Trust Degree-Based MISO Cooperative Communications with Two Relay Nodes

Considering the problems of network lifetime and energy replenishment in wireless sensor network (WSN), a Power Beacon (PB) assisted energy harvesting Simultaneous wireless information and power transfer (SWIPT) multi-relay system model is proposed. Under the condition that the relay node has the characteristics of capturing the energy of the source node and PB signal, the system throughput of the target node using the maximum ratio combining technology is derived. Then, the problem model is established under multiple constraints to ensure the communication quality of service, and a relay selection strategy based on the adaptive chaotic particle swarm optimization (ACPSO) algorithm is proposed to optimize the system throughput. Simulation and numerical results show that PB transmission power, time switching (TS) factor, power splitting (PS) factor, and other parameters have a significant impact on throughput performance. Compared with the random relay selection (RS) strategy, the proposed strategy can achieve greater throughput gain, and it is proved that the ACPSO algorithm can quickly and effectively optimize network throughput.

In this study, the authors analyse the outage performance of multirelay decode‐and‐forward cooperative networks subject to two joint practical issues of wireless communications, namely, energy constraints and transceiver hardware impairment (HI). To deal with energy constraints at relay nodes, radio‐frequency (RF) energy harvesting (EH) technique is adopted. Considering the joint impacts of RF EH technique and HI, two relay selection schemes, namely, harvested energy‐based relay selection (HEbS) scheme and channel quality‐base relay selection (CQbS) scheme are proposed. Tight closed‐form approximate expressions for the outage probability of each scheme are derived and corroborated through Monte Carlo simulations. Some representative performance comparisons are carried out and show that the diversity order achieved by the HEbS scheme is 1 and is independent of the number of relays, K , whereas that achieved by the CQbS scheme is K , which is full diversity.

This paper investigates the impact of relay selection (RS) on the performance of cooperative non-orthogonal multiple access (NOMA), where relays are capable of working in either full-duplex (FD) or half-duplex (HD) mode. A number of relays (i.e., K relays) are uniformly distributed within the disc. A pair of RS schemes are considered insightfully: 1) single-stage RS (SRS) scheme; and 2) two-stage RS (TRS) scheme. In order to characterize the performance of these two RS schemes, new closed-form expressions for both exact and asymptotic outage probabilities are derived. Based on analytical results, the diversity orders achieved by the pair of RS schemes for FD/HD cooperative NOMA are obtained. Our analytical results reveal that: 1) the FD-based RS schemes obtain a zero diversity order, which is due to the influence of loop interference at the relay; and 2) the HD-based RS schemes are capable of achieving a diversity order of K , which is equal to the number of relays. Finally, simulation results demonstrate that: 1) the FD-based RS schemes have better outage performance than HD-based RS schemes in the low signal-to-noise ratio (SNR) region; 2) as the number of relays increases, the pair of RS schemes considered are capable of achieving the lower outage probability; and 3) the outage behaviors of FD/HD-based NOMA SRS/TRS schemes are superior to that of random RS and orthogonal multiple access based RS schemes.

In this paper, a decode-and-forward cooperative interference-limited multiple relay network is considered. An efficient relay selection strategy and its performance analysis are proposed, where only the relay nodes are affected by multiple interferences. In the proposed relay selection scheme, the selected relay is not always used, depending on the power of interferences and the channel state information of all links, while the direct path between source and destination is always used. For analytical tractability the distribution of interference-limited channel is approximated as an exponential distribution with high accuracy. Analysis of cooperative networks with interference-limited relays can be performed using the approximate exponential distribution by the same methods which have been used without interferences. We derive the bit error probability and outage probability of the proposed opportunistic max-min relay selection (OMRS) scheme in independent non-identically distributed Rayleigh fading channels. Numerical results present the superiority of OMRS over the conventional relay selection scheme which always uses the selected relay path. The exactness of the approximate analysis for interference-limited relays is also shown in numerical results.

Since the existing full-rate cooperative transmission schemes have a serious defect in low Bit Error Rate (BER) performance while the existing high-rate cooperative transmission schemes have a serious defect in low spectral efficiency, a distributed high-rate cooperative relay transmission scheme based on full-rate cooperative communication model is proposed in this paper, in which Cyclic Delay Diversity (CDD) technology and Linear Constellation Precoding (LCP) technology are employed. Moreover, the proposed scheme addresses the issue of obtaining maximum spatial and multipath diversity with low decoding complexity and high transmission reliability. The BER performance of the proposed scheme is contrasted to that of the full-rate transmission scheme where better performance is achieved, and is improved when the number of the multipath or the relay nodes increases.

