Abdellaziz Walid

A decentralized network selection algorithm for group vertical handover in heterogeneous networks

The traditional vertical handover schemes postulate that vertical handover of each user comes on an individual basis. This enables the users to know previously the decision already made by other users, and then the choice will be made accordingly. However, in the case of a group vertical handover, almost all the VHO decisions - which will certainly choose the best network, will be made at the same time which will lead to system performance degradation or network congestion. In this paper, we propose a totally decentralized algorithm for network selection which based on the Congestion Game to resolve the problem of network congestion in GVHO. Therefore, the proposed algorithm named Fully Decentralized Nash Learning Algorithm with incomplete information is a prediction done by each mobile in the group that helps them to reach the Nash equilibrium. Simulation results validate the algorithm and show its robustness under two scenarios. In the first one, we examine the algorithm with a fixed number of mobiles in group to evaluate the mixed strategy and the average perceived throughput of mobiles in WIMAX and HSDPA on the basis of iteration. In the second one, we examine the algorithm with different number of mobiles in group for testing the average number of iterations needed to reach the Nash equilibrium. We also compare it with the traditional vertical handover algorithm.

Group vertical handoff management in heterogeneous networks

Traditional vertical handover schemes postulate that vertical handovers VHOs of users come on an individual basis. This enables users to know previously the decision already made by other users, and then the choice will be accordingly made. However, in case of group mobility, almost all VHO decisions of all users, in a given group e.g., passengers on board a bus or a train equipped with smart phones or laptops, will be made at the same time. This concept is called group vertical handover GVHO. When all VHO decisions of a large number of users are made at the same time, the system performance may degrade and network congestion may occur. In this paper, we propose two fully decentralized algorithms for network access selection, and that is based on the concept of congestion game to resolve the problem of network congestion in group mobility scenarios. Two learning algorithms, dubbed Sastry Algorithm and Q-Learning Algorithm, are envisioned. Each one of these algorithms helps mobile users in a group to reach the nash equilibrium in a stochastic environment. The nash equilibrium represents a fair and efficient solution according to which each mobile user is connected to a single network and has no intention to change his decision to improve his throughput. This shall help resolve the problem of network congestion caused by GVHO. Simulation results validate the proposed algorithms and show their efficiency in achieving convergence, even at a slower pace. To achieve fast convergence, we also propose a heuristic method inspired from simulated annealing and incorporated in a hybrid learning algorithm to speed up convergence time and maintain efficient solutions. The simulation results also show the adaptability of our hybrid algorithm with decreasing step size-simulated annealing DSS-SA for high mobility group scenario. Copyright

Exploiting multi-homing in hyper dense LTE small-cells deployments

It is expected that in two-tier LTE heterogeneous networks, an extensive deployment of small cell networks (SCNs) will take place in the near future, especially in dense urban zones; hence a hyper density of SCNs randomly distributed within macro cell networks (MCNs) will emerge with many overlapping zones of neighboring SCNs. Therefore, the problems of interferences in co-channel deployment will be more complicated and then the overall throughput of downlink will substantially decrease. In order to mitigate the effect of interferences in a hyper density of SCNs scenarios, a solution based on a fully distributed algorithm for sharing time access to SCNs and multi-homing capabilities of macro cellular users is proposed to improve the overall data rate of downlink and at the same time to satisfy QoS throughput requirements of macro and home cellular users. Our tentative scheme will also reduce the signaling overhead due to the absence of coordination among small base stations (SBSs) and macro base station (MBS). Results validate our solution and show the improvement attained in a hyper density of SCNs within MCNs compared to open, closed and shared time access mechanisms based on single network selection.

A congestion game-based routing algorithm for communicating VANETs

Vehicular Ad Hoc Network (VANET) is considered as a special application of Mobile Ad Hoc Networks (MANETs) in road traffic, which can autonomously organize networks without infrastructure. VANETs enable vehicles on the road to communicate with each other and with road infrastructure using wireless capabilities. In the last few years, extensive research has been performed to extend Internet connectivity to VANETs. Indeed, several routing protocols have been proposed to determine routes between vehicles and gateways. In this paper, we propose a routing algorithm which is based on the Congestion Game to resolve the problem of network congestion in VANET and to provide the optimal Internet access paths. The simulation results show that the proposed routing algorithm has better feasibility and effectiveness for communicating VANETs.

Matching game for green uplink in hyper dense LTE HeTNets

In this paper, we aim to improve the energy efficiency of cellular users located in hyper-dense co-channel deployments of LTE small cell Networks (SCNs), randomly distributed within LTE macro cell networks (MCNs). Avoiding the severe cross-tier interferences at the small base stations (SBSs) levels caused by the uplink transmissions between the macro indoor users (which are inside the SBS coverage area) and the macro base station (MBS), ensuring load balancing, and improving energy efficiency are critical technical challenges in hyper-dense co-channel LTE SCNs deployments. As a solution, we formulate our problem as a matching game, then we propose the deferred acceptance algorithm to compute the optimal stable matching consisting of assigning each macro indoor user to the most suitable SBS and vice versa. Simulation results validate our solution, and show how it can effectively improve the energy efficiency of cellular users in hyper-dense LTE HetNets compared to the default Max-SINR association scheme.

