Single Active RF Chain Uplink Multi-TRP Time Division Multiplexing
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Solution Overview
Problem
In 5G-NR systems, a single active RF frequency chain user equipment (UE) faces challenges in optimizing uplink slots for multiple transmission reception points (TRPs) when the time difference between transmission reception points is larger than the cyclic prefix (CP) length, leading to potential signal overlap and loss of symbols.
Innovation Solution
The UE employs a combined OFDM symbol scheme with a prolonged cyclic prefix and broader beam transmission to merge signals for multiple TRPs, allowing for optimized use of uplink slots by adding a prolonged cyclic prefix and using increased transmission power to compensate for beamforming and path-loss differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single active RF chain UE transmits UL signals to multiple TRPs with different timing advances, then the UE can maintain connectivity with multiple TRPs, but the UL signals will overlap in time domain causing loss of symbols
Solution Approach 1:
The patent segments the uplink transmission by creating separate combined OFDM symbols for each TRP target, with distinct timing advances. Each TRP's signal is processed independently through its own IFFT operation, allowing different TAs to be applied without interference. This segmentation enables the single RF chain to handle multiple TAs by time-multiplexing the segmented signals.
Solution Approach 2:
The patent introduces a new dimension of operation by merging the time domain and frequency domain processing. Specifically, it combines resources from two different slots (time dimension) into a single combined OFDM symbol (frequency domain representation), allowing simultaneous transmission to multiple TRPs with different TAs without time-domain overlap.
2Device complexity
If a single active RF chain UE uses traditional OFDM transmission for multiple TRPs, then the transmission structure remains simple, but the cyclic prefix length becomes insufficient to handle large propagation delay differences
Solution Approach 1:
The patent dynamically changes the cyclic prefix parameter by creating an extended CP that spans across the boundary of two original slots. This extended CP length is specifically tailored to accommodate the large propagation delay difference between multiple TRPs. The parameter change is adaptive, adjusting the CP duration based on the specific TA differences of the targeted TRPs.
Solution Approach 2:
The patent creates a composite OFDM structure that combines elements from two different slots into a single hybrid symbol. This composite structure includes resources from both slot n and slot n+1, forming a unified transmission unit that can simultaneously serve multiple TRPs with different timing requirements while maintaining OFDM orthogonality.
3Productivity
If a single active RF chain UE merges resources from two slots for combined OFDM symbol transmission, then the uplink slot utilization is improved, but the beamforming and path-loss compensation becomes more complex
Solution Approach 1:
The patent performs preliminary beamforming and power control calculations before the actual transmission. The UE determines the appropriate beam directions and power levels for each TRP based on pre-acquired channel state information. This preliminary preparation allows the combined OFDM symbol to be transmitted with optimized beamforming weights and power distribution, reducing the complexity during real-time transmission.
Solution Approach 2:
The patent creates a universal combined OFDM symbol structure that can simultaneously serve multiple TRPs with different characteristics. This unified structure incorporates resource elements from different slots and applies multipliers to adjust power levels for each TRP, making it a versatile transmission format that handles diverse TRP requirements through a single standardized procedure.
Data Source
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AI summary
There are provided apparatuses, methods and computer program products. In accordance with an embodiment, there is disclosed a method comprising obtaining by a terminal device first multiplexing symbols including at least one cyclic prefix for transmission to a first transmission reception point; obtaining by the terminal device second multiplexing symbols including at least one cyclic prefix for transmission to a second transmission reception point, wherein the first multiplexing symbols and the second multiplexing symbols have an overlap area; and creating by the terminal device a combined multiplexing symbol for the overlap area, which includes signals for the first transmission reception point and the second transmission reception point.