Wireless Audio Video Clock Synchronization via Timestamped Packet Release
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current wireless communication systems face challenges in synchronizing audio and video clocks, leading to latency and jitter issues that can cause buffer overflow or underrun, especially in high-data-rate applications like multimedia distribution and video conferencing, due to clock rate mismatches between transmitters and receivers.
Innovation Solution
The method involves synchronizing local clocks at the source and destination with a reference clock at periodic intervals, adjusting timestamps in packets, and using a phase-locked loop to correct clock errors, allowing packets to be released only when the local clock matches the adjusted timestamp, thereby maintaining packet timing relationships and minimizing latency and jitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If QoS constraints are implemented to ensure timely delivery of frames, then latency is reduced, but the inter-arrival patterns between packets are not retained across the wireless network
Solution Approach 1:
The system uses feedback mechanisms where the receiver monitors packet arrival times and sends timing information back to the transmitter. This feedback loop allows the transmitter to adjust its packet scheduling to maintain inter-arrival patterns while still meeting QoS latency requirements. The receiver's clock synchronization status is fed back to the transmitter, enabling dynamic adjustment of transmission timing.
Solution Approach 2:
Timestamps serve as an intermediary mechanism between the transmitter and receiver. The transmitter inserts timestamps indicating when packets were sent, and the receiver uses these timestamps along with its local clock to reconstruct the original inter-arrival patterns. This intermediary timing information allows the receiver to preserve packet timing relationships even when QoS constraints cause variations in actual arrival times.
2Reliability
If time stamping is used to control release of received frames, then packet timing relationships are preserved, but clock rate mismatch between transmitter and receiver causes buffer overflow or underrun
Solution Approach 1:
The system dynamically adjusts the receiver's clock rate based on timestamps from received packets. Instead of using a fixed clock rate, the receiver continuously synchronizes its clock to match the transmitter's clock rate by comparing timestamps with local clock readings. This dynamic clock adjustment prevents buffer overflow and underrun caused by clock rate mismatch while preserving packet timing relationships.
Solution Approach 2:
The receiver changes its clock rate parameter based on timestamp information from the transmitter. By calculating the time difference between transmitted timestamps and received packet arrivals, the receiver adjusts its clock frequency to match the transmitter's clock. This parameter change ensures that timestamp-based release control works correctly without causing buffer issues due to clock drift.
3Reliability
If clocks are continuously synchronized to maintain timing accuracy, then packet timing relationships are preserved, but system complexity increases
Solution Approach 1:
Instead of continuous synchronization, the system uses periodic clock adjustment based on received packets. The receiver synchronizes its clock at regular intervals by comparing timestamps from periodically transmitted packets with its local clock readings. This periodic synchronization approach maintains timing accuracy while reducing the computational complexity compared to continuous synchronization mechanisms.
Solution Approach 2:
The synchronization mechanism is self-adjusting using only the timestamp information already embedded in the data packets. The receiver autonomously calculates clock drift and adjusts its own clock rate without requiring separate synchronization messages or external intervention. This self-service approach maintains clock synchronization while minimizing system complexity by utilizing existing packet infrastructure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures that audio and video streams arrive at the receiver with preserved timing relationships, preventing buffer issues and providing a seamless user experience without requiring modifications to existing communication systems, ensuring compatibility with older devices and continuous clock synchronization.
Implementation Method 1
using a phase-locked loop to correct clock errors
Data Source
AI summary
System and method for synchronizing clocks and maintaining packet timing relationships in a wireless communications system. A preferred embodiment further comprises periodically synchronizing local clocks at a transmitter and a receiver to a clock reference, adding a timestamp to each application packet at a transmitter of a wireless network, setting the timestamp to a value of a local time at the transmitter plus a link delay, buffering a received packet at a receiver, and releasing the buffered packet to an application level when a value of a local time at the receiver equals the timestamp value in the packet. This can help to ensure that the timing relationships between data packets present at a transmitter is maintained at a receiver, regardless of transport delays (waiting, transmission and processing) incurred by the data packets.