User Terminal DMRS Mapping for Low Latency Control Signal Demodulation
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Solution Overview
Problem
In future radio communication systems, the signal configuration of demodulation reference signals (DMRS) and downlink control signals during pre-coding increases overhead, which affects resource utilization efficiency and latency.
Innovation Solution
A user terminal is designed with a receiver, channel estimator, and demodulator that maps the DMRS to symbols coinciding or preceding the downlink control signal in a subframe, allowing for efficient channel estimation and demodulation of the downlink control signal without increasing overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the demodulation reference signal is mapped to forward symbols in the subframe to reduce processing time, then latency is reduced, but the overhead of the demodulation reference signal increases
Solution Approach 1:
The patent merges the function of demodulating both the downlink control signal and downlink data signal into a single demodulation reference signal mapped to forward symbols. By using one reference signal for both purposes instead of separate reference signals, the overhead is reduced while still enabling low-latency processing since the reference signal is available early in the subframe.
Solution Approach 2:
The demodulation reference signal mapped to forward symbols serves multiple functions: it is used for demodulating both the downlink control signal and the downlink data signal. This multi-functionality reduces the total number of reference signals needed while maintaining the ability to perform both demodulation operations with low latency.
2Reliability
If pre-coding is applied to the downlink control signal to improve reception quality in high-frequency bands, then reception quality is improved, but the overhead of the demodulation reference signal increases
Solution Approach 1:
The patent combines the reference signal requirements for pre-coded downlink control signals with the existing forward-symbol-mapped demodulation reference signal. By reusing the same reference signal structure and resources, the system achieves improved reception quality through pre-coding without requiring additional reference signals that would increase overhead.
Solution Approach 2:
The patent changes the mapping parameters of the demodulation reference signal to coincide with or precede the downlink control signal symbols. This parameter adjustment allows the reference signal to be used for both control signal demodulation (benefiting from pre-coding) and data signal demodulation, avoiding overhead increase while maintaining improved reception quality.
3Quantity of substance
If the demodulation reference signal is mapped to coincide or precede the downlink control signal, then overhead is prevented from increasing, but the channel estimation accuracy may be affected
Solution Approach 1:
The patent positions the demodulation reference signal to be mapped at the same symbols as or before the downlink control signal. This preliminary positioning ensures that the reference signal is available early for channel estimation without requiring additional overhead resources. The channel estimation can proceed using this early-available reference signal, maintaining accuracy while preventing overhead increase.
Data Source
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AI summary
A user terminal receives a downstream link data signal, a demodulation reference signal for demodulating the downstream link data signal, and a downstream link signal including a downstream link control signal; calculates a channel estimation value using the demodulation reference signal; demodulates the downstream link data signal using the channel estimation value; and demodulates the downstream link control signal using the channel estimation value calculated from the demodulation reference signal mapped to a symbol before a symbol to which the downstream link control signal is mapped in a sub-frame.