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In cognitive radio networks, cooperative spectrum sensing is employed to detect the presence of primary user quickly. In this paper, we study the sensing performance of a cognitive user U1 by allowing another cognitive radio user U2 to act as its relay (cooperation). We take the average power rather than the instantaneous power as the decision statistic, so, we can use multiple signal samples in each...
In a fading environment, a secondary user may opportunistically transmit with high power when its signal received by the primary receiver is deeply faded. The spectrum access gain can be obtained when there is perfect knowledge of channel sensing at both primary and secondary receivers. In this paper, we investigate the case of imperfect knowledge of channel sensing and explore the impacts on spectrum...
A potential global performance of dynamic spectrum allocation (DSA) that exploit adaptive antenna array interference mitigation (IM) diversity at the receiver, is analyzed for interference-limited environments with high level of frequency reuse assuming Rayleigh propagation model. The system consists of base stations (BSs) that may belong to different providers, who can optimize frequency allocation...
In this paper a macrodiversity system with two microdiversity system is considered. Microdiversity system is used to reduce the effects of Rayleigh fading to the system performance and macrodiversity system is used to reduce the effects of gamma fading to the system performance. Rayleigh density function is used to describe amplitude of received signal and gamma density function is used to model the...
A new generic statistical fading model for wireless ad hoc networks is proposed. Besides small scale fading, our proposed model incorporates the variations due to geometry, i.e. the statistical distribution of transmission and reception distances. The geometry-inclusive fading model presented here can also be considered as a generalization of several prior studies. Consequently, it is valid for any...
In this paper we derive a lower bound on the bit error rate (BER) for the individual bit streams that can be mapped simultaneously in an hierarchical way onto generalized multilevel quadrature amplitude modulations (M-QAM). The expressions are valid for time-discrete multipath Rayleigh fading environments with imperfect channel estimation and can be regarded as an extension of the well-known matched...
Differential frequency hopping (DFH) is a novel technique for the frequency-hopping system in HF (high frequency) bands. The frequency transition function (FTF) and the signal detection methods are the key issues for DFH system. Product-combining receiver (PCR) and linear-combining receiver (LCR) are adopted for DFH system in the paper. The performances of DFH system with the PCR and LCR are analyzed...
We consider an amplify-and-forward (AF) cooperative-diversity system where a source node communicates with a destination node directly and indirectly (through multiple relays), in this paper, we analyze the system where N multiple relays that have the strongest signal strength at the destination are selected out of M relays and forward their received data from the source node to the destination node...
In this paper, measurements of the power delay profile and small-scale fading statistics in industrial environments have been presented. The well-known Saleh-Valenzuela model is fitted to the averaged power delay profiles, and new statistical descriptions of the model's parameters have been proposed. Small-scale amplitude fading was found to be Rayleigh distributed for all delay bins except the first...
Statistical modeling of rainfall induced temporal variations in a foliage channel at VHF frequency is performed in this paper. With the help of the Akaike weight omegaj, Weibull and Rayleigh functions are identified as the two suitable models to describe the tap amplitude variations. The Weibull function is then used as the channel model to analyze the rainfall induced temporal variations in a foliage...
In this paper, we deal with the analytical performance study of spatial multiplexing (SM) multiple-input multiple-output (MIMO) systems experiencing flat Rayleigh fading and log-normal shadowing. We address the problem of finding a tractable expression for the symbol error outage (SEO) in this environment. In order to obtain the SEO, a symbol error probability (SEP) inversion w.r.t. the signal to...
We present a novel and accurate approximation for the distribution of the sum of equally correlated Nakagami-m variates. Ascertaining on this result we study the performance of Equal Gain Combining (EGC) receivers, operating over equally correlating fading channels. Numerical results and simulations show the accuracy of the proposed approximation and the validity of the mathematical analysis.
In the current work the effects of hop-by-hop packet loss and retransmissions via ARQ protocols are investigated within a Mobile Ad-hoc NET-work (MANET). Errors occur due to outages and a success probability function is related to each link, which can be controlled by power and rate allocation. We first derive the expression for the network's capacity region. A network utility maximization problem...
Asymptotic error rate expressions are derived for multi-branch equal gain combining and selection combining operating on arbitrarily correlated Rayleigh fading channels. These closed-form solutions are used to provide rapid and accurate estimation of the error rates in large signal-to-noise ratio regions. More importantly, it is shown that the asymptotic error rates over correlated branches can be...
The bit error rate (BER) performance analysis of maximum-likelihood (ML) based decode and forward (DF) cooperative diversity systems has been a subject of considerable interest. Exact analysis of ML-DF transmission has been considered a challenging problem due to the nonlinear characteristic of the ML detector. In this paper, we provide exact expressions for the BER of ML-DF cooperative systems employing...
Given a slowly fading channel, the performance of multi-layer coding is studied for single-user scenarios. Both the source and destination are equipped with multiple antennas. The channel state information is perfectly known at the destination but not at the source. The objective is to maximize the average data rate received at the destination when the destination is able to perform successive decoding...
The use of finite state Markov chains (FSMC) for the simulation of the Rayleigh channel has been generalized in the last years. Several parameters influence the construction of the chain. The chain can be defined in terms of the complex channel response, the envelope of the received signal or the Signal to Noise Ratio. Moreover the partition method has to be selected among various options. This paper...
Recently radio frequency (RF) level antenna diversity combining has been proposed as a low cost and power efficient alternative to conventional antenna diversity combining. In RF level diversity combining the diversity weights are implemented in the hardware by making use of circuit elements such as phase shifters and variable gain amplifiers, while channel estimation is performed in the digital baseband...
Evaluation of bit error rate (BER) of a digital communication system is usually done via simulation using Monte Carlo (MC) method. For low BER, MC method requires huge sample sizes to achieve certain efficiency. To overcome this limitation, many variance reduction techniques such as importance sampling (IS) have been proposed. In this paper, we put forward a novel simulation method - Monte Carlo simulation...
In this paper we apply importance sampling (IS) for efficient performance evaluation of turbo codes over Rayleigh fading channels. Our approach is based on the most probable error path (MPEP) method which shifts the input probability density function (pdf) to the mode of the optimal biased distribution where most probable errors are located. In particular, we show how to bias the pdf of the AWGN process...
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