Adaptive prediction and cancellation digitization method for wideband multistandard software radio base-station receivers

In this study, a new method for digitizing a combination of different analog signals occupying significantly different bandwidths and having a very high dynamic range is proposed and analyzed. Since it is based upon signal-prediction/cancellation principles, it is referred to as adaptive prediction and cancellation digitization (APCD) method and is applied to various families of signals simultaneously received by a multistandard software radio (SWR) base-station receiver. It is shown theoretically and by means of computer simulations that the APCD method can effectively reduce the high dynamic range of the signals before digitization takes place. Hence, the stringent analog-to-digital-converter (ADC) resolution requirements imposed by the operation of such SWR base-station receivers can be significant relaxed. The signal dynamic-range reduction is achieved by applying appropriate signal processing techniques, e.g., autoregressive (AR) and periodic autoregressive (PAR) prediction. Such techniques allow accurate prediction and subsequent cancellation of high-power narrowband signals present among the composite received analog signal. As these signals usually have cyclostationary statistical characteristics, analysis and performance evaluation of AR and PAR predictors, when used to predict cyclostationary signals, were presented. A new adaptive algorithm for implementing the PAR predictor is also proposed, and its validity is justified by theoretical analysis as well as by various performance evaluation results obtained by means of computer simulations.     

Comment on “Maximum likelihood decoding of uncoded and codedPSK signal sequences transmitted over Rayleigh flat-fadingchannels”

This comment points out some papers published before the paper of Vitetta and Taylor (see ibid., vol.43, no.11, p.2750-58, 1995). These early papers have dealt with the general problem of maximum-likelihood sequence estimation of coded/uncoded phase-shift keying (PSK) and quadrature amplitude modulation (QAM) signals in correlated Rician and Rayleigh-fading channels. These publications did not assume use of interleaving or use of optimal codes, designed for interleaved systems. The statistical properties of the multiplicative fading process have been included in the design of the receivers which were proposed, analyzed, and evaluated. The research contributions documented in these papers have also shown for the first time in the open literature the link between conventional detection techniques and the maximum-likelihood detection of signals in this type of fading channels     

Editorial

Mobile Networks and Applications -     

Distribution of genetic diversity in relation to chromosomal inversions in the malaria mosquito Anopheles gambiae

The epidemiology of malaria in Africa is complicated by the fact that its principal vector, the mosquito Anopheles gambiae, constitutes a complex of six sibling species. Each species is characterized by a unique array of paracentric inversions, as deduced by karyotypic analysis. In addition, most of the species carry a number of polymorphic inversions. In order to develop an understanding of the evolutionary histories of different parts of the genome, we compared the genetic variation of areas inside and outside inversions in two distinct inversion karyotypes of A. gambiae. Thirty-five cDNA clones were mapped on the five arms of the A. gambiae chromosomes with divisional probes. Sixteen of these clones, localized both inside and outside inversions of chromosome 2, were used as probes in order to determine the nucleotide diversity of different parts of the genome in the two inversion karyotypes. We observed that the sequence diversity inside the inversion is more than three-fold lower than in areas outside the inversion and that the degree of divergence increases gradually at loci at increasing distance from the inversion. To interpret the data we present a selectionist and a stochastic model, both of which point to a relatively recent origin of the studied inversion and may suggest differences between the evolutionary history of inversions in Anopheles and Drosophila species.     

Differential detection of turbo codes for Rayleigh fast-fadingchannels

The performance of turbo codes using differentially detected quadrature phase-shift keying (QPSK) signals transmitted over Rayleigh fast-fading channels is investigated. So far in the open technical literature dealing with turbo codes only slow fading has been considered. Our research has shown that the use of a simple differential detector in conjunction with turbo codes can generally outperform convolutional codes in terms of the bit-and block-error rates for fading rates with a BT product up to 0.1. However, to achieve significant performance improvements, large block sizes must be employed, particularly at slower fading rates     

Analysis of Maximum Traffic Intensity and Optimal Channel Reservation Under QoS Constraints in LEO-MSS

A novel analytical approach is developed for determining the maximum traffic intensity for Low Earth Orbit Mobile Satellite Systems (LEO-MSS) under preset Quality of Service (QoS) constraints such as call blocking and dropping probabilities. The proposed methodology also enables the optimization of channel reservation for handovers so that the traffic intensity supported by LEO-MSS is maximized.     

DVB-S2 LDPC Decoding Using Robust Check Node Update Approximations

Broadband satellite services to fixed terminals are currently offered in the forward link by the 2nd generation (2G) digital video broadcasting satellite (DVB-S2) standard. For this standard the use of powerful low-density parity-check (LDPC) error correcting codes has been adopted performing within approximately 1 dB from the Shannon capacity limit. This paper studies and compares for the first time in a systematic manner different approximation methods used in check node update computation of DVB-S2 LDPC decoding with the aim of reducing computational complexity. Various performance evaluation results are presented for a wide range of DVB-S2 parameters, such as LDPC codeword size, coding rate, modulation format and including several decoding algorithms. It is shown that the proposed check node update approximations have a robust behavior, i.e. the resulting performance is quite independent of the DVB-S2 modulation and coding parameters. It is further shown that these approximations perform very close to the optimal sum-product algorithm (SPA) in degradation, which is less than 0.2 dB. Despite this small degradation, the reduction in computational complexity compared to the optimal SPA is significant and can be as high as 40% in computational time savings.     

Cost Optimization of Partial Computation Offloading and Pricing in Vehicular Networks

Journal of Signal Processing Systems - For vehicles with limited computation resources offloading their computational tasks to a mobile edge computing (MEC) server has been studied in the past as...