Abstract: Groupings of receivers for determining a target location by a multilateration system are selected to give the best geometric dilution of precision result by eliminating the receiver that makes the greatest contribution to such dilution. In this way the groups to be used may be selected as appropriate for the location of the target in real time, avoiding the requirement to have a database holding the groupings to be used.

Abstract: A communication system for the mutual interconnection of a plurality of lower traffic level (5 Terabit) switch nodes via a relatively higher traffic level (Petabit) connection bus, which system comprises in operative association with each node, a two part TDM optical data management interface, wherein a first of the two parts comprises a time slot resequencer which serves to provide for the transmission of data from its associated node to the bus, and wherein a second of the two parts comprises a time slot specific combiner which serves for the transmission of data from the bus to its associated node, each node and the bus having independent data scheduling.

Abstract: A method of improving the flow of data in a communication system having at least two links, comprising inserting into one of said links at least one enhancer, the operation of which is to a) communicate with a the unit upstream of the data flow such that the upstream unit perceives that it is communicating with the unit (s) downstream of the enhancer; b) obtaining a measure of the efficacy of operation of the down stream unit(s), and c) dependent upon the measure, varying the control of data flow sent to downstream units.

Abstract: In a multilateration system receivers are grouped into two groups. The first group is used to determine a position of a signal source, for example, an aircraft equipped with a SAR transponder. From the determined position, predicted time of arrival values are produced for the second group receivers. These are compared with the actual time of arrival values for the signals arriving at the second group receivers. A difference is determined and then the variation of that difference is determined as the aircraft travels in its track. The groupings are then varied and further variations determined. When the minimum variation is determined an alert is given that the second group has a receiver which is operating with a larger than desirable group time delay.

Abstract: A method of filtering high data rate traffic (2) based on its content, the method comprising identifying candidate fixed size partial strings (3) within the traffic; comparing characters within the candidate partial string with a content addressable memory (1) containing wanted partial string values and identifying matching traffic; wherein the partial string content includes at least one anchor character (7); wherein the partial string size is set to a predetermined number of characters adjacent to the anchor character; and, wherein partial strings ending in an anchor character are compared with wanted partial string values in the content addressable memory.

Abstract: A method of determining reliability of information received at a destination (16) in a communication network sent from a source with which the destination does not have a security association comprises generating first and second data (12, 13) representative of the information at the source. The first data is sent down a first route (14) from the source to the destination and the second data is sent down a second route (15) from the source to the destination. At the destination, received data that has been sent via the first and second routes (14, 15) is compared. Information is regenerated from the received data and the reliability of the information is determined from the result of the comparison of the received data.

Abstract: The present invention provides methods and apparatus for MIMO communications across wireless fixed links, comprising a first pair of dual polar antennas, spaced apart in a direction orthogonal to the direction of the fixed link for transmission, and a second such pair for reception, wherein orthogonal polarisations of one of each pair of antennas are oriented intermediate between the orthogonal polarisations of the other of each pair of antennas.

Abstract: In the apparatus a RADAR transmitter and receiver array are provided which see different aspects of a target by virtue of their configuration. The transmitter transmits RADAR signals based on mutually orthogonal codes. There are two preferred forms of transmitter and receiver arrays.

Abstract: A method is provided for controlling a clock for use in a frequency source. In the method a time bias is determined by determining the Accumulated Doppler Range of a signal source at different time intervals. The drift of a local clock is determined by determining the difference between the different time intervals and the clock may then be corrected. Apparatus is also provided and the invention has particular application to a multilateration system.

Abstract: Groupings of receivers to be used for determining a target location by a multilateration system are selected to give the best Geometric Dilution of Precision result by eliminating that receiver that makes the greatest contribution. In this way the groups to be used may be selected as appropriate for the location of the target in real time avoiding the requirement to have a database holding the groupings to be used.

