Mehdi Rasti - Academia.edu (original) (raw)

Papers by Mehdi Rasti

IEEE Access

The application of flying base stations (FBS) in wireless communication is becoming a key enabler... more The application of flying base stations (FBS) in wireless communication is becoming a key enabler to improve cellular wireless connectivity. Following this tendency, this research work aims to enhance the spectral efficiency of FBSs using the radio access network (RAN) slicing framework; this optimization considers that FBSs' location was already defined previously. This framework splits the physical radio resources into three RAN slices. These RAN slices schedule resources by optimizing individual slice spectral efficiency by using a deep reinforcement learning approach. The simulation indicates that the proposed framework generally outperforms the spectral efficiency of the network that only considers the heuristic predefined FBS location, although the gains are not always significant in some specific cases. Finally, spectral efficiency is analyzed for each RAN slice resource and evaluated in terms of service-level agreement (SLA) to indicate the performance of the framework.

2019 IEEE Global Communications Conference (GLOBECOM), 2019

The problem of joint power and sub-channel allocation to maximize energy efficiency (EE) and spec... more The problem of joint power and sub-channel allocation to maximize energy efficiency (EE) and spectral efficiency (SE) simultaneously in in-band full-duplex (IBFD) orthogonal frequency-division multiple access (OFDMA) network is addressed considering users' QoS in both uplink and downlink. The resulting optimization problem is a non-convex mixed integer non-linear program (MINLP) which is generally difficult to solve. In order to strike a balance between the EE and SE, we restate this problem as a multi-objective optimization problem (MOOP) which aims at maximizing system's throughput and minimizing system's power consumption, simultaneously. To this end, the ǫconstraint method is adopted to transform the MOOP into single objective optimization problem (SOOP). The underlying problem is solved via an efficient solution based on the majorization minimization (MM) approach. Furthermore, in order to handle binary subchannel allocation variable constraints, a penalty function is introduced. Simulation results unveil interesting tradeoffs between EE and SE. Index Terms-Full-duplex (FD) communication, energyefficiency (EE), spectral-efficiency (SE), mixed integer nonlinear program (MINLP), multi-objective optimization problem (MOOP), ǫ-method, majorization minimization (MM).

2019 International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOPT), 2019

Dual Connectivity (DC) has been proposed by Third Generation Partnership Project (3GPP), in order... more Dual Connectivity (DC) has been proposed by Third Generation Partnership Project (3GPP), in order to address the small coverage areas and outage of users and improve the mobility robustness and rate of users in Heterogeneous Networks (HetNets). In the HetNet with DC, each user is assigned a Macro eNode Base Station (MeNB) and a Small eNode Base Station (SeNB) and transmits data to both eNode Base Stations (eNBs), simultaneously. In this paper, we present a power splitting scheme for the HetNet with DC; to maximize the total rate of the users while not exceeding the maximum transmit power of each user. In our proposed power splitting scheme, a Deep Reinforcement Learning (DRL) approach is taken based on the actor-critic model on continuous state-action spaces. Simulation results demonstrate that our power splitting scheme outperforms the baseline approaches in terms of total rate of users and fairness.

GLOBECOM 2020 - 2020 IEEE Global Communications Conference, 2020

In this paper, we develop a resource allocation framework to optimize the downlink transmission o... more In this paper, we develop a resource allocation framework to optimize the downlink transmission of a backhaulaware multi-cell cognitive radio network (CRN) which is enabled with multi-carrier non-orthogonal multiple access (MC-NOMA). The considered CRN is composed of a single macro base station (MBS) and multiple small BSs (SBSs) that are referred to as the primary and secondary tiers, respectively. For the primary tier, we consider orthogonal frequency division multiple access (OFDMA) scheme and also Quality of Service (QoS) to evaluate the user satisfaction. On the other hand in secondary tier, MC-NOMA is employed and the user satisfaction for web, video and audio as popular multimedia services is evaluated by Quality-of-Experience (QoE). Furthermore, each user in secondary tier can be served simultaneously by multiple SBSs over a subcarrier via Joint Transmission (JT). In particular, we formulate a joint optimization problem of power control and scheduling (i.e., user association and subcarrier allocation) in secondary tier to maximize total achievable QoE for the secondary users. An efficient resource allocation mechanism has been developed to handle the non-linear form interference and to overcome the non-convexity of QoE serving functions. The scheduling and power control policy leverage on Augmented Lagrangian Method (ALM). Simulation results reveal that proposed solution approach can control the interference and JT-NOMA improves total perceived QoE compared to the existing schemes.

