ETSI EN 300 970-2000 数字蜂窝通信系统(第2+阶段).半速率语音.半速率语音业务流信道丢失帧的替代和静音.GSM 06.21(版本7.0.1,1998年发布)
Digital Cellular Telecommunications System (Phase 2+); Half Rate Speech; Substitution and Muting of Lost Frames for Half Rate Speech Traffic Channels (GSM 06.21 Version 8.0.1 Release 1999)