The sub-rating channel assignment strategy for PCS hand-offs

A new personal communications services (PCS) hand-off scheme is proposed. This scheme provides for hand-off to radio ports on which there is no free channel by “sub-rating” an existing connection. With sub-rating, an occupied full-rate channel is temporarily divided into two half-rate channels: one to serve the existing call and the other to serve the hand-off request. The blocking probabilities (combined forced terminations of existing calls and blocking of new call attempts) of this new scheme compare favorably with the standard scheme (nonprioritizing) and the previously proposed prioritizing schemes. The costs for this scheme are presented and discussed, as well as the additional procedural complexity of implementing on-the-fly sub-rating and the impact of continuing the conversation on a lower rate channel (which may lower speech quality of increase battery drain). Analytical models and simulations investigating the traffic impacts are presented, as are the results that show that even in the highest offered load considered a 3-min conversation in the busy hour experiences less than half a second of sub-rated conversation on average and only about 3% of the calls experience more than 5.12 s of sub-rated conversation. This scheme can increase capacity by 8-35% for systems with 1% call incompletion probability