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AMR Conformance Testing in GSM Devices

amr gsm conformance testing mobile communication

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.