DFT-s-OFDM Downlink Multiplexing for Multi-User Scheduling
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Solution Overview
Problem
DFT-s-OFDM restricts scheduling a single user over one DFT-s-OFDM symbol, reducing scheduling efficiency in downlink multi-user communication systems.
Innovation Solution
Implementing DFT transformation, subcarrier mapping, and inverse DFT (IDFT) processes to transmit DFT-s-OFDM signals, allowing multiplexing of data symbols targeting multiple users before the DFT precoder, thereby enabling multi-user scheduling in one DFT-s-OFDM symbol while maintaining low peak-to-average power ratio (PAPR).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If DFT-s-OFDM is used for downlink transmission, then peak-to-average power ratio (PAPR) is reduced and energy efficiency is improved, but scheduling efficiency deteriorates due to restriction to single user per symbol
Solution Approach 1:
The patent merges multiple users' data symbols into a single DFT-s-OFDM symbol by multiplexing them in the frequency domain through subcarrier allocation. Multiple users share the same time-frequency resource block with different subcarrier assignments, allowing the system to maintain low PAPR characteristics while serving multiple users simultaneously, thus resolving the contradiction between energy efficiency and scheduling efficiency.
Solution Approach 2:
The patent introduces frequency domain multiplexing as an additional dimension for user separation. Instead of limiting to single user per symbol in the time domain, users are differentiated by their subcarrier assignments within the frequency domain, effectively adding a new dimension (frequency resources) to accommodate multiple users while preserving the low PAPR benefit of DFT-s-OFDM.
2Loss of energy
If single user is scheduled per DFT-s-OFDM symbol, then low PAPR is maintained, but spectral efficiency deteriorates due to underutilization of available resources
Solution Approach 1:
The patent combines multiple users' transmissions within a single DFT-s-OFDM symbol structure. By allocating different subcarriers to different users within the same resource block, the system fully utilizes the available frequency resources while maintaining the inherent low PAPR property of DFT-s-OFDM, thereby resolving the contradiction between PAPR control and spectral efficiency.
Solution Approach 2:
The patent makes the DFT-s-OFDM symbol structure universal by enabling it to carry multiple users' data simultaneously through frequency domain multiplexing. The same DFT-s-OFDM framework that originally served single user is extended to serve multiple users, making the transmission structure multi-functional and thereby improving spectral efficiency without sacrificing PAPR performance.
Data Source
AI summary
A method performed by at least one processor of a network node operating in a wireless communication network includes receiving data associated with a plurality of users. The method further includes performing, by a discrete Fourier transform (DFT) coder, a DFT transformation on the data associated with the plurality of users. The method further includes performing, on the output of the DFT coder by a subcarrier mapper, subcarrier mapping that maps the output of the DFT coder to a set of subcarriers. The method further includes performing an inverse DFT (IDFT) on the output of the subcarrier mapper. The method further includes transmitting, over the wireless communication network, the output of the IDFT as a DFT spread optical frequency division multiplexing (DFT-s-OFDM) signal.