Proceedings of the 21st ACM International Conference on Modeling, Analysis and Simulation of Wireless and Mobile Systems
Device-to-device (D2D) communications is a promising technique for improving the efficiency of 5G... more Device-to-device (D2D) communications is a promising technique for improving the efficiency of 5G networks. Employing channel adaptive resource allocation can yield to a large enhancement in almost any performance metric of D2D communications (e.g. Energy Efficiency). Centralized approaches require the knowledge of D2D links' Channel State Information (CSI) at the BS level. However, CSI reporting suffers from the limited number of resources available for feedback transmission. Alternately, we propose a distributed algorithm for resource allocation that benefits from the users' knowledge of their local CSI in order to minimize the users' transmission power while maintaining predefined throughput constraint. The key idea is that users compute their local performance metrics (e.g. energy efficiency) and then use a new signaling mechanism to share these values between each other. Under some condition, the performance of this distributed algorithm achieves that of theideal scheduling (i.e. with a global CSI knowledge of all the D2D links). We describe how this technique can be simply implemented by adapting existing CSI reporting (e.g. in Long-Term Evolution (LTE) systems). Furthermore, numerical results are presented to corroborate our claims and demonstrate the gain that the proposed distributed scheduling brings to cellular networks compared to the bestcentralized-limited feedback scheduling.
IEEE Transactions on Wireless Communications, 2021
This paper considers the problem of fully distributed channel allocation in clustered wireless ne... more This paper considers the problem of fully distributed channel allocation in clustered wireless networks when the propagation medium is random. We extend here the existing Trial and Error (TE) framework developed in the deterministic case and for which strong convergence properties hold. We prove that using directly this solution in the random context leads to unsatisfactory solutions. Then we propose an adaptation of the original Trial and Error Learning (TEL) algorithm, called Robust TEL (RTEL), assuming that the random channel effects translate into a bounded stochastic disturbance of the utility function. The solution consists in introducing thresholds in the transitions of the TEL’s Finite State Controller (FSC). We prove that this new solution restores the good convergence property inherited from the TEL. Furthermore, we provide analysis of the stochastic utilities in the Rayleigh fading case in order to check the bounded assumption. Finally, we develop an online algorithm that dynamically estimates the optimal threshold values to adapt to the instantaneous disturbance. Numerical results corroborate our theoretical claims.
2021 IEEE Wireless Communications and Networking Conference (WCNC), 2021
Reconfigurable intelligent surfaces (RIS) technology, as the name implies, is a grid of many smal... more Reconfigurable intelligent surfaces (RIS) technology, as the name implies, is a grid of many small intelligent surfaces that can be reconfigured. It is a new and promising concept in wireless communications, expected to help realize the requirements of the future cellular generations. Numerous studies have been done to prove its added advantages and to control these surfaces in beneficial ways. However, these control schemes come with difficulties related to efficient and practical implementation. In this paper, we propose to control multiple RISs in a multi-user scheme with an algorithm that leads to a simple implementation. We formulate a stochastic optimization problem and we propose a new method using a distributed stochastic algorithm that allows the optimization to be done locally at each RIS with low computational requirements and without the need for instantaneous channel knowledge at the RIS. Also, the signaling between the base station (BS) and each RIS is limited to the exchange of a scalar only. Simulation results prove the success and efficiency of this algorithm.
2021 IEEE Wireless Communications and Networking Conference (WCNC), 2021
The initial access in 5G New Radio (NR) standalone millimeter wave (mmWave) uses the techniques o... more The initial access in 5G New Radio (NR) standalone millimeter wave (mmWave) uses the techniques of beam sweeping to Figure out appropriate directions of transmission and reception. Beam sweeping refers to the transmission of cell specific signals by the base station (BS) while switching beam direction in a sequential manner in order to cover the whole cell. The conventional beam sweeping consists of transmitting sequentially and periodically the beams, according to a fixed pattern, which results in an initial access latency. The aim of this paper is to minimize the overall number of timeslots needed to connect all users to the BS by allowing using multiple beams in some slots and then activating the beams in a prioritized and controlled manner rather than sequentially and periodically as in the conventional scheme. The problem is formulated as a combinatorial optimization problem, for which a Semidefinite Relaxation-based (SDR-based) solving approach is proposed. Numerical results demonstrate that our scheme outperforms significantly the conventional beam sweeping.
