Preamble detection in a Multi-Antenna MIMO 802.16e Receiver
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Solution Overview
Problem
Existing OFDMA systems, such as those in the IEEE 802.16e WiMAX standard, face challenges in detecting preambles at Subscriber Stations due to interference from neighboring Base Stations, which degrades preamble detection performance.
Innovation Solution
The solution involves combining the shifted correlation values from each antenna to enhance preamble detection, using complex conjugation and multiplication of signal streams, and forming absolute values to improve correlation strength, thereby overcoming destructive interference from neighboring Base Stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If shifted auto-correlation is used for preamble detection, then detection capability is improved, but performance degrades in presence of neighboring Base Station interference
Solution Approach 1:
The patent applies the principle of converting harm into benefit by utilizing the interference from neighboring Base Stations in a constructive manner. Specifically, the method computes the shifted auto-correlation for each receive antenna independently, then combines these correlation values to detect the preamble. This approach transforms the previously destructive interference pattern into a detectable signal pattern, allowing the receiver to identify preambles even when multiple Base Stations are transmitting simultaneously. The key insight is that while individual correlation values may be affected by interference, the combination process enables robust detection by leveraging the structured nature of the interference patterns from neighboring cells.
2Reliability
If correlation values from multiple antennas are combined, then detection robustness is improved, but computational complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the preamble detection task into independent processing streams for each receive antenna. Each antenna's signal is processed separately through the shifted auto-correlation computation, and only the final combination step integrates the results from multiple antennas. This segmentation approach reduces the computational burden compared to processing all antenna signals simultaneously as a single complex stream, while still achieving robust detection through the combination of individual correlation results.
Data Source
AI summary
A preamble detector for a plurality of streams of baseband digitized signals has a plurality of preamble processors, each preamble processor coupled to an input and generating an output. Each preamble processor has an input coupled to a first delay, the output of the first delay coupled to a second delay generating an output. The first and second delay are substantially equal to a preamble part. A first multiplier generates an output from a conjugated output of the second delay output and a first delay output. A second multiplier generates an output from a conjugated first delay output and an input stream. The first and second multiplier outputs are accumulated over an interval, and the complex output of the accumulator is formed into a magnitude, thereby generating the output of each preamble processor. The outputs of the preamble processors are summed and compared to a threshold to generate a preamble detect.