Method and apparatus for identifying an orthogonal frequency division multiplexing (OFDM) terrestrial repeater using inactive sub-carriers
First Claim
1. A method of transmitting an identifying signal in an orthogonal frequency division multiplexing system, comprising the steps of:
- modulating said signal;
transforming said modulated signal to create an OFDM signal having a plurality of sub-carriers wherein a first subset of said plurality of sub-carriers are allocated pursuant to a standard for transmission of information and a second subset of said plurality of sub-carriers are allocated pursuant to said standard as inactive subcarriers that do not carry information; and
transmitting said identifying signal on one or more of said inactive sub-carriers for at least a portion of time, wherein said identifying signal identifies a transmitter.
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Accused Products
Abstract
A terrestrial repeater is disclosed for use in a satellite transmission system that may also include a plurality of satellites. The terrestrial repeaters are implemented as OFDM transmitters to minimize the channel impairments caused by multi-path propagation. The OFDM terrestrial repeaters differentially encode the transmitted signal over frequency, as opposed to time, in order to avoid channel phase distortion. The OFDM receiver allocates two unmodulated sub-carriers as pilot bins and thereby provides two sub-carriers as a reference within each OFDM symbol. At the OFDM receiver, the two unmodulated pilot bins contain no phase information and provide a reference for the differential demodulation performed by the OFDM receiver. The OFDM transmitter operates in two modes, namely, a normal mode and a transmitter identifier information (TII) mode. The TII mode contains all of the functions of the normal mode, and also transmits a repeater identification signal with the customer data, using the inactive OFDM sub-carriers (bins). In a normal mode, the OFDM transmitter optionally fills unused (inactive) sub-carriers with zeroes and in a TII mode, the OFDM transmitter uses at least some of the unused (inactive) sub-carriers to transmit the transmitter identifier information (TII). The predefined TII value is mapped onto a set of complex symbols. The TII signal facilitates the receiver test equipment in associating the received signal with the terrestrial repeater(s) that generate the TII signal.
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Citations
30 Claims
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1. A method of transmitting an identifying signal in an orthogonal frequency division multiplexing system, comprising the steps of:
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modulating said signal; transforming said modulated signal to create an OFDM signal having a plurality of sub-carriers wherein a first subset of said plurality of sub-carriers are allocated pursuant to a standard for transmission of information and a second subset of said plurality of sub-carriers are allocated pursuant to said standard as inactive subcarriers that do not carry information; and transmitting said identifying signal on one or more of said inactive sub-carriers for at least a portion of time, wherein said identifying signal identifies a transmitter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An orthogonal frequency division multiplexing transmitter for transmitting an OFDM signal, comprising:
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an encoder for modulating said OFDM signal; a transformer for creating said OFDM signal having a plurality of sub-carriers wherein a first subset of said plurality of sub-carriers are allocated pursuant to a standard for transmission of information and a second subset of said plurality of sub-carriers are allocated pursuant to said standard as inactive subcarriers that do not carry information; and means for inserting an identifying signal on one or more of said inactive sub-carriers for at least a portion of time, wherein said identifying signal identifies a transmitter. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A method of receiving an identifying signal in an orthogonal frequency division multiplexing system, comprising the steps of:
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transforming said received signal to recover an OFDM signal in the frequency domain having a plurality of sub-carriers wherein a first subset of said plurality of sub-carriers are allocated pursuant to a standard for transmission of information and a second subset of said plurality of sub-carriers are allocated pursuant to said standard as inactive subcarriers that do not carry information; decoding said OFDM signal; and processing said identifying signal received on one or more of said inactive sub-carriers for at least a portion of time, wherein said identifying signal identifies a transmitter. - View Dependent Claims (18, 19, 20, 21, 22, 23)
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24. An orthogonal frequency division multiplexing receiver for receiving an OFDM signal, comprising:
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a transformer for transforming said received signal to recover an OFDM signal in the frequency domain having a plurality of sub-carriers wherein a first subset of said plurality of sub-carriers are allocated pursuant to a standard for transmission of information and a second subset of said plurality of sub-carriers are allocated pursuant to said standard as inactive subcarriers that do not carry information; a decoder for demodulating said OFDM signal; and means for processing an identifying signal received on one or more of said inactive sub-carriers for at least a portion of time, wherein said identifying signal identifies a transmitter. - View Dependent Claims (25, 26, 27, 28, 29, 30)
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Specification