No relevant resource is found in the selected language.

This site uses cookies. By continuing to browse the site you are agreeing to our use of cookies. Read our privacy policy>

Reminder

To have a better experience, please upgrade your IE browser.

upgrade

Unidirectional inter-MSC handovers fail

Publication Date:  2018-04-11 Views:  99 Downloads:  0
Issue Description
In January 2015, Sagem 2 W handheld terminals used on a second-line vehicle failed to be handed over from the Lanzhou office to the Qinghai-Tibet office. However, SED handheld terminals and TEMS handheld terminals can be properly handed over between the two offices.

Additional information

Handling Process
The BSC serving the Qinghai-Tibet office responds to the handover failure, and the cause value is that the requested speech version is unavailable.

The supported speech version capabilities reported by terminals are as follows:

Sagem 2 W handheld terminals support both full-rate and half-rate speech versions, and the half-rate speech version has a higher priority.

SED 2 W handheld terminals also support both full-rate and half-rate speech versions, and the full-rate speech version has a higher priority.

Messages reported by a Sagem 2 W handheld terminal



Messages reported by a SED 2 W handheld terminal



The following table describes the speech version capabilities supported on the network side. 



When a terminal initiates an inter-MSC handover, it sends a Handover Required message to the local MSC to request a handover request. The local MSC selects a speech version from all the stored terminal speech versions based on their priorities and then sends it to the peer MSC. For the Sagem 2 W handheld terminal, the half-rate speech version has a higher priority. When this terminal is handed over from the Lanzhou office to the Qinghai-Tibet office, it requests for half-rate speech version 1. However, the network for the Qinghai-Tibet office supports only full-rate speech version 1, and it accordingly rejects the terminal request. As a result, the handover fail. 
Suggestions
Summary:
Sagem 2 W handheld terminals support both the full-rate speech version and half-rate speech version, but preferentially use the half-rate speech version. The speech version capabilities and priorities of terminals are stored on the MSC. The MSC for the Lanzhou office supports both the full-rate speech version and half-rate speech version. When a handheld terminal initiates an inter-MSC handover, the local MSC requests the half-rate speech version (higher priority) from the peer MSC, but the peer MSC supports only the full-rate speech version. In this situation, the requested speech version is unavailable, and the handover fails.

Preventive Measures and Suggestions:
  • If Sagem 2 W handheld terminals are used on GSM-R networks, it is recommended that the full-rate speech version be configured with a higher priority than the half-rate speech version.
  • The half-rate speech version supported by the MSC for the Lanzhou office is disabled, preventing problems caused by this speech version.

END