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Al-Kanj L.,American University of Beirut | Dawy Z.,American University of Beirut | Yaacoub E.,Wireless Innovations Center
IEEE Communications Surveys and Tutorials | Year: 2013

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. © 1998-2012 IEEE.

Tadayon N.,University of Quebec at Montreal | Askari E.,University of Quebec at Montreal | Aissa S.,University of Quebec at Montreal | Khabazian M.,Wireless Innovations Center
IEEE Systems Journal | Year: 2012

In this paper, we present a novel analytical model for the service delay in IEEE 802.11 networks. This model is capable of closely tracking service delay's behavior in real wireless local area networks. We find a compact closed-form expression for the probability-generating function (PGF) of service delay using which all higher-order moments are achievable. We begin with finding the service-delay PGF; then we determine the probability density (mass) function of the delay metric by taking the inverse $z$-transform using numerical methods. At last, by comparing the first two statistical moments of this PGF with the mean delay and standard deviation from simulation results, the accuracy of the proposed analytical model is proved. © 2012 IEEE.

Yaacoub E.,Wireless Innovations Center | Dawy Z.,American University of Beirut
2011 IEEE Wireless Communications and Networking Conference, WCNC 2011 | Year: 2011

Cognitive radio networks are receiving a lot of research attention lately. Most user equipment in state-of-the-art wireless communication systems are equipped with two antennas. In this paper, we take advantage of the two transmit antennas in an underlay cognitive radio network scenario. Secondary users use the two transmit antennas in order to insert a null in the direction of the primary base station, thus protecting primary users from interference on their uplink transmissions. Primary users benefit from the antennas in order to perform beam steering in direction of the primary BS, thus enhancing their uplink SINR without being concerned of the presence of the secondary users. This has the additional possible benefit of directing most primary radiation away from the secondary BS, thus reducing the interference on uplink secondary transmissions. © 2011 IEEE.

Yaacoub E.,Wireless Innovations Center | Dawy Z.,American University of Beirut
IEEE Communications Surveys and Tutorials | Year: 2012

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. © 1998-2012 IEEE.

Khabazian M.,Wireless Innovations Center | Mehmet-Ali M.,Concordia University at Montreal | Aissa S.,University of Quebec at Montreal
IEEE Systems Journal | Year: 2013

In this paper, we study the steady-state statistical properties of continuous communication path availability in vehicular ad hoc networks. We assume a network of highways with arbitrary topology. The mobile nodes arrive at the network through one of the traffic entry points following a Poisson process and move along a path according to a mobility model with a state-dependent mean speed. First, the joint distribution of the number of nodes in the highway segments of the network is determined. Then, the number of clusters in the node population of a network path is modeled as a Markovian birth-death process where a cluster is defined as a group of nodes that may communicate with each other directly or indirectly. Thus, the probability distributions of the number of clusters in a path and duration of continuous communication path availability time are derived as functions of mobility and traffic arrival parameters. We present mean durations of continuous availability and unavailability times and mean packet delay for end-to-end communications in a path. The given numerical results illustrate the effects of mobility and traffic arrival process on continuous communication path availability and packet delay. The results show that the mean durations of path availability and mean packet delay increase with the increasing transmission range. Clearly, while high path availability duration is desired but not high packet delay. Thus, the transmission range should not be chosen higher than needed for acceptable communication path availability, so as to maintain an acceptable mean packet delay. In practice, an adaptive transmission range may be required to achieve the right balance between the communication path availability and delay. The analytical results have also been compared with some available experimental studies and verified by two different simulation approaches. © 2007-2012 IEEE.

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