wissam fawaz
Wissam Fawaz received a B.E. in computer engineering with high honors from the Lebanese University in 2001. In 2002, he earned an M.S. degree in network and information technology with high honors from the University of Paris VI. Next, he received a Ph.D. degree in network and information technology with excellent distinction from the University of Paris XIII in 2005. Between 2002 and 2004, he managed a scientific research project on optical service management at ALCATEL research and innovation, Marcoussis, France. At the University of Paris XIII, he worked as a teaching assistant of computer engineering from 2002 until 2006. He joined the Lebanese American University (LAU) as assistant professor of computer engineering in october 2006 and was promoted to the rank of associate professor in september 2012. He is teaching the following courses at LAU: computer networks, data structures, computer programming, optical networks, coe application, and queueing theory. His current research interests are in the areas of optical networks, delay/disruption tolerant networks, and queueing theory. Dr. Fawaz was the recipient of the French ministry of research and education scholarship for distinguished students in 2002 and of a Fulbright research award in 2008. He is a senior member of the IEEE . He served as an Associate Editor for the IEEE Communications Letters journal and is currently serving as associate editor for the Springer Journal of Annals of Telecommunications.
Phone: +961.9.547254 Ext: 2414
Address: Lebanese American University
P.O. Box 36 / ECE Dept
Byblos Lebanon
Phone: +961.9.547254 Ext: 2414
Address: Lebanese American University
P.O. Box 36 / ECE Dept
Byblos Lebanon
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the travel experience of commuting passengers. However, the existence of an end-to-end multi-hop path
across VANET highly depends on the willingness of vehicles to cooperate with one another when it
comes to data forwarding. Unlike the existing VANET connectivity studies that focused solely on fullycooperative
vehicular environments, this paper develops a mathematical model to explain the effect of
non-cooperative vehicles on the end-to-end connectivity through the roadway segments of a VANET.
First, this work characterizes some of the fundamental traffic-theoretic properties of VANETs in the presence
of non-cooperative vehicles. Then, it proposes to alleviate the detrimental effect of non-cooperation
on end-to-end path connectivity by exploiting Unmanned Aerial Vehicles (UAVs) as store-carry-andforward
nodes in a VANET. Through both mathematical analysis and extensive simulations, the role that
UAVs can play in enhancing end-to-end path connectivity is quantified in the context of a hybrid, UAVassisted
VANET architecture.
were proposed as a means for remedying the effects of the
various atmospheric impairments on the quality of the FSO
signal. Conventional relay-assisted FSO systems are however
designed around two basic assumptions: a) relays are buffer-free,
and b) relays are stationary. This paper proposes to improve
the performance of the existing relay-assisted FSO systems by
relaxing both of these highly restrictive assumptions through
the integration of Unmanned Aerial Vehicles (UAVs) as bufferaided
moving relays into the conventional relay-assisted FSO
systems. Specifically, two possible simple integration scenarios
are proposed and analyzed through simulation. The obtained
simulation results demonstrate the great potential associated
with the proposed highly promising, innovative, hybrid FSO
architecture. Given that high performance gains are observed
under small buffer sizes, it becomes conceivable to employ the
buffer-aided moving relaying UAVs to serve a variety of other
purposes. This includes, for instance, having these UAVs oversee
the operation of amateur drones for potential misbehavior or
wrongdoing within the area of their deployment.
(VANET) establishes a strong foundation for the development of
smart cities, where one of the main objectives is the improvement
of the welfare of commuting passengers. The availability of a
multi-hop path across a VANET system, through Vehicle-toVehicle
(V2V) communication, depends mainly on the vehicular
density and the willingness of vehicles to cooperate with one
another. This paper proposes to minimize the path availability’s
dependence on vehicular density and cooperation, by utilizing
Unmanned Aerial Vehicles (UAVs). Particularly, this work explores
both mathematically as well as through an extensive
simulation study the advantages of exploiting UAVs as storecarry-forward
nodes so as to enhance the availability of a
connectivity path as well as to reduce the end-to-end packet
delivery delay. The obtained results shed clear light on the
benefits emanating from the coupling of UAVs with vehicles in
the context of a highly promising, innovative, hybrid vehicular
networking architecture
in the case where the relays are equipped with buffers of finite size. The high directivity of the FSO
links clearly distinguishes cooperative FSO networks from their Radio Frequency (RF) counterparts thus
motivating the design of FSO-specific Buffer-Aided (BA) cooperative protocols. We propose three novel
Decode-and-Forward (DF) relaying protocols that are adapted to the nature of FSO transmissions and
that are capable of achieving different levels of tradeoff between outage probability, average packet delay
and system complexity. (i): The BA selective relaying protocol that can be implemented in the presence
of Channel State Information (CSI) and that outperforms the RF max-link protocol with a reduced delay.
