Two-Tone In-Phase Pi/2 BPSK Modulation for Low PAPR eMTC
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Solution Overview
Problem
Current two-tone modulation schemes for enhanced Machine-Type Communication (eMTC) technologies have high Peak-to-Average Power Ratio (PAPR), which is not acceptable for single-tone sub-PRB modulation schemes, and existing solutions like Quadrature Phase-Shift Keying (QPSK) also face similar issues, necessitating a method for two-tone in-phase pi/2 binary phase-shift keying (BPSK) with low PAPR for efficient communication in radio systems.
Innovation Solution
The method employs two-tone in-phase pi/2 BPSK sub-Physical Resource Block (sub-PRB) modulation using single carrier frequency-division multiple access (SC-FDMA), where pairs of bits are converted into modulation symbols using alternating BPSK symbol constellations rotated by pi/2 radians, and processed for transmission, reducing PAPR through Discrete Fourier Transform (DFT) operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If two-tone modulation using QPSK is used for eMTC, then data transmission capacity is improved, but PAPR increases significantly to 3.5 dB
Solution Approach 1:
The patent changes the modulation parameters by using pi/2 BPSK instead of QPSK, and by alternating between two different BPSK symbol constellations that are rotated by pi/2 radians relative to each other. This parameter change reduces PAPR from 3.5 dB to approximately 0.5 dB while maintaining the two-tone modulation structure for eMTC compliance
Solution Approach 2:
The patent introduces dynamic alternation between two different BPSK symbol constellations for the two tones. The symbol constellations are not fixed but switch between two possible configurations (rotated by pi/2 radians), which dynamically adapts the signal characteristics to reduce peak power while maintaining transmission capacity
2Loss of energy
If single-tone pi/2 BPSK is used for NB-IOT, then PAPR is reduced to 0.5 dB, but data transmission capacity is limited
Solution Approach 1:
The patent segments the data transmission into two parallel tone channels, each carrying pi/2 BPSK modulated data. By segmenting the transmission across two tones instead of using a single tone, the system achieves low PAPR (0.5 dB) while doubling the effective data transmission capacity compared to single-tone pi/2 BPSK
Solution Approach 2:
The patent merges two separate pi/2 BPSK modulated tone signals into a single transmitted signal. By combining the two tones with their respective modulated symbols, the system achieves both low PAPR (0.5 dB) and enhanced data transmission capacity, effectively merging the benefits of single-tone low-PAPR modulation with multi-tone capacity enhancement
Data Source
AI summary
A method and apparatus for communication, e.g. in an LTE system, that uses two tones with an in-phase pi/2 BPSK modulation with single carrier frequency-division multiple access (SC-FDMA). Pairs of input bits are converted to symbols using pi/2 BPSK, with each one of the pair of bits converted using a same symbol constellation, and successive pairs of bits converted using alternatingly different symbol constellations. The two constellations may be identical after a pi/2 radian rotation. Pairs of symbols corresponding to pairwise converted bits may be treated as the symbols for a pair of tones of a subsequent SC-FDMA, OFDMA, or similar processing operation.