2021 IEEE Global Communications Conference (GLOBECOM), 2021

In this paper, we study the problem of minimizing the uplink aggregate transmit power subject to ... more In this paper, we study the problem of minimizing the uplink aggregate transmit power subject to the users' minimum data rate and peak power constraint on each subchannel for multi-cell wireless networks. To address this problem, a distributed sub-optimal joint power and rate control algorithm called JPRC is proposed, which is applicable to both nonorthogonal frequency-division multiple access (NOMA) and orthogonal frequency-division multiple access (OFDMA) schemes. Employing JPRC, each user updates its transmit power using only local information. Simulation results illustrate that the JPRC algorithm can reach a performance close to that obtained by the optimal solution via exhaustive search, with the NOMA scheme achieving a 59% improvement on the aggregate transmit power over the OFDMA counterpart. It is also shown that the JPRC algorithm can outperform existing distributed power control algorithms. Index Terms-Aggregate transmit power, beyond 5G, OFDMA, NOMA, distributed power control algorithm.

2018 IEEE Wireless Communications and Networking Conference (WCNC), 2018

In cellular-D2D networks, users can select the communication mode either direct and form D2D link... more In cellular-D2D networks, users can select the communication mode either direct and form D2D links or indirect and communicate with BS. In former case, users should perform pairing selection and choose their pairs. The main focus in this paper is proposing an analytical framework by using tools from stochastic geometry to address these two issues, i.e. i) mode selection for the user devices to be established in either cellular or D2D mode, which is done based on received power from BS influenced by a bias factor, and ii) investigation of choosing n th-nearest neighbor as the serving node for the receiver of interest, by considering full-duplex (FD) radios as well as halfduplex (HD) in the D2D links. The analytic and simulation results demonstrate that even though the bias factor determines the throughput of each mode, it does not have any influence on the system sum throughput. Furthermore, we demonstrate that despite of suffering from self-interference, FD-D2D results in higher system sum throughput as well as higher coverage probability in comparison to its counterpart, namely purely HD-D2D network.

2017 15th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt), 2017

In this paper, we investigate the joint admission control and resource allocation problem for col... more In this paper, we investigate the joint admission control and resource allocation problem for collaborative computation under fading channels. We develop an Internet-of-Things (IoT) framework in which establishing Device-to-Device (D2D) communications, resource-poor wearable Source Mobile Terminals (SMTs) may offload their computations to resource-rich Processing Mobile Terminals (PMTs), or execute them locally, so as to save energy. Considering the offloading scenario, first, a probabilistic admission control algorithm is proposed for Mobile Terminals (MTs) taking both the deadline and energy harvesting constraints into account. Then, the joint CPU clock frequency/transmit power allocation and collaborative pair selection problem for MTs is addressed mathematically. For local execution scenario, optimal CPU clock frequencies are obtained for SMTs. Finally, based on energy consumption and outage imposed by each scenario, SMTs decide whether to offload their computations or execute them locally. Simulation results demonstrate that the proposed D2Daided Collaborative Mobile Cloud (DCMC) approach attains a near-optimal energy expenditure in a semi-feasible system while effectively mitigating outage ratio of MTs.

