Dynamic Buffer Size Determination for Embedded MAC Controllers
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Solution Overview
Problem
In embedded systems, devices like MAC controllers face buffer under-run issues due to insufficient buffer size, leading to transmission discontinuity and increased manufacturing costs when buffers are oversized to accommodate maximum packet sizes.
Innovation Solution
A method to determine buffer size based on measured buffer fill time, request response time, media data rate, and the number of bus masters, using a time-to-death value to dynamically manage buffer status and arbiter decision-making for efficient data refilling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the buffer size is increased to accommodate the maximum packet size (MPS) to avoid buffer under-run, then transmission reliability is improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent implements a dynamic buffer management system where the buffer size is not fixed at the maximum packet size but is dynamically adjusted based on the actual packet length and transmission status. The buffer allocation is optimized by calculating the minimum required buffer size based on packet length, media data rate, and bus arbitration parameters, thereby reducing unnecessary buffer resources while maintaining transmission reliability.
Solution Approach 2:
The patent changes the parameter of buffer size from a static maximum value to a dynamic value that adapts to different packet lengths and transmission conditions. By introducing parameters such as buffer fill time, request response time, and media data rate, the system calculates and adjusts the optimal buffer size for each transmission scenario, avoiding the need to allocate buffer space for the maximum possible packet size in all cases.
2Quantity of substance
If the buffer size is reduced to decrease manufacturing cost, then manufacturing cost is reduced, but buffer under-run occurs causing transmission discontinuity
Solution Approach 1:
The patent implements a feedback mechanism that continuously monitors buffer status, packet length, and transmission progress. Based on this feedback, the system adjusts buffer allocation and refilling timing to prevent buffer under-run. The feedback loop ensures that the buffer is refilled at appropriate times based on actual transmission needs rather than using a fixed conservative allocation.
Solution Approach 2:
The patent performs preliminary calculations to determine the optimal buffer size and refilling timing before transmission begins. By pre-calculating parameters such as buffer fill time and request response time based on packet length and media data rate, the system prepares the buffer in advance with the exact amount of space needed, preventing under-run without excessive allocation.
3Reliability
If a fixed buffer size equal to MPS is used for all packets, then buffer under-run is avoided, but buffer resources are wasted for small packets
Solution Approach 1:
The patent applies local quality by allocating buffer resources specifically tailored to each packet's actual requirements rather than using a uniform maximum size for all packets. The buffer allocation is localized to match the specific packet length and transmission characteristics, ensuring that each packet receives exactly the buffer space it needs without more, thereby eliminating resource waste while maintaining under-run prevention.
Data Source
AI summary
A method for determining a buffer size of devices in an embedded system is disclosed. A buffer fill time (BFT) and a request response time (RRT) are determined. Next, a media data rate (MDR) and a number of bus masters (NBM) are calculated. Finally, a lowest buffer size of a device is determined according to the BFT, the MDR and NBM of the system.