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 method of transmission comprises receiving at a first destination, a transmission from a first source; determining from the transmission from the first source, the maximum permitted additional interference subject to which the first destination can still communicate; sending an acknowledgement of the transmission and including in the acknowledgement an indication of the determined maximum permitted additional interference. A second source determines whether it has received the transmission from the first source, or the acknowledgement from the first destination, at a power level lower than that of the maximum permitted additional interference given in the indication; and if so, the second source sends a transmission to a second destination, which at least partially overlaps in time, communication between the first source and first destination.

Abstract: A method of controlling interference from a transmitter (4) in one communication system to a receiver (1) in another communication system, the method comprising transmitting a beacon (3) beacon from a beacon transmitter associated with the receiver representative of a frequency at which the receiver is trying to receive; listening for the beacon at a beacon receiver associated with the transmitter; and deriving a power spectral density limit for a transmission (2) from the transmitter based upon the strength of the beacon received at the beacon receiver.

Abstract: A phased array radar comprises a first array (2) of detectors (6) in a first dimension; and a second array (1) of detectors (6) in a second, orthogonal, direction. The first array of detectors both transmits (8) and receives (9) and the second array of detectors only receives (7). The first array resolves in range and either azimuth, or elevation; whereas the second array is a staring array that stares at targets at specified ranges determined by the first array, and the second array resolves in the other of elevation or azimuth, accordingly.

Abstract: A method of spectrum sharing comprises determining a first frequency in a first location area (30) for a channel (15) of a first transmission type; and choosing a second frequency for a channel (1) of a second transmission type on which to transmit in the first location area; wherein the second frequency differs from the first frequency by at least two frequency channels of the first transmission type.