QBL-MSK Modulation for TOA Signal Separation
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Solution Overview
Problem
Conventional spread spectrum communication systems face challenges in separating multiple path signal components, particularly when using serial quasi-band limited minimum shift keying (SQBL-MSK) modulation, as it generates both in-phase and quadrature correlation outputs, which hinders the implementation of the quadrature multiple frequency ranging (QMFR) algorithm.
Innovation Solution
A transmitter and receiver system that employs quasi-band limited minimum shift keying (QBL-MSK) modulation for the time of arrival (TOA) message to isolate the correlation output to either the in-phase or quadrature side, while using SQBL-MSK modulation for other data packet portions, with a switch to enable or disable serial formatting depending on the message type, allowing for effective separation of multiple path signal components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If SQBL-MSK modulation is used for TOA message, then data rate is increased by factor of two, but correlation output cannot be isolated to single side (I or Q)
Solution Approach 1:
The system dynamically switches between SQBL-MSK and QBL-MSK modulation schemes based on the message type being transmitted. A message type indicator field in the packet structure enables the receiver to select the appropriate demodulation and correlation processing mode, allowing flexible adaptation between high data rate (SQBL-MSK) and simplified correlation output (QBL-MSK) requirements
Solution Approach 2:
Different portions of the data packet use different modulation schemes tailored to their specific requirements. The TOA message portion uses QBL-MSK for clean correlation output, while other data portions use SQBL-MSK for higher data rate, optimizing each section's performance for its specific function
2Measurement precision
If QBL-MSK modulation is used for TOA message, then correlation output is isolated to single side enabling QMFR algorithm, but data rate is limited compared to SQBL-MSK
Solution Approach 1:
The data packet is segmented into different portions with different modulation schemes. The TOA message portion uses QBL-MSK modulation to enable precise multiple path signal separation through the QMFR algorithm, while other data portions use SQBL-MSK for higher data rate transmission. The message type indicator field enables the receiver to process each segment appropriately
3Ease of operation
If serial formatting is applied to simplify SYNC operation, then SYNC complexity is reduced, but QMFR algorithm cannot separate multiple path components
Solution Approach 1:
The system dynamically adjusts the formatting approach based on message type. For SYNC messages, serial formatting is applied to simplify operation. For TOA messages, the system switches to QBL-MSK modulation without serial formatting to enable precise multiple path signal separation through the QMFR algorithm
Data Source
AI summary
A transmitter is configured to transmit a time of arrival (TOA) message to a receiver applying a quadrature multiple frequency ranging (QMFR) algorithm for separating multiple path signal components. The transmitter includes (1) a modulator for generating a quasi-band limited minimum shift keyed (QBL-MSK) signal, (2) a serial formatter for generating a serial QBL-MSK (SQBL-MSK) signal, and (3) a switch for disabling the serial formatter, during a time that the TOA message is being transmitted to the receiver. The receiver includes (1) a matched filter for separating a data packet with the TOA message into in-phase (I) and quadrature (Q) spreading sequences, (2) an even sample mapping section, coupled to the matched filter, for outputting the even samples of the I and Q spreading sequences, (3) an odd sample mapping section, coupled to the matched filter, for outputting the odd samples of the I and Q spreading sequences, and (4) sliding correlator banks for receiving the even samples of the I and Q spreading sequences and the odd samples of the I and Q spreading sequences and outputting despread even I and Q samples and despread odd I and Q samples to a QMFR algorithm for separating multiple path signal components.