Advances in Electronics and Telecommunications

Issue no 4. ( advances_vol2_no4_dec2011.pdf )

Radio Communication Series: Recent Advances in Wireless Communication Networks

Issue editor: Alain Sibille, Davide Dardari and Hanna Bogucka
ISSN 2081-8580

This special issue collects extended versions of the selected papers from the Joint Newcom++ COST2100 Workshop 2011, 1-2 March, 2011, Paris, France, as well as papers on Radio Communications accepted from open call.

Dr Dénia Bouhired, Dr Geoff Hilton, Prof Mark Beach
Abstract:
This paper proposes a novel source detection technique and details the requirements of the measurement system and the necessary data processing. The procedure employs standard antenna pattern measurement methods to extract directional information of the surrounding propagation channel. A calculated magnitude ratio ultimately allows a three dimensional spatial map of the surrounding radiation sources and their complex field properties to be produced. The technique is then experimentally validated in terms of the spatial signature of the environment characterised, but also shown to yield correct relative field levels and phase information.
Francesco Montorsi, Fabrizio Pancaldi, Giorgio M. Vitetta
Abstract:
Propagation in non-line-of-sight (NLOS) conditions is one of the major impairments in ultrawideband (UWB) wireless localization systems based on time-of-arrival (TOA) measurements. In this paper the problem of the joint statistical characterization of the NLOS bias and of the most representative features of LOS/NLOS UWB waveforms is investigated. In addition, the performance of various maximum-likelihood (ML) estimators for joint localization and NLOS bias mitigation is assessed. Our numerical results evidence that the accuracy of all the considered estimators is appreciably influenced by the LOS/NLOS conditions of the propagation environment and that a statistical knowledge of multiple signal features can be exploited to mitigate the NLOS bias, reducing the overall localization error.
Lingfeng Liu, Raffaele D
Abstract:
On-body channels in wireless body area networks, i.e. with radio propagation occurring on the surface of human body, are typical time-varying channels due to the frequent body movements in reality. The dynamic local body scattering dominates the temporal and spatial properties of the on-body channels, which show large variance depending on the channel distribution and the patterns of body movements. In this paper, we present some major achievements on the dynamic on-body channel modeling at 2.4 GHz under the framework of the COST 2100 action. Results of two complementary measurement campaigns are presented: a canonical one based on a geometrical description of a single subject, and a scenario-based one covering different subjects. Statistical models covering the Doppler spectra and the spatial correlation of on-body channels are presented. An analytical model is also introduced offering a time-space description of the on-body channels, which is validated by the canonical measurement campaign.
Marko Höyhtyä, Sofie Pollin, and Aarne Mämmelä
Abstract:
Prediction of future idle times of different channels based on history information allows a cognitive radio (CR) to select the best channels for control and data transmission. In contrast to earlier work, the proposed method works not only with a specific type of traffic but learns and classifies the traffic type of each channel over time and can select the prediction method based on that. Different prediction rules apply to partially deterministic and stochastic ON-OFF patterns. New prediction methods for both traffic classes are developed in the paper. A CR predicts how long the channels are going to be idle. The channel with the longest predicted idle time is selected for secondary use. Simulations show that the proposed classification method works well and predictive channel selection method outperforms opportunistic random channel selection both with stochastic and deterministic ON-OFF patterns. Weibull, Pareto, and exponentially distributed traffic patterns are used in stochastic simulations to show general applicability of the proposed method. The classification-based method has even a higher gain when channels of interest include both stochastic and deterministic traffic. The collision rate with primary user over a given time interval can drop by more than 70 % compared to the predictive system operating without classification.
Mariam Kaynia, Flavio Fabbri, Geir E. Øien, and Roberto Verdone
Abstract:
