Wireless backhaul
In the subject system, a receiver includes a feed forward circuit, a phase recovery circuit, and a feedback circuit. The feed forward circuit compensates for near reflections and provides an input to the phase recovery circuit and the feedback circuit. The phase recovery circuit performs phase recovery and provides phase recovery information to the feedback circuit. The feedback circuit adjusts and/or corrects a received symbol based at least in part on the received phase recovery information.
1. A receiver comprising:
a feedforward circuit comprising a first adaptive filter;
a feedback circuit comprising a second adaptive filter, wherein the feedback circuit is operable to adjust a current symbol according to phase recovery information; and
a phase recovery circuit comprising a third adaptive filter, wherein the phase recovery circuit is operable to generate the phase recovery information according to an output from the feedforward circuit, and wherein one or more taps of the third adaptive filter are based on one or more taps of the second adaptive filter.
2. The receiver of claim 1 , wherein the first adaptive filter comprises a finite impulse response (FIR) filter.
3. The receiver of claim 1 , wherein the second adaptive filter comprises a finite impulse response (FIR) filter.
4. The receiver of claim 1 , wherein the third adaptive filter comprises an impulse response (IIR) filter.
5. The receiver of claim 1 , wherein an adaptation of the first adaptive filter is based on a residual error from a data slicer.
6. The receiver of claim 1 , wherein an adaptation of the first adaptive filter is based on the phase recovery information.
7. The receiver of claim 1 , wherein the feedforward circuit is operable to reduce inter-symbol interference from a future symbol.
8. The receiver of claim 1 , wherein an adaptation of the second adaptive filter is based on a residual error from a data slicer.
9. The receiver of claim 1 , wherein an adaptation of the second adaptive filter is based on the phase recovery information.
10. The receiver of claim 1 , wherein the feedback circuit is operable to reduce inter-symbol interference from a past symbol.
11. The receiver of claim 1 , wherein an adaptation of the third adaptive filter is based on a residual error from a data slicer.
12. The receiver of claim 1 , wherein the phase recovery information is determined based on a predetermined pilot.
13. The receiver of claim 1 , wherein the phase recovery information comprises a phase rotation of the current symbol.
14. The receiver of claim 1 , wherein a delay between the feedforward circuit and the feedback circuit aligns symbol timing in the feedback circuit with the phase recovery circuit.
15. A receiver comprising:
a reflection removal circuit operable to remove an estimated inter-symbol interference (ISI) from a wireless signal, wherein the reflection removal circuit comprises a first adaptive filter;
a phase correction circuit operable to rotate the wireless signal by an estimated phase, wherein the phase correction circuit comprises a second adaptive filter, and wherein one or more taps of the second adaptive filter are based on one or more taps of the first adaptive filter;
a slicer operably coupled to the reflection removal circuit and the phase correction circuit, wherein the slicer is operable to estimate a channel and a series of symbols in the wireless signal; and
a phase distortion circuit operable to distort the series of symbols according to the estimated phase, wherein the phase correction circuit is operable to generate the estimated ISI according to the distorted series of symbols and the channel estimate.
16. The receiver of claim 15 , wherein the first adaptive filter comprises a finite impulse response (FIR) filter.
17. The receiver of claim 15 , wherein the second adaptive filter comprises a finite impulse response (FIR) filter.
18. A receiver comprising:
a reflection removal circuit operable to remove an estimated inter-symbol interference (ISI) from a signal received over a wireless channel, wherein the reflection removal circuit comprises a first adaptive filter, and wherein the first adaptive filter is adapted according to a channel estimate;
a phase recovery circuit operable to estimate a phase introduced by the wireless channel, wherein the phase recovery circuit comprises a second adaptive filter, and wherein one or more taps of the second adaptive filter are based on one or more taps of the first adaptive filter;
a phase correction circuit operable to rotate the signal received over the wireless channel by the estimated phase; and
a slicer operably coupled to the reflection removal circuit and the phase correction circuit, wherein the slicer is operable to generate the channel estimate and predict a series of symbols in the wireless signal, and wherein the estimated ISI is based on the series of symbols in the wireless signal.
19. The receiver of claim 18 , wherein the first adaptive filter comprises a finite impulse response (FIR) filter.
20. The receiver of claim 18 , wherein the second adaptive filter comprises a finite impulse response (FIR) filter.
21. The receiver of claim 18 , wherein the estimated ISI is distorted by the estimated phase.