Ahmad M. El-Hajj

A stable matching game for joint uplink/downlink resource allocation in OFDMA wireless networks

The emergence of resource-demanding wireless services such as mobile gaming or multimedia applications motivates the introduction of advanced paradigms for resource allocation in next-generation OFDMA-based wireless networks. In this context, while existing literature mainly focused on schemes in which the uplink and downlink resources are considered independently, this paper proposes a novel subcarrier allocation approach suitable for services that have coupled uplink/downlink (UL/DL) quality-of-service requirements. We model the proposed joint uplink/downlink subcarrier allocation problem as a two-sided stable matching game and we propose a corresponding novel resource allocation algorithm. Results show that the proposed stable matching algorithm enables an efficient joint uplink/downlink subcarrier allocation and yields notable performance gains, in terms of the average utility per user, relative to classical resource allocation schemes. The results also show that our approach leads to an improved fairness in the subcarrier allocation.

A proactive approach for LTE radio network planning with green considerations

The recent trend towards energy-efficient and environment-aware network operations has mandated the development of novel green network planning paradigms. In this context, while existing work focused on developing reactive energy reduction techniques after complete network deployment, this paper presents a proactive green radio network planning (RNP) algorithm that jointly optimizes base station (BS) locations and generates the BS on/off switching patterns based on the changing traffic conditions. Simulation results demonstrate considerable energy savings through dynamic adaptation of the number of simultaneous active BSs.

On optimized joint uplink/downlink resource allocation in OFDMA networks

The emergence of new wireless technologies paved the way to the introduction of a new class of symmetric services with joint uplink/downlink quality of service requirements. In this paper, we formulate joint uplink/downlink resource allocation in OFDMA networks as an optimization problem with total sum-rate maximization as an objective function. A regularization term is added to the problem formulation to account for the coupling between the uplink and the downlink directions. This additional term controls the resource allocation via the minimization of the per-user difference between the uplink and downlink rates. We solve the formulated problem using dual optimization techniques. Performance results demonstrate the effectiveness of the proposed joint uplink/downlink allocation scheme compared to traditional single-link schemes.

On uplink OFDMA resource allocation with ergodic sum-rate maximization

Uplink ergodic sum-rate maximization in OFDMA systems is considered. The general problem is formulated as a convex optimization problem and a dual solution is presented. The problem formulation is generalized to the case of utility maximization where the utility can be any function of rate. A suboptimal scheduling algorithm with low complexity is proposed and shown to achieve close performance to the optimal solution.

Uplink OFDMA resource allocation with discrete rates: optimal solution and suboptimal implementation

Resource allocation in the uplink of orthogonal frequency-division multiple access systems is investigated. The problem of ergodic utility maximisation with discrete rates is formulated and solved using dual Lagrangian techniques. Suboptimal algorithms based on equal power allocation over the subcarriers are proposed. Results are presented and compared for the continuous and discrete rates scenario, using both the optimal solutions and the suboptimal algorithms. Equal power allocation is shown to approximate well the optimal solution in the continuous rates case, as well as in the discrete rates scenario when the number of modulation and coding schemes increases. Copyright

On Radio network planning for next generation 5G networks: A case study

The continuing growth in demand for better mobile experience, higher data rates and lower latencies is driving the development of the forthcoming generation of wireless systems, namely, 5G. Radio network planning (RNP) is one of the essential stages in deploying a wireless network that meets certain coverage, capacity and quality of service (QoS) requirements. While the RNP problem has been studied for existing wireless standards, the major advancements introduced in the upcoming 5G standard necessitate a reinvestigation of the problem. To this end, this paper investigates the RNP process in the context of the upcoming 5G networks. The planning process will minimize and optimize the locations of base stations (BSs) in a selected geographical area using a heuristic algorithm. Even though 5G is still being standardized, the paper will take into account some of the key aspects that would constitute the core of next generation networks such as the use of millimeter wave (mmw) carrier frequencies, and the eventual deployment of heterogeneous and dense networks. Different facets of the 5G RNP process are evaluated for various network scenarios.

