Narrowband IoT Random Access Preamble Configuration for TDD
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Solution Overview
Problem
The existing Narrowband-IoT (NB-IoT) systems face challenges in supporting time division duplexing (TDD) configurations, particularly in configuring and transmitting random access preambles effectively, due to the lack of suitable uplink/downlink configurations that allow continuous transmission of symbol groups in TDD mode.
Innovation Solution
A method is proposed to configure the NPRACH preamble by defining new formats that utilize the existing LTE system's uplink/downlink configuration, allowing for contiguous transmission of symbol groups in uplink subframes, with adjustable cyclic prefix lengths and subcarrier spacings to optimize cell coverage and preamble reception performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing NB-IoT random access preamble formats are used in TDD systems, then device compatibility is maintained, but continuous transmission of symbol groups cannot be achieved due to uplink/downlink configuration constraints
Solution Approach 1:
The patent introduces dynamic preamble formats that can adapt to different TDD uplink/downlink configurations. The preamble structure becomes flexible with variable numbers of symbol groups and configurable cyclic prefix lengths, allowing the system to dynamically match the available uplink resources in different TDD scenarios while ensuring continuous transmission capability.
Solution Approach 2:
The patent changes key parameters of the random access preamble including the number of symbol groups (1-4 groups), cyclic prefix lengths (normal and extended), and subcarrier spacings (3.75 kHz and 15 kHz). These parameter variations enable the preamble to accommodate different TDD configurations and achieve continuous transmission across varying uplink resource patterns.
2Reliability
If new random access preamble formats with adjustable parameters are introduced, then cell coverage and transmission performance are improved, but system complexity increases
Solution Approach 1:
The patent segments the random access preamble into multiple symbol groups (1-4 groups) that can be independently configured and transmitted. Each symbol group contains a sequence of identical symbols with configurable cyclic prefixes. This segmentation allows flexible adaptation to different TDD configurations while maintaining a modular structure that simplifies implementation despite the increased parameter options.
3Reliability
If frequency hopping is implemented in NPRACH transmission, then robustness against fading and interference is improved, but timing synchronization requirements become more stringent
Solution Approach 1:
The patent ensures continuous transmission of symbol groups within the uplink subframe without interruptions, maintaining uninterrupted useful action during the random access preamble transmission. This continuity, combined with frequency hopping across different symbol groups, provides frequency diversity while allowing the base station to accurately estimate timing advance based on the continuous signal structure.
Data Source
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AI summary
Provided are a method for transmitting a random access preamble in a narrowband-IoT system supporting time division duplexing and an apparatus therefor. Specifically, a method for transmitting a narrowband physical random access channel (NPRACH) preamble by a user equipment in a narrowband-Internet of things (NB-IoT) system supporting time division duplexing may include: receiving, from a base station, configuration information related to an uplink-downlink configuration; and transmitting, to the base station, the NPRACH preamble configured by considering the uplink-downlink configuration.