NB-IoT Terminal Subcarrier Allocation via DCI Offset
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing LTE systems face challenges in allocating resources to Narrow Band Internet of Things (NB-IoT) terminals, as they require allocation in smaller frequency units than the standard resource allocation unit, posing difficulties in managing bandwidth and reducing frequency diversity effects.
Innovation Solution
NB-IoT terminals determine resource allocation based on received resource information and identification, using higher layer signaling to select subcarriers for communication, reducing the need for explicit subcarrier allocation by the radio base station and minimizing overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If resource allocation is performed in PRB unit as in existing LTE system, then device complexity is reduced and ease of operation is improved, but NB-IoT terminals cannot allocate resources in smaller frequency units than PRB, limiting bandwidth management flexibility
Solution Approach 1:
The patent segments the PRB (Physical Resource Block) into smaller subcarriers for allocation. Instead of allocating resources only in PRB units, the system divides each PRB into multiple subcarriers and allocates them individually to NB-IoT terminals. This segmentation enables finer granularity resource allocation in the frequency domain, allowing NB-IoT terminals to use smaller frequency units than the standard PRB allocation, thus improving bandwidth management flexibility without significantly increasing system complexity
Solution Approach 2:
The patent introduces a new dimension of resource allocation by adding subcarrier-level allocation on top of the existing PRB-based time-frequency resource grid. This creates an additional layer of granularity in the frequency dimension, allowing terminals to allocate resources at subcarrier level while maintaining compatibility with the existing LTE resource allocation framework. This dimensional extension resolves the contradiction by enabling fine-grained allocation without requiring complete redesign of the resource management system
2Ease of manufacture
If NB-IoT terminals use narrower bandwidth (180 kHz, 1 PRB), then cost is reduced and coverage area is improved, but resource allocation in smaller units than PRB becomes problematic in existing LTE systems
Solution Approach 1:
The patent implements dynamic resource allocation where the allocation granularity can adapt between PRB level and subcarrier level based on terminal type and service requirements. For NB-IoT terminals with narrow bandwidth, the system dynamically switches to subcarrier-level allocation within the constrained 180 kHz bandwidth, while maintaining PRB-level allocation for other terminals. This dynamic adaptability allows narrowband terminals to achieve fine-grained resource control without requiring complex hardware, as the flexibility is provided through the allocation mechanism rather than terminal capability
3Measurement precision
If explicit subcarrier allocation is performed by radio base station, then resource allocation precision is improved, but overhead is increased
Solution Approach 1:
The patent applies partial explicit allocation by providing detailed subcarrier allocation information only when necessary for NB-IoT terminals, while using implicit or simplified allocation for other scenarios. The base station provides explicit subcarrier assignment in the downlink control information (DCI) format specifically for NB-IoT terminals that require fine-grained allocation, rather than implementing explicit allocation universally. This partial application of explicit allocation achieves the needed precision for narrowband terminals while minimizing the increase in control overhead across the entire system
Data Source
Figure 1
Figure 2
Figure 3
AI summary
In order to perform communications using a resource of a smaller frequency unit (for example, subcarrier unit) than the resource allocation unit in the existing LTE system, the present invention provides a user terminal including: a reception section that receives downlink control information; a transmission section that transmits an uplink shared channel based on the downlink control information; and a control section that determines a subcarrier used for transmission of the uplink shared channel, based on an offset value associated with a given field value in the downlink control information.