Samrat Ganguly - Academia.edu (original) (raw)
Papers by Samrat Ganguly
Lecture Notes in Computer Science, 2005
The notion of service overlay network (SON) was proposed recently to alleviate difficulties encou... more The notion of service overlay network (SON) was proposed recently to alleviate difficulties encountered in providing end-to-end quality of service guarantees in the current Internet architecture. The main problem is that end-to-end traffic often traverses through multiple autonomous systems (AS) that do not have any multilateral service level agreement (SLA) for traffic from other domains. The SONs are able to provide QoS guarantees by purchasing bandwidth from individual network domains and building a logical end-to-end data delivery infrastructure on top of existing Internet. In this paper, we consider a generalized framework for SON categorized based on three different characteristic features: a) single-homed versus multi-homed b)usage-based versus leased cost model and c) capacitated versus uncapacitated network. We focus on the algorithmic analysis of the topology design problem for the above generalized SON. We prove that for certain cases polynomial time optimal algorithm exists while for other cases, the topology design problem is NP-complete. For the NP-complete cases, we provide approximate solutions. Experimental evaluation demonstrates that our approximate solutions produce reasonable quality solution in most of the instances in a fraction of time needed to find the optimal solution. overlay network is an outcomes of the recent studies on overlay networks such as Detour [13], resilient overlay network [2] and internet indirection infrastructure . These studies shows that end-to-end performance can be significantly improved by utilizing alternate path created over a overlay network. Further studies in shows that when compared with the ideal routing, network-level routing often yields suboptimal user performance due to routing hierarchy and BGP policy routing. Further empirical studies reported in shows that 50% of the bottlenecks are at the intra-ISP links.
IEEE INFOCOM 2003. Twenty-second Annual Joint Conference of the IEEE Computer and Communications Societies (IEEE Cat. No.03CH37428), 2003
... Optical networking has become a key technology in accommodating the rapidly expanding Interne... more ... Optical networking has become a key technology in accommodating the rapidly expanding Internet traffic. ... We define the cost of routing in hierarchical optical network as the total cost of the ports (both OEO and OOO ones) required for routing the traffic flows. ...
2005 IEEE 61st Vehicular Technology Conference, 2005
The IEEE 802.16 WiMax standard provides a mechanism for creating multi-hop mesh, which can be dep... more The IEEE 802.16 WiMax standard provides a mechanism for creating multi-hop mesh, which can be deployed as a high speed wide-area wireless network. To realize the full potential of such high-speed IEEE 802.16 mesh networks, two efficient wireless radio resource allocation extensions were developed. The objective of this paper is to propose an efficient approach for increasing the utilization of WiMax mesh through appropriate design of multi-hop routing and scheduling. As multiple-access interference is a major limiting factor for wireless communication systems, we adopt here an interference-aware cross-layer design to increase the throughput of the wireless mesh network. In particular, our scheme creates a tree-based routing framework, which along with scheduling is interference aware and results in a much higher spectral efficiency. Performance evaluation results show that the proposed interference-aware scheme achieves significant throughput enhancement over the basic IEEE 802.16 mesh network.
Lecture Notes in Computer Science, 2005
Empirical studies report frequent occurrences of path failure in the Internet. In providing resil... more Empirical studies report frequent occurrences of path failure in the Internet. In providing resilience to such failures, we propose the computation of alternate backup end-to-end path that is disjoint to the default IP path. This disjoint path is created using transit hubs that can be located at diverse points in the Internet. Transit hubs provide better utilization of network resources. Assuming an IP layer routing between any two nodes, we show that the problem of computing such a disjoint path is NP-complete. We present an exact and a heuristic solution for the problem. Using routing data obtained from PlanetLab, we evaluate the efficacy of our heuristic solution.
2007 IEEE International Conference on Communications, 2007
... The channel assignment heuristic invokes two functions namely, MIS channel assignment and ens... more ... The channel assignment heuristic invokes two functions namely, MIS channel assignment and ensure connectivity. ... The objective of MIS channel assignment is to assign channels such that the number of links that can be activated simultaneously is maximized. ...
