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OPNET Technologies 7255 Woodmont Avenue Tel: 240-497-3000 E-mail: mailto:info@opnet.com OPNET is a registered
trademark of 2001 OPNET Technologies |
[ Research
| Publications | Courses ]
1. Lifetime Optimization for Heterogeneous Networks Using Concentric Rings Muharrem Gün (started 2004)
Lifetime constraint is the limiting feature for Wireless Sensor Networks. Since the data dissemination in sensor networks is towards the sink, the data communication is realized by the relay of the packets of the intermediate nodes in wireless sensor networks. As a result the nodes with high packet relay burden are the ones to go offline first, which are the nodes close to the sink. Moreover; terminations of these nodes means also that, some nodes depend on them to carry their traffic get disconnected, which defines the end of the useful lifetime of the network.
In order to alleviate the non-homogeneous energy drainage pattern, in this thesis study we propose to use different energy capacity sensor nodes and deploy them in a concentric ring shaped areas. The nodes with high battery capacity are located near the sink and those nodes with the weakest capacity are located in the outmost ring. The overall performance of the network will be then maximized and nodes arrive to end of their lifetime at about the same time.
In order to verify the obtained results, simulations were conducted on OPNET Modeler. The proposed network were modeled and simulated using the wireless module of OPNET. Different scenarios were devised and the lifetime of the network were compared.
2. Application Specific Lifetime Measurement for Wireless Sensor Networks Atay Ozgovde (started 2005)
Network Lifetime is the most important performance metric in evaluating the Wireless Sensor Network designs. Existing trend is to measure the lifetime with simplistic metrics, such as the time till the first node death. However, almost every aspect of the WSN design should be considered in an application dependent context and lifetime measurement is no exception. In this work, we propose a general framework to enable the network lifetime measurement be carried out in an application dependent manner. We show, through OPNET simulations, that metrics that do not reflect the requirements of the application lead to incorrect lifetime results and that with our proposed framework lifetime can be measured more realistically.
3. Quality of Service in Wireless Metropolitan Area Networks Sukru Kuran (started 2005)
As an wireless
alternative to xDSL and Cable modem systems, the importance of WMAN systems
has increased significantly in the recent years. The most important standard
in WMAN systems is IEEE 802.16 or WiMAX. IEEE 802.16 is expected to provide
detailed QoS support to support different application types. The basis
operating mode of WiMAX, the point-to-multipoint (PMP) mode has a detailed
QoS mechanism. On the other hand, the second operating mode, the mesh mode,
only provides a simple QoS management mechanism. We developed a Mesh mode
model of IEEE 802.16 using the centralized scheduling method using OPNET.
With this model we are developing more detailed QoS mechanisms for the Mesh
mode of IEEE 802.16 and provide performance evaluations for these
mechanisms. So far, we have developed a method for incorporating the QoS
mechanism of the PMP mode of IEEE 802.16 to the centralized scheduling
method in Mesh mode. Our current task is to extend this method to the
distributed scheduling method in the Mesh mode. 4. QoS with OFDM for B3G Wireless Systems Ali Akkaya (started 2006)
5. Packet Traffic Modeling for Intrusion Detecting WSN Ilker Demirkol (started 2006)
6. HANDOVER MANAGEMENT ALGORITHMS IN LEO SATELLITE COMMUNICATION NETWORKS Ayşegül Tüysüz (completed 2006)
One of the major problems with
LEO satellites is their higher speed relative to the terrestrial mobile
terminals, which move at lower speeds but at more random directions. This
high mobility characteristic of LEO satellites causes mobile users to hand
over between footprints of adjacent satellites very frequently. Therefore,
handover management in LEO satellite networks becomes a
7. VoIP Performance over Satellite Networks with On-Board Processing Capabilities Suzan Bayhan (completed 2006)
In this study, an adaptive routing policy utilizing the real-time network information of a two-layered satellite network is introduced. In a satellite network, depending on the requirements and properties of services provided, various kinds of satellites from different orbits can be employed. Geostationary Earth Orbit (GEO) systems are not suitable for Voice over Internet Protocol (VoIP) applications due to long end-to-end delay values about 250-270 ms. Non-Geostationary Earth Orbit (NGEO) systems consisting of Low Earth Orbit (LEO) and Medium Earth Orbit (MEO) satellites can satisfy the performance requirements of VoIP applications. Moreover, a two-layered system of LEOs and MEOs can outperform single plane satellite networks. However, due to the dynamic topology of these networks and nonuniform traffic distribution over the Earth, terrestrial packet based routing algorithms cannot perform well. The proposed routing scheme dubbed as Adaptive Routing Protocol for Quality of Service" (ARPQ) prevents the congestion on some bottleneck links by distributing the traffic over the entire network. Furthermore, link capacities can be efficiently used. Additionally, delay and jitter sensitive voice traffic is processed in a prioritized way to prevent long queueing delays.
