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Spectrum modeling represents an important tool, of the cognitive radio concept. Number of works have focused on developing accurate methods for modeling the spectrum usage in order to provide reliable and efficient assessment of the possible spectrum availabilities. This paper proposes a novel method for modeling of spectrum usage based on classification of measured quantities into multiple levels...
Energy consumption in mobile networks, e.g. 3G networks, may be a substantial part of an operator's expenses. A large part of the total energy of the network is consumed by the radio access network. Today operators are saving energy by turning off carriers or cells during periods with low traffic by manually configuring on-off periods. At the same time, operators are seeking to increase cost efficiency...
Sensing-throughput tradeoff under outage constraints has been studied before with an energy detector (ED). However, the ED does not work well in the presence of noise power uncertainty. So we study sensing-throughput tradeoff by using an autocorrelation detector (AD) for an OFDM signal. In this paper, we derive a closed form expression for the false alarm probability over both Nakagami-m and Rician...
With the increase of the number of wireless sensing or metering devices, the collection of sensing data using wireless communication becomes an important part of many applications. Cognitive radio technology can be used to facilitate the deployment of a bandwidth efficient sensor system. In this paper, we propose a data collection and dissemination framework for cognitive radio sensor systems to fully...
This paper presents a game theoretic solution for end-to-end flow allocation with joint channel and power assignment in multihop cognitive radio networks under the physical interference model. The objective is to find a distributed solution that maximizes the network utility with limited information. We consider two different criteria to define this network utility: the number of flows that can be...
We address the use of single parity check product codes (SPCPC) for erasure recovery in opportunistic spectrum access schemes, where erasures are packets lost during a collision with the primary user (PU) due to sensing impairments (non detection). Our main motivation in using SPCPC is their low decoding complexity. We derive an analytical performance bound for these product codes when the PU's activity...
Previous work on an energy detector (ED) has only analytically examined its performance over a flat-fading channel. But for the real environment, the channel should be assumed frequency-selective due to the high date rates. So in this paper we evaluate the performance of an ED over a frequency-selective fading channel. We show that the performance of the ED might improve because of the multipath environment...
We study transmission rate control and performance delay in cognitive radio (CR) links from a cross-layer perspective. We assume a hierarchical CR network where the secondary users (SU) access the spectrum band in an opportunistic and noncooperative way. The SU goal is to transmit a fixed-size file (fixed amount of data packets) during the sojourn time of the primary users (PU's) idle state. We assume...
Energy-based sensing (EBS) has been a topic of strong research in the last years due to its importance to Cognitive Radios (CRs). While EBS has been used in several works, different parameterizations have been adopted. In this work we compare different parameterization criteria to determine the decision threshold to the energy detector. We compare their performance through simulations by characterizing...
In this paper, we propose a cooperative spectrum leasing scheme for cognitive radio networks, in which both the primary user (PU) and the secondary user (SU) target to maximize their individual utility. The PU leases a portion of its spectrum to the SU to obtain revenue when its QoS is guaranteed, and the SU rents the spectrum to achieve its target data rate. This cooperative spectrum leasing problem...
In the last years, Ultra Wideband (UWB) systems have received growing interest for their low-power consumption and low-complexity implementation. Because of the ultra-short emitted waveforms nature, timing acquisition presents a most important challenge for achieving good performance. In this paper, in order to address this task and to achieve this goal, we design and test a novel timing acquisition...
We consider a Gaussian multiple-access channel (MAC) with an amplify-and-forward (AF) relay, where all nodes except the receiver have multiple antennas and the direct links between transmitters and receivers are neglected. Thus, spatial processing can be applied both at the transmitters and at the relay, which is subject to optimization for increasing the data rates. In general, this optimization...
An adaptive distributed space-time coding (DSTC) scheme and algorithms are proposed for two-hop cooperative MIMO networks. Linear minimum mean square error (MMSE) receivers and an amplify-and-forward (AF) cooperation strategy are considered. In the proposed DSTC scheme, an adjustable matrix obtained by a feedback channel is employed to transform the space-time coded matrix at the relay node. Linear...
We propose a MIMO spatial multiplexing system with distributed single-antenna relay stations which operate in the amplify-and-forward mode. A maximum likelihood detector is implemented at the receiver. We evaluate the system bit error rate (BER) performance by means of a semi-analytic bounding method which can closely bound BER at high signal to noise ratio (SNR), and hence determine diversity order...
In this paper, we consider the scenario of a cellular network where base stations aim to transmit several data packets to a set of users in the downlink, within a predefined time, at minimal energy cost. The base stations are non-cooperating and the instantaneous transmission rate depends on the instantaneous SINR at the receiver. The purpose of this article is to highlight a power-efficient transmit...
In the context of green technology, we propose in this work1 a new channel access method for wireless systems to reduce energy consumption. This method uses the concept of Cross Layer Design and cognitive radio blind sensing techniques to formulate a unified framework for congestion and fading analysis as well as Backoff exponent computation. It allows to acquire from the physical layer the information...
Accurately localizing users in indoor environments remains an important and challenging task. The article presents new results on room-level indoor localization, using cellular Received Signal Strength fingerprints collected with a standard cellular handset programmed to perform fast scans of the 900 and 1800 Megahertz GSM bands as a user explores an indoor environment at a normal walking pace. Support...
In this paper we investigate the optimal relay location in the sense of maximizing suitably defined coverage region for MIMO relay channel. We consider the general Rayleigh fading case and assume that the channel state information is only available at the receivers (CSIR), which is an important practical case in applications such as cooperative vehicular communications. In order to overcome the mathematical...
Predistortion linearizer for high nonlinear power amplifiers (PAs) is an important topic of research in wireless applications. Behavioral models based on polynomial functions are widely used for both PAs and predistorters. However, they often suffer from numerical instability problems when we include high nonlinear-order in the mathematical model. In this work, we propose a new predistorter model...
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