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Energy constraints have a significant impact on the design and operation of wireless sensor networks. This paper investigates the base station (BS) selection (or anycast) problem in wireless sensor networks. A wireless sensor network having multiple BSs (data sink nodes) is considered. Each source node must send all its locally generated data to only one of the BSs. To maximize network lifetime, it is essential to optimally match each source node to a particular BS and find an optimal routing solution. A polynomial time heuristic is proposed for optimal BS selection and anycast via a sequential fixing procedure. Through extensive simulation results, it is shown that this algorithm has excellent performance behavior and provides a near-optimal solution. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of two control parameters of the Universal Mobile Telecommunications System (UMTS) handoff algorithm on the total peak base station (BS) transmit power required per mobile station (MS) to satisfy a prescribed outage probability. Denoting the set of BSs supporting an MS in soft handoff (SH) as the active group, the first parameter n is the maximum allowed size of the active group. The second, denoted r, is the upper limit on the difference between the path loss of the dominant BS and that of any other member of the active group, where the term "dominant" refers to the BS with the lowest path loss to the MS. It was assumed that the MS is equipped with a Rake receiver capable of performing "maximal ratio combining" of the signals it receives from the transmitting BSs. General analytical derivations along with results derived for specific situations through numerical integration are presented. [ABSTRACT FROM AUTHOR]

In this paper, we present a unified approach for the computation of the outage probability, the level crossing rate (LCR), and the average outage duration (AOD) of selection combining (SC) in the presence of multiple cochannel interferences and under both minimum signal-to-interference ratio (SIR) and desired signal power constraints. We consider three selection algorithms, namely, 1) the best signal power algorithm; 2) the best SIR algorithm; and 3) the best total power (desired plus interference) algorithm. As a specific application example, we analyze the three algorithms for a low-complexity dual-branch SC receiver subject to multiple interferers over Rayleigh fading channels. When applicable, the new results are compared to those previously reported in the literature dealing with the outage probability, AOD, and LCR of 1) interference-limited systems and 2) power-limited systems. Numerical examples show that the minimum desired signal power constraint induces a floor to the outage probability, AOD, and LCR performance measures. They also show that the best SIR algorithm provides the best outage probability and AOD performance for low average SIR. On the other hand, the best signal power algorithm and the best S + I algorithm outperform the best SIR algorithm for high average SIR. It is also shown that the best SIR algorithm tends to have more outage level crossings. [ABSTRACT FROM AUTHOR]

This paper deals with a class of power control problems where the system link gains are assumed to be time varying and the signal-to-interference ratio (SIR) estimates are allowed to be corrupted with bounded noises. A simple control algorithm is devised by applying a distributed, fixed step approach. It is a feedback algorithm that requires only local information. By modifying the distributed, fixed step power control algorithm proposed by Sung and Wong, we obtain here a more robust version that can handle time varying link gains and measurement noises. The convergence property of the new algorithm is established and simulation studies were carried out to show that it is effective. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach for designing a call-admission control (CAC) algorithm for code-division multiple-access CDMA) networks with arbitrary call-arrival rates. The. design of the CAC algorithm uses global information; it incorporates e call-arrival rates and the user mobilities across the network and guarantees the users' quality of service (QoS) as well as prespecific blocking probabilities. On the other hand, its implementation in each cell uses local information; it only requires the number f calls currently active in that cell. We present several cases for a nontrivial network topology where our CAC algorithm guarantees QoS and blocking probabilities while achieving significantly higher throughput than that achieved by traditional techniques. We so calculate the network capacity, i.e., the maximum throughput f r the entire network, for prespecified blocking probabilities and QoS requirements. [ABSTRACT FROM AUTHOR]

This paper provides mobility estimation and pree-diction for a variant of the GSM network that resembles an ad hoc wireless mobile network in which base stations and users are both mobile. We propose using a Robust Extended Kalman Filter (REKF) to derive an estimate of the mobile user's next mobile base station from the user's location, heading, and altitude, to improve connection reliability and bandwidth efficiency of the underlying system. Our analysis demonstrates that our algorithm can successfully track the mobile users with less system complexity, as it requires measurements from only one or two closest mobile base stations. Further, the technique is robust against system uncertainties caused by the inherent deterministic nature of the mobility model. Through simulation, we show the accuracy of our prediction algorithm and the simplicity of its implementation. [ABSTRACT FROM AUTHOR]