2010 8th International Conference on Communications, 2010
ABSTRACT The capacity of wireless mesh networks can be enhanced with judicious channel assignment... more ABSTRACT The capacity of wireless mesh networks can be enhanced with judicious channel assignment. This paper deals with one particular type of mesh network topology - the tree topology. The unique characteristics of this topology is that all the traffic to/from the mesh nodes goes through the root. This enables design of an efficient channel allocation algorithm that utilizes the intrinsic characteristics of the tree topology and the traffic pattern over this topology. We use the unique connection characteristics of the tree topology to create an auxiliary contention graph over which we execute our coloring algorithm. This mitigates the burden of ensuring connectivity that channel allocation algorithms for mesh have to consider and the algorithm can solely focus on the task of capacity maximization. Our algorithm has a low complexity of O(N2) for a mesh network with N nodes.
Lecture Notes in Computer Science, 2006
Traditional network file systems, like NFS, do not extend to wide-area due to low bandwidth, high... more Traditional network file systems, like NFS, do not extend to wide-area due to low bandwidth, high network latency, and dynamism introduced in the WAN environment. Metadata access latency is a significant performance problem for Wide Area File Systems, since metadata requests constitute a large portion of all file system requests, are synchronous, and cannot be cached at clients.
Proceedings of the 15th international conference on World Wide Web - WWW '06, 2006
Current web search engines are retrospective in that they limit users to searches against already... more Current web search engines are retrospective in that they limit users to searches against already existing pages. Prospective search engines, on the other hand, allow users to upload queries that will be applied to newly discovered pages in the future. Some examples of prospective search are the subscription features in Google News and in RSS-based blog search engines.
2nd European Conference on Universal Multiservice Networks. ECUMN'2001 (Cat. No.02EX563), 2002
Abstract Many ISPs use MPLS for traffic engineering to account for and utilize their resources pr... more Abstract Many ISPs use MPLS for traffic engineering to account for and utilize their resources properly. A fundamental problem in MPLS is to reduce the label space usage by label switched paths (LSPs), while meeting the flow requirements. While routing ...
Fifth Annual IEEE International Conference on Pervasive Computing and Communications Workshops (PerComW'07), 2007
IEEE 60th Vehicular Technology Conference, 2004. VTC2004-Fall. 2004, 2004
Poor coverage is a major concern in cellular networks; it is also an inherent problem in HSDPA/HD... more Poor coverage is a major concern in cellular networks; it is also an inherent problem in HSDPA/HDR-based third generation (3G) wireless downlink data access. Poor coverage lowers the overall utilization of the cell and results in locationdependent downlink throughput for mobile users. In this paper, we investigate issues related to the design and application of an adhoc relay network (ARN) capable of relaying data from 3G base station to mobile users and provide a more uniform downlink data access. In order to exploit the benefits of ARN, we propose the AdhoCell architecture based on a self-organized ARN. The architecture is flexible in terms of deployment and is easy to integrate with current 3G architectures. These features are based on the ARN design and route computation scheme that we present in this paper. To utilize the ARN in the most efficient manner, we propose a two-level scheduling strategy, where the base station and some of the ARN nodes participate. Simulation results show the performance of the proposed ARN scheme significantly improve the HSDPA system
2004 IEEE International Conference on Communications (IEEE Cat. No.04CH37577), 2004
In this paper, we propose enhancements to radio link protocols by identifying decisive frames and... more In this paper, we propose enhancements to radio link protocols by identifying decisive frames and categorizing them as crucial and non-crucial. The fact that initial frames from the same upper layer segment can afford a few trials of retransmissions and the later frames cannot, motivates our work. We treat the frames differentially with respect to FEC coding and ARQ schemes. We consider specific cases of FEC and ARQ strategies and qualitatively show how the differential treatment of frames can improve the performance of the RLP.