2017 International Symposium on Wireless Communication Systems (ISWCS), 2017
We provide a comparison between overlay Device-to-Device (D2D) and cellular communications in TDD... more We provide a comparison between overlay Device-to-Device (D2D) and cellular communications in TDD (Time Division Duplex) wireless networks using queuing theory. For that, we provide a theoretical analysis of the queuing stability region of two wireless network models: the first one is a pure cellular network where any two users (UEs) can communicate with each other only through the Base Station (BS) and the second one is a hybrid network where D2D communications are overlaid with cellular communications. The communications that pass through the BS involve a coupling between the queues of the network due to the relaying functionality at the BS level. Hence, applying a queuing theory approach allows us to capture this coupling. In this paper, we investigate the stability region for both scenarios and we derive new insights on the cases where overlay D2D outperforms cellular communications. Furthermore, numerical results are presented to corroborate our claims and demonstrate the gains that overlay D2D can bring to cellular networks.
2018 IEEE Conference on Decision and Control (CDC), 2018
This paper addresses a distributed optimization problem in a large communication network, where n... more This paper addresses a distributed optimization problem in a large communication network, where nodes are active sporadically. Each active node should properly control its action to maximize the global performance of the network, which is characterized by a pre-defined utility function. We consider a challenging situation where the optimization algorithm has to be performed only based on a scalar approximation of the utility function, rather than its closed-form expression, so that the typical gradient descent method cannot be applied. This setting is quite realistic when the network is affected by some stochastic and time-varying process, and that each node cannot have the full knowledge of the network states. We propose a distributed optimization algorithm and proves its almost surely convergence to the optimum. Numerical results are also presented to justify our claim.
2011 IEEE Global Telecommunications Conference - GLOBECOM 2011, 2011
AbstractIn this paper, we study a weighted-sum rate maxi-mization problem in SC-FDMA which is ad... more AbstractIn this paper, we study a weighted-sum rate maxi-mization problem in SC-FDMA which is adopted as the multiple access scheme for the uplink in the 3GPP-LTE standard. Unlike OFDMA, in addition to the restriction of allocating a sub-channel to one user at ...
Proceedings of the 21st ACM International Conference on Modeling, Analysis and Simulation of Wireless and Mobile Systems
Device-to-device (D2D) communications is a promising technique for improving the efficiency of 5G... more Device-to-device (D2D) communications is a promising technique for improving the efficiency of 5G networks. Employing channel adaptive resource allocation can yield to a large enhancement in almost any performance metric of D2D communications (e.g. Energy Efficiency). Centralized approaches require the knowledge of D2D links' Channel State Information (CSI) at the BS level. However, CSI reporting suffers from the limited number of resources available for feedback transmission. Alternately, we propose a distributed algorithm for resource allocation that benefits from the users' knowledge of their local CSI in order to minimize the users' transmission power while maintaining predefined throughput constraint. The key idea is that users compute their local performance metrics (e.g. energy efficiency) and then use a new signaling mechanism to share these values between each other. Under some condition, the performance of this distributed algorithm achieves that of theideal scheduling (i.e. with a global CSI knowledge of all the D2D links). We describe how this technique can be simply implemented by adapting existing CSI reporting (e.g. in Long-Term Evolution (LTE) systems). Furthermore, numerical results are presented to corroborate our claims and demonstrate the gain that the proposed distributed scheduling brings to cellular networks compared to the bestcentralized-limited feedback scheduling.
IEEE Transactions on Wireless Communications, 2021
This paper considers the problem of fully distributed channel allocation in clustered wireless ne... more This paper considers the problem of fully distributed channel allocation in clustered wireless networks when the propagation medium is random. We extend here the existing Trial and Error (TE) framework developed in the deterministic case and for which strong convergence properties hold. We prove that using directly this solution in the random context leads to unsatisfactory solutions. Then we propose an adaptation of the original Trial and Error Learning (TEL) algorithm, called Robust TEL (RTEL), assuming that the random channel effects translate into a bounded stochastic disturbance of the utility function. The solution consists in introducing thresholds in the transitions of the TEL’s Finite State Controller (FSC). We prove that this new solution restores the good convergence property inherited from the TEL. Furthermore, we provide analysis of the stochastic utilities in the Rayleigh fading case in order to check the bounded assumption. Finally, we develop an online algorithm that dynamically estimates the optimal threshold values to adapt to the instantaneous disturbance. Numerical results corroborate our theoretical claims.
