@conference {
	title = {A Multiple Subset Sum Formulation for Feedback Implosion Suppression over Satellite Networks},
	author = {Akkor, Gun., Baras, John S., Hadjitheodosiou, Michael.},
	year = {2005},
	month = {11/2005},
	abstract = {In this paper, we present a feedback implosion suppression (FIS) algorithm that reduces the volume of feedback information transmitted through the network without relying on any collaboration between users, or on any infrastructure other than the satellite network. Next generation satellite systems that utilize the Ka frequency band are likely to rely on various fade mitigation techniques, in order to guarantee a service quality that is comparable to other broadband technologies. User feedback would be a valuable input for a number of such components, however, collecting periodic feedback from a large number of users would result in the well-known feedback implosion problem. Feedback implosion is identified as a major problem when a large number of users try to transmit their feedback messages through the network, holding up a significant portion of the uplink resources and clogging the shared uplink medium. In this paper, we look at a system where uplink channel access is organized in time-slots. The goal of the FIS algorithm is to reduce the number of uplink time-slots hold up for the purpose of feedback transmission. Our analysis show that the FIS algorithm effectively suppresses the feedback messages of 95\% of all active users, but still achieves acceptable performance results when the ratio of available time-slots to number of users is equal to or higher than 5\%.},
	address = {St. Louis, MO},
	booktitle = {Globecom 2005 Wireless Communications},
	pages = {pp. 3226-3230}
}
@conference {
	title = {Integrated Packet Level FEC Coding for Bulk Data Transfer Over Satellite Network},
	author = {Akkor, Gun., Baras, John S., Hadjitheodosiou, Michael.},
	year = {2005},
	month = {09/2005},
	abstract = {Packet level forward error correction (FEC) coding has been widely accepted as an efficient way of reducing the number of retransmissions and recovering from packet losses for reliable multicast in satellite networks. While there has been a significant effort in defining packet level FEC schemes that detail the structure, organization and delivery of the encoding packets, little attention has been given to how the physical channel, channel coding, and the downlink power budget affect the design space of these schemes in the context of a satellite network architecture. In this paper, we take a step in this direction, and define the points of interaction between various components and build a simulation environment. Using this simulation setup, we provide design suggestions for integrating FEC coding into reliable multicast transport protocols.},
	address = {Rome, Italy},
	booktitle = {23rd AIAA International Communications Satellite Systems Conference and Exhibit (ICSSC)}
}
@conference {
	title = {An Optimization-based Approach to Flow~Control and Resource Allocation Problem in Satellite Communication Systems},
	author = {Akkor, Gun., Baras, John S., Hadjitheodosiou, Michael.},
	year = {2004},
	month = {05/2004},
	abstract = {We propose an approach to optimize resource sharing and flow control in a multi-beam broadband satellite system that supports both unicast and multicast flows. We show that, in this architecture, the load on every spot-beam queue could be different, depending on the type of the flows and the distribution of the receivers across spot-beam coverage areas. This load imbalance may significantly under-utilized the system resources and decrease the system throughput when both unicast and multicast flows are active in the system. In this paper, we formulate an optimization problem for Intra- and inter-beam resource sharing such that the variance of the session rates experienced by users of a flow located in different beam coverage areas is minimized. The result of our resource allocation also determines the maximum sustainable rate of each flow. We present results that compare the beam utilization and maximum sustainable sessions rates with and without optimization. We conclude that this method improves the average session rates up to 40\% and average utilization of the system up to 15\% when both unicast and multicast flows are active.},
	address = {Monterey, California},
	booktitle = {22nd AIAA International Communication Satellite Systems Conference \&amp; Exhibit 2004, (ICSSC)}
}
@conference {
	title = {A Reliable Multicast Transport Protocol with Feedback Implosion Suppression for Satellite Communication Systems},
	author = {Akkor, Gun., Baras, John S.},
	year = {2004},
	month = {03/2004},
