Performance of simple priority schemes for the RRA-ISA multiple access protocol in packet voice and data cellular systems
Raffaele Bolla, Franco Davoli, Carlo Nobile · 2002
A multiple access protocol based on a reservation random access (RRA) scheme is derived, together with three of its variants, and their performance is evaluated and compared by simulation with that of another protocol operating within the same environment. Given a TDMA framed channel and a cellular structure, the aim of the protocol is that of maximizing the one-step throughput over on entire frame. This is achieved by deciding on the access rights at the base station, which then broadcasts this information at the beginning of the frame. The resulting protocol is termed the independent stations algorithm (ISA), and the overall scheme the RRA-ISA. As in other RRA protocols, time constrained (e.g., voice) traffic operates in a dynamic reservation mode, by contending for a slot in the frame with the first packet of a burst, and then keeping the eventually accessed slot for the duration of the burst; packets of the time constrained traffic unable to access a slot within a maximum delay are dropped from the input buffer. No such constraint is imposed on data traffic. The three different variants which are presented. This improvement is achieved by applying three different priority schemes which give a prominence to the service of the voice traffic. The different schemes are analysed by simulation in the presence of voice and data traffic. Several comparisons show a relevant performance improvement (in terms of data delay and maximum number of voice stations acceptable within a cell) of ISA schemes over other protocols that use ALOHA as a reservation mechanism.