IPC분류정보
| 국가/구분 |
United States(US) Patent
등록
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| 국제특허분류(IPC7판) |
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| 출원번호 |
US-0139957
(1993-10-19)
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발명자
/ 주소 |
- Davis Mark E. (Carlsbad CA)
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| 출원인 / 주소 |
- Hughes Aircraft Company (Los Angeles CA 02)
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| 인용정보 |
피인용 횟수 :
90 인용 특허 :
0 |
초록
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A direct-sequence multiple-access code division (DS-CDMA) communication system accommodates a multiplicity of separate transmitters (12) and at least one base-station receiver (14). Each transmitter generates a transmitted signal (16) at a common carrier frequency. Each transmitter has an assigned s
A direct-sequence multiple-access code division (DS-CDMA) communication system accommodates a multiplicity of separate transmitters (12) and at least one base-station receiver (14). Each transmitter generates a transmitted signal (16) at a common carrier frequency. Each transmitter has an assigned spreading code. Each bit time within the transmitted signal includes a unique signature waveform (21) generated from the spreading code that identifies the source of the transmitted signal. For a given transmitter, the transmitted signals from the other transmitters represent “multi-access noise”that may adversely degrade the signal-to-noise ratio (SNR) of that transmitter\s signal at the receiver. Each transmitter operates using a spectrally inefficient power spectrum, i.e., a non-flat power spectrum, that simplifies the transmitter circuits. Each transmitter includes a clock source (26), a signature waveform generator (28), a data generator (30, 32), a first multiplier (42), a low pass filter (44), and RF generator (46), a second multiplier (48), a bandpass filter (50), a power amplifier (52) and a broadcast antenna (54). The receiver processes the received waveform signal on a bit-by-bit basis in the absence of knowledge of the other transmitters\spreading codes. An adaptive linear filter (66) included within the receiver (14) operates to make the SNR for the spectrally-inefficient transmitted signals approach asymptotically the SNR that would be received from a spectrally-efficient transmitted signal. Additionally, the receiver rejects narrowband interference, thereby providing superior performance over a spectrally-efficient system with no narrowband noise rejection.
대표청구항
▼
A direct-sequence multiple-access code division (DS-CDMA) communication system comprising: (1) a multiplicity of transmitters, each including: (a) a first signal generator that generates an analog baseband waveform signal having a plurality of bits, each bit having a time period of TB, said bits bei
A direct-sequence multiple-access code division (DS-CDMA) communication system comprising: (1) a multiplicity of transmitters, each including: (a) a first signal generator that generates an analog baseband waveform signal having a plurality of bits, each bit having a time period of TB, said bits being digitally encoded with data that is to be transmitted, (b) a second signal generator that generates a unique signature waveform signal having a spectrally inefficient power spectrum, said unique signature waveform signal being made up of a sequence of chip waveform signals, each chip waveform signal in said sequence of chip waveform signals having a duration of TC seconds, a polarity controlled by a unique spreading code, and a bandwidth substantially corresponding to an allowed channel bandwidth, said spectrally inefficient power spectrum being spectrally inefficient and substantially non-flat within a band ±1/TC, (c) a first modulator that modulates each bit of the analog baseband waveform signal with the unique signature waveform signal to yield a direct sequence spread waveform signal, (d) a first filter for filtering the direct sequence spread waveform signal, (e) an RF generator that generates an RF carrier signal, said RF carrier signal having a carrier frequency that is the same for all of said multiplicity of transmitters, (f) a second modulator that modulates said RF carrier signal with the filtered direct sequence spread waveform signal, and (f) a transmitter that transmits the modulated RF carrier signal; and (2) at least one base-station receiver comprising: (a) an RF receiver that receives the transmitted modulated RF carrier signals from each of the multiplicity of transmitters, (b) a second filter that filters the modulated RF carrier signal to improve the signal-to-noise ratio (SNR) and to compensate for the spectrally inefficient substantially non-flat power spectrum of the signature waveform signal within the band ±1/TC, and (c) a spread spectrum receiver that processes the filtered modulated RF carrier signal to despread such signal in order to identify a particular signature waveform signal contained therein, downconvert such signal to remove the RF carrier therefrom, and integrate such signal over a bit time to determine its informational content, said informational content over several bit times comprising the digital data transmitted by a particular one of said multiplicity of transmitters.
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