synchronization in utran

Synchronization in UTRAN

Iu

UTRAN

UE

Uu

CN

• Network SynchronizationNetwork Synchronization:

• Node SynchronizationNode Synchronization

• Frame (Transport channel) SynchronizationFrame (Transport channel) Synchronization

• Radio Interface SynchronizationRadio Interface Synchronization

• (Time Alignment handling)(Time Alignment handling)

Frame Synchronization

Node Synchronization

Network Synchronization

Synchronization areas

RNC

RBS

UE

. . .RBS RBS

•Node Synchronization•Frame (Transport channel) Synchronization

RadioInterfaceSynchronization

Iub

Core Network


Synchronization functions

Dependence Among Synchronization Functions

• Network Synchronization is responsible for the distribution of clocks, and allows the clocks to operate at the same frequency in different nodes.

• Node Synchronization functionality is the basis for the numbering of frames between the RNC and RBS nodes, and for frame timing. The correct operation of Node Synchronization functionality is dependent on the proper operation of Network Synchronization.

• Frame Synchronization functionality is responsible for the numbering of user frames, and for the transmission and reception of frames to and from the RNC node at the correct times, to compensate for transfer and processing delay in the RNC-RBS path. The correct operation of the Frame Synchronization functionality on Intra-RNS case is dependent on the proper operation of the Node Synchronization functionality.

• Radio Interface Synchronization is responsible for the alignment of radio frames between the RBS and the UE.

Network Synchronization overview • System Clock• Radio BB (Base Band) Clock

• The system clock is defined as a stable clock that is needed in each WCDMA• RAN node and works as a slave clock locked to the synchronization reference. The

system clock generates an accurate and stable clock signal of 19.44 MHz, which is distributed within the WCDMA RAN node. The system clock handles the transmission network part providing a clock reference signal to the transmission network interfaces and the internal switching and transport of data within the RNC or RBS.

• The system clock is phase locked to the selected synchronization reference and follows the phase of the selected active reference in conditions when the reference is fault free.

• A fault free synchronization reference is when the jitter and wander characteristics of the reference are within the limits of the specifications and there are no signal interruptions or phase discontinuity. Normally, the reference is traceable to a PRC.

• If synchronization reference is changed, the phase synchronization of the system clock to the original reference is lost, and the synchronization to the new reference is performed.

Radio Base Band (BB) clock• The radio Base Band (BB) clock is a stable clock that is needed

in the WCDMA RAN node for the application specific functions. The radio BB clock works as a slave clock locked to the synchronization reference.

• The radio BB clock handles the radio network part providing a reference for carrier frequency generation and acting as timing reference for baseband processing in the RBS.

• The radio BB clock is phase locked to the same synchronization reference as the system clock.

• The radio BB clock handles the following: Synthesizing of an accurate and stable clock signal of 30.72 MHz,

acting as reference for the carrier frequency generation Generation and distribution of a frame synchronization signal

(100 Hz) and a 12 bit frame counter value

Network Synch – working modes• Warm Restart state (when the TU is restarted and the previous mode of

the clock is either Locked or Holdover mode)

Modes:

• Start-Up mode (warm-up, including the oscillator warm-up time)

• Locked mode (normal working mode when the clock is locked to the

reference)

• Holdover mode (no reference available but there is stored data to control

the outputs)

• Free Running mode (no reference available)

• Failure mode (when a hardware fault is detected)

• Loss of Tracking mode (when the clock can not trace the reference)

How to read Synchronization=1 moSynchronizationId 1

degradationIsFault 0 (degrNotFault)

syncRedundancy 0 (SYNCH_USE_PLANE_A)

syncRefActivity i[8] = 1 1 2 99 99 99 99 99

syncRefPriority i[8] = 3 4 2 0 0 0 0 0

syncRefStatus i[8] = 3 0 3 99 99 99 99 99

syncReference [8] =

> syncReference = Equipment=1,Subrack=MS,Slot=6,PlugInUnit=1,Etm4=1,Os155PhysPathTerm=pp1


> syncReference = Equipment=1,Subrack=MS,Slot=4,PlugInUnit=1,TimingUnit=1,TuSyncRef=1

:

