MAC, RLC, PDCP, RRC

Transport Requirements for a 5G
Broadband Use Case
Vishwanath Ramamurthi
Thomas Tan
Shankar Venkatraman
Verizon
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Policies and Procedures
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The contributor acknowledges and accepts that this contribution is subject to
•
The IEEE Standards copyright policy as stated in the IEEE-SA Standards Board Bylaws,
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Transport Requirements for a 5G Broadband Use Case
8/12/2016
2
IEEE WG Project # 1914.1
Next Generation Fronthaul Interface
Jinri Huang, Email: huangjinri@chinamobile.com
Transport Requirements for a 5G Broadband Use Case
Date: 2016-08-12
Author(s):
Name
Affiliation
Phone
[optional]
Email [optional]
Vishwanath Ramamurthi
Verizon
vishwa@VerizonWireless.com
Thomas Tan
Verizon
Thomas.Tan@VerizonWireless.com
Shankar Venkatraman
Verizon
Shankar.Venkatraman@VerizonWireless.com
Transport Requirements for a 5G Broadband Use Case
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Verizon 5GTF Specifications Summary
Goal of Verizon 5GTF (5G Technical Forum)
Develop a common and extendable platform for Verizon’s
28/39 GHz fixed wireless access deployment
Scope
The specifications facilitate early 5G deployments for
Verizon’s fixed wireless use case and requirements.
Promote interoperability among network and CPE/chipset
vendors.
Format
Developed jointly by Verizon and ecosystem partners (Nokia,
Ericsson, Samsung, Qualcomm, Intel, Cisco, and LG)
Website: http://5gtf.org
Transport Requirements for a 5G Broadband Use Case
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5GTF: General Protocol Architecture
Radio Interface is composed of Layers 1, 2 and 3, and covers the interface
between user equipment and the network
V5G.200 series describe the Layer 1 (Physical Layer)
V5G.300 series describe Layers 2 and 3 (MAC, RLC, PDCP, RRC)
LAYER 3
LAYER 2
LAYER 1
Control/ Measurements
V5G.401 describes the Stage 2 level overall network reference architecture, and
Stage 3 level NAS specifications
Transport Requirements for a 5G Broadband Use Case
RRC
Logical Channels
MAC
Transport Channels
PHY
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5GTF: Key Air Interface Features
New RAT Numerology
Short subframe duration with reduced latency
Utilize large bandwidth @ 28/39 GHz
Flexibility for different scenarios & different frequency bands
Flexible Frame Structure
Dynamic UL/DL allocations to support various traffic conditions
Flexible framework additional future use cases and scenarios
Advanced Beamforming
Improve coverage, throughput and densification of cells
Ensure a robust 5G system
Multi-site beamforming/switching
Fast initial acquisition and beamforming training
Transport Requirements for a 5G Broadband Use Case
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Physical Layer (L1) Outline
Technology Components
Details
Spectrum
28 GHz
Bandwidth
Component carrier BW = 100 MHz
Duplex
Dynamic TDD
Waveform
OFDM (DL/UL)
Subcarrier Spacing
75 KHz (5 x LTE)
MIMO
Up to 2 layers, MU-MIMO
Beamforming
Hybrid (Digital + Analog)
Modulation
Up to 64 QAM (DL/UL)
Channel Coding
LDPC
TTI length
0.2 ms (LTE / 5)
# of subcarriers
1200 per component carrier
Structure
Self contained frame structure
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Numerology Details
Sampling rate
153.6 MHz
FFT Size (N)
2048
Subcarrier spacing
(Δf)
75kHz
Basic Sample Time
Unit (Ts)
1/(75000x2048) sec
Subframe duration
0.2 ms (30720 samples)
OFDM symbols per
subframe
14
Symbol Duration
13.3 microsec (2048 samples)
CP length
160 samples (1042 ns, symbol 0/7)
144 samples (940 ns, other symbols)
Occupied Subcarriers
1200
Radio Frame Duration
10 ms (50 subframes)
UL
N symb
OFDM symbols
UL RB
k  N RB
N sc  1
Resource block
