Delta-orthogonal multiple access (D-OMA) has been recently investigated as a potential technique ... more Delta-orthogonal multiple access (D-OMA) has been recently investigated as a potential technique to enhance the spectral efficiency in 6G networks. D-OMA enables partial overlapping of the adjacent sub-channels that are assigned to different clusters of users served by non-orthogonal multiple access (NOMA), at the expense of additional interference. In this paper, we analyze the performance of D-OMA in the uplink and develop a multi-objective optimization framework to maximize the uplink energy efficiency in a multi-cell network enabled by D-OMA. Specifically, we optimize the subchannel and transmit power allocations of the users as well as the overlapping percentage of the spectrum between the adjacent sub-channels. The formulated problem is a mixed binary non-linear programming problem; therefore, we first transform the problem into a single-objective problem using Tchebyshev method. Then, we apply the monotonic optimization (MO) to explore the hidden monotonicity of the objective...
Underwater wireless optical communications is an emerging solution to the expanding demand for br... more Underwater wireless optical communications is an emerging solution to the expanding demand for broadband links in oceans and seas. In this paper, a cellular underwater wireless optical code division multiple-access (UW-OCDMA) network is proposed to provide broadband links for commercial and military applications. The optical orthogonal codes (OOC) are employed as signature codes of underwater mobile users. Fundamental key aspects of the network such as its backhaul architecture, its potential applications and its design challenges are presented. In particular, the proposed network is used as infrastructure of centralized, decentralized and relay-assisted underwater sensor networks for high-speed real-time monitoring. Furthermore, a promising underwater localization and positioning scheme based on this cellular network is presented. Finally, probable design challenges such as cell edge coverage, blockage avoidance, power control and increasing the network capacity are addressed.
2021 IEEE Global Communications Conference (GLOBECOM), 2021
Future heterogeneous wireless networks (HetNets) should provide massive connectivity for a large ... more Future heterogeneous wireless networks (HetNets) should provide massive connectivity for a large number of devices. In such networks, the problem of user association and multiple access management is of paramount importance. This paper formulates a statistical representation of the user association problem using users' probability density function. In other words, this paper is a bridge between the dynamic mixed-integer formulation of the user association used in relaxation, game theory, and reinforcement learning approaches and the static user association considered in analytical stochastic geometry methods. To this aim, a novel representation independent of the number of users is derived from the combinatorial user association formulation. Interestingly, we show that for fair user association, the statistical representation is a multi-objective optimization. The first objective is to maximize the network throughput with fairness consideration, and the second objective is to optimize the load balancing in terms of the Shannon entropy. Based on this representation, we introduce an algorithm to optimize user association using the first-order derivative formula. We propose a method that can optimize individual base stations' bias factors inside each tier of a HetNet. Numerical results show that the statistical representation closely tracks the stochastic behavior of the dynamic association. The proposed optimization approach improves the 10% outage rate of a two-tier network by 19% and enhances the load balancing by reducing the load of macro base stations by 22%.
Recently, multi-band elastic optical networks (MB-EONs) have been introduced to increase the tran... more Recently, multi-band elastic optical networks (MB-EONs) have been introduced to increase the transmission capacity of optical networks by expanding the transmission frequency range beyond the conventional C-band (e.g., O-, E-, S-, and L-band). Thus, by utilizing the idle frequency bands of the existing standard single mode fibers (SMFs), the capacity improvement in MB-EONs is achieved with lower capital expenditure compared to other techniques, such as space division multiplexing (SDM) in multi-core fibers (MCFs). The routing, modulation level and spectrum assignment (RMLSA) problem in MB-EONs is more challenging than that of the conventional single band EONs, and the inter-channel stimulated Raman scattering (ISRS) process should be considered in signal-to-noise ratio (SNR) analysis. In this article, ISRS-aware RMLSA problem in MB-EONs is studied. We obtain the optimal solution of this problem by formulating a path-based integer linear programming (ILP) model. Since the number of slots and demands are too large in a multi-band system, the ILP problem is too complex to be solved in polynomial time. Therefore, we propose heuristic algorithms to solve the ISRS-aware RMLSA problem. Then, performance of the proposed schemes is evaluated through exhaustive simulations. The results reveal that among all the proposed heuristic algorithms, the algorithm named as enhanced in-process estimation (EIPE) has the best performance in saving more frequency slots for future demands, while achieving higher spectral efficiency and SNR estimation accuracy. Moreover, for a special case of small-scale scenario, the performance of EIPE is close to the results of ILP formulation. Finally, our results indicate that by ignoring ISRS process in the SNR estimation, outage occurs for some of lightpaths, where the outage percentage depends on the launch power.