A modified joint uplink-downlink opportunistic scheduling for Quality of Service guarantees

Quality of Service (QoS) is a very important metric in wireless communication systems, where both Uplink (UL) and Downlink (DL) connections request strict QoS demands in terms of rate, delay, etc. for their proper operation. The development of wireless communications standards and the emergence of new interactive and conversational services with bi-directional QoS requirements changes the scheduling context from a link-level to a system level. To this end, this paper presents a joint UL-DL bandwidth allocation approach that considers outage as the main QoS parameter to be minimized. The well-known opportunistic scheduling algorithm is first modified to account for the UL-DL coupling and a mathematical expression of the outage probability is derived. Then the expression is employed in the joint UL-DL bandwidth allocation problem. The formulated problem is shown to be a convex optimization problem. Simulation results demonstrate the merits of the proposed approach compared to traditional techniques.

SIRA: A socially inspired game theoretic uplink/downlink resource aware allocation in OFDMA systems

Given the exploding number of mobile subscribers and the quality of service requirements of emerging mobile services specially the multimedia ones, efficient use of the limited network resources has become so important that it is driving development of intelligent resource allocation (RA) algorithms. Whereas link specific RA problems have been widely investigated in the literature targeting either the uplink or downlink of a communication system, we present in this paper, SIRA, a novel joint uplink/downlink RA scenario in an OFDMA system for users running symmetrical services on their mobile devices. The RA process is modeled as a social gaming paradigm where users are considered as players interacting with the base station which takes the role of a principal controlling the RA game. Intelligently evolving from a soft RA and inspired by the model of team development proposed by Bruce Tuckman, SIRA uses penalty based concepts which play a feedback mechanism role from a system theory perspective to finalize the decision on allocated resources. Simulation results show the merit of the proposed technique and motivate follow on research.

Joint dynamic switching point configuration and resource allocation in TDD-OFDMA networks: optimal formulation and suboptimal solution

With the large increase in data services with asymmetric traffic loads, the time division duplexing TDD mode of operation of the next generation cellular wireless standards has gained an increasing interest from both cellular network operators and the research community. However, the introduction of TDD has raised several critical design requirements. Among others, the introduced flexibility in splitting resources between the uplink and downlink directions makes of the uplink/downlink switching point configuration a major design problem, especially that it is directly connected to other design aspects such as resource allocation and interference mitigation. In this paper, we formulate joint switching point configuration and resource allocation in TDD systems as an optimization problem with the objective of minimising the total interference under traffic load and other network constraints. The problem is then reformulated by linearizing some of the nonlinear terms. Because of the persistent difficulty of the problem, we propose a three-stage suboptimal algorithm. The algorithm clusters the cells in a given network into different groups depending on the susceptibility of cells to interfere on each other with emphasis on base station-base station and mobile station-mobile station interference. Switching point configuration using standardised long term evolution LTE frame structures and multicell resource allocation utilising uplink and downlink interference indicators are subsequently performed independently. Simulation results show the merits of the proposed approach compared with traditional techniques by offering attractive trade-offs between interference mitigation and traffic adaptation. Copyright

On delay-aware joint uplink/downlink resource allocation in OFDMA networks

The advancement of wireless communications standards and the introduction of new services with tight bidirectional quality of service requirements necessitated the development of novel and intelligent resource allocation algorithms. These include delay-aware scheduling techniques to cope with the tight round trip delay constraints imposed by the standards. In this paper, we present a novel delay-aware joint uplink/downlink resource allocation algorithm that controls the scheduling process in one direction by using delay information from the other direction. The main idea behind this design is the balancing of the transmission delays between the uplink and downlink to avoid resource wastage and service degradation that can result from transmission imbalances. Results show an improved constrained delay behavior of the system. Moreover, using the definition of a satisfaction index based on the well-known Jain fairness index, we show how our proposed scheme outperforms traditional single-link resource allocation schemes in terms of user satisfaction.