NB-IoT Synchronization Signal Reception for TDD LTE Compatibility
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Solution Overview
Problem
In TDD NB-IoT technology, the downlink resources required for synchronization signals are poorly compatible with those in the TDD LTE system, making it challenging to send synchronization signals at a fixed period, which is essential for compatibility and efficient communication.
Innovation Solution
A method where a terminal device receives narrowband primary and secondary synchronization signals on one carrier and a narrowband physical broadcast channel and system information block on another carrier, with specific subframe allocations, allowing for downlink synchronization and system information acquisition, and using a Hadamard sequence set to indicate frequency spacing between carriers, enabling compatibility with both TDD and FDD NB-IoT systems using a single receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If synchronization signals are sent using a fixed period in TDD NB-IoT, then compatibility with TDD LTE system is improved, but the downlink resource compatibility deteriorates due to poor alignment with TDD LTE radio frame structure
Solution Approach 1:
The patent changes the time domain parameters of synchronization signal transmission by introducing flexible subframe offset configurations (k0, k1, k2 offsets) and periodicity options (10ms, 20ms, 40ms, 80ms). This allows the NB-IoT synchronization signals to be transmitted at fixed periods that are compatible with TDD LTE radio frame structures, resolving the resource alignment issue while maintaining fixed periodic transmission benefits
2Measurement precision
If separate receivers are used for TDD and FDD NB-IoT synchronization signals, then signal reception accuracy is improved, but terminal device cost increases
Solution Approach 1:
The patent designs a universal synchronization signal reception method where a single receiver can handle both TDD and FDD NB-IoT signals. The terminal device uses the same reception procedure for both duplex modes, with the network device indicating the duplex mode through SIB1-NB parameters. This multi-functional approach allows one receiver to serve multiple purposes, reducing terminal device cost while maintaining signal reception accuracy through mode-specific parameter configuration
3Loss of information
If synchronization signals use different time intervals from FDD NB-IoT, then TDD cell identification is enabled, but receiver compatibility becomes more complex
Solution Approach 1:
The patent uses time interval differences as a distinctive characteristic (analogous to color changes) to differentiate TDD from FDD NB-IoT cells. TDD cells use specific time intervals between NPSS and NSSS that differ from FDD configurations. The terminal device, equipped with a universal receiver, can identify the cell type by detecting these time interval patterns and automatically adjust reception parameters accordingly, enabling cell identification without increasing receiver hardware complexity
Data Source
AI summary
This application provides a signal sending method, a signal receiving method, and an apparatus. The method includes: receiving, by a terminal device on a first carrier, a narrowband primary synchronization signal (NPSS) sent by a network device according to a first period and a narrowband secondary synchronization signal (NSSS) sent by the network device according to a second period; receiving, by the terminal device on a second carrier, a narrowband physical broadcast channel (NPBCH) sent by the network device according to a third period and a system information block 1-narrowband (SIB1-NB) sent by the network device according to a fourth period; and completing, by the terminal device, downlink synchronization and obtaining system information based on the NPSS, the NSSS, the NPBCH, and the SIB1-NB.