Wireless Device Frequency Adjustment for NB-IoT LTE Coexistence
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Solution Overview
Problem
Current solutions for deploying Narrowband Internet of Things (NB-IoT) systems alongside Long Term Evolution (LTE) systems are resource inefficient due to channel raster offsets, which constrain carrier positions and require either reduced power transmission or stringent channel filters to maintain orthogonality and avoid interference.
Innovation Solution
A method where a wireless device receives information about physical resource block (PRB) and channel raster offsets, allowing it to adjust frequency and determine the appropriate frequency resource for NB-IoT deployment, enabling efficient coexistence with LTE systems by deploying on higher and lower frequency resources relative to the LTE inner frequency resource.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If NB-IoT carrier is deployed in guard-band of LTE system to fulfill 100 kHz channel raster requirement, then orthogonality to LTE subcarriers is lost, but interference between NB-IoT and LTE systems increases
Solution Approach 1:
The patent introduces guard subcarriers as intermediary elements between the NB-IoT carrier and LTE subcarriers. These guard subcarriers act as a buffer zone that maintains the 100 kHz channel raster alignment for NB-IoT while preventing interference with LTE subcarriers, thus resolving the contradiction between channel raster alignment and interference avoidance
Solution Approach 2:
The patent changes the frequency domain parameters by introducing guard subcarriers that create a frequency offset structure. This allows the NB-IoT carrier to be positioned at 100 kHz raster points while the guard subcarriers absorb the frequency mismatch, enabling orthogonality to be maintained through parameter adjustment rather than direct alignment
2Reliability
If NB-IoT carrier is deployed with offset from 100 kHz channel raster, then orthogonality to LTE subcarriers is maintained, but channel raster requirements are not fulfilled
Solution Approach 1:
The patent segments the frequency resource into three distinct parts: LTE subcarriers, guard subcarriers, and NB-IoT carrier. This segmentation allows each component to operate with its own frequency characteristics - LTE subcarriers maintain their original spacing, guard subcarriers provide the necessary offset, and NB-IoT carrier achieves 100 kHz raster alignment, thus resolving the contradiction between orthogonality and channel raster requirements
3Productivity
If NB-IoT system is deployed in-band of LTE system, then frequency resources are efficiently utilized, but interference between systems occurs due to channel raster offsets
Solution Approach 1:
The patent introduces guard subcarriers as intermediary elements between the NB-IoT carrier and LTE subcarriers. These guard subcarriers act as a buffer zone that maintains the 100 kHz channel raster alignment for NB-IoT while preventing interference with LTE subcarriers, thus resolving the contradiction between channel raster alignment and interference avoidance
Solution Approach 2:
The patent merges the NB-IoT system and LTE system into a unified frequency domain structure where both systems coexist. By combining LTE subcarriers, guard subcarriers, and NB-IoT carrier into a single frequency resource allocation scheme, the system achieves efficient frequency utilization while maintaining orthogonality through the guard subcarrier mechanism
Data Source
AI summary
Embodiments herein relate for example to a method performed by a wireless device in a first wireless communication system that is deployed on a frequency resource. The wireless device receives information indicating a PRB offset and a corresponding channel raster offset. The channel raster offset is an offset in frequency between a channel raster, used by the wireless device (105) in a cell search process, and the frequency resource. The PRB offset indicates an offset between the frequency resource and an inner frequency resource on which a second wireless communication system is deployed. In the frequency domain, the second wireless communication system is deployed on at least one higher frequency resource above the inner frequency resource and at least one lower frequency resource below the inner frequency resource. The wireless device determines, based on the received information, an adjustment in frequency applicable for the frequency resource on which the first wireless communication system is deployed.