Isochronous Latency Control via Transmitter Timestamp Feedback
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Solution Overview
Problem
Existing latency control mechanisms in wireless applications, such as wireless audio and medical implants, fail to maintain a consistent end-to-end delay across different paths, leading to significant distortion and jitter in audio signals, particularly in applications requiring precise sound source positioning and low power consumption.
Innovation Solution
A latency control mechanism that organizes isochronous data streams into frames with well-defined time references, including time stamps at both the transmitter and receiver sides, allowing for precise control of end-to-end latency by adjusting the reading and writing of audio samples to maintain a constant delay, even across different paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional buffer-based latency control mechanisms are used, then data can be stored to compensate for network delays, but end-to-end latency varies across different paths and nodes, causing significant jitter and distortion in audio signals
Solution Approach 1:
The patent implements a feedback mechanism where the receiver measures the actual end-to-end latency for each audio frame using timestamp information, compares it with a target latency value, and sends control commands back to the transmitter. The transmitter adjusts its data rate based on this feedback to maintain constant latency across all paths, eliminating jitter without complex buffer management at intermediate nodes.
Solution Approach 2:
The patent dynamically changes the data rate parameter of the audio stream based on measured latency conditions. By adjusting the data rate rather than using fixed buffer sizes, the system adapts to varying path delays and maintains consistent end-to-end latency, resolving the contradiction between reliability and complexity.
2Use of energy by moving object
If multiple hops are used to extend transmit range in low power applications, then battery life is extended, but different paths to different nodes introduce variable delays and jitter
Solution Approach 1:
The feedback mechanism measures the actual latency experienced by each audio frame traveling through multiple hops, regardless of the number of intermediate nodes. The receiver sends control commands back to the transmitter to adjust the data rate, compensating for path-specific delays introduced by different numbers of hops, thereby maintaining latency consistency while allowing flexible power-constrained routing.
Solution Approach 2:
The system dynamically adapts the data rate based on real-time latency measurements from multi-hop paths. This dynamic adjustment allows the system to accommodate variable path lengths and numbers of hops while maintaining constant end-to-end latency, enabling extended transmit range without sacrificing latency reliability.
3Productivity
If different data rates are used to adapt to channel conditions, then transmission efficiency is improved, but latency control becomes difficult to maintain across varying rates
Solution Approach 1:
The feedback loop continuously monitors the actual latency experienced by audio frames transmitted at varying data rates. Based on this measurement and comparison with target latency, the system sends control commands to adjust the data rate, ensuring that latency remains constant despite changes in transmission efficiency. This resolves the contradiction by making latency control adaptive to data rate changes rather than vice versa.
Solution Approach 2:
The system establishes a target latency value in advance and uses this predetermined parameter to guide data rate adjustments. By having the desired latency outcome predefined, the feedback mechanism can systematically adjust the data rate to achieve both transmission efficiency and latency control simultaneously.
Data Source
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AI summary
A latency control mechanism for a communication system provides a known constant end-to-end delay between an audio source and one or more end node destinations, even in the case where different paths are used to reach the end nodes. A very low jitter time on the end-to-end latency is obtained, and the latency is controllable within a given range in dependence on the constraints imposed by the implementation. A block RX DPLL and latency control unit 315 adjusts the reading moment and position from the RX buffer 305 so that a delay between the time stamp taken at the source side 200 by the transmitter time stamp unit 210, and the time stamp taken at the receiver side 300 by receiver time stamp unit 310 is constant and equal to a given value.