In this paper, we propose to use the discretized version of the so-called Enhanced Gaussian Noise... more In this paper, we propose to use the discretized version of the so-called Enhanced Gaussian Noise (EGN) model to estimate the non-linearity effects of fiber on the performance of optical coherent and uncompensated transmission (CUT) systems. By computing the power of non-linear interference noise and considering optical amplifier noise, we obtain the signal-to-noise (SNR) ratio and achievable rate of CUT. To allocate the power of each CUT channel, we consider two optimization problems with the objectives of maximizing minimum SNR margin and achievable rate. We show that by using the discretized EGN model, the complexity of the introduced optimization problems is reduced compared with the existing optimization problems developed based on the so-called discretized Gaussian Noise (GN) model. In addition, the optimization based on the discretized EGN model leads to a better SNR and achievable rate. We validate our analytical results with simulations and experimental results. We simulate...
2018 Fifth International Conference on Millimeter-Wave and Terahertz Technologies (MMWaTT), 2018
In this paper, we compare the nonlinearity effects of single mode fiber (SMF) and non-zero disper... more In this paper, we compare the nonlinearity effects of single mode fiber (SMF) and non-zero dispersion shifted fiber (NZ-DSF) on the performance of optical coherent transmission systems. We estimate the nonlinearity effects of fiber, referred to as nonlinear interference noise (NLIN), by using the so-called enhanced Gaussian noise (EGN) model, and compute signal to noise ration (SNR) of optical coherent transmission system by considering NLIN and optical amplifier noise, referred to as amplified spontaneous emission (ASE) noise. By considering EGN model we optimize the lunch power of optical coherent systems considering SMF and NZ-DSF. Finally, a 100Gbps optical coherent transmission system is simulated and its results are compared with analytical results obtained based on the EGN model. The closeness between analytical and simulation results reveal the accuracy of the EGN model and the power optimization formulations.
2017 IEEE International Conference on Communications (ICC), 2017
In this paper, we investigate multi-quality of service (QoS) routing and spectrum assignment in e... more In this paper, we investigate multi-quality of service (QoS) routing and spectrum assignment in elastic optical networks (EONs) by utilizing network state information in terms of bandwidth usage and holding time of established connections. Toward this aim, two types of traffic, namely big data traffic (BDT) requests, and fixed rate flow requests (FLRs) are considered, where BDTs can tolerate a pre-determined initial delay while FLRs must be served immediately without any delay. We assume that both frequency and time usage of optical bandwidth is slotted, and accordingly optical resources are defined in a two-dimensional (2D) time/frequency domain, where the smallest resource is specified with its time and frequency slot number. Furthermore, we define two controlling coefficients determining the ratio of time and spectrum slots which can be assigned to BDTs. By selecting various values for these coefficients, network manager will be able to support different class of services and cha...
The emerging cell-free massive multiple-input multiple-output (CF-mMIMO) is a promising scheme to... more The emerging cell-free massive multiple-input multiple-output (CF-mMIMO) is a promising scheme to tackle the capacity crunch in wireless networks. Designing the optimal fronthaul network in the CF-mMIMIO is of utmost importance to deploy a cost- and energy-efficient network. In this paper, we present a framework to optimally design the fronthaul network of CF-mMIMO utilizing optical fiber and free space optical (FSO) technologies. We study an uplink data transmission of the CF-mMIMO network wherein each of the distributed access points (APs) is connected to a central processing unit (CPU) through a capacity-limited fronthaul, which could be the optical fiber or FSO. Herein, we have derived achievable rates and studied the network's energy efficiency in the presence of power consumption models at the APs and fronthaul links. Although an optical fiber link has a larger capacity, it consumes less power and has a higher deployment cost than that of an FSO link. For a given total num...
2019 2nd West Asian Colloquium on Optical Wireless Communications (WACOWC), 2019
In this paper, we propose a new architecture to leverage visible light communication (VLC)and ste... more In this paper, we propose a new architecture to leverage visible light communication (VLC)and steerable infrared (IR)beam to enhance the wireless data transmission rate of indoor users in the so-called fiber-wireless (FiWi)access networks. In the proposed architecture, VLC access points (APs), referred to as light fidelity (LiFi)APs, besides WiFi APs are converged with fifth-generation (5G)cellular networks to provide ultra-reliable and low latency communication (URLLC). In the proposed architecture, steerable IR beams are utilized as backhaul links of LiFi APs, as well as multi-beam VLC link are implemented by using the on chip optical phased array. In this paper, we highlight potentials and benefits of this architecture and outline future research directions to address the challenges.
