Aymen Omri

Novel cooperative communication schemes with interference management for multi-user wireless networks

Cooperative communication is a promising technique for future wireless networks. It can be used in improving communication reliability, and enhancing power and spectrum efficiency. However, its performance gain degrades in the presence of co-channel interference which makes it essential to propose interference mitigation schemes. In this paper, we introduce two efficient cooperative communication schemes with interference management for multi-user cooperative wireless networks that are based on best relay and user selection (BRUS) technique. BRUS maximizes the received signal to noise ratio (SNR) while minimizing the interference by an optimal time slot allocation for the users. The first introduced scheme is using BRUS technique only if the user demands cooperation, and the second scheme is always using BRUS technique to enhance the system performance. We derive exact closed form expressions for the outage probability, ergodic capacity, average consumed power, and average bit error probability for the introduced cooperative schemes. Simulations are used to validate the analytical results and an agreement is observed. The results confirm the advantage of the introduced cooperation schemes in enhancing the system performance and improving the interference management.

Performance Analysis of OFDMA Based Wireless Cooperative Networks with Interference Management

In this paper, two cooperative communications schemes with interference management are proposed for orthogonal frequency division multiple access (OFDMA) based wireless networks. The first scheme maximizes the received signal to noise ratio (SNR) while keeping the interference levels below a certain threshold, and the second scheme maximizes the received SNR with resource allocation algorithm based . We derive exact closed form expressions for the probability density function (PDF) of the SNR, outage probability, ergodic capacity, average bit error probability, and average consumed power for the proposed cooperative schemes. Simulations are used to validate the analytical results and an agreement is observed. The results confirm the advantage of the introduced schemes in enhancing interference management and in improving spectrum efficiency and link reliability.

Enhanced Alamouti decoding scheme for DVB-T2 systems in SFN channels

The standard Alamouti space-frequency block code (SFBC) suffers from performance degradation when used over highly frequency-selective channels because the channel frequency response is not necessarily flat over the Alamouti block. In this paper, we present an enhanced Alamouti space frequency block decoding scheme for multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems over highly frequency selective channels. The enhanced Alamouti scheme uses the channel frequency variations in consecutive subcarriers to adapt the Alamouti decoder. Simulation results of DVB-T2 system confirm that the proposed method has substantial performance improvement in terms of bit error rate when compared to standard Alamouti decoder mainly over highly frequency-selective channels such as single frequency networks (SFN).

Estimation of highly selective channels for downlink LTE MIMO-OFDM system by a robust neural network

In this contribution, we propose a robust highly se lective channel estimator for downlink Long Term Ev olution (LTE) multiple-input multiple-output (MIMO) orthogonal fr equency division multiplexing (OFDM) system using n eural network. The new method uses the information provid ed by the reference signals to estimate the total f requency response of the channel in two phases. In the first phase, the proposed method learns to adapt to the channel variations, and in the second phase it predicts the channel par ameters. The performance of the estimation method i n terms of complexity and quality is confirmed by theoretical analysis and simulations in an LTE/OFDMA transmissi on system. The performances of the proposed channel estimator are compared with those of least square (LS), decis ion feedback and modified Wiener methods. The simulation results show that the proposed estimator performs better t han he above estimators and it is more robust at high speed mobi lity.

Inter-Relay Interference Management Schemes for Wireless Multi-User Decode-and-Forward Relay Networks

In this paper, two cooperative communications schemes with inter-relay interference (IRI) management are proposed for wireless multi-user decode-and-forward (DF) relay networks. The schemes are based on a DF half-duplex (HD) relaying protocol and a relay selection method which maximizes the signal-to-noise ratio (SNR) of the second hop. To minimize the IRI, the first scheme [constellation real part (CRP)] uses a new transmission scheme based on the constellation real parts of the modulated signals, and the second scheme [previous message buffering (PMB)] uses a buffering technique at the relays. To assess the performance, we derive the expressions of the average bit error rate (BER) for the proposed schemes. Numerical results are given to confirm the analytical expressions and the advantage of the proposed schemes in enhancing interference management for wireless cooperative networks.

