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Xu N.,Zhejiang University | Huang A.,Zhejiang University | Huang A.,Zhejiang Provincial Key Laboratory of Information Network Technology | Hou T.-W.,National Cheng Kung University | Chen H.-H.,National Cheng Kung University
Wireless Communications and Mobile Computing | Year: 2012

One of the most challenging issues in wireless sensor networks is to meet the requirements of coverage and connectivity under given energy constraints. Most existing coverage and connectivity algorithms work to form tree networks when sensor nodes do not have location information of themselves. However, a tree topology network does not perform well in terms of energy efficiency and scalability if compared with a cluster network. In this paper, a novel topology control algorithm called Adaptive Random Clustering (ARC) is proposed to form a cluster network with required coverage and connectivity without location information. The performance of its coverage intensity and connectivity is analyzed based on the characteristics of cluster topology, and their proper parameters are determined. ARC inherits an excellent energy efficiency from cluster topology and avoids the collisions and overhearing of data packets. A good scalability can be achieved as only a limited number of channels are needed in ARC for a large-scale network. Furthermore, ARC can adjust the number of active nodes adaptively according to the required coverage to balance the energy consumption. Simulation results demonstrate that required coverage and connectivity can be satisfied and network lifetime is prolonged significantly. Copyright © 2010 John Wiley & Sons, Ltd. Source

Wang J.,Zhejiang University | Huang A.,Zhejiang University | Huang A.,Zhejiang Provincial Key Laboratory of Information Network Technology | Wang W.,Zhejiang University | And 2 more authors.
International Journal of Communication Systems | Year: 2014

The characteristics of cognitive radio networks have huge impacts on the end-to-end performance of the transmission control protocol (TCP) for secondary users. Thus, the existing TCP throughput expression, widely used in wired and wireless networks, is no longer suitable for cognitive radio networks. In this paper, we derive the transmission opportunity of secondary users, taking into account the dynamics of spectrum availability, the overhead and errors of spectrum sensing, as well as the interaction between TCP and lower layers. The amount of transmission opportunity is expressed in terms of effective data transmission time. On the basis of the analysis of the transmission opportunity, an expression of an effective TCP throughput is then derived. To evaluate this effective TCP throughput expression, two cross-layer optimization problems are formulated as application examples to maximize the transport layer effective throughput and energy utility, respectively. Simulation results show that our analysis on transmission opportunity is accurate, and the derived effective TCP throughput expression is more precise than existing ones. Copyright © 2012 John Wiley & Sons, Ltd. Source

Zhang J.,Zhejiang University | Zhang Z.,Zhejiang University | Zhang Z.,Zhejiang Provincial Key Laboratory of Information Network Technology | Luo H.,Zhejiang University | And 2 more authors.
International Journal of Communication Systems | Year: 2012

In this paper, an initial spectrum access control algorithm for cognitive wireless networks was studied. The objective was to maximize the number of admitted secondary users (SUs) under the constraints of interference temperature at multiple measurement points (MPs), while providing active SUs' QoS protection (AQP). Here, AQP means that the signal-to-interference-plus-noise ratios (SINRs) of all active SUs will not fluctuate below some predefined thresholds during a new SU's initial spectrum access process. To this end, we proposed a new distributive power control algorithm in conjunction with a simple alarm mechanism that ensures the interference temperatures at multiple MPs to be always below their thresholds during the initial spectrum access process. Then, two realizations of the spectrum access algorithms, namely, D-AQP and C-AQP, according to whether the MPs can act as local controllers or not, were presented. In the D-AQP algorithm, each SU updates its transmit power distributively based on the local information including the current SINR, the QoS requirement, and the indicator from the MPs so that the resultant SINRs of the active SUs are able to stay above the predefined thresholds. Whereas in the C-AQP algorithm, apart from the same procedure as mentioned, each MP is supposed to be able to decide which new SU should quit the initial spectrum access process so as to protect the communication quality of the primary system. Finally, the performances of the proposed algorithms were validated by extensive simulations. Copyright © 2011 John Wiley & Sons, Ltd. Source

Bao P.,Zhejiang University | Yu G.,Zhejiang University | Yu G.,Zhejiang Provincial Key Laboratory of Information Network Technology | Yin R.,Zhejiang University
2013 9th International Wireless Communications and Mobile Computing Conference, IWCMC 2013 | Year: 2013

In this paper, the interference mitigation problem in device-to-device (D2D) communication underlaying cellular networks using fractional frequency reuse (FFR) is studied. For such system, we propose a location based channel reusing scheme in which the D2D users in the inner region have a chance to reuse the channel resources of cellular users in the outer region of neighboring cells, and the D2D users in the outer region could reuse the channel resources of particular cellular users in the inner region of the same cell. Two novel concepts are introduced, namely the accessible region and the reusable region. To protect the outage probabilities of both cellular links and D2D links, only the D2D users in the accessible region could reuse the channel resources of cellular users in the reusable region. We present a specific method to calculate the boundary of the accessible region, as well as the reusable region. Simulation results demonstrate that the proposed scheme could effectively alleviate the interference between both users. © 2013 IEEE. Source

Hu Q.,Wenzhou University | Hu Q.,Zhejiang Provincial Key Laboratory of Information Network Technology | Tian Q.,De Zhou Vocational and Technical College | Tang Z.,Wenzhou University
International Journal of Wireless Information Networks | Year: 2013

Idle listening is one of the main factors for energy consumption in wireless sensor networks, and the duty cycle mechanism is widely used to reduce idle listening. In this paper, we present a new receiver-initiated duty cycling MAC protocol for wireless sensor networks, called reordering-passive MAC (RP-MAC), which includes receiver wake-up time estimation scheme and frame reordering scheme. We evaluate the performance of RP-MAC in ns-2 network simulator, and the simulation results shows that RP-MAC achieves higher energy efficiency, higher network throughput and lower end-to-end delay compared to other passive protocols, especially in case of heavy traffic or low duty cycle. © 2012 Springer Science+Business Media, LLC. Source

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