Logging Adaptive Multi-Rate (AMR)

Last updated: May 31, 2010

This section is only applicable to the lab applications.

You can use the Wireless Protocol Advisor (WPA) to observe and analyze messages and information related to AMR. This section contains some suggestions of how to modify the WPA view to make it easier to access certain fields.

WPA help is accessible from WPA by clicking the help button or for download at: http://www.keysight.com/find/e6584a

Verify a Codec Mode Change During a Call

For the manual operation procedure for setting up this test, see Change the Codec During a Call . In the Measurement Setup screen of the WPA, filter the Layer 1 Information protocol messages and set up a column that displays the Coding Scheme Used in the Traffic Overview screen. The Coding Scheme Used is found in the Layer 1 Information. Change the Current Codec (see General AMR Parameter Setup , steps 7-9). To verify that a mobile station can handle a change in the Codec Mode, run the WPA while a call is connected, and analyze the Coding Scheme Used and verify that the changes occurred. The column that displays the Coding Scheme Used allows you to quickly see any changes that occurred during the protocol log.

The figure below shows a protocol log while a call is connected.

Verify that the Mobile Station can pass the Stress Test

For the manual operation procedure for setting up this test, see Stress Testing with Frequent Changes of Codec Mode , There are several columns in the WPA that can be set up to prove that the mobile station is capable of being forced into different active codec modes during a call. While the same information could be viewed in the message decode, the columns make it easy to view the codec changes. In the Layer 1 Information protocol messages, the Codec Mode Command, Codec Mode Request, and Codec Mode Indication are sufficient to see the if the mobile station is responding properly. For more detailed information on the Codec Mode Command and Codec Mode Request columns, set up additional columns with corresponding interpretation. For example, if you would like more information on the Codec Mode Request, set up a column that displays Interpretation of Codec Mode Request under Layer 1 Information protocol.

The figure below shows a protocol log while a call is connected. The Codec Mode Command column verifies the test set is forcing the mobile station to a different codec mode on every third uplink.

View Codec Mode Requests from the Mobile Station

For the manual operation procedure for setting up this test, see Forcing Codec Mode Requests .

Be sure to set the Current Codec mode to MS Request for this test.

A quick way to verify in WPA that the mobile station is requesting and responding to messages from the test set is to set up the Codec Mode Request and the Coding Scheme Used columns. These messages are found in Layer 1 Information protocol. Once the column is set up, start the protocol log and change the downlink traffic power on the test set. After the protocol logging has stopped, analyze the columns to see if the Codec Mode Requests changed with the Coding Scheme Used.

The figure below shows a protocol log while a call from the mobile station was connected to the test set. The Current Codec was set to MS Request on the test set. The Codec Mode Request column verifies the mobile station generated requests to change codec modes while the downlink traffic power was changed on the test set.

Verify successful Handovers

For the manual operation procedure for setting up this test, see Handovers While an AMR Call is Active . To analyze handover parameters only, set the Test Set Message Filter in the WPA to filter only the GSM Layer 3 (GSM L3 ) protocol. When the GSM L3 message is an Assignment Command type, all handover parameters except the Logical Speech Channel can be checked and verified in the message decode, as shown in the figure below. Layer 1 messages that are AMR Frame Information type show theLogical Speech Channel type.

NOTE

If the test set is configured to only filter the Layer 3 messages, it must be reconfigured to filter the Layer 1 messages before they will appear in the Traffic Overview of the WPA..

Verify AMR parameter changes using RATSCCH

For the manual operation procedure for setting up this test, see Change Parameters using RATSCCH . The following are RATSCCH messages in the WPA: AMR Threshold Req, AMR Config Req, and AMR Ack. Setting up a Test Set Message Filter to only see RATSCCH protocol messages makes them much easier and quicker to locate. AMR Threshold Req messages display all the threshold and hysteresis values that are in the codec set. AMR Config Req shows the all the active codec modes that make up the codec set. The AMR Ack message acknowledges that the message has been sent.

For example, the message highlighted (in blue) in the figure below is an AMR Threshold Req message. The message decode for the highlighted message, shown in the lower portion of the figure, lists all the threshold and hysteresis values. Since the number of sets of threshold and hysteresis values is one less than the number of codecs in the set, it is clear there are only three codecs in the Active Codec Set (ACS) because there are two sets threshold and hysteresis values. The third set of threshold and hysteresis values is reserved for when there are four codecs in the ACS.

Verify the Usage of Discontinuous Transmission (DTX)

For the manual operation procedure for setting up this test, see Discontinuous Transmission (DTX) . It is possible to verify and monitor that the transmission and decoding of the many types of frames associated with DTX. View the message decode to see whether or not DTX was used. To see this without looking at each message decode, set up a column that displays DTX-USED. The DTX messages are found in GSM L3 protocol. This column will display if DTX was used or if DTX was not used. The figure below shows an example of a protocol log of a call established between the mobile station and the test set, with the DTX-USED column set up and a message decode view. The red arrow in the diagram shows where the message decode view lists if DTX was used or if DTX was not used.