Low-cost satellite communication system
First Claim
1. A communication system comprising:
- a satellite having a high-gain antenna configured with a field of view that sweeps a service area on a planet in a first direction during a sweep period, wherein the field of view covers less than the entirety of the service area in the first direction and the field of view covers the entirety of the service area in a second direction perpendicular to the first direction, and wherein the sweep period is the amount of time it takes the field of view of the antenna to be swept across the service area in the first direction;
a plurality of remote terminal units, each including a respective transmitter configured to transmit a transmission message to the satellite during an illumination period in which the transmitter is within the field of view of the high-gain antenna, wherein the illumination period is a fraction of the sweep period and wherein the duration of the transmission message is less than the illumination period; and
a ground station configured to receive one or more retransmission messages corresponding to one or more transmission messages transmitted by a respective one or more of the plurality of remote terminal units,wherein a respective one of a plurality of direct sequence spread spectrum codes is allocated to each of the plurality of remote terminal units, and the respective transmitter of each of the plurality of remote terminal units is configured to transmit in accordance with the corresponding allocated direct sequence spread spectrum code, andwherein the respective transmitter of a first one of the plurality of remote terminal units is configured to transmit in accordance with a particular direct sequence spread spectrum code and the respective transmitter of a second one of the plurality of remote terminal units is configured to also transmit in accordance with the same particular direct sequence spread spectrum code.
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Accused Products
Abstract
A communication system is provided that allows the use of low-cost, low-power remote terminal units that communicate substantially asynchronously and independently to a base station. To minimize cost and complexity, the remote terminal units are configured similarly, including the use of substantially identical transmission schemes, such as a common Direct Sequence Spread Spectrum (DSSS) code. To minimize collisions among transmissions, the communication system is designed to use a high-gain antenna with a limited field of view, to limit the number of cotemporaneous, or overlapping transmissions that are received at the base station. To cover a wide area, the limited field of view is swept across the area of coverage. To overcome potential losses caused by collisions, the remote terminal units are configured to repeat transmissions; to minimize repeated collisions, the repeat interval and/or duration is randomized.
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Citations
6 Claims
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1. A communication system comprising:
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a satellite having a high-gain antenna configured with a field of view that sweeps a service area on a planet in a first direction during a sweep period, wherein the field of view covers less than the entirety of the service area in the first direction and the field of view covers the entirety of the service area in a second direction perpendicular to the first direction, and wherein the sweep period is the amount of time it takes the field of view of the antenna to be swept across the service area in the first direction; a plurality of remote terminal units, each including a respective transmitter configured to transmit a transmission message to the satellite during an illumination period in which the transmitter is within the field of view of the high-gain antenna, wherein the illumination period is a fraction of the sweep period and wherein the duration of the transmission message is less than the illumination period; and a ground station configured to receive one or more retransmission messages corresponding to one or more transmission messages transmitted by a respective one or more of the plurality of remote terminal units, wherein a respective one of a plurality of direct sequence spread spectrum codes is allocated to each of the plurality of remote terminal units, and the respective transmitter of each of the plurality of remote terminal units is configured to transmit in accordance with the corresponding allocated direct sequence spread spectrum code, and wherein the respective transmitter of a first one of the plurality of remote terminal units is configured to transmit in accordance with a particular direct sequence spread spectrum code and the respective transmitter of a second one of the plurality of remote terminal units is configured to also transmit in accordance with the same particular direct sequence spread spectrum code. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification