Search

In this paper, novel equalization algorithms for continuous phase modulations (CPMs) are illustrated. Both conventional (linear and decision-feedback) and turbo equalization techniques are derived using the Laurent decomposition of CPM signals. All of them operate in the frequency domain and process two samples of the received signal per channel symbol. Numerical results show that on one hand, conventional equalization strategies offer good performance for binary partial response signaling over severely frequency-selective wireless channels at a moderate complexity. On the other hand, there is evidence that turbo techniques provide a small energy saving at the price of a substantial computational burden. Index Terms--Continuous phase modulation (CPM), decision-feedback equalization (DFE), frequency-domain equalization, linear equalization, turbo equalization.

In this paper, channel equalization algorithms processing two samples of the received signal per channel symbol and operating in the frequency domain are described in a unifying framework. First, minimum mean-square error linear and decision-feedback equalizers are derived, and a synthesis technique based on the well-known Levinson-Durbin algorithm is proposed for the latter. Then, iterative linear and decision-feedback equalization algorithms for turbo processing are devised. Performance results for both uncoded and coded phase-shift keying transmissions show the efficacy of the proposed equalization techniques and their superiority over other existing frequency-domain equalization strategies. Index Terms--Decision-feedback equalization, frequency-domain equalization (FDE), multipath channel, turbo equalization.

In this paper, a novel feedback frequency synchronizer for orthogonal frequency-division multiplexing signals transmitted over multipath fading channels is described. Its derivation is based on maximum-likelihood estimation techniques and assumes an approximate statistical knowledge of the communication channel. The performance of the proposed algorithm is assessed by computer simulation, and is compared with that provided by other synchronization algorithms and with Cramer-Rao bounds. Index Terms--Fading channels, frequency synchronization, maximum-likelihood (ML) estimation, multicarrier modulation, orthogonal frequency-division multiplexing (OFDM).

In this paper, some novel results on the space-time differential modulation schemes described by Hochwald and Sweldens, and Tarokh and Jafarkhani, are derived under the assumption of a quasi-static multiple-antenna channel. First, the optimality (in the maximum-likelihood sense) of the one-shot detection algorithms of Hochwald and Sweldens, and Tarokh and Jafarkhani, is proved. Then the expression of the pairwise error probability for these detectors is derived, and, as a particular case, the bit-error rate is computed for the binary phase-shift keyed scheme of Tarokh and Jafarkhani. Finally, a per-survivor processing (PSP) detection algorithm for this class of modulations is illustrated. Numerical results evidence both the superiority of the PSP strategy over the one-shot space-time differential detectors and the accuracy of the above-mentioned bit-error rate formula. Index Terms--Maximum-likelihood detection, per-survivor processing (PSP), space-time coding, Viterbi algorithm.

Recently, the need of deploying new wireless networks for smart gas metering has raised the problem of radio planning in the 169 MHz band. Unluckily, software tools commonly adopted for radio planning in cellular communication systems cannot be employed to solve this problem because of the substantially lower transmission frequencies characterising this application. In this study, a novel data-centric solution, based on the use of support vector machine techniques for classification and regression, is illustrated. The proposed method requires the availability of a limited set of received signal strength measurements and the knowledge of a three-dimensional map of the propagation environment of interest and generates both an estimate of the coverage area and a prediction of the field strength within it. Various numerical results show that the proposed method is able to achieve good accuracy at the price of an acceptable computational cost and of a limited effort for the acquisition of measurements in the considered environments. [ABSTRACT FROM AUTHOR]

In this paper, the well known Zadeh’s series representation of a linear periodically time varying system is exploited to develop linear equalization techniques for narrowband powerline communications based on orthogonal frequency division multiplexing. Numerical and experimental results referring to the band 200–500 kHz evidence that a coherent receiver exploiting the proposed equalizers can significantly outperform both its counterpart based on conventional channel estimation/equalization techniques and differential detection with a limited complexity. This leads to the conclusion that a coherent receiver incorporating the proposed equalization techniques represents a technically appealing solution for narrowband high data rate powerline communications in indoor scenarios. [ABSTRACT FROM PUBLISHER]

The problem of bit and power loading for bit rate maximization in orthogonal frequency division multiplexing data communications over indoor powerline channels is investigated, and a simple method for bit/power allocation in half a cycle of the mains is developed. The proposed solution is based on the so-called Zadeh’s representation for modeling the linear periodically time-varying behavior of powerline channels. Numerical results show the superiority of the proposed method over other solutions available in the technical literature in a real-world scenario. [ABSTRACT FROM AUTHOR]

The knowledge of environmental maps (i.e., map-awareness) can appreciably improve the accuracy of optimal methods for position estimation in indoor scenarios. This improvement, however, is achieved at the price of a significant complexity increase with respect to the case of map-unawareness, specially for large maps. This is mainly due to the fact that optimal map-aware estimation algorithms require integrating highly nonlinear functions or solving nonlinear and nonconvex constrained optimization problems. In this paper, various techniques for reducing the complexity of such estimators are developed. In particular, two novel strategies for restricting the search domain of map-aware position estimators are developed and the exploitation of state-of-the-art numerical integration and optimization methods is investigated; this leads to the development of a new family of suboptimal map-aware localization algorithms. Our numerical and experimental results evidence that the accuracy of these algorithms is very close to that offered by their optimal counterparts, despite their significantly lower computational complexity. [ABSTRACT FROM AUTHOR]

