VoLTE ROHC Context Recovery via NACK Feedback
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Solution Overview
Problem
The robust header compression (ROHC) standard for VoLTE in LTE systems lacks an initialization and refresh (IR) packet recovery mechanism, leading to call drops when the IR packet is lost, as the evolved node B (eNB) cannot establish the necessary context for voice packet decompression.
Innovation Solution
A method and apparatus for processing voice calls in LTE systems that involves receiving packets from a terminal, determining if they are IR packets, transmitting a negative acknowledgement (NACK) when the context for ROHC decompression is absent, and re-receiving the IR packet to maintain context and prevent call drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ROHC standard is implemented without an IR packet recovery mechanism, then the system operates according to the standard specification, but call drops occur when the IR packet is lost
Solution Approach 1:
The patent implements a feedback mechanism where the base station sends a NACK (negative acknowledgement) signal to the terminal when an IR packet is lost and context cannot be established. This feedback triggers the terminal to retransmit the IR packet, thereby recovering from the packet loss and maintaining call continuity without requiring complex additional recovery protocols
Solution Approach 2:
The system enables self-service by allowing the terminal to autonomously detect when a NACK is received and automatically retransmit the IR packet without requiring external intervention or complex centralized control. The base station simply needs to send the NACK signal, and the terminal handles the recovery process independently
2Reliability
If the base station requests retransmission of the IR packet by sending a NACK, then the IR packet can be recovered and context established, but transmission time is increased
Solution Approach 1:
The patent applies preliminary action by having the terminal prepare and buffer the IR packet in advance, so that when a NACK is received, the retransmission can occur immediately without additional processing delays. This pre-positioning of the packet minimizes the time loss associated with retransmission
Data Source
AI summary
A method for performing robust header compression (ROHC) of request for comments (RFC) 3095 over a packet data convergence protocol (PDCP) layer to compress and decompress voice over long term evolution (VoLTE) packets is provided. In the voice call operation, an evolved node B (eNB) receives an initialization and refresh (IR) packet transmitted by a user equipment (UE) and performs ROHC compression/decompression on the voice packet with a compressed header based on the information contained in the received IR packet. If the IR packet is lost, the eNB cannot establish the context for the voice packet, resulting in ROHC operation failure and a call drop problem. In order to maintain the voice call, the eNB sends the UE a static negative acknowledgement (SNACK) when a voice packet is received in the state where no context exists.