Distributed QoS Guarantees for Realtime Traffic in Ad Hoc Networks

In this paper, we propose a new cross-layer framework, named QPART ( QoS br>rotocol for Adhoc Realtime Traffic), which provides QoS guarantees to real-time multimedia applications for wireless ad hoc networks. By adapting the contention window sizes at the MAC layer, QPART schedules packets of flows according to their unique QoS requirements. QPART implements priority-based admission control and conflict resolution to ensure that the requirements of admitted realtime flows is smaller than the network capacity. The novelty of QPART is that it is robust to mobility and variances in channel capacity and imposes no control message overhead on the network

Throughput Guarantees for Multi-priority Traffic in Ad Hoc Networks

In this paper, we present MPARC (Multi-Priority Admission and Rate Control), a novel joint admission control and rate policing protocol for multi-priority ad hoc networks. MPARC is based on our novel bandwidth allocation model and guarantees that the throughput of admitted realtime flows will not decrease due to later arriving realtime flows with equal or lower priorities or due to best effort flows. MPARC achieves this goal by performing accurate admission control on every newly arriving realtime flow and appropriate rate policing on all best effort traffic. Through simulation, we demonstrate that MPARC has better performance than existing approaches

Exploiting Routing Redundancy using MAC layer Anycast to Improve Delay in WSN

Source-destination pairs in wireless sensor networks often have multiple shortest hop paths because the nodes are densely deployed. These multiple paths provide a great opportunity to reduce delay as well as energy in an asynchronous duty-cycled network. In this paper, we exploit the redundancy available at the route layer using MAC-layer anycasting and reduce the delay incurred at each hop as the sender waits for its next hop node to be awake. By applying anycast to existing X-MAC and NPM protocols, we show that anycast can be incorporated into duty-cycled MAC protocols by using small modifications. Our evaluations in ns-2 show that the modified X-MAC and NPM protocols can achieve delay improvements of 30% and 12% respectively by exploiting the route level redundancy using anycast.NSF CNS 05-19817unpublishedis peer reviewe

Distributed Optimal Contention Window Control for Elastic Traffic in Wireless LANs

This paper presents a distributed contention window control control algorithm, GCA (General Contention window Adaptation), that achieves various bandwidth allocation policies and at same time efficient channel utilization. By modeling different bandwidth allocation policies as optimization problems of contention window assignment, we are able to design GCA and prove that it converges to the solution of the contention window assignment problem. By examining the stability properties of GCA, we identify the optimal stable point that maximizes channel utilization and provide solutions to control the stable point of GCA near the optimal point. Simulation results show that GCA achieves fairness and efficiency. Due to the generality of GCA, our work provides a theoretical foundation to analyze existing and design new contention window control algorithms

Achieving Loss Discrimination with Congestion Avoidance in a Rate-based Protocol

The stability of the Internet depends on the presence of well-behaved flows. While TCP forms the majority of the traffic over the Internet, the Internet user community is also dedicated to supporting mobile devices over wireless networks. However, TCP is not well suited to support applications over lossy wireless networks. Ideally, these applications require a protocol that adapts to network conditions with the ability to discriminate congestion-based and transmission-based losses. In this paper, we present a rate-based transport protocol that is designed to support communication for mobile nodes using infrastructure-based wireless networks. We propose an end-to-end approach to loss discrimination based on network state estimation at the receiver. Discrimination is achieved by correlating short-term history of packet inter-arrival times with the loss. We also integrate a congestion avoidance algorithm to react to pending network congestion. Simulations of our protocol prototype show that rate-based protocols can provide better correlation to network conditions than ACK-clocked protocols. We provide extensive evaluation through simulation demonstrating that our protocol is well-behaved over a wide range of scenarios

Cooperative solutions to the dynamic management of communication resources

Ph.D.Ken L. Calver

Mobile Learning Communities - Are We There Yet?

Advances in wireless technologies have allowed users to communicate ubiquitously anywhere and anytime and made it possible for users to access and exchange information through wireless hand-held devices such as cell-phones, tablets and laptops. Especially, if we consider our university campuses, 802.11 WiFi infrastructure is everywhere and most students use laptops and diversity of cell-phones for their personal and school work to connect to various resources via WiFi. In this report, we are exploring the premise of cell-phones as educational tools for undergraduate students in our educational institution, and creation of effective mobile learning communities through the usage of cell-phones. Through one year investigation, we wanted to answer three major questions: (1) how would a mobile phone be used as an educational tool in and out of classroom, (2) how would an educational unit deploy phones and educational services to all undergraduate students semester after semester, and (3) is the WiFi communication infrastructure at the educational institution ready for massive phone deployment in and out of classroom. Through combination of discussions with undergraduate students, implementation of educational projects by students and for students, deployment of phones in selected classes, and measurements of WiFi infrastructure performance during phone usage in classrooms, we present the complexity of the issues when answering the questions and the difficulties to consider when it comes to mobile learning communities on a university campus.NSF 0855129Vodafone Inc. - Educational Equipment GrantGoogle Inc. - DROID Equipment GiftQualcomm Inc.unpublishednot peer reviewe

Dynamically Configurable Communication Protocols and Distributed Applications: Motivation and Experience

Due to the diverse communication requirements of today's distributed applications, our work has led us in the direction of dynamically configurable protocol systems. This paper motivates the design of a framework for such systems. We discuss the initial study that drove the design of our framework, and describe the framework and the associated interfaces. Finally, we present the results from an experiment involving an adaptable application using a variable reliability protocol