Cell-free massive MIMO (CF-mMIMO) network and its variations such the user-centric (UC) one are c... more Cell-free massive MIMO (CF-mMIMO) network and its variations such the user-centric (UC) one are considered as promising techniques for the forthcoming wireless networks. Also, investigating effects of fronthaul and backhaul links connecting access points (APs) to central processing unit (CPU) is of interest to make it more practical. Thus, we study uplink of CF- and UC-mMIMO networks wherein free space optical fronthauls connect APs to serving aggregation nodes (ANs), and the ANs are connected to the CPU by fiber optic backhauls. To derive the achievable rates, we firstly obtain channel state information by use of uplink pilot transmissions, and then data recovery is performed at the CPU. Moreover, it is assumed that devices at APs and ANs are not ideal and distort the received information/pilot signals. For the CF- and UC-mMIMO setups, optimal transmission power allocations at the users, and optical gain coefficients at the APs and ANs are derived to maximize the achievable sum rat...
5G mobile networks will have to deal simultaneously with three types of traffic: mobile broadband... more 5G mobile networks will have to deal simultaneously with three types of traffic: mobile broadband communications, critical communications and Internet of Things (IoT). In this paper, we propose a novel hybrid 5G Fiber-Wireless (FiWi) access architecture equipped with Mobile Edge Computing-enabled (MEC) macro base stations and investigate its performance. Given the proposed architecture, we aim to solve the user association problem under differentiated Quality of Service (QoS). Indeed, we aim at maximizing the number of the users that are served by the network within their latency constraints, having IoT and haptic applications' requirements in mind. Our approach to solve the user association problem is based on Genetic Algorithms (GA).
IEEE Journal on Selected Areas in Communications, 2021
Elastic Optical Network (EON) is a promising solution to address the high capacity, low latency, ... more Elastic Optical Network (EON) is a promising solution to address the high capacity, low latency, and flexibility requirements of the upcoming 5th-generation (5G) networks. Furthermore, Multi-Core Fibers (MCFs) and Space Division Multiplexing (SDM) technique can be utilized to overcome the capacity limitation of the conventional Single Mode Fibers (SMFs). On the other hand, Quantum Key Distribution (QKD) is an effective solution to address the security issues in 5G transport networks. In this paper, we investigate the performance of QKD over elastic optical networks with multi-core fibers and address the resource allocation problem for quantum and classical channels of QKD (QChs and CChs) and conventional data channels (DChs). To do so, we calculate the background noise caused by different noise sources and accordingly calculate the Secret Key Rate (SKR) in quantum channels. Then, we propose an Integer Linear Programming formulation and a heuristic algorithm to allocate network resources (spectrum, core, and links) to QChs, CChs, and DChs, with the objective of maximizing the secret key rate and minimizing the number of utilized frequency slots (FSs). Finally, we evaluate the proposed ILP and heuristic algorithm in terms of SKR and the number of utilized FSs. In our simulations, we consider core and metro topologies, fixed and distance adaptive launch power for classical signals, different fiber specifications, and different assumptions regarding the relative locations of quantum and classical channels in a multi-core fiber.
2021 IEEE 32nd Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), 2021
In this paper, a novel method is proposed to study the tradeoff between energy efficiency (EE) of... more In this paper, a novel method is proposed to study the tradeoff between energy efficiency (EE) of small-cell users and unmanned aerial vehicles (UAV) users in multi-cell orthogonal frequency division multiple access (OFDMA)-based networks. Contrary to the prior works that only maximize the EE of the UAV network subject to some constraints on transmit power of UAV users, we formulate a multi-objective optimization problem (MOOP) that jointly maximize the EE of small-cell and UAV users while guaranteeing the minimum rate for UAV users as well as maximum transmit powers for the corresponding small-cell and UAV BSs. The proposed MOOP is transformed into a single optimization problem (SOOP) by the weighted Tchebycheff approach. Then, an iterative technique is used to optimize alternatively subchannels and transmission powers of small-cell and UAV networks at each step. Numerical results show that a substantial performance gain can be obtained over the existing solutions.
