ENHANCED THROUGHPUT EFFICIENCY BY USE OF DYNAMICALLY VARIABLE REQUESTMINISLOTS IN MAC PROTOCOLS FOR HFC AND WIRELESS ACCESS NETWORKS

We consider Medium Access Control (MAC) protocols in which minislots a re used to request permission to transmit packets of information (voic e, data, video, or multi-media) in the upstream channels, and the info rmation is subsequently transmitted in packet time-slots allocated by a central controller. Such MAC protocols are currently being considere d for Hybrid Fiber-Coax (HFC) as well as wireless access networks. In this paper, we compare MAC protocols for three cases with regard to re quest minislots: (1) with no minislots tin this case, the first of a b atch of information packets from a station is transmitted in contentio n mode and also carries with it a reservation request for the remainde r of packets in that batch), (2) with fixed number of minislots per fr ame, and (3) with dynamically variable number of minislots per frame. There is transmission overhead associated with minislots, but there ar e potential throughput efficiency benefits under a range of traffic mi x scenarios. This paper also proposes an algorithm for dynamically var ying the number of minislots as a function of the traffic mix. Results based on analytical performance models are presented to compare throu ghput efficiencies for the three cases stated above. The results show that a MAC protocol with dynamically variable minislots has the highes t throughput efficiency amongst the different alternatives mentioned a bove.