Bhabani P. Sinha

Channel assignment using genetic algorithm based on geometric symmetry

The paper deals with the channel assignment problem in a hexagonal cellular network with two-band buffering, where channel interference does not extend beyond two cells. Here, for cellular networks with homogeneous demands, we find some lower bounds on the minimum bandwidth required for various relative values of s/sub 0/, s/sub 1/, and s/sub 2/, the minimum frequency separations to avoid interference for calls in the same cell, or in cells at distances of one and two, respectively. We then present an algorithm for solving the channel assignment problem in its general form using the elitist model of genetic algorithm (EGA). We next apply this technique to the special case of hexagonal cellular networks with two-band buffering. For homogeneous demands, we apply EGA for assigning channels to a small subset of nodes and then extend it for the entire cellular network, which ensures faster convergence. Moreover, we show that our approach is also applicable to cases of nonhomogeneous demands. Application of our proposed methodology to well-known benchmark problems generates optimal results within a reasonable computing time.

High-Performance Hardware Implementation for RC4 Stream Cipher

RC4 is the most popular stream cipher in the domain of cryptology. In this paper, we present a systematic study of the hardware implementation of RC4, and propose the fastest known architecture for the cipher. We combine the ideas of hardware pipeline and loop unrolling to design an architecture that produces 2 RC4 keystream bytes per clock cycle. We have optimized and implemented our proposed design using VHDL description, synthesized with 130, 90, and 65 nm fabrication technologies at clock frequencies 625 MHz, 1.37 GHz, and 1.92 GHz, respectively, to obtain a final RC4 keystream throughput of 10, 21.92, and 30.72 Gbps in the respective technologies.

A survey on the channel assignment problem in wireless networks

Efficient allocation of channels for wireless communication in different network scenarios has become an extremely important topic of recent research. The main challenge lies in the fact that the channel allocation problem is NP-complete. Because of a maximum allowable time limit imposed in practical situations for allocation of channels, sometimes we may need to be satisfied with a near-optimal solution. In this correspondence, we present a discussion on the various challenges and approaches that have been used by different researchers to solve the problem of channel allocation taking into account different interference issues and efficient utilization of available communication channels for cellular mobile (including multimedia communication) environment and cognitive radio based networks. Copyright

A new network topology with multiple meshes

This paper introduces a new network topology, called Multi-Mesh (MM), which uses multiple meshes as the basic building blocks interconnected in a suitable manner. The proposed network consists of n/sup 4/ processors and is 4-regular with a diameter of 2n. The network also contains a Hamiltonian cycle. Simple routing algorithms for point-to-point communication, one-to-all broadcast, and multicast have been described for this network. It is shown that a simple n/sup 2//spl times/n/sup 2/ mesh can also be emulated on this network in O(1) time. Several application examples have been discussed for which this network is found to be more efficient with regard to computational time than the corresponding mesh with the same number of processors. As examples, O(n) time algorithms for finding the sum, average, minimum, and maximum of n/sup 4/ data values, located at n/sup 4/ different processors have been discussed. Time-efficient implementations of algorithms for solving nontrivial problems, e.g., Lagranges interpolation, matrix transposition, matrix multiplication, and Discrete Fourier Transform (DFT) computation have also been discussed. The time complexity of Lagranges interpolation on this network is O(n) for n/sup 2/ data points compared to O(n/sup 2/) time on mesh of the same size. Matrix transpose requires O(n/sup 0.5/) time for an n/spl times/n. matrix. The time for multiplying two n/spl times/n matrices is O(n/sup 0.6/) with an AT-cost of O(n/sup 3/). DFT of n sample points can be computed in O(n/sup 0.6/) time on this network. The previous papers show that n/sup 4/ data elements can be sorted on this network in O(n) time.

Fault-tolerant routing in distributed loop networks

The ring network is a popular network topology for implementation in local area networks and other configurations. But it has a disadvantage of high diameter and large communication delay. So loop networks were introduced with fixed-jump links added over the ring. In this paper, we characterize some values for the number of nodes for which the lower bound on the diameter of loop networks is achieved. We also give an O(/spl delta/) time algorithm (where /spl delta/ is the diameter of the graph) for finding a shortest path between any two nodes of a general loop network. We also propose a scheme to find a near optimal path (not more than one over the optimal) in case of a single node or link failure.

