Beam Index Reference Signal Design for Initial Access
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Solution Overview
Problem
Conventional beam-scanning protocols in high-frequency wireless communications, such as millimeter Wave (mmW), face challenges in efficiently determining optimal beam directions due to high free-space path loss and the complexity of blind decoding multiple beamformed reference signals, which hinders coherent decoding and increases the number of blind decoding iterations.
Innovation Solution
The method employs different spreading sequences, generated by permutating a root sequence with modular permutation parameters, to encode beamformed reference signals, allowing implicit signaling of beam indices and reducing the need for encoding beam indices in physical broadcast channel (PBCH) signals, enabling coherent decoding of multiple signals and lowering the complexity of blind decoding iterations by dividing time intervals into sequences with the same and different spreading sequences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If beam indices are encoded in PBCH signals for each beam direction, then beam identification is achieved, but the number of blind decoding iterations increases and coherent decoding becomes difficult
Solution Approach 1:
The patent extracts the beam identification function from the PBCH signal encoding and implements it through a separate reference signal with a distinct sequence. This separation allows the UE to identify beams through reference signal sequence matching rather than decoding beam indices from PBCH, thereby reducing blind decoding complexity while maintaining identification accuracy.
Solution Approach 2:
The patent introduces a reference signal as an intermediary element that carries beam identification information through its sequence properties rather than through encoded data. The reference signal acts as a mediator between the gNB and UE, enabling beam identification through correlation-based detection instead of complex decoding operations.
2Productivity
If multiple beamformed reference signals are transmitted for beam scanning, then optimal beam direction determination is enabled, but the complexity of blind decoding multiple signals increases
Solution Approach 1:
The patent applies different local qualities (distinct spreading sequences) to different reference signals corresponding to different beam directions. Each reference signal has a unique sequence property that enables simple correlation-based detection, avoiding the need for complex blind decoding while maintaining the ability to identify optimal beam directions through signal quality measurement.
3Loss of information
If beam indices are explicitly encoded and transmitted, then complete beam information is provided, but the number of encoding and decoding operations increases
Solution Approach 1:
The patent uses the reference signal sequence itself as a copy or representation of the beam identification information. Instead of encoding beam indices as separate data and transmitting them, the beam identity is embedded in the sequence selection, allowing the UE to extract beam information directly from the detected sequence without additional decoding operations.
Data Source
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AI summary
A method for wireless communications is provided. The method includes transmitting a first signal during a first time interval. The first signal is encoded with a first spreading sequence generated by permutating a root sequence based on a permutation parameter associated with a first index. The method further includes transmitting a second signal during a second time interval. The second signal is encoded with a second spreading sequence generated by permutating the root sequence based on a permutation parameter associated with a second index. The method further includes receiving an indication of either the first index or the second index from a user equipment (UE).