Abdurrahman Alfitouri

Performance Analysis of Optimal Relay Power Control in MIMO System

In this paper, we study the performance of a wireless communication system, where an arbitrary number of amplify-and-forward relays cooperate to enhance the signal between source and destination. The source and destination are hidden from each other, and there is no direct link between them. Optimal relay power control (ORPC) is introduced as an effective scheme to achieve cooperative diversity. This paper develops a new and more accurate model for the ORPC scheme in multiple antenna relays scenario, and takes into account the effects of fading and thermal noise at both the relays and destination. This leads to the derivation of new analytical expressions for the overall spectral efficiency which can be used to estimate the throughput, and to study the impact of different system parameters on efficiency. The accuracy of the new mathematical results is confirmed by Monte Carlo simulation.

Multiple-Access Capabilities of a Common Gateway

This paper is concerned with the performance analysis of a dual-hop random access network, where a single gateway is employed to connect a random number of independent users which are hidden from their destination(s). The gateway is an amplify-and-forward (AF) relay and is the only mean to connect users to their destinations. We develop accurate mathematical models for the multiple access interference, which take into account, in addition to the distribution of the number of active users and their random locations, the effects of fading and thermal noise at both the relay and destinations. A new unified mathematical method is developed, which leads to the derivation of new analytical expressions for the overall spectral efficiency of the dual-hop random access network over Rayleigh- and Nakagami- m fading channels. The accuracy of the new mathematical results is confirmed by Monte Carlo simulation. The results of this paper can be used to estimate the aggregate throughput of a dual-hop system employing the slotted-Aloha-type protocols.

Multiple-access capabilities of AF relaying with zero forcing

In this paper, we explore the multiple access capabilities of amplify and forward (AF) gateways employing zero forcing (ZF) beamforming techniques in a space division multiple access (SDMA) scenario. A random number of users are isolated from their destination, and the only mean to communicate with their destination(s) is through the AF gateway equipped with multiple antennas, and employing ZF beamforming technique. The channels experience both small and large-scale fading. New exact analytical expressions are derived for the overall spectral efficiency (SE) in the collaborative and non-collaborative scenarios, where in the first case ZF is applied at the sources and destinations, whereas in the latter case ZF is implemented at the gateway. The new results is used to investigate the impact of different system parameters into the overall efficiency of ZF gateways. The accuracy of the new results is confirmed through comparison with Monte Carlo simulations.

Multiple-Access Capabilities of Amplify-and-Forward Relaying

This paper is concerned with the performance of a gateway connecting a group of independent users to their destinations and employ the random slotted- Aloha type protocol. The users are isolated from their destinations and the only way to communicate with their destinations is through the common gateway which acts as a blind amplify and forward relay. Users are randomly distributed around the gateway and experience a Rayleigh or Nakagami-m fading channels. This paper develops a new accurate models for the multiple access interference at both the gateway and the destinations taking into account, in addition to the random number of the active users and their locations, the effects of fading and thermal noise at both the relay and the destinations. This leads to the derivation of new analytic expressions for the overall spectral efficiency which can be used to estimate the throughput of the aloha based gateways in Rayleigh and Nakagami-m fading channels and to study the impact of the different system parameters into their efficiency. The accuracy of the new mathematical results is confirmed by Monte Carlo simulation.

Cooperative Diversity Using Optimal Relay Power Control for Different Fading Channels

In this paper, we study the performance of a wireless communication system, where an arbitrary number of relays cooperate to enhance the signal between source and destination. The source and destination are hidden from each other, and there is no direct link between them. Optimal Relay Power Control (ORPC) is introduced as an effective scheme to achieve cooperative diversity, where there is a trade-off between complexity and system performance. This paper develops a new and more accurate model for the ORPC scheme and takes into account the effects of fading and thermal noise at both the relays and destination. This leads to the derivation of new analytical expressions for the overall spectral efficiency which can be used to estimate the throughput of the ORPC in Rayleigh and Nakagami-m fading channels, and to study the impact of different system parameters on efficiency. The accuracy of the new mathematical results is confirmed by Monte Carlo simulation. The results of this paper can be used to estimate the aggregate throughput of a dual-hop system employing the ORPC protocols.