We consider a bounded square-shaped ad hoc network scenario, within which packet arrivals are distributed randomly in space and time according to a 3-dimensional Poisson Point Process. Each packet is transmitted over a single hop to its destination, located a fixed distance away. Within this context, the outage probability of the ALOHA and CSMA protocols is derived, and we evaluate the impact of edge effects in space on the performance of MAC protocols. Our analytical expressions are verified with Monte Carlo simulations. The behavior of the network is evaluated as the system parameters, such as the node density, the physical size of the network, and the distance between each transmitter and its receiver, vary. Furthermore, the obtained results are compared to those of unbounded networks, showing that edge effects reduce the average outage probability across the network significantly, due to the lower level of interference suffered by boundary nodes.
Mihaly Varga; Mihai Alin Badiu; Vasile Bota
Abstract:
Cooperative hybrid ARQ (HARQ) protocols have been widely studied in the recent years and it was shown that their efficiency is higher than the one of the cooperative protocols. This paper proposes a joint design within which the HARQ protocol collaborates with the link adaptation function and the cooperative transmission scheme in order to adapt the behavior of the HARQ protocol to the QoS requirements of the supported services. As performance metrics of the HARQ protocol, we use the expected number of retransmissions and the expected spectral efficiency. The paper also studies the influence of the protocol parameters upon the performance provided.
Adrian Kliks, Paweł Sroka, Merouane Debbah
Abstract:
In this paper the application of the concept of crystallized rate regions to MIMO transmission with femtocell interference is investigated. Based on the referenced work a new game definition specifying the new cost function derived for MIMO transmission with femtocell interference is proposed. Furthermore, the idea of channel approximation for complexity reduction is described. Finally, the simulation results for different MIMO realizations are presented, which prove the correctness of application of the proposed regret-matching algorithm in the MIMO channel scenario with femtocell.
Piotr Remlein, Tansal Gucluoglu
Abstract:
This paper discusses the performance of antenna selection technique in space time turbo coded MIMO-OFDM systems. Multiple-input multiple-output (MIMO) technology can either increase the data rate through spatial multiplexing or improve the reliability through diversity. Space-time turbo codes (STTC) have been proposed to provide robust communications in wireless environment. STTC technique incorporates the methods of transmitter diversity and channel coding to provide significant reduction of error rates over the traditional communication systems. The orthogonal frequency division multiplexing (OFDM) is a modulation method designed to mitigate multipath distortion and frequency selectivity of wireless channels at high data-rate transmissions. The MIMO-OFDM technology supports the advantages of both the MIMO system and the OFDM technique. In practice, a major impediment in MIMO-OFDM technology is the cost of the hardware, because every antenna element requires a complete radio frequency (RF) chain to transmit signal over that element. In many (size and power constrained) mobile applications, it is desirable to have less RF units in multiple antenna systems which can be possible with antenna selection technique. In this paper, joint transmit and receive antenna selection for a space-time turbo coded MIMO-OFDM system is investigated. As the selection criterion, maximization of signal to noise ratio at the receiver is used for per-tone and all-tone selection methods. The simulation results show that the studied system improves performance by achieving significant diversity gains which makes it attractive for the next generation wireless standards.
Andrzej Kabat, Lida Sadeghioon,Hazar Sayed Darwish, Annie Gravey
Abstract:
In this paper we present an approach for supporting best effort traffic on an ECOFRAME ring network which has been dimensioned primarily for Guaranteed Traffic. This approach is reservation based, and is combined within the ECOFRAME MAC with the opportunistic access method used for Guaranteed traffic. The reservation method is intended to both protect the Guaranteed traffic and allocate fair shares of the excess resources to the competing Best Effort traffic flows. We analyze the performance of the proposed approach on 2 simple scenarios, i.e. a ”concentration” scenario where all stations send the same amount of traffic to a Hub on the ring, and an ”any-to-any” scenario where each station sends the same amount of traffic to each other station on the ring. The maximum amount of BE traffic that can be supported without degrading the QoS offered to Guaranteed traffic is derived using simple queueing models. The simple scenarios are then simulated, with the modified MAC, and compared to the theoretical results. The obtained simulation results show that Guaranteed traffic is very well protected, and that spare resources are indeed fairly shared. However, the reservation approach fails to meet the maximum utilization in the any-to-any scenario due to the fact that it forbids spatial reuse for BE traffic.