Method and system for a reference signal (RS) timing loop for OFDM symbol synchronization and tracking
Aspects of a method and system for a reference signal (RS) timing loop for OFDM symbol synchronization and tracking may include tracking symbol timing in an Orthogonal Frequency Division Multiplexing (OFDM) signal based on at least a reference symbol set. A receiver timing may be adjusted based on at least the symbol timing. The symbol timing may be tracked by generating an output signal as a function of a guard time Δt g in a phase discrimination feedback loop. The reference symbol (RS) set may be generated in an RS extraction module or circuit, from at least a fast Fourier transform of the received OFDM signal. The receiver timing may be coarsely adjusted and then finely adjusted. The coarse receiver timing adjustment may be based on processing at least a primary synchronization signal and a secondary synchronization signal.
1. A timing acquisition and tracking system, comprising:
a timing module configured:
to compare a timing of a plurality of reference symbols within a reference symbol (RS) set associated with a symbol guard time to a reference clock signal to generate a plurality of error signals corresponding to the plurality of reference symbols,
to generate a weighted sum signal representative of a weighted integration of the plurality of error signals, and
to generate an output signal that varies as a function of the symbol guard time utilizing the weighted sum signal; and
a receiver configured to process a received signal utilizing a timing signal and to adjust the timing signal based on the output signal.
2. The timing acquisition and tracking system of claim 1 , wherein the receiver comprises:
a timing generator configured to generate an RS extraction timing signal and a slot timing signal based on the output signal.
3. The timing acquisition and tracking system of claim 2 , wherein the receiver further comprises:
a fast Fourier transform (FFT) module configured to perform an FFT of the received signal within an FFT sampling window to provide an FFT output signal, the FFT sampling window being based on the slot timing signal.
4. The timing acquisition and tracking system of claim 3 , wherein the receiver further comprises:
an RS extraction module configured to extract the RS set from the received signal utilizing the FFT output signal and the RS extraction timing signal.
5. The timing acquisition and tracking system of claim 1 , wherein the timing module comprises:
an integrator module configured to integrate the plurality of error signals to provide an integrated signal; and
an adder configured to provide the weighted sum signal by adding the plurality of error signals with the integrated signal.
6. The timing acquisition and tracking system of claim 5 , wherein the timing module further comprises:
a threshold module configured to generate the output signal based on the weighted sum signal.
7. The timing acquisition and tracking system of claim 6 , wherein the threshold module is further configured to generate a reset signal, and
wherein the integrator module is further configured to reset integration of the plurality of error signals in response to the reset signal.
8. The timing acquisition and tracking system of claim 7 , wherein the threshold module is further configured to compare a signal level of the weighted sum signal to a threshold signal level and to generate the reset signal if the signal level is greater than or equal to the threshold signal level.
9. The timing acquisition and tracking system of claim 5 , wherein the RS set is from among a plurality of RS sets corresponding to a plurality of subcarriers.
10. A timing acquisition and tracking system, comprising:
a receiver configured to decode a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) from a received signal utilizing a timing signal to extract a reference symbol (RS) set; and
a timing module configured to compare a timing of the RS set to a reference clock signal to generate an output signal which tracks a guard time of the RS set,
wherein the receiver is further configured to adjust the timing signal utilizing the output signal to process the received signal.
11. The timing acquisition and tracking system of claim 10 , wherein the receiver comprises:
a timing generator configured to generate an RS extraction timing signal and a slot timing signal based on the output signal.
12. The timing acquisition and tracking system of claim 11 , wherein the receiver further comprises:
a fast Fourier transform (FFT) module configured to perform an FFT of the received signal within an FFT sampling window to provide an FFT output signal, the FFT sampling window being based on the slot timing signal.
13. The timing acquisition and tracking system of claim 12 , wherein the receiver further comprises:
an RS extraction module configured to extract the RS set from the received signal utilizing the FFT output signal and the RS extraction timing signal.
14. The timing acquisition and tracking system of claim 10 , wherein the RS set is from among a plurality of RS sets,
wherein the timing module is further configured to compare a timing of the plurality of RS sets to the reference clock signal to generate a plurality of error signals, and
wherein the timing module comprises:
an integrator module configured to integrate the plurality of error signals to provide an integrated signal; and
an adder configured to provide a weighted sum signal representative of a weighted integration of the plurality of error signals by adding the plurality of error signals with the integrated signal.
15. The timing acquisition and tracking system of claim 14 , wherein the timing module comprises:
a threshold module configured to compare a signal level of the weighted sum signal to a threshold signal level and to generate a reset signal if the signal level is greater than or equal to the threshold signal level, and
wherein the integrator module is further configured to reset integration of the plurality of error signals in response to the reset signal.
16. A timing acquisition and tracking system, comprising:
a reference symbol (RS) phase discriminator configured to compare a timing of a plurality of reference symbols within an RS set associated with a symbol guard time to a reference clock signal to generate a plurality of error signals corresponding to the plurality of reference symbols;
a phase discrimination feedback loop configured to generate a weighted sum signal representative of a weighted integration of the plurality of error signals;
a threshold block configured to generate an output signal that varies as a function of the symbol guard time utilizing the weighted sum signal; and
a timing generator configured to process a received signal utilizing a timing signal and to adjust the timing signal based on the output signal.
17. The timing acquisition and tracking system of claim 16 , wherein the timing generator is further configured to generate an RS extraction timing signal and a slot timing signal based on the output signal.
18. The timing acquisition and tracking system of claim 17 , further comprising:
a fast Fourier transform (FFT) module configured to perform an FFT of the received signal within an FFT sampling window to provide an FFT output signal, the FFT sampling window being based on the slot timing signal.
19. The timing acquisition and tracking system of claim 18 , further comprising:
an RS extraction module configured to extract the RS set from the received signal utilizing the FFT output signal and the RS extraction timing signal.
20. The timing acquisition and tracking system of claim 16 , wherein the phase discrimination feedback loop comprises:
an integrator module configured to integrate the plurality of error signals to provide an integrated signal;
an adder configured to provide the weighted sum signal by adding the plurality of error signals with the integrated signal; and
a threshold module configured to compare a signal level of the weighted sum signal to a threshold signal level, and to generate a reset signal if the signal level is greater than or equal to the threshold signal level,
wherein the integrator module is further configured to reset integration of the plurality of error signals in response to the reset signal.