Timing and Synchronisation Challenges in Wireless Infrastructure
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Timing & Synchronization in Wireless Infrastructure Harpinder Singh Matharu Senior Product Manager, Comms Division, Xilinx 11/4/2010 © Copyright 2010 Xilinx Topics . Wireless Infrastructure Market Trends . Timing & Synchronization in Base stations . Challenges & Opportunities © Copyright 2010 Xilinx Page 2 Mobile Network witnessing rapid growth Trend • Heterogeneous Network Mobile Traditional Network Investment – 80% Network– • Backhauling & Synchronization 20% a challenge © Copyright 2010 Xilinx Page 3 Revenue & CAPEX/ OPEX disparity Lower Cost CAPEX/OPEX per bit New Business Models Revenue Rapid increase in Data Traffic Expenditure / Revenue Expenditure 2G (GSM/CDMA/UMTS) +3G/4G (HSPA, WiMAX, LTE, LTE Advanced) Time • Maximizing spectrum utilization • Ease of network deployment & management • Leveraging value/ intelligence in the network © Copyright 2010 Xilinx Page 4 Base station Architectural shift Mast Mast Mounted Mounted RRH RRH CPRI/ OBSAI Traditional CPRI/ OBSAI CPRI/ OBSAI Centralized BTS Remote Radio Heads Shift from co-located to distributed BTS Architecture © Copyright 2010 Xilinx Remote Radio Heads enable Power Savings Antenna Array Antenna Array X X X X X X X X X X X X X X X X X Remote Radio Head X X X X X X X X X X After feeder loss No Feeder loss Radio Cards Channel Cards Power received – 30 W PA – 30W Channel Cards Coaxial Feeder Cable Fiber • Short length • Long haul • ~3dB Loss • No Loss Power Available – 60 W Distributed Base Station Traditional Base Station Significant CAPEX/ OPEX Impact Remote Radio Heads Cabinet (RRH) Fiber replaces Coaxial Cable for significant CAPEX/ OPEX Savings © Copyright 2010 Xilinx Standardization of Radio Interface BASEBAND REMOTE RADIO HEAD ANALOG CARD N LAYER 2 & 3 + NIC LAYER 1 - PHY E T W O R K B A C DIGITAL FRONT END K H A CONTROL CARD U L FIBER CPRI/OBSAI INTERFACE © Copyright 2010 Xilinx Page 7 Radio Interface Standards – Drivers & Benefits . Drivers: – Reduce BTS cost, power, and complexity – Make module level expertise & ecosystem viable . Benefits: – Off-the-shelf modules – Lower cost and shorter time to market – Faster technology / innovation adoption © Copyright 2010 Xilinx Topics . Wireless Infrastructure Market Trends . Timing & Synchronization in Base stations . Challenges & Opportunities © Copyright 2010 Xilinx Page 9 Timing & Synchronization Challenge in RRH Remote Radio Heads GPS Remote Radio Heads Base station Core Network IEEE1588/ NTP Timing & Synchronization I/Q Data Control Messaging Tight timing & synchronization needs to enable Remote Radio Heads © Copyright 2010 Xilinx Page 10 System Timing Requirements 0.5ms 1 2 3 4 5 6 7 8 9 10 eNodeB System Frame = 10 ms U-Plane IQ Data Round Trip Delay = 5 µs ANTENNA MODEM LTE TDD/ Control Link Delay Or Card Accuracy <= UTRA-TDD Channel REMOTE REMOTE REMOTE (Clock) TX-RX Switch = Card 8.138 ns RADIO RADIO RADIO 16.276 ns HEAD HEAD HEAD Fiber Link (10- 20 km) BTS Channel Card Chassis Daisy Chained Remote Radio Heads © Copyright 2010 Xilinx Page 11 Transmit Diversity/ MIMO Timing Requirements ANTENNA MODEM Control Or Card REMOTE Channel REMOTE (Clock) RADIO Card RADIO HEADHEAD BTS Channel Fiber Link (10-20 km) Card Chassis Phase Difference <= 65 ns Sources: 3GPP – 25.104/ 36.104 © Copyright 2010 Xilinx Page 12 CPRI Protocol Terminology ANTENNA ANTENNA OPTICAL OR OPTICAL RADIO RADIO EQUIPMENT RADIO EQUIPMENT CONTROLLER (REC) ELECTRICAL LINK OR EQUIPMENT (RE A) ELECTRICAL LINK BASEBAND CHASSIS (RE B ) D0 D1 D2 CPRI CPRI CPRI (Master) CPRI (MASTER) (Slave) (Slave) D0 D1 D2 D0 D1 D2 Packets flow between REC and RE A Packets flow between REC and RE B Link Speeds = 0.6; 1.2; 2.4; 4.9; 6.144G + 9.8G (spec expected to be released soon) © Copyright 2010 Xilinx Page 13 CPRI Protocol Frame Synchronization CONTROL DATA FRAME DELIMITER 0 1 2 3 SYMBOL 0 0 1 – 15 WORDS 1 NODE B FRAME HFN SFN SFN NUMBER 2 BASIC FRAME NUMBER (260.42 ns) 3 5 6 BFN 0 BFN 255 HYPER-FRAME (66.67 µs) 62 63 HF 0 HF 149 Control Sub Channels in a Hyper-frame SYSTEM FRAME ( 10 ms) © Copyright 2010 Xilinx CPRI Protocol – Clock Synchronization Remote Radio Head Electrical or Optical Electrical REFERENCE CLOCK PLL +/- 0.002 ppm with Master Clock Interface & VCO/ VCXO RECOVERED TRANSCEIVERS CLOCK CLOCK DATA RECOVERY (CDR) CPRI link similar to synchronous Ethernet in Clock Recovery © Copyright 2010 Xilinx Page 15 CPRI Protocol – Link Delay Accuracy Challenge Air Interface Mapping Scheme / or Optical Electrical Multi Air Interface ROUND TRIP Application Interface I/Q Data DELAY Layer Mapping Framing MEASUREMENT Control TRANSCEIVERS Messaging TDM (I/Q Data & Control) Data(I/Q & Control) TDM RECEIVE FIFO Round Trip Delay Accuracy of < = 16.276 ns fairly challenging © Copyright 2010 Xilinx Page 16 Ethernet over CPRI 0 1 2 3 0 1 2 *p 3 5 Up to 211 Mbps Bandwidth ETHERNET P PHY 62 63 Control Sub Channels in a Hyperframe Could spare Ethernet bandwidth be used for PTP to reduce timing cost? © Copyright 2010 Xilinx Page 17 Topics . Wireless Infrastructure Market Trends . Timing & Synchronization in Base stations . Challenges & Opportunities © Copyright 2010 Xilinx Page 18 Fiber Sharing – CPRI over Carrier Ethernet? Network Convergence MODEM Control Or Card Channel REMOTE REMOTE REMOTE (Clock) Card RADIO RADIO RADIO HEAD HEAD HEAD FIBER SHARING – Currently dedicated fiber link being laid out for Radio Interface © Copyright 2010 Xilinx Page 19 Small Cell Connectivity PTP plus Ethernet over Power? RADIO MODEM HEAD IEEE1588/ NTP Tower Mounted Core Network Integrated Small Base Station IEEE 1588 – Could PTP + Power over Ethernet be used in the last segment? © Copyright 2010 Xilinx Page 20 Summary . Mobile Network witnessing exponential growth . Architectural innovations to keep CAPEX /OPEX in bounds . Standardization important for healthy ecosystem . Challenges & Opportunities abound © Copyright 2010 Xilinx Page 21.