Group voice conferencing for mobile environments

We present the design and the implementation details of a group conferencing tool using only 50% of the bandwidth of a 9.6 kbit/s GSM connection, thus leaving resources for other applications that need to access network resources concurrently. The system architecture with its conferencing server and the clients is described as well as the QoS issues that were crucial during the design of the application. The used protocols and voice codecs are presented and performance constraints and measured results from the actual implementation into a virtual tourist guide are described