Efisiensi Energi Sistem Komunikasi Kooperatif Multi-relay Quantize and Forward Berdasarkan Pemilihan Relay

Recently, the cooperative wireless communication system is attracting attention as 4G and beyond 4G techniques. Transmit rate and diversity are generally enhanced in MIMO systems, however, mobile devices are limited by size or hardware complexity to set many multi-antennas. The cooperative communication system has been proposed that enables mobiles to share their antennas as relays and obtain a virtual multiple-antenna transmitter. In this paper, we consider a cooperative system with AF (Amplify-and-Forward) protocol having K relays and transmitting signal individually and simultaneously. The relationships between the channel capacity and the number of selected relays will be investigated and the simulation results show that the relation between both is quasi-linear.

The performance of multiple-input multiple-output systems using spatial multiplexing can be degraded when the spatial information channels are correlated. This work proposes a solution to this problem, which is based on a cooperative wireless communication system. Within the cooperative system, the relay is selected either randomly or using the smart selection scheme, a simple and distributed approach proposed herein. These relay selection schemes are evaluated for several situations within a small cell environment, using a simulator that generates frequency-selective channel realizations. The simulation results show that the smart selection scheme yields high capacity gains close to the theoretical maximum gain.

In this paper the performance evaluation of a decode-and-forward (DAF) cooperative communication system based on combined best relay selection and adaptive modulation (AM) is investigated. These investigations are focused on evaluating the performance of the proposed system over independent non-identical Rayleigh fading channels in terms of bit-error rate (BER) and comparing the system performance with direct transmission and fixed-DAF cooperative with single relay. The simulations results using MATLAB <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> show that the cooperative scheme achieves desired bit-error rate (BER) with lower signal-to-noise ratio (SNR) values and higher spectral efficiency as compared to AM direct transmission and AM fixed-DAF cooperative with single relay.

An Hybrid Heuristic optimal relay selection strategy for energy efficient multi hop cooperative cellular communication

Power allocation is a major issue in a cooperative wireless communication system, for improving performance of the system. In this paper, we consider a cooperative wireless communication system with amplify-and-forward (AF) relaying scheme. Considering the perfect channel state information (CSI), we allocate power of source and relay using particle swarm optimization (PSO) with minimizing symbol error rate (SER) as a constraint. The PSO algorithm maintains a swarm of particles, where each particle represents a possible solution. Hence the implemented scheme for power allocation in cooperative relaying enhances the system performance.

Relay selection in cooperative communication systems over continuous time-varying fading channel

In this paper the performance of a cooperative wireless communication system based on combined best relay selection (BRS) and adaptive LDPC coded modulation (ACM) scheme is investigated. These investigations are focused on evaluating the performance of the proposed cooperative wireless communication system over independent non-identical Rayleigh fading channels in terms of bit-error rate (BER) using MATLAB® computer simulations and comparing the system performance with ACM direct transmission and ACM cooperative with single relay. The simulations results show that the proposed cooperative scheme achieves lower signal-to-noise ratio (SNR) values for desired bit-error rate (BER) and high spectral efficiency as compared to ACM direct transmission and ACM cooperative with single relay.

This paper focuses on a combining relay selection with energy harvesting (EH), known as joint relay selection with EH (JRSEH), to improve performance in wireless cooperative communication systems. Previous research was examined performance improvement with relay selection (RS) techniques without combined with EH (RS non-EH). This study aims to improve the performance by applying EH and the RS in the cooperative communication system. In the system, a source selects the best relay from several relays that produce the highest SNR value at the destination. The selected best relay performs EH based on time switching. Then, the best relay with EH obtains the power to forward information to the destination using the Amplify and Forward (AF) relay scheme. The channel from source to relay is Rician fading, and from the relay to a destination is Rayleigh fading. The research method used is system modeling and analysis of computer simulations. The system performance is calculated based on the bit error rate (BER) and the throughput in a multi-relay cooperative system with EH and RS. The results show that the performance of the proposed JRSEH higher than that of RS non-EH, multi-relay EH, and multi-relay non-EH.

As an important part of resource allocation, power allocation affects the performance of wireless cooperative system to a great extent. However, the existing cooperative communication power allocation scheme using only a single index to optimize the performance of the system makes the optimization effect unideal, put forward a cooperative communication power allocation scheme comprehensively consider of the capacity and error probability as objective function. In this paper, the capacity and error probability of the cooperative communication technology are analyzed and the corresponding theoretical formulas are derived, then prove the nonlinear relationship between the two. On this basis, make the maximizing the capacity and minimizing error probability as objective function, present the power allocation scheme based on particle swarm optimization. The simulation results show that the proposed scheme has better effect on cooperative communication system, and is more suitable for the future development of cooperative communication technology.

