A new call admission control algorithm for IEEE 802.16 distributed mesh networks

The mesh distributed mode supported by IEEE 802.16 protocol, with the capability to establish direct links between SSs (Subscriber Station) and with the wide coverage area and the promised bit rate, allows to create interesting scenarios. The protocol defines guidelines to realize request/grant process, but it does not proposes a distributed Call Admission Control (CAC) algorithm. This process is essential to guarantee QoS constraints to admitted connections. In this paper, we present GCAD-CAC (Greedy Choice with bandwidth Availabilities aware Defragmentation): a new call admission control algorithm to guarantee the respect of data flows delay constraints defined by three different traffic classes. In order to reach good results, a Greedy algorithm is used: all the new requests are accepted, but when a higher priority request is received, a lower priority admitted request is preempted. The preemption can leave in data subframe some little gaps not sufficient to new connection admission; these gaps can be collected by GCAD algorithm by activating a bandwidth availabilities defragmentation process. The algorithm quality is proved by a comparison with other two algorithms found in the literature.