Performance Modeling and Analysis of AF Relaying with Hidden Nodes

In this paper, we investigate and analyse the performance of amplify and forward (AF) relay system connecting a group of independent sources to their destinations employing a random carrier sense multiple access (CSMA) protocol. The sources are isolated from their destination and the only means for them to communicate with their destination is through the common relay. Sources are arbitrarily distributed around the relay and experience Rayleigh fading channels. This paper develops a new and more accurate model for multiple access interference at both the relay and destination which takes into account random sources location and the effects of fading and thermal noise at both the relay and destination. Moreover, the effect of the hidden nodes on the system performance is considered as a randomly occurring factor. This leads to the derivation of new analytical expressions for the overall spectral efficiency (SE) which can be used to estimate the throughput of the CSMA-based relay in Rayleigh fading channels and to study the impact of the different system parameters on their efficiency. The accuracy of the new mathematical results is confirmed by Monte Carlo simulation.

Performance Analysis of Adaptive Power Technique for Cooperative Diversity Communications

Cooperative diversity is a promising technique for use in wireless networks because it can provide diversity gain without the need to install multiple antennas at the source or destination. This paper is concerned with the performance analysis of a dual-hop random access network employed adaptive power technique (APT) relay in cooperative diversity networks. The network considered uses amplify-and-forward relaying, and is the only mean to connect source to its destination. This scheme is compared with such popular schemes as the orthogonal scheme, best relay selection, maximal ratio transmission (MRT) and the optimum combining scheme. A new unified mathematical method is developed, which leads to the derivation of new analytical expressions for the overall spectral-efficiency of the dual-hop random access network over Rayleigh fading channels. Numerical results show that the APT can benefit from an increase in the number of relays and reduction of the noise power at the relay and destination. The results also show that the performance of the APT is comparable to the other cooperative schemes, except the MRT. Furthermore, the new mathematical results obtained for APT have been confirmed by Monte Carlo simulation.

Amplify-and-Forward Gateway With Zero-Forcing in Multiuser Environments

In this paper, we investigate and analyze the performance of amplify-and-forward (AF) gateways employing zero-forcing (ZF) beamforming techniques in a space division multiple access (SDMA) scenario. A random number of users are isolated from their destination(s), and the only means to communicate with their destination(s) is through the AF gateway equipped with multiple antennas and employing the ZF beamforming technique. All forward and backward channels experience small- and large-scale fading. New exact analytical expressions are derived for the overall spectral efficiency in the collaborative and noncollaborative SDMA scenarios. In the latter case, ZF is implemented at the gateway only, whereas with regard to the collaborative scenario, ZF is applied at both the sources and the destinations. The new results are used to investigate the impact of different system parameters on the overall efficiency of ZF AF gateways. The accuracy of the new results is confirmed through Monte Carlo simulations.

User selection scheme for amplify-and-forward relaying with zero forcing

In this paper, we report the results of an investigation and analysis of the performance of amplify and forward (AF) gateways employing zero forcing (ZF) beamforming techniques in a space division multiple access scenario. A random number of users are isolated from their destination(s) and can communicate with them only through an AF gateway equipped with multiple antennas and employing a ZF beamforming technique. The channels experience both small and large-scale fading. For large numbers of users, we introduce User Selection and Group Selection schemes, to keep the number of users less than or equal to the number of relay antennas in each group, with the goal of improving system performance. New, exact analytical expressions are derived for the overall spectral efficiency. The new results are used to investigate the impact of different system parameters on the overall efficiency of ZF gateways. The accuracy of the new results is confirmed through comparison with Monte Carlo simulations.