> syncReference =

systemClockA 2 (lockedMode)

systemClockB 2 (lockedMode)

userLabel

Synchronization=1 after pulling 10Mhz clock ref

degradationIsFault 0 (degrNotFault)

syncRedundancy 0 (SYNCH_USE_PLANE_A)

syncRefActivity i[8] = 2 1 1 99 99 99 99 99

syncRefPriority i[8] = 3 4 2 0 0 0 0 0

syncRefStatus i[8] = 3 0 0 99 99 99 99 99

syncReference [8] =



> syncReference = Equipment=1,Subrack=MS,Slot=4,PlugInUnit=1,TimingUnit=1,TuSyncRef=1

:

> syncReference =

systemClockA 2 (lockedMode)

systemClockB 2 (lockedMode)

• In ring networks there is always a risk for timing loops. One way is to use SSM (Synchronization Status Message) or timing marker. An another way is to use GPS as a synchronization source in every node in the ring. Both methods gives automatic recovery of synchronization to all nodes.

• In Ericsson WCDMA RAN system the latter one is chosen. WCDMA P3 has full support for GPS and in P2 a stand-alone GPS receiver with a 2 MHz output signal can be used.

Synchronization in Ring Networks

References: (These documents not to be distributed to customer, except the Standard document.)

• Document 1/10260 FCP 103 3436 for a description of timing loops in ring networks.

• Design Rules for Synchronization Network 1/10260-2/HSM 10101/7

• The standard: Transmission and Multiplexing (TM), Synchronization network engineering. ETSI EG 201 793.

Synchronization in Ring Networks

12

1

1

Network

DD

FF

2

Assumethat twolinksbreaks..EE

Timing loop

EE

FF

DD

12

1

1

When these two linksbreaks, the

synchronisation trailforms a closed loop!

A

Timing Loopwill occur

2

Network

Timing loop

The objective is to minimise the number of manual actionsand the number of affected nodes in case of a link failure.

This gives a “horseshoe” shaped synchronisation distribution tree.

How to synchronise a ring (PAMS)

If a single link fails, a manual action must be taken to recover the synchronisation network.Manual recovery can beavoided by using GPS inevery node in the ring.

After the link has beenrepaired, the network must be restored to the normal (original)plan.

How to synchronise a ring (PAMS), Manual Recovery

• Radio Interface Synchronization (UE - UTRAN)

• Timing Alignment Handling (UTRAN - CN: Just in Time delivery)

• Network Synchronization (Node clock ref.: long term stability)

• Frame (Transport Channel) Synchronization (Intra UTRAN TrCh sync)

• Node Synchronization (Intra UTRAN phase relations)

TimeAlignmentHandling

Transport channel/NodeSynchronization

RadioInterfaceSynchronization

NodeB

RNC

Vocoder

NodeB

NodeB

NodeB

NodeB

RNS

UTRAN

Core Network

UE1 UE 2

RNC

Frame SynchronizationNode Synchronization

Synchronization Issues Model

BFNRFN

CNIu

Iub

DHO

SRNC

RBS

MAC-x

RFN

DHO

DRNC

BFN

Iub

RBS

MAC-x

Iur



Frame Synchronization (1)

Frame Synchronization (2)


Synchronization areas

NOTE: UTRAN/FDD nodes (RBSs) are NOT synchronized w.r.t. Radio frame timing ! (asynchronous system).

• The Node Synchronization function perform node timing offset measurements (within an RNS and stored in RNC). No adjustments performed.

• Node Sync inter-node phase relations are used as a base for determining offset values for Frame sync (transport).

• Node Synchronization accuracy normally better than 1 msec.

• Node Synchronization performed continuously on a CRNC – Node-B basis (default every 15 minutes for each Node-B).


• Node Synchronization only within one RNSno RNS-RNS timing difference measurements

• Use DL/UL Node Synchronization control frames within a RNS through a dedicated, high priority connection via a static “AAL0” VC.

• Handle DL/UL Node Synchronization control frames in the User plane, received over Iur (DCH - AAL2). MV issue and RBS related. Not used by Ericsson, but “supported”.

• Up to two instances of NodeSynch mo type can exist per RBS, one for each TimDevice.

