Uplink Reference Signal Grouping for Reduced-TTI Capacity
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Solution Overview
Problem
The reduction of transmission time interval (TTI) in LTE systems reduces the capacity of data transmission and uplink capacity, necessitating increased uplink reference signals that compromise data transmission efficiency.
Innovation Solution
The user terminal determines uplink reference signal positions using higher layer signaling and control information to send signals in symbol groups and subcarrier groups, allowing for increased time units and subcarriers without adding additional TTIs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the transmission time interval (TTI) is reduced to decrease round-trip time and data transmission delay, then the responsiveness of the system is improved, but the capacity of data transmission and uplink capacity decrease
Solution Approach 1:
The TTI is segmented into multiple shorter transmission time intervals (e.g., two 0.5 ms intervals instead of one 1 ms interval). This segmentation allows the system to achieve lower round-trip time for responsiveness while maintaining adequate data transmission capacity by distributing transmissions across multiple shorter intervals, thereby resolving the contradiction between reduced latency and maintained throughput.
2Loss of time
If the TTI is reduced to improve responsiveness, then the system latency is decreased, but the uplink capacity decreases
Solution Approach 1:
The system dynamically adjusts the number and configuration of uplink reference signals based on the reduced TTI structure. By making the reference signal configuration adaptive to the shorter transmission intervals, the system maintains sufficient uplink capacity for channel estimation and scheduling while achieving lower latency through the reduced TTI, thus resolving the contradiction between latency reduction and uplink capacity maintenance.
3Reliability
If sufficient uplink reference signals are sent in reduced TTI to ensure normal base station reception and scheduling, then the reliability of communication is improved, but the data transmission efficiency decreases
Solution Approach 1:
The system changes key parameters including the number of uplink reference signals, their time-frequency positions, and the TTI structure itself. By optimizing these parameters together - using multiple shorter TTIs with appropriately configured reference signals - the system achieves both reliable communication (through sufficient reference signals for accurate channel estimation) and maintained data transmission efficiency (by distributing signals across multiple intervals rather than consuming excessive resources in a single interval).
Data Source
AI summary
An uplink reference signal transmission method, a user terminal, and a base station. The uplink reference signal transmission method includes receiving, by a user terminal, first higher layer signaling indicating at least one uplink reference signal symbol group, where the at least one uplink reference signal symbol group is in 14 symbols or 12 symbols, and where each uplink reference signal symbol group of the at least one uplink reference signal symbol group includes at least one time unit, receiving, by the user terminal, first control information using a physical channel, wherein the first control information indicates an uplink reference signal symbol group corresponding to the user terminal, and sending, by the user terminal, at least one uplink reference signal in the uplink reference signal symbol group corresponding to the user terminal.