Arbitrary Beacon Synchronization Avoiding FMCW Altimeter Interference
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Solution Overview
Problem
In Time Division Multiplexed Access (TDMA) based wireless avionics systems, synchronization of devices is challenging due to interference from Frequency-Modulated Continuous Wave (FMCW) Radio Altimeters, which can cause signal collisions and clock drift, especially when the altimeter signal occupies the beacon channel or matches the beacon period, leading to unsuitable overhead software processing requirements.
Innovation Solution
Implementing an arbitrary timing synchronization beacon (ATSB) system, where a network synchronizing device broadcasts a synchronization beacon on a designated channel that can occur in any timeslot, avoiding periodic interference with the FMCW radio altimeter signal, and using a timeslot allocation function to select non-conflicting timeslots, allowing devices to maintain synchronization without relying on constant periodic beacons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant frequency pulse beacon is used for synchronization, then devices can maintain a network standard sense of time, but the beacon signal will be blocked when the radio altimeter occupies the beacon channel, causing synchronization failure
Solution Approach 1:
The beacon is transformed from a periodic signal with fixed frequency to an arbitrary-time signal with variable frequency. The beacon transmission time is dynamically selected from multiple candidate timeslots based on channel availability, allowing the system to adapt to radio altimeter interference patterns and avoid signal blocking.
Solution Approach 2:
The beacon signal parameters are changed from constant frequency and periodic timing to variable frequency and arbitrary timing. Multiple candidate timeslots are evaluated, and the beacon is transmitted at the optimal time that avoids radio altimeter occupation, fundamentally changing the temporal characteristics of the synchronization signal.
2Stability of the object's composition
If periodic pulse beacons are transmitted at fixed intervals, then devices can maintain consistent time references, but clock drift occurs when beacon signals are lost due to radio altimeter interference
Solution Approach 1:
Multiple candidate beacon timeslots are pre-calculated and stored before actual beacon transmission. These candidate timeslots are evaluated for potential radio altimeter interference in advance, and the system is ready to select from multiple options when transmitting the beacon, ensuring that a suitable transmission time is always available.
Solution Approach 2:
The system monitors radio altimeter signal patterns and uses this feedback to dynamically select beacon transmission timeslots. By continuously tracking the radio altimeter's frequency sweeping behavior, the system can predict when the beacon channel will be occupied and adjust beacon timing accordingly to avoid signal loss.
3Measurement precision
If software protocols are implemented to correct clock drift, then synchronization accuracy can be maintained, but processing overhead increases significantly
Solution Approach 1:
The system converts the potential harm of radio altimeter interference into a benefit by using the knowledge of radio altimeter behavior to proactively select optimal beacon transmission times. Instead of reacting to interference with complex correction protocols, the system prevents interference from occurring in the first place by choosing timeslots when the beacon channel is guaranteed to be free.
4Adaptability or versatility
If the beacon period matches the radio altimeter period, then timing coordination might be simplified, but multiple sequential beacon frames are lost causing internal clock drift to exceed tolerance
Solution Approach 1:
The beacon transmission is segmented across multiple candidate timeslots rather than relying on a single fixed periodic interval. This segmentation allows the system to distribute beacon transmissions across different time windows, ensuring that at least one beacon will be successfully transmitted even if some timeslots are occupied by the radio altimeter.
Data Source
AI summary
Systems and methods to synchronize wireless device nodes in the presence of a FMCW radio altimeter are provided. In one embodiment, a wireless device network comprises: a plurality of device nodes that share a radio frequency spectrum using time-division multiple accesses; a network synchronizing device in wireless communication with the plurality of device nodes, the network synchronizing device coupled to a timeslot allocation function, wherein the timeslot allocation function allocates to the network synchronizing device a timeslot on a first designated synchronization channel within the radio frequency spectrum; wherein the network synchronizing device broadcasts an arbitrary timeslot synchronization beacon to the plurality of device nodes on the first designated synchronization channel in the timeslot; wherein the arbitrary timeslot synchronization beacon comprises a Sync Timeslot identifier that identifies the timeslot, and a Sync Time indicator that includes a time that the arbitrary timeslot synchronization beacon was transmitted.