Unidirectional Latency Measurement Without Clock Sync
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Solution Overview
Problem
Current methods for measuring unidirectional latency in asymmetric networks, such as cellular networks, require clock synchronization, which is challenging and resource-intensive, often leading to incorrect measurements and poor Quality of Service (QoS) experiences due to the need for high-precision clocks and administrator privileges.
Innovation Solution
A user device measures unidirectional latency by estimating clock offsets over a secondary connection, allowing it to calculate accurate latencies in both uplink and downlink directions without synchronizing system clocks, using a local system clock and repeating measurements to minimize errors, thus conserving resources and avoiding the need for high-precision clocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If clock synchronization is performed using high-precision clocks (e.g., GPS clock) to achieve accurate unidirectional latency measurement, then measurement precision is improved, but device complexity and resource consumption increase significantly
Solution Approach 1:
The patent uses a symmetric connection as an intermediary to establish a relationship between the asymmetric connection latency measurements and clock offsets. By measuring round-trip time through the symmetric connection, the system can calculate clock offsets without requiring direct clock synchronization, thus resolving the contradiction between measurement accuracy and system complexity
Solution Approach 2:
The patent creates a copy of the measurement approach by using a symmetric connection to model and understand the clock relationship, then applying this understanding to the asymmetric connection measurements. This allows accurate latency measurement without directly implementing complex clock synchronization hardware
2Measurement precision
If clock synchronization is performed to enable accurate unidirectional latency measurement, then measurement precision is improved, but ease of operation deteriorates due to requiring administrator privileges and complex configuration
Solution Approach 1:
The system performs self-service by automatically calculating clock offsets using the symmetric connection measurements. The user device autonomously determines the offset values through mathematical calculations based on round-trip time measurements, eliminating the need for manual clock synchronization configuration and administrator intervention
Solution Approach 2:
The symmetric connection acts as a mediator that enables the system to derive clock offset information without direct clock synchronization. This intermediary approach allows the measurement system to function independently without requiring privileged access or complex setup procedures
3Ease of operation
If round trip time measurement is used in asymmetric networks, then ease of operation is maintained, but measurement precision deteriorates due to inability to identify false issues and provide accurate troubleshooting data
Solution Approach 1:
The patent segments the round-trip time measurement into separate unidirectional latency measurements for uplink and downlink directions. By calculating individual latencies for each direction using the symmetric connection as reference, the system provides granular QoS metrics that enable precise troubleshooting rather than aggregated RTT values
Solution Approach 2:
The patent explicitly addresses asymmetric network conditions by developing separate measurement approaches for uplink and downlink directions. The system acknowledges and utilizes the asymmetry in network characteristics to provide direction-specific latency measurements, improving QoS assessment accuracy for asymmetric networks
Data Source
AI summary
A user device may measure unidirectional latency of applications over asymmetric links. The user device may accurately measure application level unidirectional latency over cellular networks, without synchronizing system clocks. The user device may accurately measure the unidirectional latency in both an uplink direction and a downlink direction, without using a high-precision system clock and without synchronizing clocks between the user device and an application server.