IEEE Wireless Communications Letters, 2020

In this paper, we propose a distributed power control algorithm for addressing the global energy ... more In this paper, we propose a distributed power control algorithm for addressing the global energy efficiency (GEE) maximization problem subject to satisfying a minimum target SINR for all user equipments (UEs) in wireless cellular networks. We state the problem as a multi-objective optimization problem which targets minimizing total power consumption and maximizing total throughput, simultaneously, while a minimum target SINR is guaranteed for all UEs. We propose an iterative scheme executed in the UEs to control their transmit power using individual channel state information (CSI) such that the GEE is maximized in a distributed manner. We prove the convergence of the proposed iterative algorithm to its corresponding unique fixed point also shown by our numerical results. Additionally, simulation results demonstrate that our proposed scheme outperforms other algorithms in the literature and performs like the centralized algorithm executed in the base station and maximizes the GEE using the global CSI.

IEEE Transactions on Vehicular Technology, 2019

IEEE Transactions on Communications, 2018

To improve the spectral efficiency in Long-Term Evolution (LTE) systems, the resource blocks (RBs... more To improve the spectral efficiency in Long-Term Evolution (LTE) systems, the resource blocks (RBs) are shared among different cells/base stations (BSs) resulting in interference among the cells/BSs on each RB although all the sub-carriers (SCs) in an RB may not be used in a cell. Defining the load of a given BS per RB as the fraction of the active SCs in that RB, in this paper, we present a generalized signal-to-interferenceand-noise-ratio (SINR) model for downlink users on a given RB. This model considers both the transmit powers of the BSs and the loads of the cells over that RB. Under this load-coupled SINR model, to study the feasibility of a given rate demand vector for users, we formulate an optimization problem of minimizing the total load of the BSs on the RBs. Then, for two different scenarios of feasible and infeasible demand vectors, respectively, we study the load management problem (i.e., minimizing the total load of the BSs on the RBs) and admission control problem (i.e., finding the subset of users with maximum cardinality whose demands can be concurrently satisfied), respectively. Our theoretical investigations, which provide guidelines for designing radio resource management methods for load-coupled OFDMA networks, are complemented through Monte Carlo simulations.

IEEE Transactions on Wireless Communications, 2017

This paper studies two power control problems in energy harvesting wireless networks where one hy... more This paper studies two power control problems in energy harvesting wireless networks where one hybrid base station (HBS) and all user equipments (UEs) are operating in in-band full-duplex mode. We consider minimizing the aggregate power subject to the quality of service requirement constraint, and maximizing the aggregate throughput. We address these two problems by proposing two distributed power control schemes for controlling the uplink transmit power by the UEs and the downlink energy harvesting signal power by the HBS. In our proposed schemes, the HBS updates the downlink transmit power level of the energy-harvesting signal so that each UE is enabled to harvest its required energy for powering the operating circuit and transmitting its uplink information signal with the power level determined by the proposed schemes. We show that our proposed power control schemes converge to their corresponding unique fixed points starting from any arbitrary initial transmit power. We will show that our proposed schemes well address the stated problems, which is also demonstrated by our extensive simulation results. Index Terms-Cellular networks; resource allocation; distributed power control; energy harvesting; in-band full-duplex.

Wireless Networks, 2017

In this paper, we study joint power and subchannel allocation problem for OFDMA based femtocell n... more In this paper, we study joint power and subchannel allocation problem for OFDMA based femtocell networks with focus on uplink direction. We minimize the aggregate power of all Femto user equipments and maximize the total system energy efficiency while satisfying the minimum required rate of all users. An interference limit constraint is considered to protect the QoS of macrocells. The original problem is a mixed-integer non-convex optimization problem which is converted to a convex problem using the time-sharing concept. Three algorithms are proposed to provide a scheme to optimize the goal function while meeting the constraints. The complexity order of all algorithms was investigated and was compared to other alternative solutions. The analytic and simulation results have demonstrated that the proposed algorithms could achieve significant power saving and better energy efficiency compared to existing algorithms.

