Efficient and robust multiple access control for wireless multimedia services

In this paper, we propose a new multiple access control (MAC) protocol for wireless distributed multimedia systems based on ATM, in which user demands are highly heterogeneous and can be classified as CBR, VBR, and ABR. Our protocol is motivated by two of the most significant drawbacks of existing protocols: (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 shadowing, which are inevitable in a mobile and wireless communication environment. A few protocols take into account the burst errors but just “handle” the errors in a passive manner. On the other hand, most of the existing protocols employ an inflexible or biased allocation algorithm such that 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 (synergistic channel adaptive multiple access), does not have these two 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 segregates a set of users with good CSI from requests gathered in the request contention phase of an uplink frame. The MAC protocol then judiciously allocates information time slots to the users according to their traffic types, CSI, urgency, and throughput, which are collectively represented by a novel and flexible priority function.