Bit Error Rate Testing Using Mixed Scrambled Unscrambled Signals
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Solution Overview
Problem
Existing analyzers face challenges in determining the bit error rate (BER) of devices under test (DUTs) that do not have the capability to enter a test mode and generate pseudorandom bit streams for BER measurements.
Innovation Solution
The method involves receiving a signal from the DUT with interspersed scrambled and unscrambled bits, generating a test bit sequence using a selected scrambling algorithm, and comparing the received scrambled bits to determine the BER without forcing the DUT into a test mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the DUT is placed in test mode to generate PRBS signal for BER measurement, then BER measurement capability is improved, but device complexity and operational restrictions increase
Solution Approach 1:
The DUT uses its own internal scrambling mechanism and normal operating data to perform BER measurement. The device serves itself by utilizing its existing scrambling functionality rather than requiring external test equipment or special test modes, thereby eliminating the need for separate test mode infrastructure
Solution Approach 2:
The same scrambling mechanism used for normal data transmission is also utilized for BER measurement purposes. This multi-functional approach allows the scrambling circuit to serve both data encryption and quality measurement functions, eliminating the need for dedicated test mode hardware
2Adaptability or versatility
If the DUT operates in normal mode with scrambled data, then operational flexibility is improved, but BER measurement accuracy deteriorates due to inability to separate scrambled from unscrambled bits
Solution Approach 1:
The analyzer receives feedback about which bits are scrambled and which are unscrambled based on the known pattern structure. This feedback mechanism allows the system to selectively process only the scrambled portions for BER measurement while ignoring unscrambled portions, maintaining accuracy despite mixed signal content
Solution Approach 2:
The measurement system extracts only the scrambled bit portions from the mixed signal for BER analysis. By separating and isolating the relevant scrambled data segments from the unscrambled portions, the system achieves accurate BER measurement without requiring the entire signal to be in test mode
3Ease of operation
If scrambled bits are measured without accounting for unscrambled portions, then measurement simplicity is improved, but measurement accuracy deteriorates due to misalignment between expected and actual bit patterns
Solution Approach 1:
The system performs preliminary identification of scrambled versus unscrambled bit boundaries before conducting BER measurement. By pre-processing the signal to mark and distinguish different bit types, the subsequent measurement process can proceed with proper alignment and without complex real-time discrimination
Solution Approach 2:
The signal is segmented into distinct scrambled and unscrambled portions based on the known pattern structure. This segmentation allows the measurement system to process each segment appropriately, applying BER analysis only to scrambled portions while maintaining correct bit alignment throughout
Data Source
AI summary
A device under test (DUT) is tested by: receiving a signal transmitted by the DUT, wherein the signal includes first portions that include scrambled bits produced from a selected bit pattern and a selected scrambling algorithm, and further includes second portions that include unscrambled bits, the first portions and second portions being interspersed within the signal; detecting received scrambled bits within the received signal; generating a test bit sequence using the selected scrambling algorithm and the selected bit pattern, including generating a bit of the test bit sequence for each of the received scrambled bits within the received signal, and not generating a bit of the test bit sequence for each of the received unscrambled bits within the received signal; and comparing the received scrambled bits to the test bit sequence to determine a bit error rate of the received signal.