RLC Protocol Interruption Handling in LTE Wireless Systems
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Solution Overview
Problem
In wireless communication systems, interruptions in protocol operations, such as resets of the media access control (MAC) protocol, can cause delays and inefficiencies in data retransmissions due to the lack of immediate notification to higher-level protocols like RLC or PDCP, leading to unnecessary delays in reordering and retransmission processes.
Innovation Solution
A method and apparatus that inform the control function of a higher protocol about interruptions in a lower protocol, such as MAC, by considering the reordering timer as expired and updating state variables, allowing for immediate reordering and retransmission decisions, even if the timer is not running, thereby enabling faster status reporting and delivery of data units to upper layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the control function of the first protocol (MAC) is reset to handle interruptions, then the protocol can recover from errors, but the retransmission process experiences delays due to lack of immediate notification to higher protocols
Solution Approach 1:
The patent implements a feedback mechanism where the MAC layer control function notifies the RLC layer control function about interruptions ( Resets). This feedback loop allows the higher protocol to immediately adjust its state variables and retransmission strategies, eliminating delays that would otherwise occur while waiting for timer expiration or packet arrival notifications.
Solution Approach 2:
The RLC layer performs preliminary actions by updating its state variables (such as maximum status transmit state variable or unacknowledged mode receive state variable) immediately upon receiving interruption notifications from the MAC layer. This preliminary preparation allows the system to respond faster when retransmissions are needed, rather than waiting for natural packet arrival or timer expiration.
2Device complexity
If the system waits for timer expiration to detect missing packets, then the protocol operates simply, but service disruptions and processing time increase during handovers
Solution Approach 1:
Instead of passively waiting for timer expiration, the system actively monitors and receives feedback about MAC layer interruptions. This feedback mechanism allows the RLC layer to immediately detect missing packets and initiate retransmission procedures, significantly reducing service disruption time during handovers without substantially increasing protocol complexity.
3Device complexity
If higher protocols continue operating independently without knowing about lower protocol interruptions, then each protocol layer remains simple, but data handling efficiency decreases due to unnecessary reordering delays
Solution Approach 1:
The patent introduces a feedback mechanism that notifies higher protocols (RLC) about interruptions in lower protocols (MAC). This allows the RLC layer to update its state variables and optimize data handling accordingly, improving productivity and reducing reordering delays while maintaining relatively simple protocol implementations through targeted information sharing rather than complete integration.
Data Source
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AI summary
Method and apparatus for reception of data units in a device by means of a first protocol and a second protocol are disclosed. A control function of the second protocol is informed of interruption in a control function of the first protocol. In response thereto a reordering timer of the second protocol is considered as having expired, and a state variable of the second protocol is updated to equal with a highest received state variable.