Mohammad M. Shurman

Performance evaluation of multiuser diversity in multiuser two-hop cooperative multi-relay wireless networks using maximal ratio combining over Rayleigh fading channels

Multiuser diversity MUD cooperative wireless networks combine the features of the MIMO systems without confronting the physical layer constraints by providing multiple copies of the transmitted signal from the source to the destination with the help of the relay node. Cooperative wireless networks have attracted the full attention in the last few years and are implemented widely in many wireless communication systems to adapt for the fading impairments, provide higher data rates, and improve the performance of the wireless communication systems. In this paper, we present an informative study for the reason of evaluating the performance of the MUD in the multiuser two-hop cooperative multi-relay networks using maximal ratio combining. Furthermore, we derive tight closed-form expressions of outage probability and symbol error probability for the amplify-and-forward and fixed decode-and-forward protocols with the MUD. Additionally, we conduct a simulation study to show to what extent our analytical and simulation results agree with each other. It is worthy to mention that our analytical and simulation results agree fairly with each other under high average signal-to-noise ratio, whereas they show that our proposed system with multiple relays provides significant improvements over those previously proposed systems having only one relay. Copyright

LEACH enhancements for wireless sensor networks based on energy model

The low-energy adaptive clustering hierarchy (LEACH) protocol is one of the most adaptive protocols used in the wireless sensor networks (WSNs). LEACH is a hierarchical model that provides a powerful strategy for energy balancing, using head rotations. However, the original LEACH protocol suffers from many drawbacks and many researchers proposed new methods to mitigate them. In this paper, we propose two approaches based on an energy model to enhance cluster heads (CHs) selection method through not only minimizing the power consumption of network nodes, but also minimizing the number of CHs. The first proposed approach effectively selects a cluster head that has the lowest power consumption when communicating with other nodes. In addition to what is proposed in the first approach, the idea of incorporating the shortest distance has been considered in the second proposed approach. This significantly decreases the energy consumption and increases the lifetime of associated nodes.

Closed-form expression of bit error rate in dual-hop dual-branch mixed relaying cooperative networks with best-path selection over Rayleigh fading channels

In this paper, a new cooperative-diversity network with simple dual hop virtual diversity with mixed decode-and-forward and amplify-and-forward with best path selection is proposed. A closed-form expression for the average bit error rate of the communication system, assuming phase shift keying modulation scheme over independent non-identical Rayleigh fading channels, is derived. The results show that the proposed model outperforms the regular cooperative network models with a sub-optimal allocation for the relay relative distance.

A collaborative reputation approach to avoid misbehaving nodes in MANETs

Ad-hoc networks carry out routing and forwarding functions through available nodes. These nodes act as base stations and also are involved in route discovery and maintenance, forwarding traffic, and network management functions. Nodes expend most of their energy to forward packets to others without receiving any direct gain from doing so. A misbehaving and greedy node only considers its own short-term utility, and it may not choose to participate within the network. A reputation approach (RAP) is proposed in this paper, based on the reputation model that is used to detect and isolate misbehaving nodes which do not cooperate in forwarding packets of other nodes. Promising results are found through extensive simulation using GloMoSim in identifying selfish nodes.

Static cluster and dynamic cluster head (SCDCH) adaptive prediction-based algorithm for target tracking in wireless sensor networks

Wireless sensor networks consist of large number of sensor nodes that have an ability to interact with the surrounding environment. The importance of finding the suitable protocol to estimate the trajectory for any moving target in a certain environment is a case of study for researchers. In this paper, new and accurate protocol for target tracking with minimum energy consumption is proposed. The proposed approach uses the static cluster and dynamic cluster head mechanism (SCDCH) to collect data from the active nodes, and then forwards it to the cluster head (CH), which in turn will send the collected data to the base station, without changing cluster border during the networks lifetime. Simulation results show that the proposed protocol has higher accuracy and save more energy compared with static clustering protocols which in turn increases the network lifetime.

