Tree-shaped Topology Research Articles

Joint topology control and routing design for reconfigurable ring-tree networks

This paper presents a joint topology control and routing design of reconfigurable ring-tree (RRT) topology for Bluetooth non-uniform networks. The non-uniform network consists of one dense and many other sparse regions. In the dense area, the RRT builds a ringshaped topology as a backbone subnet in a distributive manner, which is expanded by a treeshaped topology to other more sparse areas. For various sizes of networks, the size of the ring subnet is controlled by the trade-off between the network performance and the construction cost. Because corresponding nodes in the ring subnet do not procure the global computation situations, obtaining the optimal ring size is an NP-complete problem. In seeking to finalise the optimum ring size, an empirical max-search strategy is provided to attain the preferred cost-performance ratio. The max-search strategy is a methodical decision policy, carried out by three working elements: the topology construction, the packet routing and the maximum decision elements. The topology construction element engenders the ring-tree topology, the packet routing element processes the routing performance with a uniform traffic model, and the maximum decision element utilises a decision-making criterion to discover the optimum ring size. Experimental values demonstrate that the optimum ring size can be resolved by the max-search scheme for various sizes of networks, and the RRT delivers a better throughput performance than that of the conventional BlueHRT and Bluetree networks.

A Reconfigurable Formation and Disjoint Hierarchical Routing for Rechargeable Bluetooth Networks

In this paper, a reconfigurable mesh-tree with a disjoint hierarchical routing protocol for the Bluetooth sensor network is proposed. First, a designated root constructs a tree-shaped subnet and propagates parameters k and c in its downstream direction to determine new roots. Each new root asks its upstream master to start a return connection to convert the first tree-shaped subnet into a mesh-shaped subnet. At the same time, each new root repeats the same procedure as the designated root to build its own tree-shaped subnet, until the whole scatternet is formed. As a result, the reconfigurable mesh-tree constructs a mesh-shaped topology in one densely covered area that is extended by tree-shaped topology to other sparsely covered areas. To locate the optimum k layer for various sizes of networks, a peak-search method is introduced in the designated root to determine the optimum mesh-tree configuration. In addition, the reconfigurable mesh-tree can dynamically compute the optimum layer k when the size of the network changes in the topology maintenance phase. In order to deliver packets over the mesh-tree networks, a disjoint hierarchical routing protocol is designed during the scatternet formation phase to efficiently forward packets in-between the mesh-subnet and the tree-subnet. To achieve the energy balance design, two equal disjoint paths are generated, allowing each node to alleviate network congestion, since most traffic occurs at the mesh-subnet. Simulation results show that the joint reconfigurable method and routing algorithm generate an efficient scatternet configuration by achieving better scatternet and routing performance than BlueHRT (bluetooth hybrid ring tree). Furthermore, the disjoint routing with rechargeable battery strategy effectively improves network lifetime and demonstrates better energy efficiency than conventional routing methods.

Virtual Tree: A robust architecture for interval valid queries in dynamic distributed systems

This paper studies the problem of answering aggregation queries, satisfying the interval validity semantics, in a distributed system prone to continuous arrival and departure of participants. The interval validity semantics states that the query answer must be calculated considering contributions of at least all processes that remained in the distributed system for the whole query duration. Satisfying this semantics in systems experiencing unbounded churn is impossible due to the lack of connectivity and path stability between processes. This paper presents a novel architecture, namely Virtual Tree, for building and maintaining a structured overlay network with guaranteed connectivity and path stability in settings characterized by bounded churn rate. The architecture includes a simple query answering algorithm that provides interval valid answers. The overlay network generated by the Virtual Tree architecture is a tree-shaped topology with virtual nodes constituted by clusters of processes and virtual links constituted by multiple communication links connecting processes located in adjacent virtual nodes. We formally prove a bound on the churn rate for interval valid queries in a distributed system where communication latencies are bounded by a constant unknown by processes. Finally, we carry out an extensive experimental evaluation that shows the degree of robustness of the overlay network generated by the virtual tree architecture under different churn rates.

