SOSA aligned VPX backplane

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SOSA aligned VPX backplane from development to deployment

Alexey Mitrofanov, Comtel Electronics GmbH, July 2025

Abstract:

This article addresses the aspects of the MOSA/SOSA implementation of the mission critical applications in context of the designing SOSA aligned OpenVPX backplanes.

Introduction

The Sensor Open Systems Architecture (SOSA) standard is being driven by both Industry and the government as part of the Modular Open Systems Approach (MOSA) for defence systems.  The purpose is to enhance system modularity and interoperability whilst reducing lifecycle costs.

Hosted by the Open Group, two major editions of the SOSA specification have been published in 2019 and 2024. Approximately half of the SOSA technical standard relates to Hardware. It defines Plug-In Cards Profiles (PICPs) based on the OpenVPX (VITA 65) and VNX+ (VITA 90 drafts) PIC form-factors. These form factors cover 6U and 3U VPX, and 19mm VNX size cards. In context of the 6U and 3U OpenVPX, SOSA also defines Power Supply Card (PSC) according to VITA 62 and Mezzanine Cards based on XMC (VITA 42) form factor. Common Electrical and Functional requirements, General mechanics, cooling methods and Environmental Ruggedization as well as Chassis Management aspects referenced to the ANSI/VITA 46, 47, 48, 65, 66, 67 and 91 families of the VPX standards.

 

SOSA modules and backplane slot profiles scheme

A SOSA PICP defines the connector type and how each pin, or pair of pins, is allocated with a prescribed set of communication protocols.  This is known as the Alternative Module Profile Scheme (AMPS) which is defined according to ANSI/VITA 65. However, SOSA does not allow all possible protocols defined in ANSI/VITA 65.1. SOSA also expands the VITA 65 AMPS scheme by adding some SOSA specific fields such as RF pinouts, XMC overlay, and Switch Front Panel Fiber I/O. Important is that AMPS uses an additional construct from VITA 65.0: Alternate Naming Structure (ANS). The ANS specifies which Slot Profile is to be used on the backplane for the corresponding modules. The new AMPS naming convention from the Classic Module Profile naming was necessary to manage the unwieldy number of ANSI/VITA 65.0 Module Profile dash options.

Currently SOSA High-speed serial protocols selected for copper are:

  • Aurora-10Gbaud-64B/66B
  • Display Port
  • Ethernet:
    • 1000Base-B/KX
    • 10GBase-KR/KX4
    • 25GBASE-KR,
    • 40GBASE-KR4
    • 100GBASE-KR4
  • PCIe-Gen2/3/4 for x1/x4/x8 and x16
  • SATA Gen2/3
  • USB3
  • sFPDP-Gen3-10Gbaud-64B/67B.
  • Optical High Speed Serial Protocols:
    • Aurora 10Gbps-
    • 25Gbps-64B/66B
    • Ethernet 10/25GBase-SR
    • 40/100GBase-SR4
  • ARINC 818
  • sFPDP-Gen3-10/25Gbaud-64B/67B

Module depth, cooling, and pitch combinations supported by the last edition of SOSA are 160mm depth for Conduction and Liquid cooled Cards at 1” pitch, Air Flow Through (AFT) Cooled Cards at 1.5” pitch and 100mm Ddepth for Conduction cooled Cards at 1.2” pitch

For the backplane slot profiles SOSA selects the 6 general payload and 3 switch type profiles for 3U VPX card types including I/O intensive, External I/O, Payloads (Full and Half-P), RF/Optical Switch and Radial Clock; Plus 4 general payload and one switch type profiles.

For 6U VPX card types including External I/O and XMC Payloads; and 2 switch type profiles and secure payload profiles for VITA91 High Density 3U VPX.

Compared to OpenVPX specifies in 6U: 6 basic switch slot profiles and 25 different payload/peripheral slots; in 3U: 32 basic switch slot profiles and 39 different payload/peripheral/clock slots. It is also specified the standard backplane profiles 27 types for 6U and 24 for 3U. Also all these profiles have up to 2 digits numbers of extensions.

SOSA aligned VPX backplane

Compared to OpenVPX VITA 65 SOSA does not have standard backplane profiles. The specification contains only backplane slots reference, and none of the VITA 65 backplane profiles is SOSA aligned.

Instead of standard backplane profiles SOSA provides intent of the rules, suggestions and guidance for communication protocol dependant Backplane Connectivity Methodology as well as Backplane Apertures for Analog and Optical Fiber.

Also, SOSA backplane shall include the redundant system IPMB channel for all slot and Chassis Management Modules.

Comtel Electronics has 30+ years expertise of backplane design for different markets including defence applications. As leaders in the market for high speed backplane design, Comtel already have a large number of proven designs that support signaling speeds 100GBASE-KR4.

To support SOSA market, we produce not only backplanes for different SOSA aligned projects of our customers but also provide SOSA aligned development system. The backplane is the core element of it. To meet requirements for application specific SOSA aligned backplanes, Comtel have an on-line configurator tool to help our customer to specify the SOSA aligned slots and topology according to SOSA rules for 3U and 6U VPX backplanes. The development system also provides flexible solution for requires card cages, integrated power and cooling subsystems, user-friendly system monitor and optional VITA 46.11 Chassis Manager.

Simply click here https://comtel-online.com/open-vpx-backplane-configurator/ to start your next SOSA aligned project.

After successful evaluation with our Development system, you can order the backplanes for integration with your system, or we can build deployable chassis according to your project requirements.