RLC Reordering Timer Management for LTE Packet Loss
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Solution Overview
Problem
In mobile communication systems employing the LTE scheme, the RLC sublayer of the receiving side apparatus faces issues where it waits fruitlessly for receipt of out-of-range RLC-PDUs due to updates in the receiving side window's sequence number limits, leading to unnecessary retransmission control processing.
Innovation Solution
The receiving side apparatus manages a reordering timer and triggers retransmission requests only when an unreceived packet is within the updated receiving side window, stopping and reactivating the timer based on the sequence number updates to avoid fruitless waiting and processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the receiving side apparatus waits for out-of-range RLC-PDUs to maintain sequence order, then packet reordering accuracy is improved, but unnecessary retransmission control processing and time waste occur
Solution Approach 1:
The receiving side window is dynamically updated based on received packet sequence numbers, allowing the reordering timer to be selectively activated only for packets within the valid receiving side window range. This dynamic adjustment prevents waiting for out-of-range packets while maintaining reordering accuracy for valid packets.
Solution Approach 2:
The patent changes the parameter of the receiving side window limits (VR(R) and VR(MR)) based on received packets, and uses these updated parameters to determine whether to activate the reordering timer. This parameter-based control ensures that reordering operations are performed only on packets that can actually be received and processed.
2Reliability
If the receiving side apparatus activates reordering timer for all out-of-sequence packets, then complete packet reordering is achieved, but device complexity and processing overhead increase
Solution Approach 1:
The patent applies different reordering handling strategies based on the local condition of each packet's sequence number relative to the receiving side window. Packets within the window range trigger reordering timer activation, while packets outside the range are discarded without timer activation, creating localized quality control.
Solution Approach 2:
Instead of applying reordering timer to all out-of-sequence packets (excessive action), the patent applies it only to packets within the receiving side window (partial action). This reduces processing complexity while maintaining sufficient reordering reliability for packets that can actually be delivered.
3Adaptability or versatility
If the receiving side window is updated frequently to reflect new packet ranges, then adaptability to new data is improved, but fruitless retransmission requests for out-of-range packets increase
Solution Approach 1:
The patent uses feedback from the receiving side window update process to control reordering timer activation. When the window is updated and a packet falls outside the new window range, the system feeds back this information to prevent reordering timer activation and subsequent fruitless retransmission requests for that packet.
Solution Approach 2:
The patent takes preliminary anti-action by checking whether a packet's sequence number is within the receiving side window before activating the reordering timer. This preliminary check prevents the harmful effect of fruitless retransmission requests from occurring in the first place.
Data Source
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AI summary
In a retransmission-request transmitting method, the receiving side apparatus activates a reordering timer, when receiving a first packet before receiving an unreceived packet with a sequence number smaller than a sequence number of the first packet; triggers transmission of a retransmission request for the unreceived packet, when having not received the unreceived packet by the time of expiration of the reordering timer activated in response to the receipt of the first packet; and stops and reactivates the reordering timer activated in response to the receipt of the first packet, when a value of the sequence number of the first packet falls out of a range of the receiving side window as a result of changing the upper limit value and the lower limit value in accordance with a sequence number of a second packet received from the transmitting side apparatus.