Method and apparatus to permit substantial cancellation of interference between a received first and second signal
First Claim
1. A method of separating and substantially reducing interference at a receiver between a first and a second digital information signal which use the same frequency spectrum and are received by the receiver from approximately the same direction, the method comprising the steps of:
- at a remote transmitter(a) transmitting the first digital information signal in uncoded form in a predetermined frequency band in a first direction;
while concurrently(b) transmitting the second digital information signal having a different informational content in coded form and at a lower information transmission capacity than said first information signal in said predetermined frequency band in said first direction, said code used comprising a forward error correcting code; and
at the receiver receiving said uncoded first digital information signal and said coded second digital information signal(c) performing a detection process on the uncoded first digital information signal and the coded second digital information signal for generating the most likely digits representative of the received first digital information signals and decoded second digital information signal.
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Abstract
The present invention relates to method and apparatus for substantially reducing the effects of interference at a receiver between concurrently received first and second digital signals which use the same frequency spectrum. Interference between signals is effectively reduced by transmitting the first digital signal in an uncoded form while concurrently transmitting the second digital signal with both reduced capacity when compared with the first signal and in coded form using a forward error correcting code such as, for example, a block or convolutional code. At the receiver intercepting both digital signals, a suitable detection process is performed to decode the second signal and separate both signals. The present invention is applicable to the simultaneous satellite transmission of an area coverage beam and a plurality of spot coverage beams or to increase capacity on a radio channel.
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Citations
13 Claims
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1. A method of separating and substantially reducing interference at a receiver between a first and a second digital information signal which use the same frequency spectrum and are received by the receiver from approximately the same direction, the method comprising the steps of:
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at a remote transmitter (a) transmitting the first digital information signal in uncoded form in a predetermined frequency band in a first direction;
while concurrently(b) transmitting the second digital information signal having a different informational content in coded form and at a lower information transmission capacity than said first information signal in said predetermined frequency band in said first direction, said code used comprising a forward error correcting code; and at the receiver receiving said uncoded first digital information signal and said coded second digital information signal (c) performing a detection process on the uncoded first digital information signal and the coded second digital information signal for generating the most likely digits representative of the received first digital information signals and decoded second digital information signal. - View Dependent Claims (2, 3, 4)
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5. A communication system capable of substantially cancelling the effects of interference at a receiver between a first and a second received digital information signal which use the same predetermined frequency spectrum, comprising
a transmitter comprising a first transmission section including means for modulating a first input digital information signal to the predetermined frequency spectrum; -
a second transmission section including means capable of both encoding a second input digital information signal, having a different informational content and a lower information transmission capacity than said first digital information signal, using a forward error correcting code and modulating the second encoded digital information signal to said predetermined frequency spectrum; and means for concurrently transmitting each of the modulated first digital information signal and the encoded and modulated second digital information signal in a predetermined direction; and a receiver disposed in the path of said transmitted first and second digital information signals comprising a detector which includes decoding means capable of generating from the combined received signal of the interfering uncoded first digital information signal and coded second digital information signal the most likely digits representative of the desired first digital information signal and decoded second digital information signal. - View Dependent Claims (6, 7, 8)
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9. A transmitter comprising
a first transmission section including means for modulating a first input digital information signal to a predetermined frequency spectrum; -
a second transmission section including means capable of both encoding a second input digital information signal having a different informational content and a lower information transmission capacity than said first digital information signal using a forward error correcting code and modulating the second digital information signal to said predetermined frequency spectrum; and means for concurrently transmitting each of the digitally modulated first information signal and the encoded and digitally modulated second information signal in a predetermined direction. - View Dependent Claims (10, 11)
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12. In a communication system comprising a transmitter which concurrently transmits a first digital information signal in uncoded form in a predetermined frequency spectrum and a second digital information signal having a different informational content and lower information transmission capacity than the first digital information signal in coded form using a forward error correcting code in the predetermined frequency spectrum towards a predetermined receiving area, a receiver comprising
means for receiving the interfering uncoded first digital information signal and coded digital second information signal; - and
a detector which includes decoding means capable of generating from the combined received signal of said interfering uncoded first information signal and coded second information signal the most likely digits representative of the desired uncoded first digital information signal and decoded second digital information signal. - View Dependent Claims (13)
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Specification