Differential Modulation With ±π/2 Phase Transitions for Low PAPR
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Solution Overview
Problem
Modern cellular communication systems face high peak-to-average power ratio (PAPR) issues in transmitted signals, leading to increased power consumption in power amplifiers, particularly in battery-operated devices, which is undesirable.
Innovation Solution
A modulation method that limits phase transitions between consecutive modulation symbols to less than or equal to ±π/2, using a database for mapping rules to generate modulation symbols, and allocates these symbols to sub-carriers for transmission, reducing PAPR and enabling efficient power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional modulation methods (QPSK, QAM) are used, then data transmission rate is improved, but peak-to-average power ratio increases leading to higher power consumption
Solution Approach 1:
The patent changes the modulation parameter by limiting phase transitions between consecutive symbols to ±π/2, which fundamentally alters the signal characteristics to reduce PAPR while maintaining data transmission capability through differential encoding
Solution Approach 2:
The patent segments the modulation process into differential encoding where each symbol's phase is relative to the previous symbol, allowing independent control of phase transitions to satisfy the ±π/2 constraint while transmitting multiple bits per symbol
2Measurement precision
If reference signals are delivered for phase coherence, then demodulation accuracy is improved, but signaling overhead increases
Solution Approach 1:
Instead of transmitting reference signals from transmitter to receiver to establish phase coherence, the patent inverts the approach by having the receiver establish phase coherence through differential comparison of consecutive received symbols, eliminating the need for dedicated reference signals
3Loss of energy
If phase transitions are limited to ±π/2, then power amplifier efficiency is improved, but modulation flexibility is reduced
Solution Approach 1:
The patent compensates for reduced phase transition flexibility by changing the information encoding parameter from absolute phase to differential phase, allowing multiple bit combinations to be represented within the constrained ±π/2 phase transition range
Solution Approach 2:
The patent adds the time dimension to phase encoding by using differential phase comparison between consecutive symbols, creating a new degree of freedom that enables high-rate data transmission despite constraints on instantaneous phase transition magnitude
Data Source
AI summary
This document discloses a solution for modulating and demodulating signals transferred over a communication channel. According to an aspect, a method comprises: storing a database for mapping rules for mapping a block of N bits into M modulation symbol phase transitions, wherein a phase transition between consecutive modulation symbols is limited to less than or equal to ∓π/2, wherein M is smaller than N, and wherein M is the smallest number required for realizing 2N different phase-transition combinations; determining an initial phase; acquiring a block of N bits and modulating the block of N bits into M phase symbol transitions from the initial phase by using bit values of the block of N bits and the mapping rules, thus acquiring M modulation symbols; performing said determining, acquiring, and modulating for further blocks of N bits, thus acquiring a sequence of K modulation symbols; allocating the sequence of K modulation symbols to sub-carriers of a multi-carrier symbol and causing transmission of the multi-carrier symbol over a radio interface.