Yangcheng Huang

Adaptive MANET Routing for Low Overhead

In wireless mission-critical systems, systems may be resource-constrained including limited bandwidth, so minimising protocol overhead, whilst maintaining performance, is important. Proactive MANET routing protocols tend to provide smaller route discovery latency than on-demand protocols because they maintain route information to all the nodes in the network at all time. However, such protocols may impose excessive soft-state routing control overhead which is generated by disseminating periodic update messages. In order to mitigate the side effects of the soft-state control over-heads, we propose two adaptive proactive routing algorithms, namely DT_MIAD and DT_ODPU. By tuning the value of refresh intervals dynamically and automatically, refresh updates are triggered based on traffic conditions and node mobility. We show through simulations that the proposed adaptive routing algorithms can outperform a traditional proactive routing protocol (OLSR).

Route dynamics for Shortest Path First routing in mobile ad hoc networks

This paper investigates the route dynamics of shortest-path first (SPF) routing in mobile ad hoc networks (MANETs). In particular, we find, from a statistical analysis of route duration and route change interval, that route dynamics may require complex modelling. Our analysis considers various mobility models, node velocities and node densities of the MANET network. Our findings show that, in a MANET with moderate or high rate of mobility, the route duration could be approximated by an exponential distribution with approximate parameters, while the route duration of specific lengths could not. Our findings suggest that minimum hop-count routing in MANETs may be inappropriate and that further investigation is required in order to develop models that let us understand MANET route dynamics.

Analysing the Impact of Topology Update Strategies on the Performance of a Proactive MANET Routing Protocol

This paper presents an analysis of several topology update strategies for proactive MANET routing protocols. Although there have been a number of performance studies of proactive MANET routing protocols, little attention has been paid to the impacts of topology update strategies on routing performance. The goal of this paper is to better understand how topology update strategies can contribute to topology maintenance in proactive mobile ad hoc networks and thus impact the overall performance. Our contribution includes (1) a quantitative analysis on the impacts of proactive update intervals on the routing performance; (2) evaluating the performance of reactive topology updates and proactive updates for proactive routing protocols.

Fast-Converging Distance Vector Routing for Wireless Mesh Networks

A major concern about distance-vector routing protocols for wireless mesh networks is its slow convergence in the presence of link changes, which can potentially degrade network stability. This paper studies the impact of update intervals on network convergence and proposes a fast-converging distance-vector routing algorithm. Our simulation results have shown that the proposed algorithm could effectively reduce convergence latency and improve throughput without leading to a significant increase in control overhead.

The impact of topology update strategies on the performance of a proactive MANET routing protocol

Although there have been a number of performance studies of proactive mobile ad hoc network (MANET) routing protocols, little attention has been paid to the impacts of topology update strategies on routing performance. This paper presents an analysis of several topology update strategies for a proactive MANET routing protocol. The goal of this paper is to better understand how topology update strategies can contribute to topology maintenance in proactive MANETs and thus impact the overall performance, based on simulations involving optimised link state routing (OLSR), a popular MANET protocol. Our contribution includes (1) a quantitative analysis of the impacts of proactive update intervals on the routing performance of OLSR; (2) evaluating the performance of reactive topology updates and proactive updates for OLSR.

Decentralized resilient grid resource management overlay networks

Recently, grid and peer-to-peer overlays have attracted attention from research communities as well as industry. However, the overwhelming majority of industrial, commercial and academic activities are geared around applications, servers, and middleware. There have been some efforts in the management of the underlying networks (the connectivity for the overlays), but far from enough. This paper proposes a resilient, fault-adaptive, overlay resource management framework, with lightweight state management infrastructure, taken from some ongoing work by the authors in this area. This research aims to solve the problems of: (a) managing distributed network resources in a decentralized way; (b) providing resilient QoS for highly dynamic networks.

A Cross Layer Routing Protocol for Multihop Cellular Networks

We propose a cross-layer routing protocol for a Code Division Multiple Access (CDMA) Multihop Cellular Network (MCN). In designing the routing protocol for MCN, multiple constraints are imposed on intermediate relay node selection and end-to-end path selection. The constraints on relay nodes include willingness for cooperation, sufficient neighbourhood connectivity and the level of interference offered on the path. Path constraints include end-to-end throughput and end-to-end delay. A facile incentive mechanism is presented to motivate the cooperation between nodes in call forwarding. In addition, we present a route resilience scheme in the event of dynamic call dropping. In particular, a fast neighbour detection scheme for route resilience is proposed. Instead of using periodic HELLO messages as in traditional ad-hoc routing, the proposed neighbour detection scheme adopts an explicit handshake mechanism to reduce neighbour detection latency. We conclude the paper by demonstrating the superior performance of the proposed routing protocol compared with the other well known routing algorithms.

Autonomic MANET Routing Protocols

In Mobile Ad hoc Networks (MANETs), timers have been used widely to maintain routing (state) information. The use of fixed-interval timers is simple to implement but, in practise, may be difficult to configure in dynamic operational environments, and so may give reduced performance in the presence of frequent topology changes. This paper proposes a self-tuning timer approach within a simple control system for MANET routing protocols with the aim of allowing dynamic, autonomic, re-calibration of routing update frequencies. A novel dynamic timer algorithm is presented to automatically tune routing performance by adapting timer intervals to network conditions. Our simulation results have shown that, compared to the default fixed timer approach, the proposed algorithm could effectively improve routing throughput without manual configuration.

Self-tuning network support for MANETs

Rapid and unpredictable topology changes and resource constraints make delivering packets in a MANET (mobile ad hoc network) a challenging task. Routing information has to be updated to reflect the topology changes and maintain the correctness of route selection. On the other hand, the dissemination of control messages has to be optimised for efficient resource usage and to alleviate channel contention problems. To solve this problem, this dissertation focuses on how to automatically tune routing performance for MANETs in terms of packet delivery ratio and control overhead. The impacts of soft state signalling, especially the refresh intervals, are studied under various scenarios. A variety of topology advertisement strategies are presented. Two self-tuning neighbour detection schemes are proposed, the dynamic timer algorithm and the fast neighbour handshake algorithm, in order to enhance routing performance.

Reducing Neighbour Detection Latency in OLSR

This paper presents a fast neighbour detection scheme for a proactive MANET routing protocol. Instead of using periodic HELLO messages, the proposed scheme adopts explicit handshake mechanism to reduce the latency in neighbour detection. In particular, two route handshake options are presented, namely the Broadcast based handshake (BHS) algorithm and Unicast based handshake (UHS) algorithm. Our simulation results show that the proposed scheme improves routing performance, especially in networks with moderate or high mobility. In low-density networks, the unicast option improves the routing throughput significantly without introducing extra control overhead.