D2D Relay Selection Using DMRS Scrambling Sequences
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Solution Overview
Problem
In 3GPP LTE systems, devices outside base station coverage face challenges in identifying neighboring UEs within coverage and determining their ability to act as relays for Device-to-Device (D2D) communication, leading to significant time delays.
Innovation Solution
A method involving the reception of a Physical Sidelink Discovery Channel (PSDCH) with a De-Modulation Reference Signal (DMRS) to determine UE coverage and relay capability, using scrambling sequences and initializing parameters like RNTIs, base sequence numbers, and DMRS configurations to differentiate between UEs in and out of coverage, and those capable of operating as relays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a UE located outside base station coverage performs D2D communication by identifying neighboring UEs, then D2D communication can be established, but considerable time is required to identify neighboring UEs and determine their relay capability
Solution Approach 1:
The patent applies preliminary action by pre-configuring UEs with specific scrambling sequences and RNTI values before they engage in D2D communication. UEs inside coverage are pre-configured with base station-assigned RNTIs, while UEs outside coverage use pre-configured default RNTIs. This pre-preparation eliminates the need for time-consuming real-time identification and capability determination during the actual D2D setup process.
Solution Approach 2:
The patent uses scrambling sequences as an intermediary mechanism to convey information about UE coverage status and relay capability. Instead of direct communication between UEs to exchange capability information, the scrambling sequence acts as a mediator that encodes this information in a way that can be efficiently detected by receiving UEs through the PSDCH and PSCCH channels.
2Measurement precision
If UEs use scrambling sequences and RNTIs to identify coverage status and relay capability, then identification accuracy is improved, but the system complexity increases due to additional signaling and processing
Solution Approach 1:
The patent applies parameter changes by utilizing existing physical channel parameters (scrambling sequences, RNTIs) for their dual purpose of both channel access and information conveyance. By changing the values or assignments of these parameters based on UE coverage status, the system achieves accurate identification without adding separate complex signaling mechanisms. The same parameters used for random access are repurposed to encode coverage and capability information.
3Loss of time
If UEs outside coverage use pre-configured RNTIs and scrambling sequences, then quick relay identification is achieved, but reliability may be compromised if pre-configuration is insufficient or incorrect
Solution Approach 1:
The patent applies partial action by using a subset of the full RNTI space for out-of-coverage UEs. Instead of requiring complete and exhaustive pre-configuration of all possible scenarios, the system uses a limited set of pre-configured default RNTIs and scrambling sequences that are sufficient for the specific D2D relay scenario. This partial pre-configuration achieves quick identification while maintaining adequate reliability for the intended use case.
Data Source
AI summary
A disclosure of the present specification provides a method for selecting, by a user equipment (UE) located outside a coverage of a base station, a neighboring UE with which the UE will perform device-to-device (D2D) communication. According to the method, it is possible to quickly find out whether a neighboring UE is located within the coverage of a base station and is capable of operating as a relay, through a DMRS and a detection signal received from the neighboring UE.