Method and apparatus providing an advanced mimo receiver that includes a signal-plus-residual interference (SPRI) detector

• US 20080212722A1
• Filed: 04/07/2008
• Published: 09/04/2008
• Est. Priority Date: 09/10/2003
• Status: Active Grant

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Nokia Corporation
• Inventors: Heikkila, Markku J.
• Granted Patent: US 7,583,723 B2
• Time in Patent Office: Days
• US Class Current: 375/341
• CPC Class Codes: H04B 1/71057 using maximum-likelihood sequence estimation [MLSE]
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0891 Space-time diversity rake receivers H04B1/7115; space-time decoding H04L1/0631
• CPC Class Codes: H04L 2025/03375 Passband transmission
• CPC Class Codes: H04L 25/03006 Arrangements for removing intersymbol interference

Abstract

A method is disclosed to obtain M final symbol decisions for signals received through N receive antennas that were transmitted in M parallel data layers, using a same spreading code from M transmit antennas. The method includes space-time equalizing the N received signals to generate M output signals from which at least inter-symbol interference is substantially removed and inter-layer interference is suppressed; despreading each of the M output signals for generating M soft symbol estimates; and processing the M soft symbol estimates to derive M final symbol decisions that are made in consideration of modeled residual inter-layer interference present in the space-time equalized M output signals. Processing includes operating a signal-plus-residual-interference (SPRI) detector that operates in accordance with a maximum likelihood (ML) technique, while space-time equalizing employs a linear minimum mean-square error (LMMSE) criterion. Transmitting may occur at a base station having the M transmit antennas, and receiving may occur at a mobile station having the N receive antennas.

Claims

1. A method comprising:

space-time equalizing N received signals to generate M output signals from which at least inter-symbol interference and inter-layer interference are suppressed;

despreading each of the M output signals for generating M soft symbol estimates; and

processing the M soft symbol estimates to derive M final symbol decisions that are made in consideration of modeled residual inter-layer interference present in the space-time equalized M output signals, where processing further comprises operating a signal-plus-residual interference (SPRI) detector that operates in accordance with a maximum likelihood (ML) technique.

3. A method as in claim 1, where space-time equalizing employs a linear minimum mean-square error (LMMSE) criterion.

4. A method as in claim 1, where transmitting occurs at a base station having the M transmit antennas, where receiving occurs at a mobile station having the N receive antennas, and where N<

M.

2. (canceled)

5. A system to obtain M final symbol decisions for signals received through N receive antennas that were transmitted in M parallel data layers, using a same spreading code from M transmit antennas, comprising:

a space-time equalizer configured to operate on the N received signals to generate M output signals from which at least inter-symbol interference and interlayer interference are suppressed;

a plurality of despreaders configured to despread each of the M output signals to generate M soft symbol estimates; and

processing apparatus configured to process the M soft symbol estimates to derive M final symbol decisions that are made in consideration of modeled residual inter-layer interference present in the M output signals of said space-time equalizer, where said processing apparatus further comprises a signal-plus-residual-interference (SPRI) detector that operates in accordance with a maximum likelihood (ML) technique.

7. A system as in claim 5, where said space-time equalizer employs a linear minimum mean-square error (LMMSE) criterion.

8. A system as in claim 5, where the M transmit antennas are associated with a base station, where the N receive antennas are associated with a mobile station, and where N<

M.

6. (canceled)

9. A Multiple Input, Multiple Output (MIMO) RF receiver, configured to receive M symbols transmitted in M parallel data layers through N receive antennas, using a same spreading code, c(k), from M transmit antennas;

a space-time equalizer having N inputs coupled to said N receive antennas and M outputs coupled to individual ones of M code correlators, the space-time equalizer configured to suppress at least inter-symbol interference and inter-layer interference;

a signal model generator having an input coupled to a channel estimator and an output for outputting at least a model of residual inter-layer interference; and

a signal-plus-residual-interference (SPRI) detector having M inputs coupled to outputs of said M code correlators configured to receive M soft symbol estimates there from, a further input coupled to said output of said signal model generator, and M outputs configured to output M final symbol decisions that are made taking into account the residual inter-layer interference that was not removed by said space-time equalizer.

10. A MIMO RF receiver as in claim 9, where said signal model generator computes:

$A_{\mathrm{jm}}=w_m^H<br><br>\left(\begin{array}{c}{h}_{j<br><br><br><br>1}\\ h_{j<br><br><br><br>2}\\ \mathrm{⋮<br><br>}\\ h_{\mathrm{jM}}\end{array}\right),j=1,2,\mathrm{\dots <br><br>}<br><br>,M,$

where A_jm is the residual amplitude of the symbol from transmit antenna j when a symbol from transmit antenna m is detected by said space-time equalizer.

