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This paper deals with the problem of estimating the average signal-to-noise ratio (SNR) for a communication system employing non-coherent binary frequency shift keying (NCBFSK) over fading channels with white Gaussian noise (AWGN). The maximum likelihood (ML) estimator and one using data statistics have been derived and simulated for various scenarios including data-aided (DA), non-data aided (NDA)...
The IMP distortion occurring with the amplification of OFDM signals through a nonlinear RF power amplifier (PA) is analysed with a view to establishing internal relations and impairment significance of different types and combinations - composition categories- of IMPS. Through this, a novel estimation method was deduced to calculate power spectral densities (PSD) of nonlinear distortion. This method...
Uncertain capacity in newly emerged Cognitive Radio Networks(CRN) renders specific performance analysis for the secondary users (SUs), particularly in the aspects of Quality-of-Service (QoS). The effective bandwidth concept is employed to analyze the SUs' performance. Considering the time-varying arrival and service process, we analytically obtain the QoS metrics, such as the approximated delay-violation...
The problem of resource allocation (RA) in a downlink OFDMA system with minimum user rate requests is examined under the realistic scenario of partial (imperfect) channel state information (CSI) at the base station. The challenge in this setting is the non-zero probability of outage events which may lead to significant performance degradation if algorithms assuming perfect CSI are utilized. In this...
The mean squared error (MSE) is commonly used to measure and compare the performance of various phase estimation techniques in communications and signal processing systems. When the received signal contains recursive nuisance parameters, the MSE is extremely difficult to obtain and even the conventional modified Cramer-Rao bound (MCRB) can not be readily applied. In this paper, a recursive MSE bound...
With the introduction of a dither sequence and scaling factors, dithered Tomlinson-Harashima precoding (THP) has shown to outperform conventional spatial THP in multi-user MIMO systems. Through a careful analysis of dithered THP, this paper exhibits that it is not only possible, but also beneficial, to eliminate the dither sequence and develop efficient scale-only THP, and the key is to resolve the...
Clustering has been used as a fundamental tool to improve scalability in large wireless ad hoc networks. Techniques based on clustering, such as routing, self-organization, context management, service discovery, etc., ensure QoS in wireless ad hoc networks when the number of devices increases. The crucial issue of clustering is the overhead generated during the cluster formation and maintenance phases...
Composite fading takes place in several communication channels due to the random variations of the local average power of the received multipath-faded signal. The generalized-K (gamma-gamma) probability density function (PDF) has been proposed recently to model composite fading in wireless channels. However, further derivations using the generalized-K PDF have shown to be quite involved due to the...
A detailed characterization of interference power statistics in CDMA systems is of considerable practical and theoretical interest. Such a characterization for uplink inter-cell interference has been difficult because of transmit power control, randomness in the number of interfering mobile stations, and randomness in their locations. We develop a new method to model the uplink inter-cell interference...
Fingerprinting localization techniques provide reliable location estimates and enable the development of location aware applications especially for indoor environments, where satellite based positioning is infeasible. In our approach we utilize received signal strength (RSS) fingerprints collected in known locations and employ a radial basis function (RBF) neural network to approximate the function...
When transmitting at a fixed-rate to a wireless mobile terminal with strict latency requirements channel inversion is often used but at the cost of a significant loss in efficiency. Further, many such systems utilize limited packet buffering at the mobile terminal. In this paper we propose a method to recapture the lost spectral efficiency by exploiting the local buffer. Specifically, in severe channel...
The applicability of the gap approximation is investigated in the context of Gaussian multi-user channels where suboptimal transmission schemes are employed. In this case, the assumption of all users being subject to Gaussian interference may not always hold. Considering the two-user Multiple Access Channel as an example, and assuming uncoded Pulse Amplitude Modulation (PAM), it is shown that the...
As a fundamental problem of wireless sensor networks, the minimal exposure path problem corresponding to the sensor network's worst-case coverage plays an important role in the applications for detecting intrusions. However, most existing works about minimal exposure path are based on omnidirectional sensors. In contrast, this paper studies the minimal exposure path problem for directional sensor...
In this paper, a new architecture to compute 1-D Discrete Wavelet Transform (DWT) based on Folding Number System (FNS) is introduced. Numbers for FNS are extracted directly from analog input without any forward converter like in the Residue Number System (RNS) based DWT. The large Dynamic Range makes the FNS DWT more efficient than those implemented using RNS systems. The proposed 1D DWT architecture...
In this paper, we study the anonymous cardinality estimation problem in radio frequency identification (RFID) systems. To preserve privacy and anonymity, each tag only transmits a portion of its ID to the reader when it is being queried. To achieve complete system coverage and increase the accuracy of measurement, multiple readers with overlapping interrogation zones are deployed. The cardinality...
Wired and wireless data networks have witnessed an explosive growth of inelastic traffics such as real-time or media streaming applications. Recently, applications relying on layered encoding schemes appeared in the context of live-streaming and video and audio delivery applications. This paper addresses the Network Utility Maximization (NUM) for scalable multimedia transmission which is relying on...
We consider the sleep mode algorithm of IEEE 802.16e mobile networks where a mobile station may switch off the transceiver and go into sleep mode in order to save power. Depending on the underlying application, different algorithms are defined in the standard. In practice, a hybrid combination of the sleep mode algorithms will be used in a mobile. In this paper, we build a novel performance model...
We propose a new limited feedback scheme for the downlink of multiuser MIMO OFDM systems based on fixed linear beamforming, i.e. the linear beamforming vectors are chosen from a fixed transmit codebook. The proposed feedback method allows the base station to uniformly approximate all multiuser rates for any selection of users and any combination of beamforming vectors defined by the transmit codebook;...
This paper presents a VLSI implementation of a high-throughput and area-efficient MIMO detector. We propose a modified Dijkstra's algorithm and a pre-calculation technique to improve the throughput by allowing overlapped processing. In addition, we propose a simple approximation of L2-norm to reduce the computational complexity without degrading the error performance noticeably. A MIMO detector based...
When a link or node failure occurs in a network, flows are detoured and therefore the hop counts of the flows increase. This increase could drastically deteriorate the quality of a network. The flow hop length stability as well as network connectivity is important for network reliability. We investigate a network design method that improves stability and connectivity of a network during a failure...
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