Ansuman Bhattacharya

Multimedia communication in cognitive radio networks based on sample division multiplexing

In this paper, we address the problem of channel sensing, channel allocation and transmission of multimedia signals in a cognitive radio network, while maintaining the required quality of service (QoS) constraints. Depending on the type of signal and QoS requirements, different types of multimedia signals need different bandwidths for communication. In typical wireless systems, unless a contiguous frequency band in the spectrum with width at least equal to the required bandwidth is obtained, multimedia communication can not occur with the desired QoS. We propose here a novel technique based on sample division multiplexing (SDM) to overcome this issue. Our proposed approach is based on utilizing several frequency bands, each of smaller width than the required bandwidth but whose sum total equals at least the required bandwidth. Towards this end, we present algorithms for channel reservation, channel sensing and allocation along with protocols for transmission and reception. Our approach also ensures preemption of secondary users by the primary users as typically demanded in a cognitive radio based communication environment.

Multi-path routing In Cognitive Radio Networks for multimedia communication using sample division multiplexing

We propose a novel scheme for multi-path routing in a Cognitive Radio Network (CRN) for multimedia communication, even when a contiguous band of required width is not available for any hop in the route. The proposed scheme is based on an extension of the idea of Sample Division Multiplexing (SDM) as given in [1] for single-hop communication. Starting from the source node, we first explore the available (free) number of channels (not necessarily contiguous) between every pair of 1-distance neighbor nodes by the help of appropriate control messages. With the information gathered from this step, the network graph G is constructed. We run the max-flow algorithm [8] on this network graph to find the set of routes between the source and the destination nodes so that the sum total of the usable numbers of channels through all these routes is equal to the required number of channels for the multimedia signal to be communicated. In essence, each data packet of the multimedia signal is split into several sub-packets following the basic concept given in [1] each of which needs much smaller bandwidth than the original packet, and these sub-packets are sent through all these routes to be eventually received by the destination node with the desired QoS. The time complexity of our proposed algorithm for this route discovery is O(pf + TSD), where p is the number of edges in the network graph (G), f is the maximum flow in G and TSD is the initialization time for constructing the network graph. We have shown that TSD is O(Δδmax), where Δ is the diameter and δmax is the maximum node degree of the network graph.

An efficient protocol for load-balanced multipath routing in mobile ad hoc networks

Abstract In this paper, we propose a new routing protocol called the Least Common Multiple based Routing (LCMR) for load-balanced multipath routing in Mobile Ad hoc NETworks (MANETs). First, we find multiple paths between a source to a destination, when those exist, along with the estimates of the time to route a packet along each of these paths. The data packets originating from the source to the destination are then distributed along these multiple paths in such a way that the number of data packets sent along any such path is inversely proportional to the routing time through this path. This distribution strategy keeps the load balanced along all the paths so that the overall routing time for sending the data packets is minimized. Routes between a given source-destination pair are discovered in a way similar to that in the Ad hoc On-demand Distance Vector (AODV) routing protocol with the difference that instead of the number of hops, the routing time for reaching the destination along every route is measured, and multiple routes, if those exist, will also be determined by the route discovery process. Our proposed technique for distribution of packets along different routes is very elegant with a better performance than the existing load-balanced routing protocols like Fibonacci Multipath Load Balancing (FMLB) and Multiple AODV (MAODV), as established from a theoretical analysis as well as through simulation results.

Noncontiguous Channel Allocation for Multimedia Communication in Cognitive Radio Networks

In conventional wireless systems, unless a contiguous frequency band with width at least equal to the required bandwidth is obtained, multimedia communication cannot be effected with the desired quality of service. We propose here a novel channel allocation technique to overcome this limitation in a cognitive radio network, which is based on utilizing several noncontiguous channels, each of width smaller than the required bandwidth, but whose sum equals at least the required bandwidth. We present algorithms for channel sensing, channel reservation, and channel deallocation along with transmission and reception protocols with two different implementations based on FDM-FDMA and OFDM-FDMA techniques. Simulation results for both these implementations show that the proposed technique outperforms the existing first-fit and best-fit allocation techniques in terms of the average number of attempts needed for acquiring the necessary number of channels for all traffic situations ranging from light to extremely heavy traffic. Furthermore, the proposed technique can allocate the required numbers of channels in less than 1 s with FDM-FDMA even (4.5 s with OFDM-FDMA) for 96% traffic load, while the first-fit and best-fit techniques fail to allocate any channel in such situations.

