Hughes Electronics Corporation

Lockheed Martin Corporation

Daniel Albert Voce

Matthew Mohebbi

Faris Riyad Faris

Asha Mehrotra

John Fry

Asynchronous Transfer Mode (ATM) data is transmitted in Available Bit Rate (ABR) service over a network path including a spacecraft. The spacecraft payload switches do not provide an indication of congestion, so conventional ABR feedback control using Resource Management cells is ineffective. In one avatar of the invention, the Network Control Center coacting with the spacecraft produces signals representative of congestion in services other than ATM ABR service, and these congestion signals are coupled to the terrestrial source terminal, where return or back Resource Management cells are modified with data derived from the congestion signals, to close a feedback loop including the source of ATM ABR signals, the source terminal, and the spacecraft. The feedback loop tends to maintain excess bandwidth in use for ABR purposes, and tends to prevent congestion. In another embodiment, congestion information derived from locations downstream of the spacecraft are coupled in the upstream direction, through the spacecraft, by way of return RM cells. The spacecraft congestion information is combined with the upstream RM cell information and flows to the source of ABR service ATM data.

Available-bit-rate service in an asynchronous transfer mode based spacecraft network

A method and apparatus for determining the proper satellite communications service to be provided to a subscriber unit that may be integrated with the geographically defined service areas used in terrestrial cellular communications systems. The pre-existing geographically defined service areas are subdivided into quadrilateral tiles wherein each tile corresponds to a single service area. In addition, the tiles are mapped to a grid having a plurality of regularly spaced grid locations. A lookup table is created that references each grid location to the tiles that overlap the grid locations. The position of the subscriber unit and an approximated region of error within which the subscriber unit is likely to be located are used as input. The approximated region of error is mapped to the grid to identify the grid locations that align with the approximated region of error. Thereafter, the lookup table is accessed to identify the tiles associated with the aligning grid locations and the identified tiles are then used to identify the service area in which the subscriber unit is located so that the proper communications service may be provided. If necessary, geometrical point in polygon inclusion methods and ellipse and polygon intersection methods are used to more accurately identify the tiles of interest.

Earth tiling system for providing regional based service in a mobile satellite communication network

A method and apparatus for predicting when to perform spot beam and satellite handover in a mobile satellite communication network that uses the position of the mobile subscriber. The method and apparatus perform all calculations with respect to a satellite-based coordinate system, thereby eliminating the need to model the shape of the geometrically complex spot beams on the surface of the earth. The position of a mobile subscriber unit that initiates a call is tracked relative to a set of spot beam boundaries that are located equidistant between a first spot beam within which the subscriber unit is located at the time of call initiation and a set of adjacent spot beams. An interval during which the subscriber unit will cross over one of the boundaries is estimated. The spot beam into which the subscriber is traveling is identified, and the interval is adjusted until a desired level of accuracy has been achieved at which time the call is transferred from the first spot beam to the adjacent spot beam at the estimated time. For satellite handover, an angle of elevation between the subscriber unit and the satellite is calculated and compared to a threshold angle. When the angle of elevation drops below the threshold angle due to the movement of the satellite, the call is transferred from a first satellite to a neighboring second satellite.

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Germantown, MD, United States of America

Daniel Albert Voce