Variations on optimal and suboptimal handoff control for wireless communication systems

The design of handoff algorithms for cellular communication systems based o n signal-strength measurements is addressed. The system is modeled using a hybrid framework: a mixture of continuous state and discrete event systems. The handoff problem is formulated as an optimization problem to control th e switchings within the discrete event system, Performance is evaluated as a function of the expected number of handoffs, the expected handoff delay, and the expected number of signal degradations, A signal degradation occurs when the signal level falls below a threshold. The cost of handoff delay i s explicitly specified, in contrast to prior work, Various optimization pro blems are posed to trade off between these quantities. Based on the optimal solutions which are obtained through dynamic programming, suboptimal versi ons are proposed for ease of implementation. Performance of the suboptimal algorithm which trades off between the expected number of handoffs and the expected number of signal degradations is improved through the use of signa l averaging; however this algorithm suffers from excessive handoff delay, T herefore, the tradeoff between handoff delay and number of handoffs is cons idered, The corresponding suboptimal algorithm provides nearly one handoff and almost no delay, which is ideal if call quality is also good. Finally, an algorithm which is a combination of the two previous algorithms is explo red.