NB-IoT Cell Search Assist Information for LTE In-Band Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current communication methods between terminal apparatuses and base stations in NB-IoT and LTE systems face inefficiencies in cell search and initial access, particularly in scenarios where downlink NB-IoT is included in the transmission bandwidth of an LTE cell, leading to increased power consumption and reduced frequency efficiency.
Innovation Solution
The implementation of a communication method that utilizes assist information for cell search, including channel raster spacing and offset values, to enable efficient detection of NB-IoT cells within the LTE cell structure, allowing for optimized channel center frequency alignment and reduced interference between NB-IoT and LTE subcarriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If NB-IoT downlink is included in the transmission bandwidth of an LTE cell (in-band scenario), then frequency efficiency is improved, but cell search and initial access become more complex and power consumption increases
Solution Approach 1:
The base station transmits assist information (channel raster spacing and offset values) to the terminal apparatus before the terminal performs cell search. This preliminary provision of frequency location information enables the terminal to efficiently identify NB-IoT cell frequencies without exhaustive scanning, resolving the contradiction by preparing necessary data in advance that simplifies the subsequent cell search process while maintaining in-band frequency efficiency
2Adaptability or versatility
If NB-IoT downlink is included in the transmission bandwidth of an LTE cell (in-band scenario), then frequency efficiency is improved, but power consumption during cell search increases
Solution Approach 1:
The base station provides assist information containing channel raster spacing and offset values before the terminal apparatus performs cell search. This allows the terminal to directly calculate NB-IoT cell frequencies using the formula f_NB-IoT = f_LTE + offset, avoiding power-consuming exhaustive frequency scanning while maintaining efficient in-band frequency utilization
3Object-affected harmful factors
If dedicated NB-IoT reference signals are used for in-band operation, then interference between NB-IoT and LTE signals is reduced, but system complexity increases
Solution Approach 1:
Dedicated NB-IoT reference signals (NB-RS) are introduced specifically for NB-IoT in-band operation, while LTE cells continue to use their existing CRS. These NB-RS are configured with specific resource element positions and sequence generation parameters distinct from LTE signals, providing localized interference mitigation for NB-IoT without affecting LTE system operation, thus reducing signal interference while managing system complexity through targeted rather than universal changes
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A terminal apparatus and a base station apparatus can efficiently communicate with each other through downlink. A terminal apparatus detects a first physical layer cell identity (PCI) through cell search and receives system information, a first RS, and a second RS. The system information is used to indicate at least (i) a second PCI, (ii) a transmission bandwidth of EUTRA and an offset associated with a physical resource block index, and (iii) an operation of NB-IoT. A first sequence of the first RS is identified based at least on the first PCI. A second sequence of the second RS is identified based at least on the second PCI and the offset.