On improving network capacity for downlink and uplink of two-tier LTE-FDD networks

A Long Term Evolution-Frequency Division Duplexing (LTE-FDD) small cell is one of the promising solutions for improving service quality and data rate in both the uplink and downlink of home users. Small cell (e.g., femtocell, picocell, microcell) is short range, low cost and low power base station installed by the indoor consumers. However, the avoidance of interferences is still an issue that needs to be addressed for successful deployment of small base stations (SBS) within existing macro cell networks mainly in co-channel deployment. Moreover, interferences are strongly dependent on the type of access control of small cells. Closed and open access are in conflict interests for macro users and home users in the uplink and downlink. To mitigate this conflict, we propose a fully distributed algorithm based on the shared time access and executed by LTE-FDD small cells, in order to reduce the effect of interferences, improve QoS of users, and maximize the overall capacity of downlink and uplink in two-tier LTE networks when small cells are deployed randomly. Simulation results validate our algorithm and show the improvement attained in offloading macro cell and satisfying QoS requirements of home users compared to the closed and open access mechanisms in both the uplink and downlink.

A tax-inspired mechanism design to achieve QoS in VMIMO systems: Give to receive!

In this paper, we model a Virtual MIMO system using a game-theoretic approach. We are interested in the uplink, considering a non-coopertive game, where each user try to satisfy a quality of service. The uplink of a direct-sequence code division multiple access (DS-CDMA) data network is considered and a non-cooperative game is proposed in which users are allowed to choose their uplink receivers as well as to satisfy their quality of service. The utility function used in this framework is defined so that the throughput used by the user is divided into two components: the throughput received from cellular Network, and throughput received from Virtual MIMO System. In addition, this framework is used to study a constrained Nash equilibrium for the proposed game, and the impact of the interaction among users.

A many-to-many matching game in ultra-dense LTE HetNets

In this work, we focus our study to improving the energy efficiency of mobile cellular users in ultra-dense LTE HetNets. The hyper-dense co-channel deployment of indoor LTE small cell networks (SCNs) within LTE macro cell networks (MCNs) will aggravate the effect of cross-tier interferences caused by the uplink transmissions of macro-indoor users located inside the overlapping zones of small base station (SBS) coverage areas. Hence, degrading the uplink performance at the level of SBSs adopting closed access policy. In order to eliminate the severe cross-tier interferences, each SBS attempts to open the access for macro-indoor users that accept only the SBS with Max-SINR offer. This will lead to network congestion problems in several SCNs. Wherefore, we formulate our problem as a many-to-many matching game. Then, we introduce an algorithm that computes the optimal many-to-many stable matching which consist of assigning each macro-indoor user with multi-homing capabilities to the most suitable set of SBSs and vice versa based on their preference profiles. With regard to the conventional Max-SINR association scheme, our solution can effectively improve the energy efficiency of cellular users. Moreover, it can ensure load balancing in ultra-dense LTE HetNets.

Toward Eco-Friendly Smart Mobile Devices for Smart Cities

It is expected that the incessant use of SBSs by indoor mobile users to achieve high data rate and high energy efficiency for their smart mobile devices will drive ultra dense deployment of SCNs within MCNs, specifically in future smart cities. However, SCN densification has a hard effect on the deterioration of the energy efficiency and QoS throughput of mobile users equipped with smart mobile devices like smartphones, laptops, PDAs, and tablets. This degradation is due to the severe cross-tier interferences occurring in ultra dense co-channel deployments of SCNs within MCNs. The present article intends to study the energy efficiency of mobile users for better battery life management of their smart mobile devices through minimal energy consumption during their uplink transmissions. The proposed solution, based on a fully decentralized algorithm for sharing time access executed by SBSs and multi-homing capabilities of macrocellular users, improves the energy efficiency of mobile users for better battery life, and keeps their QoS throughput requirements. Therefore, it leads to the eco-friendly smart mobile devices required in future smart cities. The results validate our proposed solution and show the improvement achieved compared to the conventional access control mechanisms. Furthermore, our scheme requires no coordination among SBSs and macro base stations, which reduces the huge signaling overhead when using cooperative schemes.

Towards Improving Energy Efficiency of Mobiles in Hyper Dense LTE Small-Cells Deployments

In this paper, we propose a green solution for cellular users located in hyper dense co-channel deployments of LTE small cell networks (SCNs), randomly distributed within LTE macro cell networks (MCNs). Our solution is based on a distributed sharing time access algorithm executed by small base stations (SBSs), and multi-homing capabilities of macro cellular users to improve the energy efficiency of cellular users and to satisfy their QoS throughput requirements. The theoretical analysis is validated by simulations. Our results demonstrate the improved energy efficiency of cellular users compared to the other access control mechanisms.