2018 9th International Symposium on Telecommunications (IST), 2018
The transmission capacity of traditional single core fibers is reaching its upper bound. Space-di... more The transmission capacity of traditional single core fibers is reaching its upper bound. Space-division multiplexing (SDM) leveraging multi-core fibers is considered to be a promising solution for this problem. Elastic optical networks (EONs) with Multi-core fibers (MCF) are a kind of SDM-enabled EONs (SDM-EON) providing larger transmission capacity. However, the resource assignment in these networks becomes more complex due to inter-core crosstalk. Another important issue to be considered in future networks is the time domain behavior of incoming traffic which means considering Advance Reservation (AR) requests, in addition to regular Immediate Reservation (IR) requests. In this paper, the problem of routing, modulation level, core and spectrum assignment and scheduling is addressed in an SDM-EON with AR/IR traffic, in which inter-core crosstalk is modeled. This problem is formulated as a Mixed Integer Linear Programming (MILP) and a heuristic algorithm is proposed to solve it.
2019 2nd West Asian Colloquium on Optical Wireless Communications (WACOWC), 2019
As a promising solution for future indoor access networks, resource allocation in Visible light c... more As a promising solution for future indoor access networks, resource allocation in Visible light communication or LiFi networks is subject to lots of researches. An interesting approach for network algorithm design is to use some knowledge about the future of the network. With this regards, the anticipatory design may improve the performance of the system in terms of delay and throughput. This paper reviews the state-of-the-art anticipatory algorithms proposed in the literature, given different prediction capabilities. The key element that all of these algorithms share is to find an event that correlates the current actions to the performance of the network in the future. Apart from the amount of possible prediction, two main approaches have been proposed for problem formulation. The optimal anticipatory resource allocation problem can be formulated in terms of a T-step look-ahead optimization problem. This approach requires more accurate information about the future of the network and yields higher performance improvements. The objective function can be adjusted to achieve high fairness and throughput or low latency in the system. On the other hand, the resource allocation algorithm can be expressed as a matching problem on a bipartite graph. The partial knowledge of the future can be added to the problem using proper heuristic preference functions.
Delta-orthogonal multiple access (D-OMA) has been recently investigated as a potential technique ... more Delta-orthogonal multiple access (D-OMA) has been recently investigated as a potential technique to enhance the spectral efficiency in 6G networks. D-OMA enables partial overlapping of the adjacent sub-channels that are assigned to different clusters of users served by non-orthogonal multiple access (NOMA), at the expense of additional interference. In this paper, we analyze the performance of D-OMA in the uplink and develop a multi-objective optimization framework to maximize the uplink energy efficiency in a multi-cell network enabled by D-OMA. Specifically, we optimize the subchannel and transmit power allocations of the users as well as the overlapping percentage of the spectrum between the adjacent sub-channels. The formulated problem is a mixed binary non-linear programming problem; therefore, we first transform the problem into a single-objective problem using Tchebyshev method. Then, we apply the monotonic optimization (MO) to explore the hidden monotonicity of the objective...
Underwater wireless optical communications is an emerging solution to the expanding demand for br... more Underwater wireless optical communications is an emerging solution to the expanding demand for broadband links in oceans and seas. In this paper, a cellular underwater wireless optical code division multiple-access (UW-OCDMA) network is proposed to provide broadband links for commercial and military applications. The optical orthogonal codes (OOC) are employed as signature codes of underwater mobile users. Fundamental key aspects of the network such as its backhaul architecture, its potential applications and its design challenges are presented. In particular, the proposed network is used as infrastructure of centralized, decentralized and relay-assisted underwater sensor networks for high-speed real-time monitoring. Furthermore, a promising underwater localization and positioning scheme based on this cellular network is presented. Finally, probable design challenges such as cell edge coverage, blockage avoidance, power control and increasing the network capacity are addressed.
