Base station for carrier offset recovery

• US 7,949,037 B2
• Filed: 09/18/2006
• Issued: 05/24/2011
• Est. Priority Date: 05/14/1998
• Status: Expired due to Fees

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Mesecher, David K, Jacques, Alexander M, Ozluturk, Fatih M
• Primary Examiner(s): Tran; Khai
• Application Number:
  US11/532,589
• Publication Number:
  US 20070014338A1
• Time in Patent Office: 1,709 Days
• Field of Search: 370/342, 370/330, 370/335, 370/230, 370/411, 370/320, 375/148, 375/130, 375/152, 375/375, 375/376, 375/342, 375/150
• US Class Current: 375/148
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/70755 Setting of lock conditions, e.g. threshold
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop
• CPC Class Codes: H04B 1/7093 Matched filter type
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04L 2027/0067 Phase error detectors
• CPC Class Codes: H04L 25/0212 of impulse response
• CPC Class Codes: H04L 27/0014 Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A base station for carrier offset recovery. An adaptive matched filter produces a filtered signal. A rake receiver provides relative path values of multipath components. A mixer generates channel impulse response estimates. A channel despreader despreads the filtered signal using the pseudo-noise signal generated to produce a despread channel signal of the selected channel. A pilot channel despreader despreads the filtered signal using a pseudo-noise signal generator to produce a despread pilot signal of the pilot channel. A hard decision processor determines a symbol value of the despread channel signal. A complex conjugate processor generates a complex conjugate of the symbol value as a correction signal. A phase-locked loop produces a phase correction signal to recover carrier offset.

Claims

1. A base station for carrier-offset recovery during reception of a communication signal over an air interface using a reduced pilot signal, the base station comprising:

an adaptive matched filter configured to produce a filtered signal of the received signals, the adaptive matched filter being provided with filter coefficients for filtering;

a rake receiver configured to provide relative path values of a plurality of multipath components of data on a selected channel in the received signals;

a mixer configured to mix a correction signal with outputs from the rake receiver to generate channel impulse response estimates which works as the filter coefficients of the adaptive matched filter;

a channel despreader for the selected channel coupled to the adaptive matched filter output configured to despread the filtered signal using the pseudo-noise signal generated for the selected channel to produce a despread channel signal of the selected channel;

a pilot channel despreader for a pilot channel coupled to the adaptive matched filter output configured to despread the filtered signal using a pseudo-noise signal generated for the pilot channel to produce a despread pilot signal of the pilot channel;

a hard decision processor configured to determine a symbol value of the despread channel signal of the selected channel in accordance with a modulation constellation;

a complex conjugate processor configured to generate a complex conjugate of the symbol value generated by the hard decision processor, the complex conjugate of the symbol value becoming the correction signal;

a phase-locked loop configured to produce a phase correction signal by measuring a phase difference of the despread pilot signal, the phase correction signal being mixed with the received signals to recover carrier offset.

2. The base station according to claim 1 further comprising a plurality of channel despreaders, each coupled to the adaptive matched filter output for despreading said filtered signal each using an associated pseudo-noise signal generator to produce a plurality of despread channel signals.

3. The base station according to claim 2 wherein the number of channel despreaders is three.

4. The base station according to claim 2 wherein the phase-locked loop phase correction signal is at a chip level and is applied to the received signals.

5. The base station according to claim 2 wherein each of the plurality of channels is a complex, bi-phase modulated signal comprised of symbols including in-phase and quadrature components representing data, the hard decision processor compares each despread channel signal symbol to one of four possible quadrature constellation points and assigns each of said symbols to a nearest constellation point, and the complex conjugate processor derotates each of the symbols by determining a complex conjugate of each of the assigned points to produce the correction signal.

6. The base station according to claim 2 wherein the phase-locked loop further comprises a plurality of inputs corresponding with the plurality of channel despreaders.

7. The base station according to claim 6 wherein the phase-locked loop further comprises:

a plurality of hard decision processors configured to determine a symbol value of the despread channel signals;

a plurality of complex conjugate processors configured to generate a complex conjugate of the symbol value generated by the hard decision processors;

a plurality of mixers configured to mix the complex conjugate of the symbol value with the delayed despread channel signals to generate error signals;

a plurality of converters configured to convert the error signals to phase error signals; and

a maximum likelihood combiner configured to combine the phase error signals by multiplying weights to the phase error signals to generate a phase correction signal.

8. The base station according to claim 7 wherein the number of channel despreaders is three.

9. The base station according to claim 1 wherein the phase-locked loop phase correction signal is at a symbol level and is mixed to an output of the rake receiver, despread channel signal from the channel despreader and despread pilot signal from the pilot channel despreader, respectively.

10. The base station according to claim 9 further comprising a plurality of channel despreaders, each coupled to the adaptive matched filter output configured to despread the filtered signal using an associated pseudo-noise signal generator to produce a plurality of despread channel signals.

11. The base station according to claim 10 wherein the number of channel despreaders is three.

12. The base station according to claim 10 wherein the phase-locked loop further comprises a plurality of signal inputs corresponding with the plurality of channel despreaders.

13. The base station according to claim 12 wherein the phase-locked loop further comprises:

a plurality of hard decision processors configured to determine a symbol value of the despread channel signals;

a plurality of complex conjugate processors configured to generate a complex conjugate of the symbol value generated by the hard decision processors;

a plurality of mixers configured to mix the complex conjugate of the symbol value with a delayed the despread channel signals to generate error signals;

a plurality of converters configured to convert the error signals to phase error signals; and

a maximum likelihood combiner configured to combine the phase error signals by multiplying weights to the phase error signals to generate a phase correction signal.

14. The base station according to claim 13 wherein the number of channel despreaders is three.