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Medium Access Control (MAC) plays a vital role in wireless networks. With the increasing popularity of multimedia services, MAC protocols of wireless networks are required to satisfy a variety of Quality of Service (QoS) requirements, including short delays. One of techniques for satisfying such requirements is based on assignment of transmission rights on demand. Following such a protocol, bandwidth is assigned to mobile terminals when they have something to transmit. The base station has absolute control of the bandwidth, including assignment of different priorities to different classes of users. In this thesis, we survey recently proposed MAC protocols for wireless networks. The survey includes MAC protocols designed for different network generations and topologies. Next, we focus on the demand part of demand assignment MAC protocols. We propose a new strategy based on probabilistic assignment that allows mobile terminals to pick the best time for transmitting their demands. Building upon this concept, we propose a new protocol called Transmission Probability Based Dynamic Slot Assignment or, briefly, TRAPDYS. It can be used in existing demand assignment protocols to improve their performance. The TRAPDYS protocol introduces a flexible prioritised access to communication channel by dynamically adjusting transmission rights of mobile terminals to current network traffic activities. We analyse the performance and behaviour of the TRAPDYS protocol be means of stochastic simulation. The results show that the TRAPDYS protocol is able to cope with a high level of traffic by utilizing temporarily unused network resources and improves the utilization of the demand part of network capacity used by a given demand assignment MAC protocol. |