Notes on Node Synchronization

IubLink=121,NodeSynch=1 mo• NodeSynchId 1• accuracy 863• controlFrameT 200• noOfRetries 3• noOfSamples 5• phaseDiffThreshold 2• phaseMeasurement 15897531• qEval 5• reservedBy [2] = • >>> reservedBy = RncFunction=1,IubLink=121,NodeSynchTp=1• >>> reservedBy = RncFunction=1,IubLink=121,NodeSynchTp=2• supervisionIntervalT 15• timeStamp 2005-05-06 10:40:59• userLabel NodeSynchRbs121

Node Sync usage

• Node Sync is used to get phase differences between the RNS reference counters (in RNC and RBSs). Phase relations are stored in RNC, no ‘slave’ adjustments done.

• Node Sync inter-node phase relations are used as a base for determining offset values for Frame sync (transport).

• Node Sync is used to get a better and faster Frame Sync offset values for new connections and e.g. after a RBS restart.

Node Synchronization procedure

• The phase relation between RNC and a RBS can be determined by Node Sync Control Frames (t1, t2 and t3 and standardised over Iub, t4 is RNC internal)

• These RNC-RBS phase difference are used as a base for determining Frame transport offset values between RNC and RBS

• Default is 5 samples and the median value is used

These two paths (t2-t1 + t4-t3) give together the Round Trip Delay (RTD)

SRNC

Node B

[BFN]

[RFN]1 2 3 44094 4095 0

149 150 151 152146 147 148

DL NodeSynchronizationControl Frame

[t1=4094.125]

UL NodeSynchronizationControl Frame

[t1=4094.125, t2=149.250, t3=150.5]

t1

t2 t3

t4

Node Sync and Frame Sync usage

• Node Sync CFs are, for inter-node time phase measurements, used via Common channels over Iub

• Node Sync CFs can also be used via DCH over Iur/Iub in order to get a grip of round trip delay figures

• (Frame) Sync CFs are used to check Time-of-arrival• Timing Adjustment CFs are used when frames are late or early

CommonCH Iub:

Same asfrom SRNC

DCH Iur/Iub:

DL: Node Sync orSync

Control Frames.

UL: TimingAdjustment,

Node Sync orSync

Control FramesNode B

SRNC

Node B

DRNC

Common CHIub:

DL & ULNode

Sync orSync

Control Frames

DCH Iur/Iub:

Same asfrom SRNC

• Frame Synchronization is responsible for pacing of traffic frames from the SRNC to the RBSs (downlink towards the Uu) and schedule/combine traffic frames from the RBSs (uplink).

• Frame Sync is used between SRNC and RBS to secure that frames are received in time, within the “receiving windows”.

• Frame Sync is standardised in Downlink only. Though, the same principle applies in Uplink but is RNC internal.

Frame Synchronization

DchFrameSynch=1 mo• DchFrameSynchId 1• doStep 1• dto 10• reservedBy [2] = • >>> reservedBy = RncFunction=1,UeRabType=1• >>> reservedBy = RncFunction=1,UeRrcType=1• tProcRbsDl 5• tProcRbsUl 10• tProcRncDl 1• tProcRncUl 1• toAE 195• toAEUl 96• toAWE 2• toAWEUl 2• toAWS 30• toAWSUl 41• uoStep 1• userLabel DchFrameSynch for Speech• uto 10

DchFrameSynch=2 mo• DchFrameSynchId 2• doStep 1• dto 11• reservedBy [1] = • >>> reservedBy = RncFunction=1,UeRabType=2• tProcRbsDl 8• tProcRbsUl 15• tProcRncDl 1• tProcRncUl 1• toAE 195• toAEUl 95• toAWE 2• toAWEUl 2• toAWS 30• toAWSUl 40• uoStep 1• userLabel DchFrameSynch for Packet• uto 11

CchFrameSynch=1 mo

• CchFrameSynchId 1• doStep 1• dto 15• tProcRbsDl 5• tProcRncDl 1• toAE 195• toAWE 2• toAWS 30

BFN RBS Frame Number counter (Range: 0 to 4095 frames, = 40.96 sec.)

RFN RNC Frame Number counter (Range: 0 to 4095 frames)

SFN Cell System Frame Number counter. SFN is sent on BCH. (Range: 0 to 4095 frames)

CFN Connection Frame Number (counter). Used for the L2/transport channel synchronization between UE and UTRAN. (Range: 0 to 255 frames for FACH/DCH, 0 to 4095 frames for PCH).

RFN

BFN

Iu

Iub

Uu

CFN

BFN

SFN

CFN CFN CFN...

