Ad hoc and Opportunistic Routing in Static Scatternet Environment

Abstract Peer-to-peer connectivity between mobile phones using technologies such as Bluetooth has given a new dimension to the mobile communication. Peers through the help of various underlying protocols can form piconets and scatternets to transparently communicate the content across the network. There however are issues like reliability in communication, delay and the cost of communication that need to be considered before resorting to this form of communication. This paper presents a study where opportunistic concept such as Bubble Rap is tested in Bluetooth ad hoc networking environment. The notion behind this research is to study the properties of these two networking environments, since opportunistic networks are derived from ad hoc networks. Thus, study of these two different environments yet related to each other may help us find new ways of message forwarding in Bluetooth communication environment. This paper is aimed at investigating the behaviour of nodes present in Bluetooth static scatternet environment by 1) studying message transfer from a source to destination using traditional ad hoc communication protocols such as AODV and 2) message transfer using opportunistic algorithms such as Bubble Rap on top of traditional ad hoc communication. This paper also proposes a concept of ranking to transfer messages to the node that has higher social centrality ranking compared to the current node. Nodes with varying social ranking are allowed to join piconets and forward messages based on Bubble Rap concept in scatternet environment. In BR algorithm, nodes forward messages to only those encountering nodes which are more popular than the current node

MFACE: A Multicast Backbone-Assisted Face Traversal Algorithm for Arbitrary Planar Ad Hoc and Sensor Network Topologies

Face is a well-known localized routing protocol for ad hoc and sensor networks which guarantees delivery of the message as long as a path exists between the source and the destination. This is achieved by employing a left/right hand rule to route the message along the faces of a planar topology. Although face was developed for the unicast case, it has recently been used in combination with multicasting protocols, where there are multiple destinations. Some of the proposed solutions handle each destination separately and lead thus to increased energy consumption. Extensions of face recovery to the multicast case described so far are either limited to certain planar graphs or do not provide delivery guarantees. A recently described scheme employs multicast face recovery based on a so called multicast backbone. A multicast backbone is a Euclidean spanning tree which contains at least the source and the destination nodes. The idea of backbone assisted routing it to follow the edges of the backbone in order to deliver a multicast message to all spanned destination nodes. The existing backbone face routing scheme is however limited to a certain planar graph type and a certain backbone construction. One of the key aspects of the multicast face algorithm MFACE we propose in this work is that it may be applied on top of any planar topology. Moreover, our solution may be used as a generic framework since it is able to work with any arbitrary multicast backbone. In MFACE, any edge of the backbone originated at the source node will generate a new copy of the message which will be routed toward the set of destination nodes spanned by the corresponding edge. Whenever the message arrives at a face edge intersected by a backbone edge different from the initial edge, the message is split into two copies, both handling a disjoint subset of the multicast destinations which are defined by splitting the multicast backbone at that intersection point

Geometry-Experiment Algorithm for Steiner Minimal Tree Problem

It is well known that the Steiner minimal tree problem is one of the classical nonlinear combinatorial optimization problems. A visualization experiment approach succeeds in generating Steiner points automatically and showing the system shortest path, named Steiner minimum tree, physically and intuitively. However, it is difficult to form stabilized system shortest path when the number of given points is increased and irregularly distributed. Two algorithms, geometry algorithm and geometry-experiment algorithm (GEA), are constructed to solve system shortest path using the property of Delaunay diagram and basic philosophy of Geo-Steiner algorithm and matching up with the visualization experiment approach (VEA) when the given points increase. The approximate optimizing results are received by GEA and VEA for two examples. The validity of GEA was proved by solving practical problems in engineering, experiment, and comparative analysis. And the global shortest path can be obtained by GEA successfully with several actual calculations

Asynchronous Local Construction of Bounded-Degree Network Topologies Using Only Neighborhood Information

We consider ad-hoc networks consisting of $n$ wireless nodes that are located on the plane. Any two given nodes are called neighbors if they are located within a certain distance (communication range) from one another. A given node can be directly connected to any one of its neighbors and picks its connections according to a unique topology control algorithm that is available at every node. Given that each node knows only the indices (unique identification numbers) of its one- and two-hop neighbors, we identify an algorithm that preserves connectivity and can operate without the need of any synchronization among nodes. Moreover, the algorithm results in a sparse graph with at most $5n$ edges and a maximum node degree of $10$. Existing algorithms with the same promises further require neighbor distance and/or direction information at each node. We also evaluate the performance of our algorithm for random networks. In this case, our algorithm provides an asymptotically connected network with $n(1+o(1))$ edges with a degree less than or equal to $6$ for $1-o(1)$ fraction of the nodes. We also introduce another asynchronous connectivity-preserving algorithm that can provide an upper bound as well as a lower bound on node degrees.Comment: To appear in IEEE Transactions on Communication

