1. CPRI-T (Fronthaul through transport of CPRI signal from RRH to the C-RAN baseband.)
Jishnu Aravindakshan

2. ©Tejas Networks Proprietary & Confidential
What is Fronthaul (FH)?
Cellsite
Cellsite
Antenna
Centralized CoMP (C-RAN)
Architecture
Antenna
RRH
Fronthaul
RRH
Cellsite
BBU
Antenna
BBU
To backhaul
To backhaul
Hubsite
Existing distributed
Architecture
RRH
< 20 Km
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3. Ref Note: Extracted from CPRI v6.1 requirements
CPRI (Common public Radio Interface) is a standard interface used to connect Radio Equipment Controller/REC (BBU) with one or more of Radio Equipment/RE through single or multiple hop technologies
The current standard is CPRIv6.1 published on 01/07/2014
The physical layer can support both electrical and optical interface.
For fronthaul we will be concerned with only optical interface
This specification defines the Layer 1 (optical characteristics, flow multiplexing, low level signaling) and Layer 2 (MAC, Flow control, data protection of control and management flow)
CPRI operates at a basic frame rate of 3.84MHz or UMTS chip rate of 3.84 Mbps
Ref Note: Extracted from CPRI v6.1 requirements

4. CPRI REC and RE for E-UTRA
Ref Note: Extracted from CPRI v6.1 requirements

5. Ref Note: Extracted from CPRI v6.1 requirements
CPRI Frame Basics
CPRI Option
Data Rate 1
614 Mbps 2
1.28 Gbps 3
2.45 Gbps 4
3.07 Gbps 5
4.92 Gbps 6
6.14 Gbps 7
9.83 Gbps 7A
8.11 Gbit/s (64B/66B) 8
10.13 Gbps (64B/66B) 9
12.16 Gbps (64B/66B)
Basic frame duration = 1/3.84 ~ ns
Basic word consist of 16 words; W = 0 to 15
Length of the word (T) is based on the CPRI line rate. It varies from 8 bit (CPRI1) to 192 bit (CPRI9)
W=0 is used for control word (CW), W=1to 15 is used for IQ sample transmission
CW is equal to T for CPRI 1-7,7A but is equal to 128 for CPRI 8,9
Ref Note: Extracted from CPRI v6.1 requirements

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CPRI-T
For CPRI transport the following consideration will be important
Topology and resiliency
CPRI supports point-to-point, chain, tree and ring topology
In case of CPRI-T,
Ring topology will the most appropriate to handle the link failure in case of optical fiber
In case of MW backhaul point-to-point link may be a viable option due to the distance and capacity constraints of radio link
Capacity and Range
MW : GHz or E-band (70-80 GHz ) : Range (100m to max of 7 km) and Capacity (CPRI 1-3).
Optical : Range (Can support 20 Km and even more), Capacity (CPRI 1-9)
Latency requirement
One way delay of 250us for new BS (and 100us for existing equipment)
CPRI-T BER < 10-12
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7. CPRI-T Technology Option
Dark fiber (Not viable from an opportunity cost perspective)
Passive WDM
xPON (Asymmetric make it unsuitable for fronthaul)
WDM PON or Injection locked SFP (Not manageable)
Active WDM : 20 Km distance does not need this option
Microwave (Short distance)
Circuit emulation over Ethernet
OTN
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8. CPRI-T FaaS (Fronthaul as a service)
Native transport of CPRI
Ability to multiplex WiFi Backhaul (BH) with CPRI-T FH
Ability to support multiple operators with the same infrastructure
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9. ©Tejas Networks Proprietary & Confidential
Reference
CPRI Interface specification
NGMN Fronthaul Evolution
NGMN Fronthaul Requirements
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10. Jishnu Aravindakshan (Tejas Networks Ltd) jishnu@tejasnetworks.com
THANK YOU
Jishnu Aravindakshan (Tejas Networks Ltd)