NB-PDCCH Design Using REG-to-RE Mapping for Narrowband IoT
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Solution Overview
Problem
There is a lack of clear design for control channels in NB-IoT downlink and uplink channels, particularly given the constraints of limited bandwidth and the need for efficient multiplexing across different operation modes.
Innovation Solution
The proposed solution involves designing the NB-PDCCH channel based on PDCCH rather than ePDCCH, with REG-to-RE mapping extending to all available OFDM symbols in each PRB, allowing for efficient multiplexing and time-discontinuous search spaces to minimize blocking probability and support different UE requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If control channel design is based on ePDCCH, then resource flexibility is improved, but implementation complexity increases due to DMRS requirements
Solution Approach 1:
The patent extracts and removes the DMRS requirement from the control channel design, opting for PDCCH-based design that uses existing reference signals. This eliminates the complexity introduced by DMRS while maintaining resource flexibility through REG-to-RE mapping extensions.
2Quantity of substance
If REG-to-RE mapping extends to all available OFDM symbols, then control channel capacity is improved, but blocking probability increases
Solution Approach 1:
The patent segments the control channel resources into different search spaces with different aggregation levels. This segmentation allows UEs to find control information in less congested segments, reducing blocking probability while maintaining overall capacity through the extended REG-to-RE mapping.
3Reliability
If control channel uses continuous time aggregation, then coverage is improved, but time resource efficiency deteriorates
Solution Approach 1:
The patent introduces dynamic search space configurations that can be adapted based on UE requirements and channel conditions. This allows the system to switch between continuous and discontinuous time aggregation patterns, optimizing both coverage and time resource efficiency for different scenarios.
4Reliability
If NB-IoT supports multiple DL Tx antenna ports, then signal reliability is improved, but system complexity increases
Solution Approach 1:
The patent designs the control channel to be universal across different antenna port configurations. The REG-to-RE mapping and search space structures work consistently whether 1 or 2 antenna ports are used, with SFBC automatically applied for 2-port operation. This maintains signal reliability through diversity while avoiding complexity through standardized procedures.
Data Source
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AI summary
REGs are mapped to REs for UEs to all available OFDM symbols for a subframe, which includes a time-frequency resource space comprising the OFDM symbols in time and subcarriers in frequency. The mapping is performed to form a portion of a control channel and the available symbols are OFDM symbols not used for another control channel. The REs are populated in the portion of the control channel with control information for the UEs using corresponding ones of the REGs. The mapping and the populating are performed to form a complete control channel over one or more subframes, wherein the complete control channel can span a single subframe or multiple subframes. The one or more subframes with the complete control channel are transmitted. A UE will blind decode received subframe (s) in order to determine the control information, which is to be subsequently used by the UE to receive or transmit data.