PDCCH Encoding Circular Buffer Puncturing for Detection Errors

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Solution Overview

Problem

In LTE telecommunications systems, Physical Downlink Control Channel (PDCCH) detection errors occur due to ambiguity in aggregation levels caused by overlapping search spaces and repeated coded bits, leading to incorrect uplink ACK/NACK resource location and reduced downlink throughput.

Innovation Solution

The size of the circular buffer is modified by deleting or repeating coded bits to prevent repetition and ambiguity in PDCCH encoding, ensuring unambiguous encoding and transmission of PDCCH payloads.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If circular buffer based rate matching is used for PDCCH encoding, then the encoding process can be simplified and implemented efficiently, but coded bits repeat themselves causing ambiguity in aggregation level detection

Engineering Contradiction:

Improveencoding implementation simplicityVSAvoidPDCCH detection accuracy

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent extracts the problematic repeated coded bits from the circular buffer by introducing a puncturing mechanism. Specifically, certain coded bits are removed (punctured) from the buffer before transmission, breaking the repetition pattern that causes aggregation level ambiguity while maintaining the overall encoding structure.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the effective buffer size parameter by puncturing specific bits. This modifies the code rate and the pattern of transmitted bits, ensuring that identical PDCCH payloads at different aggregation levels produce distinguishable bit sequences, thereby resolving the detection ambiguity.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If search spaces for different aggregation levels overlap, then resource utilization is improved, but PDCCH detection errors occur due to ambiguity

Engineering Contradiction:

Improveresource utilization efficiencyVSAvoidPDCCH detection accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent introduces punctured bits as an intermediary mechanism that mediates between overlapping search spaces. The puncturing pattern acts as a distinguishing feature that allows the receiver to correctly identify the aggregation level even when search spaces overlap, eliminating detection errors while maintaining resource efficiency.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If multiple aggregation levels are monitored, then control channel coverage is improved, but false alarms increase due to ambiguous detection

Engineering Contradiction:

Improvecontrol channel coverageVSAvoiddetection accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent segments the coded bit sequence by puncturing specific bits at defined positions. This segmentation creates unique patterns for different aggregation levels, allowing the receiver to distinguish between them accurately. The punctured positions divide the original sequence into distinguishable segments that prevent false alarm conditions.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS8780930B2System and method for removing PDCCH detection errors in a telecommunications network

Publication Date: 2014.07.15 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A system, method and node for unambiguous encoding of Physical Downlink Control Channel (PDCCH) channels in a Long Term Evolution (LTE) telecommunications system to remove detection errors. The method includes modifying a size of a circular buffer where the coded bits are collected to avoid repetition of the coded bits in consecutive subset of the control channel elements allocated to the PDCCH. The size of the circular buffer is selected so that it is not equal to the number of coded bits output from the encoder. Coded bits can be deleted from or added to the coded bit sequence depending on the size of the circular buffer.