Abstract: In a cellular mobile telephone system, a mobile station (4d, 4e) requests allocation of a traffic channel by sending a request in a random access channel. Where there is a significant path length difference between locations in a cell and a network antenna, for instance on a satellite (3), not all of the available TDMA slots are used for random access signals. Instead, gaps of one to three time slots are left between valid random access time slots (103, 104) to avoid collision between random access bursts arriving at the network antenna along paths of different lengths.

Abstract: In a satellite mobile telecommunication system, TDMF traffic is transmitted from a SAN 1 via a satellite 3 to a mobile user terminal UT1, over a duplex link 1, 2. The SAN 1 instructs the satellite 3a to transmit signals over link 1 to UT 1 at a power level dependent upon the quality of signal received by UT 1, so as to adaptively control the power to an efficient level. Similarly, the power level of signals transmitted by UT 1 to the satellite is controlled depending on the error rate. The power level required is computed as a function of the average of easured areas determined during a given measurement period together with a margin which is computed as an adaptive function of a deviation of the errors bout the average value.

Abstract: A mobile telephone (UT 1) is configured for dual mode operation, so as to communicate either via an earth-orbiting satellite 3a with a satellite network (SAN 1) or through a conventional land-based cellular network (PLMN 9). In order to provide interworking between the satellite network and the land, cellular network 9, an interworking function (IWF 31) provides data to the cellular network 9 concerning the location of the user terminal (UT 1) in relation to the satellite network. The data is transmitted from the satellite visitor location register (VLRSAT 1) to the home location register (HLR) of the cellular network 9. The IWF maintains a list of roaming subscribers provisioned with services which are specific to the visited network and not available in the home network. The (IWF 31) is configured to operate with local GSM, DAMPS, PHS or other local land-based networks, depending on the geographic location of the SAN.

Abstract: In a preferred satellite (3) communications environment, spread spectrum communications, under extremes of digital message readability, is established for a digital message 23 by division into smaller elements W(0)-W(C−1) which are transmitted in turn, each multiplied for logical inversion or non-inversion, by the individual, sequential digits of a preferred binary polynomial 35, being either a PN polynomial, an m-polynomial, or simply displaying alternate logical ones and zeroes. The preferred polynomial may be used convey an alternative polynomial for better reception of a subsequent digital message.

Abstract: A mobile satellite communications system having at least one mobile terminal (2), at least one ground station (6), at least one relay satellite (4) interconnecting said user terminal (2) and said ground station (6), and a management store (48) associated with said ground station (6), in which the user terminal (2) is configured to initiate registration signalling with said store (48). The user terminal (2) initiates registration signalling when reception conditions relating to a downlink channel relayed via said satellite (4) become unsatisfactory over a given time greater than a predetermined minimum value and then return to a satisfactory condition. Specifically, signals received in a given channel are monitored in relation to predetermined criteria, and the duration of periods when the monitored signals do not meet the criteria are timed.

Abstract: A satellite system and method comprises a satellite 10 induced to roll 46 and pitch 52 in its orbit 12 to keep antennae 34 36 pointing ever directly at the nadir 40 as the nadir moves over the surface of the earth 14. The satellite 10 has a yaw rotation 54 designed to keep the solar panels, which rotate only about one axis, ever pointing at ninety degrees to the direction of the sun 42 for maximum solar panel efficiency. The beam pattern of the antennae 34 36 is counter-rotated to oppose the yaw motion 54. Compensation for the season of the year is applied.