Shared time division duplexing (STDD) with fast speech activity detection

Abstract

Motivated by a desire to provide low delay, high quality digital speech communications in a high capacity wireless network, an access method was introduced to achieve these requirements. Such wireless systems are primarily targeted for indoor environments, as well as outdoor microcell environments. We concentrate our efforts on time division multiple access (TDMA) systems with time division duplexing (TDD). Shared time division duplexing (STDD), provides a considerable increase in capacity over the conventional time division systems with speech activity detection (SAD) even with a moderate number of users per carrier. The key idea in STDD is sharing time slots in both directions of transmission. Fast speech activity detection (FSAD) is considered. We obtain a novel model that describes (FSAD) speech for a pair of users, by merging two existing models, one for (slow) SAD on-off speech for a pair of users, and one describing FSAD speech of a single user. It is concluded, based on this model, that the use of FSAD results in an increase of approximately 20% in capacity over systems with slow speech activity detection, as well as in much shorter runlengths of dropped packets. Numerical results are included for a short frame length of 2 ms.