Phase Offset Estimation for Satellite De-spreading
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Solution Overview
Problem
Existing phase offset estimation methods in satellite communication systems yield poor results at low signal-to-noise ratio (SNR) conditions due to degraded estimation accuracy when phase offsets are estimated in stages using only a small portion of the received signal's energy.
Innovation Solution
A method that estimates a common phase offset between successive block repetitions using multiple repetitions, allowing for coherent combining of received signals by calculating phase differences and utilizing Fast Fourier Transform (FFT) or Discrete Fourier Transform (DFT) to determine phase offset hypotheses, which improves estimation accuracy and reduces de-spreading loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If phase offset estimation is performed in stages using only a small portion of the received signal's energy, then the computational complexity is reduced, but the estimation accuracy is significantly degraded at low SNR
Solution Approach 1:
The patent combines all received signal energy from multiple block repetitions simultaneously for phase offset estimation, rather than processing repetitions in stages. This is achieved by constructing a matrix from all received repetitions and computing the phase offset using the full signal energy, which maintains estimation accuracy at low SNR while accepting increased computational complexity.
2Measurement precision
If more signal energy is used for phase offset estimation, then the estimation accuracy is improved, but the processing time and computational complexity increase
Solution Approach 1:
The patent replaces iterative sequential processing with a direct matrix-based computation approach. By formulating the phase offset estimation as a closed-form solution using matrix operations on all received repetitions simultaneously, the method achieves high estimation accuracy without the time loss associated with multiple iterative stages.
3Device complexity
If iterative phase offset estimation and combining is performed sequentially, then the device complexity is reduced, but the de-spreading loss increases at low SNR
Solution Approach 1:
The patent performs preliminary phase offset estimation using all received signal energy before combining the repetitions. By estimating the phase offset once using the complete signal energy from all repetitions and then applying this single estimation to correct all repetitions simultaneously, the method avoids the de-spreading loss that occurs when iterative sequential processing is used at low SNR.
Data Source
AI summary
Satellite communication systems utilize spreading by repetition techniques, including block repetition, to enable operation at low signal to noise conditions. A carrier frequency offset between a transmitter and a receiver results in phase offsets between repetitions. Thus, combining the repetitions requires estimation of the phase offset between the repetitions before coherent de-spreading can be performed. Disclosed herein are methods for estimating a phase offset between successive block repetitions. The methods may utilize more than two repetitions for determining a common phase offset between any two successive repetitions. In some embodiments, these methods may allow summation of repetitions with better coherency and/or with a lower de-spreading loss.