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Dive into the research topics where Karim Seada is active.

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Featured researches published by Karim Seada.


international conference on embedded networked sensor systems | 2004

Energy-efficient forwarding strategies for geographic routing in lossy wireless sensor networks

Karim Seada; Marco Zuniga; Ahmed Helmy; Bhaskar Krishnamachari

Recent experimental studies have shown that wireless links in real sensor networks can be extremely unreliable, deviating to a large extent from the idealized perfect-reception-within-range models used in common network simulation tools. Previously proposed geographic routing protocols commonly employ a maximum-distance greedy forwarding technique that works well in ideal conditions. However, such a forwarding technique performs poorly in realistic conditions as it tends to forward packets on lossy links. We identify and illustrate this weak-link problem and the related distance-hop trade-off, whereby energy efficient geographic forwarding must strike a balance between shorter, high-quality links, and longer lossy links. The study is done for scenarios with and without automatic repeat request (ARQ). Based on an analytical link loss model, we study the distance-hop trade-off via mathematical analysis and extensive simulations of a wide array of blacklisting/link-selection strategies; we also validate some strategies using a set of real experiments on motes. Our analysis, simulations and experiments all show that the product of the packet reception rate (PRR) and the distance traversed towards destination is the optimal forwarding metric for the ARQ case, and is a good metric even without ARQ. Nodes using this metric often take advantage of neighbors in the transitional region (high-variance links). Our results also show that reception-based forwarding strategies are more efficient than purely distance-based strategies; relative blacklisting schemes reduce disconnections and achieve higher delivery rates than absolute blacklisting schemes; and that ARQ schemes become more important in larger networks.


information processing in sensor networks | 2004

On the effect of localization errors on geographic face routing in sensor networks

Karim Seada; Ahmed Helmy; Ramesh Govindan

In the absence of localization errors, geographic routing - using a combination of greedy forwarding and face routing - has been shown to work correctly and efficiently. The effects of location errors on geographic routing have not been studied before. In this work we provide a detailed analysis of the effects of location errors on the correctness and performance of geographic routing in static sensor networks. First, we perform a micro-level behavioural analysis to identify the possible protocol error scenarios and their conditions and bounds. Then, we present results from an extensive simulation study of GPRS and GHT to quantify the performance degradation due to location errors (of 10% of the radio range or less) can in fact lead to incorrect (non-recoverable) geographic routing with noticeable performance degradation. We then introduce a simple modification for face routing that eliminates probable errors and leads to near perfect performance.


international conference on supporting group work | 2010

Enhancing group recommendation by incorporating social relationship interactions

Mike Gartrell; Xinyu Xing; Qin Lv; Aaron Beach; Richard Han; Shivakant Mishra; Karim Seada

Group recommendation, which makes recommendations to a group of users instead of individuals, has become increasingly important in both the workspace and peoples social activities, such as brainstorming sessions for coworkers and social TV for family members or friends. Group recommendation is a challenging problem due to the dynamics of group memberships and diversity of group members. Previous work focused mainly on the content interests of group members and ignored the social characteristics within a group, resulting in suboptimal group recommendation performance. In this work, we propose a group recommendation method that utilizes both social and content interests of group members. We study the key characteristics of groups and propose (1) a group consensus function that captures the social, expertise, and interest dissimilarity among multiple group members; and (2) a generic framework that automatically analyzes group characteristics and constructs the corresponding group consensus function. Detailed user studies of diverse groups demonstrate the effectiveness of the proposed techniques, and the importance of incorporating both social and content interests in group recommender systems.


workshop on mobile computing systems and applications | 2010

Fusing mobile, sensor, and social data to fully enable context-aware computing

Aaron Beach; Mike Gartrell; Xinyu Xing; Richard Han; Qin Lv; Shivakant Mishra; Karim Seada

In this paper, we identify mobile social networks as an important new direction of research in mobile computing, and show how an expanded definition of mobile social networks that includes sensor networks can enable exciting new context-aware applications, such as context-aware video screens, music jukeboxes, and mobile health applications. We offer SocialFusion as a system capable of systematically integrating such diverse mobile, social, and sensing input streams and effectuating the appropriate context-aware output action. We explain some of the major challenges that SocialFusion must overcome. We describe some preliminary results that we have obtained in implementing the SocialFusion vision.


