Although bi-orthogonal coding requires half the bandwidth of the other Hadamard-type waveform codes, such coding schemes are attractive only when large bandwidth is available, the finite projective plane (FPP) based waveform coding schemes are proposed and evaluated through three performance metrics, which are with similar error performance and cross correlation with Hadamard-type waveform codes. Nevertheless, the bandwidth requirements for the proposed FPP schemes grow in a quadratic way, but not exponentially with the values of message bit numbers (k), which show obvious advantages over the bi-orthogonal scheme when k ≥ 6 at the expanse of little codeword error performance.

In this paper, based on the theory of finite projective plane (FPP), a novel channel assignment is proposed with Markov chain modeling of N channels and N users, especially when the channel resources are often idle due to inefficient uses. The arrangements of intermixed grouping of channels based on FPP mechanism relate Markov chain modeling with our proposed punch through ratio (PTR) formulations successfully provide fairness among users as well. The defined throughput is obviously enhanced from simulation results with the proposed FPP scheme, especially when the traffic load is light. Nevertheless, if the proposed scheme is combined with successive interference cancellation (SIC) techniques, much better throughput for heavy traffic load is also predicted.

We propose a hierarchical least mean square (LMS) algorithm where the taps of a filter are organized into a hierarchy, and the minimization process is performed repeatedly from the bottom level to the top level. The results of performance evaluation indicate that the proposed hierarchical LMS algorithm can speed up convergence rate and reduce the excess mean squared error (MSE) of the standard LMS algorithm.

Time-hopping techniques have been applied in direct sequence code division multiple access (DS-CDMA) to reduce the harmful effects of a sudden power surge in the received signals. The conventional approaches may result in either nonuniform distribution of transmitting users among time slots or uneven interference from the dominant interferers. For both cases, the bit-error rate (BER) increases significantly for the users suffering the worst case condition. We propose an optimal time-hopping scheme based on the theory of finite projective planes for DS-CDMA to distribute interference evenly among participating users. The performance evaluation is divided into four parts. We demonstrate that both the average BER, probability of outage, and bandwidth efficiency can be improved by using the proposed time hopping scheme in comparison to other time-hopping schemes, such as the fixed allocation scheme and random selection scheme for various modulation methods including frequency shift keying-coherent demodulation (FSK-CD), differential phase shift keying (DPSK), binary phase shift keying (BPSK), and FSK with noncoherent demodulation (FSK-NCD). We compare the proposed time hopping scheme with nontime-hopping DS-CDMA with identical signal bandwidth. We then prove that the proposed scheme is optimal in minimizing interference.

It is known that the flexibility and capacity of asynchronous transfer mode (ATM) networks can meet the bandwidth requirements of multimedia applications. In ATM networks, switching is one of the major bottlenecks of end-to-end communication. We propose using a multiple partitionable circular bus network (MPCBN) as an ATM switch. Connection requests are first transformed into a graph where vertices and edges represent connection requests and conflicts among connection requests, respectively. We then use a graph traversal algorithm to select a maximal set of requests for execution in physically partitioned buses. An approach of using finite projective planes is then used to reduce the number of switch points from O(N/sup 2/) to O(N /spl radic/N), where N is the number of ports of a switch. A performance evaluation for both uniform and bursty data sources shows that the approach of using finite projective planes to reduce the number of switch points results in a small increase of cell loss probability.

The granularity of frequency reuse of the conventional approach for channel assignment is a cluster (a partition of a coverage area). That means that the channels used in cells (partitions of a cluster) within the same cluster are distinctive. In this paper, we propose a different approach for channel assignment such that the channels are reused among cells in the same cluster. However, there are two constraints on the reuse of channels in a cluster to keep the cochannel interference in check. First, adjacent cells are not allowed to use the same channels. Second, the number of "one-hop-away" cells assigned the same channels is limited. The approach we take is based on the theory of finite projective planes. By mapping the sets of points of a finite projective plane to the channels assigned to a cell, channel reuse is achieved within a cluster. The performance evaluation is done in three parts. In the first part, we show that the channel reuse efficiency of the proposed approach is higher than that of the conventional approach with a tradeoff of a lower signal-to-interference (S/I) ratio. In the second part, the S/I is kept the same, and we demonstrate that the proposed approach has a higher channel reuse efficiency when the cluster size is reasonably small. In the third part, the worst case analysis for the situation that mobile users roam around the cell boundary is illustrated and a strategy of channel allocation is provided to avoid the worst case conditions.

The authors present a dynamically partitionable circular bus network (PCBN) and efficient algorithms for maximizing its utilization. In their approach, a distributed network is transformed into a graph, in which a vertex represents a communication request and an edge denotes the conflict between a pair of communication requests. A graph traversal algorithm is applied to the graph to identify some maximal independent sets of vertices. The communication requests corresponding to the vertices of a maximum independent set call proceed in parallel. By computing the expected size of the maximal independent sets of a graph, the improvement ratio of the network can be obtained. The network control and synchronization techniques of PCBN are described in detail. The idling problem in the execution of nonconflicting requests is also discussed.>

A distributed mutual exclusion algorithm based on Huffmann trees is described. A request message is passed from a leaf node all the way to the root, signaling that a node is allowed to enter the critical section. Fault tolerance is achieved by forming the Huffman tree dynamically. It is shown that the approach has broad applications in distributed systems where nodes are often organized as a logical tree for ease of coordination. High fault tolerance is achieved, since a faulty node can be detected by its neighbor and thus be deleted from the tree.>

An efficient dynamic graph traversal algorithm is used to identify nonconflicting requests and to allocate network resources in a dynamically partitionable bus network (DPBN). In centralized network control a special processor receives from the control computer of a partitionable bus network an adjacency matrix which indicates conflicts among requests. It applies the dynamic graph traversal algorithm and returns the identified nonconflicting requests to the control computer. The control computer then physically partitions the network into a number of subnetworks for processing the nonconflicting requests in parallel. In distributed control, each station determines conflicts and sets the switches. The results of performance evaluation show a 40% decrease of network delay as compared with a fully utilized, but unpartitioned local area network.>