By a set of simulations, we showed that proposed mechanism performs better than nonadaptive routing mechanisms and therefore can enable VoIP applications over satellite networks.We used OPNET Modeler 10.5 A to model our scenarios. OPNET Wireless Module provides extensive simulation and modeling tools. Using the Transceiver Pipeline, link properties (e.g. delay, bit error rate) can be controlled. Link properties are modeled using different settings at each pipeline stage. Random error and burst error models are simulated. Various performance parameter statistics are collected and analyzed.
8.
Service
Differentiation for QoS-aware Multicast Routing in Kaan Bur (completed 2006) Recent developments in wireless
mobile telecommunications and portable computing devices, as well as the
increasing importance of multimedia applications on the Internet have
stimulated a conceptual shift in users' expectations towards group-oriented,
mobile multimedia communication. For this new generation of networks,
mobility, quality of service (QoS) support, and
multicast routing are essential components. To this end, the ad hoc QoS multicast (AQM) routing protocol has been developed
recently (see below). AQM covers the admission control, resource reservation
and routing aspects of the ad hoc QoS multicast
problem. At this point, it is necessary to combine AQM with priority
assignment and fair scheduling mechanisms, such that the final design also
covers the service differentiation aspect of QoS. The purpose of this work is to design a service differentiation component for AQM. The protocol in its final form will differentiate between QoS and best-effort traffic coexisting in the network, and apply intelligent queuing and scheduling strategies to meet the QoS requirements of both real-time multimedia as well as bursty data flows. Performance metrics such as throughput, delay, packet delivery rate, overhead and multicast efficiency will be measured. It is strongly recommended by IETF MANET that these performance metrics should be considered in the experiments during the evaluation of the proposed schemes. Simulations will be based on realistic network dynamics and mobility patterns. The simulations will be conducted on the OPNET Modeler, which is a verified and widely accepted network simulator with many ad hoc networking capabilities, in order to evaluate the performance of the final QoS multicast routing protocol.
9.
Quality-of-Service-Aware Multicast
Routing for Multimedia Applications in Kaan Bur (completed 2005) The conceptual shift in the
expectations of wireless users from voice towards multimedia, from
availability towards acceptable quality, and from stand-alone towards
group-oriented computing has a significant impact on today's networks in
terms of the need for mobility, quality of service (QoS)
and multicast routing. Ad hoc networks, being independent of any fixed
infrastructure, can provide mobile users with these features. However, it is
imperative for ad hoc networks to combine QoS and
multicast routing strategies in order to utilize the wireless medium
efficiently. This work defines the ad hoc QoS multicast routing (AQM) protocol, which achieves
multicast efficiency by tracking the availability of resources for each node
within its neighbourhood. Computation of free
bandwidth is based on reservations made for ongoing sessions and the
requirement reported by the neighbours. Current QoS status is announced at session initiation and updated
periodically to the extent of QoS provision. Nodes
are prevented from applying for membership if there is no QoS
path for the session. When nodes wish to join a session with certain service
requirements, a three-phase process consisting of request, reply and reserve
steps ensures that the QoS information is updated
and used to select the most appropriate routes. The allowed maximum hop count
of the session is taken into account in order to satisfy the delay
requirements of the multimedia applications. To cope with the continuous
nature of streaming multimedia, AQM nodes check the availability of bandwidth
within their neighbourhood not only for themselves
but within a virtual tunnel of nodes. Objection queries are issued prior to
reservation to avoid excessive resource usage due to allocations made by
nodes which cannot detect each other directly. New performance metrics are
introduced to evaluate the efficiency of AQM regarding the satisfaction level
of individual members as well as the success rate of sessions. The
simulations are based on realistic membership dynamics and mobility patterns.
They are conducted using the OPNET Modeler, which is a verified and widely
accepted network simulator with many ad hoc networking capabilities.
Simulation results show that, by applying novel QoS
management techniques, AQM significantly improves multicast efficiency for
members as well as sessions.
10.