Performance analysis of amplify-and-forward cognitive relay networks with interference power constraints over Nakagami-m fading channels

With the wide-spread wireless applications and services, the spectrum scarcity has become a challenging problem. Thus, it is necessary to find a solution to have more spectrum bands. One from these solutions is the cognitive relay network, where we can increase the spectrum utilization by combining the cognitive radio (CR) with cooperative spectrum sharing systems. In this paper, the performance of cognitive relay networks under interference power constraints from the primary user (PU) is studied. Here, the system models are studied by utilizing different scenarios. The first scenario is by using a single amplify-and-forward (AF) relay, and the second one is by using a single AF relay with selection diversity. Tabulated expressions for the outage probability (OP) are derived over independent and non-identically distributed Nakagami-m fading channels. Numerical results show that the cooperative spectrum sharing transmission with a single AF relay and selection diversity outperforms both the direct transmission and the transmission using a single AF relay for the underlay cognitive relay networks. Furthermore, the results show that the outage performance depends on the minimum fading severity parameters of the two hops of the secondary user (SU) and the OP decreases as the PU moves away from the SU network.

Outage probability of dual-hop amplify-and-forward cognitive relay networks under interference power constraints over Nakagami-m fading channels

In this paper, the performance of the outage probability (OP) for cognitive dual-hop relay networks with amplify-and-forward (AF) relay under spectrum sharing constraints on primary user (PU) over independent and identically distributed (i.i.d.) Nakagami-m fading channels is investigated. An exact closed-form expression for the OP of the proposed system is derived under the peak interference power (Ip) at the primary user. The impact of the PU location on the OP performance is studied also.

Outage probability of amplify-and-forward underlay cognitive relay networks with selection diversity over Nakagami-m fading channels

In this paper, the outage performance is investigated for cognitive dual-hop relay networks with amplify-and-forward (AF) relay and selection combining (SC) receiver at the destination under spectrum sharing constraints on primary user (PU) over independent and identically distributed (i.i.d.) Nakagami-m fading channels. We derive an exact closed-form expression for the outage probability (OP) of the considered system under the peak interference power Ip at the primary user, and the impact of the PU location on the OP performance is studied also. Moreover; the effects fading severity for the two hops on the OP is investigated also for this cognitive relay network (CRN).

N-BEB: New backoff algorithm for IEEE 802.11 MAC protocol

IEEE 802.11 standard primarily utilizes Distributed Coordination Function (DCF) which is based on carrier sense multiple access with collision avoidance (CSMA/CA). IN DCF, when a collision occurs, then a backoff algorithm will take place to randomize medium access for the nodes. The default backoff mechanism used in 802.11 is the binary exponential backoff (BEB) algorithm. In this paper, we analyze the behavior of various backoff algorithms used in IEEE802.11 standard: BEB, I-BEB, and E-BEB, then we propose the New Binary Exponential Backoff (N-BEB) algorithm to improve channel access fairness while preserving the channel throughput. Our N-BEB algorithm improves the selection process of the contention window CW, based on the number of successful and unsuccessful transmissions. Simulation results confirm fairness improvement, power consumption enhancement, reduction of dropped packets and high delivery ratio for proposed protocol over BEB, I-BEB, and E-BEB protocols.

Source location privacy in a cluster-based wireless sensor networks against local adversary

Wireless Sensor Networks (WSNs) have been popular nowadays as they provide low-cost solutions of a wide-range of real life challenges. WSN consists of a group of infrastructure-less wireless nodes that works together to deliver physical or environmental monitored data from source to sink. In general, WSNs are vulnerable to wireless attacks due to the open nature of the wireless networks. Also, WSNs suffer from unbalanced energy consumption which reduces the network life time due to the creation of the energy-hole. Two types of threats may occur for the WSNs privacy, which are; contextual and content privacy; location privacy is considered as an example for contextual privacy, where an eavesdropper tries to find the location of the source or sink. Hence, ensuring the security and privacy in WSNs is considered as an essential issue. In this paper, we avoid energy-hole creation and protect source location privacy (SLP) via proposing two source privacy protection schemes based on clustering, which are dynamic shortest path scheme (DSP) and Dynamic tree scheme (DT). We adopted grid-based clustering technique to divide the network to several square clusters. Matlab simulation evaluates the performance of the two proposed schemes in terms of safety period.