Noise Estimator for Communications Systems Using Correlation
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Solution Overview
Problem
Existing noise estimation methods in wireless communications systems, particularly for OFDM systems, face challenges in accurately estimating signal quality during the preamble interval, leading to latency and inefficiencies in base-band processing, as they rely on methods with significant latency or require signal strength estimation during data intervals.
Innovation Solution
A noise estimator that calculates the noise level by subtracting the correlated signal level from the noise plus interference level, using a CORDIC processor to compute the magnitude and phase of the correlation output, and scaling the noise estimate by the preamble length, allowing for improved signal quality estimation during the preamble interval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing noise estimation methods are used during the preamble interval, then signal quality estimation is performed, but significant latency is introduced and base-band processing efficiency is reduced
Solution Approach 1:
The patent performs noise estimation during the preamble interval before data reception begins. By calculating the noise variance V(n) using the correlation method during this preliminary period, the system prepares signal quality information in advance, eliminating the need for post-data-processing estimation and thus reducing processing latency while maintaining accuracy
2Measurement precision
If noise estimation is performed during the data interval, then accurate signal strength estimation is achieved, but processing time is increased and efficiency is reduced
Solution Approach 1:
The system performs the computationally intensive noise estimation operation during the preamble interval rather than during data processing. By calculating C(n) and V(n) beforehand using the correlation method, the patent eliminates delays that would occur during data reception, thereby improving base-band processing efficiency without sacrificing estimation accuracy
Solution Approach 2:
The patent uses the preamble sequence as a representative copy of the signal characteristics to estimate noise variance. By correlating the received signal with the known preamble sequence, the system can infer noise properties from this copy without needing to process actual data, thus maintaining accuracy while improving efficiency
Data Source
AI summary
A SINR estimator receiving a symbol stream has a delay element coupled to the symbol stream to produce a delayed symbol stream, which is also coupled to a conjugator. A first multiplier forms a product from the symbol stream and the output of the conjugator, thereafter summing these values over an interval L and scaling by L to form a correlated power estimate Cn. A second multiplier forms a product from the symbol stream which is multiplied by the conjugate of the input, thereafter summing these values over the preamble interval 2L and scaling by 2L to form a non-correlated power estimate Pn. Cn and Pn are compared to generate an SINR estimate.