British Telecommunications Public Limited Company

Richard E Tateson

Fabrice T P Saffre

Jane E Tateson

Christopher Simon Winter

Paul M Coker

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

Wireless devices in (etc) in an ad hoc network each select a channel on which to operate such that conflicts with neighbouring devices are avoided. Each device () has a normal power output, giving it a normal range () and an enhanced power output, giving it an extended 'inhibition' range (). Initially each device () transmits at the enhanced power level, such that it can be detected by devices () within the extended range (). If it detects other devices transmitting on the same channel, it may change to another channel. Once a channel has been identified on which no conflict is detected, the device () switches to the normal power level. By initiating the channel selection process at the enhanced level, conflicts between the transmissions of devices (), which would be detectable at a device () within the normal range of both, can be avoided despite the two devices () not be able to detect each other directly at the normal power level. To conserve battery power, the process is arranged to have the devices operate at the enhanced power for the minimum time necessary, by dropping to the normal level when a suitable channel has been identified with a reasonable degree of certainty.

Channel selection

A method of sorting large quantities of data is implemented on a computer based system. The method comprises defining a plurality of sort statements, determining the relevance of each of the sort statements to each data file in the database, defining a site on a display for each of the sort statements, representing the data files as elements on the display, and causing the elements to move from an initial position towards the sites according to the relevance of the respective sort parameters to the respective data files and the position of the sites relative to the respective elements.

Data selection system and method therefor

Each base station in a network has an antenna which is connected in the conventional way to a transceiver for handling normal call traffic on one or more radio channels. In addition there is another transmitter which transmits a test signal on each of several test channels, one for each radio channel available for use by the main transceiver. The transceiver also has a receiver for detecting the test channels. The system is controlled by a timer which ensures that the transmitter and receiver do not operate at the same time. The receive times may be random, or may be co-ordinated between individual base stations. When the receiver is in operation, it will detect transmissions of the test signals from other base stations. The signal strength is measured and the result is used by a control system to determine a preference value for each channel; the stronger the signal detected, the lower the preference value. The preference value is used to control an amplifier system which controls the signal strength of each channel transmitted by the transmitter. It is also used to control the traffic transceiver by selecting which traffic channels are to be used in accordance with the preference values.

Allocation of channels to radio transceivers

A channel allocation process for a cellular telephone network starts from a position of homogeneity in which each base station has the potential to use all channels. It develops ever greater heterogeneities by processing a combination of short and medium range interactions between the base stations themselves, causing each base station of the cellular telephone network to inhibit its neighbors from using a given channel, to generate a usage factor for each channel in each cell indicative of the level of interference to be expected on that channel in that cell. Channels can then be allocated to each base station according to the ranking of the usage factors determined for the channels at that base station. The entire network may be emulated by a single processor, controlling the base stations of the network in accordance with the results of the process. Alternatively, each base station of the network performs that part of the process relating to itself, in co-operation with its neighbors, and utilizes channels in accordance with results.

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Wickham Market, United Kingdom

Richard E Tateson