NB-IoT DMRS Phase Rotation for PAPR Reduction
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Solution Overview
Problem
Current wireless communication systems face challenges in efficiently transmitting demodulation reference signals (DMRS) in Narrowband-Internet of Things (NB-IoT) systems, particularly in minimizing Peak to Average Power Ratio (PAPR/CM) and inter-cell interference, while ensuring compatibility with legacy LTE systems.
Innovation Solution
A method is introduced to define an NB-PUSCH frame structure for single tone transmission, determining the position of DMRS symbols, generating DMRS sequences, and applying phase rotation to minimize PAPR/CM, with initial phase values set using cell ID and specific units, and compensating for timing offsets across multiple terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DMRS is transmitted in NB-IoT system, then channel estimation accuracy is improved, but PAPR/CM increases
Solution Approach 1:
The patent applies phase rotation to DMRS sequences by changing the phase parameter. Specifically, a phase rotation value is applied to the DMRS sequence to reduce PAPR/CM while maintaining channel estimation accuracy. The phase rotation modifies the signal parameters without changing the fundamental DMRS structure, allowing optimization of power characteristics.
2Productivity
If DMRS sequence is generated for multiple terminals, then system capacity is improved, but timing offset occurs
Solution Approach 1:
The patent applies different cyclic shift values to DMRS sequences of different terminals. Each terminal is assigned a specific cyclic shift parameter, creating locally differentiated signal characteristics. This allows multiple terminals to transmit DMRS simultaneously without causing timing offset interference, as each terminal's DMRS has a unique cyclic shift property.
3Reliability
If DMRS transmission is added to NB-IoT, then demodulation performance is improved, but inter-cell interference increases
Solution Approach 1:
The patent applies cyclic shifting to DMRS sequences, which inverts the approach of using identical sequences. By applying different cyclic shifts to different cells or terminals, the patent transforms potential interference into orthogonal or near-orthogonal signals. This inversion strategy maintains demodulation performance while reducing inter-cell interference through sequence differentiation.
Data Source
AI summary
The present specification relates to a method for transmitting, by a terminal, a demodulation reference signal (DMRS) in a wireless communication system supporting narrow-band (NB)-Internet of things (IOT), the method comprising: generating, for single tone transmission, a reference signal sequence to be used for demodulation; mapping the reference signal sequence to a plurality of symbols; and transmitting, in the plurality of symbols, the demodulation reference signal to a base station by using a single tone, wherein phase rotation is applied to each of the plurality of symbols.