Relations

SFN

Basic Counters/Clocks

More on Sync Counters

• BFN RBS common Frame Number Counter. Reference for Cells in RBS. 4096 counter.Related to SFN via Tcell. Also used for Nodesync purposes (t2 and t3).

• RFN RNC Frame Number counter. Reference in RNC.4096 counter. Node Sync reference (t1, t4).

• CFN Connection Frame Number counter. CFN is usedboth in UTRAN and in UE. 256 or 4096 counter. On common channels and for 1st RL:UTRAN is“CFN master”.

After 1st RL, UE is the ‘CFN master’.

Usage of CFN

RNS 2

UE1

NB1

SRNC

DHO

DRNC

DHO

Iu

RFN RFN

NB2 NB3 NB4

UL receiving window(not standardised)

DL receiving window

Iub

Iur

RL1 RL2 RL3 RL4

SFN SFN SFN SFN

Transport NetworkMultiplexing Equipment.

RNS 1

BFN BFN BFN BFN

Uu- UL/DL mechanism- Data labelled with CFN- Node Off/TDV

Sync related user plane procedures

SRNC NB

Timing Adjustment

SRNC

DL Synchronisation

NB

UL Synchronisation

SRNC

DL Node Synchronisation

NB

UL Node Synchronisation

• Synchronization

• Node sync

• Timing adjustment

DCH Frame transport in downlink direction

• DL TBS transmission is adjusted to fit receiving window by adjusting the DL TBS timing from northern node

• When frames are received too late or early, Timing adjustment control frames are sent to northern node, which adjusts timing

TOAWS tproc

150149DL Radio Frames 151 152

Early

t

DL frame #152received in Node B:

OK Too late

LTOA

Late

Receiving Window

TOAWE

Positive TOANegative TOA

TOA Time Of ArrivalLTOA Latest Time Of ArrivalTOAWS TOA Window Startpoint

TOAWE TOA Window Endpointtproc Processing time before transmission on

air-interface

t

DCH Frame transport in uplink direction

• UL TBS transmission timing is adjusted by moving the receiving window position internally in upper node (SRNC)

• When frames are received too late or early, the Receiving window position is adjusted in a similar way as for downlink

78UL combination time instantin SRNC for frame #80 (CFN):

79 80

Early

t

OK Too late

LTOA

Late

Receiving Window

8180UL Frames from Node B(CFN): 82 83

UL frame #80received in SRNC:

CFN range of 256

• CFN range is 256 frames• Timing relations must only cover +/-half the CFN range

i.e. +/-128. The reason is to avoid mirroring!• The range must also be feasible for L3 signalling integrity• Large window: delays <-> Small window: discarded data

CFN range 256

0

t

Correct Offset value

255

CFN range 256

0 255

T0 T1Tfalse

False Offset value

Forbidden Offset values Forbidden Offset values+/-128 is OK

Reference

CFN timing alignment at handover

• RLs are setup via Iur and DRNC at Inter RNS softhandover• UE measures and reports Offset between Cells• DL Frames are sent at the same time from SRNC• UL combining is mandatory in SRNC and optional in DRNC

RNS 2Frame Offset and

Chip Offset sent viaRNSAP to DRNC

UE1

NB1

SRNC

DHO

DRNC

DHOIu (RANAP) RFN RFN

NB2 NB3 NB4

UL receiving window(not standardised)

DL receiving window

Iub

Iur

OFF and Tm are reportedvia RRC as UE moves

from cell to cell

RL1 RL2 RL3 RL4

SFN SFN SFN SFN

Transport NetworkMultiplexing Equipm.

RNS 1

Frame Offset andChip Offset sent viaNBAP to Node B

BFN BFN BFN BFN

Uu

Trace measures• Network

• TUBs: trace1 Nss*

• TUBs: trace1 trace2 trace3 trace4 trace5 trace6 trace7 trace8 trace9 state_change bus_send bus_receive send_sig Nss_tu*

• Node

• TUBs: trace1 trace2 trace3 trace4 Tu_rn*

• TUBs: all NODE_SYNCH

• Frame

• //Search for dOffset (downlink) and timerOffset (uplink)

• SPBs: trace2 trace3 FRAME_SYNCH_UE

• SPBs: bus_send bus_receive FRAME_SYNCH_UE

• SPBs: bus_send bus_receive IUB_IUR_UP_UE

synchronization in utran

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