Zaher Dawy

A Survey on Uplink Resource Allocation in OFDMA Wireless Networks

OFDMA has been selected as the multiple access scheme for state-of-the-art wireless communication systems. Efficient resource allocation in OFDMA wireless networks is essential in order to meet the quality of service requirements of emerging services. In this paper, a survey of resource allocation and scheduling schemes in OFDMA wireless networks is presented. The focus is on the uplink direction. Resource allocation is surveyed in various scenarios: centralized and distributed, instantaneous and ergodic, optimal and suboptimal, single cell and multicell, cooperative and non-cooperative, in addition to different combinations of these variants. Directions for future research are outlined.

Toward Massive Machine Type Cellular Communications

Cellular networks have been engineered and optimized to carrying ever-increasing amounts of mobile data, but over the last few years, a new class of applications based on machine-centric communications has begun to emerge. Automated devices such as sensors, tracking devices, and meters, often referred to as machine-to-machine (M2M) or machine-type communications (MTC), introduce an attractive revenue stream for mobile network operators, if a massive number of them can be efficiently supported. The novel technical challenges posed by MTC applications include increased overhead and control signaling as well as diverse application-specific constraints such as ultra-low complexity, extreme energy efficiency, critical timing, and continuous data intensive uploading. This article explains the new requirements and challenges that large-scale MTC applications introduce, and provides a survey of key techniques for overcoming them. We focus on the potential of 4.5G and 5G networks to serve both the high data rate needs of conventional human-type communication (HTC) subscribers and the forecasted billions of new MTC devices. We also opine on attractive economic models that will enable this new class of cellular subscribers to grow to its full potential.

A Game Theoretical Formulation for Proportional Fairness in LTE Uplink Scheduling

Uplink scheduling in LTE systems is considered. A game theoretical formulation is derived where the scheduling problem is represented as a Nash bargaining solution. An algorithm to implement the proposed scheduling scheme is presented. Throughput and fairness analysis are performed via simulations. Results show that channel aware scheduling schemes outperform the round-robin scheme, but a tradeoff must be made between the increase of total throughput and fairness towards the different users.

Implementation and evaluation of cooperative video streaming for mobile devices

A promising approach for power reduction in mobile devices is peer-to-peer cooperation. In this paper, we present a testbed system implementation to evaluate the performance of an infrastructure controlled cooperative video streaming architecture. A number of mobile devices in close proximity are connected to the Internet through a wireless access point and are all requesting the same video stream from a dedicated server. Instead of sending the stream independently to each device, the server distributes the video packets among the devices, over a long-range wireless link using WLAN technology; the devices then exchange the received packets among each other over short-range wireless links using Bluetooth technology. The implemented testbed is used to experimentally demonstrate the power reduction gains in mobile devices and to derive an analytical model that relates power consumption to various design and system parameters.

Coverage and capacity enhancement of CDMA cellular systems via multihop transmission

The uplink coverage and capacity of CDMA cellular systems are intracell and intercell interference limited. In this work, we propose a practical multihop based cellular network design to enhance the uplink performance. The proposed design is based on dividing each cell into two regions where users belonging to an inner region communicate with the base station (BS) using one hop and users belonging to an outer region communicate with the BS using two hops. Each of the two regions is allocated a separate frequency channel to enable practical implementation and reduce interference. Analytic results show that intercell interference in CDMA cellular systems can be reduced by more than 75%. Moreover, a link budget analysis is performed to obtain coverage-capacity results with different receiver structures at the BS. Results show that with the single user detector (SUD) receiver, gains up to 100% in area coverage are achieved with moderate to low user loads. Furthermore, deploying multiuser detection to combat intracell interference, the proposed multihop based design achieves very high gains exceeding 100% in pole capacity and 300% in area coverage per cell.

