Yaoda Liu

Provisioning of adaptability to variable topologies for routing schemes in MANETs

Frequent changes in network topologies caused by mobility in mobile ad hoc networks (MANETs) impose great challenges to designing routing schemes for such networks. Various routing schemes each aiming at particular type of MANET (e.g., flat or clustered MANETs) with different mobility degrees (e.g., low, medium, and high mobility) have been proposed in the literature. However, since a mobile node should not be limited to operate in a particular MANET assumed by a routing scheme, an important issue is how to enable a mobile node to achieve routing performance as high as possible when it roams across different types of MANETs. To handle this issue, a quantity that can predict the link status for a time period in the future with the consideration of mobility is required. In this paper, we discuss such a quantity and investigate how well this quantity can be used by the link caching scheme in the dynamic source routing protocol to provide the adaptability to variable topologies caused by mobility through computer simulation in NS-2.

Reliable Broadcast in Error-Prone Multi-Hop Wireless Networks: Algorithms and Evaluation

Reliable broadcast is an essential functionality for disseminating messages to all nodes in a multi-hop wireless network. Ensuring broadcast reliability while minimizing communication overhead is a challenging task when error-prone links are considered. In this paper, we introduce and analyze techniques to address this challenge, and propose an overall algorithm encompassing a combination of the investigated techniques as an efficient solution for reliable broadcasting in multi-hop wireless networks. Simulations are conducted to validate the analytical results and to further evaluate the performance of the algorithm.

An enhanced optimized link state routing with delayed event driven link state updating

A simulation study of an enhanced version of optimized link state routing is presented in this paper. Instead of periodic link state updating as in optimized link state routing (OLSR), a new form of event driven link state updating, namely delayed event driven link state updating is deployed. In this paper, the protocol is evaluated by detailed simulation experiments. The simulation results show the superiority of the proposed scheme with respect to the adaptability to mobility. The scheme combines the advantages of both periodic updating and event driven updating

Localized Algorithms for Virtual Backbone Formation in Wireless Multi-hop Networks with unidirectional links

A virtual backbone can be utilized in various network optimizations in wireless multi-hop networks. Many distributed algorithms have been proposed for virtual backbone formation in the last decade. However, the assumption of undirected graph as the topology model in most existing work may not hold in real scenarios, where unidirectional links occur for many reasons. Moreover, in most of the existing algorithms, there is dependency among the decisions of different nodes. In this paper, we propose a new localized algorithm for the construction of a virtual backbone by forming a connected dominating and absorbent set. Besides the locality, the proposed algorithm also constructs a virtual backbone of smaller size compared to the existing algorithms.

An adaptive link caching scheme for on-demand routing in MANETs

With on-demand routing protocols for mobile ad hoc networks (MANETs), for example, dynamic source routing (DSR), a source node tries to find a route to the destination node only when it has a packet addressed to that destination node. And the source node can find a route either from its own route cache or by initializing a route discovery. To reduce the traffic generated by such route discoveries, caching of routing information is necessary. And in the design of caching schemes, cache timeout (i.e., the time period that a link would stay in the cache) is a critical parameter. However, only a few works have been done on how to set it. In this paper, we propose a new link caching scheme with adaptive timeouts. In this scheme, the cache timeout of a link is decided based on the estimation of the links lifetime. Simulation results show that the proposed scheme can adapt to scenario changes and hence improve the performance of on-demand routing for MANETs.

Cooperation of Network and Service Layer in Mobile Ad hoc Networks

In this article, we investigate how a service discovery protocol at the service layer in Mobile Ad Hoc Networks can be improved, by utilizing routing information from the network layer. We consider in this article proactive routing protocols as basis for the underlying routing mechanism, and focus on the optimization of proactive service discovery protocols. First we introduce a general framework, enabling the cooperation of service layer and network layer, and then we propose the optimization scheme. The performance evaluation done by simulation shows that the proposed cooperation scheme can optimize the service discovery protocol, i.e. reduce the communication cost of service discovery, by utilizing routing table and topology information.

Circuit-Elimination based Link-State Routing in Mobile Ad-hoc Networks

Circuit-elimination based connected dominating set formation is an efficient technique for reducing routing overhead in mobile ad hoc networks. In this paper, we propose a new message dissemination algorithm which utilizes such techniques to reduce the number of nodes that generate or forward link state advertisements in link state routing protocols. Simulation results with both static and dynamic network topologies demonstrate the potential of the proposed algorithm to reduce routing overhead, compared with a benchmark link state routing protocol, OLSR.