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Multiuser interference canceler for DS-CDMA system

  • US 6,584,115 B1
  • Filed: 06/22/1999
  • Issued: 06/24/2003
  • Est. Priority Date: 06/25/1998
  • Status: Expired due to Fees
First Claim
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1. A DS-CDMA multiuser interference canceler for processing a received signal containing spread signals from a plurality of users to remove signals of other users from a signal of each user and thereafter decode the signal of each user, comprising:

  • a first stage comprising a plurality of series-connected blocks, each block including a respective first interference canceler unit, for generating and outputting a respective interference replica signal which is substantially identical to respective signal components of respective users, and a respective first subtracting means for subtracting the respective interference replica signal from the received signal;

    a plurality of second stages comprising a plurality of series-connected blocks, each block including a respective adding means for adding the respective interference replica signal generated in a preceding stage to signals from a preceding block, a respective second interference canceler unit for generating a second interference replica signal which is substantially identical to the respective signal components of the respective user from output signals from said respective adding means, and except for the last block in the last stage, a respective second subtracting means for subtracting the second interference replica signal from the output signals from said respective adding means and outputting a differential signal;

    a plurality of decoding means for decoding symbols generated in a final one of said second stages; and

    a plurality of preliminary demodulating means for measuring a reception quality of the signals of the users contained in the received signal;

    each of said interference canceler units, except a first interference canceler unit in the first block in the first stage, comprising means for controlling an interference canceler unit in the preceding block to turn off the outputting of the respective interference replica signal if the reception quality of output signals from the preceding block is more degraded than the reception quality of the signals of the users measured by said preliminary demodulating means.

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