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INCREASING GSM NETWORK QUALITY OF SERVICE USING A SECOND ASSIGNMENT ATTEMPT TO ALTERNATIVE CARRIER

IP.com Disclosure Number: IPCOM000008296D
Original Publication Date: 1997-Sep-01
Included in the Prior Art Database: 2002-Jun-04
Document File: 1 page(s) / 63K

Publishing Venue

Motorola

Related People

Jonathan Hopkinson: AUTHOR

Abstract

During a standard GSM call setup process, a speech call is assigned from a SDCCH (signalling channel) to a TCH (traffic channel). If the TCH selected suffers from interference, then the assign- ment will fail. The call will then re-establish back on the SDCCH, and an Assignment Failure message will be sent to the MSC. The MSC will then typically release the call, causing the subscriber to experience a failed call setup.

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Technical Developments

INCREASING GSM NETWORK QUALITY OF SERVICE USING A SECOND ASSIGNMENT AlTEMPT TO ALTERNATIVE CARRIER

by Jonathan Hopkinson

BACKGROUND

  During a standard GSM call setup process, a speech call is assigned from a SDCCH (signalling channel) to a TCH (traffic channel). If the TCH selected suffers from interference, then the assign- ment will fail. The call will then re-establish back on the SDCCH, and an Assignment Failure message will be sent to the MSC. The MSC will then typically release the call, causing the subscriber to experience a failed call setup.

  The majority of GSM networks are now inter- ference limited-the service area of any given cell is constrained by the proximity of co-channel and adjacent channel carriers in other cells. Typically 2% of Assignment attempts fail for this reason- even more for moving mobile stations.

  By altering the operation of the system, it is possible to recover from some of these assignment failures, and thus reduce the call setup failure rate, and thereby increase the network quality of service.

RECOVERY PROCEDURE

  Standard operation requires that the BSC send an Assignment Failure message to the MSC if the MS fails assignment to a TCH and recovers to the

SDCCH. Normally the MSC then releases the call.

  However, by allowing the BSS to make a second assignment attempt autonomously, before sending the Assignment Failure message, the call setup may succeed. Selecting a TCH on an alterna- tive frequency (...