ 31 Single Role: P2P ................................................................................................................ 31 5.1 P2P Device .............................................................................................................. 32 5.2 PSP Client ............................................................................................................... 33 5.3 P2P GO .................................................................................................................. 33 Multi-Role .......................................................................................................................... 33 6.1 General Overview....................................................................................................... 33 6.2 Limitations ............................................................................................................... 33 Performance ...................................................................................................................... 34 7.1 Single-Role .............................................................................................................. 34 7.2 Multi-Role ................................................................................................................ 35 7.3 AP and mBSSID (Dual AP) Fairness ................................................................................ 36 7.4 BT-WLAN Coexistence ................................................................................................ 38 SWRU423 – July 2015 Submit Documentation Feedback Contents Copyright © 2015, Texas Instruments Incorporated 3 www.ti.com List of Figures 1 A-MPDU Aggregation ...................................................................................................... 11 2 Legacy, Mixed and Greenfield Preamble Structures .................................................................. 12 3 5-GHz Antenna Diversity .................................................................................................. 16 4 Wi-Fi – BT/BLE Coexistence – Shared Antenna ....................................................................... 16 5 Wi-Fi – ZigBee Coexistence – GPIOs Interface ........................................................................ 17 List of Tables 1 WiLink 8.0 Family ............................................................................................................ 5 2 Acronyms Table .............................................................................................................. 5 3 WiLink 8.0 Specification..................................................................................................... 7 4 RF Modes ..................................................................................................................... 8 5 Multi-Role Combinations .................................................................................................... 8 6 WiLink 8.0 802.11b Supported PHY Rates............................................................................... 8 7 WiLink 8.0 802.11a/g Supported PHY Rates 8 WiLink 8.0 Supported Modes 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 4 ............................................................................ 9 .............................................................................................. 9 WiLink 8.0 802.11n Supported PHY Rates ............................................................................. 10 QoS Access Categories ................................................................................................... 13 QoS TIDs .................................................................................................................... 13 Scan Types ................................................................................................................. 17 One-Shot Scan ............................................................................................................. 18 OS Scan ..................................................................................................................... 18 Connection Scan ........................................................................................................... 19 Beacon Filtering Parameters ............................................................................................. 23 Estimated Roaming Timing ............................................................................................... 27 DFS Time Requirements .................................................................................................. 30 Supported Multi-Role Combinations ..................................................................................... 34 Single-Role Performance.................................................................................................. 34 Multi-Role Throughput Benchmark....................................................................................... 35 AP Fairness: 1-to-10 Stations Throughput Distribution ............................................................... 36 AP Fairness: 10 Stations Connected to AP Throughput Distribution ................................................ 37 WLAN Single Role – BT Coexistence ................................................................................... 