DMRS Transmission for MTC Devices in Narrowband Uplink
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Solution Overview
Problem
Current methods do not allow machine-type communication (MTC) devices to transmit demodulation reference signals (DMRS) correctly for uplink data using only one or less of a physical resource block (PRB), limiting their ability to efficiently communicate with base stations, especially in scenarios requiring reduced bandwidth and low traffic.
Innovation Solution
A method where the DMRS sequence is mapped to 12 subcarriers of a PRB, which is then divided into N sub-PRBs, allowing transmission on N subframes, with the option to maintain the same frequency location or use different locations, and the uplink data is similarly mapped and transmitted, enabling effective communication even with reduced resource allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If MTC devices transmit uplink data using only one PRB or less, then bandwidth usage is reduced and manufacturing cost is lowered, but there is no method to correctly transmit DMRS for demodulation in such reduced bandwidth scenarios
Solution Approach 1:
The PRB is divided into multiple sub-PRBs, and the DMRS sequence is mapped to specific subcarriers within these sub-PRBs. This segmentation allows the reference signal to be properly distributed across the reduced bandwidth resources, enabling correct demodulation even when using only one PRB or less.
Solution Approach 2:
The invention extends DMRS transmission across multiple subframes while maintaining the reduced PRB allocation. By utilizing the time dimension (multiple subframes) in addition to the frequency dimension (sub-PRBs), the system achieves reliable demodulation capability without requiring increased bandwidth.
2Device complexity
If MTC devices use reduced bandwidth (one PRB or less), then device complexity and manufacturing cost are reduced, but communication capability with base stations is limited
Solution Approach 1:
By segmenting the PRB into sub-PRBs and strategically mapping DMRS sequences to specific subcarriers within these segments, the invention maintains effective communication capability while using reduced bandwidth resources, thus lowering device complexity without sacrificing adaptability.
Solution Approach 2:
The DMRS sequence is transmitted periodically across multiple subframes within the reduced PRB allocation. This periodic transmission ensures that the base station can reliably demodulate uplink data even with limited bandwidth, maintaining communication capability while keeping device complexity low.
3Measurement precision
If DMRS is mapped to all 12 subcarriers of a PRB, then demodulation accuracy is improved, but resource consumption increases when transmitting on multiple subframes
Solution Approach 1:
Instead of mapping DMRS to all 12 subcarriers in every subframe, the invention extracts and maps the DMRS sequence only to specific subcarriers within divided sub-PRBs. This selective mapping maintains sufficient demodulation accuracy while significantly reducing resource consumption across multiple subframes.
Solution Approach 2:
The invention applies partial action by mapping DMRS to only a subset of subcarriers (12/N subcarriers per sub-PRB) rather than all subcarriers. This partial mapping is sufficient for accurate demodulation while consuming fewer resources, especially when transmitting across multiple subframes.
Data Source
AI summary
The present specification discloses a method for transmitting a demodulation reference signal (DMRS) for uplink data demodulation by a machine type communication (MTC) device which is configured to operate in only a part of the system band of a cell. The method may comprise the steps of: mapping a DMRS sequence to 12 sub-carriers of a physical resource block (PRB); and dividing the PRB, to which the DMRS is mapped, into N sub-PRBs. Here, each of the sub-PRBs may comprise 12/N sub-carriers to which the DMRS is mapped. The method may further comprise a step for transmitting the N sub-PRBs to a base station in N sub-frames.