Short-TTI DMRS Control for Channel Estimation and Resource Overhead
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Solution Overview
Problem
In wireless communication systems with shortened Transmission Time Intervals (TTIs), the overhead of demodulation reference signals (DMRS) is significant, especially for short TTIs with 1 or 2 symbols, leading to inefficient use of radio resources and potential redundancy in channel condition estimation.
Innovation Solution
DMRS transmission is controlled independently from physical channels, allowing some TTIs to transmit without DMRS and others to transmit additional DMRS based on periodic patterns or higher layer signaling, optimizing resource use and channel estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DMRS is transmitted in every short TTI, then channel estimation can be performed for each TTI, but radio resource overhead becomes significant and inefficient
Solution Approach 1:
The patent extracts the DMRS transmission requirement from every TTI and applies it selectively only to TTIs containing physical channels (PUSCH/PDSCH). This removes unnecessary DMRS transmissions from TTIs that only carry control information, thereby reducing overhead while maintaining channel estimation accuracy where actually needed.
Solution Approach 2:
Instead of applying DMRS transmission universally to all TTIs (excessive action), the patent applies it partially only to TTIs with data channels. This partial application reduces the quantity of DMRS signals transmitted while ensuring sufficient channel estimation is performed for the specific TTIs that require it.
2Reliability
If multiple symbols are assigned to DMRS transmission in every TTI, then reliable demodulation is ensured, but the number of symbols available for data transmission decreases
Solution Approach 1:
The patent extracts the DMRS transmission requirement from the regular TTI structure and applies it only conditionally to TTIs containing physical channels. This removes unnecessary DMRS symbol allocations from control-only TTIs, increasing the number of symbols available for control information transmission without compromising demodulation reliability where needed.
Solution Approach 2:
The patent applies different DMRS transmission patterns to different TTIs based on their content. TTIs with physical channels receive full DMRS protection for reliable demodulation, while control-only TTIs use reduced or no DMRS transmission. This local differentiation optimizes both reliability and productivity for each TTI type.
3Loss of time
If TTI length is shortened to reduce latency, then latency reduction is achieved, but DMRS overhead becomes more significant relative to the TTI duration
Solution Approach 1:
The patent extracts unnecessary DMRS transmissions from short TTIs that only carry control information. By removing these redundant DMRS signals, the relative overhead ratio is reduced while maintaining the shortened TTI structure and its latency benefits.
Solution Approach 2:
Instead of applying full DMRS transmission to all short TTIs (which would create excessive overhead), the patent applies DMRS partially only to short TTIs containing physical channels. This partial application reduces the overall DMRS overhead ratio while maintaining sufficient channel estimation for data demodulation.
Data Source
AI summary
Embodiments of the present disclosure relate to the communication processes in a wireless communication system based on short TTIs. According to one embodiment of the present disclosure, there provide a method for communication by a base station. The method comprise: receiving, from a user equipment, an uplink demodulation reference signal, DMRS, in an uplink transmission time interval, TTI, of an uplink subframe, which supports two or more uplink TTIs. At least one uplink TTI supported by the uplink subframe is configured to only transmit uplink control information and/or uplink data without any uplink DMRS. In the other aspects of the present disclosure, there also provides methods for communication by a user equipment and corresponding apparatuses.