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A spectrum sensing technique for Cognitive Radio (CR) Networks based on the Sequential Analysis of A.Wald is applied to partially coherent channel scenarios. It is shown that using Wald's test, it is possible to reduce the number of samples required to detect the presence of the primary user by approximately a factor of 2 in comparison to the well known Neyman-Pearson test. An expression for the Wald...
Adaptive relaying schemes significantly improve the performance of relay networks by switching the forwarding technique according to the reliability of the received signal. In this paper, semi-analytical solution for the power optimization in adaptive relay network is derived. Furthermore, the accuracy of the solution is confirmed by using the polyblock algorithm, which is an optimization tool for...
The focus of this paper is on the performance of an orthogonal frequency division multiplexing (OFDM) transmission system considering the combined influence of receiver noise, Rayleigh fading and the timing error due to imperfect slot synchronization at the receiver. Performance results are presented in terms of BER, BER improvement and BER-floor in presence of inter-channel interference (ICI) and...
Next generation wireless networks are likely to include cooperative relaying in their design. The performance of certain cooperation schemes in realistic scenarios should be evaluated by system level simulations (SLS). Moreover, the link adaptation (LA) and radio resource management become more complex, since cooperation schemes involve transmissions on more than one link and joint processing at the...
Letting nodes cooperate improves the performance of wireless networks. To organize this cooperation, many cooperative transmitters employ channel knowledge that they obtain from the destination. Such Channel State Information (CSI) feedback introduces errors and overhead whose degrading effect on the overall performance has not been consistently studied so far. Capturing this degradation, we provide...
This paper investigates the impact of carrier frequency offset (CFO) on Single Carrier wireless communication systems with Frequency Domain Equalization (SC-FDE). We show that CFO in SC-FDE systems causes irrecoverable channel estimation error, which leads to inter-symbol-interference (ISI). The impact of CFO on SC-FDE and OFDM is compared in the presence of CFO and channel estimation errors. Closed...
Despite its practical performance limitations, energy detection has gained popularity during the last years as a spectrum sensing technique for dynamic spectrum access in cognitive radio networks. The main advantages of energy detection-based spectrum sensing are its simplicity, low computational and implementation costs as well as its ability to work irrespective of the actual signal to be detected...
Cooperation diversity schemes employing space-time block coding (STBC) techniques have been proposed for wireless networks to increase network capacity and coverage even when each node is equipped with a single antenna. Such schemes allow several relay stations distributed in space to assist the transmission between a given source-destination pair. A key design problem in cooperative networks is to...
In this work, we proposed a multiuser relaying strategy for a cooperative network with multiple sources sharing the radio resource provided by the cooperative relays simultaneously. Different from the existing work, the set of relays forwards signals of all source users over a common channel to enhance spectral efficiency. With full channel information available at relays, the set of sub-optimal precoders...
We study the problem of cooperative communication in the case that the assisting node (i.e. the relay) has access to correlated information about the source that needs to be reconstructed at the destination. Finding the relaying strategy that minimizes the reconstruction distortion at the destination, is one of the long standing open problems in information theory. In this paper, we propose a novel...
In this paper, we investigate the asymptotic e-outage capacity of a half-duplex large fading relay network, which consists of one source node, one destination node, and N relay nodes. The relay nodes are assumed to be randomly deployed in a given area and under fatal independent random attacks with probability p. With a total power constraint on all the nodes, we examine the e-outage rate of the amplify-and-forward...
A cooperative network can be modeled with a basic relay channel, composed by a couple of nodes - source and destination - and a third node called relay. The source broadcasts its communication to both the destination and the relay. Therefore the relay transmits the same information to the destination, which combines the two signals received from both the source and the relay. This system allows to...
In this paper, we consider an amplify-and-forward (AF) wireless relay system where multiple source nodes communicate with their corresponding destination nodes with the help of relay nodes. While each user is assisted by one relay, one relay can assist many users. Conventionally, each relay node is assumed to equally distribute the available bandwidth and power resources to all sources for which it...
Recent results establish the optimality of interference alignment to approach the Shannon capacity of interference networks at high SNR. However, the extent to which interference can be aligned over a finite number of signalling dimensions remains unknown. Another important concern for interference alignment schemes is the requirement of global channel knowledge. In this work we provide examples of...
This paper presents a cross-layer approach to jointly design adaptive modulation and coding (AMC) at the physical layer and cooperative truncated automatic repeat request (ARQ) protocol at the data link layer. We first derive an exact closed form expression for the spectral efficiency of the proposed joint AMC - cooperative ARQ scheme. Aiming at maximizing this system performance measure, we then...
In this paper, the problem of power allocation in the amplify-and-forward (AF) cooperative network is investigated based on the achievable maximum signal-to-noise ratio at the destination node. With assumptions that the source node has the perfect channel state information, optimal power allocation algorithms are developed for the relay networks under two scenarios: the full cooperative scheme with...
We consider the problem of cooperative communication for a network composed of two half-duplex parallel relays with additive white Gaussian noise. Two protocols, i.e., Simultaneous and Successive relaying, associated with two possible relay orderings are proposed. The simultaneous relaying protocol is based on dynamic decode and forward (DDF) scheme. For the successive relaying protocol, a Non-Cooperative...
In wireless cooperative networks, the asynchronism between the relays can be a source of diversity which is similar in its essence to the multipath diversity of frequency selective channels. In this context, an asynchronous two-relay two-hop cooperative wireless network using the Decode-and-Forward protocol is studied. The outage probability in the high Signal to Noise Ratio (SNR) regime is derived...
We consider a fully connected network with S full duplex source nodes, D full duplex destination nodes and R relay nodes, perfect feedback to source and relay nodes, and noisy cooperation between all source, relay and destination nodes. We show that this network has SD/S+D-1 degrees of freedom if the channel gains are time-varying/frequency selective. The implication of the result is that, the techniques...
A new method for signal-to-noise ratio (SNR) estimation is considered when multiple receiving antenna elements receive quadrature amplitude modulation (QAM) signals in complex additive white Gaussian noise (AWGN) spatially and temporally white (uncorrelated between antenna elements). In this paper, we also present the extension of other existing methods to the single input multiple output (SIMO) configuration...
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