British Telecommunications Public Limited Company

British Telecommunications Corporation

Jane E Tateson

Mark A Shackleton

Ian W Marshall

Fabrice T P Saffre

David J T Heatley

Christopher M Roadknight

Richard E Tateson

Catherine White

An apparatus according to the present invention comprises a chamber into which carbon nanotubes dispersed in a non-polar solvent may be received. The nanotubes are impelled along the chamber by the application of an external electrical field and will pass through a charging element that imposes an electrical charge on the nanotubes, and a template (), such that the nanotubes are deposited on a substrate located next to the template. The substrate may be moved relative to the template such that the nanotubes are deposited on the substrate in a predetermined selective manner.

Apparatus for selective deposition of nanotubes, using a charging element, a template and a filter

A number of data relay devices, e.g. mobile telephones, (), are conveyed by vehicles and move relative to each other. They form a vehicular ad hoc wireless network (), etc in which data stored by a device () (either own-generated or relayed from another device () is transmitted either directly or by means of one or more other devices () to a network access point () which interfaces with a cellular network. When two devices () come into proximity to each other, they use an opportunistic routing algorithm to determine a forwarding direction for the data. A retransmit timer is triggered on transmission of data, and messages which are unacknowledged at the expiry of the timer period are retransmitted. The timer period dynamically follows local congestion conditions and is recalculated at each transmission by the expression, timer minimum period/recent forwarding success(t). The current recent forwarding success at time t, RFS(t), is calculated from the RFS(t&#x2212;1) calculated for the immediately preceding transmission and from the current forwarding success, CFS, by the expression RFS(t)=4/5 RFS(t&#x2212;1)+1/5 CFS(t) where CFS is the square of the ratio of the available buffer space in the target device to the size of the payload in the source device.

Ad hoc communication system

The present invention relates to channel selection in ad hoc wireless networks. The present invention provides a method of selecting a channel for a node in an ad hoc network of nodes, the method comprising: increasing a preference score for a channel (E) in response to receiving a stimulatory control message (hoot x) associated with the channel from another node; decreasing the preference score for the channel (A) in response to receiving an inhibitory control message (hoot y) associated with the channel from another node; selecting a channel dependent on the preference score for the channel.

Channel selection in ad hoc wireless network

A plurality of mobile sensor devices each periodically measure a property of their environment, and determine the rate of change in that property. Neighboring devices also co-operate to determine the values of the property being measured by each other. If the property is invariant both over time and over a number of neighboring devices, their periodicity of measurement-taking is reduced to conserve power for more significant measurement events. The devices may co-operate to relay their measurements to a data collection point. Each device determines the level of data traffic being carried by one or more neighboring devices, identifies the device that is carrying the least traffic, and puts itself under the control of that device. Any device that determines that it is carrying less such traffic than any of its neighbor assumes control of the data sensing rate for itself and those neighbor, and transmits control data to the said other devices to co-ordinate their data collection rates and stagger their data collection times.

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The present invention relates to a sensing system, in particular to sensing system for sensing undersea seismic events. A vibration sensor is provided for sensing seismic vibrations on the sea bed is provided. The vibration sensor is electrically coupled to a transmitter unit, the transmitter unit being arranged to transmit, in use, an acoustic wave from which the presence of a seismic vibration can be inferred. The acoustic wave modulates light travelling along a nearby optical cable, the modulation being recovered at a distant monitoring station. A flotation arrangement is provide for retaining the transmitter unit in a raised position relative to the sea bed to facilitate the coupling of the acoustic wave to the optical cable.

Sensing system

A number of data collection devices are free to move relative to each other through their environment, collecting data from their environment. They form an ad hoc wireless network in which data collected by a device either by its own sensors, or relayed from another device is transmitted to a destination either directly or by means of one or more other devices. The destination collects data collected by the mobile terminals for subsequent processing. The wireless links between them have to be re-arranged in order to provide the optimum network. When two devices come into proximity to each other, a forwarding direction is determined to identify to which device data should be forwarded. The devices co-operate to define their forwarding directions by exchanging data relating to their physical locations, and factors such as the spare capacity of their buffer stores, and battery condition. Thus a network will be defined dynamically, each device having its forwarding direction aimed in the direction of the next device until they reach a sink.

Ad hoc communications system

A routing protocol scatters a stream of packets along a number of parallel paths, the packets being treated independently. The next hop for each packet is chosen probabilistically by comparing the 'resistance' of available options. The resistance of a given hop depends upon the time the packet would spend in an output buffer from the current node, the time the packet would spend in the input buffer of the next hop node, the transfer time between the nodes and the number of hops that the packet would take from the current node to the ultimate destination of the packet using the shortest path. This routing protocol is more efficient that shortest path first routing under simulation.

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Woodbridge, United Kingdom

Jane E Tateson