NPRACH Preamble Symbol Group Segmentation for TDD NB-IoT
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Solution Overview
Problem
The existing narrowband IoT systems face challenges in efficiently transmitting random access preambles in time division duplexing (TDD) configurations, particularly due to limitations in uplink-downlink configuration and symbol group settings, which affect the performance and coverage of NB-IoT systems.
Innovation Solution
A method for configuring and transmitting a narrowband physical random access channel (NPRACH) preamble in NB-IoT systems supporting TDD, involving the use of two symbol group sets with three contiguous symbol groups each, where the length of each symbol group is configured to be shorter than a transmission time unit, and frequency hopping is applied with specific hopping patterns to optimize coverage and reduce latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the NPRACH preamble uses traditional symbol group lengths equal to transmission time units, then the system maintains compatibility with existing TDD configurations, but the coverage area is limited and timing advance estimation is slow
Solution Approach 1:
The patent divides the traditional symbol group into multiple smaller symbol groups. Specifically, instead of using one symbol group per transmission time unit, the patent uses multiple symbol groups (e.g., 2-8 symbol groups) within the same transmission time unit, with each symbol group having a shorter duration. This segmentation allows for faster timing advance estimation while maintaining overall transmission structure compatibility.
Solution Approach 2:
The patent performs preliminary timing advance estimation by using multiple shorter symbol groups before the complete preamble transmission is finalized. The base station can estimate timing advance earlier in the transmission process using the first few symbol groups, rather than waiting for the entire traditional symbol group to complete.
2Speed
If the system uses shorter symbol group lengths, then the timing advance estimation speed improves, but the device complexity increases due to multiple symbol group sets and frequency hopping configurations
Solution Approach 1:
The patent changes key parameters of the preamble structure: reducing symbol group length, increasing the number of symbol groups per transmission time unit, and introducing frequency hopping between symbol groups. These parameter changes enable faster timing estimation while the systematic approach to configuration manages the complexity.
Solution Approach 2:
The patent introduces periodic frequency hopping patterns where symbol groups hop between different frequencies in a predetermined sequence. This periodic action provides structure to the increased complexity, making the system manageable through regular patterns rather than arbitrary configurations.
3Length of moving object
If multiple symbol groups are transmitted within one transmission time unit, then the coverage area can be reduced for shorter range applications, but the uplink-downlink configuration flexibility is constrained
Solution Approach 1:
The patent makes the preamble structure dynamic by allowing the number of symbol groups per transmission time unit to be configured based on coverage requirements. For normal coverage, fewer symbol groups are used, while for extended coverage or shorter range applications, more symbol groups are transmitted within the same time unit, enabling adaptive coverage adjustment.
Solution Approach 2:
The patent creates a universal preamble structure that can serve multiple functions: it works for both traditional single symbol group transmissions and the new multiple symbol group transmissions. The same basic framework accommodates different numbers of symbol groups, different frequency hopping patterns, and different coverage scenarios, making the system versatile.
Data Source
AI summary
A method for transmitting a random access preamble in a narrowband-IoT system supporting time division duplexing and an apparatus therefor. In some implementations, 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.