2016 IEEE Conference on Computer Communications Workshops (INFOCOM WKSHPS), 2016

In this paper, we address the joint channel and power allocation problem for Device-to-Device (D2... more In this paper, we address the joint channel and power allocation problem for Device-to-Device (D2D) communications underlaying uplink cellular networks. We aim to maximize the sum-rate of D2D communications while fulfilling the QoS requirements for both cellular users (CUs) and D2D pairs (DUs). We first propose a heuristic channel assignment algorithm in which a cellular channel is allowed to be shared by multiple DUs and every DU can reuse multiple channels. Given this assigned channels, a price-based Stackelberg game is then formulated to obtain the sub-optimal transmission power for DUs. The simulation results demonstrate that our proposed joint channel and power allocation scheme has a superiority over a few existing resource allocation schemes for D2D communications in terms of D2D sum-rate.

2016 IEEE Symposium on Computers and Communication (ISCC), 2016

Two-tier networks consisting of macrocell and femtocells are provided as a solution to increase c... more Two-tier networks consisting of macrocell and femtocells are provided as a solution to increase capacity and improve indoor coverage of cellular networks. In two-tier networks, when the spectrum is shared by macrocell and all of femtocells, the cross-tier and co-tier interference should be taken into account. In this paper, we investigate the power control problem of minimizing the aggregate transmit power for macro-tier and the joint power control and sub-channel allocation problem of maximizing the total rate for femto-tier, both in uplink transmission, while the cross-tier and co-tier interference are both taken into account. Then, to solve these problems, we propose distributed sub-optimal algorithms for both macro and femto-tier. Finally, simulation results are presented to confirm out performance of our proposed algorithm and to compare with the existing algorithm.

2015 IEEE/CIC International Conference on Communications in China (ICCC), 2015

Device-to-Device (D2D) communication as a promising part of next generation wireless networks imp... more Device-to-Device (D2D) communication as a promising part of next generation wireless networks improves network performance by enabling direct communication between nearby mobile devices. However, as an underlay to cellular network, the resulting co-channel interference degrades the system performance, if available resources are not adequately allocated for D2D pairs. In this paper, we formally state the uplink resource allocation problem of maximizing system sum-rate while taking the signal-to-interference-plus-noise ratio (SINR) constraints into account for each user. A centralized scheme is proposed in which in contrast to existing works a D2D user equipment (DUE) is allowed to reuse resources of more than one cellular user equipment (CUE), and a resource of CUE is allowed to be shared by multiple DUEs. According to this approach, both CUEs and DUEs make probabilistic resource sharing decisions by taking advantage of a concept namely, Adaptive Interference Restricted Region (AIRR). Simulation results show that our proposed approach, exhibits a near-optimal sum-rate, and outperforms existing related schemes.

IEEE Transactions on Wireless Communications, 2016

Next generation cellular networks will consist of multiple tiers of cells and users associated wi... more Next generation cellular networks will consist of multiple tiers of cells and users associated with different network tiers may have different priorities (e.g., macrocell-picocellfemtocell networks with macro tier prioritized over pico tier, which is again prioritized over femto tier). Designing efficient joint power and admission control (JPAC) algorithms for such networks under a co-channel deployment (i.e., underlay) scenario is of significant importance. Feasibility checking of a given target signal-to-noise-plus-interference ratio (SINR) vector is generally the most significant contributor to the complexity of JPAC algorithms in single/multi-tier underlay cellular networks. This is generally accomplished through iterative strategies whose complexity is either unpredictable or of O(M 3), when the wellknown relationship between the SINR vector and the power vector is used, where M is the number of users/links. In this paper, we derive a novel relationship between a given SINR vector and its corresponding uplink/downlink power vector based on which the feasibility checking can be performed with a complexity of O(B 3 + M B), where B is the number of base stations. This is significantly less compared to O(M 3) in many cellular wireless networks since the number of base stations is generally much lower than the number of users/links in such networks. The developed novel relationship between the SINR and power vector not only substantially reduces the complexity of designing JPAC algorithms, but also provides insights into developing efficient but low-complexity power update strategies for prioritized multi-tier cellular networks. We propose two such algorithms and through simulations, we show that our proposed algorithms outperform the existing ones in prioritized cellular networks.

