| Wireless ATM networks have been studied extensively in recent years because it has the advantage of offering end-to-end multimedia capabilities with guaranteed quality of service (QoS). The multiple access protocol is one of the critical technologies of the wireless ATM. Only by adopting the efficient multiple access protocols, can the frequency be used fairly and reasonably, so that to increase the system capacity.In this paper, firstly, a brief survey of the development network structure . critical technologies and research activities of the wireless ATM are presented; Secondly, the mathematical modeling of the heterogeneous traffic(such as, CBR VBR ABR and UBR) and discrete event system simulation which is used in this paper are discussed; Thirdly, the importance of the multiple access protocol and all kinds of multiple access protocols which are proposed for wireless ATM are analyzed and studied; Finally, a multiple access protocol that is PRMA++ is improved and developed. The orthogonal code is used for reservation slot, hence, the packet collisions are prevented while several packets apply for reservation slot simultaneously. In addition, due to bandwidth limitation, the dynamic slot allocation algorithm(DSAA) with bound variable for burst traffic is also proposed in this paper, so that the QoS of multimedia traffics are guaranteed in wireless ATM networks well.The performance of PRMA++ protocol in which orthogonal code and DSAA are used by using computer simulation based on above viewpoint. From the analysis and simulation results, I know that the slot utilization in improved system is higher than that of the other well-know integrated services multiple access(e. g. , PRMA PRMA++). Furthermore) the performances of burst traffics outperform the case without dynamic slot allocation. In addition, the improved PRMA++ protocol prevents cell collisions and increases the channel efficiency, moreover, the more statistical multiplexing gains are got for VBR voice and VBR video traffic and voice capacity increases too. Therefore, the improved PRMA++ protocol is a good algorithm and can meets the QoS requirements for VBR voice, VBR video and UBR data traffics well in wireless ATM networks; meanwhile the improved PRMA++ protocol is a competitive candidate to be adopted in the wireless ATM networks. |
