| In this research, we examine the design and analysis of the media access control (MAC) layer protocols for broadband wired and wireless networking systems.; For wired networks, we focus on the hybrid fiber/coax (HFC) networks used in digital cable modem services under the Data Over Cable Service Interface Specifications (DOCSIS). The availability of high speed-access enables the delivery of high quality audio, video and interactive services. To support quality-of-service (QoS) for such applications, it is important for HFC networks to provide effective medium access and traffic scheduling mechanisms. We first develop a multilevel priority collision resolution scheme with adaptive contention window adjustment. The proposed scheme separates and resolves collisions for different classes of traffics, thus achieving the capability for preemptive priorities. Second, a novel scheduling mechanism and a new bandwidth allocation scheme are proposed to support multimedia traffic over DOCSIS-compliant cable networks. The primary goal is to improve the transmission of real-time variable bit rate (VBR) traffic in terms of throughput and delay.; For wireless networks, we consider the wireless local area networks (Wireless LANs) specified by the IEEE 802.11 standard. In wireless LANs, the CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) protocol supports asynchronous data transfer, and adopts an acknowledgment mechanism to confirm successful transmissions and a handshaking mechanism to reduce collisions. In both cases, a binary exponential backoff mechanism is used. An enhanced CSMA/CA protocol is presented in this research. The enhanced protocol improves the exponential backoff scheme by dynamically adjusting the contention window around the optimal value. Moreover, an analytical model based on the Markov chain is developed to analyze the system performance in terms of throughput and delay. Numerical results are presented to show the effect of the proposed backoff mechanism. |
