NB-IoT DwPTS Resource Mapping for TDD Coverage
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Solution Overview
Problem
Current methods for Machine Type Communication (MTC) and Internet of Things (IoT) in LTE systems face challenges in efficiently repeating downlink or uplink channels on limited Resource Elements (REs) in TDD special subframes, leading to difficulties in expanding cell coverage and maintaining low-cost communication.
Innovation Solution
The proposed solution involves methods for RE mapping, repetition, and scheduling in slot units using the DwPTS region of a special subframe, allowing for efficient data transmission and coherent combining of downlink physical channels in NB-IoT devices operating under TDD schemes, by determining conditions for using DwPTS as a slot and configuring NRS positions and interleaving patterns to maximize resource utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If downlink or uplink channels are repeated on TDD special subframes, then cell coverage is expanded, but the number of available Resource Elements is insufficient for effective repetition
Solution Approach 1:
The patent segments the TDD special subframe into distinct functional regions (DwPTS, GP, UpPTS) and further divides the DwPTS region into multiple slots. This segmentation allows selective use of specific resource elements within the special subframe for channel repetition, maximizing the utilization of limited available REs while maintaining proper TDD frame structure and timing relationships.
Solution Approach 2:
The patent introduces slot-level granularity within the DwPTS region, creating an additional dimension of resource organization beyond the traditional subframe level. By defining slot structures with specific start and end symbols within DwPTS, the system can perform channel repetition across multiple slots, effectively increasing the number of available resource elements for repetition without extending the overall subframe duration.
2Ease of manufacture
If bandwidth for MTC is reduced to be smaller than system bandwidth, then communication cost is reduced, but cell coverage expansion becomes more difficult
Solution Approach 1:
The patent merges multiple resource elements across different slots within the DwPTS region to form a combined resource pool for channel repetition. By combining resources from multiple time slots and performing coherent combining at the receiver, the system achieves enhanced coverage for narrowband MTC devices without requiring increased bandwidth, thus maintaining low communication costs while improving reliability.
Solution Approach 2:
The patent enables continuous channel repetition across multiple slots within the special subframe structure, ensuring uninterrupted transmission of downlink or uplink channels. This continuous transmission approach allows narrowband devices to accumulate signal energy over time through coherent combining, effectively extending cell coverage while maintaining the reduced bandwidth configuration for cost-effective MTC communication.
Data Source
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AI summary
One disclosure of the present specification provides a method for receiving a downlink physical channel by a narrowband Internet of things (NB-IoT) device. The method may comprise the steps of: determining whether to receive a signal of a downlink physical channel from an NB-IoT cell, on a downlink pilot time slot (DwPTS) of a time division duplex (TDD) special subframe; and receiving the signal of the downlink physical channel on the TDD special subframe including the DwPTS, on the basis of the determination.