Cloud RAN fronthaul Options, benefits and challenges. iJOIN Winter School "5G Cloud Technologies: Technologies: Benefits and Challeng Challenges„ es„ Bremen, 2015-02-23 2015-02-23 Aleksandra Checko, Industrial PhD student Aleksandra.Checko@mtig Aleksandra
[email protected] roup.com
www.fp7-harp.eu
Outline of today’s presentation Base station architecture evolution towards C-RAN –
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Traditional base station (past) With RRH (present) Cloud RAN (C-RAN) (present/future)
Fronthaul network –
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Bitrate, delay and sync requirements Transport medium Transport solutions
Fronthaul evolution
Why?
How?
Base station evolution
Telecom Italia Demo
Traditional base station
Base station with RRH
Through base station with Remote Radio Head
A n t e n n a
Currently deployed Power efficient l h r o c t n n y o S C
Easy cooling For different standards
BS cell
Interface: –
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–
Traditional Macro BS
Open Base Station Architecture Initiative (OBSAI) Common Public Radio Interface (CPRI) (some parts are vendorspecific) Open Radio Equipment Interface (ETSI-ORI)
Fiber up to 20-40 km, usually p2p Baseband Unit (BBU) a.k.a. Data Unit
t r d o n p a s B F A n e R P s a r a T B
l h o r c t n n y o S C
A n t e n n a
RF
RRH
t r d o n p a s B n e a s r a T B
BBU cell
BS with RRH
To C-RAN architecture Proposed by IBM in 2010 Cloud, Centralized processing, Cooperative radio, Clean
RF
RRH RF
t d t r d d l t r l n t r o d n h l o r o n a l o h r h o p n a c o t r o p a c h B r t s a p n o c r B t n s p c n B e t n s n y n B e n o n s n y s e o n a y s S n e o n a y r C s a S o a r C s a S a r T a C S a B r T C B T B T B
RF
RRH
Virtual BBU Pool
C-RAN with RRHs Fiber – Digital BaseBand
Coax cable – RF
RRH
Cloud RAN Data center – BBU Pool
Remote sites - RRH
L U A H T N O R F Source: http://www.mti-mobile.com/
Source: http://krnet.or.kr/
Fronthaul transport network - “link” between RRH and BBU P2P link for base station with RRH Fronthaul network based on –
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–
WDM Ethernet OTN
Requirements on bitrate & timing 20 MHz LTE, 2x2 antennas (MIMO) – 150 Mbps for users, 2.5 Gbps on
fronthaul link (CPRI)
Delay < 3 ms RRH-BBU-RRH (HARQ) ≈ 0.1- 0.2 ms on fronthaul
(CMCC) Jitter < 65 ns (MIMO, 36.104) Frequency error < 50 ppb (Macro BS, 36.104) BER < 10e-12 (CPRI, for specific application)
Which medium to choose? Medium
Bit rate
Distance
Fiber
100Gbps +
Tens km
Copper
10 Gbps
100 m
Microwave
1 Gbps (80GHz)
1.5 km
Remarks
LoS required
Why to consider microwave, not fiber everywhere? Mobile Backhaul Connections by Medium 10 9 8 7 n 6 o i l l i 5 M 4
Air Fiber
3
Copper
2 1 0 2011
2012
Source: Infonetics Research, March 2012
2013
2014
2015
2016
(Yes, people are working on compression) Majority of algorithms –
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Remove redundancies in spectral domain, Perform block scaling, Use non-uniform quantizer Up to 33% (3:1) compression ratio for 8% EVM ALU, IDT
University of Texas at Austin –
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rescaling, non-uniform quantization, noise-shaping error feedback Resampling 5:1 ratio
One algorithm detects user activity – up to 7%! (14:1) –
Telefonica I+D
Transport solution Point to point
CPRI / OBSAI
BBU Pool
RRH CPRI / OBSAI
CPRI / OBSAI
WDM WDM-PON
Microvawe
Compression
CPRI / OBSAI
CPRI / OBSAI
Compression OTN
CPRI/ OBSAI
Eth/CPRI/ OBSAI
CPRI/ OBSAI
Ethernet Eth/CPRI/ OBSAI
Technology is ready (capacity not necessarily)
Ethernet enables to maximize multiplexing gains Among others to reduce cost of BBU pool
A. Checko, et al. ” Cloud RAN for Mobile Networks - a Technology Overview”, IEEE Communications Surveys & Tutorials 2,0 1,5 n i a g g 1,0 n i x e l p 0,5 i t l u M 0,0 0
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30
40
50
60
70
80
90
100
Office cells (%) A. Checko, H. Holm, H. Christiansen, ” Optimizing small cell deployment by the use of C-RANs”, European Wireless 2014
Timing in fronthaul
Timing is really important
Frequency of transmission Handover, coding
00 01 02
00 01 02
Requirements
Phase error LTE-A with eICIC/CoMP: ± 1.5 - 5 μs, MIMO: 65 ns Frequency error LTE – A TDD/FDD: ± 50 ppb Device A
Solution: timing distribution
GPS PHY layer clock – SyncEth Packet-based timing IEEE 1588v2 (PTP) Multiple
Device B
Shared Ethernet is even better for cost-saving Switching Multiplexing Widely deployed (reuse!)
