Papers by Fakhreddine Gaaloul
2015 IEEE Global Communications Conference (GLOBECOM), 2014
This paper develops analytical models to investigate the impact of various operation terms and pa... more This paper develops analytical models to investigate the impact of various operation terms and parameters on the downlink performance of spectrum-shared overlaid networks under closed-access small cells deployment. It is considered that closed-access small cells (i.e., femtocells) can not reuse available channels, and can serve only active authorized user equipments (UEs). On the other hand, the macrocell base station can unconditionally reuse available channels to serve active macrocell UEs. The analysis characterizes UEs identities, their likelihoods of being active, and their likelihoods of initiating interference. Moreover, it quantifies interference sources observed from effective femtocells considering their over-loaded and under-loaded cell scenarios. The developed results to characterize an active UE performance and the impact of the number of available channels are thoroughly examined. The obtained results are generally applicable for any performance measure and any network channel models. Numerical and simulation examples are presented to clarify the main outcomes of this paper.
Communications, IET, 2012
Abstract This study investigates different receive single-branch switch-based diversity schemes f... more Abstract This study investigates different receive single-branch switch-based diversity schemes for dual-hop amplify-andforward relaying networks. Specifically, three receive processing algorithms are adopted, in which the receive branch is selected using the arbitrary selection algorithm, the switching algorithm, or the switching algorithm with post-examining best branch selection. The identification of the receive branch is carried out for two different system models. For the first model, a single-antenna relaying station is used ...
ieeexplore.ieee.org
Abstract—This paper proposes adequate methods to improve the interference mitigation capability o... more Abstract—This paper proposes adequate methods to improve the interference mitigation capability of a recently investigated switched-based interference reduction scheme in short-range open-access and over-loaded femtocells. It is assumed that the available orthogonal channels for the femtocell network are distributed among operating access points in close vicinity, where each of which knows its allocated channels a priori. For the case when the feedback links are capacity-limited and the available channels can be universally shared ...
ieeexplore.ieee.org
Abstract This correspondence investigates an adaptive scheduling algorithm for multiuser environm... more Abstract This correspondence investigates an adaptive scheduling algorithm for multiuser environments with statistically independent but non-identically distributed (ind) channel conditions. The algorithm aims to reduce the feedback load by examining the users channels sequentially and arbitrarily. It also provides improved performance by realizing a post-examining best user selection. The first part of the correspondence presents new formulations for the statistics of the signal-to-noise ratio (SNR) of the scheduled user ...
This letter investigates the performance of a cognitive radio transceiver that can opportunistica... more This letter investigates the performance of a cognitive radio transceiver that can opportunistically use the available channel. We propose and compare two different opportunistic channel access schemes. The first scheme applies when the secondary user (SU) has access to only one channel. The second scheme is based on switching between available channels and applies when the SU has access to multiple channels but can at a given time monitor and access only one channel. For these proposed access schemes, we derive analytical expressions of the novel metrics of the average access duration and the average waiting time for a general primary user traffic model. Based on these two metrics a time-average secondary access throughput formula is presented to predict the performance of the SU.
… Wireless Networks and …, 2012
Cognitive Radio (CR) technology is envisaged to solve the problems in wireless networks resulting... more Cognitive Radio (CR) technology is envisaged to solve the problems in wireless networks resulting from the limited available spectrum and the inefficiency in the spectrum usage by exploiting the existing wireless spectrum opportunistically. CR networks, equipped with the intrinsic capabilities of the cognitive radio, will provide an ultimate spectrum aware communication paradigm in wireless communications. Such networks, however, impose unique challenges due to the high fluctuation in the available spectrum as well as diverse Quality-of-Service (QoS) requirements. Specifically, in Cognitive Radio Ad Hoc Networks (CRAHNs), the distributed multi-hop architecture, the dynamic network topology, and the time and location varying spectrum availability are some of the key distinguishing factors. In this paper, current research challenges of the CRAHNs are presented. First, spectrum management functionalities such as spectrum sensing, spectrum sharing, and spectrum decision, and spectrum mobility are introduced from the viewpoint of a network requiring distributed coordination. Moreover, the influence of these functions on the performance of the upper layer protocols are investigated and open research issues in these areas are also outlined. Finally, the proposed tools, and best simulator to solve research challenges in spectrum management are explained. This gives an insight in choosing the suitable tool, and the suitable simulator that fit for solving different challenges.
IEEE Transactions on Vehicular Technology, Jan 1, 2012
Rights Archived with thanks to IEEE Transactions on Vehicular Technology Downloaded 4-Dec-2016 03... more Rights Archived with thanks to IEEE Transactions on Vehicular Technology Downloaded 4-Dec-2016 03:37:28
We investigate the performance of a multiuser downlink access scheme based on a post-selection sw... more We investigate the performance of a multiuser downlink access scheme based on a post-selection switch and examine algorithm. The studied scheme sequentially switches over the users that experience independent and non-identically distributed fading conditions, and selects a single user with an acceptable channel quality as compared to a pre-selected signal-to-noise ratio (SNR) threshold. If no one of the users can satisfy the target channel quality, the base station (BS) takes the advantage of the knowledge of all users channels and serves the user with the best channel quality among all users. This scheme reduces considerably the feedback load but offers a lower average spectral efficiency (ASE) as compared to that of the full feedback system with instantaneous best user selection. On the other hand, it improves the system performances, such as outage probability and average bit error rate (BER), as compared to a system that is based on a standard switching scheme without post-selection. Numerical results for the ASE average BER, and average feed back load, are presented for the cases of outdated and non-outdated rate-adaptive modulation scheme operating over independent and non-identically distributed users.
This paper investigates the effect of different switched diversity configurations on the implemen... more This paper investigates the effect of different switched diversity configurations on the implementation complexity and achieved performance of dual-hop amplify-and-forward (AF) relaying networks. A low-complexity model of the relay station is adopted, wherein single-input single-output antenna configuration is employed. Each of the transmitter and the receiver however employs multiple antennas to improve the overall link performance. Single-phase and two-phase based receive switching strategies are investigated assuming optimum first hop signal-to-noise ratio (SNR). Moreover, the simple scheme in which the switched diversity is applied independently over the two hops is studied using tight upper bounds. Thorough performance comparisons and switching thresholds optimization for the aforementioned strategies are presented. Simulation results are also provided to validate the mathematical development and to verify the numerical computations.
This paper investigates the performance of different low-complexity combining schemes in the cont... more This paper investigates the performance of different low-complexity combining schemes in the context of dual-hop amplify-and-forward relaying networks. It is assumed that the relay uses single transmit (receive) antenna due to space limitation and to reduce the processing complexity. On the other hand, the transmitter and the receiver use antenna arrays to improve the overall diversity gain. However, this gain is achieved at the expense of increased processing complexity and power consumption. To this end, some combining schemes aiming at reducing the processing complexity and decreasing the number of active receive channels are investigated. Through the analysis, new formulas for the end-to-end signal-to-noise ratio statistics in slowly varying and frequency flat Rayleigh fading channels are derived, which are then used to present some performance measures. Numerical and simulation results are presented to clarify the trade-off between the achieved diversity gain and the receive processing complexity.
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Papers by Fakhreddine Gaaloul