Enhanced Bluetree: a mesh topology approach forming Bluetooth scatternet

This study presents the enhanced Bluetree, a mesh topology scheme for Bluetooth scatternet formation. The scatternet formation algorithm includes two phases. In the first phase, a root node begins to create a conventional tree-shaped topology. To improve the network reliability of tree topology, a return connection mechanism is introduced in the second phase to generate more connection paths and to convert the tree-shape into a mesh-shaped topology. The mechanism contains two connection models including the ‘slave/slave mesh’ (SSM) and the ‘master/slave mesh’ (MSM) models. The SSM model builds a mesh-shaped topology by interconnecting more leaf nodes, whereas the MSM model connects additional intermediate nodes to establish the backbone connection in a mesh-shaped topology. Simulation results show that the enhanced Bluetree effectively improves the performance metrics, including the piconet efficiency, path length and end-to-end delay, beyond the Bluetree with more formation packets. As a result, the enhanced Bluetree not only builds a mesh-shaped topology that improves the network reliability but also generates an efficient network with less packet delay performance than a conventional Bluetree network.

A Mesh Topology Approach for Bluetooth Scatternet Formation

This paper presents the Enhanced Bluetree, a mesh topology scheme for Bluetooth scatternet formation. The scatternet formation algorithm includes two phases. In the first phase, a designated node called the root starts to create a tree-shaped topology and in the second phase the tree-shaped topology is converted into a mesh-shaped topology. In addition, a return connection mechanism is introduced in this phase to generate more connection paths among the nodes. The mechanism contains two scatternet topology models including the slave/slave mesh (SSM) model and the master/slave mesh (MSM) model. The SSM Model builds a mesh-shaped topology by interconnecting more leaf nodes. On the other hand, the MSM Model connects additional intermediate nodes to establish the backbone connection in a mesh-shaped topology. Simulation results show that both the SSM and the MSM of an Enhanced Bluetree more effectively improve the network performance than Bluetree by significantly reducing the average path length.

HMT: A Hybrid Mesh Tree Algorithm in Forming Bluetooth Networks

In this letter, a new scatternet formation algorithm called hybrid mesh tree for Bluetooth ad hoc networks was proposed. The hybrid mesh tree constructs a mesh-shaped topology in one dense area that is extended by tree-shaped topology to the other areas. First, the hybrid mesh tree uses a designated root to construct a tree-shaped subnet, and then propagates a constant k in its downstream direction to determine new roots. Each new root then asks its upstream master to start a return connection procedure to convert the first tree-shaped subnet into a mesh-shaped subnet. At the same time, each new root repeats the same procedure as the designated root to build its own tree-shaped subnet until the whole scatternet is formed. Simulation results showed that the hybrid mesh tree achieved better network performance than Bluetree and generated an efficient scatternet configuration for various sizes of Bluetooth scatternets.

Peer-to-peer systems for discovering resources in a dynamic grid

The convergence of the Grid and Peer-to-Peer (P2P) worlds has led to many solutions that try to efficiently solve the problem of resource discovery on Grids. Some of these solutions are extensions of P2P DHT-based networks. We believe that these systems are not flexible enough when the indexed data are very dynamic, i.e., the values of the resource attributes change very frequently over time. This is a common case for Grid metadata, like CPU loads, queue occupation, etc. Moreover, since common requests for Grid resources may be expressed as multi-attribute range queries, we think that the DHT-based P2P solutions are poorly flexible and efficient in handling them. In this paper we present two P2P systems. Both are based on Routing Indexes, which are used to efficiently route queries and update messages in the presence of highly variable data. The first system uses a tree-shaped overlay network. The second one is an evolution of the first, and is based on a two-level hierarchical network topology, where tree topologies must only be maintained at the lower level of the hierarchy, i.e., within the various node groups making up the network. The main goal of the second organization is to achieve a simpler maintenance of the overall P2P graph topology, by preserving the good properties of the tree-shaped topology. We discuss the results of extensive simulation studies aimed at assessing the performance and scalability of the proposed approaches. We also analyze how the network topologies affect the propagation of query and update messages.