Quantifying
Energy Saving using Multi-Hop Links in Wireless Sensor Networks E. Ilker Oyman
(completed 2004) Wireless sensor networks consist
of small sensor elements which are distributed randomly over the area under
investigation. Sensor nodes are equipped with very limited computational
resources and battery power. Therefore, the underlying network architecture
must provide with power aware techniques as a primary design constraint. In this work, we present the use
of multi-hop communication links. The gain in total energy is calculated
using analytical techniques. We show that shorter links must be employed
whenever possible,
in order to prolong the network lifetime. The model is built on the OPNET
Modeler. The sensor network consists of several sensor nodes and one
destination node. Each sensor node is deciding on the output power level of
its transmitter circuitry and therefore is adjusting its transmission range
and hence its power consumption. According to scenarios, the amount of energy
saving is calculated, and the expected network lifetime is compared among the
scenarios.
11.
Large Scale
Multiple Sink Wireless Sensor Network Design E. Ilker Oyman
(completed 2003) Wireless sensor networks consist
of small sensor elements which are distributed randomly over the area under
investigation. After deployment of sensor nodes to the environment, the
network is organized so that the data can be propagated to the control
center. Each sensor node senses the
environment and extracts the necessary data. Thereafter, this data is sent to
the next sensor node which is responsible to forward the data packet towards
the control center. In large scale networks, the network should be divided
into smaller subnetworks to achieve scalability. At
the center of these subnetworks, some special nodes
should be used as concentrators. The sensors redirect their data packets to
these concentrators. These nodes are mainly collecting the data from the
sensors, and forward them to the control center. They are powerful gateway
elements which can communicate with sensors, with each other, and also with
the global network. This work focuses on finding
locations of concentrators on large scale static wireless sensor networks.
The objective is to minimize the number of concentrator nodes as their cost
is much higher than sensor nodes. On the other hand, they must be sufficient
to maximize total network life optimizing power usage of the sensor nodes. We
have implemented a self-organizing map approach to this well known
concentrator location problem using the OPNET Modeler. The results achieved
by our network simulations are proven to be of high quality.
12.
Routing In A
LEO Network Using Min Flow Max Residual Path In A Routing Set Roy Kucukates (completed 2002) Low Earth Orbit (LEO) satellite
networks will be widely used within the next few years. There are many
satellite projects and theoretical studies being worked on. Many of them deal
with power consumption, orbit selection, inclination angle, etc. However, the
routing/switching of these communication paths over the satellite network is
a very important issue which will result in higher utilization and less
congestion on the satellite networks. In this work we designed a LEO
network routing protocol that will find a more reasonable path for a packet
on the network using Min Flow Max Residual (MFMR) path in a boundary called
Routing Set (RS). The network is modeled as a finite state automaton. The
satellite network has a finite number of states that are countable and nodes
are assumed to be stable during a state. The routing information is relative
to the satellite position. The proposed network and protocol
are modeled using the OPNET Modeler. The nodes are capable to discover their
surrounding nodes and their links. They are aware of the network architecture
and the flows on each link. The routing of the packets or the path selection
for a circuit is done by choosing the min flows and then max residual
capacity on the candidate paths. As a result of the project, max flows on the
links and the packet delays are measured and reported for different
scenarios. 1. Kaan Bur and Cem Ersoy, "Quality-of-Service-Based Multicast Routing in Heterogeneous Networks with Ad Hoc Extensions," submitted to IEEE Communications Magazine, under review
Abstract - The growing popularity of video, voice and data communications over the Internet and the rapid penetration of mobile telephony have stimulated a change in consumers’ expectations. Novel wireless networking technologies embedded into portable computing devices enable an ever-growing number of users to communicate with each other while on the move. Thus, the number of wireless users, group-oriented services and multimedia applications are increasing. Mobile ad hoc networks can provide users with the necessary features. However, the increasing amount of multimedia content shared over the wireless communication medium makes quality of service (QoS)-related, resource-efficient routing strategies a fundamental requirement for ad hoc networks. Moreover, the growing number of group-oriented applications necessitates the efficient utilization of network resources. The multicast communication model is a promising technique which can achieve this efficiency by facilitating the inherent broadcast capability of the wireless medium. However, it is not easy to integrate QoS mechanisms into a multicast routing protocol. This article presents the ad hoc QoS multicast (AQM) routing protocol, which achieves multicast efficiency by tracking the availability of resources for each node within its neighbourhood. The QoS status is monitored continuously and announced periodically to the extent of QoS provision. Any protocol is destined to fail in the real world if it is developed as a stand-alone routing mechanism but not designed to operate and survive in the heterogeneous network of the near future, which will probably consist of fixed, infrastructured wireless and mobile ad hoc components. As far as multicast sessions are concerned, the goal is to provide a seamless service whereby a single multicast group can span all these components, which requires the design of a gateway between the ad hoc and the wired networks.
