Gsm Kpi Improvement

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GSM KPI Improvement Process / Guidelines

Key Performance Indicators - KPIs
SDCCH Blocking SDCCH Drop TCH Drop Rate Handover Success Rate

Limited Internal

2

NPI Training - Retainability

2005-09-30

Accessibility Definition
Call to an MS
MSC/VLR 1 TRC 1 BSC 5 3 2

1. MSC/VLR sends paging command to all BSCs belonging to the location area (LA) where MS is located 2. BSC forwards the paging command to all BTSs in that LA, and the BTSs in their turn page the MS on the PCH 3. The MS responds to the BTS on the RACH and the BTS forwards the response to the BSC (forward to MSC) 2

Accessibility

2

4

4. The BSCs checks with the BTS if it has an SDCCH available and the BTS grants the MS an SDCCH by using the AGCH 5. The MS and the BTS signal on the SDCCH, measurement reports sent on SACCH are forwarded from the BTS to the BSC and once the signalling is done the BSC decides which TCH to use 6. TCH connection established between MS and BTS

BTS BTS 3 2 4 6 5

Limited Internal

3

NPI Training - Retainability

2005-09-30

SDCCH Congestion – Overview
SDCCH Activities:  Mobility Management
– Normal Location update – Periodic Registration – IMSI Attach / Detach

 Connection Management
– – – – Call setup SMS Point to Point Fax Setup Supplementary Services

Limited Internal

4

NPI Training - Retainability

2005-09-30

SDCCH Congestion – Overview
Channel Configuration:  Channel Configuration can be done as follow – Combined BCCH/SDCCH on 1 TS (SDCCH/4) – Non-Combined BCCH and SDCCH on 2 TS (SDCCH/8)

 Cell Broadcast Channel (CBCH)
– – The Cell Broadcast service provides the transmission of an SMS from a message-handling centre to all MSs in the serving area of the BTS. If the Cell Broadcast service is active in a cell, one signaling sub-channel is replaced by one CBCH resulting in a SDCCH/7

Limited Internal

5

NPI Training - Retainability

2005-09-30

SDCCH Congestion – Overview
SDCCH Channel Allocation Profile (CHAP)    Channel Allocation is the feature that selects and allocates suitable channels when one or more channels are required Channel Allocation Profile (CHAP) is the parameter that provides different channel allocation strategies For SDCCH assignments, CHAP 8 prioritize new assignments as follows: 1. OL/SDCCH 2. UL/SDCCH (if OL/SDCCH is congested)

Limited Internal

6

NPI Training - Retainability

2005-09-30

SDCCH Congestion – Overview
A new assignment will use the SDCCH in OL first
B S T T T T P P T S T T T T T T T T T T T T T T T T T T T T T T OL (CHGR 0) B S T P BCCH timeslot SDCCH timeslot TCH timeslot PDCH timeslot

UL (CHGR 1)

If the OL is congested, the SDCCH in UL will be used
B S T T T T P P T S T T T T T T T T T T T T T T T T T T T T T T OL (CHGR 0)

UL (CHGR 1)

Note SDCCH congestion in the OL will increment, but this is not customer perceived since the SDCCH in UL will then be utilized

Limited Internal

7

NPI Training - Retainability

2005-09-30

SDCCH Dimensioning Strategy
GOS Approach:  SDCCH should be dimensioned for better GOS compare to TCH. Typical range is 0.5% - 1%.  Immediate Assignment of TCH with “TCH as last option strategy” is recommended.  It is recommended to add SDCCH when 0.5 Erlang of signaling traffic is carried by TCH.  Half Rate penetration, usage of Extended Range cell and HSCSD should be taken into consideration. STS Approach:  Accurate dimensioning is achieved by using STS cell statistics

Limited Internal

8

NPI Training - Retainability

2005-09-30

SDCCH Congestion Optimization
Analyze the following issues that could be possible reasons for SDCCH Congestion:  SDCCH Dimensioning  Incorrect use of SDCCH capacity features such as Adaptive Configuration of Logical channels  TCH Congestion  Location Areas not optimized  SMS usage and Cell Broadcast channel  SDCCH Availability

Limited Internal

9

NPI Training - Retainability

2005-09-30...
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