D2DMRS Cyclic Shift Selection for Interference Reduction
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Solution Overview
Problem
In Device to Device (D2D) Proximity Service (ProSe) for LTE systems, the collision of Demodulation Reference Signals (DMRS) between user equipment leads to significant link-level losses, particularly due to cyclic shifts that are not adequately differentiated, necessitating a method to reduce interference during reference signal transmission.
Innovation Solution
The method involves selecting a cyclic shift indication based on a unique identifier for each user equipment, generating a reference signal using a preset base sequence, and transmitting it to other user equipment, thereby ensuring orthogonality and reducing interference between signals on the same time-frequency resource.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If cyclic shift of DMRS is used to differentiate user equipment, then interference between reference signals is reduced, but blind detection of DMRS cyclic shift becomes necessary which increases receiver complexity
Solution Approach 1:
The patent introduces a cyclic shift indication field as an intermediary element that carries information about the cyclic shift configuration. Instead of requiring the receiver to blindly detect the cyclic shift, the indication field provides direct guidance, thereby reducing receiver complexity while maintaining interference differentiation between user equipment.
Solution Approach 2:
The cyclic shift indication field acts as a feedback mechanism from the transmitter to the receiver, providing explicit information about the cyclic shift configuration. This feedback eliminates the need for blind detection and allows the receiver to directly configure its demodulation parameters, reducing complexity while maintaining signal differentiation.
2Ease of manufacture
If identical DMRS are transmitted by different user equipment, then reference signal transmission is simplified, but significant link-level loss occurs due to collision
Solution Approach 1:
The patent applies local quality differentiation by using cyclic shift indication fields specific to each user equipment's reference signal. Each UE's reference signal carries its own cyclic shift indication, allowing localized differentiation without requiring complex global coordination. This maintains transmission simplicity while preventing collisions and link-level losses.
3Object-affected harmful factors
If cyclic shift of DMRS varies in pseudo-random manner, then interference is reduced across discovery periods, but blind detection and processing complexity increases
Solution Approach 1:
The cyclic shift indication field serves as an intermediary that conveys the pseudo-random cyclic shift configuration from the transmitter to the receiver. This eliminates the need for blind detection of pseudo-random patterns, reducing processing complexity while maintaining the interference reduction benefits of variable cyclic shifts across discovery periods.
Data Source
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AI summary
Embodiments of the present invention provide a reference signal transmission method and user equipment. The method includes: determining, by first user equipment, a first identifier related to the first user equipment; determining, by the first user equipment, a first cyclic shift indication from to-be-selected cyclic shift indications according to the first identifier; determining, by the first user equipment, first reference signal according to the first cyclic shift indication and a preset base sequence; and sending, by the first user equipment, the first reference signal to second user equipment. In the embodiments of the present invention, the to-be-selected cyclic shift indications are preset, and the first user equipment selects the first cyclic shift indication according to the first identifier related to the first user equipment, generates the first reference signal on a basis of the first cyclic shift indication and the preset base sequence, and then sends the first reference signal to the second user equipment, thereby implementing reference signal transmission in D2D communication.