Foundations of Mobile Radio Engineering
Foundations of Mobile Radio Engineering
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As tetherless multimedia computing environments are becoming much desired, broadband wireless communication infrastructures for providing wireless multimedia services will play an important role, and thus, are expected to proliferate. However, despite much research efforts have been expended, the multiple access control of the precious bandwidth remains a challenging problem because of the existence of two common drawbacks in the state-of-the-art 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. 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. In this paper, a new MAC protocol, called SCAMA (synergistic channel adaptive multiple access) is proposed. 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 the respective traffic types, CSI, urgency, and throughput, which are collectively represented by a novel and flexible priority function. Despite that contention request queue is not used in the protocol, the SCAMA protocol is robust in that it can avoid the congestion collapse which occur in other protocols.