38 List of Figures SWRU423 – July 2015 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated User's Guide SWRU423 – July 2015 WiLink 8.0™ Software Specification 1 Introducion 1.1 Scope This document provides detailed information about various WiLink 8.0 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 8.0 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/. This document covers the entire WiLink 8.0 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 8.0 Family 1.2 WiLink8.0 Description WL1807MOD Industrial dual band combo, 2x2 MIMO Wi-Fi module WL1837MOD Industrial dual band, 2x2 MIMO Wi-Fi, Bluetooth® and Bluetooth low energy module WL1835MOD Single band combo 2x2 MIMO Wi-Fi, Bluetooth and Bluetooth low energy module WL1831MOD Single band combo Wi-Fi, BT and BLE 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 Wi-Fi Access Point Access Point Under Test Address Resolution Protocol Block Acknowledgment Basic Service Set BR Basic Rate (for BT) BT Bluetooth CDMA Code Division Multiple Access COEX Co-Existence Bluetooth is a registered trademark of Bluetooth SIG, Inc. Android is a trademark of Google, Inc. Linux is a registered trademark of Linus Torvalds. All other trademarks are the property of their respective owners. SWRU423 – July 2015 Submit Documentation Feedback WiLink 8.0™ Software Specification Copyright © 2015, Texas Instruments Incorporated 5 Introducion www.ti.com Table 2. Acronyms Table (continued) Acronyms 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 BT) ELP Extreme Low Power ESS Extended Service Set GO P2P Group Owner GUI Graphical User Interface LAN Local Area Network MIMO MR Multiple Input, Multiple Output 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 WLAN U-APSD 6 Description CTS Wireless Local Area Network Unscheduled Automatic Power-Save Delivery UPSD Unscheduled Power Save Delivery WMM Wireless Multi-Media WPS Wi-Fi Protected Setup WiLink 8.0™ Software Specification SWRU423 – July 2015 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Introducion www.ti.com 1.3 WiLink 8.0 Specification Table 3. WiLink 8.0 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–BT/BLE 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 Device Name Supported wpa_supplicant.conf Client Supported wpa_supplicant.conf GO Supported hostapd.conf STA AP P2P SWRU423 – July 2015 Submit Documentation Feedback WiLink 8.0™ Software Specification Copyright © 2015, Texas Instruments Incorporated 7 General Features www.ti.com Table 3. WiLink 8.0 Specification (continued) Role Feature Description Configuration MR Multi-Role Combinations See Table 5 Not Configurable 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 2 General Features 2.1 Supported Rates P2P GO WiLink 8.0 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. 2.1.1 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 8.0 802.11b Supported PHY Rates 8 Modulation Bit Rate Defined in DBPSK 1 Mbps 802.11 DQPSK 2 Mbps CCK 5.5 Mbps CCK 11 Mbps WiLink 8.0™ Software Specification 802.11b SWRU423 – July 2015 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated General Features www.ti.com 2.1.2 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 8.0 802.11a/g Supported PHY Rates 2.2 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 Supported Modes WiLink 8.0 supports the operation modes shown in Table 8 per WLAN role. Table 8. WiLink 8.0 Supported Modes Band Role STA 2.4 GHz 5 GHz 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 SWRU423 – July 2015 Submit Documentation Feedback WiLink 8.0™ Software Specification Copyright © 2015, Texas Instruments Incorporated 9 General Features 2.3 www.ti.com 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. 2.3.1 11n Rates WiLink 8.0 supports the PHY rates for both TX and RX (in Mbps) shown in Table 9. Table 9. WiLink 8.0 802.11n 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. 2.3.2 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. 10 WiLink 8.0™ Software Specification SWRU423 – July 2015 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated General Features www.ti.com 2.3.3 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. 2.3.4 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. 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. SWRU423 – July 2015 Submit Documentation Feedback WiLink 8.0™ Software Specification Copyright © 2015, Texas Instruments Incorporated 11 General Features 2.3.5 www.ti.com 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. 2.3.6 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. 2.3.7 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 12 WiLink 8.0™ Software Specification SWRU423 – July 2015 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated General Features www.ti.com 2.4 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. Table 10 shows the default EDCA parameters. Table 10. 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 11). Table 11. 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. SWRU423 – July 2015 Submit Documentation Feedback WiLink 8.0™ Software Specification Copyright © 2015, Texas Instruments Incorporated 13 General Features 2.5 2.5.1 www.ti.com 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 2.5.2. For more information, see the 802.11n specification located at https://en.wikipedia.org/wiki/802.11. 2.5.2 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 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. 2.6 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. 14 WiLink 8.0™ Software Specification SWRU423 – July 2015 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated General Features www.ti.com 2.7 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 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 2.8 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. 2.9 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. 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. 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) SWRU423 – July 2015 Submit Documentation Feedback WiLink 8.0™ Software Specification Copyright © 2015, Texas Instruments Incorporated 15 General Features www.ti.com SoC 5GHz antenna port 1 WLAN 5GHz Tx WLAN 5GHz Rx 5GHz antenna port 2 DPDT switch control Figure 3. 5-GHz Antenna Diversity 2.10 Wi-Fi – BT/BLE Coexistence Both WLAN and BT 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 BT/BLE 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 BT. 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 BT 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 – BT/BLE Coexistence – Shared Antenna 16 WiLink 8.0™ Software Specification SWRU423 – July 2015 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated General Features www.ti.com 2.11 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 3 Single Role: Station 3.1 Scanning 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 12 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 12 describe the shortest, typical, and longest scan process. Table 12. 