An Energy-Efficient Communication Scheme for Wireless Networks: A Redundant Radix-Based Approach

We propose a redundant radix based number (RBN) representation for encoding and transmitting data for applications which typically utilize low cost devices and demand low power operations with simple modulation techniques like ASK, OOK and FSK. Coupled with silent periods for communicating the digit zero, this encoded communication scheme, called as RBNSiZeComm, provides a highly energy-efficient technique for data transmission. Considering an n-bit data representation and assuming that each of the 2n binary strings is equally likely to occur, theoretically obtainable fraction of energy savings by using our proposed RBNSiZeComm transmission protocol is, on an average, 1 - n+2/4n. A hybrid modulation scheme using FSK and ASK with non-coherent detection based receiver for the RBNSiZeComm protocol has been presented. Assuming equal likelihood of all possible binary strings of a given length, there is nearly 53% savings in energy on an average at the transmitter relative to binary FSK, over additive white gaussian noise (AWGN) channels. Simulation results demonstrate that compared to binary FSK, our proposed implementation can extend the battery life of devices from about 33% to 62% on an average in applications like remote healthcare and wireless sensor networks for agriculture.

On an optimal algorithm for channel assignment in cellular networks

A cellular network is often modelled as a graph and the channel assignment problem is formulated as a coloring problem of the graph. Sen et al. (1998) introduced the notion of cellular graphs that models the hexagonal cell structure of a cellular network. Assuming a k-band buffering system where the interference does not extend beyond k cells away from the call originating cell, we provided two different formulations of the channel assignment problem: distance-k chromatic number problem and k-band chromatic bandwidth problem. The channel assignment algorithms presented in Sen et al. were non-optimal. In this paper we provide: (i) a new algorithm for the distance-k chromatic number problem that is optimal and (ii) a near optimal algorithm for the 2-band chromatic bandwidth problem that has a performance bound of 4/3. The complexity of the algorithms is O(p), where p is the number of cells.

An efficient sorting algorithm on the multi-mesh network

The shear-sort algorithm on an SIMD mesh model requires 4/spl radic/N+o(/spl radic/N) time for sorting N elements arranged on a /spl radic/N/spl times//spl radic/N mesh. In this paper, we present an algorithm for sorting N elements in time O(N/sup 1/4/) on an SIMD multi-mesh architecture, thereby significantly improving the order of the time complexity. The multi-mesh architecture is built around n/sup 2/ blocks, where each block is an n/spl times/n mesh with n=N/sup 1/4/, so that each processor will uniformly have four neighbors in the final topology.

Fast parallel algorithms for binary multiplication and their implementation on systolic architectures

Two algorithms for parallel multiplication of two n-bit binary numbers are presented. Both use column compression to increase the speed of execution. They require almost regular interconnection between only two types of cells and hence are very suitable for VLSI implementation. Both of them can also be easily modified to handle twos complement numbers with constant differences in time. >

Multi-Mesh-an efficient topology for parallel processing

This paper introduces a new interconnection scheme, called Multi-Mesh (MM) network, for parallel processing which uses multiple meshes as the basic building blocks interconnected in a suitable manner. The interconnection pattern is regular and suitable for VLSI implementation. Each processor in the network has degree four with a resulting diameter upper bounded by 2n for n/sup 4/ processors. Routing can easily be done within 2n time on this network. Sum/minimum/maximum of n/sup 4/ data values can be found in O(n) time. Two n/spl times/n matrices can be multiplied by the MM network in O(n/sup 0.6/) with an AT-cost of O(n/sup 3/). The DFT of n sample points can be computed in O(n/sup 0.6/) time on this network. Sorting of n/sup 3/ data elements resident on n/sup 3/ processors can be done in 2n log n+14n+o(n) time.<<ETX>>