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    Apparatus for use in a satellite communications earth station using tdma channels
    92.
    发明专利
    Apparatus for use in a satellite communications earth station using tdma channels 未知

    公开(公告)号：IN192234B

    公开(公告)日：2004-03-20

    申请号：IN894MA1995

    申请日：1995-07-14

    Applicant: INMARSAT LTD

    Inventor： HART NICHOLAS ,  BJORNSTROM GUNNAR

    IPC: H04B7/185 ,  H04B7/204 ,  H04B7/00

    Abstract: An earth station (8) receives a return signal (3) via more than one satellite link (4a,4b) from a mobile terminal (2) using TDMA. The earth station (8) selects one or more of the satellite links (4a) for transmitting a forward signal (15) on the basis of the quality of signal (3;15) received via each link. The earth section (8) allocates frequency channels to the mobile terminals (2) according to their location on the surface of the earth, so that the propagation time to and from those mobile terminals (2) which share the same frequency channel is approximately the same. The satellite (4a;4b) includes an antenna which generates an array of beams which are individually pointed to fixed regions of the earth, until the elevation of the satellite (4a;4b) relative to a fixed region falls below a minimum value, in which case the corresponding beam is redirected to a new area, while the other beams remain pointed at the corresponding fixed areas. In this way, beam-to-beam handover is reduced, while maintaining the boresight of the antenna pointing at the radir.

    Carrier allocation
    94.
    发明专利
    Carrier allocation 未知

    公开(公告)号：GB2385491A

    公开(公告)日：2003-08-20

    申请号：GB0203682

    申请日：2002-02-15

    Applicant: INMARSAT LTD

    Inventor： DRAKOS EVRIPIDES

    IPC: H04B7/185 ,  H04W16/02 ,  H04W16/12 ,  H04Q7/36

    Abstract: In a carrier (or frequency) allocation scheme for a cellular communications system, cells are divided into groups of different types (CG1, CG2, CG3, CG4) and carriers (fxyz) are divided into sets (f1yz, f2yz, f3yz, f4yz,) allocated respectively to the different types. Carriers may be re-used between different groups of the same type, and optionally within a group, subject to a minimum re-use distance rule. The allocation patterns may be varied independently between different groups of the same type. The scheme may be adapted to the demand for carriers over a predetermined period. Different allocation schemes applied to different carriers may be overlaid on the same cells. Different allocation schemes may be applied to different cells, provided that the minimum re-use distance rule is obeyed between schemes. The scheme may be applied to spot beams of a satellite communications system, or cells of a terrestrial cellular system. In an alternative embodiment a method of allocating a plurality of carriers to a plurality of cells in a cellular communication system is described in which the allocation of at least one of the carriers is shared between two or more cells separated by less than a predetermined reuse distance according to a weighting factor (e.g. predicted load, predictability of the load and/or density of users in the cell) of each of the two or more cells.

    99.
    发明专利
    未知

    公开(公告)号：DE69626213D1

    公开(公告)日：2003-03-20

    申请号：DE69626213

    申请日：1996-11-04

    Applicant: INMARSAT LTD

    Inventor： TRACHTMAN EYAL

    IPC: H04N1/00 ,  H04N1/32 ,  H04N1/333 ,  H04N1/41 ,  H04N1/411 ,  H04Q7/20

    Abstract: An image interface circuit for compressing an image for subsequent transmission via a radio transmission channel, comprising; an image reception port; an image reception circuit for receiving an image from said image reception port in a first compressed signal format; an image decompression circuit for decompressing said first compressed signal format; an image segmenting circuit for segmenting the image into text and non-text areas; an optical character recogniser for recognising text characters in the text areas and generating corresponding character data; an image encoder circuit for compression-encoding the non-text areas into a image data in a second image signal format different to said first image format; a compressed image transmission port connected to said radio transmission channel, and; a signal combiner circuit for combining the character data and the image data into a combined signal and supplying the combined signal to the compressed image transmission port.

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