Multi-Stream DFT-s-OFDM Precoding for Low-PAPR Uplink Signals
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Solution Overview
Problem
Existing communication protocols support only multi-stream cyclic prefix-orthogonal frequency division multiplexing (CP-OFDM) waveforms, which have high signal peak-to-average power ratio (PAPR), limiting average output power and uplink coverage. The DFT-s-OFDM waveform offers lower PAPR but lacks corresponding multi-stream transmission solutions.
Innovation Solution
A signal transmission method using a multi-stream DFT-s-OFDM waveform with phase offset precoding between transmit antenna ports, employing a codebook with non-zero elements causing phase differences, and π/2-BPSK modulation to improve demodulation performance and spectral efficiency without affecting low PAPR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If CP-OFDM waveform is used for multi-stream signal transmission, then existing protocol compatibility is improved, but signal peak-to-average power ratio (PAPR) increases
Solution Approach 1:
The patent changes the waveform parameter from CP-OFDM to DFT-s-OFDM, which fundamentally alters the signal generation process by inserting a DFT operation before the OFDM modulation. This parameter change maintains protocol compatibility while reducing PAPR through the properties of DFT-spread signals.
2Loss of energy
If DFT-s-OFDM waveform is used, then peak-to-average power ratio (PAPR) is reduced, but multi-stream transmission capability is lost
Solution Approach 1:
The patent segments the signal transmission process into multiple independent streams, each undergoing separate DFT-s-OFDM modulation. Multiple streams are then combined and transmitted simultaneously through multiple antenna ports, enabling multi-stream capability while preserving the low PAPR characteristic of DFT-s-OFDM.
Solution Approach 2:
The patent merges multiple DFT-s-OFDM streams across different antenna ports to create a combined transmission signal. This merging operation allows the system to achieve multi-stream transmission capacity while each individual stream maintains the low PAPR property, and the combined signal benefits from diversity gain.
3Object-generated harmful factors
If phase difference is introduced between transmit antenna ports, then inter-stream interference is reduced, but codebook complexity increases
Solution Approach 1:
The patent introduces asymmetric phase differences between transmit antenna ports, where each antenna port is assigned a specific phase offset relative to a reference port. This asymmetric phase configuration creates orthogonal signaling spaces that reduce inter-stream interference. The codebook is designed to reflect these asymmetric phase relationships, providing a structured approach to managing complexity.
Data Source
AI summary
This application discloses a signal transmission method and apparatus, to implement signal transmission by using a multi-stream DFT-s-OFDM waveform. The method includes: precoding N streams of signals based on a first codebook before sending, to obtain N1 precoded signals, where a quantity of non-zero elements in each row of the first codebook is 1, the first codebook causes a phase difference between two of the N streams of signals, and N and N1 are integers greater than 1; and sending the N1 precoded signals. A transmitting end introduces a phase offset between two transmit antenna ports in a precoding process, so that equivalent inter-stream interference is optimal after channel equalization is performed at a receiving end, to improve demodulation performance of the receiving end.