(ii): The BA all-active relaying protocol that can be implemented in the absence of CSI. This constitutes
the simplest protocol with the best delay performance at the expense of a degraded outage performance.
(iii): The BA load-balanced selective protocol where supplementary FSO communications are triggered
along the inter-relay links for a more balanced distribution of the packets among the buffers. While the
last protocol incurs the highest signaling complexity, it results in significant performance gains with a
delay that is comparable to that of the BA selective protocol. A Markov chain analysis is adopted for
evaluating the system outage probability and the average packet delay where the corresponding state
transition matrices are derived in the cases of both symmetrical and asymmetrical networks.
which the intersection operates. A major challenge in this regard is the ability to accurately estimate all the
components underlying the overall control delay, including the uniform, incremental and initial queue delays.
This paper tackles this challenging task by proposing a novel exact model of the uniform control delay
component with a view to enhancing the accuracy of the existing approximate models, notably, the one reported
in the Highway Capacity Manual 2010. Both graphical and analytical proofs are employed to derive
exact closed-form expressions for the uniform control delay at undersaturated signalized intersections.
The high degree of accuracy of the proposed models is analysed through extensive simulations to demonstrate
their abilities to exactly characterize the performance of real-life intersections in terms of the
resulting vehicle delay. Unlike the existing widely adopted uniform delay models, which tend to overestimate
the LOS of real-life intersections, the delay models introduced in this paper have the merit of exactly
capturing such a LOS
(V2I) communication system. Existing mathematical models for such a
system overlook some of its essential behavioural characteristics such as the reneging,
force-termination and ultimately blocking of service requests. A multi-server queueing
model with First-In–First-Out (FIFO) service policy is proposed for the purpose of accurately
capturing the dynamics of the above-mentioned communication system and evaluating
its performance. Approximations were exploited as a mean to enhance this model’s
mathematical tractability. Simulations are conducted in the context of a realistic scenario
with the objective of validating the proposed approximate model, verifying its accuracy
and characterizing the system’s performance in terms of several new metrics. The reported
results indicate a cataclysmic access request blocking probability ranging from 66% to 85%.
An Access Request Deadline-Aware (ARDA) service policy is then proposed to reduce the
blocking probability and improve the system’s response time. Indeed ARDA achieved an
improvement over FIFO of almost 70% in terms of the overall blocking probability and 22%
to 66% in terms of the system’s response time.
the travel experience of commuting passengers. However, the existence of an end-to-end multi-hop path
across VANET highly depends on the willingness of vehicles to cooperate with one another when it
comes to data forwarding. Unlike the existing VANET connectivity studies that focused solely on fullycooperative
vehicular environments, this paper develops a mathematical model to explain the effect of
non-cooperative vehicles on the end-to-end connectivity through the roadway segments of a VANET.
First, this work characterizes some of the fundamental traffic-theoretic properties of VANETs in the presence
of non-cooperative vehicles. Then, it proposes to alleviate the detrimental effect of non-cooperation
on end-to-end path connectivity by exploiting Unmanned Aerial Vehicles (UAVs) as store-carry-andforward
nodes in a VANET. Through both mathematical analysis and extensive simulations, the role that
UAVs can play in enhancing end-to-end path connectivity is quantified in the context of a hybrid, UAVassisted
VANET architecture.
were proposed as a means for remedying the effects of the
various atmospheric impairments on the quality of the FSO
signal. Conventional relay-assisted FSO systems are however
designed around two basic assumptions: a) relays are buffer-free,
and b) relays are stationary. This paper proposes to improve
the performance of the existing relay-assisted FSO systems by
relaxing both of these highly restrictive assumptions through
the integration of Unmanned Aerial Vehicles (UAVs) as bufferaided
moving relays into the conventional relay-assisted FSO
systems. Specifically, two possible simple integration scenarios
are proposed and analyzed through simulation. The obtained
simulation results demonstrate the great potential associated
with the proposed highly promising, innovative, hybrid FSO
architecture. Given that high performance gains are observed
under small buffer sizes, it becomes conceivable to employ the
buffer-aided moving relaying UAVs to serve a variety of other
purposes. This includes, for instance, having these UAVs oversee
the operation of amateur drones for potential misbehavior or
wrongdoing within the area of their deployment.
