QoS based scheduling for incorporating variable rate coded voice in Bluetooth

Bluetooth is an emerging standard low-cost indoor pico-cellular wireless systems. It is a master driven time division duplex (TDD) system. Real time services such as voice are given 64 kbps bandwidth in Bluetooth. However most other wireless networks use compressed voice, which requires much lesser bandwidth, leading to a substantial increase in system capacity. Bandwidth can be further conserved by using voice activity detection (VAD) techniques and variable rate voice codecs. We propose and analyse modifications to be made to Bluetooth for incorporating variable rate coded voice. Current mechanisms in Bluetooth use synchronous channels with fixed slot allocation for voice and a best effort service for data. We propose and study two scheduling strategies which optimise bandwidth consumption by using variable rate coded voice. In the first scheme, adaptive T_SCO scheduling, we modify the conventional scheduling policy to change the time period of scheduling a voice channel depending upon its activity. In the voice over ACL scheduling, we schedule voice asynchronously like data using a QoS based scheduling scheme with maximum scheduling delay tolerable by packets as the QoS parameter. This scheme can also be used to schedule other multimedia applications with varying QoS requirements. We observe from simulations that the voice over ACL scheme gives more than 115% increase in bandwidth over the currently used scheduling in the presence of two voice connections