A steganographic technique based on VLSB method using RC4 stream cipher

This paper presents a steganographic technique for embedding a secret file (any file e.g. audio,video) into a color image. We have used RC4 technique to generate pseudo random position for embedding secret data. After determining the position embedding is done using Variable Least Significant Bit (V LSB) method. The number of bits embedded into a pixel depends on the pixel value itself. An (N × N) cover image is divided into q number of (b×b) blocks and for each block RC4 method has been applied. 2q different key values for random key generation of q blocks are the secret key here. As RC4 algorithm is being used for randomizing the position of embedding, this method ensures higher level of security with good embedding capacity. Besides that the amount of embedded bits into a pixel purely depends upon the pixel itself, so the image quality is less distorted.

Energy-Efficient Multimedia Communication for Cognitive Radio Networks

We propose an elegant source coding technique with highly asymmetric frequencies of occurrences of different symbols. Keeping the symbol with the highest frequency of occurrence as silent during transmission, we achieve substantial savings of transmitter and receiver energies by using a hybrid Amplitude Shift Keying ASK - Frequency Shift Keying FSK modulation/demodulation technique. Our results show that for channels with Additive White Gaussian Noise AWGN, on an average, the transmitter side energy is reduced by about 53%, while at the receiver side there is about 17.2% savings. Due to the savings of transmitter and receiver energies and the low cost/complexity of the proposed transceiver, our proposed scheme is suitable for multi-hop communication in Cognitive Radio Networks CRNs.

On-demand routing for multimedia communication through Cognitive Radio Networks using sample division multiplexing

We propose a novel distributed on-demand routing scheme for multimedia communication through Cognitive Radio Networks (CRN). The basic technique is to effect the multimedia communication through multiple routes between the source and the destination nodes based on Sample Division Multiplexing (SDM) [2] such that the sum of flow along all such routes is equal to the required flow between the source-destination pair. In contrast to [1] where a centralized Max-Flow algorithm has been used, we propose here a protocol based on distributed algorithms for finding the multiple routes with the required flow by relaxing same of the constraints on the network structure assumed in [1]. The proposed protocol has a worst-case time complexity of O(|E| × DN), |E| being the number of edges of the network and DN being the number of channels required for communicating a multimedia signal, which is also less than that of the centralized algorithm in [1]. Simulation results on different network structures, however, reveal that the average time complexity of the proposed protocol is much smaller than the above worst-case time complexity.

Candidate core selection for load-balanced multicore shared tree multicasting

Multicasting can be done in two different ways: source based tree approach and shared tree approach. Protocols such as Core Based Tree (CBT), Protocol Independent Multicasting Sparse Mode (PIM-SM) use shared tree approach. Shared tree approach is preferred over source-based tree approach because in the latter construction of minimum cost tree per source is needed unlike a single shared tree in the former approach. Objective of the present work is two-fold: to provide a candidate core selection approach for shared tree multicasting to guard against any possible core failure and to provide an efficient load balanced multicore multicasting approach using the candidate cores.

An anti-jamming protocol based on secret reallocation of channels

In this paper we propose an anti-jamming technique which is based on a secret reallocation of the jammed channels. Jamming is defined to be a deliberate use of radio noise or signals in an attempt to disrupt communications. We present suitable algorithms to be executed by a transmitting and a receiving node, assuming the possible presence adversaries acting as jammers. In our proposed algorithm, for a network with n jammed channels out of m simultaneously active communications, the average number of attempts to find n free channels is equal to ⌈1/f⌉, where f is the fraction of free channels out of total of C channels, and is hence independent of both m and n. Simulation results of our proposed approach on random networks also show that our proposed anti-jamming protocol is quite effective in counteracting jamming attacks.

MRBNS: A new energy-efficient communication scheme in low power wireless networks

A new energy-efficient communication scheme has been proposed based on a novel source coding technique along with the idea of silent communication, so that the frequencies of occurrences of different symbols in the encoded message become very asymmetric. Keeping the symbol period with the highest frequency of occurrence as silent during transmission, we achieve substantial savings of transmitter and receiver energies by using a hybrid FSK-ASK modulation/demodulation technique. We also design the corresponding protocols for transmission and reception of messages and evaluate their performances to compare with other existing techniques. Our results demonstrate that for additive white Gaussian noise in channels, on an average, the transmitter side energy is reduced by about 53%, while at the receiver side there is about 17.2% savings. Due to the savings of both transmitter and receiver energies, our proposed scheme is particularly suitable for multi-hop communication in low power wireless networks.