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A cooperative beamforming and power control scheme for amplify-and-forward wireless relay networks with single-antenna nodes is developed. Assuming perfect channel state information (CSI) and the existence of the direct link between the source and destination nodes, we design the optimal beamforming and power control weights that maximize the mutual information. In contrast to previous approaches...
This paper proposes a cooperative jamming strategy for two-hop relay networks where the eavesdropper can wiretap the relay channels in both hops. The problems of jamming beamformer design and power allocation are investigated jointly for two scenarios where the eavesdropper has either a single or multiple antennas, with the assumption that the global channel state information (CSI) is available. Under...
This paper considers a cooperative network in which binary frequency-shift-keying (BFSK) modulation is employed to facilitate noncoherent communications between a source and a destination with the help of K relays. Proposed is an adaptive cooperative scheme that employs two thresholds as follows. One threshold is used to select retransmitting relays: a relay retransmits to the destination if its decision...
We present the optimal relay-subset selection and transmission-time for a decode-and-forward, half-duplex cooperative network of arbitrary size. The resource allocation is obtained by maximizing over the rates obtained for each possible subset of active relays, and the unique time allocation for each set can be obtained by solving a linear system of equations. We also give a recursive algorithm which...
This paper considers the maximization of the sum capacity of a multiuser cooperative wireless network through the joint optimization of power allocation among source nodes and distributed beamforming weights across the relay nodes. The distributed beamforming techniques offer the capability of enhancing the sum network capacity by achieving spatial multiplexing to support concurrent communications...
In this paper, we study the joint power allocation and relay selection problem for multi-user amplify-and-forward (AF) cooperative networks. To increase the system's spectral efficiency under the orthogonal transmission assumption, each source-destination pair is constrained to be assisted by a small subset of a set of available relays. The aim of this work is to establish a framework that determines...
This paper derives an optimal power allocation (PA) to maximize the effective average signal-to-noise ratio (SNR) of distributed space-time coding (DSTC) in wireless relay networks, where the locations of the relays can be anywhere between the source and destination. It is first shown that in maximizing the average SNR, not all the relays might be active, and hence the code performance might be compromised...
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...
Rate allocation is a fundamental problem in the operation of a wireless network because of the necessity to schedule the operation of mutually interfering links between the nodes. Among the many reasons behind the importance of efficiently determining the membership of an arbitrary rate vector in the feasibility region, is its high relevance in optimal cross layer design. A key feature in a wireless...
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