Requirements and viewpoints for backhaul synchronization

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Requirements and viewpoints for backhaul
synchronization

• draft-zhou-tictoc-ran-sync-req-00.txt
• Angela Zhou, Xiaodong Duan
• China Mobile

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Outline

• Synchronization Requirements
• Mobile backhaul network
• Concerns on synchronization

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Synchronization in 2G/GSM

• Current 2G/GSM Networks

• Future 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

• 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.

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Synchronization in 3G/TD-SCDMA

• Future 3G/TD-SCDMA Networks

• Current trail 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.

• 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

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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.

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Synchronization in different parts

• Requirements schematic diagram

• Synchronization requirements in different
  positions

Layer Sub Items Frequency Accuracy Phase Accuracy
Network Sync E1 50ppm -
Network Sync STM-N 4.6ppm -
Network Sync PTN Not so strict -
Node Sync Controller-Base station 50ppb(If base station pick up time from base station controller) 3us(if base station pick up time from base station controller)
Node Sync Inter-Base station 50ppb(If base station pick up time from other base station) 3us(If base station pick up time from other base station)
Radio interface GSM 50ppb -
Radio interface WCDMA 50ppb -
Radio interface TD-SCDMA 50ppb 3us
Radio interface TDD LTE 50ppb TBD
Radio interface FDD LTE 50ppb -
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Outline

• Synchronization Requirements
• Mobile backhaul network
• Concerns on synchronization

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Mobile backhaul

• Mobile backhaul could be based on
• Carrier Ethernet (e.g. 802.1ad, 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).

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Mobile backhaul

• Mobile backhaul network

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SON Self-backhauling

• 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

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Outline

• Synchronization Requirements
• Mobile backhaul network
• Concerns on synchronization

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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?

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Thank youAny questions?