UL
N symb
 N scRB resource elements
N scRB subcarriers
100 MHz
UL
 N scRB subcarriers
N RB
Component
Carrier BW
One uplink slot Tslot
Resource element (k , l )
k 0
l0
Transport Requirements for a 5G Broadband Use Case
l
UL
N symb
1
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Spectrum for 5G
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RAN Architecture Considerations
1. Flexible RAN Split Options (Central Unit CU and Remote Unit RU)
•
Enables Centralization gains and cost efficient design
•
Different RAN split options might be optimal for different deployment scenarios
•
Allow different degrees of centralization for user and control plane
2. 5G BW and Latency Requirements
•
5G Radio with data rates of order of several Gbps per sector challenges FrontHaul (FH)
using legacy CPRI type interface
•
CPRI (PHY – RF split) Limitations
•
•
20 MHz 2 x 2 LTE sector requires ~ 2.5 Gbps FH BW
•
Max ~ 25 Gbps, Stringent delay requirements
•
Does not scale with BW and # of antenna elements
•
Closed ecosystem
Need to study alternate RAN architectures and split options
3. Interaction between RAN protocol and architecture designs
•
Protocol design should allow for architecture flexibility
•
Impacts and impacted by several aspects including HARQ design, Timing Advance,
Scheduling Latency, CSI feedback, Segmentation/Re-assembly etc
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RAN Split Benefits/Drivers
Resource Pooling
Cooperative
Processing
Increased
Virtualization
Easier Upgrades and
Self Healing
• Pool resources across multiple eNBs
• L2/L3 resources dimensioned on aggregate traffic / connections
• L1 resources dimensioned on RF BW & antennas
• Centralized Scheduling and Interference management
• UL/DL CoMP schemes
•
•
Enable SDN/NFV with general purpose compute hardware
Efficient scalable RAN
• Reduce hardware/software upgrade & provisioning time
• Grow user capacity / connections / features as needed
• Virtual machine switchover on failure
Edge Applications
• Faster deployment of new services and features (M2M handling,
Edge Analytics (User/Application), Video Optimization etc)
• Decouple applications from dedicated physical elements
Energy Savings
• Efficient pooling of compute to lower overall energy consumption
• Power down resources during lighter traffic to save energy
Reduce CAPEX/OPEX
• Large scale centralized processing on general purpose hardware
• Cost effective Fronthaul transport - some PHY functions at edge
• Easier hardware, software and vendor switching
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RAN Split Options and Tradeoffs
Low
RLC
ARQ, Segmentation, Re-Assembly
UE Scheduling, QoS
MAC
Channel Map, MCS, RB Allocation, HARQ
L
1
PDCP – RLC (DC)
PHY
RLC – MAC
MAC Hi – MAC Lo
MAC – PHY
Bit Processing (FEC etc)
PHY Bit – PHY Sym
Mod, Layer Map, Precode
PHY Pre – PHY IFFT
Res Map, IFFT
PHY – RF (CPRI)
RF
CPRI to RF modulation
HARQ
(X TTI)
High
Transport Requirements for a 5G Broadband Use Case
Stringent
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Centralization Gain
PDCP
Ciphering, Integrity Protection, Compression
L
2
Low
IP
Fronthaul Delay Requirement
RRC
Ctrl Signaling, NAS
Fronthaul Bandwidth Requirement
L
3
Relaxed
High
12
RAN Split Options: Comparison
Front Haul
Requirement
Split Option
Performance/Operations
BW
Latency
Central
Sched. &
Int. Mgmt.
Cent.
Gains
Interface
Complexity
FH Cost
Low
More Relaxed
No
Low
Moderate
Cheaper
Low
More Relaxed
No
Better
Moderate
Cheaper
Lower
Relaxed
Yes
High
High
Cheaper
Lower
Strict
Yes
High
High
Cheaper
Lower
Strict
Yes
High
High
Cheaper
High
Strict
Yes
Very High
Low
+ IFFT
Expensive
Always High
Strict
Yes
Very High
High
PDCP – RLC
Op 1
CU: RRC, PDCP
RU: RLC, MAC, PHY, RF
RLC – MAC
Op 2
CU: RRC, PDCP, RLC
RU: MAC, PHY, RF
MAC Hi – MAC Lo
Mid
Op 3
