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PON Architecture for Wireless Backhaul

PON Architecture for Wireless Backhaul. Paul Wilford. October 28, 2009. 1. The mobile backhaul problem. The mobile backhaul problem. Current Wireless Carrier Environment Increased bandwidth demands Due to more advanced users and handsets Mobile broadband (killer app)

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PON Architecture for Wireless Backhaul

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  1. PON Architecture for Wireless Backhaul Paul Wilford October 28, 2009

  2. 1 The mobile backhaul problem

  3. The mobile backhaul problem Current Wireless Carrier Environment • Increased bandwidth demands • Due to more advanced users and handsets • Mobile broadband (killer app) • TDM Backhaul is not efficient for packet data • Doesn’t fit well in traditional T1 Architecture

  4. The mobile backhaul problem Data is becoming the primary use of the network

  5. The mobile backhaul problem Traffic ARPU 2000-2005 2005-2010 2010-2020 New mobile data services require exponentially increasing bandwidth but generate less revenue per bit transported than voice services. • 100 Kb/s for GSM GPRS (downlink) • ≥100 Mb/s for LTE (downlink) This will break the traditional voice-optimized TDM Mobile Backhaul (MBH) network • Legacy leased line capex and opex scale linearly with bandwidth

  6. 2 Landscape of today

  7. BaseStation Voice Channels IP Channel GSM UMTS NodeB Landscape of today SGSN – Serving GPRS Support Node GGSN – Gateway GPRS Support Node PDSN – Packet Data Support Node HSGW – HRPD Serving Gateway RNC – Radio Network Controller DoRNC – Data Optimized RNC BSC – Base Station Controller MSC – Mobile Switching Center HRPD – High Rate Packet Data (1xEV-DO) Separate Core Networks for different Radio Access Networks DoRNC Voice Channels IP Channel 3G1X HRPD PDSN/HSGW BTS BTS

  8. Landscape of today • Examples of customer deployments – Customer ‘X’ • Customer ‘X’ primarily uses ATM for backhaul. The overall strategy is to seek higher-capacity, lower-cost solutions as the more data-centric technologies such as HSDPA drive capacity requirements. • The target state architecture is one that is flexible and can scale as capacity demand increases. Some solutions being considered include fiber to the cell site and bonded copper. • Customer ‘X’ has a combination of GSM/UMTS networks and will need to integrate backhaul for all networks as it migrates from GSM to UMTS to LTE.

  9. Landscape of today • Examples of customer deployments – Customer ‘Y’ • Customer ‘Y’s backhaul strategyconsists of delivering Ethernet over the existing copper infrastructure with a migration to fiber-based Ethernet backhaul services. • Customer ‘Y’ plans to leverage its Fiber to the Premise (FTTP) network with pseudowire to provide backhaul services.

  10. 3 Landscape of Tomorrow

  11. Landscape of tomorrow – Evolution to a common core GSM and CDMA voice and data networks converge into an IP-based evolved packet core (EPC) For LTE, IP data from the eNodeB connects directly to the EPC RNC Voice Channels BaseStation IP Channel GSM UMTS NodeB LTE SGW HSGW PDN GW DoRNC Voice Channels IP Channel BTS 3G1X HRPD MME PCRF BTS

  12. Landscape of tomorrow - 4G/LTE Mission Improved SpectrumEfficiency 3-4x HSPA Rel’6 in DL* 2-3x HSPA Rel’6 in UL 1 bps/Hz broadcast High Peak Data Rates 100 Mbps DL (20 MHz, 2x2 MIMO) 50 Mbps UL (20 MHz, 1x2) *Assumes 2x2 for DL in LTE, but 1x2 for HSPA Rel’ 6 Improved CellEdge Rates 3-4x HSPA Rel’6 in DL* 2-3x HSPA Rel’6 in UL Full Broadband Coverage Scalable Bandwidth 1.4, 3, 5, 10, 15, 20 MHz LTE Network Co-existence UMTS, GSM, HRPD, CDMA Packet Domain Only Simplified Network Architecture Low Latency < 5ms User Plane (UE to RAN edge) < 100ms camped to active < 50ms dormant to active Radio Access Network Core Network

  13. Landscape of tomorrow – Technology Innovation With increased spectral efficiency, reduced latency and increased bandwidth, LTE enables innovations to improve performance at the handset. An example of this is CoMP.

  14. 4 What is CoMP?

  15. Controller High-speed backhaul Today’s network Interference Desired signal Desired signal All signals are potentially useful – no interference! Each user is connected to a single base Data rates limited by interference What is CoMP? – Cooperative Multi-Point Overcome inter-cell interference by coordinating Tx/Rx at several base stations, thereby greatly increasing user rates and system capacity. Each user is connected to several bases

  16. What is CoMP? - System Outline Backhaul that conveys both uplink and downlink baseband signal. Handset Base Station Base Station CoMP Processor Handset Base Station Handset Base Station Performs downlink and uplink CoMP beamforming. Handset Base stations communicate with a centralized CoMP processor. The backhaul network conveys both uplink and downlink signals.

