Showing papers in "Wireless Communications and Mobile Computing in 2008"

Security in wireless sensor networks

Abstract: With sensor networks on the verge of deployment, security issues pertaining to the sensor networks are in the limelight. Though the security in sensor networks share many characteristics with wireless ad hoc networks, the two fields are rapidly diverging due to the fundamental differences between the make-up and goals of the two types of networks. Perhaps the greatest dividing difference is the energy and computational abilities. Sensor nodes are typically smaller, less powerful, and more prone to failure than nodes in an ad hoc network. These differences indicate that protocols that are valid in the context of ad-hoc networks may not be directly applicable for sensor networks. In this paper, we survey the state of art in securing wireless sensor networks. We review several protocols that provide security in sensor networks, with an emphasis on authentication, key management and distribution, secure routing, and methods for intrusion detection. Copyright © 2006 John Wiley & Sons, Ltd.

Increasing network lifetime by balancing node energy consumption in heterogeneous sensor networks

Abstract: Sensor nodes are powered by battery and have severe energy constraints. The typical many-to-one traffic pattern causes uneven energy consumption among sensor nodes, that is, sensor nodes near the base station or a cluster head have much heavier traffic burden and run out of power much faster than other nodes. The uneven node energy dissipation dramatically reduces sensor network lifetime. In a previous work, we presented the chessboard clustering scheme to increase network lifetime by balancing node energy consumption. To achieve good performance and scalability, we propose to form a heterogeneous sensor network by deploying a few powerful high-end sensors in addition to a large number of low-end sensors. In this paper, we design an efficient routing protocol based on the chessboard clustering scheme, and we compute the minimum node density for satisfying a given lifetime constraint. Simulation experiments show that the chessboard clustering-based routing protocol balances node energy consumption very well and dramatically increases network lifetime, and it performs much better than two other clustering-based schemes. Copyright © 2006 John Wiley & Sons, Ltd.

Pervasive data access in wireless and mobile computing environments

Abstract: The rapid advance of wireless and portable computing technology has brought a lot of research interests and momentum to the area of mobile computing. One of the research focus is on pervasive data access. With wireless connections, users can access information at any place at any time. However, various constraints such as limited client capability, limited bandwidth, weak connectivity, and client mobility impose many challenging technical issues. In the past years, tremendous research efforts have been put forth to address the issues related to pervasive data access. A number of interesting research results were reported in the literature. This survey paper reviews important works in two important dimensions of pervasive data access: data broadcast and client caching. In addition, data access techniques aiming at various application requirements (such as time, location, semantics and reliability) are covered. Copyright © 2006 John Wiley & Sons, Ltd.

Analytical modeling of MAC protocol in ad hoc networks

Abstract: In ad hoc networks, CSMA/CA is a widely used MAC layer protocol. There has been considerable work on the performance evaluation of this protocol. But most work is confined to saturation performance of single-hop ad hoc networks. In this paper, we employ a linear feedback model to evaluate the performance for CSMA/CA according to the Poisson distributed traffic in both single-hop and multi-hop ad hoc networks. To the best of our knowledge, this is the first attempt to analytically evaluate the performance for CSMA/CA protocol under a general assumption about the traffic. This paper also gives analytical results, showing the impact of RTS/CTS. Although RTS/CTS do add the overhead to the system, they become essential when either the hidden terminal problem is dominant, or the traffic is heavy, or the packet length is very large. This paper also shows that the performance degrades dramatically in multi-hop ad hoc networks when the number of competing nodes increases, which implies that the scalability is still a major problem in ad hoc networks. To validate our analytical results, we have done extensive simulations, and it is observed that the simulation results match the analytical results very well. Copyright © 2006 John Wiley & Sons, Ltd.

Sustained service lookup in areas of sudden dense population

Abstract: As mobility became the norm rather than the exception, location-based services are playing more of a key role in assisting mobile users. In this paper, we address the challenges of providing location-based services to users in areas of sudden population increases, such as stadiums and traffic jams. A sudden increase in the number of mobile users leads to an increasing demand for the already scarce wireless bandwidth, thus causing dramatical throughput degradation and an increase in connectivity failures. We propose a hybrid model within which a peer-to-peer mode is deployed to assist the cellular-based network whenever a sudden increase in population density is sensed by the base station. Location-based data is migrated to selected elite nodes, thus allowing other peer nodes to get their information locally. This approach is proven, through experimental results, to decrease the query response time and number of query failures. Copyright © 2006 John Wiley & Sons, Ltd.

Prospects and problems of wireless communication for underwater sensor networks

Abstract: This paper reviews the physical fundamentals and engineering implementations for efficient information exchange via wireless communication using physical waves as the carrier among nodes in an unde...

