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Overview The AMR selects an appropriate coding/decoding rate automatically so that the antiinterference capability of the wireless communication system is enhanced and the speech quality is improved.

Definition AMR is an adaptive multi-rate speech coding/decoding algorithm, which is termed full-rate speech version 3 and half-rate speech version 3 in protocols. The algorithm enables a BTS and an MS to select an appropriate coding/decoding rate automatically in the specified rate collection based on the interference conditions of the radio environment so that the antiinterference capability and the speech quality of the wireless communication system can be enhanced. AMR is applicable to the speech services in the wireless communication system and is not applicable to the CS data services or PS services.

Purposes In the wireless communication system, if the speech coding rate involved in channel coding is high, the quantity of the speech feature information carried in the coded code stream is large and the speech fidelity is high. At the same time, the quantity of redundant information in the code stream is small and the anti-interference capability of the code stream is poor. In a poor wireless communication environment, bit errors occur easily and the speech frames may be lost thereby. Thus, voices may be intermittent. If the rate of the speech coding involved in channel coding decreases, the coded code stream can contain much redundant information. Then the code stream has strong anti-interference and error correction capabilities. Thus the continuity of voice can be improved. The AMR enables a BTS and an MS to obtain the interference status of the radio environment based on the receive level, receive quality, and carrier-to-interference ratio so that the rate of the speech coding can be adaptively adjusted. Thus, the anti-interference capability of the wireless communication system can be enhanced and the speech quality can be improved.

AMR Calls The AMR is involved in the following call procedures: the incoming BSC handover procedure, the outgoing BSC handover procedure, and the intra-BSC handover procedure. The call procedures are achieved based on the contents described in References. 2016-01-06

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Assignment Procedure The assignment procedure is described as follows: 1.

The MSC determines whether an MS supports AMR based on the support capability of the MS, the service type of a call, the speech version supported by the MSC, and the circuit pool where the circuit on the A interface is located.

2.

The MSC determines a set of speech versions that are supported by the call and sends the information on the set to the BSC through an Assignment Request message.

3.

After receiving the Assignment Request message from the MSC, the BSC determines whether AMR can be used based on whether the license allows the BSC to use AMR and whether the A interface tag is PHASE 2+.

4.

Based on the intersection of the set of supported speech versions carried in the Assignment Request message and the speech versions supported by the cell, the BSC can obtain the candidate speech versions.

5.

Based on the candidate speech versions and the types of the assigned channels, the BSC selects a speech version whose level is the highest for final use.

6.

If an AMR speech version is selected, the BSC sends the AMR service parameters to the BTS through a Channel Activation message or a Mode Modify command. Then, the BSC sends the AMR service parameters to an MS through an assignment command or a Channel Mode Modify command. After the MS is accessed, the MS reports an Assignment Complete message to the MSC. The assignment procedure for an AMR call is complete.

Incoming BSC Handover Procedure The incoming BSC handover procedure is described as follows: 1.

The MSC determines whether an MS supports AMR based on the support capability of the MS, the service type of a call, the speech version supported by the MSC, and the circuit pool where the circuit on the A interface is located.

2.

The MSC determines a set of speech versions that are supported by the call and sends the information on the set of speech versions to the BSC through an incoming BSC handover request message.

3.

After receiving the handover request from the MSC, the BSC obtains the candidate speech versions based on the intersection of the set of supported speech versions carried in a handover request and the speech versions supported by a cell.

4.

Based on the candidate speech versions and the types of the assigned channels, the BSC selects a speech version whose level is the highest for final use.

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If an AMR speech version is selected, the BSC sends the AMR service parameters to the BTS through a Channel Activation message. After receiving a Channel Activation Acknowledge message from the BTS, the BSC send a Handover Request Acknowledge message to the MSC and then sends the AMR service parameters to an MS through a handover command.

Outgoing BSC Handover Procedure In the outgoing BSC handover procedure, the BSC determines to initialize an outgoing BSC handover based on the handover decision algorithm and sends a Handover Required message to the MSC. The message contains the speech version used by the current call.

Intra-BSC Handover Procedure In the intra-BSC handover procedure, the BSC determines to initialize an intra-BSC handover based on the BSC handover decision algorithm. According to the saved assignment requests or the set of the supported speech versions carried in an incoming BSC handover request, a method is used to determine the speech version for final use. The method is the same as that is used in the assignment procedure. When a call is an AMR call, the BSC sends the AMR service parameters to the BTS through a Channel Activation message, and then sends these parameters to an MS through a handover command.