	abstract = {In this paper, we propose a reliable multicast transport protocol for satellite communication systems. Many of the emerging applications in the Internet would benefit from reliable multicast services, and broadband satellite communication systems have attractive characteristics for supporting such services. However, many of the protocols designed primarily for terrestrial networks do not perform well over satellite networks. Therefore, it is necessary to look at the problem of reliable multicast in the solution space of satellite communications. Our protocol makes use of a special form of forward error correcting codes and couples it with an adaptive window based control mechanism to dynamically adjust the number of encoding packets forwarded to the users. Protocol makes very good use of the broadcast nature of the satellite channel and attempts to minimize the feedback volume by a novel feedback implosion suppression algorithm. We evaluate the protocol performance by computer simulations.},
	address = {Princeton, New Jersey},
	booktitle = {38th Annual Conference on Information Sciences and Systems (CISS 2004)},
	pages = {pp. 1-6}
}
@conference {
	title = {A Feedback Implosion Suppression Algorithm for Satellite Reliable Multicast},
	author = {Akkor, Gun., Baras, John S., Hadjitheodosiou, Michael.},
	year = {2003},
	month = {12/2003},
	abstract = {In this paper, we propose a knapsack-based feedback suppression algorithm for reliable multicast transport protocols operating over a satellite network. A reliable transport protocol needs to identify the packets which failed to reach a given destination. This is achieved through feedback packets returned to the source. For multicast services, receive feedback has been shown to lead to the feedback implosion problem. Feedback implosion is a well-studied problem and various solutions exist in the literature. However, these solutions mainly focus on wireline terrestrial networks and do not take into account the inherent characteristics of the satellite channel and the architecture of the deployed network. Therefore, we need to revisit the problem and provide a new set of solutions for efficient integration to next-generation satellite systems. In this paper, we introduce a feedback implosion suppression algorithm, which effectively suppresses the amount of feedback relayed through the satellite channel, while ensuring that the critical information is conveyed in a timely fashion. The performance of the algorithm is evaluated through simulations.},
	address = {San Francisco, California},
	booktitle = {IEEE Globecom 2003},
	pages = {pp. 3765-3769}
}
@article {
	title = {Multicast-Aware Power Allocation in Multiple Spot-Beam Satellite Communication Systems},
	author = {Akkor, Gun., Hadjitheodosiou, Michael., Baras, John S.},
	year = {2006},
	month = {01/2006},
	abstract = {In this paper, we address the problem of user heterogeneity in satellite multicast from the perspective of resource allocation in a multiple spot-beam satellite system that supports both unicast and multicast flows. Satellite communication systems, with their wide-area coverage and direct access to a large number of users, clearly have an inherent advantage in supporting multicast applications. In order to remain competitive against other broadband technologies, however, next generation satellite systems will be required to support both unicast and multicast flows and offer optimal sharing of system resources between these flows. We show that user heterogeneity across spot-beam queues may result in lower allocated session rates for active flows, and be perceived as unsatisfactory by potential users when both unicast and multicast flows are active in the system. We propose an optimization-based approach that allocates resources with the goal of smoothing user heterogeneity and show that resulting session rates are higher on the average for both unicast and multicast flows. This is achieved through the re-distribution of system power among spot-beam queues, by taking into account the load on the queues and the channel states. We conclude that it is possible to increase the average session rates of multicast flows by 25{\textendash}100\%, and the rates of unicast flows by 15{\textendash}40\% compared to the pre-optimization levels.},
	pages = {pp. 49-71},
	volume = {Vol. 24},
	number = {Issue  1},
	journal = {International Journal of Satellite Communications}
}
@article {
	title = {Transport Protocols in Multicast via Satellite},
	author = {Akkor, Gun., Hadjitheodosiou, Michael., Baras, John S.},
	year = {2004},
	month = {11/2004},
	abstract = {In a wide variety of broadband applications, there is a need to distribute information to a potentially large number of receiver sites that are widely dispersed from each other. Communication satellites are a natural technology option and are extremely well suited for carrying such services because of the inherent broadcast capability of the satellite channel. Despite the potential of satellite multicast, there exists little support for multicast services over satellite networks. Although several multicast protocols have been proposed for use over the Internet, they are not optimized for satellite networks. One of the key multicast components that are affected when satellite networks are involved in the communication is the transport layer. In this paper, we attempt to provide an overview of the design space and the ways in which the network deployment and application requirements affect the solution space for transport layer schemes in a satellite environment. We also highlight some of the issues that are critical in the development of next generation satellite multicast services.},
