www.mtigroup.com/mobile Public
Cloud RAN fronthaul
Options, benefits and challenges.
Aleksandra Checko, Industrial PhD student [email protected]
iJOIN Winter School "5G Cloud Technologies: Benefits and Challenges„ Bremen, 2015-02-23
www.fp7-harp.eu
www.mtigroup.com/mobile 2 Public
Outline of today’s presentation
Base station architecture evolution towards C-RAN – Traditional base station (past) – With RRH (present) – Cloud RAN (C-RAN) (present/future)
Fronthaul network – Bitrate, delay and sync requirements – Transport medium – Transport solutions
Fronthaul evolution
How? Why?
www.mtigroup.com/mobile 3 Public
Traditional base station
Base station evolution
Telecom Italia Demo
Base station with RRH
www.mtigroup.com/mobile 4 Public
Through base station with Remote Radio Head
Currently deployed
Power efficient
Easy cooling
For different standards
Interface: – Open Base Station Architecture Initiative (OBSAI) – Common Public Radio Interface (CPRI) (some parts are vendor-
specific) – Open Radio Equipment Interface (ETSI-ORI)
Fiber up to 20-40 km, usually p2p
Baseband Unit (BBU) a.k.a. Data Unit
Bas
eBan
d
Traditional Macro BS
Antenna
BScell
Tran
spor
t
Con
trol
Syn
ch
RF
PA
BS with RRH
Antenna
cell
RRHRF
BBU
Bas
eBan
d
Tran
spor
t
Con
trol
Syn
ch
www.mtigroup.com/mobile 5 Public
To C-RAN architecture
Proposed by IBM in 2010 Cloud, Centralized processing, Cooperative radio, Clean
RF
RF
C-RAN with RRHs
Virtual BBU Pool
RRH
RRH
RRH
RF
Bas
eBan
d
Syn
ch
Con
trol
Tran
spor
t
Bas
eBan
d
Syn
ch
Con
trol
Tran
spor
t
Bas
eBan
d
Syn
ch
Con
trol
Tran
spor
t
Bas
eBan
d
Tran
spor
t
Con
trol
Syn
ch
Fiber – Digital BaseBand Coax cable – RF
www.mtigroup.com/mobile 6 Public
Cloud RAN
Remote sites - RRH
FRO
NTH
AUL
Source: http://www.mti-mobile.com/
Source: http://krnet.or.kr/
Data center – BBU Pool
www.mtigroup.com/mobile 7 Public
Fronthaul transport network
- “link” between RRH and BBU
P2P link for base station with RRH Fronthaul network based on
– WDM – Ethernet – OTN
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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)
www.mtigroup.com/mobile 9 Public
Which medium to choose?
Medium Bit rate Distance Remarks
Fiber 100Gbps + Tens km
Copper 10 Gbps 100 m
Microwave 1 Gbps (80GHz) 1.5 km LoS required
0123456789
10
2011 2012 2013 2014 2015 2016
Mill
ion
Mobile Backhaul Connections by Medium
Air
Fiber
Copper
Source: Infonetics Research, March 2012
Why to consider microwave, not fiber everywhere?
