RTP Packet Delay Measurement Using QoS Agents
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Solution Overview
Problem
Conventional methods fail to accurately measure conversational latency or duplex delay in Voice over IP (VoIP) calls, leading to subjective user experiences and unaddressed quality issues in real-world cellular networks, which affects the Quality of Service (QoS) and user satisfaction.
Innovation Solution
Implementing Quality of Service (QoS) agents on user devices to collect and report metrics on Real-time Transport Protocol (RTP) packets, transforming these metrics into probability distribution functions to estimate end-to-end delay, allowing for objective measurement of conversational latency and clock domain offset, even when clocks are not synchronized.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional interarrival jitter evaluation is used, then packet quality can be assessed, but conversational latency cannot be measured
Solution Approach 1:
The patent introduces RTP timestamp fields as intermediaries to carry timing information through the network. These timestamps serve as mediators that enable delay measurement without requiring direct coordination between endpoints, thus resolving the contradiction between maintaining packet flow and measuring conversational latency
Solution Approach 2:
The invention creates copies of timing information by embedding timestamps in RTP packets. These timestamp copies allow the receiving end to calculate delay without needing access to the original transmission time reference, enabling latency measurement while preserving normal packet transmission
2Reliability
If laboratory test equipment is used, then delay can be evaluated, but real customer network conditions cannot be measured
Solution Approach 1:
The measurement system performs self-service by using the existing RTP packet structure and timestamps already present in voice traffic. The endpoints themselves generate and process the timing data without requiring external test equipment, enabling real network measurement while minimizing added complexity
Solution Approach 2:
The RTP timestamp mechanism serves multiple functions: it enables both normal voice packet transmission and delay measurement simultaneously. This universal approach allows the same infrastructure to handle both communication and quality assessment, eliminating the need for separate laboratory test equipment
3Measurement precision
If subjective user reported incidents are used, then user perception can be captured, but objective delay measurement is unavailable
Solution Approach 1:
The patent implements feedback by having endpoints continuously monitor and report delay metrics based on timestamp comparisons. This automated feedback loop provides objective delay measurement data that complements subjective user reports, enabling operators to identify and address quality issues proactively
Data Source
AI summary
In a wireless call between two mobile phones, metrics of conversational latency between the two parties determines a measure of Quality of Service (QoS) for the one or more carriers of real-time transport protocol RTP packets. Packages of metrics are collected at the two terminal devices, each of which may have an independent local clock. A Quality of Service estimation apparatus transforms metric packages into a pair of probability distribution functions for a plurality of real-time transport protocol packets between two endpoints. The offset between the two independent local clocks is determined or eliminated. A key performance indicator is determined for End-to-End RTP stream delay by transforming the timestamps associated with transmission and reception at user equipment hosting a QoS agent.