Access Point Synchronization via Monophonic Signal Phase Compensation
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Solution Overview
Problem
In distributed network MIMO scenarios, frequency offsets between independent crystal oscillators used by access points lead to phase rotation, resulting in accumulated phase errors and increased bit error rates due to channel effects.
Innovation Solution
A synchronization method where a second access point receives a monophonic signal from a first access point, determines the frequency offset between their carriers, and performs phase compensation on target data frames to ensure the phase difference between the carriers is within a specified threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If independent crystal oscillators are used for each access point, then device complexity is reduced and ease of operation is improved, but frequency offsets occur between access points leading to phase rotation and increased bit error rates
Solution Approach 1:
The patent implements a feedback mechanism where the second access point measures the frequency offset between its carrier and the first access point's carrier by receiving a monophonic signal. The measured frequency offset is then used to perform phase compensation on the target data frame, creating a closed-loop system that continuously corrects for oscillator drift and maintains synchronization between distributed access points.
2Reliability
If GPS clock modules are added to each access point, then frequency offsets are reduced, but device complexity and cost increase
Solution Approach 1:
The patent introduces a monophonic signal as an intermediary carrier that travels from the first access point to the second access point. This single-frequency signal serves as a reference that enables the second access point to measure frequency offsets without requiring complex GPS hardware or additional synchronization infrastructure at each node.
Solution Approach 2:
The patent creates a simplified reference signal (monophonic signal with single frequency) that copies only the essential synchronization information needed for frequency offset measurement, eliminating the need for complex GPS clock modules while achieving the same frequency synchronization goal.
3Reliability
If phase compensation is performed on target data frame, then phase difference between carriers is reduced, but additional processing time is required
Solution Approach 1:
The patent performs frequency offset measurement using the monophonic signal before the actual data transmission occurs. By determining the frequency offset in advance and applying phase compensation to the target data frame beforehand, the system minimizes real-time processing delays during critical data transmission phases.
Data Source
Figure 1a~1b
Figure 1c~2a
Figure 2b
AI summary
Embodiments of this application provide a synchronization method and an access point, where the method includes: receiving, by a second access point, a monophonic signal transmitted by a first access point; determining, by the second access point, a frequency offset between a first carrier and a second carrier based on the monophonic signal, where the first carrier is used by the first access point to transmit the monophonic signal, and the second carrier is used by the second access point to receive the monophonic signal; performing, by the second access point, phase compensation on a target data frame based on the frequency offset, so that a difference between a phase of the second carrier and a phase of the first carrier is less than or equal to a first threshold; and transmitting, by the second access point, a phase-compensated target data frame by using the second carrier. According to the embodiments of this application, a system error rate can be reduced.