CU: RRC, PDCP, RLC, MAC Hi
RU: MAC Lo, PHY, RF
MAC – PHY
Op 4
CU: RRC, PDCP, RLC, MAC
RU: PHY, RF
PHY Bit – PHY Sym
Op 5
CU: RRC, PDCP, RLC, MAC, PHYx
RU: PHYy, RF
Low
PHY Pre – PHY IFFT
Op 6
CU: RRC, PDCP, RLC, MAC, PHYx
RU: PHYy, RF
PHY – RF
Op 7
CU: RRC, PDCP, RLC, MAC, PHY
RU: RF
Transport Requirements for a 5G Broadband Use Case
Low
Off Shelf H/W
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Very
Expensive
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5G Fronthaul BW Estimates
Parameter
Units
Bandwidth
MHz
OFDM Sym per sub frame
#
Subframe duration
ms
FFT Size
#
# of subcarriers
#
# of BS antenna elements/sector
#
# of streams (layers)
#
Bits/Sample
bit per sample
Mod Order
bits per symbol
Max TB Size
bits
# of carrier aggregation
#
Overhead of front haul protocol
%
Split Type
PDCP - RLC
MAC – PHY / MAC Hi-MAC Low
PHY Bit - PHY Sym
PHY Pre - PHY IFFT
PHY - RF
LTE Baseline (UL)
5G Case 1
5G Case 2
5G Case 3
20
14
1
2048
1200
8
4
8
8
75375
2
25%
100
14
0.2
2048
1200
8
4
8
6
66392
4
25%
100
14
0.2
2048
1200
8
4
8
6
66392
8
25%
100
14
0.2
2048
1200
16
8
8
8
66392
8
25%
Units
LTE Baseline (UL)
Gbps
Gbps
Gbps
Gbps
Gbps
0.7
0.8
1.3
5.4
9.2
Transport Requirements for a 5G Broadband Use Case
Fronthaul BW
5G Case 1
5G Case 2
6.0
6.6
10.1
53.8
91.8
12.0
13.3
20.2
107.5
183.5
5G Case 3
23.9
26.6
53.8
215.0
367.0
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FH BW Comparison – RAN Split Options
FrontHaul Bandwidth for various options
400
LTE Baseline
5G Case 1
5G Case 2
5G Case 3
Fronthaul BW (Gbps)
350
300
250
200
150
100
50
0
PDCP - RLC
Transport Requirements for a 5G Broadband Use Case
MAC - PHY
PHY Bit - PHY PHY Pre - PHY
Sym
IFFT
PHY - RF
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4G/5G Fronthaul/Backhaul Architecture Options
Dark Fiber/NGFI
5G RRH
5G BBU Pool
Eth. Switch
N * 10GE
CO
CPRI/RoE
5G RRH
NGFI/RoE
5G RU
5G RU
Eth. Switch
NGFI/RoE
5G RU
Vendor1
5G RU Pool
Eth. Switch
5G RU
Vendor2
5G RU
Vendor3
5G RRH
4G RRH
Local
Data
Center
10 GE
M * 10GE
Optical Ring
CO
Local
Data
Center
4G/5G vBBU
Eth. Switch
5G RRH
4G RRH
Local
Data
Center
NGFI/RoE
4G/5G vBBU
Eth. Switch
CO
1GE to 10GE
CPRI/RoE/NGFI
Transport Requirements for a 5G Broadband Use Case
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Trajectory of Change
Transport Network Requirements Evolution
LTE-A
1Gbps
Eth
2009
2012
10000
2006
100
2002
50
8T1
4T1
12
10
1000
50 Mbps
Eth
100
NGFI/RoE?
Eth
? ?
100 Mbps
Eth
5000
1000
CRAN
10Gbps
CPRI
2016
2017
100000
10000
CRAN
5Gbps
CPRI
NGFI/RoE?
CRAN
10X Gbps Eth
CPRI/RoE
50000
100000
6
Front/Backhaul BW Range (Mbps)
1000000
2017
2019
1
3G
2014
4G
2020
5G
Generation - Timeline
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Future Mobile/Access Network
DC SDN
RAN SDN
DC SDN
OTN
National
Data Center
Control Plane
Functions
NOC
Provisioning
Billing
Orchestration
Service
Assurance
4G
5G
Unified Front-haul,
Mid-haul & Backhaul
Over Ethernet
Internet of Everything
WAN SDN
In-Building
In-Building
MultiGigE Internet
Local
Data Center
User Plane
Functions
vBBU/MME
Security
Caching
Routing
Edge Computing
Internet
Internet
Femto
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New Opportunities/Challenges
•
Unified front-haul, mid-haul and backhaul
•
•
•
•
Optimized RAN Split: Desired Features
•
•
•
•
•
•
Move away from CPRI (technical and ecosystem limitations)
Ethernet could be the unifier
Enable fronthaul resilience
Reduced FH Bandwidth
Low complexity interface
Low cost off-the shelf Remote Units
Centralization gains
At least one high and one lower layer split
Challenges
•
•
•
Tradeoffs: Timeline-Flexibility, Cent. Gains–Bandwidth
Standardized Interfaces: Vendor Interoperability
Ecosystem: Partners needed for equipment, compute, networking, and end-toend testbeds/PoC
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