yamen issa | Université de Valenciennes et du Hainaut-Cambrésis (UVHC) (original) (raw)
Papers by yamen issa
Http Www Theses Fr, Dec 2, 2013
Wireless networks continue to gain popularity over wired networks while their users do not stop t... more Wireless networks continue to gain popularity over wired networks while their users do not stop to grow their demands for high data rates. The new researches in this field try to meet these demands with the new orientation of the industry towards low cost, low power consumption and multifunctional small devices. Therefore, designer and researchers face a compromise between these goals and the required quality of service (QoS). In wireless network, multipath fading severely corrupts the link performance. Indeed, as a signal propagates through a wireless channel, it incurs random fluctuations in time, reflections, and attenuation due to the wireless link nature and the arbitrarily movement of the users. Multiple input multiple output (MIMO) system is an effective countermeasure to combat multipath effects and to provide spatial diversity to the receiver. But it requires the implementation of physically separated antennas in order to have independent fading effects. Theoretically, MIMO systems increase the capacity of wireless links compared to systems with single transmit or receive antenna (SISO). In the same context, ultra wideband (UWB) technology offers unique qualities such as the unlicensed re-utilization of the allocated spectrum. This technology can underlay existing radio systems using signal with low power and quasi flat power spectral densities (PSD). In addition, UWB signals occupy wide bandwidth leading to fine time resolution which can be employed for localization applications as well as a high capacity and data rates. All these advantages make this technology a very interesting choice for low and high rate communication in different applications. Motivated by the aim to answer to the new demands in the field of wireless communication while preserving simplicity, low cost, and low power consumption; we propose to use cooperative diversity in conjunction with UWB technology in wireless networks. Cooperative diversity is indeed an alternative of the well-known diversity techniques where instead of installing multiple antennas on each node, these nodes can share their antennas to relay each other's signal in such a way that they form a virtual antenna array (virtual MIMO system). To show the benefits of the proposed solution, we study an UWB system with cooperation schemes in multipath environment using decode-and-forward (FD) relaying protocol. Next, we compare the bit error performance of the proposition with the case of non-cooperative UWB communication in same environment. We consider, respectively, time hopping pulse position modulation (TH-PPM) and direct sequence binary phase shift keying (DS-BPSK) systems. Due to the high number of multipath components (MPCs) in UWB channel, we refer to use partial Rake (P-Rake) receiver in our simulation. We analytically analyze the decision variable at the output of Rake receiver and present simulation results of the BER performance of these two systems under different UWB channel considering the IEEE 802.15.4a standard, more precisely, residential and office line-of-sight (LOS) and non-line-of-sight (NLOS) channel environments. Our results show that the relay cooperation significantly improves the performance of the two systems under different scenarios, and that the diversity gain increases proportionally with the number of cooperative relays. Increasing the number of fingers in a RAKE receiver will enhance the systems performance but will, unfortunately, increase the complexity of the design. In order to remedy this problem, we can use selective Rake (S-RAKE) receiver, which combines the best MPCs of the received signal. In presence of multiple access interference (MAI), our results show that the overall system performance degrades significantly, but the benefit of cooperation is still moderately effective. The performance in this case is limited in terms of attainable diversity that the source-relay link becomes worse when MAI is present. Hence, if better reliability is achieved at the relay nodes, the diversity may be improve, or may even be maintained. In light of this, we propose to employ antenna selection at the relay receiver in order to improve the reliability of the source-relay link. We assume that the relay node is equipped with multiple antennas and the receiver selects the best antenna which corresponds to the best sub-channel between the source and the relay out of the available sub-channels. The proposal based on the principle of antenna selection can maintain a good performance in the presence of AMI. The consequence of this is that, while leveraging the benefits of the available antennas at the relay, the number of radio frequency (RF) chains is reduced to the number of selected antennas, which leads to reduced cost and complexity.
Le multiplexage en polarisation fait partie des diverses techniques fortement envisagées pour aug... more Le multiplexage en polarisation fait partie des diverses techniques fortement envisagées pour augmenter l'efficacité spectrale des futurs systèmes de communications optiques. Cependant, outre les difficultés liées à l'émission et à la réception de ces signaux optiques complexes, se pose le problème de leur amplification tout-optique, notamment à base de SOA (Semiconductor Optical Amplifier). Ce type de multiplexage dans une chaîne utilisant l'amplification par des SOA – composant intrinsèquement non-linéaire – n'est pas sans présenter une certaine analogie avec les systèmes de transmissions radiofréquences. Dans ce cas, l'emploi des techniques MIMO permet de tirer parti de la diversité engendrée par la polarisation. C'est pourquoi nous présentons dans cette communication les résultats d'une étude sur l'emploi de méthodes MIMO pour la transmission et l'amplification par un SOA de signaux multiplexés en polarisation.