Cooperative communication in wireless sensor network has emerged a solution of energy limitation of sensor nodes. Relay selection in cooperative communication plays an important role to improve the performance of energy constrained networks. In such networks, to make balance between network lifetime (NL) and Bit Error Rate (BER) is the difficult task for the researchers. Although, the minimization of BER can be achieved by choosing best possible relay to destination link which has lowest path loss, but this solution cannot gives guarantee to enhance the NL because some nodes are frequently selected for retransmission of the information. On the other hand, increase the NL is possible by efficiently distribution of energy consumption among all the available relay nodes. In this paper, we propose an Adaptive Neuro Fuzzy Inference System based Relay Selection (ANFISRS) scheme where residual energy of the relay node and path loss of the channel are considered as an input parameters for the relay selection. ANFISRS makes balance between these two parameters for improving network lifetime and BER. Furthermore, the proposed method is compared with three existing strategies: Random Relay Selection, Maximum Residual energy based Relay Selection, and Minimum Energy Consumption based relay selection. The proposed scheme considerably reduces the BER while enhance the network lifetime over the existing strategies.

In order to improve the delay quality-of-service aware throughput performance of the optical wireless communications, a joint power allocation and relay selection scheme is proposed for a relay assisted multichannel coherent optical wireless communication system. The proposed joint power allocation and relay selection scheme provides the delay aware quality-of-service guarantee by maximizing the end-to-end effective capacity under the average transmit power constraints at both source as well as relay nodes. The joint power allocation and relay selection problem is formulated as a non-convex and combinatorial optimization problem, and the solution of this optimization problem is obtained using a time-sharing relaxation technique. Subsequently, a fast convergent algorithm is proposed for the joint power allocation and relay selection by considering the delay aware quality-of-service requirements of the services transmitted over the optical wireless communication channels. Numerical results demonstrate that the proposed joint power allocation and relay selection scheme provides the strict statistical delay aware quality-of-service with an improved throughput without increasing the transmit power requirements.

In recent years, there has been an upsurge of interest in relay-based wireless networks in both industry and academia. With the introduction of relay node, which can forward packet for some other nodes which require relaying assistance, the network performance can be dramatically improved: the coverage of an infrastructure network is extended; spatial diversity is exploited and system capacity is increased; meanwhile, the transmission reliability is enhanced. In relay wireless networks, in order to fully exploit the benefit of relay transmissions, MAC and network layer schemes need to be redesigned. In this thesis, we will focus on the study of relay selection problem in MAC layer and optimal routing decision problem in network layer. Several relay and routing selection schemes are proposed for different wireless applications when concept of relaying is applied. In relay selection part, a cooperative MAC protocol is designed to dynamically select relay nodes according to real-time channel condition and contention relationship for broadcast traffics in vehicular networks; in respect to the cognitive radio networks, a relay-based cognitive radio architecture is proposed to balance the spectrum availability and traffic demand for secondary users, an experimental testbed is constructed to verify its effectiveness; we also propose an incentive relay set selection scheme to motivate secondary users to act as cooperative relays to forward packets for primary users. In routing selection part, a cooperative routing scheme which considers contention relationship among links is proposed in multi-source multi-destination multi-hop wireless networks; a cooperative network coding-aware routing scheme is given to enable relaying to further enhance the benefit of network coding in wireless networks. Finally, a software-defined radio-based cooperative communication testbed is built to evaluate the performance of various cooperative transmission schemes. The above studies demonstrate that with appropriate relay and routing schemes, relaying benefit and cooperative diversity is fully exploited and network performance is remarkably enhanced in relay-based wireless networks.

In cooperative relay networks with multiple users and multiple potential relays, which relay nodes are selected has great impact on the system performance. It is an optimization problem for selecting suitable relay nodes. The exhaustive search can solve this problem but the complexity will increase factorially with the network size, i.e., the number of users and the number of relays in the network. In this paper, we formulate both single-objective and multi-objective relay selection problems. For single-objective relay selection problem, only system throughput or fairness is considered. A novel quantum particle swarm optimization (QPSO) based relay selection scheme is proposed. For multi-objective relay selection problem, two contradictive objectives, i.e., system throughput and fairness are considered simultaneously. A novel non-dominated sorting quantum particle swarm optimization (NSQPSO) based relay selection scheme is proposed. Simulation results show that the proposed relay selection schemes have the ability to search global optimal solution but have less computational complexity compared with exhaustive search.

