Co-channel spatial separation using matched doppler filtering

Patent metadata

Field	Value
Publication number	US-2017041175-A1
Application number	US-201514820709-A
Country	US
Kind code	A1
Filing date	Aug 7, 2015
Priority date	Aug 7, 2015
Publication date	Feb 9, 2017
Grant date	—

Abstract

Systems ( 100 ) and methods for co-channel separation of communication signals. The methods involve: simultaneously receiving a plurality of communication signals transmitted at disparate relative Doppler frequencies from different locations within a multi-access system; performing matched filtering operations to pre-process each of the plurality of communication signals so as to generate pre-processed digitized samples using a priori information contained in pre-ambles ( 302, 304 ) of messages present within the plurality of communication signals; using estimated signal parameters to detect the plurality of communication signals from the pre-processed digitized samples; and demodulating the plurality of communication signals without using a Viterbi decoder.

First claim

1 . A method for co-channel separation of communication signals, comprising:
simultaneously receiving a plurality of communication signals transmitted at disparate relative Doppler frequencies from different locations within a multi-access system; performing matched filtering operations to pre-process each of the plurality of communication signals so as to generate pre-processed digitized samples using a priori information contained in pre-ambles of messages present within the plurality of communication signals; using estimated signal parameters to detect the plurality of communication signals from the pre-processed digitized samples; and demodulating the plurality of communication signals using a Reduced State Sequence Estimation (“RSSE”) demodulation technique.

2 . The method according to claim 1 , wherein the plurality of pre-processed digitized samples are generated by estimating at least one of the following signal parameters: a signal's Time Of Arrival (“TOA”); a Doppler frequency; a phase; and a Signal-to-Noise Ratio (“SNR”).

3 . The method according to claim 1 , wherein the estimated signal parameters are determined using the a priori information contained in the pre-ambles of the messages.

4 . The method according to claim 1 , wherein the matched filtering operations are performed in a frequency domain.

5 . The method according to claim 1 , wherein the a prior information comprises a training sequence and a start flag of an Automatic Identification System (“AIS”) message.

6 . The method according to claim 1 , wherein a Constant False Alarm Rate (“CFAR”) technique is used to detect the plurality of communication signals from the pre-processed digitized samples.

7 . A method for co-channel separation of communication signals, comprising:
simultaneously receiving a plurality of communication signals transmitted at disparate relative Doppler frequencies from different locations within a multi-access system; performing matched filtering operations to pre-process each of the plurality of communication signals so as to generate pre-processed digitized samples using a priori information contained in pre-ambles of messages present within the plurality of communication signals; using estimated signal parameters to detect the plurality of communication signals from the pre-processed digitized samples; and demodulating the plurality of communication signals using a demodulation technique exclusive of a classical full-state Viterbi algorithm; wherein the plurality of communication signals are demodulating using a Reduced State Sequence Estimation (“RSSE”) or a Decision Feedback Equalization (“DFE”) demodulation technique.

8 . The method according to claim 7 , wherein the DFE demodulation technique involves:
match filtering each signal of the plurality of communication signals; de-rotating each signal to a real axis; whitening filtering each signal to remove the effects of Inter-Symbol Interference (“ISI”) on pulses that are currently being demodulated; non-coherently demodulating each signal; and determining hard decisions and soft decisions about binary bits contained in each signal.

9 . The method according to claim 8 , wherein the soft decisions are used for error correction based on a Cyclic-Redundancy Code (“CRC”).

10 . A method for co-channel separation of communication signals, comprising:
simultaneously receiving a plurality of communication signals transmitted at disparate relative Doppler frequencies from different locations within a multi-access system; performing matched filtering operations to pre-process each of the plurality of communication signals so as to generate pre-processed digitized samples using a priori information contained in pre-ambles of messages present within the plurality of communication signals; using estimated signal parameters to detect the plurality of communication signals from the pre-processed digitized samples; and demodulating the plurality of communication signals using a demodulation technique exclusive of a classical full-state Viterbi algorithm; wherein the demodulating is performed by a number of demodulators that is less than that required to span an entire channel instantaneous bandwidth.

11 . A system, comprising:
a signal processing circuit configured to
simultaneously receive a plurality of communication signals transmitted at disparate relative Doppler frequencies from different locations within a multi-access system,
perform matched filtering operations to pre-process each of the plurality of communication signals so as to generate pre-processed digitized samples using a priori information contained in pre-ambles of messages present within the plurality of communication signals,
use estimated signal parameters to detect the plurality of communication signals from the pre-processed digitized samples, and
demodulate the plurality of communication signals using a Reduced State Sequence Estimation (“RSSE”) demodulation technique. algorithm.

12 . The system according to claim 11 , wherein the plurality of pre-processed digitized samples are generated by estimating at least one of the following signal parameters: a signal's Time Of Arrival (“TOA”); a Doppler frequency; a phase; and a Signal-to-Noise Ratio (“SNR”).

13 . The system according to claim 11 , wherein the estimated signal parameters are determined using the a priori information contained in the pre-ambles of the messages.

14 . The system according to claim 11 , wherein the matched filtering operations are performed in a frequency domain.

15 . The system according to claim 11 , wherein the a prior information comprises a training sequence and a start flag of an Automatic Identification System (“AIS”) message.

16 . The system according to claim 11 , wherein a Constant False Alarm Rate (“CFAR”) technique is used to detect the plurality of communication signals from the pre-processed digitized samples.

17 . A system, comprising:
a signal processing circuit configured to
simultaneously receive a plurality of communication signals transmitted at disparate relative Doppler frequencies from different locations within a multi-access system,
perform matched filtering operations to pre-process each of the plurality of communication signals so as to generate pre-processed digitized samples using a priori information contained in pre-ambles of messages present within the plurality of communication signals,
use estimated signal parameters to detect the plurality of communication signals from the pre-processed digitized samples, and
demodulate the plurality of communication signals using a demodulation technique exclusive of a classical full-state Viterbi algorithm; wherein the plurality of communication signals are demodulating using a Reduced State Sequence Estimation (“RSSE”) or a Decision Feedback Equalization (“DFE”) demodulation technique.

18 . The system according to claim 17 , wherein the DFE demodulation technique involves:
match filtering each signal of the plurality of communication signals; de-rotating each signal to a real axis; whitening filtering each signal to remove the effects of Inter-Symbol Interference (“ISI”) on pulses that are currently being demodulated; non-coherently demodulating each signal; and determining hard decisions and soft decisions about binary bits contained in each signal.

19 . The system according to claim 18 , wherein the soft decisions are used for error correction.

20 . A system, comprising:
a signal processing circu

Assignees

• Harris Corp

Inventors

• Dyson Timothy F
• Mcpherson Rodney K

Classifications

• H04L1/0045

  Arrangements at the receiver end · CPC title

• H04L5/0058

  Allocation criteria · CPC title

• H04L27/2649 Primary

  Demodulators · CPC title

• H04L25/03057

  with a recursive structure (H04L25/03031 takes precedence) · CPC title

• H04L1/0061

  Error detection codes · CPC title