Http Www Theses Fr, Dec 2, 2013
Wireless networks continue to gain popularity over wired networks while their users do not stop t... more Wireless networks continue to gain popularity over wired networks while their users do not stop to grow their demands for high data rates. The new researches in this field try to meet these demands with the new orientation of the industry towards low cost, low power consumption and multifunctional small devices. Therefore, designer and researchers face a compromise between these goals and the required quality of service (QoS). In wireless network, multipath fading severely corrupts the link performance. Indeed, as a signal propagates through a wireless channel, it incurs random fluctuations in time, reflections, and attenuation due to the wireless link nature and the arbitrarily movement of the users. Multiple input multiple output (MIMO) system is an effective countermeasure to combat multipath effects and to provide spatial diversity to the receiver. But it requires the implementation of physically separated antennas in order to have independent fading effects. Theoretically, MIMO systems increase the capacity of wireless links compared to systems with single transmit or receive antenna (SISO). In the same context, ultra wideband (UWB) technology offers unique qualities such as the unlicensed re-utilization of the allocated spectrum. This technology can underlay existing radio systems using signal with low power and quasi flat power spectral densities (PSD). In addition, UWB signals occupy wide bandwidth leading to fine time resolution which can be employed for localization applications as well as a high capacity and data rates. All these advantages make this technology a very interesting choice for low and high rate communication in different applications. Motivated by the aim to answer to the new demands in the field of wireless communication while preserving simplicity, low cost, and low power consumption; we propose to use cooperative diversity in conjunction with UWB technology in wireless networks. Cooperative diversity is indeed an alternative of the well-known diversity techniques where instead of installing multiple antennas on each node, these nodes can share their antennas to relay each other's signal in such a way that they form a virtual antenna array (virtual MIMO system). To show the benefits of the proposed solution, we study an UWB system with cooperation schemes in multipath environment using decode-and-forward (FD) relaying protocol. Next, we compare the bit error performance of the proposition with the case of non-cooperative UWB communication in same environment. We consider, respectively, time hopping pulse position modulation (TH-PPM) and direct sequence binary phase shift keying (DS-BPSK) systems. Due to the high number of multipath components (MPCs) in UWB channel, we refer to use partial Rake (P-Rake) receiver in our simulation. We analytically analyze the decision variable at the output of Rake receiver and present simulation results of the BER performance of these two systems under different UWB channel considering the IEEE 802.15.4a standard, more precisely, residential and office line-of-sight (LOS) and non-line-of-sight (NLOS) channel environments. Our results show that the relay cooperation significantly improves the performance of the two systems under different scenarios, and that the diversity gain increases proportionally with the number of cooperative relays. Increasing the number of fingers in a RAKE receiver will enhance the systems performance but will, unfortunately, increase the complexity of the design. In order to remedy this problem, we can use selective Rake (S-RAKE) receiver, which combines the best MPCs of the received signal. In presence of multiple access interference (MAI), our results show that the overall system performance degrades significantly, but the benefit of cooperation is still moderately effective. The performance in this case is limited in terms of attainable diversity that the source-relay link becomes worse when MAI is present. Hence, if better reliability is achieved at the relay nodes, the diversity may be improve, or may even be maintained. In light of this, we propose to employ antenna selection at the relay receiver in order to improve the reliability of the source-relay link. We assume that the relay node is equipped with multiple antennas and the receiver selects the best antenna which corresponds to the best sub-channel between the source and the relay out of the available sub-channels. The proposal based on the principle of antenna selection can maintain a good performance in the presence of AMI. The consequence of this is that, while leveraging the benefits of the available antennas at the relay, the number of radio frequency (RF) chains is reduced to the number of selected antennas, which leads to reduced cost and complexity.
Le multiplexage en polarisation fait partie des diverses techniques fortement envisagées pour aug... more Le multiplexage en polarisation fait partie des diverses techniques fortement envisagées pour augmenter l'efficacité spectrale des futurs systèmes de communications optiques. Cependant, outre les difficultés liées à l'émission et à la réception de ces signaux optiques complexes, se pose le problème de leur amplification tout-optique, notamment à base de SOA (Semiconductor Optical Amplifier). Ce type de multiplexage dans une chaîne utilisant l'amplification par des SOA – composant intrinsèquement non-linéaire – n'est pas sans présenter une certaine analogie avec les systèmes de transmissions radiofréquences. Dans ce cas, l'emploi des techniques MIMO permet de tirer parti de la diversité engendrée par la polarisation. C'est pourquoi nous présentons dans cette communication les résultats d'une étude sur l'emploi de méthodes MIMO pour la transmission et l'amplification par un SOA de signaux multiplexés en polarisation.