Energy-efficient Cooperative Transmission Research Articles

Censoring-Based Relay Transmission for Achieving Energy Efficiency in Cognitive Radio Networks

Energy efficiency (EE) is critical to achieve cooperative sensing and transmission in relay-assisted cognitive radio networks (CRNs) with limited battery capacity. This paper proposes an energy-efficient cooperative transmission strategy with combined censoring report and spatial diversity in cooperative process, namely, censoring-based relay transmission (CRT). Specifically, secondary relays (SRs) take part in cooperative sensing with differential censoring to reduce energy consumption, and the best SR assists secondary transmission to enhance communication quality in transmission stage and thus to improve secondary transmission EE. First, we derived generalized-form expressions for detection probability, reporting probability, sensing energy, and expected throughput for CRT. Second, we investigate a mean EE-oriented maximization nonconvex problem by joint optimizing sensing duration and power allocation for secondary users under secondary outage probability and sensing performance constraints. With the aid of Jensen’s inequality, an efficient cross-iteration algorithm with low complexity is proposed to obtain the suboptimal solutions, which is developed by golden segmentation search method. Finally, extensive simulations are conducted to evaluate the performance of CRT. The results show significant improvements of SUs’ EE compared with traditional noncooperation single cognitive transmission schemes, which demonstrate the benefits of our proposed cooperative strategy in conserving energy for secondary transmission.

Energy-efficient cooperative transmission for intelligent transportation systems

Recent advances in cooperative multiple-input-multiple-output (CMIMO) techniques have encouraged interest in the development of intelligent transportation systems (ITS). They have the potential for use in the infrastructure to vehicle (I2V) and infrastructure to infrastructure (I2I) communications in ITS networks where the energy consumption of wireless sensor nodes embedded on the road infrastructure is constraint. Therefore, how to reduce the energy consumption becomes a hot research topic. In this paper, applications of cooperative communications in ITS networks are proposed for reducing the total energy consumption. At first, the ITS model is established based on the cooperative multiple-input-multiple-output spatial modulation (CMIMO-SM). A detailed energy consumption analysis of the proposed scheme compared with the traditional single-input-single-output (SISO) based scheme is then presented. The comparison conducted between these communication schemes helps us select the optimal one for energy reduction in energy constrained ITS networks. Additionally, under the guidance of the proposed scheme we consider the multi-hop transmission scenario where the energy efficiency improvement is achieved by finding the optimal hop number with the equal hop-length scheme. As a result, we analyze the energy consumption in different situations, and discuss the requirements on the hop-length and hop number in ITS networks. It shows that the optimal results are dependent on the ITS scenarios and choosing the appropriate transmission scheme will provide a good energy consumption performance in ITS.

Energy efficiency maximisation in wireless powered networks with cooperative non‐orthogonal multiple access

In the 5G wireless networks, non-orthogonal multiple access (NOMA) is a promising paradigm to improve its high spectrum efficiency. This study considers applying simultaneous wireless information and power transfer (SWIPT) technique to cooperative NOMA wireless networks, where energy-constrained relay nodes harvest the ambient radio-frequency signal and use the harvested energy to forward the packets from sources to destinations. To this end, the authors first formulate the energy-efficient cooperative transmission problem for SWIPT in NOMA with imperfect channel state information. Then, by exploiting alternative optimisation and dual decomposition, they design an iterative algorithm for power allocation and power splitting (PS) to solve the non-convex optimisation problem. The authors' simulation results reveal that the proposed algorithm can converge within a few iterations and yield optimal system energy efficiency.