	pages = {pp. 611-627},
	volume = {Vol. 22},
	number = {No. 6},
	journal = {International Journal of Satellite Communication}
}
@techreport {
	title = {Power Balancing in Multiple Spot-Beam Satellite Systems for Multicast Support},
	author = {Akkor, Gun., Hadjitheodosiou, Michael.},
	year = {2004},
	month = {01/2004},
	abstract = {We address the problem of optimizing resource sharing and flow control in a multiple spot-beam broadband satellite system that supports both unicast and multicast flows. Satellite communication systems, with their wide-area coverage and ubiquitous access to large number of users, clearly have an inherent advantage in supporting distributed applications that require concurrent transmission of content to multiple users. In order to remain competitive against other broadband technologies, next generation satellite systems will be required to support both unicast and multicast flows and offer optimal sharing of system resources between these flows. We show that a high load variation across the spot-beam queues may significantly under-utilize the system and be perceived unsatisfactory by potential users when both unicast and multicast flows are active in the system. We propose an optimization based-approach to balance the load in the system and conclude that it is possible to increase the average session rates of all active flows by up to 30\% after this optimization is applied.},
	number = {Number: CSHCN TR 2004-15}
}
@techreport {
	title = {A Multiple Subset Sum Formulation for Feedback Implosion Suppression over Satellite Networks},
	author = {Akkor, Gun., Hadjitheodosiou, Michael.},
	year = {2004},
	month = {01/2004},
	abstract = {In this paper, we present a feedback implosion suppression (FIS) algorithm that reduces the volume of feedback information transmitted through the network without relying on any collaboration between users, or on any infrastructure other than the satellite network. Next generation satellite systems that utilize the Ka frequency band are likely to rely on various fade mitigation (compensation) techniques ranging from adaptive coding to dynamic power control, in order to guarantee a service quality that is comparable to other broadband technologies. User feedback would be a valuable input for a number of such components, however, collecting periodic feedback from a large number of users would result in the well-known feedback implosion problem. Feedback implosion is identified as a major problem when a large number of users try to transmit their feedback messages through the network, holding up a significant portion of the uplink resources and clogging the shared uplink medium. In this paper, we look at a system where uplink channel access is organized in time-slots. The goal of the FIS algorithm is to reduce the number of uplink time-slots hold up for the purpose of feedback transmission. Our analysis show that the FIS algorithm effectively suppresses the feedback messages of 95\% of all active users, but still achieves acceptable performance results when the ratio of available time-slots to number of users is equal to or higher than 5\%.},
	number = {Number: CSHCN TR 2004-21}
}
@techreport {
	title = {Multicast-aware Power Allocation in Multiple Spot-Beam Satellite Communication Systems},
	author = {Akkor, Gun., Hadjitheodosiou, Michael.},
	year = {2004},
	month = {01/2004},
	abstract = {We address the problem of optimizing resource sharing and flow control in a multiple spot-beam broadband satellite system that supports both unicast and multicast flows. Satellite communication systems, with their wide-area coverage and direct access to large number of users, clearly have an inherent advantage in supporting multicast applications. In order to remain competitive against other broadband technologies, however, next generation satellite systems will be required to support both unicast and multicast flows and offer optimal sharing of system resources between these flows. We show that, in a multiple spot-beam system, a high load variation across spot-beam queues may force lower allocated session rates for active flows, and be perceived as unsatisfactory by potential users when both unicast and multicast flows are active in the system. We propose an optimization framework for balancing the spot-beam queue service rates such that the sum of the rate variances of all active multicast flows is minimized. This is achieved through the re-distribution of system power among spot-beam queues, by taking into account the load on the queues and the channel states. We conclude that it is possible to increase the average session rates of multicast flows by up to 16\%, and the rates of unicast flows by up to 4\% after this optimization is applied.},
	number = {Number: CSHCN TR 2004-19}
}
@techreport {
	title = {Load balancing in multi-beam satellite systems},
	author = {Akkor, Gun., Hadjitheodosiou, Michael.},
	year = {2004},
	month = {01/2004},