Determination of the AMR Speech Version Figure 1 shows the procedure for determining the AMR speech version. Figure 1 Procedure for determining the AMR speech version

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Configuring AMR Configure the AMR through the BSC6000 Local Maintenance Terminal.

Context

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For Huawei MSCs, the current BSC is configured as supporting full-rate speech version 3 and half-rate speech version 3 or is configured as supporting any one of these two versions. For the specific operation, refer to the user manuals related to the MSC products.

Procedure 1.

Apply for and activate the license a.

When the license used for half-rate service is applied, you should ensure that in the BSC6000V900R001 (None) Commercial License Application Template, the Number of resources corresponding to the Number of the TRX supporting AMR in the Resource control items column is not 0. You should fill in the actual number of TRXs that has the AMR function.

b.

On the BSC6000 Local Maintenance Terminal, activate the license. For details, refer to Activating License.

2.

Configure the A interface tag as GSM_PHASE_2+. a.

On the BSC6000 Local Maintenance Terminal, right-click the BSC6000 node on the Management Tree tab page. Choose Configure BSC Attributes from the shortcut menu. A dialog box is displayed, as shown in Figure 1. Figure 1 Configuring A interface tag of the BSC

b.

Select Basic Data tab, on the tab page, set the Value of the A Interface Tag to GSM_PHASE_2+.

3.

Set the configuration of the speech version in a cell as supporting full-rate speech version 3 or half-rate speech version 3.

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On the BSC6000 Local Maintenance Terminal, select a cell on the Management Tree tab page, and then right-click it. Choose Configure Cells Attributes from the shortcut menu. A dialog box is displayed, as shown in Figure 2. Figure 2 Configuring Cells Attributes dialog box

b.

Double-click a corresponding cell in the Cell view area, and then add it to the list of the Selected cells.

c.

Click Next. A dialog box is displayed, as shown in Figure 3. Figure 3 Configuring Cells Attributes dialog box

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Click Configure Cells Attributes. A dialog box is displayed, as shown in Figure 4. Figure 4 Set Cells Attributes dialog box

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Click Call Control. A dialog box is displayed, as shown in Figure 5. Figure 5 Setting call control parameters

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Click Advanced. A dialog box is displayed, as shown in Figure 6. Figure 6 Set Call Control Parameter[Cell: 3002E] dialog box

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On the Access Control tab page, modify the value of Speech Version as Support Full-rate Version 3. If the cell supports the half-rate service, select Support Half-rate Version 3 at the same time.

4.

Configure the AMR call processing parameters a.

As shown in Figure 6, select AMR Call Control tab. On the tab page, configure the AMR call processing parameters applied to the full-rate and halfrate channels, as shown in Figure 7 and Figure 8. Figure 7 Configuring AMR full-rate call processing parameters in a cell

Figure 8 Configuring AMR half-rate call processing parameters in a cell

NOTE: AMR ACS (F) in Figure 7 and AMR ACS (H) in Figure 8 can select four types of 2016-01-06

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coding rate at most and one coding rate at least separately. 5.

Configure the full handover and half handover parameters in an AMR cell. a.

As shown in Figure 4, click Handover Data. A dialog box is displayed, as shown in Figure 9. In the Parameter Name area, set the Value for Intracell HO Allowed and Inttracell F-H HO Allowed. Figure 9 Configuring full handover and half handover control parameters in an AMR cell (1)

b.

Pull down the scroll bar shown in Figure 9, as shown in Figure 10. In the Parameter Name area, set Value for Intracell F-H HO Stat Time(s), Intracell F-H HO Last Time(s), F2H HO th, and H2F HO th. Figure 10 Configuring full handover and half handover control parameters in an AMR cell (2)

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Configure the AMR power control parameters in a cell a.

As shown in Figure 4, click Power Control. A dialog box is displayed, as shown in Figure 11. Figure 11 Setting power control parameters

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Click Advanced. A dialog box is displayed, as shown in Figure 12. Figure 12 Configuring AMR power control parameters in a cell

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Select AMR Power Control tab. On the tab page, configure the parameters shown in AMR Power Control.

7.

Configure the AMR channel management parameters in a cell a.

As shown in Figure 4, click Channel Management. A dialog box is displayed, as shown in Figure 13. Figure 13 Setting channel management parameters

b.

Click Advanced. A dialog box is displayed, as shown in Figure 14. Figure 14 Configuring AMR channel management parameters in a cell

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Select HWII Channel Assignment and Radio Channel Control tab. On the tab page, configure AMR TCH/H Prior Allowed and AMR TCH/H Prior Cell Load Threshold.

8.

