This paper presents the use of a multi-objective genetic algorithm (MOGA) for solving an access point placement problem in a wireless LAN. The aim is to maximize signal coverage over the interested area. The problem has been formulated as a multi-objective optimization problem where the decision variables are derived from the locations of the access points in the target area. The objectives consist of the number of access points and the average SNR over the whole area. The major advantage of using MOGA is that multiple optimal placement configurations for different numbers of access points can be obtained from a single run. A set of solutions provides more alternatives to the network designer. The simulation results indicate that the MOGA is capable of generating a placement result which is superior to that produced using standard placement techniques. In addition, the result assessment has been confirmed using statistical and analyzed data profile.

Multicast operation is an important operation in multicomputer communication systems and can be used to support several collective communication operations. A significant performance improvement can be achieved by supporting multicast operations at the hardware level. We propose an asynchronous tree-based multicasting (ATBM) technique for multistage interconnection networks (MINs). The deadlock issues in tree-based multicasting in MINs are analyzed first to examine the main causes of deadlocks. An ATBM framework is developed in which deadlocks are prevented by serializing the initiations of tree operations that have a potential to create deadlocks. These tree operations are identified through a grouping algorithm. The ATBM approach is not only simple to implement but also provides good communication performance using minimal overheads in terms of additional hardware requirements and synchronization delay. Using the ATBM framework, algorithms are developed for both unidirectional and bidirectional multistage interconnection networks. The performances of the proposed algorithms are evaluated through simulation experiments. The results indicate that the proposed hardware-based ATBM scheme reduces the communication latency when compared to the software multicasting approach proposed earlier.

In this peeper, we propose a tree-based multicasting algorithm for Multistage Interconnection Networks. We first analyze the necessary conditions for deadlocks in MINs. Based on these observations, an asynchronous tree-based multicasting algorithm is developed in which deadlocks are prevented by serializing the initiations of branching operations that have potential for creating deadlocks. The serialization is done using a technique based on grouping of the switching elements. The preliminary simulation results are encouraging as it lowers the latency by almost a factor of 4 when compared with the software multicasting approach proposed earlier.

In this paper, we analyze several issues involved in developing low latency adaptive wormhole routing schemes for two-dimensional meshes. It is observed that along with adaptivity, balanced distribution of traffic has a significant impact on the system performance. Motivated by this observation, we develop a new fully adaptive routing algorithm called positive-first-negative-first for two-dimensional meshes. The algorithm uses only two virtual channels per physical channel creating two virtual networks. The messages are routed positive-first in one virtual network and negative-first in the other. Because of this combination, the algorithm distributes the system load uniformly throughout the network and is also fully adaptive. It is shown that the proposed algorithm results in providing better performance in terms of the average network latency and throughput when compared with the previously proposed routing algorithms.

In this paper, we present a new concept of region of adaptivity with respect to various routing algorithms in wormhole networks. Using this concept, we demonstrate that the previously proposed routing algorithms, though more adaptive, causes an uneven workload in the network which limits the performance improvement. A is observed that balanced distribution of traffic has greater impact on system performance than the adaptivity or efficiency of the algorithm. Based on these motivating factors, we have presented a new fully adaptive routing algorithm for 2-dimensional meshes using one extra virtual channel. The algorithm is more efficient in terms of the number of paths it offers between the source and the destination and also distributes the network load more evenly and symmetrically. The simulation results are presented and are compared with the results of previously proposed algorithms. It is shown that the proposed algorithm results in much better performance in terms of the average network latency and the throughput.>