Bit error rate for rectangular QAM with arbitrary constellation mapping in Nakagami-m channels

Abstract: We present closed-form expressions for the bit error rate (BER) of rectangular quadrature amplitude modulation (QAM) in Nakagami-m fading channels. The presented formulas, which are valid for arbitrary bits-to-symbols mapping, thus may be used when non-Gray mapping is employed, are particularly useful in the low signal-to-noise ratio (SNR) range and/or for small values of the parameter m. The advantage of the proposed expressions over the known bounding techniques is illustrated through numerical simulations. Copyright © 2006 John Wiley & Sons, Ltd.

Distance bounding protocols for RFID enhanced by using void-challenges and analysis in noisy channels

Abstract: RFID systems are vulnerable to different attacks related to the location; distance fraud attack, relay attack and terrorist attack. The main countermeasure against these attacks is the use of proto...

A mutual authentication and privacy mechanism for WLAN security

Abstract: IEEE 802.11 wireless local area networks (WLAN) has been increasingly deployed in various locations because of the convenience of wireless communication and decreasing costs of the underlying technology. However, the existing security mechanisms in wireless communication are vulnerable to be attacked and seriously threat the data authentication and confidentiality. In this paper, we mainly focus on two issues. First, the vulnerabilities of security protocols specified in IEEE 802.11 and 802.1X standards are analyzed in detail. Second, a new mutual authentication and privacy scheme for WLAN is proposed to address these security issues. The proposed scheme improves the security mechanisms of IEEE 802.11 and 802.1X by providing a mandatory mutual authentication mechanism between mobile station and access point (AP) based on public key infrastructure (PKI), offering data integrity check and improving data confidentiality with symmetric cipher block chain (CBC) encryption. In addition, this scheme also provides some other new security mechanisms, such as dynamic session key negotiation and multicast key notification. Hence, with these new security mechanisms, it should be much more secure than the original security scheme. Copyright © 2006 John Wiley & Sons, Ltd.

Power control and scheduling for guaranteeing quality of service in cellular networks

Abstract: Providing quality of service (QoS) guarantees is important in the third generation (3G) and the fourth generation (4G) cellular networks. However, large-scale fading and non-stationary small-scale fading can cause severe QoS violations. To address this issue, we design QoS provisioning schemes, which are robust against time-varying large scale path loss, shadowing, non-stationary small scale fading, and very low mobility. In our design, we utilize our recently developed effective capacity technique and the time-diversity dependent power control proposed in this paper. The key elements of our QoS provisioning schemes are channel estimation, power control, dynamic channel allocation, and adaptive transmission. The advantages of our QoS provisioning schemes are (1) power efficiency, (2) simplicity in QoS provisioning, (3) robustness against large-scale fading and non-stationary small-scale fading. Simulation results demonstrate that the proposed algorithms are effective in providing QoS guarantees under various channel conditions. Copyright © 2006 John Wiley & Sons, Ltd.

Outage probability analysis of antenna array using maximum ratio combining in spherically invariant fading environment

Abstract: In this paper, the outage probability of maximum ratio combining (MRC) in the spherically invariant fading environment was analyzed. The study was done with and without consideration of the effect of noise. First, the probability density functions (pdf) of signal-to-interference plus noise ratio (SINR) and signal-to-interference ratio (SIR) were derived. In our derivation, the characteristic pdfs of spherically invariant random process (SIRP) corresponding to the interferences were assumed to be both different and identical. Moreover, both equal and different mean powers of interferences were considered. With the derived pdfs of SINR and SIR, the expressions of outage probability were computed. Numerical analysis was done using three numerical methods known as Gauss–Laguerre, Gauss–Hermite, and Gauss–Legendre integrations. It should be noted that SIRP, the generalization of Gaussian random process, is assumed to have K-distribution, which is the generalization of Rayleigh. Our analysis was verified by comparing the outage probabilities of the considered environments with those of Rayleigh fading channel. From the numerical results, the derived outage probability converges to that of Rayleigh fading, when the shape parameter of characteristic pdf approaches infinity. Copyright © 2006 John Wiley & Sons, Ltd.

An approximation and its applications in wireless networks performance analysis

Abstract: In the literature, there are two common assumptions for the tele-traffic parameter in analyzing the wireless network performance, that is, the tele-parameter follows a specific probability density function (pdf) and additionally the pdf exists closed-form Laplace Transform (LT). However, taking into account the cell irregular shape, the specific pdf may be unavailable while only the measured statistical moments are available. Moreover, the pdf function may not exist a closed-form LT, for example, lognormal distribution function. In this paper, based on the Central Limit Theorem and hyper-Erlang universal approximation property, we propose an approximation method applicable in the situations when only the statistical moments are available or LT of pdf does not exist. We then employ the technique in diverse applications, including the performance analysis of wireless network and the cost evaluation of mobility management. Extensive numerical examples demonstrate the good approximation capability to the exact formula and the simulation results. Copyright © 2006 John Wiley & Sons, Ltd.