Efficient and Robust Multiple Access COntrol for Wireless Multimedia Services

摘要

In this paper, we propose a new multiple access control (MAC) protocol for wireless distributed multimedia systems based on ATM, in whic user demands are highly heteroge-lneous and can be classified as CBR, VBR, and ABR. Our protocol is motivated by two of the most significant draw-backs of existing prootcols: (1) channel condition is ignored or not exploited, and (2) inflexible or biased time slots allocation algorithms are used. Indeed, existing protocols mostly ignore the burst errors due to fading and shadow-ing, which are inevitable in a mobile and wireless communication environemtn. A few protocols take into account the butst errors but just "handle" the errors in a passive nanner. Ont he tothe rhand, most of the existing protocols employ an inflexible or biased allocation algorithm such athat over-provisioning may occur for a certain class of users at the expense of the poor service quality received by other users. Our proposed protocol, called SCAMA (synergis-tic channel adaptive multiple access), does not have these teo drawbacks. The proposed protocol works closely with the underlying physical layer in that through observing the channel state information (CSI) of each mobile user, the MAC protocol first esegregates a set of users with good CSI from requests gathered in the requrest contention phase of an uplink frame. The MAC protocol then judiciously allocates information time slots to the users according to their traffic tyeps, CSI, urgency, and throughput, which are collectively represented by anovel and flexible priority function.