Joint symbol, amplitude, and rate estimator
View Patent ↗The system in one embodiment relates to tightly integrating parameter estimation, symbol hypothesis testing, decoding, and rate identification. The present invention provides Turbo-decoding for joint signal demodulation based on an iterative decoding solution that exploits error correction codes. The system iteratively couples an initial amplitude estimator, a symbol estimator, a bank of decoders, and a joint amplitude estimator to produce the symbol estimates.
1. A joint amplitude estimator for a data stream from multiple users, comprising:
a data stream from said multiple users divided into a plurality of observation intervals;
a plurality of processing modules coupled to said observation intervals, wherein said processing modules calculates interference cancellation values for each of said users and computes a filter for each of said observation intervals, said filter being applied to said data within said observation interval to compute individual amplitude estimates; and
an amplitude estimation unit which processes said individual amplitude estimates and calculates new amplitude estimates, wherein said new amplitude estimates are iteratively passed back to said processing modules either a maximum number of iterations or a desired bit error rate have been reached.
2. The joint amplitude estimator according to claim 1 , wherein said final condition is selected from at least one of the group consisting of: bit error rate metric level and fixed number of iterations.
3. The joint amplitude estimator according to claim 1 , wherein said amplitude estimation unit sums and weighs said individual estimates.
4. The joint amplitude estimator according to claim 1 , wherein said observation intervals are based on distinguishing attributes selected from at least one of the group consisting of: time, code, and frequency.
5. The joint amplitude estimator according to claim 1 , wherein said filter is calculated for an arbitrary observation interval m as:
G m =B m S m H ( S m χ m S m H +σ n 2 I ) −1
wherein G m is a MMSE filter, B m is a diagonal matrix representing the expected bit or symbol value, S m is an S matrix defined over a single observation interval, I is an identity matrix and m is an arbitrary observation interval.
6. A method for processing amplitude estimates for a multiuser data stream divided into a plurality of observation intervals, comprising:
computing a filter for each said observation interval of said data stream;
applying interference cancellation to said data stream for each said observation interval;
applying said filter to said data stream for each said observation interval from said interference cancellation to produce individual amplitude estimates for each said observation interval;
computing new amplitude estimates using said individual amplitude estimates; and
passing said new amplitude estimates back to said filter for iterative processing until either a maximum number of iterations or a desired bit error rate have been reached.
7. The method according to claim 6 , wherein said computing further comprises summing said individual amplitude estimates and weighing.
8. The method according to claim 6 , wherein said final condition is selected from at least from the group consisting of: bit error rate metric level and fixed number of iterations.