Provin Gurung

Reducing energy consumption on mobile devices with WiFi interfaces

Emergence of mobile handheld devices with WiFi (IEEE 802.11) interfaces such as WiFi phones, WiFi-cellular dual-mode phones and PDAs (personal digital assistants), allow users to take full advantages of heterogeneous radio technologies. WiFi, however, was not originally designed for energy-constrained handheld devices. As a result, the standby times of a handheld device with a WiFi interface is significantly lower than what people typically experience with todays cellular phones. This paper presents and evaluates a system-level power management method devices with WiFi, or other high energy-consuming network interfaces, to significantly increase their standby times without modifications to WiFi and upper layer protocols and implementations.

Ad hoc mobility protocol suite for the MOSAIC ATD

An ad hoc mobility protocol suite (AMPS) aimed at providing rapidly deployable, secure, robust IP-based communications among tactical mobile ad hoc nodes is presented in this paper. AMPS is an integrated networking solution for the MOSAIC ATD in that it provides the following capabilities: autoconfiguration, mobility management, unicast and multicast routing, reliable transport, quality of service, security and network visualization tools. This paper describes the architecture and implementation of AMPS for the MOSAIC ATD. Both laboratory and field experiments to measure AMPS functionality and performance were conducted in 2002 and 2003. This paper reports on the results of those experiments and their impact on future AMPS design and operation.

Realistic wireless emulation for performance evaluation of tactical MANET protocols

Traditional approaches for testing MANET protocols and applications prior to field experimentation often involve simulation tools or small-sized physical testbeds. However, simulation tools typically do not run in real-time and rely on simplified models rather than a real system, while physical testbeds are prohibitively expensive to build and operate. A more practical method is to use emulation tools as they provide high-fidelity network modeling in a cost-effective manner without sacrificing realism. In this paper, we present the use of Wireless IP Scalable EmulatoR (WISER) and its capabilities for testing and evaluating two network routing agents, namely Congestion Control Agent (CCA) and Soft Handoff Agent (SHA), developed for tactical MANETs under the CERDEC PILSNER program. These two agents are integrated within the WISER framework, providing them a scalable and realistic wireless MANET testbed which otherwise was not readily available. Experiments demonstrating interoperability of these technologies are included.

MOSAIC ad hoc mobility protocol suite (AMPS) enhancements

The multifunctional on-the-move secure adaptive integrated communications (MOSAIC) ad hoc mobility protocol suite (AMPS) is designed to provide rapidly deployable, secure, robust IP-based communications among tactical mobile ad hoc nodes. AMPS is an integrated networking solution It combines several important capabilities: autoconfiguration, mobility management, unicast and multicast routing, reliable transport, quality of service, security and network visualization tools. These technologies were successfully tested in a field demonstration in 2003. Since then several enhancements have been made to improve the functionality, scalability and robustness of AMPS. This paper describes these enhancements.

Performance of QoS system for Future Battlefield Networks

One of the major QoS goals for Future Battlefield Networks (FBN) is to ensure Multi-level Precedence and Preemption (MLPP). Ensuring MLPP is difficult, partly due to the networking architecture for FBN which consists of wired “red” network connected by encrypted wireless “black” network. The security requirements for FBN do not allow passing information from black to red networks. So when congestion occurs in the black network, it cannot send explicit congestion notification to red-side sources for preempting flows. To address MLPP, WIN-T networks use a red-side admission controller - QoS Edge Device (QED) - that preempts low priority flows during congestion. Another technology that MLPP for FBN is the QoS Agent1, which is a black-side agent that dynamically manages WAN router queues. Both of these agents have been shown to independently uphold MLPP. For this paper we evaluated the QoS performance when both these agents were simultaneously active. We compared the performance of a system that used a red-side admission controller with a system that used both a red-side admission controller and a black-side queue management agent. Our simulations and experiments showed that the later system increases the throughput of the high priority traffic as well as that of the overall traffic. In addition it also helps in avoiding Priority Inversion, a situation where low priority flow is granted access to the network while a high priority flow is denied network access.

Local Unicast Routing Control Agent

Routing for link state routing protocols such as OSPF is determined by computing shortest-paths on the network topology graph. In conventional routing the OSPF link costs are configured a-priori before the network is deployed, and remain fixed until manually changed. If subsequently, link quality degrades or alternate links become available, routing paths may become sub-optimal in terms of throughput or end to end delay. In this paper we describe a distributed routing optimization technology called Local Unicast Routing Control Agent (L-URCA). 1 L-URCA is co-located with every router, and dynamically updates the OSPF link costs to re-route traffic away from congested or highly utilized links. L-URCA only uses local information, i.e. information that can be gathered from the local router. This removes the overhead of messaging and state synchronization between L-URCA processes. One simple heuristic for local-rerouting is to dynamically set the link cost proportional to link utilization. This tends to re-route traffic away from the congested link, however it can lead to congestion elsewhere in the network and oscillation of traffic. The heuristics of L-URCA are specifically designed to set the OSPF weights such that traffic following the shortest-path will approximately minimize the average delay experienced in the network. The heuristics proposed for L-URCA are based on robust optimization techniques that take into account uncertainties of traffic, capacity and routing decisions in other parts of the network. Examples and further steps in this ongoing research project are briefly discussed.

Inter-domain traffic engineering for tactical wireless networks using BGP

In the tactical Internet, inter-domain links consist mostly of unreliable and low bandwidth wireless links. To enable seamless routing across different Autonomous Systems (ASes), we propose an inter-domain Traffic Engineering (TE) scheme to reroute traffic when congestion occurs. There are two components for the TE scheme. First, a Traffic Splitting (TS) scheme is used for load balancing among parallel links connecting two ASes. By formulating traffic splitting as a non-linear programming problem, we minimize either the sum of packet delay or average packet delay between two ASes. Second, there is a Random Spanning Tree (RST) scheme. When traffic splitting fails to resolve congestion, we invoke the RST scheme to determine the set of optimal spanning trees for each AS. All inter-domain traffic is then rerouted accordingly on the new set of trees. The TE scheme resides in a centralized routing agent, which monitors network information and invokes the TS and RST schemes when congestion is detected. We implemented the TE scheme on QualNet and show that the TE scheme improves throughput and delay performance over several network scenarios. We also implemented the TE scheme in a testbed using Cisco routers. We demonstrate successfully that the TE scheme is responsive to real-time network data, rerouting traffic as needed to resolve congestion.