2021 IEEE Wireless Communications and Networking Conference (WCNC), 2021
Reconfigurable intelligent surfaces (RIS) technology, as the name implies, is a grid of many smal... more Reconfigurable intelligent surfaces (RIS) technology, as the name implies, is a grid of many small intelligent surfaces that can be reconfigured. It is a new and promising concept in wireless communications, expected to help realize the requirements of the future cellular generations. Numerous studies have been done to prove its added advantages and to control these surfaces in beneficial ways. However, these control schemes come with difficulties related to efficient and practical implementation. In this paper, we propose to control multiple RISs in a multi-user scheme with an algorithm that leads to a simple implementation. We formulate a stochastic optimization problem and we propose a new method using a distributed stochastic algorithm that allows the optimization to be done locally at each RIS with low computational requirements and without the need for instantaneous channel knowledge at the RIS. Also, the signaling between the base station (BS) and each RIS is limited to the exchange of a scalar only. Simulation results prove the success and efficiency of this algorithm.
2021 IEEE Wireless Communications and Networking Conference (WCNC), 2021
The initial access in 5G New Radio (NR) standalone millimeter wave (mmWave) uses the techniques o... more The initial access in 5G New Radio (NR) standalone millimeter wave (mmWave) uses the techniques of beam sweeping to Figure out appropriate directions of transmission and reception. Beam sweeping refers to the transmission of cell specific signals by the base station (BS) while switching beam direction in a sequential manner in order to cover the whole cell. The conventional beam sweeping consists of transmitting sequentially and periodically the beams, according to a fixed pattern, which results in an initial access latency. The aim of this paper is to minimize the overall number of timeslots needed to connect all users to the BS by allowing using multiple beams in some slots and then activating the beams in a prioritized and controlled manner rather than sequentially and periodically as in the conventional scheme. The problem is formulated as a combinatorial optimization problem, for which a Semidefinite Relaxation-based (SDR-based) solving approach is proposed. Numerical results demonstrate that our scheme outperforms significantly the conventional beam sweeping.
2017 International Symposium on Wireless Communication Systems (ISWCS), 2017
We provide a comparison between overlay Device-to-Device (D2D) and cellular communications in TDD... more We provide a comparison between overlay Device-to-Device (D2D) and cellular communications in TDD (Time Division Duplex) wireless networks using queuing theory. For that, we provide a theoretical analysis of the queuing stability region of two wireless network models: the first one is a pure cellular network where any two users (UEs) can communicate with each other only through the Base Station (BS) and the second one is a hybrid network where D2D communications are overlaid with cellular communications. The communications that pass through the BS involve a coupling between the queues of the network due to the relaying functionality at the BS level. Hence, applying a queuing theory approach allows us to capture this coupling. In this paper, we investigate the stability region for both scenarios and we derive new insights on the cases where overlay D2D outperforms cellular communications. Furthermore, numerical results are presented to corroborate our claims and demonstrate the gains that overlay D2D can bring to cellular networks.
2018 IEEE Conference on Decision and Control (CDC), 2018
This paper addresses a distributed optimization problem in a large communication network, where n... more This paper addresses a distributed optimization problem in a large communication network, where nodes are active sporadically. Each active node should properly control its action to maximize the global performance of the network, which is characterized by a pre-defined utility function. We consider a challenging situation where the optimization algorithm has to be performed only based on a scalar approximation of the utility function, rather than its closed-form expression, so that the typical gradient descent method cannot be applied. This setting is quite realistic when the network is affected by some stochastic and time-varying process, and that each node cannot have the full knowledge of the network states. We propose a distributed optimization algorithm and proves its almost surely convergence to the optimum. Numerical results are also presented to justify our claim.
2011 IEEE Global Telecommunications Conference - GLOBECOM 2011, 2011
AbstractIn this paper, we study a weighted-sum rate maxi-mization problem in SC-FDMA which is ad... more AbstractIn this paper, we study a weighted-sum rate maxi-mization problem in SC-FDMA which is adopted as the multiple access scheme for the uplink in the 3GPP-LTE standard. Unlike OFDMA, in addition to the restriction of allocating a sub-channel to one user at ...
Uploads
Papers by Mohamad Assaad