TCH Assignment Scenario [PDF]

Zitiervorschau

TCH Assignment Scenario

1. The MSC sends an Assignment Request message to the BSS based on the service request and then starts timer T10. Upon receiving the Assignment Request message from the MSC, the BSC checks the channel type. If a PS service is requested, the BSC determines whether the requested service is supported 2. 2. The BSC sends the BTS a Channel Activation message to activate the corresponding terrestrial resources. The message carries IEs such as Activation Type, Channel Description, Level, and TA. 3. Upon receipt of the Channel Activation message, if the IEs carried in the message are correct, the BTS turns on the power amplifier on the specified channel to receive uplink messages. At the same time, the BTS sends the BSC a Channel Activation Acknowledge message carrying the absolute frame number, which is used by the BSC to determine Starting Time. 4. After receiving the Channel Activation Acknowledge message, the BSC sends the Assignment Command message on the signaling channel to the MS and starts timer T3107 ,The Assignment Command message carries IEs such as Channel Description, Power Command, and Channel Mode. 5. After receiving the Assignment Command message, the MS starts to transmit and receive signaling over the TCH. The MS sends an SABM message to the network over the FACCH through frame stealing. The SABM frame is the first frame for establishing the asynchronous balanced mode. Compared with the immediate assignment procedure, the assignment procedure does not have layer 3 messages. 6. After receiving the SABM message, the BTS sends a UA frame to the MS over the FACCH. The layer 3 messages are not carried. 7. At the same time, the BTS sends the BSC an ESTABLISH INDICATION message without the layer 3 messages. Then, the BSC responds with a UA frame for acknowledgement. 8. After receiving the UA frame, the MS sends an Assignment Complete message to the network over the FACCH, indicating that the TCH is established successfully. When receiving the Assignment Complete message, the BSC stops timer T3107. 9. In addition, the BSC fills the message with the corresponding information and sends the message to the MSC. Upon receiving the Assignment Complete message, the MSC stops timer T10.

Parameters Description T10 Supervision of the assignment procedure • Interpretation: The timer T10 supervises the assignment procedure • Timer start condition: The timer T10 starts before the BSC sends a PHYSICAL_CONTEXT_REQUEST message to the BTS. • Timer stop condition: The timer T10 stops when the MS sends either an ASSIGNMENT_COMPLETE or an ASSIGNMENT_FAILURE message to the BSC. • Action performed on timer expiry: When the timer T10 expires, the BSC sends an ASSIGNMENT_FAILURE message to the MSC. • Appropriate value: Min. = 4 s. Max. = 30 s. Def. = 8 s. Rule = T10 > T3107 It is recommended that T10 be at least 2 seconds longer than T3107. • Signaling diagram:

T3107 Supervision of the assignment procedure Interpretation: The timer T3107 supervises the assignment procedure and the internal intracell handover. • Timer start condition: The timer T3107 starts when the BSC sends an ASSIGNMENT_CMD message to the MS (via a BTS). • Timer stop condition: The timer T3107 stops when the BSC receives either an ASSIGNMENT_CMPL or ASSIGNMENT_FAILURE message from the MS. • Action performed on timer expiry: When the timer T3107 expires, the new and the old channel are released, all the appropriate MS connections are cleared, and an ASSIGNMENT_FAILURE message is sent to the MSC. In the case of the internal intracell handover, a CLEAR_REQUEST message is sent to the MSC. • Appropriate value: Min. = 3,5 s. Max. = 28 s. Def. = 6 s. Rule = T3107 < T10 It is recommended that T10 be at least 2 seconds longer than T3107. Signaling diagram:

Analysis and Recommendations  Analysis • After Checking Drop BSS overall BSCs , we found that all Drop BSS over all BSCs are Keeping high with the same trend not increased due to other actions • The main reason behind the Drop BSS is ABIS Fails ,so our Target is How to solve this ABIS Fails • We have 2 Reasons for ABIS Fails:  Small Timers Configuration from MSC and BSC during the TCH assignment  Transmission Issue

 Recommendations • We recommended to increase these 2 Timers T10 (From MSC) and T3107 (From BSC) to the Max Value to give more opportunity for the data to be received in case of Congestion over ABIS interface • Also after increasing these timers to the max , and we still have high Drop BSS that is mean at this time is Transmission and not related to parameter wise • The below is the Current and Recommended Configurations: Timer Name

Current Value

Recommended Value

T10

14 s

30 s

T3107

12 s

28 s

• We want to Go for the max Value Directly for the Trial , Specially this Timers are Just representing the window that the BSC and MSC will wait the Response from UE • We Propose BSC SANTE 1 or SANTE 2 for the Trial.

Drop BSS



Drop BSS is Keeping within normal trend for all BSCs

 

DROP BSS is Keeping within normal trend for BSCs (SP2 ,YAKRO 1 and Villa 1) Drop BSS Slightly Decrease for BSC Villa 2 after Change Card Action

ABIS Fails



ABIS Fails are Keeping within normal trend for all BSCs

 

ABIS Fails are Keeping within normal trend for BSCs (SP_2 ,YAKRO_1,Villa 1) There is Slight Decrease for BSC Villa 2 after Change Card Action

Thank you Copyright©2018 Huawei Technologies Co., Ltd. All Rights Reserved.

Page 11

HUAWEI TECHNOLOGIES CO., LTD.