NB-IoT Uplink Framing for LTE SRS Interference Avoidance
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Solution Overview
Problem
The legacy LTE system is not optimized for low-cost IoT communication, requiring bandwidth reduction, which necessitates a new frame structure design and consideration of interference with neighboring LTE terminals.
Innovation Solution
A method for transmitting uplink channels using a narrowband-internet of things (NB-IoT) device, determining a subcarrier spacing of 3.75 kHz and a subframe length of 2 ms, excluding the last portion of the subframe when it overlaps with a sounding reference signal (SRS) transmission by adjacent LTE-based UEs, and incorporating a processor to control the transmission and reception unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bandwidth of IoT communication is reduced for cost reduction, then communication cost is reduced, but a new frame structure design is required and interference problems with neighboring legacy LTE terminals arise
Solution Approach 1:
The patent changes the subcarrier spacing parameter from the legacy LTE value to 3.75 kHz for NB-IoT, which enables more efficient bandwidth utilization. This parameter change allows the system to achieve lower cost communication while maintaining compatibility with existing LTE infrastructure, resolving the contradiction between cost reduction and system complexity.
Solution Approach 2:
The patent segments the subframe structure by excluding the last portion from uplink channel transmission when it overlaps with SRS resources. This segmentation approach allows NB-IoT devices to coexist with legacy LTE terminals by avoiding interference with SRS transmissions, thereby reducing interference problems while maintaining the reduced bandwidth structure.
2Reliability
If the bandwidth of IoT communication is reduced for cost reduction, then communication cost is reduced, but interference problems with neighboring legacy LTE terminals arise
Solution Approach 1:
The patent extracts or removes the last portion of the subframe from uplink channel transmission when it would overlap with SRS resources. This extraction eliminates the source of interference with legacy LTE terminals while preserving the reduced bandwidth structure for cost-effective IoT communication.
Solution Approach 2:
The patent applies preliminary anti-action by proactively excluding the last portion of the subframe from uplink transmission before interference can occur. This preventive measure ensures that NB-IoT devices do not interfere with SRS transmissions from legacy LTE terminals, resolving the interference problem before it arises.
3Reliability
If a new frame structure is designed for reduced bandwidth, then cost is reduced, but the structure must accommodate SRS transmission by adjacent LTE UEs
Solution Approach 1:
The patent creates a universal frame structure that serves multiple functions: it enables cost-reduced NB-IoT communication while simultaneously accommodating SRS transmissions from legacy LTE terminals. By making the last portion of the subframe available for SRS transmission, the structure achieves multi-functionality and ensures coexistence between NB-IoT and LTE systems.
Data Source
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AI summary
The disclosure of the present specification provides a method in which a narrowband-Internet of things (NB-IoT) device transmits an uplink channel. The method comprises: determining an uplink subcarrier spacing for transmitting an uplink channel; determining the length of a subframe on the basis of the subcarrier spacing; and transmitting the uplink channel in a subframe having the determined length. The last part of the subframe may be excluded from the transmission of the uplink channel.