SCCPCH Concept & Implementation

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Add SCCPCH for Reduce FACH Cong.

Nexwave Strategic Solution

Overview :• Channel Concept• FACH Congestion• Add Secondary SCCPCH• Result Implementation Secondary SCCPCH

Overview


Channel Concept

• WCDMA is separted on 3 main channel: Logical, Transport and Physical Channel• FACH Channel and Paging channel which located on Transport channel is multiplexed

together on the same Physical Channel. This channel is called Secondary Common Control Physical Channel(S-CCPCH)


Channel Concept


FACH Congestion

• RAB AbnormalRelPS. RF.UuNo Reply increased when Data Fach Congestion is increased.

• From the performance, we can conclude the FACH channel is not congested. But the FACH data are not scheduled successfully

• So we need instigated more, why FACH congestion is occurred, otherwise FACH Band with usagerate is too low


FACH Congestion

The FACH channel data scheduleOn the downlink, the MAC will schedule the Sccpch data as follow:• Firstly, the PCH data will be scheduled on the

highest PRI;• Secondly, the FACH channel which is used to

transfer the signaling will be scheduled;• and last, the FACH channel which is used to

transfer the data will be scheduled.So, if the FACH data are can’t be scheduled, the reason may be:• there are so many FACH data so that the FACH

channel is congesting;• There are so many FACH signaling and PCH data

so that the FACH data can’t be scheduled timely.

Because of FACH and PCH is multiplexed together on SCCPCH, so we need to add SCCPCH on Physical Channel to separed FACH data and FACH Signaling +PCH.

FACH Channel data schedule


Add SCCPCH

• Problem: The main problem is FACH congestion which casue high PS drops, so the target is release FACH congestion aiming to improve Ps drops by adding 2nd S-CCPCHS-CCPCH: Carry FACH & PCH

• Cause analysis: A cell is configured with one S-CCPCH by default.The S-CCPCH carries one PCH, one FACH #0 that carries signaling, and one FACH #1 that carries service data.If two SCCPCHs are used, the first SCCPCH always carries only PCH, and the second SCCPCH always carries FACH#0 and FACH#1, so we doubled the FACH BW

• Action: Add Second SCCPCH Script add SCCPCH


Add SCCPCH Basic Information(ADD USCCPCHBASIC)

. Based on the product specifications, it is recommended that the CCPCHs in a cell be identified as follows: 1)The ID of the PSCH is 0. 2)The ID of the SSCH is 1. 3)The ID of the PCPICH is 2. 4)The ID of the PCCPCH is 3. 5)The ID of the PRACH #1 is 4. The ID of the corresponding AICH is 6. 6)The ID of the SCCPCH #1 is 8. The ID of the corresponding PICH is 10. 7)The ID of the SCCPCH #2 is 9.

PhyChId SCCPCH ID

Meaning: Uniquely identifying an SCCPCH corresponding to a paging indication channel in a cell.The ID of a common physical channel is used to identify a common physical channel in a cell. Each common physical channel is uniquely numbered within a cell. The IDs of common physical channels should be planned before the channels are configured for the cell.One cell can be configured with one to eight S-CCPCHs. It is recommended that one S-CCPCH be configured.

GUI Value Range: 0~255

Unit: None

Actual Value Range: 0~255

MML Default Value: None

Recommended Value: 8

Parameter Relationship: None

Service Interrupted After Modification: N/A

Impact on Network Performance: None

Parameter


Add SCCPCH Basic Information(ADD USCCPCHBASIC)

Script add SCCPCH

SCCPCHOffset SCCPCH Offset

Meaning: Sequential offset between the SCCPCH and PCCPCH in the cell. For detailed information of this parameter, refer to 3GPP TS 25.433 and 3GPP TS 25.211.

GUI Value Range: 0~149

Unit: chip

Actual Value Range: 0~149

MML Default Value: 50

Recommended Value: 50

Parameter Relationship: None

Service Interrupted After Modification: No (And no impact on the UE in idle mode)

Impact on Network Performance: As defined by the 25.211 protocol, the PICH timing is 7680 chips prior to its corresponding SCCPCH frame timing. If the offset of the SCCPCH timing from the PCCPCH timing is smaller than 30 (x 256 chips), the corresponding CFN decreases by 1. Then, the difference between the PICH CFN and the corresponding SCCPCH CFN is 2. However, in the 25.435 protocol, the PI information and paging message are transmitted with two consecutive CFNs. In the BSC6900, the PI information and paging messages are also transmitted with two consecutive CFNs irrespective of the chip offset. Therefore, the two protocols conflict with each other in this aspect. To avoid the compatibility problem, it is recommended that the SCCPCH timing carrying the PCH transport channel be set to between 31 and 149.


Result Implementation add SCCPCH

Log Result Before and After Runnin Script

Before Implementation

After Implementation


Result Implementation add SCCPCH

Result Perfromance

SCCPCH Concept & Implementation

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