Sidelink Precoding Using Unprecoded Reference Signal Feedback
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Solution Overview
Problem
Sidelink communications in wireless networks are not effectively precoded, leading to interference with other communications due to implementation complexities, which affects reliability.
Innovation Solution
A first UE transmits an unprecoded reference signal to a second UE, allowing the second UE to measure and select a precoding matrix, with subsequent transmissions from the first UE being at least partially precoded based on the selected matrix, and this pattern is intermittently repeated to reduce interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sidelink communications use precoding to reduce interference, then communication reliability is improved, but implementation complexity increases due to the need for reference signal transmission and precoding matrix selection
Solution Approach 1:
The patent applies preliminary action by having the first UE transmit an unprecoded reference signal before the actual precoded data transmission. This reference signal (DMRS or CSI-RS) is sent in advance to allow the second UE to measure channel conditions and select an appropriate precoding matrix, enabling the subsequent data transmissions to benefit from precoding without interference. The preliminary reference signal transmission sets up the necessary channel state information before the main communication begins.
Solution Approach 2:
The patent segments the communication process into distinct phases: a reference signal transmission phase (unprecoded) and a data transmission phase (precoded). By separating these functions into different time slots or transmission opportunities, the system can first establish channel conditions through the reference signal, then apply precoding for the actual data communication, reducing the complexity of doing both simultaneously.
2Object-affected harmful factors
If continuous precoding is used for all sidelink transmissions, then interference is reduced, but measurement accuracy deteriorates because the reference signal cannot be transmitted unprecoded
Solution Approach 1:
The patent implements periodic action by alternating between unprecoded reference signal transmissions and precoded data transmissions in a periodic pattern. The reference signal is transmitted unprecoded at regular intervals to maintain accurate channel state information, while data transmissions utilize precoding to reduce interference. This periodic switching allows the system to benefit from both accurate measurements and interference reduction without requiring continuous precoding.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. Generally, the described techniques provide for a first user equipment (UE) transmitting, to a second UE, a sidelink message that includes an unprecoded reference signal. The second UE may measure the unprecoded reference signal and select a precoding matrix. The second UE may transmit a precoding matrix indication (PMI) to the first UE. The first UE may then transmit at least one sidelink message that is at least partially precoded in accordance with the PMI. In some cases, the first UE and the second UE may communicate according to a unprecoded transmission and precoded transmission pattern, where a new PMI is selected, using an unprecoded transmission, after a predefined number of precoded transmissions.