Dejittering System for VoLTE Packet Latency Control
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Solution Overview
Problem
Jitter in IP-based cellular communication networks, such as VoLTE, causes variations in packet latency, affecting voice and media playback by making it difficult for target terminals to lock onto the clock of the source terminal, leading to poor playback quality.
Innovation Solution
A dejittering system is placed between base stations and the core network, which records packet arrival times and delays packets to achieve a target latency, ensuring consistent packet delivery times and reducing jitter by adjusting the delay duration based on the difference between arrival times and target latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If packets are transmitted through the communication network without delay, then the transmission speed is maintained, but the packet latency varies causing jitter that degrades playback quality
Solution Approach 1:
The system performs preliminary measurement of packet arrival times at two different locations in the network. By measuring the arrival time difference before final delivery, the system can proactively calculate the required delay duration and apply compensatory delay to achieve consistent playback timing, preventing jitter-related playback quality degradation
Solution Approach 2:
The system dynamically adjusts the delay duration for each packet based on the measured arrival time difference. The delay amount is not fixed but varies according to the actual network conditions observed for each packet, allowing the system to adaptively compensate for jitter while minimizing overall latency
2Reliability
If a fixed delay is applied to all packets, then playback quality improves, but the overall transmission time increases
Solution Approach 1:
Instead of applying a uniform delay to all packets, the system applies delay selectively and individually to each packet based on its specific arrival time characteristics. Each packet receives the precise delay amount needed to achieve target latency, avoiding unnecessary delays for packets that already have acceptable timing
Solution Approach 2:
The system changes the delay parameter dynamically for each packet based on measured network conditions. By calculating the specific arrival time difference for each packet and applying a corresponding delay, the system optimizes the balance between playback quality and transmission efficiency, rather than using a static delay value
Data Source
AI summary
Described embodiments include a system that includes a network interface and a processor. The network interface is configured to receive, at a first time, a packet transmitted from a source communication terminal over a communication network en route to a target communication terminal, before the packet passes through a particular portion of the communication network, and to receive the packet at a second time, after the packet has passed through the particular portion of the communication network. The processor is configured to delay the packet, subsequently to the packet being received at the second time, by a delay duration that is a decreasing function of a duration between the first time and the second time, and to send the delayed packet, subsequently, via the network interface, en route to the target communication terminal. Other embodiments are also described.