RLC Entity Reordering Window Initialization for D2D Packet Loss

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Solution Overview

Problem

In Device to Device (D2D) communication, data packets may be discarded due to the lack of a fixed starting point for RLC protocol, causing them to fall out of the reordering window, leading to packet loss.

Innovation Solution

Setting initial values for the VR (UH) and VR (UR) state variables based on the Serial Number (SN) of the first received data packet to ensure all packets remain within the reordering window, using methods such as setting both variables to the SN of the first packet or setting VR (UR) to the difference between VR (UH) and the reordering window size, with MOD operations for SN lengths of 5 or 10 bits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If initial values of VR(UH) and VR(UR) are set to 0 in D2D communication, then the RLC protocol can be applied without network control, but data packets may fall out of the reordering window and be discarded due to lack of fixed starting point

Engineering Contradiction:

ImproveD2D communication capabilityVSAvoidpacket delivery reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies preliminary action by initializing the reordering window boundaries VR(UH) and VR(UR) based on the Serial Number (SN) of the first received data packet before processing subsequent packets. This preliminary setup ensures that the reordering window is properly positioned from the start, preventing packets from falling out of the window due to asynchronous transmission in D2D communication.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the initial parameter values from the conventional 0 to dynamic values derived from the first packet's SN. Specifically, VR(UH) is set to the SN of the first packet, and VR(UR) is set to VR(UH) - reordering window size (with MOD operation for wraparound). This parameter change adapts the reordering window to the actual transmission context, ensuring all packets remain within the window.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If VR(UH) and VR(UR) are initialized to 0, then the RLC entity can start processing immediately, but packets with SN falling outside the reordering window will be incorrectly discarded

Engineering Contradiction:

Improvepacket processing efficiencyVSAvoidpacket loss

Core Design Contradiction:

ProductivityVSLoss of information

Solution Approach 1:

The patent performs preliminary initialization of the reordering window boundaries before packet processing begins. By setting VR(UH) and VR(UR) based on the first packet's SN, the system prepares the correct window range in advance, ensuring that subsequent packets are processed correctly without being discarded due to window misalignment.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses feedback from the first received packet to initialize the reordering window. The SN of the first packet serves as feedback information that determines the initial position of VR(UH) and VR(UR). This feedback mechanism ensures the window is accurately positioned according to the actual transmission context, preventing incorrect packet discarding.

Inventive Principle:

Principle #23Feedback

3Device complexity

If the reordering window is defined with fixed boundaries, then packet processing is simplified, but packets received out of sequence in D2D communication cannot be handled correctly

Engineering Contradiction:

ImproveRLC processing complexityVSAvoidhandling of out-of-sequence packets

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent introduces dynamics by making the reordering window boundaries adaptive rather than fixed. The window boundaries VR(UH) and VR(UR) are dynamically initialized based on the SN of the first received packet, allowing the window to adapt to the actual transmission sequence. This dynamic initialization maintains simplicity while enabling correct handling of out-of-sequence packets.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the static initial parameters VR(UH) and VR(UR) from fixed 0 values to dynamic values based on the first packet's SN. This parameter change allows the reordering window to adapt to different transmission contexts while maintaining the same basic processing logic, thus handling out-of-sequence packets correctly without increasing complexity.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP3136665B1Method for processing data packet of RLC layer and RLC entity

Publication Date: 2018.06.13 CHINA ACAD OF TELECOMM TECH

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AI summary

Disclosed are a method for processing a data packet of an RLC layer and an RLC entity, which are used for solving the problem existing in the prior art that a receiving end incorrectly discards a data packet because the receiving end in D2D communication may not start receiving from a first data packet sent by a sending end when receiving data. The method comprises: according to a serial number (SN) of a received first data packet, setting, by an RLC entity, initial values for a VR (UH) state variable and a VR (UR) state variable of an RLC layer; and according to the SN of the currently received data packet and current values of the VR (UH) state variable and the VR (UR) state variable which are configured in the RLC layer, conducting, by the RLC entity, processing on the currently received data packet, and updating the current values of the VR (UH) state variable and the VR (UR) state variable.