Next-Gen Networks High-Performance Testing: PCIe Takes the Challenge
Embedded systems can leverage the products being driven by data center applications, using the high-volume cost points and powerful components to create solutions that may be an even better fit to the embedded market than their originally intended usage.
Embedded system architects are often guided towards certain form factors, such as VPX, MicroTCA or PC/104, and overlook one of the computing industry’s most widely adopted technologies—PCI Express (PCIe). Having evolved from the parallel buses of personal computing, PCI Express can be thought of as a desktop PC or commercial server add-in card standard. However, a growing number of developers of embedded applications are recognizing that the flexibility and widespread support PCIe enjoys could bring them benefits. Although by strict definition ‘PCI Express’ is the serial interface, not a form factor, here we will refer to the PCIe form factor, which elsewhere is variously referred to as ‘PCI Express,’ ‘PCI Edge’, ‘PC Expansion’ and ‘CEM 1.1,’ noting that the cards themselves are designed and manufactured in various sizes.
The PCIe form factor also provides an excellent foundation for integrating new technology into legacy systems. For example, the latest FPGAs—such as the Xilinx UltraScale range—are ideal for ASIC prototyping, ASIC emulation and 100G transponder or muxponder applications. They are being adopted for algorithm development and testing prior to deploying in an ASIC for high-performance testing of next generation networks, including 5G (Figure 1). Many of the development systems for these networks are based on proprietary, COTS PCIe or other COTS technologies, and the PCIe form factor is one of the easiest to integrate into almost any system architecture.
Not all applications require the platform management or high-speed connectivity of an architecture such as MicroTCA, so making these technologies available in the PCIe form factor enables customers to leverage existing field-proven designs and add functionality to their server-based applications.
Of course, not every application needs the sheer horsepower performance of the Xilinx® Virtex® UltraScale™ XCVU440 FPGA, arguably the highest performance FPGA available today. Silicon vendors recognize this and typically meet different price/performance levels with a range of parts. Certainly, the variety of Xilinx Virtex, Kintex and UltraScale FPGAs means there is an option for almost every application. PCI Express implementations mean that developers can select the appropriate mix of I/O and processing resources for their specific application.
Software and Firmware Support
Integrators need a lot more than just the hardware to get systems into deployment. Access to firmware, board support packages or other low-level software is critical. It’s helpful when the software arrives as source code that uses an industry-standard such as the VHSIC Hardware Description Language (VHDL), widely used in electronic design automation. Higher-level software is a bonus, and should be flexible enough to move from a development to a deployment environment. Again, industry standards exist here, such as the Experimental Physics and Industrial Control System (EPICS).
Multi Form Factor Development and Deployment
PCIe is a great development platform and, for some applications, ideal for deployment. But some applications require different levels of ruggedization or system management. These applications also demand the ability to use a common architecture across different physical form factors so as to significantly shorten the time it takes a lab project to get into the field. There are also benefits to having a common platform when the same application may be deployed in different environments. For example, a homeland security data traffic monitoring system may live in a data center or central office environment, but may equally be mobile at large public events.
Many large installations, such as those in high energy physics research, have already decided to mix various form factors, including PCIe, MicroTCA, AdvancedTCA and VME, to meet the price-performance point for each of their application classes (Figure 2). They want a common platform, but to take advantage of the different capabilities of the available commercial form factors. The same approach could work for the testing of next-generation networks.
FMC as the Common Platform
The FPGA Mezzanine Card (FMC) standard as defined by VITA 57 describes an I/O mezzanine module with connection to an FPGA or other device with reconfigurable I/O capability. The low-profile design allows use on popular industry-standard slot card, blade and motherboard form factors, including VME, VPX, CompactPCI, AdvancedTCA, MicroTCA, PCI, PXI, and many other low-profile motherboards. The compact size is highly adaptable to many configuration needs and complements existing common low-profile mezzanine technology such as PMC, XMC and AMC.
The key benefit of the FMC standard for next-generation network test, as well as for many data acquisition and signal processing applications, is the wide range of analog-to-digital and digital-to-analog converters (ADC/DAC) available from the open market. Form-factor agnostic at the system level, the same FMC works across multiple system architectures to suit multiple application types and price/performance requirements.
A final benefit of some FMC data acquisition products is that they connect input and output to the same FPGA, leading to very low latency.
Examples Available Today
A survey of some of the PCI Express cards that have entered the market recently offers examples of the suitability of PCIe for next-generation network testing. For instance, VadaTech has recently brought to market three new PCI Express cards featuring Xilinx FPGAs. The PCI516, PCI592 and PCI595 cards (Figure 3) are ideal for bringing COTS PCIe systems up to date with the latest FPGAs, or—because each card has a site that can accommodate an FMC module—for integrating high-end FMCs. All three cards provide direct connections to neighboring cards, avoiding the need to stage data through the host processor, thereby optimizing throughput and minimizing latency for high-performance applications. Active cooling—a feature that is unique to these cards—is provided for both the FPGA and FMC, making the modules ideal for power-hungry applications or those requiring temperature stability for good performance.
The VadaTech PCIe cards mentioned above all leverage designs from existing AMC products, which means the royalty-free VHDL source that is provided with the product works on these cards too. It’s field-proven software to kick-start a development project.
VadaTech also offers more advanced software for data acquisition systems, the DAQ Series. This has a graphical interface for the simplest development or can be integrated with larger applications using the industry-standard Experimental Physics and Industrial Control System (EPICS). This gives developers full flexibility to implement a standalone digitizer with GUI, an EPICS input/output controller (IOC) or to customize the software to suit their specific application. The software comes with sample designs with source code for typical usage models to give developers the fastest start in building a data acquisition system. This kind of software makes it easier for developers using PCIe, FMCs, software and complete solutions to move from one form factor to another and hit deployment quickly.
The simplest reason that PCI Express is good for network test: it can support high processing performance while being lower cost than VITA or PICMG standards, which are designed around less benign environments.
Paul Kuepfer is VP Sales and Marketing at VadaTech. Based in the company’s Nevada, U.S.A. headquarters and manufacturing facility, Kuepfer leads the sales and marketing teams in collaboration with operations, engineering, and finance to increase customer satisfaction.
Ian Shearer is Managing Director of VadaTech UK with responsibility for European sales and also leads the company’s product marketing operation. He has previously worked in commercial and technical roles for Mercury Computer Systems and BAE Systems.