Efficient transmission of integrated voice and data in wireless networks

Two categories of commercial wireless packet services exist today-a standalone system where the entire bandwidth is dedicated to the transmission of data packets (e.g. ARDIS, Mobitex), and an overlay system, where the unused channels of an existing cellular phone system are used (e.g. CDPD, GPRS). This paper examines the performance of the overlay service in a high density Manhattan street grid microcell. This type of cell is common in central urban areas. A simple analytical model is derived to describe the channel occupancy distribution in the microcell. The model is used to examine the performance of a connectionless data service operating over a cellular system. The two crucial performance criteria from a user's point of view are the packet latency and throughput. The model is firstly applied to a generic TDMA based data service to make some general observations about such a system. Then, the performance of CDPD in terms of the throughput and latency is evaluated under the two existing channel assignment schemes currently in use. A new assignment scheme is proposed, and is found to give a better performance with minimal changes to the CDPD specification.