Capacity Increase in GSM Networks Using Source-Adaptive AMR

Adaptive multi rate (AMR) is a variable-rate speech codec, which was introduced in GSM specifications to improve speech quality and transmission robustness. Based on existing AMR codecs, source-adaptive AMR is a new proposal to improve system capacity in GSM and WCDMA networks. In GSM, by decreasing the codec bit rate we can reach a more robust transmission, due to the increased redundancy available. Because some speech periods have low entropy, they can be encoded with lower bit rate with no noticeable loss in speech quality. This implies a robustness gain, which can be used to increase system capacity. In this paper we investigate the potential capacity increase that can be obtained in GSM networks using this technique