What Is a Correlating Best Source Selector?

In the world of telemetry, data integrity is everything. When multiple receivers are acquiring the same signal, each with varying degrees of quality, how do you ensure you’re using the best version of the data at any given moment? That’s where a Correlating Best Source Selector (BSS) comes in.

What Is a Correlating Best Source Selector?

In the telemetry world, there are many situations where a transmitting device sends telemetry information to multiple ground antenna receiving sites. In these types of applications, the transmitters are typically moving (i.e. aircraft, missile, or ground vehicle). At any point in time the best received signal with the minimum amount of interference is changing as a result of noise, obstructions and / or signal reflections. These applications require an automatic and dynamic method of selecting the best source of data (best receiving site) at every point in time during the mission. This device is called a Best Source Selector.

Because receiving sites are in different locations, the data received at the central BSS location have different delays. In the past, legacy Best Source Selectors performed a hard switch based on frame sync lock and/or errors in the frame sync pattern. Because the data streams are not correlated in time to each other, when a switch occurs from Stream A to Stream B, there would be a drop lock (time jump) in the downstream frame synchronizers. The modern GDP Model 2276C has solved this problem by automatically correlating the streams in time to each other so that when a switch occurs from Stream A to Stream B, there is not drop-lock or time jump downstream. A Weighted Majority Vote algorithm on top of the Correlation allows for error correction..

A Brief History of BSS Technology

Best Source Selectors have been around for many years. GDP Space Systems delivered our first legacy non-Correlating BSS Units well over 30 years ago. Although they were state-of-the-art back then, some issues could not be addressed with the technology available at that time. With the introduction of FPGA (Field Programmable Gate Array) technology and the continuing need for better data to reduce mission test time, GDP worked with the industry and released our first Correlating BSS 15+ years ago.

This product revolutionized data recovery in the flight test and launch industry. With this product, customers achieved over a 5dB performance gain in their downlink. Additionally, for the first time, they were able to switch on bit boundaries and always get the correct but from the correct antenna at any instant in time while not dropping lock on downstream decoms. Today, GDP has the largest installed base of Correlating BSS units worldwide.

Why Choose a GDP Correlating BSS?

GDP’s Model 2267C isn’t just another Best Source Selector; it’s a high-performance, mission-proven solution built to solve the real challenges of modern telemetry operations. Here’s what sets it apart:

Encrypted data? No problem. While other vendors are just now catching up, GDP has supported encrypted PCM stream correlation for over 15 years. It’s baked into the architecture, not bolted on as an afterthought.
True bit-by-bit decisions. In addition to supporting frame-based decisions (RCC DQE/DQM), GDP offers the only true bit-by-bit mode for ultimate accuracy, which is far superior in noisy or high-error environments.
Versatile inputs and outputs. The system supports 16 input channels (Ethernet, Data/Clock, or both) and 6 output groups, all running at full 40 Mbps simultaneously. Need to scale up? Just add another unit, no performance drop.
16 raw decapsulated data/clock outputs. Even if you use encapsulated Ethernet and/or TTL, you still get unwrapped raw PCM access for recording, viewing, or diagnostics, a critical feature for many mission scenarios.
100% FPGA-based. No PCs, no hard drives, no OS updates. Just rock-solid hardware that’s secure, reliable, and consistent across production runs.
Instant visibility. In addition to the remote GUI, the real-time front-panel LED display shows real-time status across all 16 inputs, letting you know at a glance which streams are locked, correlated, or active — invaluable for troubleshooting or live ops.
TMoIP and IRIG standard compliant. Built-in support for 218-10 and 218-20 ensures smooth network transport in modern range environments.
No surprise maintenance fees. Every BSS comes with a 3-year warranty and full support; no hidden annual charges, no expensive licensing traps.

Backed by GDP.

In an environment where data integrity, timing, and signal clarity are mission-critical, GDP’s Correlating Best Source Selector stands out as the trusted choice. With decades of telemetry experience, unmatched hardware reliability, and a customer-first approach to support, GDP continues to lead the way in best source selection technology. Whether you’re modernizing a test range or launching a new program, our solutions are ready to deliver, with the precision and performance your mission demands. Ask for a demonstration today.