AMR Conformance Testing in GSM Devices

The following are the AMR conformance test specifications used to test AMR features in GSM-compliant devices.

Loopback I: AMR Speech Channels

• The System Simulator (SS) is expected to transmit a valid Downlink (DL) signal, which includes speech frames channel-encoded as per CMI/DL.
• The Mobile Station (MS) continuously transmits in the Uplink (UL) the in-band bits decoded in the DL. Decoded CMI/DL shall be looped as CMR/UL. Decoded CMC/DL shall be looped as CMI/UL.
• A default (ODD) transmission phase for CMI/CMC is assumed once in a loop.
• The MS always uses the codec mode resulting from the received CMC for channel encoding.
• It uses a fixed pattern of alternating 0 and 1, with the first bit being 1 (0x55 used in Hassium) and with TX_TYPE = SPEECH_GOOD.
• The RATSCCH protocol is deactivated during loop I. There’s no need to interpret the content of the DL RATSCCH message, and no need to send RATSCCH_ACK.
• Loop I is only required to operate when DL DTX (Discontinuous Transmission) is NOT used. When SID_FIRST/SID_FIRST_P1/SID_FIRST_P2/SID_FIRST_INH/SID_UPDATE/SID_UPDATE_INH/ONSET is detected, there is no need for in-band signaling loopback.
• Loop I is not designed to measure the performance of in-band signaling over SID_UPDATE or RATSCCH messages.
• If FACCH (Fast Associated Control Channel) is detected, the MS sends an all-0 pattern using the same codec mode as the previous UL frame. CMI/UL = uplink codec mode in use. CMR/UL = previous UL CMR.

AMR (TCH/AFS & TCH/AHS) Testing Conformance Tests

The following conformance tests are performed on AMR (Adaptive Multi-Rate) implementations:

• Bad frames Indication (14.1.5, 14.1.6)
• Reference Sensitivity (14.2.10, 14.2.18)
• Co-channel Rejection (14.4.8, 14.4.16)
• Inband decoding performances (14.2.19, 14.2.20, 14.4.17, 14.4.18)
• Adjacent Channel Rejection (14.5.1)
• CMR computation performances (14.10.1, 14.10.2, 14.10.3, 14.10.4)
• DARP Phase-I (14.11.2, 14.11.3)
• DARP Phase-II (14.19.2, 14.19.3)
• Received signal measurements (with and without DTX) (21.3.3, 21.3.4, 21.3.5, 21.3.6, 21.4.2, 21.4.3)
• 26.16.x -> AMR signalling: AMR assignment, inband, ratscch, AMR HO

Companies like Alcatel, Ericsson, Motorola, Nortel, Nokia, and Siemens have facilities to test AMR features in their respective IOT (Internet of Things) labs.