ACM Transactions on Sensor Networks | 2008

Efficient geographic routing over lossy links in wireless sensor networks

Marco Zúñiga Zamalloa; Karim Seada; Bhaskar Krishnamachari; Ahmed Helmy

Recent experimental studies have shown that wireless links in real sensor networks can be extremely unreliable, deviating to a large extent from the idealized perfect-reception-within-range models used in common network simulation tools. Previously proposed geographic routing protocols commonly employ a maximum-distance greedy forwarding technique that works well in ideal conditions. However, such a forwarding technique performs poorly in realistic conditions as it tends to forward packets on lossy links. Based on a recently developed link loss model, we study the performance of a wide array of forwarding strategies, via analysis, extensive simulations and a set of experiments on motes. We find that the product of the packet reception rate and the distance improvement towards destination (PRR × d) is a highly suitable metric for geographic forwarding in realistic environments.


wireless communications and networking conference | 2004

Efficient geocasting with perfect delivery in wireless networks

Karim Seada; Ahmed Helmy

Geocasting is the delivery of packets to nodes within a certain geographic area. For many applications in wireless networks, geocasting is an important and frequent communication service. The challenging problem in geocasting is distributing the packets to all the nodes within the geocast region with high probability but with low overhead. According to our study we notice a clear tradeoff between the proportion of nodes in the geocast region that receive the packet and the overhead incurred by the geocast packet especially at low densities and irregular distributions. We present two novel protocols for geocasting that achieve high delivery rate and low overhead by utilizing the local location information of nodes to combine geographic routing mechanisms with region flooding. We show that the first protocol (GFG) has close-to-minimum overhead in dense networks and that the second protocol (GFPG) provides guaranteed delivery without global flooding or global network information even at low densities and with the existence of region gaps. A practical version of the second protocol (GFPG) has the desirable property of perfect delivery at all densities and close-to-minimum overhead at high densities. We evaluate our mechanisms and compare them using simulation to the currently proposed geocasting mechanisms. The results show the significant improvement in delivery rate (up to 63% higher delivery percentage in low density networks) and reduction in overhead (up to 80% reduction) achieved by our mechanisms.


international parallel and distributed processing symposium | 2004

Rendezvous regions: a scalable architecture for service location and data-centric storage in large-scale wireless networks

Karim Seada; Ahmed Helmy

Summary form only given. In large-scale wireless networks such as mobile ad hoc and sensor networks, efficient and robust service discovery and data-access mechanisms are both essential and challenging. Rendezvous-based mechanisms provide a valuable solution for provisioning a wide range of services. We describe rendezvous regions (RRs) - a novel scalable rendezvous-based architecture for wireless networks. RR is a general architecture proposed for service location and bootstrapping in ad hoc networks, in addition to data-centric storage, configuration, and task assignment in sensor networks. In RR the network topology is divided into geographical regions, where each region is responsible for a set of keys representing the services or data of interest. Each key is mapped to a region based on a hash-table-like mapping scheme. A few elected nodes inside each region are responsible for maintaining the mapped information. The service or data provider stores the information in the corresponding region and the seekers retrieve it from there. We run extensive detailed simulations, and high-level simulations and analysis, to investigate the design space, and study the architecture in various environments including node mobility and failures. We evaluate it against other approaches to identify its merits and limitations. The results show high success rate and low overhead even with dynamics. RR scales to large number of nodes and is highly robust and efficient to node failures. It is also robust to node mobility and location inaccuracy with a significant advantage over point-based rendezvous mechanisms.


ad hoc networks | 2007

Modeling and analyzing the correctness of geographic face routing under realistic conditions

