Transport Link Control for Packet Loss Detection in 5G CU-DU Interfaces

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Solution Overview

Problem

In 5G cellular systems, packets can be lost on the CU-DU interface without detection, leading to unreliability in the transport network, as existing protocols do not effectively identify and retransmit lost packets.

Innovation Solution

Establishing a transport network communication link between infrastructure cellular entities with transport link control functions that allocate sequence numbers to data packets, detect packet loss, and transmit status reports to a central controller, enabling retransmissions and congestion management.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If traditional protocol layers are split between CU and DU, then base station functionality is distributed and scalability is improved, but packet loss detection capability deteriorates because lost packets cannot be identified over the transport network

Engineering Contradiction:

Improvebase station scalabilityVSAvoidpacket loss detection

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The transport link control function is segmented into separate transmitting and receiving entities, with the transmitting entity assigning sequence numbers to packets and the receiving entity detecting losses based on these numbers. This segmentation enables reliable packet loss detection while maintaining the distributed CU-DU architecture.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The receiving transport link control entity provides feedback about detected packet losses to the transmitting entity using status reports. This feedback mechanism enables the transmitting side to identify and retransmit lost packets, improving reliability while preserving the flexible distributed architecture.

Inventive Principle:

Principle #23Feedback

2Device complexity

If no transport link control function is implemented, then device complexity is reduced, but communication reliability deteriorates due to inability to detect and retransmit lost packets

Engineering Contradiction:

Improvetransport protocol complexityVSAvoiddata transmission reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

A transport link control function acts as an intermediary layer between the application layer and the transport network. This intermediary introduces sequence numbering and loss detection capabilities without requiring complex changes to the underlying transport network infrastructure.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The transport link control function provides self-service by automatically detecting packet losses through sequence number analysis and initiating retransmissions without external intervention. This self-service approach improves reliability while maintaining relatively simple device implementation.

Inventive Principle:

Principle #25Self-service

3Measurement precision

If sequence numbers are allocated to all data packets, then packet loss detection precision is improved, but processing time and overhead increase

Engineering Contradiction:

Improvepacket loss detection precisionVSAvoidpacket processing time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

Sequence numbers are allocated selectively to packets that require reliable delivery, and status reports are generated only when packet losses are detected. This partial action approach provides precise loss detection where needed while minimizing unnecessary processing overhead for packets that are successfully transmitted.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS10531336B2Link control in centralized deployments

Publication Date: 2020.01.07 GOLDHAMER MARIANA

AI summary

A method for cellular network operation includes establishing a transport network communication link in a cellular network between first and second infrastructure cellular entities. A first transport link control function is established within the first infrastructure cellular entity, and a pair transport link control function is established within the second infrastructure cellular entity. Data packets are transmitted through the first and second transport link control functions on the transport network communication link while allocating sequence numbers by the first transport link control function to the transmitted data packets. The pair transport link control function detects, based on the sequence numbers, a loss of a data packet transmitted by the first transport link control function and transmits a status report to the first transport link control function. The forwarding of user traffic from the first infrastructure cellular entity to the second infrastructure cellular entity is controlled responsively to the reports.