11. A MIMO RF receiver as in claim 10, where said SPRI detector uses a maximum-likelihood (ML) criterion to obtain the final symbol decisions as:

$\left(\begin{array}{c}{\stackrel{\_}{s}}_1\\ {\stackrel{\_}{s}}_2\\ \mathrm{⋮<br><br>}\\ {\stackrel{\_}{s}}_M\end{array}\right)=\arg <br><br><br><br>\underset{u_1,u_2,\mathrm{\dots <br><br>}<br><br><br><br>u_M}{\min }<br><br>\left\{\underset{m=1}{\overset{M}{\sum <br><br>}}<br><br>{<br><br>{\hat{s}}_m-\left(\begin{array}{cccc}{A}_{1<br><br>m}& A_{2<br><br>m}& \mathrm{\dots <br><br>}& A_{\mathrm{Mm}}\end{array}\right)<br><br>\left(\begin{array}{c}{u}_1\\ u_2\\ \mathrm{⋮<br><br>}\\ u_M\end{array}\right)<br><br>}^2\right\},$

where detection of an mth data layer is based on the outputs of all of said M code correlators.

12. A MIMO RF receiver as in claim 9, where said signal model generator generates signal models for both desired signals and for interfering signals appearing at said M outputs of said space-time equalizer.

13. A MIMO RF receiver as in claim 9, where said space-time equalizer operates with a linear minimum mean-square error (LMMSE) criterion.

14. A MIMO RF receiver as in claim 9, where N<

M.

15. A received signal-plus-residual-interference (SPRI) detector comprising M inputs configured to be coupled to M sources of soft symbol estimates in which inter-symbol interference and inter-layer interference have been suppressed, a further input configured to be coupled to an output of a signal model generator that models residual inter-layer interference present in an equalized received signal, and M outputs configured to output M final symbol decisions that are made taking into account the residual inter-layer interference.

16. The SPRI detector as in claim 15, where the signal model generator computes:

$A_{\mathrm{jm}}=w_m^H<br><br>\left(\begin{array}{c}{h}_{j<br><br><br><br>1}\\ h_{j<br><br><br><br>2}\\ \mathrm{⋮<br><br>}\\ h_{\mathrm{jM}}\end{array}\right),j=1,2,\mathrm{\dots <br><br>}<br><br>,M,$

where A_jm is the residual amplitude of a symbol from transmit antenna j when a symbol from transmit antenna m is detected by a space-time equalizer that generates the equalized received signal, and where said SPRI detector uses a maximum-likelihood (ML) criterion to obtain the final symbol decisions as;

$\left(\begin{array}{c}{\stackrel{\_}{s}}_1\\ {\stackrel{\_}{s}}_2\\ \mathrm{⋮<br><br>}\\ {\stackrel{\_}{s}}_M\end{array}\right)=\arg <br><br><br><br>\underset{u_1,u_2,\mathrm{\dots <br><br>}<br><br><br><br>u_M}{\min }<br><br>\left\{\underset{m=1}{\overset{M}{\sum <br><br>}}<br><br>{<br><br>{\hat{s}}_m-\left(\begin{array}{cccc}{A}_{1<br><br>m}& A_{2<br><br>m}& \mathrm{\dots <br><br>}& A_{\mathrm{Mm}}\end{array}\right)<br><br>\left(\begin{array}{c}{u}_1\\ u_2\\ \mathrm{⋮<br><br>}\\ u_M\end{array}\right)<br><br>}^2\right\},$

where detection of an mth data layer is based on all said M sources of soft symbol estimates.

17. The SPRI detector as in claim 15, where the received signal is received through N receive antennas from M transmit antennas, where N≦

M.

18. A system to obtain M final symbol decisions for signals received through N receive antennas that were transmitted in M parallel data layers, using a same spreading code from M transmit antennas, comprising:

an equalizer configured to operate on the N received signals to generate M output signals from which at least inter-symbol interference and inter-layer interference is are suppressed;

a plurality of despreaders arranged to despread each of the M output signals for generating M soft symbol estimates; and

processing apparatus configured to process the M soft symbol estimates to derive M final symbol decisions that are made in consideration of modeled residual inter-layer interference present in the M output signals of said equalizer.

19. A system as in claim 18, where said processing apparatus comprises a signal-plus-residual-interference (SPRI) detector.

20. A system as in claim 19, where said SPRI detector operates in accordance with a maximum likelihood (ML) technique.

21. A system as in claim 19, where said SPRI detector operates in accordance with a Maximum a posteriori (MAP) technique.

22. A system as in claim 19, where said system forms a part of an ordered successive interference canceller (OSIC) receiver.