High Power Efficiency Transmission Based on Game Theory for AF Cooperative Communication

A low complexity algorithm is proposed for joint allocation of power profiles at the source and relay nodes and subcarrier assignment for single user amplify and forward (AF) cooperative communication using orthogonal frequency division multiplexing (OFDM) system. The relay uses AF cooperative relaying to transmit messages on a set of available subcarriers with diversity. The remaining subcarriers are used for direct transmission without diversity. The objective is to allocate the resources to maximize the sum rate subject to individual power constraint on each node. We formulate such a problem as subcarrier based resource allocation that seeks joint optimization of subcarrier assignment and power profiles at the source and relay nodes. The algorithm is based on an ordering of the channel gain's ratio and splitting them into two partitions, then searching for the partition that maximizes the sum rate. Simulation results demonstrate the merit of the proposed algorithm.

We consider an amplify-and-forward (AF) cooperative diversity system where a source communicates with a destination with the help of multiple relay nodes. The conventional system assumes all relay nodes participate, with the available channel and power resources equally distributed over all nodes. This approach being clearly sub-optimal, we first present an optimal power allocation scheme to minimize the outage probability for an AF system. Next, we propose a new selection scheme where only one, the "best" relay node is chosen to participate in the transmission. We show that at reasonable power levels the selection AF scheme maintains full diversity order, and has significantly better outage behavior and average throughput than the conventional scheme or that with optimal power allocation

Due to the great potential in extending propagation distance and enhancing the link reliability, amplify and forward (AF) cooperative communications have attracted much attention recently. However, the existing studies mainly focus on the energy consumption analysis and optimization, and also the channels used in communications are based on Rayleigh/Rician fading model, and/or it was usually supposed that the channel state information (CSI) is known or can be acquired by a training sequence. In this paper, blind signal detection for AF cooperative communication systems based on time division multiple access (TDMA) is studied, in which the channels are modeled as frequency selective fading and the CSI are unknown. A blind signal detection algorithm of partial amplify and forward (PAF) cooperative communication is proposed based on semidefinite relaxation (SDR). This method can recover the data without the training sequence and need not to implement blind equalization for the unknown channels. With the correlation between data of different links, the proposed method can obtain the optimal solution efficiently and achieve better performance of signal detection than the traditional algorithm. By simulations, the energy consumption efficiency as well as the overall system performance of the proposed strategy are verified.

In this paper, we consider cooperative beamforming in an amplify-and-forward (AF) cooperative network with multiple relay nodes. Specially, only "appropriate" relay nodes are selected to perform cooperative beamforming. Source node can determine the relay nodes with just mean channel gain, which will reduce the complexity of obtaining instantaneous channel state information (CSI). This scheme guarantees that the energy is allocated to those "appropriate" relay nodes, and accordingly improves the energy efficiency. Therefore, it is able to provide superior diversity over the conventional cooperative beamforming. We also prove that power allocation (PA) between source and selected relay nodes is a convex problem, which can be resolved with lower computational complexity. Simulation results demonstrate that our scheme achieves an essential improvement in terms of outage performance, as well as high energy-efficiency for energy-constrained networks.

Cooperative communication (CC) has been proposed to increase the wireless channel capacity and reliability by employing multiple single-antenna nodes to form a virtual antenna array. Many efforts focus on exploiting the benefits of CC among multiple source-destination pairs with an unrealistic assumption that each of them communicates over a dedicated channel without interference. In this paper, we investigate the transmission scheduling problem for multiple source-destination pairs under the assistance of a set of dedicated relay nodes on a single channel. By applying the protocol interference model, we propose a concept of cooperative link to characterize the interference regions of CC. Due to the NP-completeness of optimal scheduling, LP (linear programming) based heuristic algorithms are proposed to maximize the minimum transmission rate under a given relay assignment. Then, without specifying a relay node for each source-destination pair, we study the max-min rate problem by jointly considering transmission scheduling and relay assignment. Heuristic algorithms are proposed to solve this more challenging problem. Finally, extensive simulations are conducted to show that the proposed algorithm outperforms direct transmission substantially.

