A Hybrid Adaptive Wireless Channel Access Protocol for MultimediaPersonal Communication Systems

Abstract

This paper proposes a new medium access protocol (MAC) protocol for future wireless multimedia personal communication systems, denoted hybrid and adaptive multiple access control (HAMAC) protocol. The HAMAC protocol integrates fixed assignment TDMA protocol, reservation-based protocols, and contention-based protocols into a single wireless network so as to simultaneously and efficiently support various classes of traffic such as constant-bit-rate (CBR), variable-bit-rate (VBR), and available-bit-rate (ABR) traffic. In particular, the HAMAC protocol uses a novel preservation slot technique to overcome the packet contention overhead in packet reservation multiple access (PRMA) like protocols, while keeping most isochronous service features of TDMA protocols to serve voice and CBR traffic streams. A preservation slot is a very short slot which is used to represent a CBR connection when the traffic in the CBR connection is in a silent period in which there is no meaningful data to transmit. Due to the very short length of the preservation slot, it only takes minimal portion of the bandwidth pre-allocated to the CBR connection, so that the remaining bandwidth can be freed for other connections to use. When the CBR source becomes active again, the preservation slot is replaced by normal data slots without any reservation operation, extra delay, or significant bandwidth loss. Consequently, the guaranteed service and simplified signaling features of TDMA protocols, together with the adaptive bandwidth allocation features of PRMA-like protocols, are both realized in the HAMAC protocol. We have analyzed the performance of the HAMAC protocol using extensive simulations. The results show that the HAMAC protocol can achieve very low loss rates for various multimedia traffic with stringent quality of service (QoS) requirements and outperforms state-of-the-art PRMA-like protocols. As a result, the HAMAC protocol appears to be a good candidate for future generation multimedia personal communication systems.