Isochronous Circuit Buffer Rate Control
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Solution Overview
Problem
Conventional USB data rate synchronization methods, such as those described by Bei et al., often result in large buffer swings and a high probability of buffer overrun or under run due to clock mismatches, making it difficult to achieve the smallest possible buffer size while maintaining data rate synchronicity.
Innovation Solution
An isochronous circuit with a rate calculator and register that monitors buffer occupation to estimate and adjust data rates, using a time counter and capacity variation calculations to synchronize input and output data rates, thereby reducing buffer swing and preventing buffer overrun or under run.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a small buffer is implemented using conventional data rate control methods, then cost is reduced, but there is a high probability to induce buffer overrun or under run
Solution Approach 1:
The patent implements a feedback mechanism where the second device monitors buffer occupation levels and sends feedback signals to the first device. The first device adjusts its data transmission rate based on this feedback, dynamically balancing buffer occupancy to prevent both overrun and under run conditions while maintaining a small buffer size.
Solution Approach 2:
The system enables self-regulation where the first device automatically adjusts its own transmission rate based on feedback from the second device about buffer status. This self-service approach allows the transmission system to adapt to varying conditions without external intervention, maintaining reliability with minimal buffer capacity.
2Ease of manufacture
If buffer size is reduced to minimize cost, then manufacturing cost is reduced, but buffer swing becomes too large making synchronization difficult
Solution Approach 1:
The patent transforms the static buffer size problem into a dynamic control problem. Instead of relying on a large fixed buffer to absorb variations, the system dynamically adjusts the transmission rate based on real-time buffer occupation monitoring, allowing a small buffer to maintain stable occupancy levels through active rate adaptation.
Solution Approach 2:
The system changes the transmission rate parameter dynamically based on buffer occupation levels. By monitoring buffer status and adjusting the data rate accordingly, the system maintains stable buffer occupancy despite using a small buffer capacity, effectively transforming the stability issue into a controllable parameter adjustment problem.
3Productivity
If conventional data rate control is used with buffer monitoring, then data rate adjustment is achieved, but buffer swing remains too large to reduce buffer size
Solution Approach 1:
The system performs preliminary monitoring of buffer occupation levels before transmission rate adjustments are made. By continuously tracking buffer status in advance and using this information to proactively adjust transmission rates, the system prevents large buffer swings from developing, maintaining stable occupancy with minimal buffer capacity.
Data Source
AI summary
Methods and apparatus for rate control are provided. An isochronous circuit controls data transmission between a first device and a second device. The first device outputs a set of data packets to the isochronous circuit at a first data rate, and the second device pulls the set of data packets from the isochronous circuit at a second data rate. The isochronous circuit comprises a buffer, a rate calculator and a register. The buffer buffers the set of data packets bound to the second device through a USB. The rate calculator monitors occupation of the buffer to estimate the second data rate. The register is coupled to the rate calculator for storage of the second data rate. The first device may access the estimate of the second data rate from the register to update the first data rate.