IEEE Journal on Selected Areas in Communications, 2015

Heterogeneous network (HetNet) integrated with multiple radio access technologies (RATs) is a pro... more Heterogeneous network (HetNet) integrated with multiple radio access technologies (RATs) is a promising technique to satisfy the exponentially increasing traffic demand of future cellular systems. In this paper, we investigate energyefficient resource allocation in a multi-RAT HetNet, aiming at maximizing the energy efficiency (EE) for each individual user while guaranteeing the quality-of-service (QoS) requirement. Since the EE cannot be simultaneously maximized for every user, a multiple-objective optimization problem (MOOP) is formulated. To find its Pareto optimal solution, we first introduce the concept of Utopia EE, defined as the maximum achievable EE, for each user. Then, using the weighted Tchebycheff method, a singleobjective optimization problem (SOOP) is formulated, which can achieve Pareto optimal solution of the original MOOP. The SOOP is a generalized fractional programming problem that aims to minimize the maximum of several quasiconvex fractional functions. We further transform the problem into an equivalent but better tractable one, and develop an iterative algorithm to effectively solve it. Numerical results demonstrate that the proposed algorithm yields fast convergence, high system EE, and flexible EE tradeoff.

21st Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, 2010

We propose a scheme for maintaining the requested SIR of each user under uncertainty of system pa... more We propose a scheme for maintaining the requested SIR of each user under uncertainty of system parameters in the power control of interference limited wireless networks. In doing so, we keep the outage probability of users below their predefined threshold with minimal power consumption. To reduce the complexity, we apply the notion of chance constraint robust optimization to the outage probability. This approach preserves the convexity of the problem and maintains its tractability. For solving the reformulated problem, a distributed probabilistic robust power algorithm is developed based on the standard interference function and local convergence, which utilizes infrequent message passing. We derive the conditions for the convergence of our algorithm, and prove the optimality of the equilibrium.

IEEE Signal Processing Letters, 2014

IEEE Transactions on Communications, 2016

In an underlay cognitive radio network (CRN), in order to guarantee that all primary users (PUs) ... more In an underlay cognitive radio network (CRN), in order to guarantee that all primary users (PUs) achieve their target-signal-to-interference-plus-noise ratios (target-SINRs), the interference caused by all secondary users (SUs) to the primary receiving-points should be controlled. To do so, the feasible cognitive interference region (FCIR), i.e., the region for allowable values of interference at all of the primary receiving-points, which guarantee the protection of the PUs, needs to be formally characterized. In the state-of-the-art interference management schemes for underlay CRNs, it is considered that all PUs are protected if the cognitive interference for each primary receiving-point is lower than a maximum threshold, the so called interference temperature limit (ITL) for the corresponding receiving-point. This is assumed to be fixed and independent of ITL values for other primary receiving-points, which corresponds to a boxlike FCIR. In this paper, we characterize the FCIR for uplink transmissions in cellular CRNs and for direct transmissions in ad-hoc CRNs. We show that the FCIR is in fact a polyhedron (i.e., the maximum feasible cognitive interference threshold for each primary receiving-point is not a constant, and it depends on that for the other primary receiving-points). Therefore, in practical interference management algorithms, it is not proper to consider a constant and independent ITL value for each of the primary receiving-points. This finding would significantly affect the design of practical interference management schemes for CRNs. To demonstrate this, based on the characterized FCIR, we propose two power control algorithms to find the maximum number of admitted SUs and the maximum aggregate throughput of the SUs in infeasible and feasible CRNs, respectively. For two distinct objectives, our proposed interference management schemes outperform the existing ones. The numerical results also demonstrate how the assumption of fixed ITL values leads to poor performance measures in CRNs. Index Terms-Cellular and ad-hoc cognitive radio networks, uplink transmission, interference feasible region, power and admission control, SINR violation.