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Abstract: This paper proposes the use of equalization concepts in frequency domain that exploit the frequency domain channel matrix to combat inter-carrier interference (ICI) instead of inter-symbol interference (ISI) in 5.9GHz Dedicated Short Range Communications (DSRC) systems. The physical layer (PHY) of DSRC is currently being developed by work group of IEEE 802.11p. The conventional system currently assumes static channel characteristics. Channel tracking schemes were investigated and the Viterbi-aided channel estimation scheme was proposed for DSRC systems that did not explicitly exploit the ICI components caused by the time-varying channels. The performance of the DSRC system is investigated for a time-varying channel using a conventional DSRC model, a decision-directed (Viterbi-aided) channel estimation model, and the frequency-domain equalization design. It is shown that the DSRC system with the frequency-domain equalization achieves a considerable performance enhancement compared to both the conventional and the Viterbi-aided channel estimation schemes in terms of both packet error rate (PER) and bit error rate (BER) at relatively high and low velocities. [Copyright &y& Elsevier]

Abstract: In this paper, Minimum Energy Dynamic Source Routing (MEDSR) and Hierarchical Minimum Energy Dynamic Source Routing (HMEDSR) protocols for Mobile Ad Hoc Networks (MANET) are proposed. The objective of MEDSR protocol is to reduce energy consumption in MANET while maintaining connectivity in the network. The objective of HMEDSR is to reduce the overhead of MEDSR. The overall result is that energy spent in transmitting overhead packets is reduced. This reduction allows more energy in transmitting data packets. The Dynamic Source Routing (DSR) protocol is modified to implement both MEDSR and HMEDSR protocols, and these implementations are tested with a network simulator (Network Simulator (NS-2)). The simulation results show that both MEDSR and HMEDSR protocols reduce energy consumption per data packet by 25% compared to DSR, but HMESDR further reduces energy consumption by 12% compared to MEDSR by controlling overhead packets. [Copyright &y& Elsevier]

Abstract: This paper introduces a game theoretic method, called forwarding dilemma game (FDG), which controls routing overhead in dense multi-hop wireless ad hoc networks. The players of the game are the wireless nodes with set of strategies {Forward, Not forward}. The game is played whenever an arbitrary node in the network receives a flooding packet. In FDG, every player needs to know the number of players of the game. That is why a neighbor discovery protocol (NDP) is introduced. In order for NDP to function, a field is attached to the flooding packets (routing overhead packets). The mixed strategy Nash equilibrium is used as a solution for the FDG. This provides the probability that the flooding packet would be forwarded by the receiver node. FDG with NDP is implemented in AODV protocol in Network Simulator NS-2 to verify its performance with simulations. FDG with NDP improves performance of the AODV compared to the same network with only AODV protocol in moderate and high node densities. FDG can be applied to any routing protocol that uses flooding in the route discovery phase. [Copyright &y& Elsevier]

Abstract: In this paper, we present a study of the dedicated short range communications (DSRC) receiver performance under varying signal to noise ratio, velocity, symbol durations and packet lengths. Conventional channel estimation, which is used in IEEE 802.11a, assumes static channel characteristics for the entire packet duration. That is found to be infeasible for high velocity DSRC applications. Simulation results show that the packet-error-rate increases with the increase in relative velocity. Viterbi decoding substantially improves the performance, but the sensitivity to Doppler shift still exists. Analysis and simulation results show that extending the symbol duration or increasing packet length results in an increase of the packet-error-rate. These results may serve as benchmarks for future DSRC channel estimation methods. [Copyright &y& Elsevier]