Energy-efficient high-speed packet access in WCDMA systems with smart packet dispatching: performance with TCP/IP based applications

This paper presents a performance analysis of high-speed downlink packet access (HSDPA) for TCP/IP applications in WCDMA systems with smart packet dispatching (SPD). The focus is on energy efficiency over burst-error correlated fading channels. The fading-channel characterization thereof is due to low user mobility of the primarily targeted environments for HSDPA applications. Using theoretical analysis and simulation, we show that in burst-error correlated fading channels adapting the time instant of scheduling/dispatching retransmission to fading-channel conditions: (i) significantly reduces the number of retransmissions; and (ii) helps closing the gap of bad channel states allowing the system to operate with much lower fade margin or transmit-power. It thus improves the efficiency of resource utilization in HSDPA. This method is referred to as SPD. In our modeling, we study the impact of fading based on fade duration statistics. The effects of diversity, mobility, and QoS constraints (such as timer for discarding out-of-date packets) are taken into account. The results are used to develop simple and energy-efficient adaptive SPD mechanisms.