Energy-Aware Cooperative Content Distribution over Wireless Networks: Design Alternatives and Implementation Aspects

This paper presents a comprehensive overview on the area of energy-aware common content distribution over wireless networks with mobile-to-mobile cooperation. It is assumed that a number of mobile terminals (MTs) that are geographically close to each other are interested in downloading the same content from a server via a base station using a long-range wireless technology. Selected MTs download the content directly from the base station and transmit it to other MTs using a short-range wireless technology. This cooperation can lead to significant performance gains since short-range wireless technologies are energy efficient and provide higher data rates due to the geographical proximity among the MTs. In this paper, we highlight the main alternatives that shape the design of cooperative content distribution architectures with focus on energy efficiency. These include content segmentation, long-range and short-range distribution strategies, grouping of the MTs into cooperating clusters, single hop and multihop communications among the MTs, resource allocation, fairness considerations, and network dynamics. We also discuss various methods commonly utilized for developing content distribution algorithms and evaluating network performance. Finally, we present sample results for selected network scenarios, discuss related standardization activities, and highlight future research directions.

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.

Energy-Efficient Cooperative Video Distribution with Statistical QoS Provisions over Wireless Networks

For real-time video broadcast where multiple users are interested in the same content, mobile-to-mobile cooperation can be utilized to improve delivery efficiency and reduce network utilization. Under such cooperation, however, real-time video transmission requires end-to-end delay bounds. Due to the inherently stochastic nature of wireless fading channels, deterministic delay bounds are prohibitively difficult to guarantee. For a scalable video structure, an alternative is to provide statistical guarantees using the concept of effective capacity/bandwidth by deriving quality of service exponents for each video layer. Using this concept, we formulate the resource allocation problem for general multihop multicast network flows and derive the optimal solution that minimizes the total energy consumption while guaranteeing a statistical end-to-end delay bound on each network path. A method is described to compute the optimal resource allocation at each node in a distributed fashion. Furthermore, we propose low complexity approximation algorithms for energy-efficient flow selection from the set of directed acyclic graphs forming the candidate network flows. The flow selection and resource allocation process is adapted for each video frame according to the channel conditions on the network links. Considering different network topologies, results demonstrate that the proposed resource allocation and flow selection algorithms provide notable performance gains with small optimality gaps at a low computational cost.

Optimized energy efficient content distribution over wireless networks with mobile-to-mobile cooperation

Mobile terminals interested in the same content and that are in the vicinity of each other can cooperate to improve the efficiency of the download process. In this paper, content distribution and cooperation among the mobile terminals is coordinated by the base station which is the centralized entity that runs an optimization framework to minimize energy consumption at mobile terminals while guaranteeing quality of service constraints. Two cooperation cases are investigated where the mobile terminals can either unicast or multicast the content they receive from the base station to each other. Results show that as the number of cooperating mobile terminals increases the total energy consumption decreases compared to the non-cooperative case.

Optimization Models and Algorithms for Joint Uplink/Downlink UMTS Radio Network Planning With SIR-Based Power Control

Universal mobile telecommunication system (UMTS) networks should be deployed according to cost-effective strategies that optimize a cost objective and satisfy target quality-of-service (QoS) requirements. In this paper, we propose novel algorithms for joint uplink/downlink UMTS radio planning with the objective of minimizing total power consumption in the network. Specifically, we define two components of the radio planning problem: 1) continuous-based site placement and 2) integer-based site selection. In the site-placement problem, our goal is to find the optimal locations of UMTS base stations (BSs) in a certain geographic area with a given user distribution to minimize the total power expenditure such that a satisfactory level of downlink and uplink signal-to-interference ratio (SIR) is maintained with bounded outage constraints. We model the problem as a constrained optimization problem with SIR-based uplink and downlink power control scheme. An algorithm is proposed and implemented using pattern search techniques for derivative-free optimization with augmented Lagrange multiplier estimates to support general constraints. In the site-selection problem, we aim to select the minimum set of BSs from a fixed set of candidate sites that satisfies quality and outage constraints. We develop an efficient elimination algorithm by proposing a method for classifying BSs that are critical for network coverage and QoS. Finally, the problem is reformulated to take care of location constraints whereby the placement of BSs in a subset of the deployment area is not permitted due to, e.g., private property limitations or electromagnetic radiation constraints. Experimental results and optimal tradeoff curves are presented and analyzed for various scenarios.