Synchronous Carrier Frequency Signals for Distributed AP Clock Alignment
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Solution Overview
Problem
In distributed MIMO networks, carrier frequency differences between access points due to varying crystal oscillators lead to phase errors and increased bit error rates, hindering effective signal decoding and network throughput.
Innovation Solution
A method and apparatus for implementing frequency synchronization by a first access point sending synchronous carrier frequency information and signals to other access points, using phase-locked loops and frequency mixers to establish a fixed frequency difference, ensuring consistent reference clocks across access points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If distributed APs use independent crystal oscillators for reference clocks, then device complexity is reduced and deployment is easier, but carrier frequency differences cause phase errors and increased bit error rates
Solution Approach 1:
The patent introduces a frequency synchronization mechanism as an intermediary between distributed APs with independent crystal oscillators. The synchronization mechanism mediates the frequency differences by exchanging frequency information and adjusting local oscillators, allowing independent deployment while maintaining signal reliability through coordinated frequency reference.
2Reliability
If carrier frequency synchronization is implemented between distributed APs, then bit error rate is reduced and signal decoding is improved, but device complexity and system overhead increase
Solution Approach 1:
The patent implements a feedback-based frequency synchronization mechanism where APs exchange frequency information and continuously adjust their local oscillators based on received frequency data. This feedback loop enables automatic frequency alignment without manual intervention, improving signal decoding reliability while keeping the synchronization system manageable through automated control.
3Reliability
If frequency synchronization is achieved through complex coordination protocols, then carrier frequency difference is eliminated, but network overhead and processing time increase
Solution Approach 1:
The patent applies preliminary action by having APs exchange frequency information and perform frequency alignment before actual data transmission begins. The frequency synchronization is established in advance during system initialization or connection setup, eliminating the need for continuous complex coordination during data transmission and reducing overall synchronization time.
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 approach eliminates frequency differences caused by crystal oscillators, enabling synchronized reference clocks and increasing network throughput by ensuring consistent frequency synchronization among access points.
Implementation Method 1
inputting the frequency of the local crystal oscillator to at least two phase-locked loops, PLLs, and obtaining a frequency of one synchronous carrier frequency signal after the frequency of the local crystal oscillator is processed by using each PLL
Implementation Method 2
inputting, to a frequency mixer for processing, the channel of signals output from the combiner, wherein the frequency mixer is configured to mix the channel of signals input to the frequency mixer with a local-frequency signal for outputting
Data Source
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AI summary
Embodiments of this application disclose a synchronous carrier frequency signal sending method, receiving method, and apparatus. The sending method includes: obtaining, by a first access point, synchronous carrier frequency information, where the synchronous carrier frequency information is used to set a synchronous carrier frequency channel for at least one second access point; sending, by the first access point, the synchronous carrier frequency information to the at least one second access point; generating two or more synchronous carrier frequency signals, where the synchronous carrier frequency signals are used to set a working radio frequency reference clock of the second access point, and a frequency difference between the synchronous carrier frequency signals is a fixed value; and sending, by the first access point, the synchronous carrier frequency signals on the synchronous carrier frequency channel. In this method, the second access point determines the synchronous carrier frequency channel based on the synchronous carrier frequency information, and processes received synchronous carrier frequency signals. An obtained frequency difference between the two or more synchronous carrier frequency signals is a fixed value. Therefore, same working radio frequency reference clocks are output, thereby eliminating a frequency difference between different access points.