	abstract = {We propose an approach to optimize resource sharing and in a multi-beam broadband satellite system that supports both unicast and multicast flows. We show that in this architecture, the load on every spot-beam queue could be different, depending on the type of the flows and the distribution of the receivers across spot-beam coverage areas. This load unbalance may significantly under-utilize the system resources and decrease the system throughput when both unicast and multicast flows are active in the system. In this paper, we formulate an optimization problem for intra- and inter-beam resource sharing such that the variance of the session rates experienced by users of a flow located in different beam coverage areas is minimized. The result of our resource allocation also determines the maximum sustainable rate of each flow. We calculate the beam utilization and maximum sustainable sessions rates with and without optimization and compare the results. We conclude that this method significantly improves the session rates and overall utilization of the system when both unicast and multicast flows are active.},
	number = {Number: CSHCN TR 2004-9}
}
@techreport {
	title = {A Reliable Multicast Transport Protocol for Satellite Communication Systems},
	author = {Akkor, Gun., Hadjitheodosiou, Michael.},
	year = {2003},
	month = {01/2003},
	abstract = {In this paper, we propose a reliable multicast transport protocol for satellite communication systems. Many of the emerging applications in the Internet would benefit from reliable multicast services, and broadband satellite communication systems have attractive characteristics for supporting such services. However, many of the protocols designed primarily for terrestrial networks do not perform well over satellite networks. Therefore, it is necessary to look at the problem of reliable multicast in the solution space of satellite communications. Our protocol makes use of a special form of forward error correcting codes and couples it with an adaptive window based control mechanism to dynamically adjust the number of encoding packets forwarded to the users. Protocol makes very good use of the broadcast nature of the satellite channel and attempts to minimize the feedback from users. We evaluate the protocol performance by extensive computer simulations.},
	number = {Number: CSHCN TR 2003-17}
}
@techreport {
	title = {A Feedback Implosion Suppression Algorithm for Satellite Reliable Multicast},
	author = {Akkor, Gun., Hadjitheodosiou, Michael.},
	year = {2003},
	month = {01/2003},
	abstract = {In this paper, we propose a knapsack-based feedback suppressionalgorithm for reliable multicast transport protocols operating over asatellite network. A reliable transport protocol needs to identify thepackets which failed to reach a given destination. This is achievedthrough feedback packets returned to the source. For multicastservices, receiver feedback has been shown to lead to thefeedback implosion problem. Feedback implosion is awell-studied problem and various solutions exist in the literature.However, these solutions mainly focus on wireline terrestrial networksand do not take into account the inherent characteristics of thesatellite channel and the architecture of the deployed network.Therefore, we need to revisit the problem and provide a new set ofsolutions for efficient integration to next generation satellitesystems. In this paper, we introduce a feedback implosion suppressionalgorithm, which effectively suppresses the amount of feedback relayedthrough the satellite channel, while ensuring that the criticalinformation is conveyed in a timely fashion. The performance of thealgorithm is evaluated through simulations.},
	number = {Number: CSHCN TR 2003-3}
}
@techreport {
	title = {IP Multicast via Satellite: A Survey},
	author = {Akkor, Gun., Hadjitheodosiou, Michael.},
	year = {2002},
	month = {01/2002},
	abstract = {Many of the emerging applications in the Internet, such astele-conferencing, distance-learning, distributed games, softwareupdates, and distributed computing would benefit from multicastservices. In many of these applications, there is a need todistribute information to many sites that are widely dispersed fromeach other. Communication satellites are a natural technology optionand are extremely well suited for carrying such services. Despite thepotential of satellite multicast, there exists little support forsatellite IP multicast services. Both Internet Engineering andInternet Research Task Forces (IETF and IRTF) have been involved in aresearch effort to identify the design space for a general purposereliable multicast protocol and standardize certain protocolcomponents as building blocks. However, for satellite multicastservices, several of these components have a different designspace. In this paper, we attempt to provide an overview of the designspace and the ways in which the network deployment and applicationrequirements affect the solution space. We maintain a similartaxonomy to that of the IETF efforts, and identify which keycomponents of a general multicast protocol are affected by two of themost common satellite network deployment scenarios. We also highlightsome of the issues which we think are critical in the development ofnext generation satellite IP multicast services.},
	number = {Number: CSHCN TR 2002-35}
}
