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Byline: Avraham Freedman (1), Amit Gil (2), Ran Giladi (3) Keywords: access protocols; channel allocation; limited availability; unbalanced availability; wireless access Abstract: Cellular wireless systems, such as mobile systems and fixed wireless access systems may encounter the problem of limited availability, where users of the system do not enjoy equal access opportunity to the systems' radio ports. The problem of limited availability was encountered in the early age of telephony but it has not yet been analyzed in the context of its impact on wireless system capacity. Two common scenarios where limited availability is encountered are discussed in this paper. One where there is an overlap in the coverage of two neighboring stations and the other where the coverage of one radio port is completely contained within that of the other. The paper analyzes two possible policies of radio port selection for the users who can access more than one port. One access policy is that of a completely random choice, while by the other the user selects only one of the free ports. The analysis demonstrates that system capacity may drop substantially if a proper balance is not maintained. Author Affiliation: (1) Department of Electrical Engineering-Systems, Tel-Aviv University, P.O. Box 39040, Ramat-Aviv, Tel Aviv, 69978, Israel (2) Celltick Technologies Ltd., 7 Hagalim Ave., P.O. Box 12878, Herzliya, 46733, Israel (3) Department of Communication Systems Engineering, Ben Gurion University of the Negev, Beer-Sheva, 84105, Israel Article History: Registration Date: 13/10/2004

Byline: Lixin Wang (1), Mounir Hamdi (2) Keywords: multiple access protocols; multimedia wireless networks; performance evaluation Abstract: This paper proposes a new medium access protocol (MAC) protocol for futurewireless multimedia personal communication systems, denoted hybrid andadaptive multiple access control (HAMAC) protocol. The HAMAC protocolintegrates fixed assignment TDMA protocol, reservation-based protocols, andcontention-based protocols into a single wireless network so as tosimultaneously and efficiently support various classes of traffic such asconstant-bit-rate (CBR), variable-bit-rate (VBR), and available-bit-rate (ABR)traffic. In particular, the HAMAC protocol uses a novel preservationslot technique to overcome the packet contention overhead in packetreservation multiple access (PRMA) like protocols, while keeping mostisochronous service features of TDMA protocols to serve voice and CBR trafficstreams. A preservation slot is a very short slot which is used torepresent a CBR connection when the traffic in the CBR connection is in asilent period in which there is no meaningful data to transmit. Due to thevery short length of the preservation slot, it only takes minimalportion of the bandwidth pre-allocated to the CBR connection, so that theremaining bandwidth can be freed for other connections to use. When the CBRsource becomes active again, the preservation slot is replaced bynormal data slots without any reservation operation, extra delay, orsignificant bandwidth loss. Consequently, the guaranteed service andsimplified signaling features of TDMA protocols, together with the adaptivebandwidth allocation features of PRMA-like protocols, are both realized in theHAMAC protocol. We have analyzed the performance of the HAMAC protocol usingextensive simulations. The results show that the HAMAC protocol can achievevery low loss rates for various multimedia traffic with stringent quality ofservice (QoS) requirements and outperforms state-of-the-art PRMA-likeprotocols. As a result, the HAMAC protocol appears to be a good candidate forfuture generation multimedia personal communication systems. Author Affiliation: (1) The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (2) The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong E-mail Article History: Registration Date: 24/09/2004

Byline: F. Arani (1), W. He (1), B. Honary (1) Keywords: Error control coding speech coding; combined source and channel coding. Abstract: A novel speech transmission technique over noisy channel condition based on combined ARS and channel coding schemes is described. The proposed scheme is suitable for time varying channels with some form of ARQ facilities. It is shown that under an AWGN channel condition, up to 3.8 dB gain relative to a conventional 32 kbits/s transmission can be provided using the combined technique. Author Affiliation: (1) Lancaster Communications Research Centre, Engineering Department, Lancaster University, Lancaster, LA1 4YR, UK Article History: Registration Date: 28/09/2004

Byline: N. Movahhedinia (1), G. Stamatelos (1), R.H.M. Hafez (1) Keywords: Wireless multimedia; ATM; bandwidth allocation; polling. Abstract: The rapid development of wireless in-building communication systems, has widened the scope of supported applications. Remote terminals may be capable of producing broadband real-time traffic such as variable bit-rate (VBR) video or bursty data transfers. Consequently one of the important issues in indoor broadband wireless networks (IBWN) is employment of an efficient bandwidth management protocol. In such a protocol, both the effects of radio channel behavior and the traffic heterogeneity have to be considered. In this paper we present a bandwidth allocation scheme based on the interplay of the radio channel characteristics and the traffic parameters and requirements. In the proposed scheme the base station visits the terminals in a non-uniform cyclic fashion. The inter-visit interval and the amount of service which is provided to each user during a visit, is determined using the channel and traffic parameters based on an analytical approach. This system is evaluated by simulations and is found to provide improved performance in fulfilling the requirements of multimedia services in IBWN. Author Affiliation: (1) Department of System and Computer Engineering, Carleton University, Ottawa, K1S 5B6 Article History: Registration Date: 28/09/2004