If the site used currently supports the AMR, but the BTS software does not support the AMR, based on the description of software versions in Table 1, the BTS software version that supports the AMR features is obtained. Then, apply the obtained version to the BTS. Otherwise, the AMR fails to be configured.

Example Enable the AMR function in the cells where the BTS3X supports the half-rate service. A maximum of 100 TRXs that supports AMR features are supported in the license. The AMR parameters are configured as follows: 

Ensure that the software version used in the BTS3X is G3BTS32V302R002C06SP02 and later releases



Configure full-rate speech coding algorithm 3 and half-rate speech coding algorithm 3 that are supported by the MSC



Activate the license that supports the AMR function



Configure the A interface tag as GSM_PHASE_2+, as shown in Figure 1.



Configure full-rate speech version 3 and half-rate speech version 3 that are supported by a cell, as shown in Figure 6



Use the default value to configure the AMR call processing parameters in a cell, as shown in Figure 7 and Figure 8

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Use the default value to configure the full handover and half handover parameters in an AMR cell, as shown in Figure 9 and Figure 10

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Configure full-rate speech version 3 and half-rate speech version 3 that are supported by a cell, as shown in Figure 6



Use the default value to configure the AMR power control parameters in a cell, as shown in Figure 12



Use the default value to configure the AMR channel management parameters in a cell, as shown in Figure 4. The configuration is complete.

Verifying AMR You can ensure that whether a call uses the AMR by verifying the AMR through the BSC6000 Local Maintenance Terminal.

Prerequisites 

The BSC6000 Local Maintenance Terminal is started normally.



The communication between the BSC and the BTS is normal.

Procedure 1.

On the BSC6000 Local Maintenance Terminal, choose Trace & Monitor tab on the Management Tree tab page. Then, choose Trace > Trace User Message. Doubleclick it. A dialog box is displayed, as shown in Figure 1. Figure 1 Trace User Message dialog box

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Set parameters in the Interface Type, Tracing Mode, and Color areas. Select and fill in the IMSI, TMSI, MSISDN, IMEI, or Channel of the user to be traced. Click OK to start tracing. The result is displayed, as shown in Figure 2. Figure 2 Tracing Single user message

3.

Select the area where the CHANNEL ACTIVATION (CHANNEL ACTIVATION are displayed in two places in the dialog box. You need select the one near the ASSIGNMENT COMPLETE.) exists, and then double-click the area. A dialog box is displayed, as shown in Figure 3.

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Figure 3 Displayed result



If the value of the speech-coding-algor is gsm-speech-coding-algorithmversion(3), the AMR is used.



Otherwise, the AMR is not used.

Capabilities The AMR capabilities consist of the functions that AMR supports and the limitations on AMR. The AMR supports the following functions:  The AMR speech coding/decoding function can be performed on a full-rate channel. There are eight types of speech rates:

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12.2 kbit/s (GSM EFR)

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10.2 kbit/s

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7.95 kbit/s

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7.40 kbit/s (IS-641)

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6.70 kbit/s

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5.90 kbit/s

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5.15 kbit/s

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The coding rate can be adjusted based on C/I and the AMR speech coding/decoding on a full-rate channel can be adjusted in the Active Coding Set (ACS).  The AMR speech coding/decoding function can be performed on a half-rate channel. There are five types of speech rates: 

7.40 kbit/s (IS-641)

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6.70 kbit/s

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5.90 kbit/s

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5.15 kbit/s

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4.75 kbit/s

The coding rate can be adjusted based on C/I and the AMR speech coding/decoding on a half-rate channel can be adjusted in the Active Coding Set (ACS).  The AMR supports the quality-based HR-FR intra-cell handover.  The AMR calls and non-AMR calls use different power control strategies.  The AMR service can be enabled or disabled at the cell level.  Different ACSs, coding rate adjustment thresholds and hysteresis, and initial coding rates can be set at the cell level.  The AMR supports the dynamic configuration of AMR functions, ACS, coding rate adjustment threshold and hysteresis, and initial coding rate. The limitations on the AMR are as follows:  The AMR supports the change in ACS during the handover. The AMR does not support the change in ACS during the maintenance of channels.  The AMR does not support the TFO, RATSCCH, or pre-handover.  The half-rate AMR service does not support the coding rate of 7.95 kbit/s. NOTE: The fixed-rate bandwidth (8 kbit/s) is used for transmission on the Abis interface in GBSS half-rate mode and the bandwidth cannot bear the speech coding information transmitted at a rate of 7.95 kbit/s. Therefore, the half-rate AMR service does not support the coding rate of 7.95 kbit/s. In half-rate AMR service mode, only five types of coding rates are supported.

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