Energy-Efficient Cooperative Tfor Simultaneous Wireless Information and Power Transfer in Clustered Wireless Sensor Networks

This paper considers applying simultaneous wireless information and power transfer (SWIPT) technique to cooperative clustered wireless sensor networks, where energy-constrained relay nodes harvest the ambient radio-frequency (RF) signal and use the harvested energy to forward the packets from sources to destinations. To this end, we first formulate the energy-efficient cooperative transmission (eCotrans) problem for SWIPT in clustered wireless sensor networks as a non-convex constrained optimization problem. Then, by exploiting fractional programming and dual decomposition, we develop a distributed iteration algorithm for power allocation, power splitting and relay selection to solve the non-convex optimization problem. We find that power splitting ratio plays an imperative role in relay selection. Our simulation results illustrate that the proposed algorithm can converge within a few iterations and the numerical analysis provides practical insights into the effect of various system parameters, such as the number of relay nodes, the inter-cluster distance and the maximum transmission power allowance, on energy efficiency and average harvested power.

A Novel Energy-efficient Cooperative Transmission Scheme Based on V-BLAST Processing and ICA clustering for WSNs Lifetime Maximization

In wireless sensor network, one of the main objectives is how to improve its lifetime because the sensor nodes are generally energy-limited. Thus, providing ways to optimize energy Consumption, which ultimately increases the network lifetime, is of great importance. In this paper, we propose and evaluate an energy-efficient cooperative MIMO transmission scheme based on V-BLAST technique. In proposed scheme the clustering is done based on Imperialist Competitive Algorithm (ICA) then V-BLAST technique based virtual MIMO transmission are used. This proposed protocol performance is analytically and experimentally is compared with previous presented works. From the analysis and the simulation results, it is seen that the proposed method can reduce the energy consumption of the network and prolong the sensor networks lifetime compared with existing techniques.

Energy-Efficient Cooperative Transmission in Heterogeneous Wireless Networks with QoS Constraint

Heterogeneous wireless network is an effective scheme to improve both the spectrum efficiency and energy efficiency of cellular system. However, interference limits the performance of such heterogeneous wireless network seriously. Hence cooperative decision making, i.e., cooperative transmission is necessary. In this paper, we develop an energy-efficient scheme for cooperative transmission in heterogeneous wireless networks with QoS constraint. Since too much signaling is needed for absolutely centralized cooperation, which is infeasible in practical system, partly cooperation is considered in this paper. We first formulate the problem as a two-stage Stackelberg game. In the first stage, an energy-efficient transmission scheme for macrocell users (MUE) is proposed based on the interference state of the MUEs. In the second stage, after obtaining the SINR and target SINR of the MUEs, the femtocell base stations update their beamformers and optimize the transmission power individually through a non-cooperative game, the existence and uniqueness of the Nash equilibrium is proved. Then an iterative algorithm is proposed to obtain the Stackelberg equilibrium. Simulation results show the performance gain of the proposed scheme.

Performance Analysis and Optimization for Energy-Efficient Cooperative Transmission in Random Wireless Sensor Network

This paper considers random wireless sensor networks where nodes are distributed randomly and form clusters to transmit the packets to relay clusters using cooperative multi-input-multi-output (CMIMO) technique. First, we study CMIMO energy consumption and divide it into intra-cluster energy consumption and inter-cluster energy consumption. Then we focus on analyzing the system performance in terms of overall packet error rate (PER) and energy consumption. Based on system performance metrics, we propose a new node sleep strategy, where overall energy consumption is minimized by coordinating inter-cluster transmitting energy consumption and the number of sensor nodes in activation. Compared to existing works, our contributions are (1) we consider random distribution of nodes and get a closed-form expression of overall PER that simplifies the energy minimization problem; (2) we analyze the tradeoff between overall energy consumption and nodes active rate. In simulation, we investigate the relationships among nodes active rate, inter-cluster transmitting energy consumption and the overall energy consumption. Furthermore, we discuss how these parameters are affected by the nodes density, the inter-cluster transmitting distance, the cluster radius and the intra-cluster energy consumption. Finally, we validate that the proposed nodes sleep strategy has significant energy savings compared with non-sleep cooperative transmission and direct transmission.

