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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.comnet.2008.10.005 Byline: Peng-Yong Kong, Inn-Inn Er Keywords: IEEE 802.16; Mesh network; Time-spread multiple access; Topology-transparent scheduling Abstract: This paper studies the use of IEEE 802.16d mesh MAC protocol for multi-hop networking in an indoor domestic environment. The mesh network is expected to support time-sensitive audio-video applications with stringent QoS requirement. In the literature, time-spread multiple access (TSMA) is a promising technology to provide a minimum throughput guarantee in a multi-hop mesh network with dynamic topology. However, existing TSMA schemes require the number of nodes in the entire network and their global maximum node degree, be known a priori to a central controller. The requirement is not practical. In view of this problem, this paper proposes a distributed time-spread multiple access (DTSMA) scheme. The proposed DTSMA has the following main contributions: (a) A method for each node to determine locally its polynomial coefficients without a priori global knowledge of node number and maximum node degree, and (b) A method to distribute to neighbours the locally determined polynomial coefficients, and to resolve collision between two sets of identical polynomial coefficients from two neighbouring nodes. The proposed DTSMA has been evaluated through extensive simulations to confirm that it can indeed preserve the capability of providing a minimum throughput guarantee in the absence of the a priori global knowledge. In benchmark against the de facto distributed coordinated scheduling (DCS) in the original IEEE 802.16d mesh MAC protocol under various domestic wireless channel conditions, DTSMA outperforms in terms of packet delivery ratio and average end-to-end packet delay which are important metrics for time-sensitive audio-video applications. Simulation results also show that DTSMA outperforms TSMA in terms of average end-to-end packet delay and average delay jitter when the severity of propagation impairment is high. Author Affiliation: Institute for Infocomm Research, Agency for Science, Technology and Research (AaSTAR), 1 Fusionopolis Way, #21-01 Connexis (South Tower), Singapore 138632, Singapore Article History: Received 1 August 2007; Revised 31 August 2008; Accepted 8 October 2008 Article Note: (miscellaneous) Responsible Editor: L. Lenzini

With the convergence of multimedia applications and wireless communications, there is a need to support real-time traffic in wireless networks. In general, real-time packets must be delivered before a certain delay upper bound. In the literature, feasible earliest due date (FEDD) is one of the scheduling algorithms proposed to provide packet delay upper bound guarantees over a time-varying wireless channel. However, FEDD is reactive with respect to changes in the wireless channel. In view of this, we propose a novel deadline-based scheduling algorithm called proactive earliest due date (PEDD), which dynamically adjusts a packet's deadline in anticipation of an upcoming change in the channel condition. Similar to FEDD, PEDD is idealistic, as they both assume the availability of the exact channel knowledge. This is not implementable and, thus, this paper further proposes a realistic version of PEDD, caned R-PEDD. R-PEDD uses a probing mechanism to acquire the channel knowledge, which in turn is used for the packet deadline adjustment. Since probe packets consume bandwidth, a modified version of R-PEDD, called R-PEDD+ is proposed to derive the required channel information from recent packet transmissions. We have performed extensive simulations using OPNET to evaluate the performance of these proposed algorithms. In short, PEDD always outperforms a couple of existing algorithms in the literature. R-PEDD and R-PEDD+ are both capable of approximating the performance of the idealistic PEDD in a realistic wireless channel. However, their performance deteriorates with more rapid changes in the channel condition. Index Terms--Channel-knowledge acquisition, delay upper bound, earliest due date (EDD), packet scheduling, wireless networks.