Power control has been widely studied and shown to be crucial for the capacity and performance of direct-sequence code-division multiple-access (DS-CDMA) systems. Practical implementations typically employ fast closed-loop power control, where transmitters adjust their transmit powers according to commands received in a feedback channel. The loop delay resulting from the measurements, processing, and transmission of the power control commands can result in oscillations of the transmission powers and lead to degradation in the system performance. In this paper we present new adaptive closed-loop power control algorithms that are able to alleviate the effect of the loop delay. The algorithms are based on self-tuning controllers designed for a log-linear model of the power control process. We carried out computational experiments on a DS-CDMA network using the distributed constrained power control (DCPC) as a reference algorithm. Practical versions of the algorithms are also provided and they were compared with the fixedstep power control (FSPC) algorithm employed in the IS-95 and WCDMA systems. The numerical results indicate that our algorithms can significantly improve the radio network capacity without any increase in power control signaling. [ABSTRACT FROM AUTHOR]

Positioning algorithms in cellular networks has become increasingly important as a means of supporting emerging services that require a sufficiently precise estimation of the position of the mobile terminal (MT) associated with a given base station (BS). Currently, even the most sophisticated positioning algorithms require at least three BSs to achieve satisfactory precision. This paper presents a novel algorithm that makes use of a single-BS antenna array to locate MTs in cellular networks. A triangulation technique is utilized and supported by some minimal information about the environment in the BS neighborhood. This algorithm is shown to perform well when operating in a microcellular environment with perfect channel-parameter estimation. The effect of finite resolution of the input parameters is also investigated. The performance is analyzed for a universal mobile telecommunications system microcellular scenario through a three-dimensional deterministic channel model. Finally, the performance of the proposed positioning technique is compared to the well-known location method based on the time-of-arrival measurements at three different BSs. [ABSTRACT FROM AUTHOR]

One of the main problems facing accurate location in wireless communication systems is nonline-of-sight (NLoS) propagation. In this paper, we propose a novel location technique that estimates the true, or line-of-sight (LoS), ranges based on NLoS range measurements. This approach utilizes a constrained nonlinear optimization approach, when range measurements are available from three base stations (BSs) only. Bounds on the NLoS error and the relationship between the true ranges are extracted from the geometry of the cell layout and the measured range circles to serve as constraints. Simulations studying the performance of the algorithm for different NLoS error distributions and BS configurations show that the location accuracy is significantly improved over traditional algorithms, even under highly NLoS conditions. [ABSTRACT FROM AUTHOR]

Quality-of-service (QoS) routing is the key to support multimedia services in wireless multihop networks. The goal of QoS routing is to find satisfactory paths that support the end-to-end QoS requirements of the multimedia flows. Previous work has demonstrated a framework for supporting QoS muting in mobile ad hoc networks, where two novel mechanisms for dynamic channel assignment, called the minimum-blocking and bandwidth-reallocation channel-assignment (MBCA/BRCA) algorithms, were proposed. MBCA/BRCA are on-demand channel assignment methods that reactively provide a differentiated service treatment to multimedia traffic flows at the link level using novel techniques for end-to-end path QoS maximization. Efficient QoS routing is then accomplished by giving the muting mechanism access to QoS information, thus coupling the coarse grain (routing) and fine grain (congestion control) resource allocation. In this paper, the specifics and individual mechanisms of the MBCA/BRCA algorithms are presented, whereas their effectiveness and the manner in which they interact in order to contribute to the overall protocol performance is examined and documented. The system performance is studied through simulations experiments under various QoS traffic flows and network scenarios. The protocol's behavior and the changes introduced by variations on some of the mechanisms that make up the protocol is further investigated. As demonstrated, the MBCA/BRCA methods are able to increase system's aggregate traffic by 2.8 Kb/s, on average, comparing to a non-MBCA/BRCA dynamic channel-allocation scheme. [ABSTRACT FROM AUTHOR]

In power control, the convergence rate is one of the most important criteria that can determine the practical applicability of a given algorithm. The Convergence rate of power control is especially important when propagation and traffic conditions are changing rapidly. To track these changes, the power control algorithm must converge quickly. The purpose of this paper is to generalize the existing power control framework such that we can utilize partially known link gain information in improving the convergence speed. For the purpose, block power control (BPC) is suggested with its convergence properties. BPC is centralized within each block in the sense that it exchanges link gain information within the same block. However, it is distributed in a block-wise manner, and no information is exchanged between different blocks. Depending on availability of link gain information, a block can be any set of users, and can even consist of a single user. Computational experiments are carried out on a direct-sequence code-division multiple-access system, illustrating how BPC utilizes available link gain information in increasing the convergence speed of the power control. [ABSTRACT FROM AUTHOR]