Channel estimation for a high-speed data packet access rake receiver
View Patent ↗An HSDPA rake receiver has a plurality of rake fingers. Different channels may experience different spreading factors. The channel estimate (CE) and the CE delay may be affected and depend on the spreading factor. The CE delay is related to the individual rake finger output buffer size. According to the structure of the present invention, an adaptive channel estimate delay that depends on the spreading factor may result in improved performance.
1. A high-speed data packet access (HSDPA) rake receiver comprising:
an input staging register operable to receive signal samples;
a Pseudo-Noise (PN) sequence generator operable to generate a PN sequence;
a despreader that employs the PN sequence to despread received signal samples, the dispreader using a spreading factor corresponding to a channel upon which the despreader operates;
a post-despread delay line that receives despread signal samples and produces delayed despread samples;
a channel estimator that produces a channel estimate based upon the despread samples, wherein the channel estimator produces the channel estimate with a channel estimate delay that is based upon the spreading factor; and
an energies and metrics module operable to receive the despread output of the despreader.
2. The HSDPA rake receiver of claim 1 , wherein the energies and metrics module receives the output of the channel estimator.
3. The HSDPA rake receiver of claim 1 , wherein an Space Time Transmit Diversity (STTD) decoder receives the outputs of the channel estimator and the post-despread delay line and operates upon the delayed despread samples using the channel estimate produced by the channel estimator.
4. The HSDPA rake receiver of claim 3 , wherein a delay matching combiner memory receives the output of the STTD decoder and performs combining operations on decoded samples.
5. The HSDPA rake receiver of claim 3 , wherein the Space Time Transmit Diversity (STTD) Decoder comprises:
a physical channel despreader;
a delay buffer;
an upper processing branch operable to apply a first channel estimate to the delay buffer symbol output, and apply a conjugate of a first channel estimate to the delay buffer symbol output and produce non STTD encoded symbols; and
a lower processing branch operable to read delayed delay buffer symbol outputs, apply a conjugate of a second channel estimate and a STTD decoder scheme to the delay buffer symbol output to produce non STTD encoded symbols.
6. The HSDPA rake receiver of claim 5 , wherein a first portion of the received signal is operated on by a first channel estimate function.
7. The HSDPA rake receiver of claim 5 , further comprising:
a combiner operable to combine the non STTD encoded symbols of the upper processing branch and non STTD encoded symbols lower processing branch.
8. The HSDPA rake receiver of claim 5 , wherein the upper branch operate on bits that have neither been flipped nor rearranged.
9. The HSDPA rake receiver of claim 8 , wherein the bits are flipped or rearranged according to a dedicated pattern.
10. The HSDPA rake receiver of claim 5 , wherein the STTD decoder is within a rake receiver of a wireless communication system.
11. The HSDPA rake receiver of claim 10 , wherein the wireless communication systems at comprise CDMA systems, spread spectrum systems, and Orthogonal Frequency Division Multiplex (OFDM) systems.
12. A high-speed data packet access (HSDPA) rake receiver comprising:
an input staging register operable to receive signal samples;
a Pseudo-Noise (PN) sequence generator operable to generate a PN sequence;
a despreader that employs the PN sequence to despread received signal samples, the dispreader using a spreading factor corresponding to a channel upon which the despreader operates;
a post-despread delay line that receives despread signal samples and produces delayed despread samples;
a channel estimator that produces a channel estimate based upon the despread samples, wherein the channel estimator produces the channel estimate with a channel estimate delay that is based upon the spreading factor; and
an energies and metrics module operable to receive the despread output of the despreader, wherein the energies and metrics module receives the output of the channel estimator; and wherein an Space Time Transmit Diversity (STTD) decoder receives the outputs of the channel estimator and the post-despread delay line and operates upon the delayed despread samples using a channel estimate produced by the channel estimator.
13. The HSDPA rake receiver of claim 12 , wherein a delay matching combiner memory receives the output of the STTD decoder and performs combining operations on decoded samples.
14. The HSDPA rake receiver of claim 13 , wherein the STTD decoder comprising:
a physical channel despreader;
a delay buffer;
an upper processing branch operable to apply a first channel estimate to the delay buffer symbol output, and apply a conjugate of a first channel estimate to the delay buffer symbol output and produce non STTD encoded symbols;
a lower processing branch operable to read delayed delay buffer symbol outputs, apply a conjugate of a second channel estimate and a STTD decoder scheme to the delay buffer symbol output to produce non STTD encoded symbols; and
a combiner operable to combine the non STTD encoded symbols of the upper processing branch and non STTD encoded symbols lower processing branch.
15. The HSDPA rake receiver of claim 14 , wherein a first portion of the received signal is operated on by a first channel estimate function.
16. The HSDPA rake receiver of claim 14 , wherein the upper branch operate on bits that have neither been flipped nor rearranged.
17. The HSDPA rake receiver of claim 14 , wherein the upper branch operate on bits that have been flipped or rearranged.
18. The HSDPA rake receiver of claim 17 , wherein the bits are flipped or rearranged according to a dedicated pattern.
19. The HSDPA rake receiver of claim 14 , wherein a de-spreader output is given by:
r 0 =h 1 s 0 −h 2 s 1 *+n 0
r 1 =h 1 s 1 +h 2 s 0 *+n 1 .
20. The HSDPA rake receiver of claim 14 , wherein the STTD decoder is given by
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21. The HSDPA rake receiver of claim 14 , wherein the lower branch is secured when processing non-STTD signals.
22. The HSDPA rake receiver of claim 14 , wherein the STTD decoder is within a rake receiver of a wireless communication system.
23. The HSDPA rake receiver of claim 22 , wherein the wireless communication systems at comprise CDMA systems, spread spectrum systems, and Orthogonal Frequency Division Multiplex (OFDM) systems.