Abstract: The present invention provides methods and apparatus for optimising power consumption in transistor amplifiers. The method comprises the step of adapting the amplifier characteristics of the transistor by adapting the bias impedance at the base of the transistor. The method may further comprise the step of adapting the amplifier characteristics of the transistor by adapting the quiescent collector current in the transistor.

Abstract: To cater for the positioning of an aircraft in a boundary zone between two adjacent multilateration systems, the controller (14) in one system receives Time Difference of Arrival data provided by the controller (15) in the second system. The controller (15) derives the TDoA data from time of arrival data provided by its receiver stations (9-13). By furnishing TDoA data the timings of the two systems do not need to be synchronised. The controller (14) uses the TDoA data and also time of arrival data from its local receiver stations (4-8) to perform a multilateration to determine the location of the aircraft (16).

Abstract: A method of searching for one or more patterns in a text using Boyer-Moore methodology, including the step of wherein once a match of an ngram is determined, entering into a routine which jumps forward so as to compare more initial characters so as to provide faster rejection.

Abstract: Described herein is a method of controlling data flow between a local network (120) and a remote network (30) via a geostationary satellite link (40, 46, 48). The local network (120) comprises a sending host (22) and a connection splitting node (124) which includes a throttling unit (150). The remote network (30) comprises a receiving host (32) which is connected to a second connection splitting node (142) having a buffer (152) via the internet (34). The data flow rate from the local network (120) is throttled to provide a data flow rate which substantially matches that which can be handled by the remote network (30) so that the buffer (152) at the second connection splitting node (142) is not overfilled.

Abstract: The invention comprises a method of constructing an Aho-Corasick tree characterised wherein the tree is constructed in a general depth first manner, one string at a time. Preferably during construction of said string, after each node is added, failure links or extended failure links from that node to other nodes are added and failure links to nodes in the newly inserted branch are re-updated.

Abstract: A method of calibrating an adaptive antenna array that applies beamsteering (1) of a satellite navigation system comprises receiving signals from a plurality of satellites at a plurality of receivers (2) within the system. The satellite direction relative to the antenna array orientation for each satellite signal is determined (5); and the received signals are despread (8) to recover satellite signals. Gain and phase information is calculated from the despread code for a given satellite in a given direction; and the calculated gain and phase information are stored in a manifold store (4) at a predetermined address related to the direction of arrival of the satellite signal.

Abstract: An audio recording system comprises an array of microphones and a processor module. The array is a logarithmic spiral array in which the minimum distance between each microphone and all others that lie closer to the centre is maximised. The processor module further comprises a beam direction control device and a beam width control device; whereby an audio target is isolated.

Abstract: A method of communication in a time division duplex (TDD) satellite communication system comprising at least one satellite and a plurality of terrestrial terminals comprises allocating time division multiple access (TDMA) time slots for transmission between the satellite and any one of the plurality of terminals, such that for any given terminal, transmit time slots for transmission to the satellite and receive time slots for reception from the satellite are separated in time. An assigned time delay between transmit and receive time slots at the any one terminal is small compared with a round trip propagation delay and if the transmit time slot for one terminal causes a transmission from that one terminal to be received at another terminal overlapped in time with a receive time slot allocated for the other terminal, then those two terminals are spaced apart in distance, sufficiently, such that interference between the two terminals is minimised.

Abstract: A security camera system is provided. Several video cameras operate in conjunction with an image display monitor, a user control and camera selector means whereby a target of interest may be followed. Each two cameras providing adjacent areas of coverage are operable to provide an overlay image portion at transition regions of a displayed image. Upon movement of the target of interest to a specified transition region of a currently displayed image provided by one video camera, the camera selection means is operable to select a second camera whereby to maintain target display continuity by the monitor.

Abstract: A method of associating the Training code to a Channelisation code in a mobile telecommunications system. The method includes associating a Training code with a Channelisation code prior to transmission according to a set of rules such that upon detection of the Training code by a receiver, the Channelisation code is known.