2021 IEEE Global Communications Conference (GLOBECOM), 2021
Future heterogeneous wireless networks (HetNets) should provide massive connectivity for a large ... more Future heterogeneous wireless networks (HetNets) should provide massive connectivity for a large number of devices. In such networks, the problem of user association and multiple access management is of paramount importance. This paper formulates a statistical representation of the user association problem using users' probability density function. In other words, this paper is a bridge between the dynamic mixed-integer formulation of the user association used in relaxation, game theory, and reinforcement learning approaches and the static user association considered in analytical stochastic geometry methods. To this aim, a novel representation independent of the number of users is derived from the combinatorial user association formulation. Interestingly, we show that for fair user association, the statistical representation is a multi-objective optimization. The first objective is to maximize the network throughput with fairness consideration, and the second objective is to optimize the load balancing in terms of the Shannon entropy. Based on this representation, we introduce an algorithm to optimize user association using the first-order derivative formula. We propose a method that can optimize individual base stations' bias factors inside each tier of a HetNet. Numerical results show that the statistical representation closely tracks the stochastic behavior of the dynamic association. The proposed optimization approach improves the 10% outage rate of a two-tier network by 19% and enhances the load balancing by reducing the load of macro base stations by 22%.
Recently, multi-band elastic optical networks (MB-EONs) have been introduced to increase the tran... more Recently, multi-band elastic optical networks (MB-EONs) have been introduced to increase the transmission capacity of optical networks by expanding the transmission frequency range beyond the conventional C-band (e.g., O-, E-, S-, and L-band). Thus, by utilizing the idle frequency bands of the existing standard single mode fibers (SMFs), the capacity improvement in MB-EONs is achieved with lower capital expenditure compared to other techniques, such as space division multiplexing (SDM) in multi-core fibers (MCFs). The routing, modulation level and spectrum assignment (RMLSA) problem in MB-EONs is more challenging than that of the conventional single band EONs, and the inter-channel stimulated Raman scattering (ISRS) process should be considered in signal-to-noise ratio (SNR) analysis. In this article, ISRS-aware RMLSA problem in MB-EONs is studied. We obtain the optimal solution of this problem by formulating a path-based integer linear programming (ILP) model. Since the number of slots and demands are too large in a multi-band system, the ILP problem is too complex to be solved in polynomial time. Therefore, we propose heuristic algorithms to solve the ISRS-aware RMLSA problem. Then, performance of the proposed schemes is evaluated through exhaustive simulations. The results reveal that among all the proposed heuristic algorithms, the algorithm named as enhanced in-process estimation (EIPE) has the best performance in saving more frequency slots for future demands, while achieving higher spectral efficiency and SNR estimation accuracy. Moreover, for a special case of small-scale scenario, the performance of EIPE is close to the results of ILP formulation. Finally, our results indicate that by ignoring ISRS process in the SNR estimation, outage occurs for some of lightpaths, where the outage percentage depends on the launch power.
In this paper, we propose to use the discretized version of the so-called Enhanced Gaussian Noise... more In this paper, we propose to use the discretized version of the so-called Enhanced Gaussian Noise (EGN) model to estimate the non-linearity effects of fiber on the performance of optical coherent and uncompensated transmission (CUT) systems. By computing the power of non-linear interference noise and considering optical amplifier noise, we obtain the signal-to-noise (SNR) ratio and achievable rate of CUT. To allocate the power of each CUT channel, we consider two optimization problems with the objectives of maximizing minimum SNR margin and achievable rate. We show that by using the discretized EGN model, the complexity of the introduced optimization problems is reduced compared with the existing optimization problems developed based on the so-called discretized Gaussian Noise (GN) model. In addition, the optimization based on the discretized EGN model leads to a better SNR and achievable rate. We validate our analytical results with simulations and experimental results. We simulate...
2018 Fifth International Conference on Millimeter-Wave and Terahertz Technologies (MMWaTT), 2018
In this paper, we compare the nonlinearity effects of single mode fiber (SMF) and non-zero disper... more In this paper, we compare the nonlinearity effects of single mode fiber (SMF) and non-zero dispersion shifted fiber (NZ-DSF) on the performance of optical coherent transmission systems. We estimate the nonlinearity effects of fiber, referred to as nonlinear interference noise (NLIN), by using the so-called enhanced Gaussian noise (EGN) model, and compute signal to noise ration (SNR) of optical coherent transmission system by considering NLIN and optical amplifier noise, referred to as amplified spontaneous emission (ASE) noise. By considering EGN model we optimize the lunch power of optical coherent systems considering SMF and NZ-DSF. Finally, a 100Gbps optical coherent transmission system is simulated and its results are compared with analytical results obtained based on the EGN model. The closeness between analytical and simulation results reveal the accuracy of the EGN model and the power optimization formulations.