In this paper, we consider a generalized non-regenerative (amplify and forward) cooperative wireless communication system with L relay nodes. The Rayleigh fading channel is assumed in both broadcasting and relaying stages and maximal ratio combining (MRC) scheme is assumed to be implemented at the receiver side. We evaluate the bit error rate (BER) performance of L-relay nodes cooperative network under the influence of Rayleigh fading channel. The direct channel link between the source and the destination is assumed to have bad channel conditions, and hence, is neglected in the performance evaluation. The Prony approximation for the Gaussian Q-function is used to approximate the BER of coherent modulation techniques in the additive white Gaussian noise (AWGN) channel. Unlike existing expressions in the literature, the BER expression derived in this paper does not include integral-form terms. Numerical results are presented for the closed-form result, which show a great matching with the exact ones calculated using numerical integrals.

One of effective diversity techniques to combat fading on wireless channel is a cooperative communication system in which a source sends information through several relays and then forward it to a destination. A cooperative communication system has shown increased the system performance and reduced the energy consumption. However, it depends on the used relay mechanism that is relay protocols such as quantize and forward (QF) and amplify and forward (AF). In the previous research, energy efficiency of AF relay has investigated for a single-relay cooperative system, but multi-relay is more practical. Therefore, this research focuses on power efficiency in multi-relay cooperative communication system using QF protocol. The research method used is mathematical analysis and computer simulation for outage probability and power efficiency in the multi-relay QF. Simulation result found that multi-relay QF system could provide a high power efficiency, but the efficiency is reduced when the distance ratio increases. Power efficiency can be increased by adding the number of relays in the system. A comparison of power efficiency for QF and AF protocols has simulated, in which power efficiency of multi-relay QF is higher than that of multi-relay AF at distance ratio and power transmit. Thus, multi-relay QF system can provide high performance and power efficiency in the cooperative communication system.

The wireless communication networks are subjected to multi access interference and multipath fading. To minimize the interference cancellation in CDMA networks, multiple user detection schemes and cooperative communication networks are used. consider the uplink of a cooperative CDMA network, where users cooperate by relaying each other’s messages to the base station. When spreading waveforms are not orthogonal, multiple access interference (MAI) exists at the relays and the destination, causing cooperative diversity gains to diminish. To overcome this problem, we integrate various multiuser detection (MUD) schemes to mitigate MAI in achieving the full advantages of cooperation. Specifically, the relay-assisted decorrelating multiuser detector (RADMUD) is proposed to separate interfering signals at the destination with the help of precoding at the relays along with pre-whitening at the destination. In this paper we examined the BER performance of various MUD schemes are analyzed and compared with cooperative system. The advantages of RAD-MUD with co-operative communication shows better BER performance compared with non co-operative wireless communication system and other existing cooperative MUD schemes are also shown through MATLAB Simulations.

In order to overcome fading in wireless channels and increase the performance of wireless systems, cooperation is needed between the source node and relay node. In a cooperative wireless communication system, PA (Power Allocation) and RS (Relay Selection) are important issues for improving performance of the system. In particular, PA is an effective way to save transmit power and improve the coverage and capacity of the system. Some papers analyze full CSI (Channel State Information) for obtaining optimal power allocation. However, this makes the system increasingly complex and presents a practical problem. Thus, there is a need for partial CSI to reduce the complexity. With PSO (Particle Swarm Optimization), individuals referred to as particles are "flown" through hyper-dimensional search space. Changes to the position of a particle within a swarm are influenced by the knowledge of its neighbors. The PSO algorithm maintains a swarm of particles, where each particle represents a potential solution. Therefore, we propose an improved scheme for power allocation in relay-based cooperative wireless communications. For this purpose, we employ partial CSI and PSO algorithms to solve the optimization problem of power allocation with reduced system complexity as well as optimized performance.

This paper develops a general framework for maximum likelihood (ML) demodulation in cooperative wireless communication systems. Demodulators with piecewise-linear combining are proposed as an accurate approximation of the nonlinear ML detectors for coherent and noncoherent decode-and-forward (DF). The detectors with piecewise-linear combiner not only have certain implementation advantages over the nonlinear ML detectors, but also can lead to tight closed-form approximations for their error probabilities. High SNR approximations are derived based on the closed-form BER expressions. For noncoherent DF, the approximation suggests a different optimal location for the relay in DF than for the relay in amplify-and-forward (AF). A set of tight bounds of diversity order for coherent and noncoherent DF with multiple relays is also provided, and comparison between DF and AF suggests that DF with more than one relay loses about half of the diversity order of AF

With the low cost and low hardware complex considerations, cooperative systems are a tendency in the future communications. This work considers the secure cooperative communications systems. For a practical situation in the system, the scenario includes multiple source stations, multiple relay stations, multiple destination stations, and eavesdroppers. To analyze the optimal relay selection in the system, we begin with the performance analysis for a single source station and a single destination station. By applying two cooperative models, the amplify-and-forward (AF) mode and decode-and-forward (DF) mode, the secrecy capacity is derived. Then, we apply the derived results to the considered environment to find the optimal relay assignment. By the way, the relay selection can be obtained by the exhaustive search algorithm. However, there are a lot of steps needed if the number of source stations is large. Hence, applying the characters of the cooperative modes in the relay selection, the pre-selection step is proposed with a mathematical derivation. It could be used for the practical situation without a long-time calculation.