2. Kaan Bur and Cem Ersoy, "Quality-of-Service-Aware Multicast Routing with Tree-to-Mesh Evolution for Mobile Ad Hoc Networks," submitted to IEEE/ACM Transactions on Networking, under review Abstract - The tremendous amount of multimedia applications running across the wireless communication medium makes quality of service (QoS) a fundamental requirement for ad hoc networks. On the other hand, the growing number of group-oriented applications also necessitates the efficient utilization of network resources. The multicast model is a promising technique which can achieve this efficiency by facilitating the inherent broadcast capability of the wireless medium. However, it is not easy to incorporate QoS into multicast in ad hoc networks. The ad hoc QoS multicast (AQM) routing protocol is developed to address this problem. AQM achieves multicast efficiency by tracking the availability of resources for each node within its neighbourhood. The QoS status is monitored continuously and announced periodically to the extent of QoS provision. Using these features, AQM nodes can make their decisions on joining a new multicast session based on the sustainability of their perceived QoS. AQM also evolves the initial multicast tree into a mesh during the course of an ongoing session to achieve a more robust network topology. Thus, AQM integrates the concept of QoS-awareness into multicast routing in mobile ad hoc networks. Since the nature of ad hoc networks requires that the control overhead of any routing protocol be as little as possible, an analysis of the tree-to-mesh evolution process of AQM and its impact on the system control overhead is provided. The performance of AQM is evaluated using various qualitative criteria as well as the results of the overhead analysis. Simulation results show that AQM improves multicast efficiency significantly through its QoS-aware admission and routing decisions with an acceptable overhead. It can be concluded that QoS is not only essential for, but also applicable to mobile ad hoc networks.
3. Muharrem Gün, Rabun Koşar, and Cem Ersoy , "Lifetime Optimization Using Variable Battery Capacities in Wireless Sensor Networks," Submitted to European Wireless 2007 Conference,
Abstract - In wireless sensor networks, energy consumptions of nodes are nonuniform throughout the network. As a result of this nonuniformity, having early deaths among highly loaded nodes is a common phenomenon which makes impossible to use the full capacity of the network. In this paper, we propose to deploy sensors with heterogeneous energy capacities in order to counterbalance the nonuniform energy drainage pattern, thus achieving a longer sensor network lifetime. We divide the monitored region into concentric ring areas and deploy nodes in these areas such that nodes with the highest battery capacity are located in the ring where the highest energy drainage takes place. Results show that up to 6 to 7 times longer lifetimes are attained without any increase in costs with this approach.
4. Atay Ozgovde and Cem Ersoy , "WCOT: A Utility Based Lifetime Metric for Wireless Sensor Networks," 18th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC) , September, 3-7, 2007, Athens, Greece
Abstract - One important measure for the effectiveness of any routing or deployment scheme in Wireless Sensor Networks (WSNs) is the network lifetime. Defining the lifetime of a sensor network is not a straight forward task since many aspects specific to the scenario at hand should be taken into consideration. In this paper, a generally applicable method with customizable parameters for computing the lifetime of a sensor network is proposed. Our method, WCOT (Weighted Cumulative Operational Time), maps the complete network behavior into a value which reflects the overall utility obtained from the WSN during its lifetime. A lifetime metric which ignores application dependence is bound to produce incorrect lifetime results. To show this, a series of simulations are run to compare the effectiveness of WCOT with the widely used lifetime metric time till the First Node Death (FND).
5. Suzan Bayhan, Gürkan Gür, Fatih Alagöz, "VoIP Performance in Multi-layered Satellite IP Networks with On-Board Processing Capability," accepted, IJCS (Wiley)
Abstract -
In this article, Voice over IP (VoIP)
performance in multi-layered satellite IP networks with on-board processing
(OBP) capability is investigated. With on-board processing, a satellite can
process the received data, and according to the nature of application, it
can decide on the transmission properties. After a brief overview of
relevant aspects of satellite networks to VoIP, VoIP performance for
Non-Geostationary Earth Orbit (NGEO) single layer and multi-layered
constellations are examined using a network simulation tool.
6. Ayşegül Tüysüz and Fatih Alagöz, "Satellite Mobility Pattern Scheme for Centrical and Seamless Handover Management in LEO Satellite Networks," JOURNAL OF COMMUNICATIONS AND NETWORKS (JCN), VOL. 8, NO. 4, DECEMBER 2006
Abstract -
One of the major problems with LEO satellites is their higher
speed relative to the terrestrial mobile terminals, which move at lower
speeds but at more random directions. This high mobility characteristic of
LEO satellites causes mobile users to hand over between footprints of
adjacent satellites very frequently. Therefore, handover management in LEO
satellite networks becomes a very challenging task for supporting global
mobile communication. The thesis discusses the basic handover management
schemes used in LEO satellite networks and points out their drawbacks. By
taking into consideration the inconvenience and incompleteness of the
current proposals in literature, this thesis proposes a new mobility
management scheme for LEO satellite communication networks.
