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Cooperative communication systems employ cooperation among nodes in a wireless network to increase data throughput and robustness to signal fading. However, such advantages are only possible if there exist perfect synchronization among all nodes. Impairments like channel multipath, time varying phase noise (PHN) and carrier frequency offset (CFO) result in the loss of synchronization and diversity...
This paper is concerned with a challenging problem of channel estimation for amplify-and-forward cooperative relay based orthogonal frequency division multiplexing (OFDM) systems in the presence of sparse underwater acoustic channels and of the correlative non-Gaussian noise. We exploit the sparse structure of the channel impulse response to improve the performance of the channel estimation algorithm,...
This paper investigates the performance of a cooperative downlink (DL) multi-carrier code division multiple access (MC-CDMA) system, where each of the K user's mobile station (MS) is supported by a group of MSs acting as relays in order to achieve the relay diversity. In a cooperative DL communication, multi-user interference (MUI) at the relays precludes the achievement of the relay diversity. In...
We focus in this work on optimal maximum a posteriori (MAP) decoding for lattice-based physical-layer network coding operating in Gaussian multiple access relay channels. We consider a general lattice design that makes our results hold for any lattice coding schemes of any dimensions including the Compute-and-Forward framework. By examining the MAP decoding rule, we first derive an analytical bound...
Securing communication against non-colluding passive eavesdroppers has been extensively studied. Colluding eavesdroppers were considered for interference-limited large networks. However, collusion was not investigated for large cooperative networks. This paper closes this gap: we study the improvement the eavesdroppers achieve due to collusion in terms of the information leakage rate in a large cooperative...
We study a relay channel with confidential messages (RCC), which involves a sender, a receiver and a relay. In the RCC, a common information must be transmitted to both a receiver and a relay and also a private information to the intended receiver, while keeping the relay as ignorant of it as possible. The level of ignorance of the relay rather than the private message is measured by the equivocation...
In this paper, we study the problem of cooperative spectrum sharing among a primary user (PU) and multiple secondary users (SUs) under quality of service (QoS) constraints. The SUs network is controlled by the PU through a relay which gets a revenue for amplifying and forwarding the SUs' signals to their respective destinations. The relay charges each SU a different price depending on its received...
The goal of this paper is the analysis of cryptographic mechanisms utilised in VANET communication for Intelligent Transportation Systems with focus on security. The practical part of the contribution is dedicated to modelling of security properties of VANET networks in OPNET Modeler modelling tool extended by the implementation of the OpenSSL library. The designed models simulate a transmission of...
This paper considers network-layer cooperation in cognitive radio networks whereby secondary users can relay primary user's packets, in return for a more favorable spectrum access rules. Under this cooperative scheme, the paper investigates whether, and under what conditions, the primary and secondary networks can be stabilized without explicit knowledge of the packet arrival-rates. We consider a...
The multiple-input multiple-output relay broadcast channel with one source, one relay, and two destinations is studied. It is assumed that the source and the relay cooperatively serve one of two destinations, which may have a weaker channel from the source (due to, for example, being located far from the source), while the source alone serves the other destination that has a stronger channel. Given...
In this paper, a novel scheme called blind interference neutralization is provided in the 3- cell interference channel with a shared instantaneous relay. The shared relay not only receives signals from sources, but also sends signals to destinations with a processing matrix. With the proposed scheme, each destination is able to pick up its own desired signal without encountering inter-user interference...
In this paper, the linear minimum mean square error beamformers are designed for relay-assisted cloud radio access network (C-RAN). In C-RAN, the remote radio units are separated from the baseband units to save energy cost. To further enhance network coverage, it is a good choice to duly arrange relay nodes. Regrading the per-antenna power constraints at both the relay nodes and the remote radio heads...
This paper investigates linear precoding designs for a cooperative amplify-and-forward (AF) network with a multi-antenna relay having complete channel state information (CSI). The focus is on both orthogonal AF (OAF) and non-orthogonal AF (NAF) protocols. The precoders at the relay are derived based on the maximum ratio combining (MRC) scheme, followed by an optimal power amplification factor to maximize...
In this paper, a novel remapping design for multiway relay system with multi-user (MU) is presented. Every user exchanges information with its partners via the relay. The two communication terminals have different modulation schemes according to their individual channel quality.We term this system an adaptive modulation asymmetric multi-way relaying networks, in which signal space alignment for network...
In a cooperative cognitive radio (CR) network when a group of CR users acts as relays for a given user, a cooperative beamforming among these relays can be used to improve the quality of communications. However, this cooperative beamforming can introduce asynchronous interference at the primary receivers due to different propagation delays between different CR relays and the primary receivers. We...
In this paper, we study beamforming techniques for secrecy with worst case signal-to-interference-plus-noise ratio (SINR) guarantees in cooperative communications with imperfect channel state information (CSI). The worst case SINRs are the minimum SINR at the intended destination and the maximum SINR at the eavesdroppers. We consider a norm bounded CSI error model. With the available imperfect channel...
We develop an analytical framework for the end-to-end (e2e) asymptotic performance of pilot-symbol assisted Mary phase-shift keying (M-PSK) dual-hop relaying communication networks. The relays use the selective-decode-and-forward protocol and are equipped with multiple receive antennas. Channel estimation per antenna branch is done based on the least-squares estimation technique by means of pilot...
In this letter, a robust distributed amplify and forward (AF) relay beamforming problem is solved, using the stochastic approach with imperfect channel state information (CSI) at the relay nodes and destination terminals. Specifically, we model the channel estimation error as a Gaussian random vector with known statistical distribution. Our objective is to minimize the total relays transmit power...
We present a novel low-complexity technique that obtains the Physical-Layer Network Coding (PNC) equation coefficient vectors for the two-way relay channel when Compute-and-Forward is employed. The proposed method is based on pre-computed look-up tables that are used for all channel realizations. It is shown that the size of the look-up tables can be made small by taking into account the statistics...
In this paper, the issue of energy-aware competitive resource allocation in an amplify-and-forward (AF) relay-assisted multiple-antenna interference network is considered. A non-cooperative game-theoretic approach is taken and the EE of each communication link is defined as the ratio of the achievable rate over the consumed power. The proposed resource allocation algorithm jointly allocates the relay...
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