N-EPDCCH Sub-band Operation for MTC Devices
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Solution Overview
Problem
Legacy downlink control channels cannot be operated in reduced bandwidth, posing a challenge for machine-type communication (MTC) devices that require cost-effective communication solutions with limited system bandwidth.
Innovation Solution
A new downlink control channel, referred to as N-EPDCCH or M-EPDCCH, is introduced, allowing MTC devices to operate within a sub-band, using either CRS-based or DMRS-based channel estimation, and employing SFBC techniques for transmission, to facilitate efficient communication without requiring the entire system band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If MTC devices use reduced bandwidth to reduce cost, then device cost is reduced, but legacy downlink control channels cannot be operated
Solution Approach 1:
The system bandwidth is segmented into multiple sub-bands, and the downlink control channel is configured to operate within a specific sub-band rather than the entire system bandwidth. This allows MTC devices to use reduced bandwidth (one sub-band) while still receiving control channel transmissions, resolving the contradiction between cost reduction and control channel operation capability
Solution Approach 2:
The downlink control channel is configured with localized resource allocation within a specific sub-band, allowing different frequency resources to serve different purposes. MTC devices can be allocated control channel resources in a specific sub-band while other sub-bands remain available for data transmission or other devices, enabling cost-effective operation without sacrificing control channel functionality
2Device complexity
If MTC devices operate in reduced bandwidth, then device complexity is reduced, but control channel compatibility is lost
Solution Approach 1:
The downlink control channel configuration is made dynamic and flexible, allowing the network to configure control channel resources adaptively based on device capabilities and service requirements. MTC devices can be configured with appropriate sub-band allocations and control channel parameters, enabling them to operate in reduced bandwidth while maintaining compatibility through flexible resource allocation rather than fixed legacy structures
3Reliability
If legacy PDCCH is used in full bandwidth, then control channel coverage is maintained, but MTC devices cannot operate cost-effectively
Solution Approach 1:
The control channel coverage is maintained by segmenting the system bandwidth into sub-bands and configuring the downlink control channel to transmit within specific sub-bands. This allows MTC devices to receive control channel transmissions in their allocated sub-band without requiring full system bandwidth, maintaining coverage while enabling cost-effective operation
Solution Approach 2:
The control channel transmission is moved from the traditional time-domain focused approach to include frequency-domain segmentation. By configuring control channels in specific sub-bands rather than spanning the entire frequency spectrum, the system creates a new dimensional approach to control channel allocation that enables both full coverage and reduced device bandwidth requirements
Data Source
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AI summary
Provided is a method for receiving a downlink control channel in a machine type communication (MTC) device configured to operate only in a part of a band among system bands of a cell. A method for receiving a downlink control channel can comprise the steps of: determining a precoding matrix index (PMI) applied to a downlink control channel receivable only in a part of a band; receiving from a cell the downlink control channel in the part of the band in a data area of a subframe; and decoding the downlink control channel, which has been received from the cell, on the basis of the determined PMI.