In this paper, the problem of precoder design and node power allocation in a three node cooperative multiple-input multiple-output (MIMO) relay system is discussed. All the nodes are assumed to be equipped with multiple antennas and the source and the relay nodes are subject to a total transmit power constraint. We first introduce an upper bound on the received mean square error (MSE), then we suggest suboptimal structures to the source and the relay precoders to minimize this bound. Unlike the previous works in this area, the proposed precoders are easy to calculate and does not involve in computationally costly iterative methods. Next, based on the precoder structures, it is shown that proper transmit power assignment to the source and relay nodes can further improve the system performance and the optimal power allocation for the special case of single symbol transmission is derived. Simulation results show significant improvement in the received mean square error (MSE) by applying the proposed precoding and node power allocation schemes. The node power allocation scheme is also shown to be most effective when the relay and destination nodes have different noise levels.

Power Line Carrier (PLC) and micropower wireless are two mainstream local communication technologies for low-voltage electricity information acquisition system, the cooperation- and complementarity between which-represent the future development trend. Aiming at the high outage probability deficiency- of traditional PLC and micropower wireless cooperative communications and the insufficient utilization of channel diversity gains, an Adaptive Relay Selection (ARS) based PLC and wireless multi-channel cooperative communication method is proposed. When the quality of the PLC link between the source node and the destination node is poor, the data of the source node is first sent to the potential relay node through the micropower wireless channel. Then, based on the channel quality of the PLC link between the relay node and the destination node, as well as the channel capacity between the source node and the relay node, the relay node and relay mode can be confirmed. Thus, a virtual Multi-Input Multi-Output (MIMO) PLC array can be constructed between the relay node and the destination node, and the system reliability can be improved by using distributed space-timecoding scheme. Simulation results show that, compared with traditional methods, ARS can significantly reduce the outage probability of the relay system, and reduce the transmission error rate via transmission diversity gains of multiple relay nodes.

In this paper, we investigate cooperative OFDM communications using amplify-and-forward (AF) protocol at the relays, in the presence of imperfect timing synchronization. In most studies on cooperative communications, perfect time synchronization among cooperating nodes is assumed. In practice, however, due to imperfect time synchronization, orthogonality among the subcarriers of the different nodes' signals at the destination receiver can be lost, causing inter-symbol interference (ISI). In this paper, we derive analytical expressions for the average SINR at the DFT output at the destination as a function of timing offset in cooperative OFDM with AF protocol, and illustrate the SINR degradation as a function of the timing offset. We also present an interference canceling (IC) receiver to mitigate the effects of ISI when there is timing offset. We show that the proposed IC receiver achieves improved BER performance even when timing offsets are large.

Power optimization for maximum channel capacity in MIMO relay system

In a wireless communication system, a cooperative communication technique is a communication method for improving performance. In the conventional scheme, when a destination user is located in the cell boundary, one base station communicates with a destination user. At a same time, a destination user communicates with other base stations which cooperate with base station. If a distance between a base station and a destination user is far, the quality of communication is degraded by the effect of channel attenuation. Therefore, this paper proposes an enhanced cooperative transmission scheme using the orthogonal frequency multiplexing in the wireless communication system. The proposed scheme uses extra relays between a base station and a destination user. When the channel state of a destination user is bad, other base stations are used. In order to obtain better performance than the conventional scheme, the cooperative decode and forward (DF), and space time cyclic delay diversity (STCDD) and cyclic delay diversity (CDD) are applied in the extra relays. In simulation results, the proposed scheme has higher error and throughput performances than the conventional scheme for obtaining diversity gain when the used modulation scheme is increased. Also, the proposed scheme which uses cooperative DF has slightly better error and throughput performances than the proposed scheme which uses cooperative STCDD and CDD due to less error propagations and resultant higher diversity gain.

