System and method for providing an accurate estimation of received signal interference for use in wireless communications systems

• US 20040091025A1
• Filed: 10/08/2003
• Published: 05/13/2004
• Est. Priority Date: 05/11/1999
• Status: Active Grant

• Current Assignee: Eduardo A.S. Esteves, Nagabhushana T. Sindhushayana
• Original Assignee: Eduardo A.S. Esteves, Nagabhushana T. Sindhushayana
• Inventors: Sindhushayana, Nagabhushana T., Esteves, Eduardo A.S.
• Granted Patent: US 6,975,671 B2
• Time in Patent Office: Days
• US Class Current: 375/148
• CPC Class Codes: H04B 1/712 Weighting of fingers for combining, e.g. amplitude control or phase rotation using an inner loop
• CPC Class Codes: H04B 17/336 Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR]
• CPC Class Codes: H04L 25/067 providing soft decisions, i.e. decisions together with an estimate of reliability H04L25/068 and H04L25/069 take precedence; sequence estimation techniques H04L25/03178
• CPC Class Codes: H04L 27/34 Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
• CPC Class Codes: H04L 27/38 Demodulator circuits; Receiver circuits

Abstract

A system for providing an accurate interference value signal received over a channel and transmitted by an external transceiver. The system includes a first receiver section for receiving the signal, which has a desired signal component and an interference component. A signal extracting circuit extracts an estimate of the desired signal component from the received signal. A noise estimation circuit provides the accurate interference value based on the estimate of the desired signal component and the received signal. A look-up table transforms the accurate noise and/or interference value to a normalization factor. A carrier signal-to interference ratio circuit employs the normalization factor and the received signal to compute an accurate carrier signal-to-interference ratio estimate. Path-combining circuitry generates optimal path-combining weights based on the received signal and the normalization factor.

Claims

1. A code division multiple access (CDMA) communication apparatus, comprising:

means for receiving a signal over a wireless channel, the received signal comprising a desired signal component and an interference component;

means for estimating carrier signal-to-interference and interference energy of the received signal to generate an interference energy value and a signal-to-interference ratio of the received signal, the means for estimating carrier signal-to-interference and interference energy comprising means for extracting an estimate of the desired signal component from the received signal; and

means for generating summed weighted-path signals in response to the interference energy value and the estimate of the desired signal component.

2. The apparatus of claim 1, further comprising means for generating soft decision values based on the summed weighted-path signals.

3. The apparatus of claim 2, wherein the means for generating soft decision values comprises a log-likelihood ratio generator.

4. The apparatus of claim 2, further comprising means for generating decoded signals based on the soft decision values.

5. The apparatus of claim 4, further comprising means for generating a message selected from the group consisting of a rate control message and a power fraction request message based on the signal-to-interference ratio.

6. The apparatus of claim 1, wherein the means for receiving a signal comprises an intermediate-frequency (IF)-to-baseband converter to generate spread-spectrum in-phase and quadrature signals based on the received signal.

7. The apparatus of claim 6, wherein the means for extracting an estimate of the desired signal component comprises a pseudo-noise despreader to generate despread in-phase and quadrature signals based on the spread-spectrum in-phase and quadrature signals.

8. The apparatus of claim 7, wherein the means for extracting an estimate of the desired signal component further comprises a decoverer connected to the pseudo-noise despreader to separate data signals along a data channel and a pilot signal along a pilot channel from the despread in-phase and quadrature signals.

9. The apparatus of claim 8, wherein the data channel is described by the following equation:

10. The apparatus of claim 8, wherein the means for estimating carrier signal-to-interference and interference energy further comprises a pilot filter connected to the decoverer to generate a filtered pilot signal.

11. The apparatus of claim 10, wherein the filtered pilot signal is described by the following equation:

p=M{square root}{square root over (Ê

)}_p,l·

e<sup>jθ

l</sup>

where p represents the filtered output signal, M is the number of chips per Walsh symbol, Ê

_p,l is pilot chip energy of an Ith multipath component of p, and θ

l is the phase of p.

12. The apparatus of claim 11, wherein the means for estimating carrier signal-to-interference and interference energy further comprises a forward link constant generator capable of generating a forward link constant.

13. The apparatus of claim 12, wherein the forward link constant is described by the following equation:

14. The apparatus of claim 13, wherein the means for estimating carrier signal-to-interference and interference energy further comprises a look-up table capable of generating a reciprocal of the interference energy value based on the despread in-phase and quadrature signals, the filtered pilot signal and the forward link constant.

15. The apparatus of claim 14, wherein the means for generating summed weighted-path signals comprises:

a constant generator capable of generating a constant

$k=\frac{1}{M}<br><br>\sqrt{\frac{E_s}{E_p}},$

 

where E_s is modulation symbol energy; and

a multiplier connected to the constant generator and the pilot filter to generate an estimate of a channel coefficient

{circumflex over (α

)}={square root}{square root over (Ê

)}_s,l·

e<sup>j{circumflex over (θ

)}l</sup>,

where Ê

_s,l is an estimate of the modulation symbol energy of the l^th multipath component, and {circumflex over (θ

)}^l is an estimate of the phase of the pilot signal.

16. The apparatus of claim 15, wherein the summed path-weighted signals are generated based on the estimate of the channel coefficient, the reciprocal of the interference energy value, and the number of chips per Walsh symbol.