DFT-s-OFDM Symbols with Multiplexed Reference Sequences for Low PAPR
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Solution Overview
Problem
Existing communication systems face challenges with high Peak Power to Average Ratio (PAPR) in DFT-s-OFDM, intermodulation distortion, and phase noise in mm-wave systems, especially in high-speed scenarios and systems with oscillator frequency/phase variations, necessitating improved channel and phase tracking mechanisms.
Innovation Solution
The method involves time-multiplexing data and reference sequences within a single DFT-s-OFDM symbol, followed by DFT processing to achieve low PAPR waveforms, enabling efficient channel and phase tracking through multiplexed reference sequences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data sequence and reference sequence are time multiplexed and transmitted as independent symbols in separate slots, then channel equalization can be enabled through reference sequence, but the transmission time is increased and bandwidth utilization is reduced
Solution Approach 1:
The patent combines data sequence and reference sequence into a single DFT-s-OFDM symbol through time multiplexing within the same symbol duration. The reference sequence is multiplexed with data sequence in the time domain before DFT processing, allowing both to be transmitted simultaneously in one slot rather than requiring separate slots for data and reference signals.
Solution Approach 2:
The patent transitions from transmitting reference and data in separate time slots to multiplexing them within the same time slot by utilizing the time domain dimension within a single symbol. This dimensional change allows simultaneous transmission of both sequences without increasing overall transmission time.
2Productivity
If multiple sub-carriers are used in OFDM for bandwidth utilization, then bandwidth efficiency is improved, but Peak Power to Average Ratio (PAPR) increases
Solution Approach 1:
The patent segments the wideband carrier into multiple sub-carriers while using DFT-s-OFDM modulation to control the power distribution. The single-carrier DFT-s-OFDM structure divides the data into smaller segments that are processed through DFT, which inherently reduces the peak power compared to traditional multi-carrier OFDM while maintaining bandwidth efficiency.
Solution Approach 2:
The patent changes the modulation parameter from traditional OFDM to DFT-s-OFDM, which modifies how data is mapped to sub-carriers. This parameter change in the modulation scheme reduces PAPR while preserving the ability to utilize bandwidth efficiently through sub-carrier multiplication.
3Power
If single carrier modulation DFT-s-OFDM is used, then PAPR is reduced, but transmission speed and data rate are decreased
Solution Approach 1:
The patent employs dynamic resource allocation and flexible numerology configuration to optimize the balance between PAPR reduction and data rate. The system can adaptively adjust parameters such as sub-carrier spacing, symbol duration, and resource block allocation to maintain high data rates while preserving the low PAPR characteristics of DFT-s-OFDM.
Solution Approach 2:
The patent creates a composite modulation scheme that combines DFT-s-OFDM with advanced signal processing techniques and flexible numerology. This composite approach integrates the low PAPR benefit of single-carrier modulation with high data rate capabilities through optimized resource allocation and dynamic adaptation mechanisms.
4Reliability
If cyclic prefix is introduced to reduce Inter Symbol interference (ISI), then frequency selective fading robustness is improved, but symbol duration is increased
Solution Approach 1:
The patent uses a reduced cyclic prefix length that is sufficient to mitigate ISI in the specific operating conditions. By optimizing the cyclic prefix duration to be just enough to handle the channel memory, the system achieves adequate frequency selective fading robustness without excessively increasing symbol duration, thereby maintaining spectral efficiency.
Data Source
AI summary
The present disclosure discloses a method and a system for transmitting DFT-s-OFDM symbols. A data sequence for transmitting as an OFDM symbol is received as input from a data source. A reference sequence for transmitting along with the data sequence as the OFDM symbol is generated and time-multiplexed with the data sequence, to generate a multiplexed sequence. Thereafter, a Discrete Fourier Transform (DFT) operation is performed on the multiplexed sequence to generate a DFT-spread-Orthogonal Frequency Division Multiplexing (DFT-s-OFDM) symbol that is further processed for transmitting over a channel. The transmission of the reference sequence and the data sequence in a single OFDM symbol provides better bandwidth utilization and flexibility in modulation of the reference sequence and the data sequence.