In this paper, the impact of statistical noise modelling on the error performance achieved by orthogonal frequency-division multiplexing (OFDM) over indoor broadband power-line channels is investigated. Different classes of statistical models suitable to represent power-line noise are illustrated and their impact on the error performance of a specific OFDM system is assessed via computer simulations. Numerical results are compared with the error performance provided by the same system in the presence of measured power-line noise; this is evidence that a realistic indication of error performance can be achieved only if the power spectral density of the adopted noise model exhibits a good match with that of the measured noise. In practice, this result can be achieved by modeling the power-line noise as a moving average random process of proper order; however, a satisfying match can be achieved as well if other simple noise models available in the technical literature are adopted. [ABSTRACT FROM AUTHOR]

Indoor powerline channels usually exhibit a cyclic input–output behavior due to the time-varying impedance of power loads. This makes typical time-invariant system models unsuitable to provide a faithful representation of such channels. In this paper, starting from the so-called Zadeh's series expansion, a discrete-time parametric representation of a linear periodically time-varying system is developed, and it is shown how a reduced-complexity version of it can be adopted to model indoor powerline channels. Then, various methods for estimating the parameters of the proposed representation are developed and compared in terms of performance and complexity. Numerical results evidence that our reduced complexity model is able to provide an accurate representation of indoor powerline channels and is of practical interest for both smart-grid applications and home area networks. [ABSTRACT FROM AUTHOR]

The accuracy of indoor wireless localization systems can be substantially enhanced by map-awareness, i.e., by the knowledge of the map of the environment in which localization signals are acquired. In fact, this knowledge can be exploited to cancel out, at least to some extent, the signal degradation due to propagation through physical obstructions, i.e., to the so called non-line-of-sight bias. This result can be achieved by developing novel localization techniques that rely on proper map-aware statistical modelling of the measurements they process. In this manuscript a unified statistical model for the measurements acquired in map-aware localization systems based on time-of-arrivaland received signal strength techniques is developed and its experimental validation is illustrated. Finally, the accuracy of the proposed map-aware model is assessed and compared with that offered by its map-unaware counterparts. Our numerical results show that, when the quality of acquired measurements is poor, map-aware modelling can enhance localization accuracy by up to 110% in certain scenarios. [ABSTRACT FROM PUBLISHER]

Estimating the input-output behavior of low voltage powerline channels for indoor high speed data communications requires the availability of proper wideband channel sounding tools. In fact, the properties of real world powerline channels are substantially different from those commonly exhibited by their wireless counterparts, so that standard methods for wireless channel sounding cannot be adapted to a powerline scenario. In this paper, after providing some general design guidelines for powerline channel sounding, a detailed description of a FPGA-based implementation of a wideband powerline channel sounder is provided. Such a tool is based on low cost hardware and is flexible, since it can be easily customized to user needs using a set of simple graphical user interfaces. Some of its specific applications, namely the estimation of the time-varying transfer function of an indoor powerline channel and the evaluation of the power spectral density of the noise affecting it, are illustrated to show the potentialities of the developed equipment. [ABSTRACT FROM PUBLISHER]

Establishing bounds on the accuracy achievable by localization techniques represents a fundamental technical issue. Bounds on localization accuracy have been derived for cases in which the position of an agent is estimated on the basis of a set of observations and, possibly, of some a priori information related to them (e.g., information about anchor positions and properties of the communication channel). In this paper, new bounds are derived under the assumption that the localization system is map-aware, i.e., it can benefit not only from the availability of observations, but also from the a priori knowledge provided by the map of the environment where it operates. Our results show that: a) map-aware estimation accuracy can be related to some features of the map (e.g., its shape and area) even though, in general, the relation is complicated; b) maps are really useful in the presence of some combination of low SNRs and specific geometrical features of the map (e.g., the size of obstructions); c) in most cases, there is no need of refined maps since additional details do not improve estimation accuracy. [ABSTRACT FROM AUTHOR]

A novel ranging technique based on received signal strength (RSS) and suitable to indoor scenarios is illustrated. In the proposed technique, multiple power measurements, associated with the signals radiated by a cluster of nodes surrounding a given target, are jointly processed to improve the quality of RSS-based estimation of the distance between the target and an anchor. Specific algorithms for the generation of a cluster and for the acquisition of power measurements are described. Simulation results show that, when used in indoor positioning systems, the proposed ranging technique is substantially more accurate than noncooperative strategies. In addition, it allows to concentrate significant processing tasks in a limited number of fixed anchors, so reducing maintenance costs and making it possible to adopt cheap and simple portable wireless nodes. [ABSTRACT FROM AUTHOR]

Focuses on a study which devised soft-in soft-out algorithms for symbol detection over frequency-flat Rayleigh fading channels. Algorithm for maximum a posteriori detection over frequency-flat channels; Results; Conclusion.

Presents a study which investigated optimum one-shot detection over known and partially known doubly selective Rayleigh fading channels. Description of the communications system model; Definition of partially matched detectors for doubly selective fading channels; Numerical results and conclusions.

Presents a novel two-stage noncoherent receiver for interleaved trellis-coded CPSFK signals transmitted over time-selective channels. Information on the novel noncoherent algorithm; Estimation and tracking of the channel parameters; Simulation results and conclusions.