Investigations on opportunistic networking mechanisms in IEEE 802.15.4-based wireless mobile body sensor networks
Thesis DisciplineComputer Science
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
Neighbour discovery and message scheduling are two very important functions of wireless networks. This thesis explores these two domains of wireless networks. The first part of this work investigates the passive discovery of IEEE 802.15.4-based Body Sensor Networks (BSNs). The later part focuses on message scheduling in Opportunistic networks.
Wireless body sensor networks is an important research area in the field of health care. These networks aim to improve the well being and quality of life. BSNs are wearable networks that can monitor the vital functions of the body and alert the concerned health practitioners in case the status of any of the vital functions is abnormal. Since, these networks are wearable, they allow the person to roam around freely without having to deal with the clutter of the cables.
One challenging task that BSNs has to perform is to discover the target network or the coordinator nodes. This target network or the coordinator node can be a gateways where the BSN coordinator offload data for further processing and storage services.
This thesis presents a cooperative passive discovery scheme (the rumour-based scheme) for the beacon-enabled mode that is based on a simple class of listening strategies called sweep strategy for IEEE 802.15.4 based body sensor networks. The thesis investigates a simple scenario of unbounded targeted discovery where a specific mobile BSN is searching for a specific destination network. The performance of this scheme is evaluated in terms of the average discovery time using simulations. The results show that this scheme can significantly reduce the time required to discover the target network.
The next part of the thesis focuses on the a message scheduling algorithm for opportunistic network or Delay Tolerant Network (DTN). Opportunistic networks are characterized by having only intermittent connectivity on end- to-end paths due to highly mobile nodes. Due to this mobility, a successful delivery of messages becomes a real challenge for these network.
Message scheduling is a key part of an opportunistic routing and forwarding scheme. A node has needs to find the sequence in which it transmits messages reliably for further relaying to its various neighbours.
This thesis presents a scheduling scheme that incorporates the knowledge about the remaining contact time into the scheduling. The scheduler sorts the messages according to their priority and sizes. When a node comes in close contact with other node, the scheduler then messages are then sent while taking into account the remaining contact time left between the nodes. The performance of thesis scheme is compared against baseline schemes from the literature.
The results show that incorporating remaining contact time can indeed give substantial improvements in key performance indicators like the average delivery delay or the overhead ratio.