Karim Seada; Ahmed Helmy; Ramesh Govindan

Geographic protocols are very promising for wireless ad hoc and sensor networks due to the low state storage and low message overhead. Under certain idealized conditions, geographic routing - using a combination of greedy forwarding and face routing - has been shown to work correctly and efficiently. In this work we model and analyze the correctness of geographic routing under non-ideal realistic conditions. We present a systematic methodology for micro-level behavioral analysis that shows that conditions that violate the unit-graph assumption of network connectivity, such as location errors, obstacles and radio irregularity, cause failure in planarization and consequently face routing. We then discuss the limitations of fixing these failures and prove that local algorithms that use only information up to a limited number of hops are not sufficient to guarantee face routing delivery under arbitrary connectivity. In addition, we analyze the effect of location errors in more detail to identify the possible protocol error scenarios and their conditions. We present results from an extensive simulation study about the effects of location errors on GPSR and GHT to quantify their performance degradation at different error ranges, distributions and error models. Based on our analysis we present a potential fix based on local information sharing that improves the performance significantly but does not remove all failures. Finally, we conclude that in order to avoid all failures under arbitrary connectivity, we need a non-local algorithm that can search or propagate information for an unlimited number of hops.


Computer Communications | 2006

Efficient and robust geocasting protocols for sensor networks

Karim Seada; Ahmed Helmy

Geocasting is the delivery of packets to nodes within a certain geographic area. For many applications in wireless ad hoc and sensor networks, geocasting is an important and frequent communication service. The challenging problem in geocasting is distributing the packets to all the nodes within the geocast region with high probability but with low overhead. According to our study we notice a clear tradeoff between the proportion of nodes in the geocast region that receive the packet and the overhead incurred by the geocast packet especially at low densities and irregular distributions. We present two novel protocols for geocasting that achieve high delivery rate and low overhead by utilizing the local location information of nodes to combine geographic routing mechanisms with region flooding. We show that the first protocol Geographic-Forwarding-Geocast (GFG) has close-to-minimum overhead in dense networks and that the second protocol Geographic-Forwarding-Perimeter-Geocast (GFPG) provides guaranteed delivery without global flooding or global network information even at low densities and with the existence of region gaps or obstacles. An adaptive version of the second protocol (GFPG*) has the desirable property of perfect delivery at all densities and close-to-minimum overhead at high densities. We evaluate our mechanisms and compare them using simulation to other proposed geocasting mechanisms. The results show the significant improvement in delivery rate (up to 63% higher delivery percentage in low density networks) and reduction in overhead (up to 80% reduction) achieved by our mechanisms. We hope for our protocols to become building block mechanisms for dependable sensor network architectures that require robust efficient geocast services.


international conference on computer communications | 2009

An Experimental Study on Wi-Fi Ad-Hoc Mode for Mobile Device-to-Device Video Delivery

Bo Xing; Karim Seada; Nalini Venkatasubramanian

The demand for video content is continuously increasing as video sharing on the Internet is becoming enormously popular recently. This demand, with its high bandwidth requirements, has a considerable impact on the load of the network infrastructure. As more users access videos from their mobile devices, the load on the current wireless infrastructure (which has limited capacity) will be even more significant. Based on observations from many local video sharing scenarios, in this paper, we study the tradeoffs of using Wi-Fi ad-hoc mode versus infrastructure mode for video streaming between adjacent devices. We thus show the potential of direct device-to-device communication as a way to reduce the load on the wireless infrastructure and to improve user experiences. Setting up experiments for Wi-Fi devices connected in ad-hoc mode, we collect measurements for various video streaming scenarios and compare them to the case where the devices are connected through access points. The results show the improvements in latency, jitter and loss rate. More importantly, the results show that the performance in direct device-to-device streaming is much more stable in contrast to the access point case, where different factors affect the performance causing widely unpredictable qualities.

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Ramesh Govindan

University of Southern California

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Aaron Beach

University of Colorado Boulder

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Bhaskar Krishnamachari

University of Southern California

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Mike Gartrell

University of Colorado Boulder

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