Ayman Khalil

CROSS -LAYER RESOURCE ALLOCATION SCHEME UNDER HETEROGENEOUS CONSTRAINTS FOR NEXT GENERATION HIGH RATE WPAN

In the next generation wireless networks, the growing demand for new wireless applications is accompanied with high expectations for better quality of service (QoS) fulfillment especially for multimedia applications. Furthermore, the coexistence of future unlicensed users with existing licensed users is becoming a challenging task in the next generation communication systems to overcome the underutilization of the spectrum. A QoS and interference aware resource allocation is thus of special interest in order to respond to the heterogeneous constraints of the next generation networks. In this work, we address the issue of resource allocation under heterogeneous constraints for unlicensed multiband ultra-wideband (UWB) systems in the context of Future Home Networks, i.e. the wireless personal area network (WPAN). The problem is first studied analytically using a heterogeneous constrained optimization problem formulation. After studying the characteristics of the optimal solution, we propose a low-complexity suboptimal algorithm based on a cross-layer approach that combines information provided by the PHY and MAC layers. While the PHY layer is responsible for providing the channel quality of the unlicensed UWB users as well as their interference power that they cause on licensed users, the MAC layer is responsible for classifying the unlicensed users using a two-class based approach that guarantees for multimedia services a high-priority level compared to other services. Combined in an efficient and simple way, the PHY and MAC information present the key elements of the aimed resource allocation. Simulation results demonstrate that the proposed scheme provides a good tradeoff between the QoS satisfaction of the unlicensed applications with hard QoS requirements and the limitation of the interference affecting the licensed users.

Efficient Network Coding packet selection model for QoS-based applications

In this paper, we study Network Coding (NC) at switching level. We use a novel NC algorithm to select, among received packets, those to be coded and released into the network. The selection is based on address correlation and QoS is attained based on delay optimization. The main feature of our algorithm is that it enhances the coding decision and guarantees decodability of transmitted packets. We developed a testing model to evaluate the performance of our proposed algorithm. Significant throughput and QoS improvements can be observed when our algorithm is compared with traditional NC schemes.

Aging in Network Coding

With network coding, received packets are linearly combined together and broadcasted over the network. Several techniques exist in the literature dedicated to the process of combining packets. However, these techniques focus on forwarding and decoding coded packets without taking into consideration the life cycle of each individual packet. By neglecting this issue, a packet might live forever in coded messages introducing an overhead on the coding/decoding process. In this letter, we introduce the concept of aging that limits the existence of a packet within coded messages. Statistics about the effect of aging on the size of coded messages are provided in order to determine the best tradeoff between the number of required transmissions and then the throughput gain on one hand and the buffering size and then the decoding complexity on the other hand.

Novel distributed decoding scheme for efficient resource utilization in network coding

In this paper, we introduce network coding (NC) at intermediate nodes of a linear network where coding is conducted on address correlated packets. In particular, we propose a novel algorithm for decoding network-coded messages that enhances the bandwidth usage and reduces the resource allocation by allowing nodes in the network to perform distributed decoding. We show that, compared to traditional decoding at end nodes, distributed decoding allows reduction not only in the number of transmitted bytes but also in the number of resources needed to perform NC. Our strategy is compared to decoding at end nodes and experiments show a reduction of 64% in the number of transmitted bytes and a reduction of 93% of buffering time when using distributed decoding to exchange 1000 packets between end nodes of a linear network of 8 nodes.

Optimizing Context-Aware Resource and Network Assignment in Heterogeneous Wireless Networks

This paper discusses the problem of user association and downlink resource allocation in heterogeneous wireless networks (HWNs) where a mobile node (MN) can associate to a single network at a time. A context-aware optimization problem is formulated to maximize the aggregate user-centric profit in the system while taking into consideration the network constraints, user preferences, and the amount of data rate requested by each MN. To achieve its purpose, the formulated problem employs contextual information related to the MN measurements and requirements, the HWN architecture, and the available resources at each network. The user-centric profit is based on the quality of the received signal and the power consumption at the MN. The formulated optimization problem is discrete (binary) with high complexity; based on the continuous relaxation of the problem, a solution with polynomial-time complexity is proposed. It is shown through simulations that the proposed solution achieves a nearoptimal performance in terms of average user-centric profit and percentage of blocked data rate. Moreover, the proposed solution requests lower number of handovers.

Load-aware power efficiency maximization in heterogeneous wireless networks

This paper proposes a solution to maximize the power efficiency, i.e. datarate per power unit, in a heterogeneous wireless system that is based on integrated mobile base stations (BSs) and Wi-Fi access points (APs). In this context, a user association and downlink resource allocation optimization problem is formulated. The formulated problem considers the power consumption at both networks and mobile terminals (MTs), and the data rate requirement, i.e. load, of each MT. Since MTs could only be associated with a single network at a time, the formulated problem is binary with high complexity. Thus, a new sub-optimal solution with polynomial-time complexity is proposed based on the continuous relaxation of the problem. Simulation results show that the proposed sub-optimal solution, when compared to the trivial network selection methodology, remarkably reduces the power consumption of networks and MTs. Moreover, it is shown that the proposed solution performs close to the optimal one.

Context-aware network selection algorithm for heterogeneous wireless networks

In this paper, a network selection algorithm for heterogeneous wireless networks (HWNs) is proposed. The proposed solution deploys contextual information related to the user preferences, user data rate requirements, and networks constraints. Networks are ranked based on a weighted profit function that combines two attributes: the relative received signal strength (RRSS) and the mobile terminal (MT) power consumption. The weight of each parameter is based on the user preference. The formulated problem aims at maximizing the profit of the MT, while considering the access technology resource allocation constraints and the data rate requirement of the MT. A novel network selection algorithm is proposed to solve the formulated problem. Simulation results verify that the proposed solution could be effectively tunned to meet user preferences.

Fault-tolerant minimal retransmission mechanism with network coding

A new coding mechanism is provided to automatically detect and recover lost packets in wireless lossy networks. Contrary to the majority of automatic repeat request (ARQ) algorithms relying on acknowledgment, our mechanism extracts feedback on packet delivery by analyzing received network coded messages and automatically reacts when packet loss is sensed. Compared to traditional end-to-end ARQ, our proposed mechanism shows significant reduction in the number of transmissions required to exchange the same amount of data.

Admission control and resource allocation in IEEE 802.15.5 HDR WPAN

In this paper, we propose a novel admission control and centralized channel time allocation algorithm for two-hop communications based on the IEEE 802.15.5 specifications. The first contribution is the introduction of a dynamic superframe size for efficient resource utilization. The second contribution adopts the use of a threshold concept and a flag metric, which jointly provide satisfaction and fairness among the requesting devices. The performance of the proposed algorithm is evaluated and the results show that the proposed approach achieves good performance in terms of satisfaction and fairness.

Chaos-based video encryption for network coded wireless systems

The ease of sharing information happening today increases the number of data transmissions over the Internet, which started by a simple text transmission, and evolved to more complex formats, such as image, audio and video. This data can then be easily accessed by attackers, hence the need for security. In this paper, we propose a modification to the Enhanced 1D Chaotic Key Based Encryption (ECKBA) with cat map that will be applied on video transmission (sequence of images), by changing the confusion and diffusion blocks, in order to ensure a higher level of security. Moreover, to guarantee the security for real-time applications transmitted over an unreliable network, we include a method that combines the new scheme with the Network Coding principle.