www.mtigroup.com/mobile 10 Public
(Yes, people are working on compression)
Majority of algorithms – 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 – 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
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Transport solution
Technology is ready (capacity not necessarily)
CPRI / OBSAI
CPRI / OBSAI
WDM
CPRI / OBSAI
CPRI / OBSAI
Microvawe
Compression Compression
Eth/CPRI/ OBSAI
Eth/CPRI/ OBSAI
Ethernet
CPRI/ OBSAI
CPRI/ OBSAI
OTN
BBU Pool
RRH
CPRI / OBSAI Point to point
WDM-PON
www.mtigroup.com/mobile 12 Public
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
0,0
0,5
1,0
1,5
2,0
0 10 20 30 40 50 60 70 80 90 100
Mul
tiple
gai
n
Office cells (%)
A. Checko, H. Holm, H. Christiansen, ” Optimizing small cell deployment by the use of C-RANs”, European Wireless 2014
www.mtigroup.com/mobile 13 Public
Timing in fronthaul
Timing is really important Frequency of transmission Handover, coding
00 01 02
00 01
02
Device A Device B
Solution: timing distribution GPS PHY layer clock – SyncEth Packet-based timing
IEEE 1588v2 (PTP) Multiple
Requirements Phase error LTE-A with eICIC/CoMP:
± 1.5 - 5 μs, MIMO: 65 ns Frequency error LTE – A TDD/FDD:
±50 ppb
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Shared Ethernet is even better for cost-saving
Access network - fronthaul
Aggregation network - backhaul
BBU Pool
CPRI / OBSAI
RemoteRadio Heads
CPRI / OBSAI
Aggregation network - fronthaul
Aggregation network - backhaulRemote
Radio Heads
IQ over Eth
CPRI2EthGateways
BBU Pool
GPS, 1588, ect
RRH
CPRI
GPS?, 1588?, new solution?
Variable delay
RRH++
BBU Pool++
Traditional fronthaul
Packet-based fronthaul
Sync delivered together with data (CPRI)
New Sync solution needed
BBU
Switching Multiplexing Widely deployed (reuse!) ! Fronthaul cost savings vs problems with delays ! Synchronous CPRI vs asynchronous Ethernet
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HARP optimization
Looking when to use C-RAN Combining fiber and microwave Optimizing cell-BBU assignment
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Deploying C-RANs
Trade off – 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
www.mtigroup.com/mobile 17 Public
Optimization model
To maximize multiplexing gain and minimize fiber cost In multi C-RANs scenario
Aggregated Traffic (h)
Aggregated Traffic (h)
24 h
24 h
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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
R. Al-obaidi; et. Al. ”C-RAN deployment scenarios”, DTU, 2014
Backhaul network
Base Stations
LTE
MWR
Fronthaul network Backhaul network
BBU Pool
CPRI
RemoteRadio Heads
MWR
FiberAggregated Traffic (h)
24 h
S1
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Updates from industry
No more CPRI?! 4G towards 5G
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It is time to rethink fronthaul towards 5G
New functional split between BBU and RRH
– To reduce fronthaul data rate – Decoupling user-processing and
cell-processing
No more CPRI? Need for interface supporting:
– Variable bit rate (traffic dependent to enjoy multiplexing gain)
• To increase scalability
– Packet-based • Synchronization is a challenge
– Multipoint to multipoint – Fully standardized
BBU Pool--
RRH
BBU Pool
Current C-RAN
Future C-RAN
10 Gbps
10 Gbps
2 Gbps
2 Gbps
2 Gbps
RRH++
BBU Pool--
2 Gbps
3 Gbps
3 Gbps
Vendor A
Vendor A
Vendor A
Vendor B
Vendor C
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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 multi-
point packet-based fronthaul interface supporting load balancing
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Wrap Up
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Costs
– 2x2 MIMO, 20 MHz LTE,
15+1 CPRI 2.5 Gbps
– 3 sectors? 7.5 Gbps
– Tens of BS over long
distance? 100s Gbps
Costs vs savings
Fever BBUs? Fronthaul
cost?
Savings
– Equipment
– Energy
Re-define fronthaul
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Base station architecture evolution
BaseBand RF
a) Traditional Macro BS
Antenna
RF
RF
c) C-RAN with RRHs
Virtual BBU Pool
BaseBandBaseBand
RRH
RRH
RRH
RF
Fiber – Digital BaseBand Coax cable – RF
BS
cell
BaseBand
RF
b) BS with RRH
Antenna
cell
RRH
BBU
RF
RF
d?) Possibly C-RAN with new function split between BBU and RRH
Virtual BBU Pool
BaseBandBaseBand--
RRH
RRH
RRH
RF
BB
BB
BB
FH network
www.mtigroup.com/mobile 25 Public
Deployment scenarios
A. Checko, et al. „Cloud RAN for Mobile Networks - a Technology Overview”, IEEE Communications Surveys & Tutorials
www.mtigroup.com/mobile 26 Public
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