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ABSTRACT: Directional antennas have the considerable benefits of higher antenna gain, long transmission distance and spatial reuse compared to omni?antennas. To support a directional antenna, IEEE 802.15.3c specifies a high data transmission rate and short frequency range communication based on the characteristics of 60GHz band. However, the contention?based protocol of IEEE 802.15.3c may cause channel collisions and throughput degradation as the number of stations in the network increases. In order to resolve this problem and reduce channel access latency, we propose an adaptive allocation algorithm in which the contention window size for optimal transmission probability is derived after the directional information has been obtained by means of AP control procedures. Extensive simulations demonstrate that the proposed algorithm outperforms the existing channel access scheme in IEEE 802.15.3c wireless personal area networks under different situations, especially when the number of contending stations is large.
International Journal of Advanced Robotic Systems 04/2012; · 0.38 Impact Factor
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ABSTRACT: This paper presents an analytical model for the performance evaluation of an IEEE 802.11e network in non?saturation environments. We first characterize the probability distribution of the MAC layer packet service time. Based on the probability distribution model of the MAC layer packet service time, we then study the queuing performance of the wireless local area networks (WLANs) at different traffic loads based on the IEEE 802.11e MAC protocol. The numerical results show that we can choose a feasible number and bandwidth of the node which determines the system performance that a user demands.
International Journal of Advanced Robotic Systems 04/2012; · 0.38 Impact Factor
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ABSTRACT: Nowadays, with wireless sensor networks (WSNs) being widely applied to diverse applications, heterogeneous sensor networks (HSNs), which can simultaneously support multiple sensing tasks in a common sensor field, are being considered as the general form of WSN system deployment. In HSNs, each application generates data packets with a different size, thereby resulting in fairness issues in terms of the network performance. In this paper, we present the design and performance evaluation of a differentiated channel access scheme (abbreviated to DiffCA) to resolve the fairness problem in HSNs. DiffCA achieves fair performance among the application groups by providing each node with an additional backoff counter, whose value varies according to the size of the packets. A mathematical model based on the discrete time Markov chain is presented and is analyzed to measure the performance of DiffCA. The numerical results show that the performance degradation of disadvantaged application groups can be effectively compensated for by DiffCA. Simulation results are given to verify the accuracy of the numerical model.
Sensors 01/2011; 11(7):6629-44. · 1.74 Impact Factor
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IEICE Transactions. 01/2010; 93-B:1016-1019.
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NBiS 2009, 12th International Conference on Network-Based Information Systems, Indianapolis, Indiana, USA, 19-21 August 2009; 01/2009
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ABSTRACT: This paper describes an energy-efficient BOP-based beacon transmission scheduling (EBBS) algorithm. EBBS is the centralized approach, in which a resource-sufficient node called as Topology Management Center (TMC) allocates the time slots to transmit a beacon frame to the nodes and manages the active/sleep schedules of them. We also propose EBBS with Adaptive BOPL (EBBS-AB), to adjust the duration to transmit beacon frames in every beacon interval, adaptively. Simulation results show that by using the proposed algorithm, the energy efficiency and the throughput of whole network can be significantly improved. EBBS-AB is also more effective for the network performance when the nodes are uniformly deployed on the sensor field rather than the case of random topologies.
Personal, Indoor and Mobile Radio Communications, 2008. PIMRC 2008. IEEE 19th International Symposium on; 10/2008
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ABSTRACT: We propose an opportunistic transmission strategy for wireless sensor networks (WSNs) that operate in a strict energy-constrained environment. Our proposed transmission strategy named binary-decision based transmission (BDT) attempts to transmit at good channel conditions while meeting the delay constraint for delay-sensitive applications and the buffer size constraint for non-delay-sensitive applications, under time- varying wireless channel. The Markov decision process (MDP) is used to find an optimum threshold for transmission decision. Our BDT scheme initiates transmission only when the channel quality exceeds the optimum threshold, so that unsuccessful transmissions causing a waste of energy are avoided whenever possible.
Communications, 2008. ICC '08. IEEE International Conference on; 06/2008
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IEICE Transactions. 01/2008; 91-B:3469-3479.
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ABSTRACT: Many applications in wireless sensor networks (WSNs) require the energy efficiency and scalability. Although IEEE 802.15.4/Zigbee which is being considered as general technology for WSNs enables the low duty-cycling with time synchronization of all the nodes in network, it still suffer from its low scalability due to the beacon frame collision. Recently, various algorithms to resolve this problem are proposed. However, their manners to implement are somewhat ambiguous and the degradation of energy/communication efficiency is serious by the additional overhead. This paper describes an Energy-efficient BOP-based Beacon transmission Scheduling (EBBS) algorithm. EBBS is the centralized approach, in which a resource-sufficient node called as Topology Management Center (TMC) allocates the time slots to transmit a beacon frame to the nodes and manages the active/sleep schedules of them. We also propose EBBS with Adaptive BOPL (EBBS-AB), to adjust the duration to transmit beacon frames in every beacon interval, adaptively. Simulation results show that by using the proposed algorithm, the energy efficiency and the throughput of whole network can be significantly improved. EBBS-AB is also more effective for the network performance when the nodes are uniformly deployed on the sensor field rather than the case of random topologies.