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 SWRU423 – July 2015 Submit Documentation Feedback 5000 WiLink 8.0™ Software Specification Copyright © 2015, Texas Instruments Incorporated 17 Single Role: Station 3.1.1 www.ti.com 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 13. 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 14. 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) 3.1.2 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. 18 WiLink 8.0™ Software Specification SWRU423 – July 2015 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Single Role: Station www.ti.com 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 15. 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) 3.1.3 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 3.15. 3.2 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. 3.2.1 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 3.2.2). SWRU423 – July 2015 Submit Documentation Feedback WiLink 8.0™ Software Specification Copyright © 2015, Texas Instruments Incorporated 19 Single Role: Station www.ti.com 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. 3.2.1.1 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 3.2.1.2 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. 20 WiLink 8.0™ Software Specification SWRU423 – July 2015 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Single Role: Station www.ti.com 3.2.1.3 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. 3.2.2 Automatic (Via Profiles) Section 3.8 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. 3.2.3 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. 3.2.3.1 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. 3.2.3.2 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. 3.3 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 SWRU423 – July 2015 Submit Documentation Feedback WiLink 8.0™ Software Specification Copyright © 2015, Texas Instruments Incorporated 21 Single Role: Station www.ti.com After the disconnection process, if the STA has any saved profiles, it starts to scan. If any candidate is discovered, it connects. 3.4 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. 3.5 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). 3.5.1 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 3.5.2 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) 3.5.3 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. 3.6 3.6.1 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. 22 WiLink 8.0™ Software Specification SWRU423 – July 2015 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Single Role: Station www.ti.com 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 16. Table 16. Beacon Filtering Parameters 3.6.2 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. 3.7 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. 3.8 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. SWRU423 – July 2015 Submit Documentation Feedback WiLink 8.0™ Software Specification Copyright © 2015, Texas Instruments Incorporated 23 Single Role: Station www.ti.com 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. 3.8.1 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. 3.9 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. 3.9.1 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. 3.9.2 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. 3.9.3 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. 24 WiLink 8.0™ Software Specification SWRU423 – July 2015 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Single Role: Station www.ti.com 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. 3.10 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. 3.10.1 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. 3.10.2 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. 3.11 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. 3.12 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. SWRU423 – July 2015 Submit Documentation Feedback WiLink 8.0™ Software Specification Copyright © 2015, Texas Instruments Incorporated 25 Single Role: Station www.ti.com 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. 3.13 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. 3.14 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. 3.15 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. 3.15.1 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 3.15.1.1 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. 26 WiLink 8.0™ Software Specification SWRU423 – July 2015 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Single Role: Station www.ti.com 3.15.1.2 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. 3.15.1.3 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. 3.15.1.4 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 17 shows an example of roaming process time in a clean environment. Table 17. Estimated Roaming Timing 3.15.2 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. 3.15.2.1 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. 3.15.2.2 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. SWRU423 – July 2015 Submit Documentation Feedback WiLink 8.0™ Software Specification Copyright © 2015, Texas Instruments Incorporated 27 Single Role: Station www.ti.com 3.16 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. 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 Single Role: AP 4.1 Connection 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. 4.2 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. 4.3 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. 28 WiLink 8.0™ Software Specification SWRU423 – July 2015 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Single Role: AP www.ti.com As mentioned in Section 3, 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) • 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. 4.4 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. 