Amal El-Nahas

Time-shift scheduling—fair scheduling of flows in high-speed networks

We present a scheduling protocol, called time-shift scheduling, to forward packets from multiple input flows to a single output channel. Each input flow is guaranteed a predetermined packet rate and an upper bound on packet delay. The protocol is an improvement over existing protocols because it satisfies the properties of rate-proportional delay, fairness, and efficiency, while existing protocols fail to satisfy at least one of these properties. In time-shift scheduling each flow is assigned an increasing timestamp, and the packet chosen for transmission is taken from the flow with the least timestamp. The protocol features the novel technique of time shifting, in which the schedulers real-time clock is adjusted to prevent flow timestamps from increasing faster than the real-time clock. This bounds the difference between any pair of flow timestamps, thus ensuring the fair scheduling of flows.

Location management techniques for mobile systems

Abstract Locating users in mobile environment is an essential problem in PCS that becomes more challenging as the network size increases and the user population grows. In third generation mobile systems, the signaling traffic and processing overhead of location updates is expected to grow tremendously leading to poor performance. Therefore location management schemes should aim at reducing the cost of updates. Yet, the lookup delay should be kept minimum. This paper aims at classifying the various approaches used for location management of mobile users by grouping them into two main categories. The first category comprises techniques that focused on reducing the cost of looking up a user and adjusted the update process accordingly. These are classified into replication , caching and selective paging techniques. The second category consists of techniques that focused on reducing the cost of updates and maneuvered the update policy to reduce the lookup cost by informing the system with the maximum possible information about users mobility. This could be achieved by the use of statistic collection, estimation or prediction processes. We classify those schemes into three main classes: schemes based on forwarding pointers , learning-based schemes and prediction-based schemes. By investigating the technical significance of each class a new direction for future research is proposed which favors the second category of location techniques and emphasis the importance of adopting suitable learning and prediction techniques to optimize the overall location cost.

A profile-based hierarchical location management scheme for future PCS

To accommodate the growth in the user population and network size in mobile environments, hierarchical architectures of location databases have been proposed. Recent studies showed that the signaling traffic and processing overhead of location updates is expected to grow tremendously, leading to poor performance. The authors present a Profile based Hierarchical location management Scheme (PHS) that focuses on reducing the cost of updates while keeping the lookup cost low. Our proposal is motivated by the observation that users follow repetitive patterns that can be profiled and predicted with reasonable cost, allowing users to send updates occasionally and not on every move. Further, it deploys a simple prediction technique that reduces the uncertainty of a users location. We quantify the costs and benefits of PHS for several mobility patterns and show that it can result in up to 60% reduction in the update cost with minimal increase (7%) in lookup cost.

Fast localization in indoor environments

In this paper, we propose an algorithm for fast indoor localization. The algorithm does not require any sensors to be installed; instead, localization is determined using image matching. Our system studies (or learns) the indoor environment through detecting image junctions using the so-called JUDOCA detector. Any 2-edge junction forms a triangle that can be used to store information and recognize the environment afterwards. Correlation is applied to points denoted with respect to one side of the triangle formed by the junction. Experiments show that this approach reaches similar accuracy of the affine-based correlation approach in less processing time.

Sustained service lookup in areas of sudden dense population

As mobility became the norm rather than the exception, location-based services are playing more of a key role in assisting mobile users. In this paper, we address the challenges of providing location-based services to users in areas of sudden population increases, such as stadiums and traffic jams. A sudden increase in the number of mobile users leads to an increasing demand for the already scarce wireless bandwidth, thus causing dramatical throughput degradation and an increase in connectivity failures. We propose a hybrid model within which a peer-to-peer mode is deployed to assist the cellular-based network whenever a sudden increase in population density is sensed by the base station. Location-based data is migrated to selected elite nodes, thus allowing other peer nodes to get their information locally. This approach is proven, through experimental results, to decrease the query response time and number of query failures. Copyright

Traffic Differentiating Queue For Enhancing AODV Performance in Real-Time Interactive applications

The phenomenal growth rate of voice over IP applications is fueling the demand of bridging the gap between real-time QoS guarantees and QoS in ad hoc networks. Multimedia applications are designed for stable networks, with unstable mobile ad-hoc networks presenting a challenge for such applications. Real-time applications require mechanisms that guarantee bounded delay and delay jitter. This paper proposes a traffic differentiating queue (TDQ) for AODV to provide higher QoS guarantees for real-time interactive applications. The popular object-oriented network simulator NS2 has been used for the cross evaluation of the proposed TDQ-AODV. The modified algorithm provides significant improvement over the original algorithm in the average packet delay and throughput, in which the average modification improvement reaches up to 1.5times. Moreover, jitter is generally reduced and stabilized over the varying number of connections.

Generic Geo-Social Mobility Model for VANET

Simulation is a key feature in validating the protocols dedicated for VANET applications. Since the vehicles mobility is driven by the human mobility characteristics and is controlled by the geographical restrictions of the roads, the work presented in this paper is aimed to having a realistic mobility model that incorporates both the social aspects of human mobility together with the geographical restrictions that governs the movement of the mobile nodes. This mobility model is dedicated for testing the protocols related to the delay tolerant applications where unicasting/multicasting is used for data dissemination rather than broadcasting. Thus location awareness and destination prediction is essential. The model is based on using realistic data sets rather than randomly generated data. Evaluating the technique using the SUMO simulator have proven a range of 80% to 90% of match between the predicted traces and real life data available for evaluation.

Generic Geo-Social Mobility Model for VANET Simulation

Vehicular Ad Hoc Network (VANET) simulation is a key feature in validating the protocols dedicated for VANET applications. Since the vehicles mobility is driven by the human mobility characteristics and controlled by the geographical restrictions of the roads, the work presented in this paper is aimed to having a realistic mobility model that incorporates both the social aspects of human mobility together with the geographical restrictions that governs the movement of the mobile nodes.

LSD: link strength based discovery protocol for dynamic ad hoc networks

Service discovery is one of the main enabling gears for ubiquitous computing where people and computational devices embedded in the surroundings invisibly interact and share services. Such services, either hardware like printers and fax machines, or software like files and drivers, need to be discovered and invoked with minimum user intervention. This is the role of service discovery protocols. In this paper, we propose a fully distributed, energy efficient service discovery protocol for highly dynamic ad hoc environment. The proposed protocol opts for saving device energy and delay by selecting the most stable routes to the service providers. The protocol is evaluated through simulation experiments. Results showed a significant improvement in terms of saving the power capacity of the devices in the network and minimising the delay and the failure rate of service requests.

Profile-Based Sustained Service Lookup in Areas of Sudden Dense Population

This paper addresses some of the challenges associated with providing location-based services to mobile users in areas of sudden density increases. We adopt a profile-based peer to peer mode that allows host queries, upon density increase, to obtain their data from built in logical entities within our system called autonomous systems. Autonomous systems are a composite of elite mobile devices selected upon the occurrence of sudden density to cache service data. This work expands on a previously published work by us that demonstrated how sudden densities are detected, how autonomous systems are selected and formed, and how data is cached. In this paper, autonomous systems formation, distribution, and record caching are made highly sensitive to individual users profiles. Simulation and experimental results demonstrate that this approach decreased the latency associated with service lookups as well as increasing the ability to accommodate more mobile users at times of disrupted services.