! Fronthaul cost savings vs problems with delays ! Synchronous CPRI vs asynchronous Ethernet Access network fronthaul
Aggregation network backhaul
Remote Radio Heads
Aggregation network - fronthaul Remote Radio Heads
BBU Pool
Aggregation network backhaul
BBU Pool
IQ over Eth CPRI2Eth Gateways
CPRI / OBSAI
Sync delivered together with data (CPRI)
CPRI / OBSAI New Sync solution needed
GPS, 1588, ect
GPS?, 1588?, new solution?
CPRI
Variable delay BBU
RRH
RRH++
Traditional fronthaul
Packet-based fronthaul
BBU Pool++
HARP optimization
Looking when to use C-RAN Combining fiber and microwave Optimizing cell-BBU assignment
Deploying C-RANs Trade off –
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Fiber length Cells in the C-RAN Multiplexing gain
TCO vs. capacity
A. Checko, H. Holm, H. Christiansen, ” Optimizing small cell deployment by the use of C-RANs”, European Wireless 2014
Optimization model To maximize multiplexing gain and minimize fiber cost In multi C-RANs scenario Aggregated Traffic (h)
24 h
Aggregated Traffic (h)
24 h
Partial C-RANs
Partial C-RAN –
Some sites are excluded from the C-RAN and are backhauled to the nearest C-RAN site by MWR
Fronthaul network
Remote Radio Heads
Backhaul network
CPRI
MWR
BBU Pool
S1
Aggregated Traffic (h)
Fiber
LTE
24 h
MWR
Base Stations
Backhaul network
R. Al-obaidi; et. Al. ”C-RAN deployment scenarios”, DTU, 2014
Updates from industry
No more CPRI?! 4G towards 5G
It is time to rethink fronthaul towards 5G New functional split between BBU
Vendor A Vendor A
and RRH –
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10 Gbps
To reduce fronthaul data rate Decoupling user-processing and cell-processing
10 Gbps
BBU Pool
Current C-RAN
RRH
No more CPRI? Need for interface
Vendor A
supporting: –
Variable bit rate (traffic dependent to enjoy multiplexing gain) •
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To increase scalability
2 Gbps
2 Gbps
BBU Pool--
Vendor B
Packet-based •
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Vendor C 2 Gbps
2 Gbps
Synchronization is a challenge
3 Gbps
3 Gbps
Multipoint to multipoint Fully standardized
BBU Pool--
RRH++
Future C-RAN
Timely topic IEEE 1904.3 - encapsulation and mapping of IQ data over Ethernet IEEE 802.1 – CPRI fronthaul discussion with Time Sensitive Networking
task force CPRI CPRI2? 3GPP - proposal on a study item on variable rate multi-point to multipoint packet-based fronthaul interface supporting load balancing
Wrap Up
Costs vs savings
Costs –
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Savings
2x2 MIMO, 20 MHz LTE,
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Equipment
15+1 CPRI 2.5 Gbps
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Energy
3 sectors? 7.5 Gbps Tens of BS over long distance? 100s Gbps
Fronthaul cost?
Fever BBUs?
Re-define fronthaul
Base station architecture evolution A n t e n n a
A n t e n n a
RF
BaseBand
RRH
BaseBand
RF
BBU
BS
cell
cell
a) Traditional Macro BS
RF
b) BS with RRH
RRH
RF
RRH
BB RF
RRH
RF
RRH
BB
FH network BaseBand BaseBand
RF
RRH
Virtual BBU Pool
BaseBand BaseBand --
RF
RRH
BB
Virtual BBU Pool
c) C-RAN with RRHs Fiber – Digital BaseBand
d?) Possibly C-RAN with new function split between BBU and RRH Coax cable – RF
Deployment scenarios
A. Checko, et al. „Cloud RAN for Mobile Networks - a Technology Overview”, IEEE Communications Surveys & Tutorials
Take away points Fronthaul network capacity is a deal breaker for introducing C-RAN Fronthaul solutions so far rely on legacy deployments Industry is working on “redefining” fronthaul – towards switchable,
multipoint-to-multipoint connections, with a strong focus on Ethernet based solutions
Thank you for your attention
www.fp7-harp.eu