Modelling and performance analysis of 3-D heterogeneous cellular networks

Cellular networks are usually described by two-dimensional (2-D) models. These models are appropriate for rural or suburban areas but are not suitable for dense urban environments, where a large number of heterogeneous small cells are deployed to satisfy the rapid increase in mobile subscribers and communication service demands. In this paper, a new general 3-D model for heterogeneous cellular networks is proposed. The 3-D Poisson point process (PPP) is used to describe the positions of the picocells and femtocells in the network. We derive the average coverage probability expressions of downlink heterogeneous cellular networks for a given set of parameters. Monte Carlo simulations are conducted to evaluate the analytical results and the advantage of the proposed 3-D model when compared to the traditional 2-D model. The results confirm the accuracy of the proposed model which presents an efficient description and tractable model of dense small cells deployment in heterogeneous cellular networks.

Interference management schemes with general order statistics and interference constraint for multi-user cooperative wireless networks

In this paper, two cooperative communications schemes with interference management are proposed for multiuser wireless networks. The first scheme (Interference Constraint based Relay Selection (ICRS)) maximizes the received SNR while keeping the interference levels below a certain threshold, and the second scheme (General Order Relay and User Selection (GORUS)) is using channel state informations (CSIs) based resource allocation algorithm to improve the system performance. We derive exact closed form expressions of outage probability, ergodic capacity, and average bit error probability for the proposed schemes. Simulations are used to validate the analytical expressions. The results confirm the advantage of the proposed schemes in enhancing interference management and link reliability.

Performance analysis of cooperative communication system with feedback delay and channel estimation error

In this paper, we investigate the impact of feedback delay and channel estimation error (CEE) on the performance of wireless multi-user decode-and-forward (DF) relay systems in independent and non identically distributed Rayleigh fading channels. To assess the performance, we derive the exact probability density function (PDF) expression of the signal-to-noise ratio (SNR) for each link, and the average outage probability expression with imperfect channel state information (ICSI). Numerical results are presented to confirm the analytical expressions and to investigate the effect of the ICSI on the performances of the wireless cooperative system.

Estimation of highly selective channels for downlink LTE system by a robust neural network

In this paper we propose a robust channel estimator for Long Term Evolution (LTE) downlink highly selective using neural network. This method uses the information provided by the reference signals to estimate the total frequency response of the channel in two phases. In the first phase, the proposed method learns to adapt to the channel variations, and in the second phase it predicts the channel parameters. The performance of the estimation method in terms of complexity and quality is confirmed by theoretical analysis and simulations in an LTE/OFDMA transmission system. The performance of the proposed channel estimator are compared with those of least square (LS), decision feedback and modified Wiener methods. The simulation results show that the proposed estimator performs better than the above estimators and it is more robust at high speed mobility.

Effective area spectral efficiency metric for decode-and-forward cooperative wireless communications

In this paper, we introduce a new metric, namely: effective area spectral efficiency (EASE), to quantify the spectral efficiency as well as the spatial properties of decoding and forward (DF) relaying wireless communications networks with interference management. The EASE metric is based on the average affected area, the average ergodic capacity, and a new introduced index, namely: source relay communication index (SRCndx). We derive a closed-form expression for the maximum transmission range under Rayleigh fading environment. Based on the maximum transmission range, we define and derive the average affected area and the average ergodic capacity for DF relaying communications system. The SRCndx is used to validate the communication possibility between a source and a relay for given transmission parameters in a given environment, and provides information about the necessity of using relaying communications. We then introduce the EASE expression to quantify the spatial spectral utilization efficiency. Through mathematical analysis and numerical examples, we show that the EASE metric provides a new perspective on the design and optimization of wireless transmissions, especially the transmission power selection process.