SummaryIn energy‐constrained military wireless sensor networks, minimizing the bit error rate (BER) with little compromise on network lifetime is one of the most challenging issues. This paper presents a new relay selection based on fuzzy logic (RSFL) scheme which provides balance between these parameters. The proposed scheme considers node's residual energy and path loss of the relay‐destination link as the input parameters for the selection of the relay node. The relay node selection by fuzzy logic is based on prioritizing higher residual energy and minimum path loss. To evaluate the performance on wireless sensor network, we compare the proposed scheme with the three existing relay selection strategies, ie, random, maximum residual energy based relay selection (MaxRes), and minimum energy consumption based relay selection (MinEnCon). The simulation results of the proposed scheme in terms of network lifetime, BER, Network Survivability Index (NSI), and average energy of network nodes have been presented and compared with different relay selection schemes. The simulation results show that the proposed RSFL scheme has the lowest BER, moderate network lifetime, average energy, and NSI.

In this study, the performance of wirelessly powered relay‐aided non‐orthogonal multiple access networks is investigated in terms of outage probability. Specifically, two relay selection strategies, i.e. two‐stage relay selection (TRS) and maximum energy harvesting relay selection (MEHS), and two energy harvesting scenarios, i.e. time switching (TS) and power splitting (PS) are considered. In each setup, outage probabilities' analytical expressions and their asymptotics are derived. Monte‐Carlo simulations are also carried out to verify the correctness of the analysis. The results show that regardless of relay selection and energy harvesting strategies, increasing transmit power can improve the proposed system performance. However, TRS can achieve a full diversity order, while MEHS has a unit diversity order. Besides, the results recommend parameter selections of PS and TS coefficients for optimal performance in term of outage probability.

In this paper, optimal power allocation and relay selection strategies in energy harvesting cooperative wireless networks are studied. In particular, signal‐to‐noise ratio (SNR)‐maximizing based power allocation and relay selection without and with energy cooperation—via wireless energy transfer—are considered. Moreover, total relay power minimization subject to target end‐to‐end SNR is investigated. The different optimal strategies are formulated as optimization problems, which are non‐convex. Thus, intelligent transformations are applied to transform non‐convex problems into convex ones, and polynomial‐time solution procedures are proposed. Simulation results illustrate that power allocation strategies achieve higher end‐to‐end SNR than relay selection ones. Finally, energy cooperation is shown to be effective in improving end‐to‐end SNR, while total relay power minimization balances end‐to‐end SNR, transmit power consumption, and harvested energy. Copyright © 2016 John Wiley & Sons, Ltd.

Deploying decode-and-forward relay nodes is a promising solution for LTE-advanced networks in order to meet the growing data rate demand and the challenging requirements for coverage extension. However, relay selection scheme plays a crucial role in enhancing the benefit of this technology. In this paper, we have proposed a new relay selection scheme which achieves a more balanced load in the network, respects the user's quality of service requirements, but more importantly, avoids recurrent handovers and reduces the transmission delay. Simulation results proved a significant enhancement of the system performance in terms of outage probability, total system throughput and delay as compared to common relay selection strategies.

In the complex and dynamically varying underwater acoustic (UWA) channel, cooperative communication can improve throughput for UWA sensor networks. In this paper, we design a reasonable relay selection strategy for efficient cooperation with reinforcement learning (RL), considering the characteristics of UWA channel variation and long transmission delay. The proposed scheme establishes effective state and reward expression to better reveal the relationship between RL and UWA environment. Meanwhile, simulated annealing (SA) algorithm is integrated with RL to improve the performance of relay selection, where exploration rate of RL is dynamically adapted by SA optimization through the temperature decline rate. Furthermore, the fast reinforcement learning (FRL) strategy with pre-training process is proposed for practical UWA network implementation. The whole proposed SA-FRL scheme has been evaluated by both simulation and experimental data. The simulation and experimental results show that the proposed relay selection scheme can converge more quickly than classical RL and random selection with the increase of the number of iterations. The reward, access delay and data rate of SA-FRL can converge at the highest value and are close to the ideal optimum value. All in all, the proposed SA-FRL relay selection scheme can improve the communication efficiency through the selection of the relay nodes with high link quality and low access delay.

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.