IEEE INFOCOM, 2006
Voice trafc on the Internet (VoIP) is poised to grow rapidly but the Internet is not engineered f... more Voice trafc on the Internet (VoIP) is poised to grow rapidly but the Internet is not engineered for such delay- sensitive applications. We show how the end-user quality of many VoIP calls can be improved by rerouting them in an intermediate overlay network and thought the use of various path-diversity and error-coding techniques. We present an overlay network (OverPhone) that
ACM SIGMETRICS Performance Evaluation Review, 2006
... Sudeept Bhatnagar, Samrat Ganguly, Rauf Izmailov NEC Laboratories, Princeton, NJ 08540, USA {... more ... Sudeept Bhatnagar, Samrat Ganguly, Rauf Izmailov NEC Laboratories, Princeton, NJ 08540, USA {sudeept,samrat,rauf}@nec-labs.com ... 1. INTRODUCTION We present Π-Stream, a system which enables fast real-time media-streaming that allows clients to take advantage of ...
Journal of tropical pediatrics, 2014
We report a 12-year-old girl presenting with acute disseminated encephalomyelitis (ADEM) along wi... more We report a 12-year-old girl presenting with acute disseminated encephalomyelitis (ADEM) along with hypertensive emergency. Hypertension persisted for few weeks following recovery and subsided with oral clonidine. Although autonomic instability in ADEM has been reported before, hypertensive emergency was not previously documented as presenting feature of ADEM.
Proceedings of the 11th international symposium on Modeling, analysis and simulation of wireless and mobile systems - MSWiM '08, 2008
In this work, we address the issue of unrealistic simulations of wireless networks using a measur... more In this work, we address the issue of unrealistic simulations of wireless networks using a measurement-based approach. The idea is to use empirical modeling using measurement data as a mechanism to model physical layer behavior. We demonstrate the power of this approach for 802.11-based networks using ns2, a packet-level network simulator. Specifically, we develop two versions of the ns2 simulator that model the wireless physical layer with different levels of fidelity. In both versions, the deferral and reception model are built using measurements. For propagation modeling, one version uses direct measurements and the other uses an empirically derived model. In validation experiments with a 12-node mesh testbed, both these versions were found to be reasonably accurate (85 percentile errors within about 10% of the capacity) relative to regular simulations (85 percentile errors within 50% of capacity).
2008 International Symposium on a World of Wireless, Mobile and Multimedia Networks, 2008
... We thank Dr. Shamik Sengupta of Stevens Institute of Technology for broadly publicizing this ... more ... We thank Dr. Shamik Sengupta of Stevens Institute of Technology for broadly publicizing this workshop. ... We hope you'll enjoy the program. Mainak Chatterjee, University of Central Florida Samrat Ganguly, NEC Americas June 2008 xiv
Proceedings of the 13th annual ACM international conference on Mobile computing and networking - MobiCom '07, 2007
We present a practical, measurement-based model that captures the effect of interference in 802.1... more We present a practical, measurement-based model that captures the effect of interference in 802.11-based wireless LAN or mesh networks. The goal is to model capacity of any given link in the presence of any given number of interferers in a deployed network, carrying any specified amount of offered load. Central to our modeling approach is a MAC-layer model for 802.11 that is fed by PHY-layer models for deferral and packet capture behaviors, which in turn are profiled based on measurements. The target network to be evaluated needs only O(N ) measurement steps to gather metrics for individual links that seed the models. We provide two solution approaches -one based on direct simulation (slow, but accurate) and the other based on analytical methods (faster, but approximate). We present elaborate validation results for a 12 node 802.11b mesh network using upto 5 interfering transmissions. We demonstrate, using as comparison points three simpler modeling approaches, that the accuracy of our approach is much better, predicting link capacities with errors within 10% of the base channel datarate for about 90% of the cases.
