2010 International Conference on Computer Application and System Modeling (ICCASM 2010)
A Novel Cluster-Based Routing Protocol and Cluster Reformation Criteria for Mobile Ad Hoc Networks Zhengmin Kong, Liang Zhong, Guangxi Zhu, Li Yu Department of Electronics and Information Engineering, Wuhan National Lab for Optoelectronics, Huazhong University of Science Wuhan, China E-mail:
[email protected] Abstract-In
many traditional hierarchical routing protocols
proposed for mobile ad hoc networks, each cluster designates a single cluster-head (CH) node to relay inter-cluster traffic. These
cluster-head nodes
become
traffic "hot-spots" and
restricting cluster to access through cluster-head lead
to sub-optimal route.
To
solve
these
nodes can
problems,
we
proposed a novel cluster-based distributed gateways routing protocol, namely DGR. In our proposed scheme, we rely on border mobile terminals (BMTs) as gateways for inter-cluster routing instead of relying on eHs. eHs are not necessarily involved in each route search and data transmission process. In addition, we also proposed a cluster reformation criterion to avoid unnecessary cluster reformation. It is proved that the proposed scheme can reduce the route search time, alleviate the burden of eHs and achieve optimal routes. Moreover, it can make clusters much more stable for nodes mobility under the proposed cluster reformation criteria.
Keywords-Ad hoc networks; hierarchical routing; distributed gateways routing (DGR); cluster reformation criteria; communication overhead, route search time; load balance 1.
INTRODUCTION
The Mobile Ad Hoc Networks (MANETs) are self-organizing and rapidly deployable networks in which neither a wired backbone nor a centralized control exists. Moreover, as a matter of fact, MANETs are collections of both mobile and static terminals which may behave like terminals and routers, and the packets may be exchanged between sources and destinations over scarce wireless channels in a multi-hop fashion. Due to the mobility of network nodes and the changing propagation conditions, the dynamic nature of the network inevitably makes the task of routing in MANETs far more difficult than in wired networks. Moreover, it is commonly assumed for MANETs that the wireless links tend to be relatively low capacity fixed-sized links (i.e., no hierarchy in the physical topology of the network) [1]. In addition, traditional flat architectures are not bandwidth efficient in large networks because control messages have to propagate globally throughout the network. The scalability gets worse when the number of nodes increases. To address the problem of routing with low overhead, various design approaches based on hierarchical architectures for ad hoc networks are proposed. In hierarchical architectures, the detail of the network topology is concealed by aggregating nodes into clusters and clusters into super clusters and so on. Clustering basically transforms a physical network into a virtual network of
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interconnected clusters or groups of nodes. Control messages may only have to propagate within a cluster. Thus, the multilevel hierarchy reduces the storage requirement and the communication overhead of large wireless networks [2]. Hence, Clustering strategies tend mainly to support the network scalability. However, in many hierarchical routing protocols, each cluster designates a single cluster-head node to relay inter-cluster traffic. Cluster-heads (CHs) thereby take on a special role in managing routing information and have a higher computation and communication burden than other nodes. These cluster-head nodes become traffic "hot-spots", potentially resulting in network congestion and single point of failure. Furthermore, restricting cluster to access through cluster-head nodes can lead to sub-optimal routes, as potential neighbors in different clusters are prohibited from communicating directly. Prior works did many researches on the formation of the clusters, especially how the cluster-head is elected or re-elected. Although [3]-[6] have proposed ideas to reduce the load of the CH by different methods, the CH still suffers. Moreover, no optimal routing protocol tailored for cluster-based ad hoc networks is proposed. Therefore, in this paper, we proposed a distributed gateways routing protocol for ad hoc networks, namely DGR. The proposed scheme can alleviate the burden of CHs and also achieve optimal routes. Moreover, it can provide flexibility for CH re-election when the prior CH powers off or moves off. A CH re-election can be postponed until a proper node claims to be a CH or the cluster is going to be split. Therefore, DGR can make clusters much more stable for mobility and make the average life time of nodes in the clusters much longer. In addition, we also proposed a cluster reformation criterion to avoid unnecessary cluster reformation. It can make clusters much more stable for nodes mobility under the proposed cluster reformation criteria. The paper is organized as follows. In section II we present the some definitions. In section III we discuss our proposed routing protocol and give a mathematical analysis on overhead and cluster stability of proposed routing protocol, and then followed by simulation results in section IV. Finally, we give a conclusion in section V. II.
DEFINITIONS
The following definitions will be frequently used in the following sections.
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2010 International Conference on Computer Application and System Modeling (ICCASM 2010)
A.
Definition 1 (system topology)
A.
The system topology is a dynamic undirected graph G = (V, E), where V is the set of the nodes, and E is the set of logical edges. A logical edge (x, y) means that node y is in the transmission range of x, and vice versa. We define N[v] to be the neighborhood of node v as follows:
N[v]=U{v'ldist(v,v')
