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This paper studies the use of amplify-and-forward (AF) relays for robust beamforming, with the aid of imperfect channel state information (CSI) at the sender. In particular, the maximization of the worst-case signal-to-noise ratio (SNR) at the destination terminal is studied under a bounded spherical region for the norm of CSI error vector. We show that under a condition on the estimated CSI quality,...
We consider an Amplify-and-Forward relay selection for OFDM networks with fairness constraints where a source node communicates with a destination node with the help of one or more relays. The system model assumes all relays participate and considers the subcarrier pairing with fairness constraints on relays. Our subcarrier allocation algorithm is presented to maximize the system capacity based on...
Cooperative diversity systems rely on using relay nodes to relay copier of transmitted information to the destination such that each copy experiences different channel fading, hence increasing the diversity of the system. In this letter, we proposed a novel distributed cooperative beamforming scheme for decode-and-forward relay networks without channel state information (CSI) feedback. We further...
As the number of users increases, the amount of required feedback Channel State Information (CSI) at the base station becomes huge and prohibits the feasibility of conventional adaptive resource allocation algorithms in fairness-aware downlink OFDMA systems. Thus, this paper presents a novel mechanism making use of multi-user diversity to greatly reduce the feedback CSI while maintaining almost the...
Power allocation with relay selection with incomplete channel state information is considered. Particularly, the utility function is based on the rate and adds the different pricing schemes to reflect the cost of each node according to the different status of each node. We decide if and which relay node to take part in cooperative communication based on the SNR of each node. Then the source and the...
This work presents a novel adaptive cooperation scheme that takes both the channel state information and residual energy information into account to prolong the network lifetime while meeting the transmission rate requirement of destination. In order to achieve this aim, we will select the relay with the best instantaneous weighted channel conditions by attributing a weight coefficient to each relay...
Communication over delay-constrained block-fading channels with discrete inputs and imperfect channel state information at the transmitter (CSIT) is studied. The CSIT mismatch is modeled as a Gaussian random variable, whose variance decays as a power of the signal-to-noise ratio (SNR). We focus on the large-SNR behavior of the outage probability when transmit power control is used. We derive the outage...
Multiuser diversity is inherent in wireless networks due to independent channel variations of different users. It requires that the transmitter has the knowledge of the channel state information (CSI) of each user in the downlink. Too much feedback will bring a heavy load to the system in some cases. This paper investigates the problem of exploiting multiuser diversity in a one source multiple destinations...
We consider a source-destination pair assisted by multiple decode-and-forward relays without channel state information at transmitter (CSIT). We investigate three schemes exploiting spatial diversity including multiple-relay cooperation (MR-Coop), conventional multiple-relay relaying (MR-Relay), and multiple-input-single-output (MISO). The total power is equally allocated to transmission partners...
This paper focuses on average bit error rate (BER) and diversity order analysis of distributed Alamouti's code in dissimilar cooperative networks with channel state information (CSI)-assisted relays. We first assume that the relays adopt the amplifying coefficient. A lower and an upper bounds of the average BER of the distributed Alamouti's code are derived. Then we show that the distributed Alamouti's...
In this paper, distributed power allocation schemes are studied for amplify-and-forward (AF) cooperative relay networks, where only partial channel state information (CSI) is available at the source and relays. Aiming at minimizing the total transmit power while providing a target outage probability, a scheme is first investigated in which the source decides transmit power and a relay-forwarding threshold,...
In this paper, we consider a cooperative system based on relay selection in a scenario where the available channel state information (CSI) is subject to delays. In order to exploit the selection diversity gains of the system while providing robustness against CSI inaccuracy, we propose a robust relay selection strategy based on a minimum mean square error (MMSE) Bayesian estimator. As shown in the...
The problem of dirty paper coding (DPC) over the (multi-antenna) fading dirty paper channel (FDPC) Y = H (X + S) + Z is considered when there is imperfect knowledge of the channel state information H at the transmitter (CSIT). The case of FDPC with positive definite (p.d.) input covariance matrix was studied by the authors in a recent paper, and here the more general case of positive semi-definite...
We consider a wireless relay network with Rayleigh fading channels, and apply distributed space-time coding (DSTC) in amplify-and-forward (AF) mode. It is assumed that the relays have statistical channel state information (CSI) of the local source-relay channels, while the destination has full instantaneous CSI of channels. It turns out that, combined with power allocation in the relays, AF DSTC results...
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