Multiple-input multiple-output (MIMO) and cooperative communications have been attracted great attention for the improvements of communication capacity, power consumption, and transmission coverage. The conventional fixed relaying protocols, amplify-and-forward (AF) and decode-and-forward (DF), have their own advantages and disadvantages, i.e. AF performs better than DF for low signal-to-noise ratio (SNR) region, while the reverse is true for high SNR region. Therefore, this paper proposes an SNR-adaptive forward (SAF) relaying scheme obtaining the advantages of both AF and DF. Furthermore, the proposed SAF does not need to switch between AF and DF when SNR changes. The main idea is to adaptively derive the soft information at the cooperative relay nodes based on the information of the received signal and the SNR. Besides, based on the theoretical analysis and the simulation results, it is affirmed that the proposed SAF achieves superior performance than both AF and DF for all SNRs. Moreover, the performance gain would be improved with the increasing number of parallel cooperative relay nodes.

On one hand, cooperative communication has been gaining more and more popularity since it has great potential to increase the capacity of wireless networks. On the other hand, the applications of cooperative communication technology are rarely seen in reality, even in some scenarios where the demands for bandwidth-hungry applications have pushed the system designers to develop innovative network solutions. A main obstacle lying between the potential capability of channel capacity improvement and the wide adoption of cooperative communication is the lack of incentives for the participating wireless nodes to serve as relay nodes. Hence, in this paper, we design TASC, an auction scheme for the cooperative communications, where wireless node can trade relay services. TASC makes an important contribution of maintaining truthfulness while fulfilling other design objectives. We show analytically that TASC is truthful and has polynomial time complexity. Extensive experiments show that TASC can achieve multiple economic properties without significant performance degradation compared with pure relay assignment algorithms.

ABSTRACTBy combining Spatial modulation (SM) with cooperative communication, the diversity gain brought by cooperative relaying and high rate of SM can be obtained. In this paper, considering amplify-and-forward (AF) protocol, the performance of cooperative SM system with imperfect channel state information (CSI) over Rayleigh channel is analyzed. According to the performance analysis, the moment generating functions (MGFs) of effective signal-to-noise ratios (SNRs) are derived. With the MGFs, closed-form expressions of the error probability of antenna index detection and the error probability of symbol detection for imperfect CSI are achieved. Thereby, the approximate overall average bit error ratio (BER) is obtained, and these theoretical expressions include those under perfect CSI as special cases. Besides, the asymptotically approximate BER for large SNR is also derived. Based on this, a suboptimal power allocation (PA) scheme is developed, and the corresponding PA coefficients are attained by minimizing the asymptotical BER. As a result, closed-form PA can be attained for the system with multiple receive antennas. Computer simulations show that the theoretical BERs are close to the corresponding simulated results, which illustrates the effectiveness of the derived theoretical expressions. Compared with the conventional equal PA scheme, the proposed PA scheme enhances the BER performance efficiently.

Cooperative communication has great potential to improve the wireless channel capacity by exploiting the antennas on wireless devices for spatial diversity. The performance in cooperative communication depends on careful resource allocation such as relay selection and power control. In this paper, the network is expanded and more than one source is used. What is proposed is a distributed buyer/seller game theoretic framework over multiuser cooperative communication networks in order to stimulate cooperation and improve the system performance. A two-level Stackelberg game is employed to jointly consider the benefits of the source node and the relay nodes in which the source node is modeled as a buyer and the relay nodes are modeled as sellers, respectively. In this work we proposed coded method in which relays amplify and code Source data and send it to destination at the same time and then signal detection occur in destination, but in the codeless network relays send source data separately to destination. So, here coded and codeless networks are compared and contrasted. The stimulation results revealed that the proposed coded method performed better than the codeless ones; furthermore, the research shows that relays near the sources can play a significant role in increasing source node's utility, so every source would like to buy more power from these preferred relays. Also, the proposed algorithm enforces truthful power demands.

In this study, we propose a cooperative transmission framework based on Adaptive Modulation and Coding (AMC) cooperative food communication system in Multiple-Input Multiple-Output (MIMO) fading channels. We consider the scenario that consists of one source node, one relay node and one destination node, they all equipped with multiple antennas and employed the adaptive modulation and coding schemes. The relay node follows the decode-and-forward strategy, forwarding the information received from the source to the destination in case of correct decoding. Through computer simulation, we got the effective capacity of the adaptive cooperative transmission cooperative food communication system according to different Qos requirement.