Proceedings of the 1st international workshop on Wireless network testbeds, experimental evaluation & characterization - WiNTECH '06, 2006
Lecture Notes in Computer Science, 2005
The notion of service overlay network (SON) was proposed recently to alleviate difficulties encou... more The notion of service overlay network (SON) was proposed recently to alleviate difficulties encountered in providing end-to-end quality of service guarantees in the current Internet architecture. The main problem is that end-to-end traffic often traverses through multiple autonomous systems (AS) that do not have any multilateral service level agreement (SLA) for traffic from other domains. The SONs are able to provide QoS guarantees by purchasing bandwidth from individual network domains and building a logical end-to-end data delivery infrastructure on top of existing Internet. In this paper, we consider a generalized framework for SON categorized based on three different characteristic features: a) single-homed versus multi-homed b)usage-based versus leased cost model and c) capacitated versus uncapacitated network. We focus on the algorithmic analysis of the topology design problem for the above generalized SON. We prove that for certain cases polynomial time optimal algorithm exists while for other cases, the topology design problem is NP-complete. For the NP-complete cases, we provide approximate solutions. Experimental evaluation demonstrates that our approximate solutions produce reasonable quality solution in most of the instances in a fraction of time needed to find the optimal solution. overlay network is an outcomes of the recent studies on overlay networks such as Detour [13], resilient overlay network [2] and internet indirection infrastructure . These studies shows that end-to-end performance can be significantly improved by utilizing alternate path created over a overlay network. Further studies in shows that when compared with the ideal routing, network-level routing often yields suboptimal user performance due to routing hierarchy and BGP policy routing. Further empirical studies reported in shows that 50% of the bottlenecks are at the intra-ISP links.
IEEE INFOCOM 2003. Twenty-second Annual Joint Conference of the IEEE Computer and Communications Societies (IEEE Cat. No.03CH37428), 2003
... Optical networking has become a key technology in accommodating the rapidly expanding Interne... more ... Optical networking has become a key technology in accommodating the rapidly expanding Internet traffic. ... We define the cost of routing in hierarchical optical network as the total cost of the ports (both OEO and OOO ones) required for routing the traffic flows. ...
2005 IEEE 61st Vehicular Technology Conference, 2005
The IEEE 802.16 WiMax standard provides a mechanism for creating multi-hop mesh, which can be dep... more The IEEE 802.16 WiMax standard provides a mechanism for creating multi-hop mesh, which can be deployed as a high speed wide-area wireless network. To realize the full potential of such high-speed IEEE 802.16 mesh networks, two efficient wireless radio resource allocation extensions were developed. The objective of this paper is to propose an efficient approach for increasing the utilization of WiMax mesh through appropriate design of multi-hop routing and scheduling. As multiple-access interference is a major limiting factor for wireless communication systems, we adopt here an interference-aware cross-layer design to increase the throughput of the wireless mesh network. In particular, our scheme creates a tree-based routing framework, which along with scheduling is interference aware and results in a much higher spectral efficiency. Performance evaluation results show that the proposed interference-aware scheme achieves significant throughput enhancement over the basic IEEE 802.16 mesh network.
Lecture Notes in Computer Science, 2005
Empirical studies report frequent occurrences of path failure in the Internet. In providing resil... more Empirical studies report frequent occurrences of path failure in the Internet. In providing resilience to such failures, we propose the computation of alternate backup end-to-end path that is disjoint to the default IP path. This disjoint path is created using transit hubs that can be located at diverse points in the Internet. Transit hubs provide better utilization of network resources. Assuming an IP layer routing between any two nodes, we show that the problem of computing such a disjoint path is NP-complete. We present an exact and a heuristic solution for the problem. Using routing data obtained from PlanetLab, we evaluate the efficacy of our heuristic solution.
2007 IEEE International Conference on Communications, 2007
... The channel assignment heuristic invokes two functions namely, MIS channel assignment and ens... more ... The channel assignment heuristic invokes two functions namely, MIS channel assignment and ensure connectivity. ... The objective of MIS channel assignment is to assign channels such that the number of links that can be activated simultaneously is maximized. ...