2017 IEEE International Conference on Communications (ICC), 2017
In this paper, we investigate multi-quality of service (QoS) routing and spectrum assignment in e... more In this paper, we investigate multi-quality of service (QoS) routing and spectrum assignment in elastic optical networks (EONs) by utilizing network state information in terms of bandwidth usage and holding time of established connections. Toward this aim, two types of traffic, namely big data traffic (BDT) requests, and fixed rate flow requests (FLRs) are considered, where BDTs can tolerate a pre-determined initial delay while FLRs must be served immediately without any delay. We assume that both frequency and time usage of optical bandwidth is slotted, and accordingly optical resources are defined in a two-dimensional (2D) time/frequency domain, where the smallest resource is specified with its time and frequency slot number. Furthermore, we define two controlling coefficients determining the ratio of time and spectrum slots which can be assigned to BDTs. By selecting various values for these coefficients, network manager will be able to support different class of services and cha...
The emerging cell-free massive multiple-input multiple-output (CF-mMIMO) is a promising scheme to... more The emerging cell-free massive multiple-input multiple-output (CF-mMIMO) is a promising scheme to tackle the capacity crunch in wireless networks. Designing the optimal fronthaul network in the CF-mMIMIO is of utmost importance to deploy a cost- and energy-efficient network. In this paper, we present a framework to optimally design the fronthaul network of CF-mMIMO utilizing optical fiber and free space optical (FSO) technologies. We study an uplink data transmission of the CF-mMIMO network wherein each of the distributed access points (APs) is connected to a central processing unit (CPU) through a capacity-limited fronthaul, which could be the optical fiber or FSO. Herein, we have derived achievable rates and studied the network's energy efficiency in the presence of power consumption models at the APs and fronthaul links. Although an optical fiber link has a larger capacity, it consumes less power and has a higher deployment cost than that of an FSO link. For a given total num...
2019 2nd West Asian Colloquium on Optical Wireless Communications (WACOWC), 2019
In this paper, we propose a new architecture to leverage visible light communication (VLC)and ste... more In this paper, we propose a new architecture to leverage visible light communication (VLC)and steerable infrared (IR)beam to enhance the wireless data transmission rate of indoor users in the so-called fiber-wireless (FiWi)access networks. In the proposed architecture, VLC access points (APs), referred to as light fidelity (LiFi)APs, besides WiFi APs are converged with fifth-generation (5G)cellular networks to provide ultra-reliable and low latency communication (URLLC). In the proposed architecture, steerable IR beams are utilized as backhaul links of LiFi APs, as well as multi-beam VLC link are implemented by using the on chip optical phased array. In this paper, we highlight potentials and benefits of this architecture and outline future research directions to address the challenges.
Cell-free massive MIMO (CF-mMIMO) network and its variations such the user-centric (UC) one are c... more Cell-free massive MIMO (CF-mMIMO) network and its variations such the user-centric (UC) one are considered as promising techniques for the forthcoming wireless networks. Also, investigating effects of fronthaul and backhaul links connecting access points (APs) to central processing unit (CPU) is of interest to make it more practical. Thus, we study uplink of CF- and UC-mMIMO networks wherein free space optical fronthauls connect APs to serving aggregation nodes (ANs), and the ANs are connected to the CPU by fiber optic backhauls. To derive the achievable rates, we firstly obtain channel state information by use of uplink pilot transmissions, and then data recovery is performed at the CPU. Moreover, it is assumed that devices at APs and ANs are not ideal and distort the received information/pilot signals. For the CF- and UC-mMIMO setups, optimal transmission power allocations at the users, and optical gain coefficients at the APs and ANs are derived to maximize the achievable sum rat...
5G mobile networks will have to deal simultaneously with three types of traffic: mobile broadband... more 5G mobile networks will have to deal simultaneously with three types of traffic: mobile broadband communications, critical communications and Internet of Things (IoT). In this paper, we propose a novel hybrid 5G Fiber-Wireless (FiWi) access architecture equipped with Mobile Edge Computing-enabled (MEC) macro base stations and investigate its performance. Given the proposed architecture, we aim to solve the user association problem under differentiated Quality of Service (QoS). Indeed, we aim at maximizing the number of the users that are served by the network within their latency constraints, having IoT and haptic applications' requirements in mind. Our approach to solve the user association problem is based on Genetic Algorithms (GA).
