Signal despreader for CDMA systems
First Claim
1. In a CDMA system which transmits a coded signal for each of a plurality of users through a bandlimited channel, each coded user signal being formed by processing that user'"'"'s symbols using a sequence of code coefficients, said sequence being different for each user, and wherein a received signal includes a composite of all coded user signals, apparatus comprising:
- means for receiving samples of said received signal;
means for forming a filtered replica of each sequence of code coefficients; and
means for estimating a user'"'"'s symbols in response to said received signal samples and in response to said filtered replica of the sequence of code coefficients used to from this user'"'"'s coded signal.
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Accused Products
Abstract
A signal despreader for use in a CDMA system processes samples of the received signal with filtered replicas of the code coefficient sequences associated with the system users. The symbols transmitted by each system user are recovered using a filtered replica of that user'"'"'s associated code coefficient sequence. In the disclosed embodiment, the communications channel between each system user'"'"'s transmitter and the base station is bandlimited. Accordingly, within each user'"'"'s transmitter, filtering apparatus having a frequency characteristic is utilized to limit the frequency spectrum of each coded signal to a predetermined bandwidth equal to or less than that of the communications channel. Each filtered replica, pursuant to the present invention, reflects this frequency characteristic. In addition, the communications channel also has a frequency characteristic, and each filtered replica can reflect this characteristic as well.
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Citations
9 Claims
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1. In a CDMA system which transmits a coded signal for each of a plurality of users through a bandlimited channel, each coded user signal being formed by processing that user'"'"'s symbols using a sequence of code coefficients, said sequence being different for each user, and wherein a received signal includes a composite of all coded user signals, apparatus comprising:
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means for receiving samples of said received signal; means for forming a filtered replica of each sequence of code coefficients; and means for estimating a user'"'"'s symbols in response to said received signal samples and in response to said filtered replica of the sequence of code coefficients used to from this user'"'"'s coded signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. In a CDMA system which transmits a coded signal for each of a plurality of users through a bandlimited channel, each coded user signal being formed by processing that user'"'"'s symbols using a sequence of code coefficients which is different for each user and wherein a received signal includes a composite of all coded user signals, a method comprising the steps of:
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receiving samples of said received signal; forming a filtered replica of each sequence of code coefficients; and estimating a user'"'"'s symbols in response to said received signal samples and in response to said filtered replica of the sequence of code coefficients used to form this user'"'"'s coded signal.
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Specification