Energy-efficient hybrid opportunistic cooperative protocol for single-carrier frequency division multiple access-based networks

In this study, a new energy-efficient hybrid opportunistic cooperative (HOC) transmission protocol is proposed for single-carrier frequency division multiple access (SC-FDMA)-based cooperative networks. The author considers a single source–destination pair and multiple relays network. The proposed protocol improves the energy efficiency of SC-FDMA-based networks by selecting the most energy-efficient cooperative transmission protocol from a set of available protocols according to the current channel state information. The protocols considered in the development of the HOC protocol are amplify-and-forward, decode-and-forward, compress-and-forward and estimate-and-forward. Computer simulation is done over four different scenarios of channel conditions. The obtained results show that the proposed HOC protocol significantly improves the delay-limited capacity and minimises the outage probability of SC-FDMA-based cooperative networks. The results also show that the minimum required average total power in the proposed HOC protocol is less than that of opportunistic decode-and-forward by 0.55 dB.

A New Cooperative Transmission Metric in Wireless Sensor Networks to Minimize Energy Consumption per Unit Transmit Distance

In this letter, we propose a new metric for energy-efficient cooperative transmission in wireless sensor networks (WSN) where the circuit energy consumption is taken into consideration. Under the guide of the new metric, we optimize the energy consumption per unit transmit distance by selecting the appropriate number of cooperative nodes and the transmit energy consumption. In this way, we provide a new point of view to achieve the energy-efficient cooperative transmission, and the proposed metric can be applied in clustered multi-hop sensor networks to transmit data to an appropriate next relay cluster far away from the former cluster.

Throughput per Pass for Data Aggregation from a Wireless Sensor Network via a UAV

Data retrieval from a sensor field by means of unmanned aerial vehicle (UAV) has increasing interests for both commercial, military, and homeland security applications. In these situations, the design of energy-efficient communication links between sensor field and UAV is crucial, owing to battery powered sensor nodes. We propose an energy-efficient cooperative transmission scheme for wireless sensor networks (WSNs) where data gathered by sensor nodes need to be collected into a far receiver. In particular, we consider a network composed of sensor nodes that share a common message that has to be transmitted asynchronously toward a fusion center onboard a UAV. We consider that the communication channels between the nodes and the fusion center are subject to fading and noise. Due to the far communication distance and energy constraint at each node, the fusion center must be able to reliably receive the weak and noisy signals. In our approach the fusion center consists of a Rake receiver capable of collecting multiple replicas of the same information from the nodes in the WSN. The performance of the proposed cooperative diversity scheme is then studied in terms of throughput, bit error probability, and energy efficiency. The results obtained show that, as the number of nodes increases, the proposed approach increases network lifetime, communication reliability, and throughput.

Distributed Space-Time Continuous Phase Modulation Code Design

In this paper, distributed space-time (ST) codes for continuous-phase modulation (CPM) are introduced. The distributed ST codes are designed to operate in wireless networks containing a large set of nodes N, of which only a small a priori unknown subset S sub N will be active at any time. Under the proposed scheme, a relay node transmits a signal which is the product of a diagonal block-based ST code (optimized specifically for ST-CPM transmission) and a signature vector of length N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> uniquely assigned to each node in the network. An efficient method is presented for the design and optimization of appropriate signature vector sets, assuming a quasi-static, frequency nonselective fading channel model. If a properly designed signature vector set is employed it is shown that a diversity order of d = min{N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ,N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> } can be achieved, where N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> is the number of active relay nodes. The decoding complexity of the proposed scheme is shown to be independent of the number of active relay nodes, and non-coherent receiver implementations, which do not require channel estimation, are applicable. Compared to distributed ST transmission with linear modulation, distributed ST-CPM can considerably reduce the energy consumption at the transmitter due to the constant envelope of the transmit signal. At the same time, the additional energy consumption due to more complex receiver processing can be kept low. Therefore, the proposed distributed ST-CPM scheme is particularly apt for energy-efficient cooperative transmission in wireless networks.