2010 8th International Conference on Communications, 2010
ABSTRACT The capacity of wireless mesh networks can be enhanced with judicious channel assignment... more ABSTRACT The capacity of wireless mesh networks can be enhanced with judicious channel assignment. This paper deals with one particular type of mesh network topology - the tree topology. The unique characteristics of this topology is that all the traffic to/from the mesh nodes goes through the root. This enables design of an efficient channel allocation algorithm that utilizes the intrinsic characteristics of the tree topology and the traffic pattern over this topology. We use the unique connection characteristics of the tree topology to create an auxiliary contention graph over which we execute our coloring algorithm. This mitigates the burden of ensuring connectivity that channel allocation algorithms for mesh have to consider and the algorithm can solely focus on the task of capacity maximization. Our algorithm has a low complexity of O(N2) for a mesh network with N nodes.
Lecture Notes in Computer Science, 2006
Traditional network file systems, like NFS, do not extend to wide-area due to low bandwidth, high... more Traditional network file systems, like NFS, do not extend to wide-area due to low bandwidth, high network latency, and dynamism introduced in the WAN environment. Metadata access latency is a significant performance problem for Wide Area File Systems, since metadata requests constitute a large portion of all file system requests, are synchronous, and cannot be cached at clients.
Proceedings of the 15th international conference on World Wide Web - WWW '06, 2006
Current web search engines are retrospective in that they limit users to searches against already... more Current web search engines are retrospective in that they limit users to searches against already existing pages. Prospective search engines, on the other hand, allow users to upload queries that will be applied to newly discovered pages in the future. Some examples of prospective search are the subscription features in Google News and in RSS-based blog search engines.
2nd European Conference on Universal Multiservice Networks. ECUMN'2001 (Cat. No.02EX563), 2002
Abstract Many ISPs use MPLS for traffic engineering to account for and utilize their resources pr... more Abstract Many ISPs use MPLS for traffic engineering to account for and utilize their resources properly. A fundamental problem in MPLS is to reduce the label space usage by label switched paths (LSPs), while meeting the flow requirements. While routing ...
Fifth Annual IEEE International Conference on Pervasive Computing and Communications Workshops (PerComW'07), 2007
IEEE 60th Vehicular Technology Conference, 2004. VTC2004-Fall. 2004, 2004
Poor coverage is a major concern in cellular networks; it is also an inherent problem in HSDPA/HD... more Poor coverage is a major concern in cellular networks; it is also an inherent problem in HSDPA/HDR-based third generation (3G) wireless downlink data access. Poor coverage lowers the overall utilization of the cell and results in locationdependent downlink throughput for mobile users. In this paper, we investigate issues related to the design and application of an adhoc relay network (ARN) capable of relaying data from 3G base station to mobile users and provide a more uniform downlink data access. In order to exploit the benefits of ARN, we propose the AdhoCell architecture based on a self-organized ARN. The architecture is flexible in terms of deployment and is easy to integrate with current 3G architectures. These features are based on the ARN design and route computation scheme that we present in this paper. To utilize the ARN in the most efficient manner, we propose a two-level scheduling strategy, where the base station and some of the ARN nodes participate. Simulation results show the performance of the proposed ARN scheme significantly improve the HSDPA system
2004 IEEE International Conference on Communications (IEEE Cat. No.04CH37577), 2004
In this paper, we propose enhancements to radio link protocols by identifying decisive frames and... more In this paper, we propose enhancements to radio link protocols by identifying decisive frames and categorizing them as crucial and non-crucial. The fact that initial frames from the same upper layer segment can afford a few trials of retransmissions and the later frames cannot, motivates our work. We treat the frames differentially with respect to FEC coding and ARQ schemes. We consider specific cases of FEC and ARQ strategies and qualitatively show how the differential treatment of frames can improve the performance of the RLP.
