Wireless Access Point Clock Synchronization via Wired Master Signal
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Solution Overview
Problem
Existing wireless communication systems face challenges in synchronizing the clocks of multiple access points, leading to uncertainties in location determination and phase coherence, particularly due to variations in quartz crystals and environmental factors, which affect applications like TDOA, TOA, beam-forming, and MU-MIMO.
Innovation Solution
A method where a central controller generates discrete samples of a continuous waveform and transmits them over a wired medium to access points, synchronizing their local clocks with a master clock, allowing precise reconstruction and transmission of wireless signals, using digital signal processing and analog components to align samples with the master clock, and reducing noise through slow control loops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If access points use independent local clocks based on quartz crystals, then each access point can operate independently, but clock synchronization between access points deteriorates due to frequency variations and environmental factors
Solution Approach 1:
The patent merges the clock functions of multiple access points by having them all synchronize to a single master clock signal distributed through the wired network infrastructure. This centralizes timekeeping authority while allowing access points to maintain independent wireless operation, resolving the contradiction between operational independence and clock synchronization accuracy.
Solution Approach 2:
The master clock acts as an intermediary between the wired network infrastructure and the wireless access points. It receives timing signals from the wired network and distributes synchronized clock signals to all access points, enabling both independent operation and precise synchronization without requiring direct connection between access points.
2Measurement precision
If a central controller distributes waveform samples to multiple access points, then transmission synchronization improves, but processing requirements and network bandwidth consumption increase
Solution Approach 1:
The patent segments the waveform transmission process into two parts: the master clock provides timing synchronization signals, while access points generate their own waveform data locally based on that timing. This segmentation avoids transmitting large amounts of waveform data over the network while maintaining precise synchronization, reducing bandwidth consumption.
Solution Approach 2:
The system performs preliminary synchronization by distributing the master clock signal to all access points before waveform transmission begins. This pre-synchronization allows access points to independently generate and transmit waveforms at precisely synchronized times without requiring continuous control signals during transmission, minimizing ongoing network bandwidth usage.
Data Source
AI summary
Techniques are disclosed to synchronize wireless signal transmission by endpoints controlled by a central controller. For example, an example method of wireless communication includes receiving, at a first device, over a wired medium between the first device and a second device, a plurality of packets from the second device. Each of the plurality of packets comprises data representative of a portion of a signal corresponding to a wireless medium. The method further includes receiving, at the first device, from the second device over the wired medium a synchronization signal based on a common master clock at the second device. The method further includes synchronizing, at the first device, a local clock of the first device to the common master clock based on the synchronization signal. The method further includes reconstructing the signal corresponding to the wireless medium based on the plurality of packets and the synchronized local clock.