Requirements and viewpoints for backhaul synchronization draft-zhou-tictoc-ran-sync-req-00.txt Angela Zhou, Xiaodong Duan China Mobile

Outline Synchronization Requirements Mobile backhaul network Concerns on synchronization

Synchronization in 2G/GSM Current 2G/GSM Networks Sync Requirements in current 2G/GSM Networks –SDH transport network need frequency sync: +/- 50ppm –Base stations need frequency sync: +/- 0.05ppm –Reference clock is distributed via an explicit transport at the physical layer: PDH/SDH Future 2G/GSM Networks Sync Requirements in future 2G/GSM Networks –Packet switching network do not need strict synchronization –Base stations need frequency sync: +/- 0.05ppm –For base stations, Reference clock is distributed via PSN, need physical synchronization support (e.g. Sync Ethernet) or packet-based synchronization (e.g. 1588). Note: Previous SDH transport network maybe still exist for traditional base stations, sync requirement is the same as before. BTS BSC Ref. clock MS SDH E1 BTS BSC Ref. clock MS IP BSC MS PSN IP BTS Circuit Emulation E1 FEGE

Synchronization in 3G/TD-SCDMA Current trail 3G/TD-SCDMA Networks Sync Requirement in current 3G/TD-SCDMA Networks –SDH transport network need frequency sync: +/- 50ppm –For transport network, Reference clock is distributed via an explicit transport at the physical layer: PDH/SDH –Base stations need frequency sync: +/- 0.05ppm, and phase sync: +/- 3us –For base stations, reference clock is distributed via GPS Future 3G/TD-SCDMA Networks Sync Requirement in future 3G/TD-SCDMA Networks –Packet switching network do not need strict synchronization –Base stations need frequency sync: +/- 0.05ppm, and phase sync: +/- 3us –For base stations, reference clock is distributed via PSN, need physical synchronization support (e.g. Sync Ethernet) for frequency sync or packet-based synchronization (e.g. 1588) for time/phase sync. RNC NodeB SDH ATM RNC NodeB PSN FE GE Ref. clock

Synchronization in 4G/TDD-LTE/FDD-LTE Possible synchronization requirements in LTE –Synchronization requirements in ALL-IP network –Synchronization requirements in distributing Base Station (mesh topology among base stations) –Synchronization requirements in distributing BBU & RRU –Synchronization requirements in radio interfaces Note: synchronization requirement in LTE is under discussion. AGW eNB PSN Ref. clock eNB

Synchronization in different parts Base station Base station controller Base station UE Radio Interface SYNC Ref. Clock Network SYNCNode SYNC Requirements schematic diagram Synchronization requirements in different positions LayerSub ItemsFrequency AccuracyPhase Accuracy Network SyncE150ppm- STM-N4.6ppm- PTNNot so strict- Node SyncController-Base station 50ppb(If base station pick up time from base station controller) 3us(if base station pick up time from base station controller) Inter-Base station50ppb(If base station pick up time from other base station) 3us(If base station pick up time from other base station) Radio interfaceGSM50ppb- WCDMA50ppb- TD-SCDMA50ppb3us TDD LTE50ppbTBD FDD LTE50ppb-

Outline Synchronization Requirements Mobile backhaul network Concerns on synchronization

Mobile backhaul Mobile backhaul could be based on –Carrier Ethernet (e.g ad, PBB-TE) –IP/MPLS (e.g. PW, VPLS, L3VPN,IP routing) –T-MPLS –Others Each transport technique can fit certain scenario respectively, and they could be used in different network layers (access/aggregation/core).

Mobile backhaul Mobile backhaul network Base station IP/MPLS core Base station controller PBT Base station 802.1ad Base station DLS PON Base station controller Base station IP/MPLS core Base station controller TMPLS Base station TMPLS Base station controller TMPLS Base station controller Base station IP/MPLS core Base station controller Base station MPLS AGG VLL/VPLS MPLS Access 802.1ad CoreAggrAccess

SON & Self-backhauling AGW 1AGW 2 New BS Join Ref. Clock Self Organization Network –Some BSs are configured only by its mother BS for both sync and radio resource Self-backhauling –Using in-band connection between BSs for backhaul

Outline Synchronization Requirements Mobile backhaul network Concerns on synchronization

Concerns & Summary The requirements for RAN is clear and urgent –Radio Access Network is on the early stage of moving to IP transport –Using GPS will affect the flexible deployment of BS, we really need a new synchronization technology to substitute GPS, epically though a simple Ethernet port –How to distribute synchronization through packet based network? Can 1588 meet our requirements? Telecom profiles of 1588 should be standardized: network scale/ network load/ local clock accuracy Security –The synchronization methods in next generation mobile network (LTE) and MESH/SON network should be paid more attention. At the same time, it is complex and more technologies in backhaul –How to extend IEEE1588 or other synchronization technology so that it can be used smoothly in PBN and complex backhaul. –Features needed for Backhaul nodes to support 1588 for high accuracy –Different layers shall collaborate to meet the sync requirements form end to end, so what kind of mechanisms/protocols are need between different layer and technologies in backhaul?

Thank you& Any questions?