Service and system enhancements for TDMA digital cellular systems

Throughout 1998, the TDMA community investigated and defined an enhanced su ite of voice and data services for TIA/EIA-136 while also improving its bas ic system capabilities. These enhancements, collectively named 136+, provid e improved voice quality, increased capacity, higher data rates, and improv ed tools for RF system engineering. The enhancements are obtained by introd ucing a new modulation scheme (8-PSK), new slot formals, and the addition o f several new interleaving and coding options. As a result, TIA/EIA-136 now supports a new vocoder mode, the GSM Enhanced Full-Rate (US1) for improved fidelity applications, a robust IS-641 vocoder mode with a 4 dB FER enhanc ement on the IS136 downlink, and a new packet data service capable of provi ding usable data rates of 14.4, 28.8, or 43.2 kb/s on a full-rate, double f ull-rate, or triple full-rate channel, respectively. The packet data servic e is truly evolutionary in nature, having a new medium access control layer with a network layer very similar to that used for the existing digital co ntrol channel. In addition, it maximizes commonalities among TDMA technolog ies, using identical higher layers and network architecture to the General Packet Radio Service specified in GSM. furthermore, by using a concept know n as tunneling to pass TIA/EIA-136 messages through the GPRS network elemen ts, the existing features defined on the DCCH are maintained. This article provides an overview of these 136+-applications, as well as insight into ad ditional near-term improvements, such as the ability to support six voice u sers per 30 kHz (TDMA6), downlink time diversity, and fast power control.