Control Channel Padding and Scrambling for Fewer False CRC Passes

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Solution Overview

Problem

In cellular networks, especially those using Orthogonal Frequency Division Multiple Access (OFDMA), existing control channel signaling methods face challenges in minimizing overhead while ensuring accurate and efficient decoding by user equipment (UE), particularly in differentiating between control channels and reducing false CRC passes due to shared resources and varying transmission parameters.

Innovation Solution

The proposed solution involves a transmitter and receiver system that includes input padding, scrambling, forward error correction encoding, and rate matching to generate and process control channel bits, using unique masking sequences based on UE identification numbers to ensure correct decoding and reduce computational burden by limiting candidate control channels and false CRC passes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If control channels are shared among multiple users with different transmission parameters, then resource utilization is improved, but decoding accuracy deteriorates due to increased difficulty in differentiating control channels

Engineering Contradiction:

Improveresource utilizationVSAvoiddecoding accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent segments the control channel by inserting unique padding bits for each user equipment (UE) before channel encoding. This segmentation allows each UE to identify its specific control channel through the unique padding pattern, thereby maintaining decoding accuracy even when multiple users share the same control channel resources.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediary mechanism (unique padding bits derived from UE identification) that mediates between the shared control channel resources and the individual UE decoding requirements. This intermediary allows UEs to differentiate their control channels without requiring dedicated control channel resources for each user.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If overhead is minimized in control signaling, then transmission efficiency is improved, but reliability deteriorates due to reduced error detection and differentiation capability

Engineering Contradiction:

Improvetransmission efficiencyVSAvoiderror detection capability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies partial action by inserting only a limited number of padding bits (exactly the number needed for UE identification, typically 16 bits) rather than extensive redundancy. This provides sufficient error detection and channel differentiation capability while minimizing the overhead added to the control signal.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The patent changes the parameter of padding bit insertion by making the padding bits dynamic and UE-specific rather than static and universal. The padding bits are generated based on UE identification parameters, allowing the system to maintain reliability through unique patterns while controlling overhead through parameter optimization.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If unique padding bits are inserted for each UE before encoding, then decoding accuracy is improved by enabling UE identification, but overhead increases due to additional bits

Engineering Contradiction:

Improvedecoding accuracyVSAvoidcontrol channel overhead

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent uses exactly the minimum number of padding bits required for UE identification (typically 16 bits matching the CRC length) rather than inserting excessive redundancy. This provides sufficient decoding accuracy and UE differentiation while minimizing the overhead added to each control channel transmission.

Inventive Principle:

Principle #16Partial or excessive action

4Reliability

If multiple decoding attempts are performed by UE to find assigned control channel, then probability of correct decoding is improved, but computational burden increases

Engineering Contradiction:

Improvedecoding success probabilityVSAvoidcomputational burden

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent performs preliminary action by inserting unique padding bits into the control channel before encoding and transmission. This preliminary differentiation allows UEs to quickly identify their assigned control channel through simple pattern matching on the padding bits, significantly reducing the number of full decoding attempts required and thereby reducing computational burden.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS8683305B2Rate matching and scrambling techniques for control signaling

Publication Date: 2014.03.25 TEXAS INSTRUMENTS INC

AI summary

Embodiments of the present disclosure provide a transmitter, a receiver and methods of operating a transmitter and a receiver. In one embodiment, the transmitter includes an input padding module configured to provide padded bits having padding bits added to payload bits for one or more control channels, and a scrambling module configured to apply a masking sequence to one or more of the padded bits to generate scrambled bits. Additionally, the transmitter also includes an encoding module configured to perform forward error correction encoding and rate matching on the scrambled bits to obtain a required number of control channel output bits, and a transmit module configured to transmit the control channel output bits for one or more control channels.