DFT-s-OFDM Reference Signal Filtering for Low-PAPR Uplink
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Solution Overview
Problem
Existing communication technologies face challenges in reducing the peak-to-average power ratio (PAPR) of uplink signals in cellular networks, particularly in DFT-s-OFDM waveforms, leading to power constraints and reduced coverage, especially for cell edge users, and lack clear mechanisms for spectrum shaping of data and DMRS sequences, which affect channel estimation and data demodulation.
Innovation Solution
Implementing specific transmitter architectures that filter DFT-s-OFDM data and DMRS signals using data and RS filters with a one-to-one relationship, followed by port mapping, rotation, and DFT transformations to generate waveforms with low PAPR, ensuring identical channel estimation performance across antenna ports.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If OFDM is used for transmission, then transmission capacity is improved, but PAPR increases causing power constraints and reduced coverage
Solution Approach 1:
The patent segments the reference signal into multiple sequences and applies different filtering operations to different segments. Specifically, the reference signal is divided into first and second sequences, where the first sequence undergoes spectrum shaping filtering while the second sequence uses a different filter, allowing differentiated PAPR management across signal segments
Solution Approach 2:
The patent applies local quality by using different filtering characteristics for different parts of the reference signal. The first sequence uses a filter designed for low PAPR while the second sequence uses a different filter, creating localized optimization of signal properties in different frequency or time regions
2Power
If spectrum shaping filtering is applied to reduce PAPR, then power constraints are improved, but reference signal performance may deteriorate
Solution Approach 1:
The patent changes parameters by selecting specific filtering characteristics and sequence types (e.g., Zadoff-Chu sequences, constant amplitude sequences) that maintain reference signal properties while achieving low PAPR. The filter design parameters are optimized to preserve autocorrelation and cross-correlation properties essential for channel estimation
3Adaptability or versatility
If multiple DMRS sequences are used for multiple streams, then multi-user support is improved, but PAPR control becomes more difficult
Solution Approach 1:
The patent segments the reference signal into multiple sequences corresponding to different antenna ports or user streams. Each sequence can be independently filtered and processed, allowing multiple users to transmit simultaneously while maintaining individual PAPR control through separate filtering operations on each sequence
Solution Approach 2:
The patent enables dynamic assignment of different filtering characteristics to different DMRS sequences based on channel conditions and user requirements. The system can adaptively select which sequences undergo spectrum shaping and which use alternative filtering, providing flexible multi-user support with coordinated PAPR management
Data Source
AI summary
Embodiments of the present disclosure relate to systems and methods to generate a signal in a communication network. The method comprises fdtering a discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM) data signal, and one of a DFT-S-OFDM and orthogonal frequency division multiplexing (OFDM) reference signal (RS) using a data filter and a RS filter respectively, to produce filtered data signal and filtered RS. The RS filter has one to one relationship with the data filter. Thereafter, port mapping the filtered RS to a corresponding port assigned to the transmitter to obtain port mapped filtered RS, wherein the port mapped filtered RS comprises a first subset of non-zero locations comprising of the filtered RS values and a second subset of zero locations comprising of zero values.