7. M. Şükrü Kuran, Birkan Yılmaz, Fatih Alagöz, Tuna Tuğcu, "Quality of Service in Mesh Mode of IEEE 802.16 Networks," 14th International Conference on Software, Telecommunications and Computer Networks 2006, (SoftCOM '06), Split-Dubrovnik, Croatia, 2006.
Abstract - IEEE 802.16 standard supports two topologies: point-to-multipoint (PMP) and Mesh. In this paper, a QoS mechanism for the Mesh mode of IEEE 802.16 and a BS scheduler for the Mesh mode are proposed. Our QoS mechanism is developed by modifying the QoS mechanism of the PMP mode in IEEE 802.16. We compare our QoS mechanism against the default Mesh QoS mechanism of IEEE 802.16. The performances of both methods are analyzed by providing simulation results based on these two solutions. The results show that the default QoS mechanism introduces a delay of at least 100 ms, which makes it inappropriate for real time and multimedia services.
8. Suzan Bayhan, Gürkan Gür, Fatih Alagöz, "Adaptive Routing Protocol for QoS in Two-Layered Satellite IP Networks," 2nd International Workshop in Satellite and Space Communications (IWSSC06), September 14-15 2006, Madrid, Spain.
Abstract - Non-geostationary (NGEO) satellite networks can meet the requirements of next-generation internet services with high bit rates and much lower latency than geostationary (GEO) systems. However, various characteristics of these systems dissimilar from wired and GEO systems expose some challenges. Dynamic topology of the network and constraints on key system resources such as on-board CPU and memory are essential pointsto be considered for an efficient system design. In this paper,a novel adaptive routing mechanism in two-layered satellitenetwork considering the network’s real time information is introduced. Adaptive Routing Protocol for Quality of Service (ARPQ) utilizes on-board processing (OBP) and avoids congestion by distributing traffic load between MEO and LEO layers.We utilize a dynamic queueing policy to satisfy QoS requirements of delaysensitiveapplications while evading non real-time traffic suffer low performance level.
9. Suzan Bayhan, Gürkan Gür, Fatih Alagöz, "VoIP Performance on NGEO Satellite IP Networks with On-board Processing Capabilities," 7th IEEE International Symposium on Computer Networks (ISCN06), June 16-18 2006, İstanbul, Turkey. Abstract - In this study, Voice over IP (VoIP) performance in multi-layered satellite IP networks with on-board processing (OBP) capability is investigated. With on-board processing, a satellite can process the received data, and according to the nature of application, it can decide on the transmission properties. Specifically, considered OBP includes error-correcting coding to combat adverse channel conditions and priority queueing mechanisms for efficient use of the system resources. After a brief overview of relevant aspects of satellite networks to VoIP, VoIP performance for Non-Geostationary Earth Orbit (NGEO) single layer and multi-layered constellations are examined using a network simulation tool. The outcome of these simulations justifies the premise for the multi layered architecture for delay-sensitive and real-time traffic such as voice. Subsequently, the effects of some quality-of-service (QoS) mechanisms in multi-layered architecture are tested using various simulation parameters. The system simulation verifies that multi-layered satellite networks with OBP capabilities and QoS mechanisms are essential for feasibility of packet-based high quality voice services which are vital components of next-generation communications networks.
10. Kaan Bur and Cem Ersoy, "Ad Hoc Quality of Service Multicast Routing with Objection Queries for Admission Control," European Transactions on Telecommunications, (vol. 17, no. 5, pp. 561-576, September/October 2006).
