Best Source Selectors classically use signal-to-noise metrics to determine which signal to use from incoming signals. More recently other methods such as Data Quality Metrics (DQM) are also employed for making quantitative decisions on Best Source Selection (BSS). In all cases, it is common to discard the weaker signals for the ones that have good strength or DQM scores. This may reject other signals, though weaker, may contain viable data. There is a method to retain all signals and produce a “golden” stream which is a composite of all the streams made from only the good data. This method is called Best Data Engine (BDE).
The most successful method for getting the best results is to use both methods in tandem. First, each Telemetry (TM) station would use standard BSS methods to choose the best source for that station, then send all the signals (all would have the same data) to a central location, then use BDE for the final result. As the mission continues the individual streams may contribute to the final result or may not depending how they compare.
What is BDE?
BDE takes all the streams and compares the data in each stream by frame aligning all the input streams, then using advanced weighting algorithms (such as last-in-lock, most-in-lock, DQM, and bit voting). Each stream, based on one of these algorithms, will contribute to a composite stream. As the signals change over time the BDE system automatically adapts to the changes in signal quality.
The aim is to optimize the telemetry system’s performance by relying on the best available data source at any given time.
BDE Algorithms
In-lock Weighting:
This algorithm weighs all the channels based on how long each has been in lock and what is in lock now.
Last-in-lock:
Simply uses whatever has been in lock most recently.
BDE:
Uses data quality scores from compatible receivers as a basis for selection.
Bit Vote:
This is a bit-by-bit comparison of the incoming data. This requires 3 or more streams.
Applications and Benefits
Suppose you have a test flight of an aircraft flying around a test range. As the aircraft flies and turns, goes behind mountains or other obstacles, different TM stations will see the signal at different strengths at various times. With BDE, the quality of the output does not change and will match what is being transmitted.
Similarly, if you are tracking something travelling extremely far and it passes several TM stations, as some drop and some pick up the signals, there is also a time delay. BDE accounts for these delays as well. BDE works in real time with any Parraid product with BDE enabled and works as a post process with a file version that operates on Chapter 10 files. For more information, visit https://www.parraid.com/.
