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The stationary signal-strength-difference (SSSD)-based positioning technique has been proposed as a cost-effective, low-complexity solution. The positioning accuracy with this technique, however, is limited, as a result of the large error in the distance. In this paper, we contribute a simple and efficient method for the accuracy improvement issues in the distance. Starting from the concept of the Global Positioning System (GPS) pseudorange (PD) equation, a complete set of distance difference (DD) is formulated. In addition, we then correct the error in the distance by going in the set of DD, based on the least-squares (LS) sense. The theoretical model is established and verified via experimental data gathered in an urban environment. Results clearly show that the proposed method performs well when encountering a large error in the distance. On top of this, we investigate the accuracy improvement issues in the location estimation and propose an iterative LS algorithm by using the corrected distances. The positioning accuracy is studied based on the analysis of different location errors, and the effect of geometric dilution of precision (GDOP) is also investigated. The improvement of the positioning accuracy is clearly demonstrated through the experimental data collected at 55 different test points with 25 133 samples, which is outstanding. [ABSTRACT FROM AUTHOR]

This paper presents efficient dynamic resource allocation schemes with interference mitigation techniques for multimedia services in downlink orthogonal frequency-division multiplexing mobile cellular systems. Performance of the proposed algorithms is evaluated in terms of user quality-of-service and system spectral efficiency. It is shown that the best subcarrier allocation scheme with interference mitigation and macrodiversity techniques gives significant performance gains in terms of system spectral efficiency. Furthermore, sharing the system bandwidth among real-time stream-type voice and bursty data services can support much larger system loads than having a hard division. [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]

In this paper, we consider the problem of blind channel estimation for single-input-single-output (SISO) orthogonal frequency-division multiplexing (OFDM) system via second-order statistics only. Based on the assumption that the transmitted symbols are independent and identically distributed, we develop a simple blind channel estimation technique for OFDM systems by utilizing a generalized linear nonredundant block precoding. Instead of using partial information from the signal covariance matrix, as done in previous works where a specific precoder is designed and only one column of the signal covariance matrix is exploited, our work jointly considers all the information contained in the signal covariance matrix. Compared to the popular subspace-based blind channel estimation methods, the proposed algorithm is much more computationally efficient. A design criterion of the precoders by which the performance can be improved is provided, and the closed-form stochastic Cramér-Rao bound is derived. The numerical results clearly show the effectiveness of our proposed algorithm, as well as its improvement over the existing techniques. [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]