Microwave Transmission Clock Stability During ACM Switching
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Solution Overview
Problem
In microwave transmission systems employing adaptive code and modulation (ACM), changes in ambient factors lead to unstable system clocks during ACM switching, resulting in increased error rates due to varying symbol clock rates and phases.
Innovation Solution
A microwave transmission apparatus with a first service transmitting device featuring a multiplexing unit, stream control unit, interface unit, encoding and mapping unit, and clock tracking unit that adjusts the service clock rate to match the read clock rate, generating a stable symbol clock for stable system clock transfer, even during ACM switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If ACM switching is performed to adapt transmission capacity to ambient factors, then bandwidth utilization ratio is improved, but system clock stability deteriorates
Solution Approach 1:
The patent segments the clock function into two independent parts: a stable system clock that remains fixed during ACM switching, and a variable symbol clock that adapts to transmission conditions. This segmentation allows the system to maintain clock stability while achieving adaptability through ACM switching.
Solution Approach 2:
The patent introduces an intermediary clock tracking mechanism that decouples the relationship between system clock and symbol clock. The clock tracking unit acts as a mediator that generates stable system clocks independent of ACM switching operations, while still enabling adaptive modulation through the variable symbol clock.
2Reliability
If service clock rate is changed during ACM switching to maintain transmission quality, then transmission quality is improved, but error rate increases
Solution Approach 1:
The patent separates the clock functions into a fixed system clock and a variable symbol clock. The system clock remains stable to prevent errors, while the symbol clock adapts to transmission conditions to maintain quality, resolving the contradiction between reliability and transmission quality.
Solution Approach 2:
The patent makes the symbol clock dynamic and adaptive to transmission conditions while keeping the system clock static. This dynamic adjustment of the symbol clock rate allows the system to maintain optimal transmission quality without causing errors from system clock instability.
Data Source
AI summary
A microwave transmission apparatus is provided. A multiplexing unit generates multiplexed data based on a service clock rate. An interface unit writes and reads the multiplexed data at the service clock rate and a read clock rate respectively. An encoding and mapping unit performs encoding and mapping on the multiplexed data using a symbol clock rate to generate symbol data, and sends the symbol data to up conversion units. A clock tracking unit generates the symbol clock according to the system clock, and performs frequency division on the symbol clock to acquire the read clock. A stream control unit adjusts the service clock rate according to a water line error generated by the interface unit, so that the service clock rate is equal to the read clock rate. As a frequency and a phase of the system clock are fixed, even ACM switching occurs, the system clock is stably transferred.