Abstract - Today's handheld computing devices equipped with novel wireless network technologies can provide their users with features such as mobility, multimedia support and group communication. On the other hand, the administrative effort required to enable all these features increases beyond the level that an ordinary user can manage. Ad hoc networks, being able to quickly tilize themselves without user intervention, can overcome this problem. They are also suitable for group-oriented mobile multimedia communication. However, it is imperative for ad hoc networks to combine quality of service (QoS) and multicast routing strategies in order to tilize the wireless medium efficiently. This article defines the components of an ad hoc QoS multicast routing (AQM) protocol which addresses this issue. AQM achieves multicast routing efficiency by tracking the availability of resources for each node within its neighbourhood. Computation of free bandwidth is based on reservations made for ongoing sessions and the usage reported by neighbours. Current QoS status is announced at the initiation of a new session and updated periodically in the network to the extent of QoS provision. Thus, nodes are prevented from applying for membership if there is no QoS path for the session. When nodes wish to join a session with certain service requirements, a three-phase process consisting of request, reply and reserve steps ensures that the QoS information is updated and used to select the most appropriate routes. The allowed maximum hop count of the session is taken into account in order to satisfy the delay requirements of the multimedia applications. To cope with the continuous nature of streaming multimedia, AQM nodes check the availability of bandwidth within their neighbourhood not only for themselves but within a virtual tunnel of nodes. Objection queries are issued prior to reservation to avoid excessive resource usage due to allocations made by nodes which cannot detect each other directly. New performance metrics are introduced to evaluate the efficiency of AQM regarding the satisfaction level of individual members as well as the success rate of sessions. Simulation results show that, by applying novel QoS management techniques, AQM significantly improves multicast efficiency for members as well as for sessions.
11.
Kaan Bur, "Quality-of-Service-Aware
Multicast Routing for Multimedia Applications in Mobile Ad Hoc Networks," PhD.
Thesis Dissertation,
12.
Kaan Bur and Cem Ersoy,
"Ad Hoc Quality of Service Multicast Routing,"
Computer Communications, (vol. 29, no. 1, pp. 136-148,
December 2005).
Abstract - The
conceptual shift in expectations of wireless users from voice towards
multimedia, from availability towards acceptable quality, and from
stand-alone towards group-oriented computing has a significant impact on
today's networks in terms of the need for mobility, quality of service (QoS) and multicasting. Ad hoc networks, being independent
of any fixed infrastructure, can provide mobile users with these features, if
necessary QoS multicasting strategies are
developed. The aim of this article is to define the building blocks of such
an ad hoc QoS multicasting (AQM) protocol. AQM
achieves multicasting efficiency by tracking the availability of resources
for each node within its neighbourhood. Computation
of free bandwidth is based on reservations made for ongoing sessions and
similar information reported by neighbours. Current
QoS status is announced at the initiation of a new
session and updated periodically in the network to the extent of QoS provision. Thus, nodes are prevented from applying
for membership if there is no QoS path for the
session. When nodes join a session with certain service requirements, a
request-reply-reserve process ensures that the QoS
information is refreshed and used to select the most appropriate routes. To
evaluate the efficiency of AQM in providing multicast users with QoS and satisfying application requirements, two new
performance metrics, member and session satisfaction grades are introduced.
AQM is compared to a non-QoS scheme with particular
emphasis on these criteria. Simulation results show that, by applying QoS restrictions, AQM significantly improves multicasting
efficiency. Thus, QoS is both essential for and
applicable to multicasting in order to support mobile multimedia applications
in ad hoc networks.
13.
Kaan Bur and Cem Ersoy,
"Admission Control for Multicast Routing with
Quality of Service in Ad Hoc Networks," Springer Verlag Lecture Notes in Computer Science, to appear, compiled from the articles
presented at the 20th International Symposium on Computer and
Information Sciences (ISCIS),
Abstract - Ad
hoc networks, being able to organize themselves without user intervention,
can easily provide their users with mobility, multimedia support and group
communication. However, they have to combine quality of service (QoS) and multicast routing strategies. This article
defines the resource management and admission control components of the ad
hoc QoS multicast (AQM) routing protocol, which
achieves multicast efficiency along the network. When nodes wish to join a
session, a request-reply-reserve process ensures that an appropriate QoS route is selected. Nodes are prevented from applying
for membership if there is no QoS path for the
session. To cope with the continuous nature of multimedia, AQM nodes check
the availability of bandwidth in a virtual tunnel of nodes. Objection queries
are issued prior to admission in order to avoid excessive resource usage by
the nodes which cannot detect each other. New performance metrics are
introduced to evaluate AQM�s member and session
satisfaction rates. Simulation results show that AQM improves multicast
efficiency both for members and sessions.
14.
