Performance of Multi-relay Cooperative Communication Using Decode and Forward Protocol

Nowadays, the development of wireless communication systems will be refer to user cooperative communication system in which a source information can transmit data to a destination through a relay. This can reduce the effect of fading on wireless communication channel which is a major problem in wireless communication system that can degrade the system performance. In this paper, we investigate the performance of multi-relay cooperative communication using decode and forward protocol in terms of channel capacity, bit error rate (BER) and throughput. The use of decode and forward protocol in multi-relay cooperative communication offers cooperation among users to generate virtual multiple antennas to increase the channel capacity and also can give better system performance. Furthermore, the simulation model of the system and computer simulation is developed to evaluate the performance of multi-relay cooperative communication. The simulation result shows that the channel capacity increases as the value of signal to noise ratio (SNR) increases. Also, the channel capacity increases as the number of relays increases. Moreover, the performance of multi-relay cooperative communication performs better than a single-relay cooperative communication by using decode and forward protocol in terms of BER. Furthermore, multi-relay cooperative communication provides a good throughput of the system compared to a single-relay. Therefore, the multi-relay cooperative communication is useful to mitigate the effects of channel fading, increase the channel capacity, improve the system performance and provide a good throughput by exploiting decode and forward protocol

Performance of multi-relay cooperative communication using decode and forward protocol

Nowadays, the development of wireless communication systems will be refer to user cooperative communication system in which a source information can transmit data to a destination through a relay. This can reduce the effect of fading on wireless communication channel which is a major problem in wireless communication system that can degrade the system performance. In this paper, we investigate the performance of multi-relay cooperative communication using decode and forward protocol in terms of channel capacity, bit error rate (BER) and throughput.  The use of decode and forward protocol in multi-relay cooperative communication offers cooperation among users to generate virtual multiple antennas to increase the channel capacity and also can give better system performance. Furthermore, the simulation model of the system and computer simulation is developed to evaluate the performance of multi-relay cooperative communication. The simulation result shows that the channel capacity increases as the value of signal to noise ratio (SNR) increases. Also, the channel capacity increases as the number of relays increases. Moreover, the performance of multi-relay cooperative communication performs better than a single-relay cooperative communication by using decode and forward protocol in terms of BER. Furthermore, multi-relay cooperative communication provides a good throughput of the system compared to a single-relay. Therefore,  the multi-relay cooperative communication is useful to mitigate the effects of channel fading, increase the channel capacity, improve the system performance and provide a good throughput by exploiting decode and forward protocol

Power allocation strategies for distributed precoded multicell based systems

Multicell cooperation is a promising solution for cellular wireless systems to mitigate intercell interference, improve system fairness, and increase capacity. In this article, we propose power allocation techniques for the downlink of distributed, precoded, multicell cellular-based systems. The precoder is designed in two phases: first the intercell interference is removed by applying a set of distributed precoding vectors; then the system is further optimized through power allocation. Three centralized power allocation algorithms with per-BS power constraint and diferente complexity trade-offs are proposed: one optimal in terms of minimization of the instantaneous average bit error rate (BER), and two suboptimal. In this latter approach, the powers are computed in two phases. First, the powers are derived under total power constraint (TPC) and two criterions are considered, namely, minimization of the instantaneous average BER and minimization of the sum of inverse of signal-to-noise ratio. Then, the final powers are computed to satisfy the individual per-BS power constraint. The performance of the proposed schemes is evaluated, considering typical pedestrian scenarios based on LTE specifications. The numerical results show that the proposed suboptimal schemes achieve a performance very close to the optimal but with lower computational complexity. Moreover, the performance of the proposed per-BS precoding schemes is close to the one obtained considering TPC over a supercell.Portuguese CADWIN - PTDC/ EEA TEL/099241/200

Single and multiple antenna relay-assisted techniques for uplink and downlink OFDM systems

In this paper we propose and assess the performance of relay-assisted schemes designed for both the uplink and downlink OFDM based systems, using efficient distributed space-frequency block coding protocols. We consider the use of an antenna array at the base station and a single antenna at the user terminal. At the relay node we consider either single antenna or an antenna array. We assume that some of the user terminals deployed in a certain area could act as relaying-able terminals for the communication of other users. Two types of relay-assisted protocols are considered: equalize-and-forward and decode-and-forward. The optimal maximum ratio combining coefficients are derived for the proposed relay-assisted schemes. The performance of these cooperative schemes is evaluated under realistic scenarios, considering typical pedestrian scenarios based on WiMAX specifications and using channel convolutional turbo code. The proposed schemes are also compared against the non-cooperative OFDM based systems. +umerical results show that the availability of antenna arrays at the relays significantly improves the cooperative systems performance, which outperform the non-cooperative ones in most studied scenarios