  17. What is CoMP? – Coherent vs. Non-Coherent • Coherent • Uses I/Q samples for CoMP processing in time or frequency domain • Requires the highest bandwidth from the backhaul network • Potential for greatest gain at the handset • Non-coherent • Uses soft bits for CoMP processing • Requires less backhaul bandwidth than coherent scheme

  18. What is CoMP? – Uplink and Downlink • Uplink • To perform uplink CoMP, I/Q samples or soft bits must be transmitted to the CoMP processor • Downlink • To perform downlink CoMP there are two options: • Data and beam forming coefficients sent to each base station • I/Q samples or soft bits sent to each base station • After CoMP processing performed at CoMP processor • The backhaul network must support the required data distribution to all nodes • Channel State Information is required for beam forming • Different base stations adjust the amplitude and phase of the transmission of the signals to the handsets to achieve improved handset performance

  19. What is CoMP? - Requirements • CoMP schemes demand for • High bandwidth • multiple Gbit/s (DL &UL coherent, time domain) • <1 Gbit/s (DL & UL coherent, frequency domain) • about 100 Mbit/s (non-coherent) • Low latency • about 1 ms (all schemes, optimal case) • high backhaul latency may become a show stopper for CoMP • Need for a backhaul solution that is low latency The Technical challenge is to meet the latency requirement under fully loaded conditions. This requires sophisticated scheduling and MAC Layer processing.

  20. 5 Different PON technologies

  21. Different PON technologies • PON technologies: • APON – ATM PON • First PON standard – used primarily for business applications • 622 Mbps/155 Mbps • BPON – Broadband PON • Extension of APON – added OMCI (OAM Management Control Interface) and WDM capability • 622 Mbps/155 Mbps • GEPON/EPON – Ethernet PON • IEEE 802.3ah Standard • 1Gbps/1Gbps • GPON – Gigabit PON • ITU-T G.984 Standard • Evolution of BPON • 2.5Gbps/1.25Gbps

  22. Different PON technologies • PON technologies: • 10G EPON – 10G Ethernet PON • Extension of GE/EPON • 10 Gbps/1 Gbps • XGPON – 10G GPON • Extension of GPON • XGPON1 – 10 Gbps/2.5 Gbps • XGPON2 – 10 Gbps/10 Gbps • GPON is a suitable backhaul technology for packet-based services • For increased capacity and to support applications like CoMP, XGPON2 is the best backhaul solution

  23. 6 Synchronization

  24. Synchronization: Problems with synchronization • Base station radio interface typically requires some level of synchronization • Frequency accuracy • Time/phase accuracy • Base station backhaul interface (typically legacy base stations) may be synchronous (T1/E1) • Synchronization considerations • Relative phase stability • Mobile hand-off between base stations • Coherent CoMP • Core network may or may not be synchronous • (Traditional) Ethernet, Synchronous Ethernet, SONET, etc. • Separate timing distribution network may or may not exist • GPS, NTR, etc.

  25. E1/Sync E GPON PHY 8 kHz clock IEEE 1588v2 (when PRC not avail. at OLT) PRC PRC GPON-fed cell site gateway (ONU) E1, Eth E1, Eth ONU GPON GPON frame t Cell site OLT RNC/BSCGateway ONU GPON frame t ONU GPON frame t IP/ Ethernet Network GPON frame t RNCBSC OLT Synchronization: GPON Mobile Backhaul End-to-End Synchronization • The GPON Transmission Convergence (GTC) layer supports the transport of an 8 kHz clock via 125 microsecond framing • Therefore GPON provides deterministic synchronization like TDM • However, CoMP requires something better • To achieve more precise timing synchronization, provisions must be made to compensate for the OLT-ONU delay variations

  26. 7 The MAC Layer

  27. The MAC Layer: GPON • GPON QoS is maintained through transmission containers (T-CONTs) • T-CONT classes • Type 1 – fixed bandwidth • Type 2 – assured bandwidth • Type 3 – allocated bandwidth + non-assured bandwidth • Type 4 – best effort • Type 5 – superset of all of the above • Scheduling algorithm at the GEM Layer guarantees that transmission container bandwidth and latency guarantees are satisfied under fully loaded conditions • Dynamic Bandwidth Allocation • Maximum fiber bandwidth utilization • Based on queue status from ONUs • Security (via AES) • FEC

  28. The MAC Layer: Backhaul challenges • CoMP data processed and sent to downstream path for scheduling/reflection to ONUs • Very low latency requirement of 1 ms • Handoff between eNodeBs requires tighter synchronization at base stations • OLT must send additional information to ONUs so they know neighboring ONU timing for handoffs • FEC at 10 Gbps • Completing R-S computations for 10 Gbps within 125 us is challenging

  29. The MAC Layer: CoMP timing messages Scheduling for QoS and CoMP reflection S1/X2 translation 10G FEC encode CoMP processing. Data fed to downstream GEM Layer for reflection to ONUs S1/X2 translation 10G FEC decode

  30. 8 Conclusions

  31. Conclusions • XGPON2: • Is a backhaul solution that can accommodate growth in bandwidth demand • Is a backhaul solution that connects to the simplified network architecture • Is a backhaul solution that can integrate data from 2G,3G and LTE networks • Is a backhaul solution that can handle the uplink and downlink data distribution requirements for applications like CoMP • Is a backhaul solution that is synchronous and is compatible with IEEE 1588v2 synchronization through packet networks • Is a backhaul solution that contains efficient scheduling in the MAC layer for maintaining QoS under fully loaded conditions

  32. Thank You!

  33. Backup Slides

  34. The MAC Layer: ONU block diagram

  35. Conclusions: Broadband Access Networks can support 3G/LTE Bandwidth Requirements GPON satisfies LTE bandwidth needs • 2.5G DS/1.25G US shared • Optical split adjusted as required. • Future evolution to 10G PON (λ overlay on same PON) XGPON2 satisfies LTE bandwidth needs • 10G DS/10G US shared 10G PON > 1000 GPON 500 Bonded VDSL2 supports HSPA+ and early LTE VDSL2 100 LTE DL Speed [Mbps] ADSL2+ HSPA+ 24 Wireline SHDSL.bis 10 ADSL2 ADSL2+ and SHDSL.bis are tactical solutions for 2G  3G 8 ADSL HSPA 4 Wireless 1 UMTS GPRS 0,512 2000 2002 2004 2006 2008 2010 2012

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