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07 Synchronisation

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    1 Nokia Siemens Networks RU20 for Network Planners 2009

    3GTPL - Synchronisation

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    2 Nokia Siemens Networks RU20 for Network Planners 2009

    RAN1254 Timing Over Packet (TOP)

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    RAN1254 Timing over Packet Feature

    Timing over Packet (ToP) provides the means to provide asynchronization reference for base stations in Ethernet/packettransport networks

    No need for separate TDM links for providing a synchronization

    reference for base stationsNo need for GPS based synchronization sources at the base

    station sites

    Applicable for Iub/IP and packet-based backhaul with Pseudowire

    The Master Clock is implemented as a dedicated networkelement at the RNC site.

    Slave Clocks are integrated into the Ethernet interface units of

    the base stations ToP solution is based on the use of IEEE 1588 v2 protocol This protocol is also called Precision Time Protocol (PTP).

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    ToP Solution Overview

    At the RNC site there is a Master Clock

    The Master Clock has a timing reference traceable to a Primary

    Reference Clock (PRC) ToP can be used as synchronization alternative in packet networks havingno other possibility to synchronize the base station.

    RNC can not be synchronised with ToP

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    Timing over Packet Operating Principle

    The Master Clock sends Sync messages to the Slave Clocks The Slave Clocks recovers the synchronization reference byusing the Sync messages received from the Master Clock The Master and Slave Clocks communicate by using IEEE1588 v2 protocol

    Used is communication mode is unicast

    Unicast discovery (preconfiguration

    of slave clocks with the

    address of the master clock) and unicast

    negotiation are

    supported

    Sync messages and signaling messages are supported Sync messages are time stamped event messages Signaling messages are used for unicast negotiationsignaling messages are not time stamped

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    ToP Messages

    There are three types of Messages supported by NodeB:

    Announce

    Announce and Signaling messages are not time stamped, general

    messages. Announce messages are needed for maintainingthesynchronization

    hierarchy. A slave clock tries to lock to a master only

    if it receives Announce messages from the master.

    Signalling Signaling messages are used for unicast negotiation. Sync Sync messages are time stamped event messages. A slaveclockrecovers

    the timing reference based on the Sync messages sent bythe master clock.

    With the unicast options of IEEE 1588 v2, all slave clocks arepreconfiguredwith the address of the master clock. By using unicast negotiation, a slaverequests the master to send Announce or Sync messages. As a response,the master sends a grant in a signaling message, and after grant

    it starts to

    send Announce or Sync messages.

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    ToP QoS Requirements Low network Utilisation

    Low network utilization (< 50%)

    it is possible to introduce ToP

    without any additional measures in networks

    with less than 50% bandwidth utilization even as BE traffic.

    This Requires Maximum 50% link loading in the network No frame loss

    Maximum queue length 10 frames (preferably 3 frames)

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    ToP QoS Requirements High network Utilisation

    High network utilization (< 90-95%) If the network utilization is larger than 50% it is necessary to use Classes ofServices (CoS) in the network to ensure proper Quality of Service (QoS) forthe ToP

    packets.

    The load on the CoS containing the ToP traffic needs to be lowerthan the whole network utilization The high load scenario is discused further in the slides belowin terms of

    Priorisation Classification

    Policing

    Queuing

    Scheduling and shaping

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    ToP in High load network Classification

    The classification function at the ingress of each networkelement identifies the received packet or frame and assign itto the correct flow and the corresponding CoS

    for the further

    handling in the network element. The ToP packets or frames are identified

    UDP port plus the DSCP value

    VLAN ID plus the user_priority

    Note that the TP 5000 supports only 16 VLANS so a pure layer 2solution for Iub with VLANs needs a router for ToP master forcreating the VLANs.

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    ToP in High load network Policing andBandwidth Assignment

    Bandwidth has to be reserved for each connection with QoSguarantees in a network supporting QoS better than just BE.

    The bandwidth needed per ToP

    connections between

    Master and Slave with 16 synch messages per second:

    Direction from Master to Slave:

    On IP level: 9.3 kbps per connection

    On Ethernet level :

    12.1 kbps per connection

    Direction from Slave to Master: On IP level: 0.005 kbps per connection On Ethernet level : 0.006 kbps per connection Bandwidth can be reserved by CAC or by manualconfiguration depending on the network. Policing functions at networks boundaries may be necessary

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    ToP in High load network Queuing

    The support of ToP requires that the network is designed in such a waythat for ToP frames queues are only needed for rate adaptation betweeningress and egress.

    Only short queues of less than 100 frames are needed for this purpose inthe ideal case it should be even less than 10 frames.

    Queues for handling of traffic bursts and congestion requiring longerqueue length should be avoided for ToP flows. . A frame loss of < 2% is acceptable for ToP. Queues for ToP flows should be short even with the risk of slightlyhigher frame losses.

    Tail Discard, RED or WRED do not make a difference to ToP

    Sophisticated drop mechanism can lead to lower network loadbenefiting also ToP messages.

