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A noise robust scheme for voice activity detection (VAD) that employs a combination of both intra- and inter-frame acoustic features is presented in this paper. As intra-frame features full-band energy and mel-frequency cepstrum coefficient (MFCC) are calculated whereas integrated bispectrum is estimated as inter-frame features. The parameters combined by intra- and inter-frame features are sorted...
This paper treats the digital design of a probabilistic energy equalizer for impulse radio (IR) UWB receiver in high data rate (100 Mbps). The aim of this study is to bypass certain complex mathematical function as a chi-squared distribution and reduce the computational complexity of the equalizer for a low cost hardware implementation. As in Sub-MAP algorithm, the max* operation is investigated for...
Recently, mutli-channel aggregation has been considered, e.q. in IEEE 802.20 (MBTDD 625 k-MC mode), to achieve higher throughput on legacy wireless systems. To realize such a system, a multi-channel digital down converter (DDC) is needed for the receiver. In a conventional scheme, parallel DDCs are used to implement the mutli-channel DDC. However, such architecture results in a high computational...
Adaptive modulation schemes have been proposed to optimize Shannon's channel capacity in recent orthogonal frequency division multiplexing (OFDM) based broadband wireless standard proposals. By adapting the modulation type (effectively changing the number of bits per symbol) at the transmitter end one can improve the bit error rate (BER) during transmission at designated SNR. Blind detection of the...
Traditional polarization diversity systems have relied on the distribution of obstacles within the mobile medium to achieve signal decorrelation and power coupling between orthogonal polarizations. If the channel does not facilitate adequate power coupling, signal diversity is suboptimal because signal contribution from the polarization with lesser power is limited. Further, due to the presence of...
Artificial neural networks (ANN) techniques have become very common as equalization solutions in several types of communication channels. These neural networks are presented in many topologies. The suitable choice of a topology for equalization purpose depends on different criteria such as: convergence rate, bit error rate (BER), computational complexity, among many others. In this paper, it is investigated...
This paper describes a way to modify the K-Best Sphere Detector, using the knowledge that the real and the imaginary part of complex number are always orthogonal. To ensure that this property is used, a modification to the Real Value Decomposition is proposed that will ensure that the orthogonality is seen also after the decomposition. The proposed method allows for equally efficient implementations...
Promising results obtained for a simplified 1-optimum local search multiuser detection (1-opt s-LS-MUD), are extended in this paper to a new scenario, considering quadrature phase shift keying (QPSK) modulation and single/multiple-input multiple-output (S/MIMO) in a multi-carrier code division multiple access (MC-CDMA) system. Furthermore, so as to avoid the complex-valued computation in QPSK formats,...
In this paper, we evaluate the performance of a suboptimum maximum-likelihood receiver for FFH/BFSK systems with a worst case multi-tone jamming and additive white Gaussian noise over frequency selective Rician fading channel. As we know the computation of nonlinear modified Bessel function is required to implement the optimum ML receiver. According to this fact, one of the existent approximations...
This paper presents a localization algorithm to detect lung sounds using a circular array of microphones. We use the natural basis functions of propagation waves in height invariant wavefields to form a spatial minimum variance (MV) problem in eigen space. We also derive a Nyquist criteria for localizing sources within a circular region. This Nyquist criteria shows that the radius of the region where...
Channel estimation and training sequence design for spatially correlated fading in multiple input multiple output with orthogonal frequency division multiplexing (MIMO-OFDM) systems are still open research topics of great interest. In this paper, we investigate the linear minimum mean square error (LMMSE) channel estimation for MIMO-OFDM systems in spatially correlated fading channels. We find the...
The classical problem of extrapolation of a bandlimited signal from limited time domain data is revisited for signals defined on the sphere. That is, given limited or incomplete measurements of a low pass signal on the unit sphere, find the unique extrapolation to the complete unit sphere. Signals defined on the unit sphere arise in a number of applications, such as beam-patterns in azimuth and elevation...
In this paper we investigate multipath propagation during rain for broadband fixed wireless access (BFWA) employed in dense urban areas. The geometrical based single bounce elliptical (GBSBE) channel model was used to estimate channel parameters such as power, delay, angle of departure (AOD) and angle of arrival (AOA) of each multipath component. Depending on the spatial variability of rain, the channel...
The paper introduces a feature extraction technique for face recognition called the phase-based Gabor Fisher classifier (PBGFC). The PBGFC method constructs an augmented feature vector which encompasses Gabor-phase information derived from a novel representation of face images - the oriented Gabor phase congruency image (OGPCI) - and then applies linear discriminant analysis to the augmented feature...
It is well known that the maximum-likelihood (ML) detection for multiple-input-multiple-output (MIMO) systems requires high computational complexity. As a result, many suboptimal algorithms, achieving a tradeoff between computational complexity and performance, have been proposed. Among these algorithms, the sphere decoding (SD) detector is considered as a very efficient solution. However, the throughput...
The paper presents some most important design issues of antennas with modelled monopulse radiation pattern in both azimuth and elevation, especially of dielectric substrate microstripe antenna structures. An approach to optimisation of the antenna patterns is discussed and an example of circular antenna array solution is presented. The issue of feeding such antenna arrays is discussed. The solution...
Intermittent periodic transmit (IPT forwarding) is known as a packet forwarding scheme that achieves highly efficient packet relays in wireless multihop networks. In the method, a source node sends source packets intermittently and periodically with some transmit period, by which co-transmission space of forwarding packets, that is defined as space between multihop nodes in packet transmission, can...
A robust image transmission scheme deploying distributed-Alamouti space-time code (STC) over wireless relay networks is proposed. Specifically, we propose a cross-layer design combining application, networking, and physical layer to enhance the quality of multimedia data over error-prone wireless channels. At the application layer, a coded image sequence based on the wavelet transform is divided into...
Network coding has recently attracted a lot of interest from the research community, mainly due to its simplicity of application and the large number of applications it can be suited for. Research in network coding started on wired networks, but the researchers soon came to realize that the inherent properties of the wireless medium render it a fertile ground for the application of network coding,...
In this paper, we present a new analysis of the optimal throughput of a single user for transporting MPEG-4 video over universal mobile telecommunication system (UMTS) network. A wireless channel considers that bit errors associated with link-layer packets are due to the time-varying features of a wideband code-division-multiple access (WCDMA) channel. By this network, the perceived video quality...
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