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Multiuser communications system

  • US 10,284,286 B2
  • Filed: 08/21/2014
  • Issued: 05/07/2019
  • Est. Priority Date: 08/21/2013
  • Status: Active Grant
First Claim
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1. A method for operation of a multiuser receiver in a slot based wireless communication system to detect multiple transmissions via iterative soft interference cancellation, the method comprising:

  • a) receiving a signal in a slot;

    b) attempting to acquire one or more user signals in a residual signal by searching for a predefined signal inserted in a complex transmit signal transmitted by a user to aid acquisition, and for each new user signal acquired, estimating a set of channel parameters for the acquired new user signal, and adding the acquired new user signal to a set of acquired user signals, wherein the set of channel parameters comprises at least one of a complex gain, a time offset, a frequency offset, a rate of change of frequency offset, or a noise variance;

    c) decoding the residual signal, for each acquired user signal in the set of acquired user signals comprising;

    generating a soft estimate of the complex transmit signal associated with the acquired user signal; and

    refining or initially estimating at least one of a time offset estimate, a frequency offset estimate, a rate of change of frequency offset estimate, a complex gain estimate, an interference plus noise power estimate, or a signal to interference plus noise ratio (SINR) estimate using the soft estimate of the complex transmit signal, a previous soft estimate of the signal contribution from the user, and the residual signal to obtain an updated set of channel parameters for the acquired user signal and an updated soft estimate of the signal contribution in the residual signal from the acquired user signal;

    d) updating the residual signal by subtracting the updated soft estimate of the signal contribution for each user signal obtained in step c) from the residual signal; and

    e) performing another iteration of steps b) to d) until a termination condition is met wherein the updated residual signal in previous step d) is the residual signal in the next iteration of steps b) to d), andwherein steps c) and d) may be performed serially, or step c) may be performed in parallel for each user signal in the set of acquired user signals, such that the residual signal for the next iteration of steps b) to d) comprises the residual signal from which the updated soft estimate of the signal contribution for each user signal has been subtracted, and during each iteration, step c) may be repeated for a user signal in the set of acquired users or step c) may be skipped for one or more user signals in the set of acquired user signals in which case the previous soft estimate of the signal contribution from the acquired user signal is used as the updated soft estimate of the signal contribution from the acquired user signal,wherein the residual signal in step b) is the received signal from step a) if step d) has not yet been performed.

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