Performance Analysis of Hybrid Decode-Amplify-Forward (HDAF) Relaying for Improving Security in Cooperative Wireless Network

In present communication scenario, security and privacy of data being transmitted is very difficult due to the openness of wireless medium. To secure and protect the confidentiality of data being transmitted, physical layer security offers attractive solutions using cooperative relaying schemes, in which relay assists the transmission of data between source and destination. In this work, we consider a cooperative wireless network in which relay either tries to improve the channel capacity of source to destination link using cooperative relaying protocols or reduce the channel capacity of source to eavesdropper link using jamming techniques. In order to improve the performance of the communication system, optimal relay and jammer are selected based on the three proposed relay and jamming selection schemes namely Conventional selection (Without jamming), Optimal selection with jamming (OSJ) and Optimal selection with control jamming (OSCJ).Optimal relay forwards the source information using cooperating relaying protocols such as decode and forward(DF), Amplify and Forward(AF) ,Hybrid decode amplify forward (HDAF) which combines the benefits of both DF and AF schemes. At the same time, jammer generates artificial noise using cooperative jamming scheme, to confuse the eavesdropper. The received signals at the receiver are combined using the various diversity techniques such as maximum ratio combining (MRC) and fixed ratio combining (FRC) techniques.Monte Carlo simulations are carried out and the obtained results are compared for different relay,jammer and eavesdropper locations. A study of comparison is made in terms of secrecy capacity and intercept probability for the proposed relaying schemes in the presence of single eavesdropper. Finally from the simulated comparison study, it is observed that HDAF scheme outperforms AF and DF schemes and we can also observe control jamming selection achieves more secrecy rate compared to without jamming and with optimal jamming

Who wrote this scientific text?

The IEEE bibliographic database contains a number of proven duplications with indication of the original paper(s) copied. This corpus is used to test a method for the detection of hidden intertextuality (commonly named "plagiarism"). The intertextual distance, combined with the sliding window and with various classification techniques, identifies these duplications with a very low risk of error. These experiments also show that several factors blur the identity of the scientific author, including variable group authorship and the high levels of intertextuality accepted, and sometimes desired, in scientific papers on the same topic

L'intertextualité dans les publications scientifiques

La base de données bibliographiques de l'IEEE contient un certain nombre de duplications avérées avec indication des originaux copiés. Ce corpus est utilisé pour tester une méthode d'attribution d'auteur. La combinaison de la distance intertextuelle avec la fenêtre glissante et diverses techniques de classification permet d'identifier ces duplications avec un risque d'erreur très faible. Cette expérience montre également que plusieurs facteurs brouillent l'identité de l'auteur scientifique, notamment des collectifs de chercheurs à géométrie variable et une forte dose d'intertextualité acceptée voire recherchée

16-QAM Hierarchical Modulation Optimization in Relay Cooperative Networks

16-QAM Hierarchical Modulation Optimization in Relay Cooperative Networks Sara Sallam Recently, the concept of cooperative networks has attracted special attention in the field of wireless communications. This is due to their ability in achieving diversity with no extra hardware cost. The main drawback that characterizes cooperative networks is that they require extra transmission time slots compared to the traditional non-cooperative networks. Several strategies have been proposed in order to mitigate this disadvantage. One of the most recently adopted techniques is the use of hierarchical modulation. Hierarchical modulation was originally used in Digital Video Broadcast (DVB) applications. Lately, it has been applied in cooperative networks for its ability to transmit relative high data rate with acceptable performance. In this thesis, the application of a 4/16 QAM hierarchical modulation in cooperative networks is examined. This study focuses on a downlink cellular network scenario, composed of a Base Station, a Relay and two destinations. The Base Station intends to transmit two different streams of data to these two destinations by concatenating the two streams and broadcasting the resulting sequence using a non-uniform 4/16 QAM hierarchical modulation. Unlike previous work, the main contribution in this thesis is the optimization of the 16QAM constellation’s parameters according to each user’s channel condition. In other words, this method gives each user’s data the priority it needs in order to be detected as correctly as possible at the destination. Explicit closed form expressions of Hierarchical modulation Bit Error Rate in relay cooperative networks are derived. These BER expressions are used in order to select the constellation’s parameters that will achieve total minimum BER in coded and un-coded schemes. Results prove that the proposed method achieve noticeable improvement in both users performance compared to the use of uniform 16QAM constellation