IEEE Journal on Selected Areas in Communications, 2021
Elastic Optical Network (EON) is a promising solution to address the high capacity, low latency, ... more Elastic Optical Network (EON) is a promising solution to address the high capacity, low latency, and flexibility requirements of the upcoming 5th-generation (5G) networks. Furthermore, Multi-Core Fibers (MCFs) and Space Division Multiplexing (SDM) technique can be utilized to overcome the capacity limitation of the conventional Single Mode Fibers (SMFs). On the other hand, Quantum Key Distribution (QKD) is an effective solution to address the security issues in 5G transport networks. In this paper, we investigate the performance of QKD over elastic optical networks with multi-core fibers and address the resource allocation problem for quantum and classical channels of QKD (QChs and CChs) and conventional data channels (DChs). To do so, we calculate the background noise caused by different noise sources and accordingly calculate the Secret Key Rate (SKR) in quantum channels. Then, we propose an Integer Linear Programming formulation and a heuristic algorithm to allocate network resources (spectrum, core, and links) to QChs, CChs, and DChs, with the objective of maximizing the secret key rate and minimizing the number of utilized frequency slots (FSs). Finally, we evaluate the proposed ILP and heuristic algorithm in terms of SKR and the number of utilized FSs. In our simulations, we consider core and metro topologies, fixed and distance adaptive launch power for classical signals, different fiber specifications, and different assumptions regarding the relative locations of quantum and classical channels in a multi-core fiber.
2021 IEEE 32nd Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), 2021
In this paper, a novel method is proposed to study the tradeoff between energy efficiency (EE) of... more In this paper, a novel method is proposed to study the tradeoff between energy efficiency (EE) of small-cell users and unmanned aerial vehicles (UAV) users in multi-cell orthogonal frequency division multiple access (OFDMA)-based networks. Contrary to the prior works that only maximize the EE of the UAV network subject to some constraints on transmit power of UAV users, we formulate a multi-objective optimization problem (MOOP) that jointly maximize the EE of small-cell and UAV users while guaranteeing the minimum rate for UAV users as well as maximum transmit powers for the corresponding small-cell and UAV BSs. The proposed MOOP is transformed into a single optimization problem (SOOP) by the weighted Tchebycheff approach. Then, an iterative technique is used to optimize alternatively subchannels and transmission powers of small-cell and UAV networks at each step. Numerical results show that a substantial performance gain can be obtained over the existing solutions.
2018 9th International Symposium on Telecommunications (IST), 2018
The transmission capacity of traditional single core fibers is reaching its upper bound. Space-di... more The transmission capacity of traditional single core fibers is reaching its upper bound. Space-division multiplexing (SDM) leveraging multi-core fibers is considered to be a promising solution for this problem. Elastic optical networks (EONs) with Multi-core fibers (MCF) are a kind of SDM-enabled EONs (SDM-EON) providing larger transmission capacity. However, the resource assignment in these networks becomes more complex due to inter-core crosstalk. Another important issue to be considered in future networks is the time domain behavior of incoming traffic which means considering Advance Reservation (AR) requests, in addition to regular Immediate Reservation (IR) requests. In this paper, the problem of routing, modulation level, core and spectrum assignment and scheduling is addressed in an SDM-EON with AR/IR traffic, in which inter-core crosstalk is modeled. This problem is formulated as a Mixed Integer Linear Programming (MILP) and a heuristic algorithm is proposed to solve it.
2019 2nd West Asian Colloquium on Optical Wireless Communications (WACOWC), 2019
As a promising solution for future indoor access networks, resource allocation in Visible light c... more As a promising solution for future indoor access networks, resource allocation in Visible light communication or LiFi networks is subject to lots of researches. An interesting approach for network algorithm design is to use some knowledge about the future of the network. With this regards, the anticipatory design may improve the performance of the system in terms of delay and throughput. This paper reviews the state-of-the-art anticipatory algorithms proposed in the literature, given different prediction capabilities. The key element that all of these algorithms share is to find an event that correlates the current actions to the performance of the network in the future. Apart from the amount of possible prediction, two main approaches have been proposed for problem formulation. The optimal anticipatory resource allocation problem can be formulated in terms of a T-step look-ahead optimization problem. This approach requires more accurate information about the future of the network and yields higher performance improvements. The objective function can be adjusted to achieve high fairness and throughput or low latency in the system. On the other hand, the resource allocation algorithm can be expressed as a matching problem on a bipartite graph. The partial knowledge of the future can be added to the problem using proper heuristic preference functions.
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Papers by Hamzeh Beyranvand