Seon Yeong Han

An Adaptive Hello Messaging Scheme for Neighbor Discovery in On-Demand MANET Routing Protocols

In mobile ad-hoc networks, local link connectivity information is extremely important for route establishment and maintenance. Periodic Hello messaging is a widely-used scheme to obtain local link connectivity information. However, unnecessary Hello messaging can drain batteries while mobile devices are not in use. This paper proposes an adaptive Hello messaging scheme to suppress unnecessary Hello messages without reduced detectability of broken links. Simulation results show that the proposed scheme reduces energy consumption and network overhead without any explicit difference in throughput.

Dynamic Link Quality Aware Routing Protocol for Multi-radio Wireless Mesh Networks

Wireless mesh networks (WMNs) are promising networks in the future Internet environments due to their self-configuration and ease of deployment. Although streaming and real time applications are possible using current mobile devices, these applications still suffer from low quality. Because link failures are not reported in congested situations, the existing routing protocols do not capture these deteriorations. An extension of the AODV-MR that is adaptive to changes in link quality is proposed in order to detect deteriorated situations and to recover the path in WMNs. The path is recovered proactively by route discovery if the quality difference of the current link and other available links exceeds the threshold which is determined by the network status. The simulation results demonstrate that the proposed method is effective in multi-radio WMNs and achieve higher throughput, lower average jitter, and lower end-to-end delay.

Price-based congestion control and local channel-link assignment for multi-radio wireless mesh networks

Display Omitted We extend a price-based approach to multi-radio wireless networks.We devise a closely coupled congestion control and local channel selection framework.We demonstrate the convergence of proportional fair rate allocation by the framework.We demonstrate the convergence of max-min fair rate allocation. In multi-radio multi-channel wireless mesh networks, engineering the network capacity requires a complex cross-layer design. In this paper, in order to make the complex problem implementable in a distributed manner, we make a decoupling approach that breaks down the entire design space into routing and initial channel assignment, and distributed congestion control and local channel reassignment. We propose a unified priced-based framework for distributed congestion control and localized channel-link assignment algorithms. We demonstrate the convergence of the proposed algorithms with respect to different fairness objectives (i.e., proportional fairness and max-min fairness) via simulation on both grid and random topologies. The proposed algorithms achieve faster convergence with less overhead in the control and forwarding plane than previous multi-path based algorithms.

Trust ME: A Trust Decision Framework for Mobile Environments

Recent advancement in smart phones enables users to collaborate in mobile environments. Their diverse communication interfaces allow them to interact with nearby devices, enabling the sharing of computing capabilities and resources among collocated users. Given the personal nature of smart phones, the selection of trustworthy users must be incorporated to enable this sharing process. In this work, a context-aware trust decision scheme for mobile ad-hoc environments is presented. This scheme is decentralized as uses information acquired by mobile phones, while leveraging social theories to reflect real-life aspects properly. The proposed scheme is validated against required properties of trust decision schemes for mobile ad-hoc environments.

Efficient and consistent path loss model for mobile network simulation

The accuracy of wireless network packet simulation critically depends on the quality of wireless channel models. Path loss is the stationary component of the channel model affected by the shadowing in the environment. Existing path loss models are inaccurate, require excessive measurement or computational overhead, and/or often cannot be made to represent a given environment. This paper contributes a flexible path loss model that uses a novel approach for spatially coherent interpolation from available nearby channels to allow accurate and efficient modeling of path loss. We show that the proposed model, called Double Regression (DR), generates a correlated space, allowing both the sender and the receiver to move without abrupt change in path loss. Combining DR with a traditional temporal fading model, such as Rayleigh fading, provides an accurate and efficient channel model that we integrate with the NS-2 simulator. We use measurements to validate the accuracy of the model for a number of scenarios. We also show that there is substantial impact on simulation behavior when path loss is modeled accurately. Finally, we show that unlike statistical models, DR can make a simulation representative of a given environment by using a small number of seeding measurements. Thus, DR provides a cost-effective alternative to ray tracing or detailed site surveys.

Application-awareness support for QoS-aware routing protocols in wireless ad-hoc networks

In order to support QoS in wireless ad-hoc networks, each node needs to monitor the network status and to determine whether the current network status satisfies the requirements of an application or not. Since the network requirements on an intermediate node are usually different from those on the end nodes, there is a need to convert the application requirement into a hop-by-hop network requirement. This paper induces link validation formulas for each node to determine if a link can satisfy the requirement of a specific application. The simulation results show the effectiveness of application-awareness on discovering appropriate routes for a specific application type in wireless ad-hoc networks.

An application-driven path discovery mechanism for MANET routing protocols

In mobile ad hoc networks (MANETs), a layered approach to networks makes a routing protocol to be responsible on discovery of a path between two nodes. However, this approach has fundamental limitations in diversifying the strategies of routing in a network when various types of applications require different routing support. In this paper, we propose an application-driven path discovery mechanism. In the proposed architecture, a routing packet controller resides in each MANET node and each application can control path discovery process by installing rules in the routing packet controller. Several examples are described to show the feasibility of our approach.

Double Regression: Efficient spatially correlated path loss model for wireless network simulation

The accuracy of wireless network packet simulation critically depends on the quality of the wireless channel models. These models directly affect the fundamental network characteristics, such as link quality, transmission range, and capture effect, as well as their dynamic variation in time and space. Path loss is the stationary component of the channel model affected by the shadowing in the environment. Existing path loss models are inaccurate, require very high measurement or computational overhead, and/or often cannot be made to represent a given environment. The paper contributes a flexible path loss model that uses a novel approach for spatially coherent interpolation from available nearby channels to allow accurate and efficient modeling of path loss. We show that the proposed model, called Double Regression (DR), generates a correlated space, allowing both the sender and the receiver to move without abrupt change in path loss. Combining DR with a traditional temporal fading model, such as Rayleigh fading, provides an accurate and efficient channel model that we integrate with the NS-2 simulator. We use measurements to validate the accuracy of the model for a number of scenarios. We also show that there is substantial impact on simulation behavior (e.g., up to 600% difference in throughput for simple scenarios) when path loss is modeled accurately.

Application-aware self-reconfigurable routing support for multi-radio MANET protocols

Recently, dynamic reconfiguration of routes using link quality metrics is required to support application requirements such as throughput or jitter in dynamically changing environments in mobile ad-hoc networks (MANETs). Since multiple types of applications will be running over a MANET, the route reconfiguration should be aware of application characteristics and requirements rather than a single application type. We propose an application-aware self-reconfiguration scheme for multi-radio routing protocols that supports distinguished route reconfiguration for each application type. The detection of a deteriorated link and the selection of an alternative link are done separately based on application types and the bandwidth requirement.