NR Channel and SSB Raster Alignment for Unlicensed Spectrum
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Solution Overview
Problem
The alignment of NR channel and synchronization signal rasters with LTE channel rasters in unlicensed spectrum is not trivial, leading to inefficiencies in transceiver design and increased latency in cell acquisition due to misalignment of subcarrier and PRB grids, which affects the coexistence and efficient operation of NR cells with LTE and Wi-Fi systems.
Innovation Solution
The proposed solution involves selecting specific NR channel and synchronization signal block (SSB) raster entries that align with LTE channel raster positions, ensuring subcarrier and PRB grid alignment, allowing for efficient transceiver design and reduced latency in cell acquisition by using formulas to calculate optimal NR-ARFCN and GSCN values, and down-selecting entries that meet criteria for PRB and guard band alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If NR channel raster frequencies are selected to align with LTE channel raster positions, then transceiver implementation is simplified and power consumption is reduced, but the granularity of the raster cannot be modified which affects subcarrier and PRB grid alignment
Solution Approach 1:
The patent applies parameter changes by defining specific NR channel raster frequencies based on LTE channel raster positions. The formula F_NR = F_LTE + offset establishes a relationship between LTE and NR raster frequencies, allowing NR to align with LTE while maintaining its own frequency grid. This resolves the contradiction by fixing the raster granularity to enable alignment benefits without allowing modification that would break subcarrier and PRB grid alignment.
2Adaptability or versatility
If channel raster and SSB raster are aligned with LTE positions, then coexistence with LTE and Wi-Fi systems is enabled, but initial access acquisition latency increases due to restricted frequency options
Solution Approach 1:
The patent segments the frequency spectrum by defining discrete NR channel raster positions that are subsets of LTE channel raster positions. This segmentation creates a finite set of aligned frequencies where NR can operate while maintaining coexistence with LTE and Wi-Fi. The segmentation approach resolves the contradiction by limiting frequency options to aligned positions, which reduces acquisition latency through fewer search possibilities while enabling systematic coexistence.
3Productivity
If NR operates in unlicensed spectrum with aligned rasters, then spectrum usage efficiency improves, but device complexity increases due to additional alignment calculations
Solution Approach 1:
The patent applies preliminary action by pre-defining the NR channel raster frequencies based on LTE channel raster positions before actual communication begins. The formulas establish the raster alignment relationship in advance, so that during operation, the device only needs to select from pre-calculated aligned frequencies rather than performing complex real-time alignment calculations. This resolves the contradiction by performing the complex calculation work beforehand, which simplifies runtime operations while maintaining high spectrum usage efficiency.
Data Source
AI summary
Systems and methods for determining channel raster(s) and synchronization signal raster(s) for New Radio (NR) unlicensed spectrum are disclosed herein. For each of a plurality of data objects an NR channel raster position is determined using Absolute Radio Frequency Channel Number (NR-ARFCN) numbers. For each corresponding NR channel, Global Synchronization Channel Numbers (GSCNs), a number of Physical Resource Blocks (PRBs) based on channel subcarrier spacing (SCS), NR channel raster position placement, channel edges, synchronization signal and physical broadcast channel (SSB) edges, and an SSB raster position are calculated. The plurality of data objects may then be down selected based on e.g., corresponding Long Term Evolution (LTE) channel raster positions and/or entries of a second plurality of data objects calculated for NR channels that use a second SCS.