Kaan Bur and Cem Ersoy,
"Multicast Routing for Ad Hoc
Networks with a Multiclass Scheme for Quality of
Service," C. Aykanat, T. Dayar, I. Korpeoglu (eds.),
Springer Verlag Lecture Notes in Computer Science,
No. 3280, pp. 187-197, October 2004, compiled from the articles presented at
the 19th International Symposium on Computer and Information
Sciences (ISCIS), Antalya, Turkey, October 27-29,
2004. Abstract - As
multimedia- and group-oriented computing becomes increasingly popular for the
users of wireless mobile networks, the importance of features like quality of
service (QoS) and multicasting support grows. Ad
hoc networks can provide users with the mobility they demand, if efficient QoS multicasting strategies are developed. The ad hoc QoS multicasting (AQM) protocol achieves multicasting
efficiency by tracking resource availability within a node�s neighbourhood and announces it at session initiation.
When nodes join a session of a certain QoS class,
this information is updated and used to select the most appropriate routes.
AQM is compared to a non-QoS scheme with emphasis
on service satisfaction of members and sessions in an environment with
multiple service classes. By applying QoS
restrictions, AQM improves the multicasting efficiency for members and
sessions. The results show that QoS is essential
for and applicable to multicast routing in ad hoc networks.
15.
Kaan Bur and Cem Ersoy,
"Multicast Routing For Ad Hoc
Networks With A Quality Of Service Scheme For Session Efficiency,"
Proceedings of the 15th IEEE International Symposium on Personal, Indoor and
Mobile Radio
Communications (PIMRC), Barcelona , Spain ,
September 5-8, 2004. Abstract - The
conceptual shift in expectations of wireless users from voice towards
multimedia, from availability towards acceptable quality, and from
stand-alone towards group-oriented computing has a big impact on the needs of
today's networks in terms of mobility, quality of service (QoS) support, and multicasting. Ad hoc networks can
provide users with these features. However, it is necessary to develop QoS multicasting strategies for them. This paper defines
the building blocks of an ad hoc QoS multicasting
(AQM) protocol, which achieves multicasting efficiency by tracking resource
availability in a node's neighbourhood based on
previous reservations, and announces the QoS
conditions at session initiation. When nodes join a session with certain QoS requirements, this information is used to select the
most appropriate routes. AQM is compared to a non-QoS
scheme with emphasis on service satisfaction for sessions. By applying QoS restrictions, AQM improves the multicasting session efficiency.
The results show that QoS is essential for and
applicable to ad hoc networks.
16.
Kaan Bur and Cem Ersoy,
"Multicast Routing for Ad Hoc
Networks with Overload Prevention for Group Members," Proceedings
of the 13th IST Mobile and Wireless Communications Abstract - Mobility,
quality of service (QoS) support, and multicast
routing capability are important requirements for today�s networks. This is a
result of the changes in wireless users� expectations, which favour group-oriented, high-quality, multimedia
communication. Ad hoc networks enhanced with QoS
multicasting strategies can provide users with these features. This paper
defines the building blocks of an ad hoc QoS
multicasting (AQM) protocol, which tracks the availability of resources
within a node's neighbourhood based on reservations
made previously, and announces it at session initiation. When nodes join a
session with certain QoS requirements, this
information is updated and used to select the most appropriate routes. AQM is
compared to a non-QoS scheme with particular
emphasis on preventing overload on multicast group members. It achieves
better results through the use of its QoS-related
routing decisions, which suggests that QoS is both
essential for and applicable to multicast applications in ad hoc networks.
17.
E. Ilker Oyman
and Cem Ersoy, "Overhead Energy Considerations for Efficient Routing in
Wireless Sensor Networks," Computer Networks, Vol. 46, No. 4,
pp. 465-478, November 2004. Abstract - Energy
is the most critical resource in the life of a wireless sensor node.
Therefore, its usage must be optimized to maximize the network life. It is
known that for higher path loss exponent values, utilizing shorter
communication links reduces the transmitter energy, whenever the radio
equipment has power adjustment capability. Although the transmitter energy is
one of the major factors of total energy dissipation, neglecting the overhead
energy could result in suboptimal energy usage. Routing algorithms should
also be concerned about the overhead energy which is wasted at each hop of
data transfer. In this paper, we investigate the use of multi hop
communication links and compare the amount of energy gain upon alternative
routes using analytical techniques. We show that employing multi hop links
does not always result in energy gain, and try to quantify situations when it
is advantageous. The analytical results are used in routing decisions and
their effect in energy efficiency is validated using simulations. Moreover,
we also quantify the gain achieved in terms of lifetime by considering
overhead energy on power adjustable sensors for different environmental
conditions. We show that the network lifetime can dramatically decrease, if
the overhead energy component is neglected during routing decisions.
18.
