Uplink Subcarrier Spacing Indication for NB-IoT
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Solution Overview
Problem
In Narrowband Internet of Things (NB-IoT) communication, the inconsistency between the uplink subcarrier spacing used by user equipment (UE) and the subcarrier spacing supported by the base station leads to incorrect demodulation of uplink signals, as NB-IoT systems define two types of subcarrier spacings, whereas LTE/LTE-A systems only support one.
Innovation Solution
The base station and terminal indicate their respective supported uplink subcarrier spacings to each other, using methods such as classifying physical random access preamble sequences or PRACH signals into groups corresponding to specific subcarrier spacings, to ensure the terminal uses the appropriate subcarrier spacing for data transmission, allowing the base station to correctly demodulate the uplink signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If NB-IoT system supports multiple uplink subcarrier spacings (3.75 kHz and 15 kHz) for different transmission modes, then the adaptability and versatility of the system is improved, but the complexity of indicating and coordinating subcarrier spacing between base station and terminal increases
Solution Approach 1:
The patent segments the random access preamble sequences into multiple groups, where each group corresponds to a specific uplink subcarrier spacing (3.75 kHz or 15 kHz). The base station indicates the appropriate group to the terminal, enabling the terminal to select preambles from the indicated group. This segmentation approach allows the system to support multiple subcarrier spacings while simplifying the indication mechanism by using group identifiers rather than direct subcarrier spacing parameters.
Solution Approach 2:
The patent introduces an intermediary mechanism where the base station sends indication information (group identifier) to the terminal, which then uses this indication to select from the segmented preamble groups. This intermediary indication approach resolves the complexity by providing a simplified signaling method that bridges the base station's subcarrier spacing configuration and the terminal's preamble selection, avoiding direct complex subcarrier spacing negotiation.
2Device complexity
If the base station and terminal do not indicate their supported uplink subcarrier spacings to each other, then the communication protocol simplicity is improved, but the reliability of uplink signal demodulation deteriorates
Solution Approach 1:
The patent implements preliminary action by having the base station pre-configure and indicate the appropriate random access preamble group to the terminal before the actual random access procedure. This advance indication ensures that both the base station and terminal are aligned on the subcarrier spacing to be used, eliminating the need for complex real-time negotiation while guaranteeing reliable demodulation. The terminal uses the indicated group information to select preambles that match the base station's expected subcarrier spacing.
Solution Approach 2:
The patent establishes a feedback mechanism where the terminal's selection of random access preamble from the indicated group provides implicit feedback to the base station about the terminal's capability and the agreed-upon subcarrier spacing. This feedback loop ensures both parties are synchronized on the subcarrier spacing configuration, maintaining reliability while keeping the protocol simple through implicit rather than explicit continuous negotiation.
Data Source
AI summary
Embodiments of the present invention provide an uplink subcarrier spacing indication method, a base station, and a terminal. The base station determines indication information that is used to indicate a first uplink subcarrier spacing supported by the base station, and communicates with the terminal according to the indication information. During the communication, the base station indicates the first uplink subcarrier spacing supported by the base station to the terminal, so that the terminal subsequently determines, based on the first uplink subcarrier spacing, a second uplink subcarrier spacing supported by the terminal; or the base station receives information that is sent by the terminal and that carries a second uplink subcarrier spacing, in other words, receives an indication from the terminal, so as to learn of the second uplink subcarrier spacing supported by the terminal or to be used by the terminal to send an uplink signal.