In this paper, we investigate the outage performance of cognitive wireless relay networks where source nodes communicate to their destinations via multiple hops facilitated by intermediate cognitive nodes able to acquire spectrum holes. Specifically, we consider a model that consists of a source node, a destination node, and a group of network clusters each consisting of a number of cognitive (...

Single-relay selection techniques based on the max-min criterion can achieve highest bit error rate (BER) performance with full diversity gain as compared to state-of-the-art single-relay techniques. Therefore, in this work, we propose a modified by considering differences among close value channels of all relays while selecting best relay node. The proposed not only enjoys but also offers sign...

In this paper, we investigate the antenna and node selection issues for amplify-and-forward (AF) and decode-and-forward (DF) multi-antenna relay networks in correlated channels. Based on the channel statistics, optimal selection criteria for antenna and relay node are derived jointly, aiming to maximize the ergodic capacity. Instantaneous channel knowledge-based selection schemes, motivated by ...

In this paper, we analyze the effect of resource allocation in two-relay networks with mixed relaying protocol. We assume that two relay nodes exist between the source node and destination node, and one relay node adopts decode-and-forward (DF) relaying protocol and the other one uses amplify-andforward (AF) relaying protocol. Differential modulation scheme is applied for all cases to bypass ch...

Consider an unstable linear time invariant system in which the sensor transmits information to a controller across an additive white Gaussian noise channel. The designer can optionally utilize a relay node to assist the controller; however the total transmission power consumed by the sensor and the relay node is constant. We consider two topologies: (i) a Gaussian relay channel, and (ii) a casc...

Relay networks have recently attracted extensive attention due to its potential to increase coverage area and channel capacity. In a relay network, a source node communicates with a destination node with the help of the relay node. The performances of improving the channel capacity and coverage area have been explored and evaluated in the literature (Sendonaris et al., 2003)-(Laneman et al., 20...

The performance of a cooperative diversity with selection combining is analyzed in Rayleigh fading channels. The effect of limited power at the relay node is also presented. Our results show that when the average signal-to-noise ratio (SNR) of each branch is identical, the single relay cooperative diversity with selection combining provides 13.5 dB power gain over the non-cooperative system at ...

An amplify-and-forward (AF) wireless relay network consisting of a one-source-one-destination node pair and cooperative multiple N relay nodes is proposed in three adverse wireless communication environments, i.e., jamming, node geometry, and channel uncertainty. Based on the minimum mean square error (MMSE) criterion, the optimal amplifying relay matrix in three adverse wireless environments w...

IEEE 802.11a/b/g standards support multiple data rates. Although the use of multiple data rates increases the capacity of wireless networks, it can lead to a performance anomaly problem. Cooperative communication for wireless networks has attracted considerable interest owing to its ability to mitigate this performance anomaly problem. In cooperative communication, a number of relay nodes suppo...

Relay networks and cooperative transmission have spurred considerable interest in recent years, promising performance improvements in, e.g., system capacity, robustness and transmission rate. In this thesis, the focus is on the so-called half-duplex relay channels, where in the system, a source node wants to transmit a message to a destination node and a relay node can potentially assist this t...