4.5 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. 4.6 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. 4.6.1 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. 4.6.2 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. SWRU423 – July 2015 Submit Documentation Feedback WiLink 8.0™ Software Specification Copyright © 2015, Texas Instruments Incorporated 29 Single Role: AP www.ti.com Both whitelist and blacklist can be used simultaneously. 4.7 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. 4.8 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. 4.9 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. 4.9.1 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 18. Table 18. DFS Time Requirements 4.9.2 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. 30 WiLink 8.0™ Software Specification SWRU423 – July 2015 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Single Role: AP www.ti.com 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. 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. 4.9.3 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. 4.10 Access Control 4.10.1 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. 4.10.2 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. 4.11 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. 5 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. SWRU423 – July 2015 Submit Documentation Feedback WiLink 8.0™ Software Specification Copyright © 2015, Texas Instruments Incorporated 31 Single Role: P2P www.ti.com 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. 5.1 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 5.1.1 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. 5.1.2 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. 5.1.3 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. 32 WiLink 8.0™ Software Specification SWRU423 – July 2015 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Single Role: P2P www.ti.com 5.2 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. 5.3 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. 6 Multi-Role 6.1 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. 6.2 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. SWRU423 – July 2015 Submit Documentation Feedback WiLink 8.0™ Software Specification Copyright © 2015, Texas Instruments Incorporated 33 Performance www.ti.com Table 19. Supported Multi-Role Combinations • • 7 Role STA AP P2P CL STA X V V P2P GO V AP V Same Channel V Same Channel 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. 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, BT-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 7.2. When BT 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 BT is called BT-WLAN coexistence. Results for this scenario are described in Section 7.4. 7.1 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 34 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 TCP TX 46 70 48 73 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 WiLink 8.0™ Software Specification SWRU423 – July 2015 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Performance www.ti.com 7.2 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. 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 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 47 SWRU423 – July 2015 Submit Documentation Feedback WiLink 8.0™ Software Specification Copyright © 2015, Texas Instruments Incorporated 35 Performance 7.3 www.ti.com AP and mBSSID (Dual AP) Fairness 7.3.1 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 MIMO TCP TX SISO20 MIMO 5G TCP RX SISO20 SISO40 TCP TX SISO20 SISO40 36 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 STA 6 STA 7 STA 8 STA 9 STA 10 TP Total 57.3 53.5 5.0 5.0 5.0 5.0 5.0 50.0 88.4 90.3 7.9 7.8 7.8 7.9 7.9 78.8 48.3 5 9.3 9.2 9.0 9.0 8.8 10 3.7 3.7 3.7 3.7 3.7 1 71.6 45.3 3.7 3.7 3.7 3.7 3.7 37.0 71.6 5 12.3 12.0 12.3 12.3 12.1 10 5.1 5.1 5.1 5.1 5.1 1 52.1 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 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 WiLink 8.0™ Software Specification 63.0 5.3 5.3 5.3 5.3 5.3 53.0 SWRU423 – July 2015 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Performance www.ti.com 7.3.2 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 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 44.5 SWRU423 – July 2015 Submit Documentation Feedback WiLink 8.0™ Software Specification Copyright © 2015, Texas Instruments Incorporated 37 Performance 7.4 www.ti.com BT-WLAN Coexistence WLAN and BT 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 BT and WLAN IP air access. The WLAN-BT coexistence performance results depend on several parameters, which can impact the overall system behavior and performance. BT modulation, packet type, or bandwidth can impact WLAN throughput performance. This is because BT, 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 BT and WLAN parameters and peer device capabilities. 7.4.1 WLAN Single Role – BT Performance Table 24. WLAN Single Role – BT Coexistence WLAN TP [Mbps] 2.4GHz DUT Role BT/BLE Traffic Settings SUT Hands Free 2EV3 1 Retry A2DP Sink 350 kbps A2DP Source 350 kbps FTP CLT TX APUT 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 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 98 350 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 HF A2DP Sink 38 WLAN Traffic BLE Advertise A2DP Source CLUT 1 Mbps 5GHz 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 WiLink 8.0™ Software Specification SWRU423 – July 2015 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Performance www.ti.com Table 24. WLAN Single Role – BT Coexistence (continued) WLAN TP [Mbps] 2.4GHz DUT Role BT/BLE Traffic Settings GOUT HF 2EV3 1 Retry A2DP Sink 350kbps A2DP Source 350kbps FTP CLT TX 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 SWRU423 – July 2015 Submit Documentation Feedback SISO40 WiLink 8.0™ Software Specification Copyright © 2015, Texas Instruments Incorporated 39 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. 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