Access Delay Analysis in Reservation Multiple Access Protocols for Broadband Local and Cellular Network Ahmed Doha Telecommunications Research Lab Electrical and Computer Engineering Department Queen’s University doha@ee.queensu.ca Hossam Hassanein Telecommunications Research Lab School of Computing Queen’s University hossam@cs.queensu.ca Abstract This paper analyzes reservation request access delay in reservation multiple access protocols in light of frame’s contention slot allocation. Variations of reservation MAC protocol is widely used in local and cellular network technologies. We derive an analytical model for access delay of reservation request packets that reflects the impact of per-frame number of contention slots on access delay of a request packet. We obtain insightful observations on this relation and as a result show that a new family of delay and throughput constrained dynamic contention slot allocation schemes can be developed. Keywords: Broadband local and cellular access networks, Reservation MAC, contention slot allocation 1. Introduction Reservation multiple access MAC protocols are widely used in Multiple Access MAC layer of broadband local and cellular access technologies. The MAC protocol organizes users’ access to limited bandwidth BW Resources. In most of the reservation based MAC protocols, time is organized into frames. A frame comprises an uplink subframe (from subscribers to BS) and a downlink subframe (from BS to subscribers). The downlink is used solely by the BS to send a stream of Time Division Multiplex TDM signal to Subscriber Stations SS’s whereas the uplink is shared by all SS’s to send their data to the Base Station. The transmission of both portions may be time-separated on the same frequency band in a Time Division Duplex TDD fashion or simultaneous in time on separate frequency bands in a Frequency Division Duplex FDD fashion. In a centralized manner, media access and BW assignment to subscriber stations SS’s are controlled by the head end controller HC (i.e. Base Station BS as well call it throughout this work). Upon traffic generation, an SS must first send a BW reservation request packet, through contention, to the BS. The BW request packet indicates to the BS the amount of BW a user needs. Ultimately, when the BS receives a BW request, it allocates – on the uplink – an equal amount of BW to the user’s request. However, the schedule of BW allocation, which is not necessarily contiguous, is chosen at the BS’s own discretion. The diverse priorities of traffic and users that are already in the system and also available BW resources are the main factors that shape the BS’s chosen allocation schedule. The uplink subframe is made in the most part of contention and data slots. Besides, control and management slots occupy relatively minor portion of the uplink subframe. Since the amount of offered traffic normally exceeds the system’s time-unit BW, BW-related delays are inescapable. In reservation MAC protocols, BW- related delays consist of contention-related and BW allocation schedule-related delays. The notion of BW allocation schedule-related delay is entwined with available data slots in a frame. Since frame size is fixed, simultaneously minimizing both types of delays is a paradox, though highly desired. An efficient reservation MAC protocol ought to have provisions to competently approach this objective. There have been several proposals of reservation MAC protocols. The most popular choice of a multiple access protocol for local access (wired or wireless) and cellular systems [3] supporting voice and data traffic is Reservation ALOHA protocol R-ALOHA [18]. Variations of R-ALOHA protocol are adopted in local and cellular networks. The organization of the MAC frame’s time slots into contention slots CS’s and data slots DS’s vary from one protocol to another. In R-ALOHA protocol, proposed by Crowther et al. [18], the media is organized into time frames. A frame is divided into a fixed size contention period and a fixed Proceedings of the 29th Annual IEEE International Conference on Local Computer Networks (LCN’04) 0742-1303/04 $ 20.00 IEEE