High-Speed Streaming of Digital Communications in Space

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"Thanks to the NI technology and our engineers’ exhaustive knowledge of it, we saved time in the design and testing stages when designing the system’s hardware and communication network. Our engineers had more time to design and improve the prototypes needed to connect with the product."

- Miguel Navas Sanchez, EIIT

The Challenge:
Building a test bench to verify and validate the high-speed digital communications generated and received by the main modules that make up the Meteosat Third Generation (MTG) satellite communication system.

The Solution:
Using a high-performance NI PXI system with several large bandwidth communication modules, a data acquisition and storage system with streaming capabilities, and a program developed using NI LabVIEW system design software for test bench management.

Author(s):
Miguel Navas Sanchez - EIIT

EIIT’s Special Test Equipment Department has more than 25 years of experience developing testing systems for electronic products and R&D projects. MTG selected our team to design and build a test bench to validate the high-speed digital communication systems that will be used on board its satellites. Thus, we needed a design and quality control system with exceptional capabilities. The main objective of the test benches was to establish an adequate environment for the hardware-in-the-loop testing of these systems.

Due to the confidential nature of this project, we will not mention any specific components of this system or their functions. We aim to explain the problem and the solution from a general point of view so that any reader can get an idea of the surrounding circumstances and the work and effort invested in this project.

The products we wanted to test and validate are part of a high-speed digital communication system and must be subjected to data transfers of several gigabytes (1 GB/3 s) and store files larger than several hundred GBs. The system needs to certify a 192 MB/s speed per channel. Transfer and storage at these speeds can be a challenge because a PCI bus directly connected to a motherboard in any PC has a maximum transfer speed of 133 MB/s.

Because of the high speeds needed in the communication process, the test bench must be able to manage a high volume of data, carry out processing tasks online, and perform continuous operations of accessing files to write/read data, all without slowing down the main processes of data generation/acquisition. This process must be managed within a specific software environment that controls and supervises each different process and also offers the user all the necessary onscreen information and test report generation.

We built an NI PXI system consisting of an NI PXIe–1071 chassis, NI PXIe–8133 controller, NI PXIe–6545 digital waveform generator/analyzer, NI PXI–6509 digital I/O module, NI 8262 module with an NI HDD–8264 RAID enclosure, PCBs designed and built specifically to manage high-speed digital signals, and LabVIEW software, all to meet the data transfer, acquisition, and speed management requirements.

Figure 1. Layout of the VCU Test Bench

The PXIe-1071 features a high-performance rack with three PCI Express slots that can withstand broadband speeds of up to 3 GB/s. Using the NI PXIe–6545 module, we can achieve transfer speeds of 660 MB/s for acquisition and 400 MB/s for digital signal generation because of the card’s internal memory and the streaming capability of this hardware from NI.

Using the rack’s communication buses, we can establish a connection with the NI 8262, which interfaces with the NI HDD–8264 hard drives. This NI hardware provides 12 hard drives, each having a 250 GB memory with a total storage capability of 3 TB and a reading/writing speed of up to 600 MB/s that is sustainable up to 2 TB. Apart from these two cards, we included a PXI–6509 to manage certain control signals necessary to carry out the required tests. This control and communication system is managed with the NI PXIe–8133 controller, which is Windows based for user convenience, and features control software developed with LabVIEW.

How the Equipment Works

The final equipment is made up of two separate test benches. The first bench, called the receptor, carries out the reception, processing, and posterior storage of the data. The objective of the receptor is to validate the performance of the satellite’s data generation systems.

Figure 2. PCB to Communicate With the VCU System

The second bench is called the transmitter, and it must extract the information localised in the storage systems and send it to the satellite’s data reception systems to validate its functionality.

The receptor’s test bench needs to be attached to the satellite’s four different data generation systems to test and verify the performance of each one, as well as to verify the transfer rates and the possible errors that can occur during communication. Therefore, the test bench includes four data entry points that are multiplexed to a single acquisition system. This is similar with the transmitter, but in this case, the bench is made up of one single generation system whose data is multiplexed to four data exit points attached to the satellite’s four different data acquisition systems.

We can integrate both test benches to the corresponding satellite systems with special cables measuring between 4 m and 8 m. Due to these lengths and the high speeds, we designed the PCB to avoid distortions, noise, and interference in the transferred signals, as well as to avoid jitter problems on the watch signals of a few picoseconds. Lastly, we can make the communication with the test system locally or, as per the client’s requirements, with TCP/IP protocols.

Figure 3. VCU System User Interface

Conclusion

Thanks to the N I technology and our engineers’ exhaustive knowledge of it, we saved time in the design and testing stages when designing the system’s hardware and communication network. Our engineers had more time to design and improve the prototypes needed to connect with the product. The perfect integration of the cards with the software development environment, as well as the system’s control design using digital signals, has helped us significantly reduce software development time and helped us finish ahead of the deadline set by our client.

Author Information:
Miguel Navas Sanchez
EIIT
Spain

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