(VANET) establishes a strong foundation for the development of
smart cities, where one of the main objectives is the improvement
of the welfare of commuting passengers. The availability of a
multi-hop path across a VANET system, through Vehicle-toVehicle
(V2V) communication, depends mainly on the vehicular
density and the willingness of vehicles to cooperate with one
another. This paper proposes to minimize the path availability’s
dependence on vehicular density and cooperation, by utilizing
Unmanned Aerial Vehicles (UAVs). Particularly, this work explores
both mathematically as well as through an extensive
simulation study the advantages of exploiting UAVs as storecarry-forward
nodes so as to enhance the availability of a
connectivity path as well as to reduce the end-to-end packet
delivery delay. The obtained results shed clear light on the
benefits emanating from the coupling of UAVs with vehicles in
the context of a highly promising, innovative, hybrid vehicular
networking architecture
in the case where the relays are equipped with buffers of finite size. The high directivity of the FSO
links clearly distinguishes cooperative FSO networks from their Radio Frequency (RF) counterparts thus
motivating the design of FSO-specific Buffer-Aided (BA) cooperative protocols. We propose three novel
Decode-and-Forward (DF) relaying protocols that are adapted to the nature of FSO transmissions and
that are capable of achieving different levels of tradeoff between outage probability, average packet delay
and system complexity. (i): The BA selective relaying protocol that can be implemented in the presence
of Channel State Information (CSI) and that outperforms the RF max-link protocol with a reduced delay.
(ii): The BA all-active relaying protocol that can be implemented in the absence of CSI. This constitutes
the simplest protocol with the best delay performance at the expense of a degraded outage performance.
(iii): The BA load-balanced selective protocol where supplementary FSO communications are triggered
along the inter-relay links for a more balanced distribution of the packets among the buffers. While the
last protocol incurs the highest signaling complexity, it results in significant performance gains with a
delay that is comparable to that of the BA selective protocol. A Markov chain analysis is adopted for
evaluating the system outage probability and the average packet delay where the corresponding state
transition matrices are derived in the cases of both symmetrical and asymmetrical networks.
which the intersection operates. A major challenge in this regard is the ability to accurately estimate all the
components underlying the overall control delay, including the uniform, incremental and initial queue delays.
This paper tackles this challenging task by proposing a novel exact model of the uniform control delay
component with a view to enhancing the accuracy of the existing approximate models, notably, the one reported
in the Highway Capacity Manual 2010. Both graphical and analytical proofs are employed to derive
exact closed-form expressions for the uniform control delay at undersaturated signalized intersections.
The high degree of accuracy of the proposed models is analysed through extensive simulations to demonstrate
their abilities to exactly characterize the performance of real-life intersections in terms of the
resulting vehicle delay. Unlike the existing widely adopted uniform delay models, which tend to overestimate
the LOS of real-life intersections, the delay models introduced in this paper have the merit of exactly
capturing such a LOS
(V2I) communication system. Existing mathematical models for such a
system overlook some of its essential behavioural characteristics such as the reneging,
force-termination and ultimately blocking of service requests. A multi-server queueing
model with First-In–First-Out (FIFO) service policy is proposed for the purpose of accurately
capturing the dynamics of the above-mentioned communication system and evaluating
its performance. Approximations were exploited as a mean to enhance this model’s
mathematical tractability. Simulations are conducted in the context of a realistic scenario
with the objective of validating the proposed approximate model, verifying its accuracy
and characterizing the system’s performance in terms of several new metrics. The reported
results indicate a cataclysmic access request blocking probability ranging from 66% to 85%.
An Access Request Deadline-Aware (ARDA) service policy is then proposed to reduce the
blocking probability and improve the system’s response time. Indeed ARDA achieved an
improvement over FIFO of almost 70% in terms of the overall blocking probability and 22%
to 66% in terms of the system’s response time.