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    Scheduling and shaping

    Scheduling mechanisms ToP or voice are sensitive to delay and jitter but these connectionstypically have low bandwidth requirements compared to other services. These services should be served with highest strict user priority. WRR or WFQ may suit the other traffic in the interface better so anoptimal scheduler is a combination of WRR/WFQ and Strict Priority.

    Shaping ToP load is relatively constant and quite low Shaping is not necessary as compared to e.g. TCP/IP data traffic

    Shapers introduce additional delay and also under some

    circumstances additional jitter and this is harmful for ToP messages.

    AXC & FTM

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    Timing over Packet Parameters

    AXC C5.0FTM C5.0

    AXC & FTM

    FTM

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    ToP ParametersFTM

    Timing over Packet the

    only choice if there is onlyEthernet interface activated

    Check this box to activateToP(License needed)

    FTM

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    ToP: DSCP and PHBFTM

    DSCP and PHB for ToP

    DSCP -

    46 and

    PHB -

    EF recommended

    FTM

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    Activating ToPFTM

    In the rare

    case that theToP Masteris in adifferentnetwork than

    the Transportinterface, it isnecessary toconfigureroutes under

    BTS Routing,not underBTS Routing.

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    Master clock options (aligned with RU10)

    Option 1: dedicated master / slave

    Symmetricom TimeProvider 5000

    New product based on NSN requirements formobile backhaul

    Cost efficient solution for RNC sites and hub sites

    Dual power supply, dual I/O card,1:1 node redundancy

    Option 2: upgrade of existing SSU

    Symmetricom SSU2000, large installed base

    Can be upgraded with an IEEE1588v2 blade

    Fully redundant node with various I/O options

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    Master clock options (aligned with RU10)

    Release 1.0

    IEEE 1588v2 GM

    GPS and/or E1 Inputs

    10MHz/1pps Outputs

    The RNC supports 2.048 MHz, 2.048Mbit/s

    and 1.544 MHz external

    synchronization interfaces

    VLAN Support (up to 16 VLANs)

    SNMP and CLI Management

    One IOC interface module

    2 x 100/1000Base-T SFPs

    More than 10 000 Timing packets persecond

    Rel 1.1 will have optional IOC slotgiving two additional Ethernet ports

    Supports VLAN p-bits and DSCPmarking

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    RAN1708 BTS Synchronous Ethernet

    BTS S h Eth t

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    BTS Synchronous Ethernet

    The main advantage of Synchronous Ethernet is that it can provide a high

    quality synchronization reference for base stations - the quality iscomparable to that of SDH

    Contrary to packet based synchronization techniques (e.g. ToP) the

    stability of the recovered frequency does not depend on network load ornetwork impairments like delay variation

    BTS S h Eth t

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    BTS Synchronous Ethernet

    BTS Synchronous Ethernet (SyncE) provides a mechanism for timingsynchronization over Ethernet of Flexi/Ultra

    BTS with Primary Reference

    Clock according to ITU G.8261spec

    The Ethernet transport interface of a BTS shall be SyncE capable SyncE as specified in RAN1708 is considered as an alternative to Timingover Packet (ToP) BTS synchronization, as specified in RAN1254

    BTS S h Eth t

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    Impact to UTRAN Transport dimensioning:

    IP-based Iub dimensioning requires a selection of the synchronization

    type: SyncE, ToP, none.

    SyncE contributes with an additional capacity on IP-based Iub atthe BTS side (Iub last mile), due to SSM message flow terminatedat BTS. Bandwidth requirement of the SSM flow is around 6.4kbps. Note: this is specified only in the Ethernet layer, and not in the

    IP layer.

    BTS Synchronous Ethernet

    BTS S nchrono s Ethernet

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    BTS Synchronous Ethernet

    The

    basic principle of Synchronous Ethernet (SyncE) is that at transmitting side

    Ethernetphysical layer signal is timed by using a network reference

    At receiving side the clock signal is recovered from the physical layer signal, in thisway SyncE

    is capable of carrying network synchronization reference from one

    network element to another

    BTS Synchronous Ethernet

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    BTS Synchronous Ethernet

    Interdependencies between features:

    BTS Synchronous Ethernet can only be used for IP enabled Flexi orUltraSite

    WCDMA BTS. One of the following features is a prerequisite:

    RAN74: IP based Iub for Flexi WCDMA BTS

    RAN1634: IP based Iub for UltraSite

    WCDMA BTS

    RAN1142: ATM over Ethernet (only with Flexi WCDMA BTS)

    RAN1449: Dual Iub for Flexi WCDMA BTS

    RAN1633: Dual Iub for UltraSite WCDMA BTSSystem Impact:

    Iub requires 1Gb SyncE

    capable interface card

    2 Alarms SSM* mismatch; SSM missing 2 Parameters SSM enbling flag; SSM message timeout*) -

    Synchronization Status Message

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