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The IEEE 802.16 wireless metropolitan area network (WMAN) standard is a promising and cost-effective, last-mile wireless technology for the provision of broadband Internet access to end users. In this paper, we present an accurate analytical model that describes the contention-based bandwidth (BW) request scheme of the 802.16 standard, which is also known as WiMAX, for the persistent and nonpersistent request generation cases. We first model the contention procedure with a Markov chain, taking into account the exponential back-off procedure as well as the waiting time for a BW assignment and the possible timeout for lost messages. The accuracy of the model is then evaluated by comparing it with simulation results for a wide range of values of the parameters involved. We use this model to accurately calculate the capacity of the contention slots in delivering BW requests, from which the average access delay is also found. These measures are used to determine a proper configuration for the efficient operation of the contention-based BW request scheme. The proposed model provides a useful analytical tool for devising adaptive configuration mechanisms for the contention access mode of the 802.16 medium access control (MAC) layer. Index Terms--Contention-based access, IEEE 802.16, Markov chain (MC), medium access control (MAC), WiMAX, wireless networks.

In this paper, we propose a cross-layer optimization scheme for delivery of scalable video over multirate wireless networks, in particular the popular 802.11 based wireless local area network (WLAN). The 802.11 based networks use a link adaptation mechanism in the physical layer (PHY) to maintain the reliability of transmission under varying channel conditions. When channel condition worsens, the reliability is maintained by employing more robust modulation and coding schemes, at the cost of reduced PHY bit rate. The reduced bit rate will result in lower available throughput for applications. For scalable video streaming applications, the conventional solution to this problem is to reduce the video bit rate by dropping the higher enhancement layers of the scalable video. We show in this article that the video quality can be improved, if the link adaptation scheme uses more intelligent reliability criteria and adjusts the PHY parameters used for delivering each video layer, according to the relative importance of that layer. Our scheme achieves better video quality without increasing the traffic load of the WLAN. For this purpose we present temporal fairness constraints and formulate an optimization problem for assigning different PHY modes to different layers of scalable video; the solution to this problem provides a set of PHY configuration parameters that achieve the highest possible video quality while meeting the admission control constraints in the network. Performance evaluations demonstrate that our method outperforms the existing mechanisms. Index Terms--Cross-layer design, H.264, multiple-input multiple-output (MIMO), scalable video coding (SVC), video over wireless, WLAN, 802.11n.

A novel class of AT squared optimal networks, based on the methodology associated with large K-shuffle network mapping, calculated the multidimensional Discrete Fourier Transform (DFT). The networks exhibited conventional layouts and were used for index-rotation separation, essential for multidimensional calculations. The VLSI network circuits calculated the DFT at specified points.

Interconnected constituents of an N by N image in a reconfigurable network consisting of N cube processors is labelled by applying a constant-time algorithm. The alogorithm determines the minimum labelled potential energy in each constituent with the help of a new constant time method. The processors used by the algorithm are reduced by the formula N(super (2+(1/d))).

In recent years, a considerable amount of research has been done on the problem of labeling digitized images. Because connectivity in images possesses both local and global properties, different algorithmic techniques have been proposed to exploit one or both of these properties. This paper provides a characterization and survey of the various parallel techniques proposed for this problem. Parallel architectures and parallel models of computation that implement these techniques are also studied.

This paper presents a novel recursive algorithm for generating higher order multidimensional (m-D) discrete cosing transform (DCT) by combining the computation of [2.sup.m] identical lower order (smaller size) DCT architectures. One immediate outcome of our results is the true 'scalability' of the DCT computation. Basically, an m-D DCT computation can be constructed from exactly one stage of smaller DCT computations of the same dimension. This is useful for both hardware and software solutions, in which a very efficient smaller size m-D DCT core has been developed, and a larger DCT computation is required. The resulting DCT networks have very simple modular structure, highly regular topology, and use simple arithmetic units. Index Terms--Modular structures, multidimensional structures, permutation matrices, recursive architectures, tensor products.