Partial Delaunay Triangulation and Degree Limited Localized Bluetooth Scatternet Formation

This paper addresses the problem of localized scatternet formation for multi-hop Bluetooth based personal area ad hoc networks. Nodes are assumed to know their positions and are able to establish connections with any of their neighboring nodes, located within their transmission radius, in the neighbor discovery phase. The next phase of the proposed formation algorithm is optional, and can be applied to construct a sparse geometric structure in a localized manner. We propose here a new sparse planar structure, namely, partial Delaunay triangulation (PDT), which can be constructed locally and is denser than other known localized structures. In the next mandatory phase, the degree of each node is limited to 7 by applying the Yao structure, and the master-slave relations in piconets are formed in created subgraphs. This phase consists of several iterations. In each iteration, undecided nodes with higher keys than any of their undecided neighbors apply the Yao structure to bound the degrees, decide master-slave relations on the remaining edges, and inform all neighbors about either deleting edges or master-slave decisions. To the best of our knowledge, our schemes are the first schemes that construct degree limited (a node has at most 7 slaves) and connected piconets in multi-hop networks, without parking any node. The creation and maintenance require small overhead in addition to maintaining accurate location information for one-hop neighbors. The experiments confirm good functionality of created Bluetooth networks in addition to their fast creation and straightforward maintenance

Message forwarding techniques in Bluetooth enabled opportunistic communication environment

These days, most of the mobile phones are smart enough with computer like intelligence and equipped with multiple communication technologies such as Bluetooth, wireless LAN, GPRS and GSM. Different communication medium on single device have unlocked the new horizon of communication means. Modern mobile phones are not only capable of using traditional way of communication via GSM or GPRS; but, also use wireless LANs using access points where available. Among these communication means, Bluetooth technology is very intriguing and unique in nature. Any two devices equipped with Bluetooth technology can communicate directly due to their unique IDs in the world. This is opposite to GSM or Wireless LAN technology; where devices are dependent on infrastructure of service providers and have to pay for their services. Due to continual advancement in the field of mobile technology, mobile ad-hoc network seems to be more realised than ever using Bluetooth. In traditional mobile ad-hoc networks (MANETs), before information sharing, devices have partial or full knowledge of routes to the destinations using ad-hoc routing protocols. This kind of communication can only be realised if nodes follow the certain pattern. However, in reality mobile ad-hoc networks are highly unpredictable, any node can join or leave network at any time, thus making them risky for effective communication. This issue is addressed by introducing new breed of ad-hoc networking, known as opportunistic networks. Opportunistic networking is a concept that is evolved from mobile ad-hoc networking. In opportunistic networks nodes have no prior knowledge of routes to intended destinations. Any node in the network can be used as potential forwarder with the exception of taking information one step closer to intended destination. The forwarding decision is based on the information gathered from the source node or encountering node. The opportunistic forwarding can only be achieved if message forwarding is carried out in store and forward fashion. Although, opportunistic networks are more flexible than traditional MANETs, however, due to little insight of network, it poses distinct challenges such as intermittent connectivity, variable delays, short connection duration and dynamic topology. Addressing these challenges in opportunistic network is the basis for developing new and efficient protocols for information sharing. The aim of this research is to design different routing/forwarding techniques for opportunistic networks to improve the overall message delivery at destinations while keeping the communication cost very low. Some assumptions are considered to improved directivity of message flow towards intended destinations. These assumptions exploit human social relationships analogies, approximate awareness of the location of nodes in the network and use of hybrid communication by combining several routing concept to gain maximum message directivity. Enhancement in message forwarding in opportunistic networks can be achieved by targeting key nodes that show high degree of influence, popularity or knowledge inside the network. Based on this observation, this thesis presents an improved version of Lobby Influence (LI) algorithm called as Enhanced Lobby Influence (ELI). In LI, the forwarding decision is based on two important factors, popularity of node and popularity of node’s neighbour. The forwarding decision of Enhanced Lobby Influence not only depends on the intermediate node selection criteria as defined in Lobby Influence but also based on the knowledge of previously direct message delivery of intended destination. An improvement can be observed if nodes are aware of approximate position of intended destinations by some communication means such as GPS, GSM or WLAN access points. With the knowledge of nodes position in the network, high message directivity can be achieved by using simple concepts of direction vectors. Based on this observation, this research presents another new algorithm named as Location-aware opportunistic content forwarding (LOC). Last but not least, this research presents an orthodox yet unexplored approach for efficient message forwarding in Bluetooth communication environment, named as Hybrid Content Forwarding (HCF). The new approach combines the characteristics of social centrality based forwarding techniques used in opportunistic networks with traditional MANETs protocols used in Bluetooth scatternets. Simulation results show that a significant increase in delivery radio and cost reduction during content forwarding is observed by deploying these proposed algorithms. Also, comparison with existing technique shows the efficiency of using the new schemes