Benefits of queued handoff in a multi-tier architecture

In multi-tier cellular networks a set of contiguous microcells are overlayed with a macrocell. Such architectures provide a higher system capacity because of the small frequency reuse distance of the microcell layer. However, handoff control is a key issue in such architectures; decrease in the cell dwelling time causes higher number of handoffs and hence higher handoff blocking probability. Queueing handoff calls when there are no idle channels, in the target cell, can improve handoff blocking probability without significantly increasing the new call blocking probability. We first present an analytical model to study the performance of a single-tier cellular network with two types of users, namely, high-speed users and low-speed users. We then use this model to analyze a multi-tier network with a queue in only one tier. Finally, we use a simulation model to examine the multi-tier network with different queue strategies. Our results show that by using a priority queue in the multi-tier network, the blocking probability of handoff calls can be significantly improved at the same time supporting a large system load