QAM Encoding for Zero-Crossing Avoidance in Wireless Transceivers
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Solution Overview
Problem
Designing a wireless transceiver that satisfies size and power constraints while avoiding zero-crossing conditions in quadrature amplitude modulation, which can degrade adjacent-channel-power and error-vector-magnitude performance.
Innovation Solution
Implementing zero-crossing-avoidance encoding for quadrature amplitude modulation by modifying the phase and amplitude of symbols to ensure an absolute phase difference between consecutive symbols is substantially different than 180 degrees, and generating a correction list to identify encoded symbols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional quadrature amplitude modulation is used, then data transmission can be achieved, but zero-crossing conditions occur which degrade adjacent-channel-power and error-vector-magnitude performance
Solution Approach 1:
The patent applies parameter changes by modifying the phase and amplitude parameters of modulation symbols. Specifically, when a zero-crossing condition is detected (phase difference of 180 degrees between consecutive symbols), the system changes the phase and/or amplitude parameters of the affected symbol to eliminate the zero-crossing condition, thereby resolving the technical contradiction between achieving data transmission and maintaining performance metrics
2Reliability
If zero-crossing-avoidance encoding is implemented, then adjacent-channel-power and error-vector-magnitude performance metrics are satisfied, but device complexity increases due to additional encoding and correction list generation
Solution Approach 1:
The patent implements preliminary action by detecting zero-crossing conditions and preemptively modifying the affected symbols before they cause performance degradation. The system identifies when a symbol would create a zero-crossing condition (180-degree phase difference with previous symbol) and proactively adjusts the phase and amplitude parameters to prevent the harmful effect, rather than reacting after degradation occurs
Solution Approach 2:
The system employs feedback mechanisms by generating a correction list that tracks which symbols were modified during zero-crossing-avoidance encoding. This feedback information is transmitted along with the modulated signal, allowing the receiver to properly decode the symbols by reversing the modifications, thus managing the added complexity through structured feedback
Data Source
AI summary
An apparatus for wireless communication is disclosed that performs zero-crossing-avoidance encoding for quadrature amplitude modulation. In an example aspect, the apparatus includes a polar transceiver configured to be coupled to an antenna. The polar transceiver is configured to transmit, via the antenna, data including multiple symbols associated with quadrature amplitude modulation. The multiple symbols include multiple sets of two consecutive symbols. An absolute value of a phase difference between the two consecutive symbols within each set of the multiple sets is substantially different than 180 degrees.