NB-IoT NPDCCH False Positive Detection via Code Rate Ratio
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Solution Overview
Problem
In NB-IoT systems, false positive detection in the downlink control channel leads to mismatched uplink and downlink scheduling, increasing retransmissions and power consumption, due to the high likelihood of erroneous CRC checks in low SNR conditions.
Innovation Solution
A method that calculates the effective and scheduled code rates of NPDCCH, NPDSCH, and NPUSCH, and compares them to pre-defined bounds to filter out false positive detections, thereby reducing unnecessary processing and resource allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If blind search method is used to monitor NPDCCH candidates, then the user equipment can detect downlink control information, but false positive detection occurs due to erroneous CRC checks in low SNR conditions
Solution Approach 1:
The patent changes the parameter used for false positive detection from CRC check result alone to a combination of CRC check result and code rate information. By introducing code rate as an additional parameter, the system can distinguish true detections from false positives more accurately in low SNR conditions.
Solution Approach 2:
The patent introduces code rate information as an intermediary element that mediates between the CRC check result and the final detection decision. The code rate acts as a filter that helps validate whether a CRC pass represents a true detection or a false positive.
2Productivity
If false positive detection occurs, then unnecessary resource allocation and processing happen, but power consumption increases
Solution Approach 1:
The patent performs preliminary verification using code rate information before committing to full resource allocation and processing. By checking code rate consistency early in the detection process, the system可以避免 unnecessary resource allocation and reduce power consumption associated with processing false positives.
Solution Approach 2:
The patent extracts and utilizes code rate information as a separate verification criterion independent of the CRC check. This extracted parameter serves as an additional filter to eliminate false positives before they consume valuable resources and power.
3Reliability
If code rate is reduced to improve transmission reliability, then more channel bits are transmitted, but false positive detection likelihood increases
Solution Approach 1:
The patent changes the detection approach by incorporating code rate information into the verification process. Even when low code rates are used for reliable transmission, the system can distinguish true detections from false positives by checking whether the detected code rate matches expected values, thus maintaining detection accuracy despite low SNR conditions.
Data Source
AI summary
The application relates to a method for reducing false positive detection in NB-IoT downlink control channel. The method comprises the following steps: synchronizing a UE to an eNB and exchanging a data transmission via a NPDSCH or a NPUSCH, whereas DCI pertaining to downlink or uplink data transmission is signaled to UE by eNB via NPDCCH, wherein calculating an effective code rate of NPDCCH that is used in receiving downlink grant, resulting in a value CRNPDCCH, calculating a scheduled code rate of NPDSCH or NPUSCH, resulting in a value CRNPDSCH or CRNPUSCH, calculating a ratio between the effective code rate CRNPDCCH and the scheduled code rate CRNPDSCH or CRNPUSCH, resulting in a result x, comparing the result x with pre-defined upper and lower bounds, dropping and not processing further the result x as false positive detection if the result x violates the pre-defined bounds.