Load threshold for connection state scheme supporting packet data service in wireless networks

In provisioning packet data service on wireless cellular networks, a scheme of altering connection status between mobile and base stations appeared intending to efficiently utilize resource during idle periods. In such a scheme, connection components are sequentially released as an idle period persists, while a transmission activity is resumed as a prescribed amount of traffic load is accumulated at the transmitting station. Before a transmission resume, however, latency depending on previous idle period is unavoidable to retrieve the lost connection components, which also produces a chain reaction in forthcoming idle period and connection retrieval time. An issue arising in design of the scheme is to determine a threshold value for load accumulation in conjunction with packet delay properties. A high threshold apparently incurs along stand-by to gather the prescribed traffic load before resuming transmission. On the other hand, such high threshold may shorten the length of upcoming idle period and reduce the consequent connection retrieval time by suppressing the release of connection components. In this paper, we thus investigate the antithetical effects of load threshold on packet delay performance. First, we generalize the connection retrieval time in consideration of the number of states and maximum sojourn times. Secondly, for general packet arrivals, we estimate average length of idle period and mean packet delay. In addition, we present an approximation method to calculate the moments of packet delay time for Poisson arrivals. Finally, we construct and solve a problem to find an optimal value for load threshold minimizing mean packet delay. From numerical examples, we find non-trivial optimal thresholds in the environments characterized by relatively long connection retrieval time and heavy traffic load.