Wireless Timing Synchronization via Master Beacon Control
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Solution Overview
Problem
WiFi devices in cellular networks face challenges with high current drain and inefficient power saving features, making it difficult to run applications like peer discovery, routing information exchanges, and traffic monitoring without significantly impacting standby time. Additionally, not all devices can receive external timing signals, necessitating continued use of beacon signaling for synchronization.
Innovation Solution
A communications device synchronizes with an external timing reference signal and operates as a master timing control device by transmitting network timing reference signals with intentionally greater time stamps, allowing it to seize control of network timing and synchronize devices with the external reference without significant signaling overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If WiFi devices use internal timing clocks to maintain synchronization, then devices can operate independently without external signals, but timing accuracy degrades over time and devices cannot achieve precise synchronization for power-efficient operations
Solution Approach 1:
The master device performs preliminary timing adjustment by transmitting beacon signals with time stamps that indicate a greater passage of time than actually elapsed. This preliminary action compensates for cumulative clock drift before it becomes significant, allowing slave devices to synchronize their timing without waiting for large deviations to occur.
Solution Approach 2:
The system implements feedback through beacon signaling where the master device continuously monitors network timing and adjusts its beacon transmissions accordingly. The time stamps in beacon signals provide feedback information to slave devices, enabling them to adjust their internal clocks to match the master device's timing, which is itself synchronized to external GPS timing.
2Reliability
If a device operates as a master timing control device and transmits frequent beacon signals to synchronize the network, then timing synchronization accuracy improves, but signaling overhead increases and communication capacity is reduced
Solution Approach 1:
The master device transmits beacon signals at periodic intervals rather than continuously. The patent specifies that beacons are transmitted at a rate of approximately once per second (1 Hz), which is sufficient to maintain synchronization for power-saving applications while minimizing overhead. This periodic transmission allows devices to enter sleep modes between beacons, dramatically reducing power consumption.
Solution Approach 2:
The master device transmits timing information with intentional excess precision by indicating a passage of time greater than actually elapsed. This partial over-synchronization ensures that even if some beacons are missed, slave devices can still achieve and maintain accurate timing synchronization, providing a margin of error that reduces the need for extremely frequent beacon transmissions.
3Reliability
If all WiFi devices receive external timing signals directly, then timing synchronization accuracy improves, but device complexity increases and not all devices can access external signals due to location or receiver capabilities
Solution Approach 1:
The master device acts as an intermediary between external GPS timing signals and the WiFi network. Instead of requiring every device to directly receive and process GPS signals, the master device receives external timing references and redistributes this timing information through beacon signals to all slave devices. This intermediary approach simplifies device requirements while maintaining network-wide synchronization accuracy.
Solution Approach 2:
The timing synchronization function is segmented into two roles: master devices that receive external GPS signals and slave devices that rely on beacon signals. This segmentation allows the system to leverage external timing references where available while maintaining compatibility with devices that lack GPS receivers or are located in areas where GPS signals are unavailable.
4Use of energy by moving object
If WiFi devices use power saving features to extend standby time, then energy consumption decreases, but timing synchronization accuracy deteriorates and applications like peer discovery and routing exchanges become infeasible
Solution Approach 1:
The system uses periodic beacon transmissions at 1 Hz intervals to maintain timing synchronization while allowing devices to enter deep sleep modes between beacons. This periodic structure provides predictable wake-up times for applications like peer discovery and routing exchanges, enabling these applications to operate with known timing windows while maximizing power-saving opportunities during idle periods.
Data Source
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AI summary
A communications device synchronizes itself with respect to an external reference signal, e.g., a GPS signal. The communications device detects timing reference signals, e.g., beacon signals, from a communications network. If the communications device determines that the network is not synchronized to the external timing reference signal, the communications device operates as a master timing control device. In various embodiments, when operating as a master timing control device the wireless communications device communicates time stamps, e.g., in beacon signals, which indicate a greater passage of time than the actual passage of time. When operating as a master timing control device the communications device transmits network timing reference signals at a higher rate than is being used by the network to seize control of network timing and become the master timing control device. The communications device drives the network timing to synchronize network timing to the external timing reference.