Introduction: Cooperative communications [1] create diversity gains for network users with a single antenna. The classical cooperative scheme consists of two orthogonal time slots (TS): a broadcasting TS for a source (S) to transmit its signal to the intended destination (D), and a relaying TS for a relay (R) to retransmit S’s signal to D. There are amplify-and-forward (AF) and decode-and-forwa...

In this paper, we investigate the performance of selecting the best protocol between amplify and forward (AF) and decode and forward (DF) in multiple relay networks with multiple interferences at relays. In the selection scheme, the best protocol between AF and DF is selected depending on the comparisons of signal-to-interference and noise ratio (SINR) for all source-relay links. All relays mea...

This paper focuses on turbo packet combining for hybrid AF/DF multi-relay systems operating over multipleinput–multiple-output (MIMO) broadband channels. We consider virtual antenna based combining strategy that has been widely studied for the point-to-point hybrid ARQ. However, the extension of this combining strategy to hybrid AF/DF cooperative communications is not straightforward. In this p...

Systematic Luby transform (SLT) codes constitute rateless codes, which are capable of adaptively adjusting their code rate depending on the channel quality without any explicit channel state information (CSI) at the transmitters. SLTs are also suitable for space time collaboration-aided relay networks. In this study, an iterative decoding-aided SLT scheme is combined with 16 quadrature amplitud...

We Consider a multihop relay network in which two terminals are communicating with each other via a number of cluster of relays. Performance of such networks depends on the routing protocols employed. In this paper, we find the expressions for the average symbol error probability (ASEP) performance of amplify-and-forward (AF) multihop transmission for the simplest routing protocol in which the ...

Reconfigurable intelligent surface (RIS) assisted air-to-ground wireless powered communication networks (WPCNs) are constructed to promote the energy efficiency of system, in which unmanned aerial vehicles (UAV) reflects towards energy-constrained hybrid access points (HAP) through RIS. Subsequently, HAP uses collected communicate with users blind areas RIS-UAV. By optimizing parameters such as...

In a wireless transmission network, relay node or intermediate nodes play a very important role. Thus, the use of relay transmission offers significant performance benefits, including being able to achieve spatial diversity through node cooperation and extending coverage without requiring large transmitter powers. In this paper, we consider a Physical-layer Network Coding (PNC) scheme for a two...

Future wireless communications technology should fulfill the demands of multimedia applications, interactive internet service, high data rates and power efficiency. However, wireless channel is affected by multipath fading that can degrade the system performance. To overcome the problem, cooperative communication has been introduced to be an efficient diversity technique to combat the multipath...

Optimization of the switching thresholds for constant-power adaptive five-mode M -ary quadrature amplitude modulation (M -QAM) transmission with an amplify-and-forward (AF) relay network is developed. The optimization criterion is the maximization of spectral efficiency subject to an average bit-error-rate (BER) constraint. This approach results in a constant-BER variable-rate M -QAM AF relay s...

In this thesis, we focus on joint relay beamforming and transceiver processing in multiuser relay network. First of all, we consider the scenario in which multiple source-todestination (S-D) pairs intend to communicate with the help of multiple distributed amplify-and-forward (AF) relays. A rank-two beamforming Alamouti scheme is proposed at the sources and relays, and we aim to minimize maxima...