IEEE INFOCOM, 2006
Voice trafc on the Internet (VoIP) is poised to grow rapidly but the Internet is not engineered f... more Voice trafc on the Internet (VoIP) is poised to grow rapidly but the Internet is not engineered for such delay- sensitive applications. We show how the end-user quality of many VoIP calls can be improved by rerouting them in an intermediate overlay network and thought the use of various path-diversity and error-coding techniques. We present an overlay network (OverPhone) that
ACM SIGMETRICS Performance Evaluation Review, 2006
... Sudeept Bhatnagar, Samrat Ganguly, Rauf Izmailov NEC Laboratories, Princeton, NJ 08540, USA {... more ... Sudeept Bhatnagar, Samrat Ganguly, Rauf Izmailov NEC Laboratories, Princeton, NJ 08540, USA {sudeept,samrat,rauf}@nec-labs.com ... 1. INTRODUCTION We present Π-Stream, a system which enables fast real-time media-streaming that allows clients to take advantage of ...
Journal of tropical pediatrics, 2014
We report a 12-year-old girl presenting with acute disseminated encephalomyelitis (ADEM) along wi... more We report a 12-year-old girl presenting with acute disseminated encephalomyelitis (ADEM) along with hypertensive emergency. Hypertension persisted for few weeks following recovery and subsided with oral clonidine. Although autonomic instability in ADEM has been reported before, hypertensive emergency was not previously documented as presenting feature of ADEM.
Proceedings of the 11th international symposium on Modeling, analysis and simulation of wireless and mobile systems - MSWiM '08, 2008
In this work, we address the issue of unrealistic simulations of wireless networks using a measur... more In this work, we address the issue of unrealistic simulations of wireless networks using a measurement-based approach. The idea is to use empirical modeling using measurement data as a mechanism to model physical layer behavior. We demonstrate the power of this approach for 802.11-based networks using ns2, a packet-level network simulator. Specifically, we develop two versions of the ns2 simulator that model the wireless physical layer with different levels of fidelity. In both versions, the deferral and reception model are built using measurements. For propagation modeling, one version uses direct measurements and the other uses an empirically derived model. In validation experiments with a 12-node mesh testbed, both these versions were found to be reasonably accurate (85 percentile errors within about 10% of the capacity) relative to regular simulations (85 percentile errors within 50% of capacity).
2008 International Symposium on a World of Wireless, Mobile and Multimedia Networks, 2008
... We thank Dr. Shamik Sengupta of Stevens Institute of Technology for broadly publicizing this ... more ... We thank Dr. Shamik Sengupta of Stevens Institute of Technology for broadly publicizing this workshop. ... We hope you'll enjoy the program. Mainak Chatterjee, University of Central Florida Samrat Ganguly, NEC Americas June 2008 xiv
Proceedings of the 13th annual ACM international conference on Mobile computing and networking - MobiCom '07, 2007
We present a practical, measurement-based model that captures the effect of interference in 802.1... more We present a practical, measurement-based model that captures the effect of interference in 802.11-based wireless LAN or mesh networks. The goal is to model capacity of any given link in the presence of any given number of interferers in a deployed network, carrying any specified amount of offered load. Central to our modeling approach is a MAC-layer model for 802.11 that is fed by PHY-layer models for deferral and packet capture behaviors, which in turn are profiled based on measurements. The target network to be evaluated needs only O(N ) measurement steps to gather metrics for individual links that seed the models. We provide two solution approaches -one based on direct simulation (slow, but accurate) and the other based on analytical methods (faster, but approximate). We present elaborate validation results for a 12 node 802.11b mesh network using upto 5 interfering transmissions. We demonstrate, using as comparison points three simpler modeling approaches, that the accuracy of our approach is much better, predicting link capacities with errors within 10% of the base channel datarate for about 90% of the cases.
Proceedings of the 1st international workshop on Wireless network testbeds, experimental evaluation & characterization - WiNTECH '06, 2006