Short-TTI DMRS Scheduling for Lower Wireless Uplink Overhead
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Solution Overview
Problem
The reduction of symbols in a TTI for latency reduction in LTE systems leads to significant DMRS overhead and inefficient radio resource usage, especially in short TTIs with 1 or 2 symbols, as channel conditions may not vary much, necessitating unnecessary DMRS transmission.
Innovation Solution
DMRS transmission is controlled independently from physical channels, allowing for dynamic triggering or periodic patterns, with some TTIs transmitting DMRS and others not, and using separate control mechanisms to optimize resource usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DMRS transmission is performed in every TTI to maintain channel quality monitoring, then channel estimation reliability is improved, but radio resource efficiency deteriorates due to significant overhead in short TTIs
Solution Approach 1:
The patent implements periodic DMRS transmission patterns where DMRS is sent in certain TTIs and omitted in others, rather than transmitting in every TTI. This periodic approach maintains sufficient channel estimation reliability while significantly reducing the overhead and improving radio resource efficiency in short TTI scenarios.
Solution Approach 2:
The patent introduces dynamic control mechanisms that allow the network to flexibly adjust DMRS transmission timing and frequency based on actual channel conditions, traffic patterns, and quality requirements. This dynamic adaptation enables the system to maintain reliability when needed while conserving resources during stable conditions.
2Measurement precision
If DMRS transmission is performed in every TTI to ensure accurate channel quality determination, then measurement precision is improved, but device complexity increases due to separate control mechanisms
Solution Approach 1:
The patent integrates DMRS transmission control into existing physical channel structures and control planes, allowing the same control mechanisms to serve multiple functions including resource allocation, scheduling, and DMRS timing coordination. This multi-functionality approach avoids adding separate dedicated control systems.
3Speed
If short TTIs with 1 or 2 symbols are used to reduce latency, then speed is improved, but manufacturing precision deteriorates due to insufficient symbols for proper DMRS transmission
Solution Approach 1:
The patent employs periodic DMRS transmission where reference signals are sent at regular intervals within the short TTI structure. This periodic approach ensures that channel estimation is performed at sufficient intervals to maintain precision while accommodating the reduced symbol count in short TTIs.
Solution Approach 2:
The patent positions DMRS transmissions at optimal earlier symbols within the TTI structure to establish channel conditions before data transmission begins. This preliminary channel estimation allows the system to maintain precision even with fewer total symbols available in short TTI configurations.
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.