ECOC2014 Sunday Workshop, WS5 Front-Haul challenges for future radio access Sep. 21 st, 2014 Shigeru Kuwano NTT Access Network Service Systems Laboratories, NTT Corporation kuwano.shigeru@lab.ntt.co.jp
Agenda Future Radio Access (5G) 2020 and beyond NG-PON2 for 5G MFH bandwidth reduction Cooperation between mobile and optical High speed backhaul NTT Confidential 1
Future Radio Access (5G) Various number of radio access technologies (RAT) Enhanced RAT New RAT Use of higher frequency bands (Low-SHF to EHF) Inter cell cooperation MBH Multi Frequency band cells (U-plane) MFH C/U plane Split (Dual Connectivity) U-plane C-plane Ultra high data rate Spot cells (e.g. > 10 GHz) NewRAT Small cells High data rate (e.g. 3.5 GHz) EnhancedRAT Macro cell User Equipment Moderate data rate/ C-plane (e.g. < 2 GHz) 2
Requirement MFH Accommodation of bandwidth explosion Reduction of optical bandwidth Low latency MBH Low cost high speed access Low latency connection between enbs for dual connectivity RAT Accommodation Bandwidth Latency (Oneway) Enhanced RAT (Small cells) New RAT (Spot cells) MFH > 40 Gbit/s (> 4 CPRI option7 links) MBH 10 Gbit/s ~ (Massive MIMO cell) 100 ~ 200 µs (Depends on implementation) 2~10 ms (between enbs) 3
NG-PON2 for 5G MFH WDM overlay Multiplexed transmission Higher rate more than current specification (G.989) Wavelength level monitoring (AMCC) TWDM-PON Reduced data rate transmission Cooperation between mobile and optical Challengeable MBH WDM overlay for spot cells Higher rate (> 10Gbit/s) more than current specification (G.989) Wavelength level monitoring (AMCC) TWDM-PON enbs with moderate rate (< 10 Gb/s) 4
Multiplexed transmission of CPRI Cost effective PtP transmission for macro cell WDM or TDM TDM is an economical solution for the bit rate of about 10 Gbit/s (e.g. CPRI option3 multiplexing). TDM Data format Dedicated format (e.g. byte multiplexing) CPRI over OTN (ITU-T G.709) PtP solution is under study. CPRI over Ethernet OAM functions Synchronization RRH CPRI CPRI MUX/ DEMUX Multiplexed transmission MUX/ DEMUX BBU 5
CPRI compression Reduce the redundancy of digitized IQ data Lossless and Lossy compression Lossless(preferable): LPC and Entropy coding Lossy(high performance): Sampling rate reduction and bit width reduction Compression ratio Lossless: 50 %, Lossy: 30~50 % Depends on latency and distortion Latency: ~10 µs Distortion (Lossy case): EVM < 1 % ETSI ORI (Open Radio Interface) Lossy compression (50%) Non-linear quantization Latency: 20µs (preferable) EVM < 3 % China Mobile C-RAN field trial Lossless compression (50%) Issues for 5G More information in the same radio bandwidth NOMA, 256QAM Smaller compression gain Larger distortion Higher latency EVM by IQ compression [%] 10 8 6 4 2 1 EVM degradation 0.01 db 0.1 db 1 db 64-QAM 16-QAM QPSK 0 0 5 10 15 20 25 30 Copyright 2014 System NTT EVM corp. All [%] Rights Reserved. 6
MFH Redefinition (Midhaul?) Redefinition of splitting point between BBU and RRH Drastically reduction of optical bandwidth can be achieved. Optical traffic is proportional to mobile traffic. Variable bit rate Functionality of mobile systems (e.g. C-RAN) should be kept. CoMP Latency requirement is the same. HARQ Many aggressive studies ALU, ijoin, ChinaMobile etc. Channel Coding Channel Coding Scrambling Scrambling Modulation Mapper Modulation Mapper Layer Mapper Precoding Resource Element Mapper Resource Element Mapper IFFT IFFT MAC Smaller bandwidth Larger bandwidth CPRI 7
TWDM-PON approach for MFH Statistical multiplexing of redefined MFH transports for effective use of optical bandwidth. Suitable for small cell cluster accommodation. Latency of conventional DBA is too high for MFH. Accurate time and frequency synchronization should be provided over TWDM-PON. DBA based scheduling RRH 100~200 m Splitter Shared Fiber BBU/ OSU(OLT) Shared Network Equipment 5~10 km BBU OLT RRH UE Request Data Signal PON Scheduling Grant Data High Latency Time 8
Mobile DBA Cooperation between mobile and optical scheduling. scheduling based PON scheduling. Lower than 50 µs latency can be achieved. BBU OLT RRH UE Scheduling PON Scheduling Grant Data Signal Data Low Latency Time Latency (µs) 10000 1000 100 Proposed (1 ) Conventional (1 ) Proposed (4 s) Conventional (4 s) 10 0 1 2 3 4 5 6 7 Data rate per (Gb/s) 9 T. Tashiro et al., OFC2014
High speed transport for MBH NewRAT BH will require high bit rates (> 10 Gbit/s). High speed (40 ~ 100 Gbit/s) and Low cost optical access interface is needed. Candidates 100GE, 400GE based technologies PAM DMT Low cost WDM Digital coherent (if extremely low cost interface can be realized ) Challenges Link budget for high speed WDM overlay Low cost optics and electronics 10
Summary WDM overlay To support high speed transport (~ 40 Gb/s) Monitoring capability TWDM-PON Challengeable for MFH. Redefined MFH interface is essential. Cooperation between mobile and optical for proper operation. Standardization is VERY important. Not only G.989 series NGMN, ORI, etc. 11
Thank you! 12