E. Ilker Oyman
and Cem Ersoy, "The Effect of Overhead Energy Considerations to the Network
Lifetime in Wireless Sensor Networks," Proceedings of the 13th
IST Mobile and Wireless Communications Abstract - Although
the transmitter energy is one of the major factors of total energy
dissipation in a sensor node, neglecting the overhead energy in energy aware
routing decisions could result in suboptimal energy usage. Routing algorithms
should be concerned about the overhead energy which is wasted at each hop of
data transfer. When only the transmission energy is considered as the
communication cost, using shorter multi hop links seems to be more
advantageous. However, due to other energy consuming activities on the sensor
nodes, such as reception of relayed messages, sensing and computation tasks,
a considerable overhead energy might be dissipated while forwarding a
message. Therefore, multi hopping becomes not always advantageous in wireless
sensor networks. In this work, we investigate the use of multi hop
communication links and compare the amount of energy gain acquired by correct
routing energy calculations. We show that neglecting the overhead energy and
overemphasizing the importance of power adjustable transmitter circuitry
could result in considerable energy loss.
19.
E. Ilker Oyman
and Cem Ersoy, "Multiple Sink Network Design Problem in Large Scale Wireless
Sensor Networks," Proceedings of the IEEE International
Conference on Communications (ICC), Abstract - The
battery resource of the sensor nodes should be managed efficiently, in order
to prolong network lifetime in wireless sensor networks. Moreover, in large
scale networks with a large number of sensor nodes, multiple sink nodes
should be deployed, not only to increase the manageability of the network,
but also to reduce the energy dissipation at each node. In this paper, we
focus on the multiple sink location problems in large scale wireless sensor
networks. Different problems depending on the design criteria are presented.
We consider locating sink nodes to the sensor environment, where we are given
a time constraint that states the minimum required operational time for the
sensor network. We use simulation techniques to evaluate the quality of our
solution.
20. E. Ilker Oyman, "Multiple
Sink Network Design Problem in Large Scale Wireless Sensor Networks,"
PhD.
Thesis Dissertation,
21.
Roy Kucukates and Cem Ersoy, "High
Performance Routing in a LEO Satellite Network," Proceedings of
the 8th IEEE Symposium on Computers and Communications (ISCC), Antalya, Turkey, June 30 - July 3, 2003. Abstract - Satellite systems are designed as a
backup system to the existing land based wireless systems. Because of the
global coverage of the system it becomes more economic for the rural areas
where there is no wired infrastructure of communication. Besides being more
economic to the rural areas the satellite networks are not affected by the
natural disasters and continue to give the service in such situations. In
this research a routing method in a routing set concept is investigated. The
system tries to minimize the maximum flow over a given set of shortest paths
from the source to destination and aims to leave additional capacity over the
inter-satellite links to be able to utilize better the limited capacity and,
also, to avoid the congestion.
22.
Roy Kucukates, "A Minimum Flow Maximum Residual
Method for Routing in a LEO Satellite Network," PhD. Thesis
Dissertation, 1.
CmpE 523 -
Performance Evaluation of Computer Networks (Formerly CmpE 580 Computer Networks I)
(A course offered by NETLAB) Introduction for computer
networks performance evaluation. Modeling of traffic flows. Delay and loss
models for computer networks. Networks of queues. Performance evaluation of
multiple access methods and local area networks. Measurement and simulation
of computer networks. Instructor: Cem Ersoy, ersoy@boun.edu.tr, http://www.cmpe.boun.edu.tr/~ersoy
Course home page:
http://netlab.boun.edu.tr/courses/cmpe523/fall2006/index.html
2.
CmpE 524 -
Computer Network Design (Formerly CmpE 582 Computer Networks
II) (A course offered by NETLAB) Principles of computer networks
design, network design algorithms, centralized network design. Application of
minimum spanning tree and shortest path algorithms to problems in network
design. Static and dynamic routing algorithms. Network reliability analysis.
Linear and integer programming techniques. Heuristics, evolutionary
algorithms. Distributed network design. Case studies: Multimedia network
design, multihop lightwave
network design, cellular network design, satellite network design, ad hoc
network design problems. Instructor: Cem Ersoy, ersoy@boun.edu.tr, http://www.cmpe.boun.edu.tr/~ersoy
Course home page: http://netlab.boun.edu.tr/courses/cmpe524/fall2007/index.html
3.
CmpE
470 -
Computer Performance Evaluation
(A course offered by
NETLAB)
Systematic approach to
computer performance evaluation. Measurement techniques and tools.
Instructor:
Cem Ersoy, ersoy@boun.edu.tr,
http://www.cmpe.boun.edu.tr/~ersoy
Course home page: http://orkinos.cmpe.boun.edu.tr/netlab/courses/cmpe470/fall2007/ NETLAB,
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