Enhanced throughput efficiency by use of dynamically variable request minislots in MAC protocols for HFC and wireless access networks

Abstract

We consider Medium Access Control (MAC) protocols in which minislots are used to request permission to transmit packets of information (voice, data, video, or multi?media) in the upstream channels, and the information is subsequently transmitted in packet time?slots allocated by a central controller. Such MAC protocols are currently being considered for Hybrid Fiber?Coax (HFC) as well as wireless access networks. In this paper, we compare MAC protocols for three cases with regard to request minislots: (1) with no minislots (in this case, the first of a batch of information packets from a station is transmitted in contention mode and also carries with it a reservation request for the remainder of packets in that batch), (2) with fixed number of minislots per frame, and (3) with dynamically variable number of minislots per frame. There is transmission overhead associated with minislots, but there are potential throughput efficiency benefits under a range of traffic mix scenarios. This paper also proposes an algorithm for dynamically varying the number of minislots as a function of the traffic mix. Results based on analytical performance models are presented to compare throughput efficiencies for the three cases stated above. The results show that a MAC protocol with dynamically variable minislots has the highest throughput efficiency amongst the different alternatives mentioned above.