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What you’ll learn:
- 这role the high-bandwidth, low-latency PCI Express (PCIe) interconnect in the IoT space.
- 如何在物联网段中使用PCIE架构，例如边缘计算，测试设备，嵌入式/工业PC和汽车。
这Internet of Things (IoT) represents a wide range of vertical markets spanning retail, manufacturing, smart cities, energy and utilities, transportation, public sector, education, hospitality, health and life sciences, automotive, banking, gaming, and entertainment—touching practically every aspect of our human lives（图。1）。
IoT represents a wide range of diverse systems spanning edge/gateway, data-acquisition devices, automotive, modular computers, industrial PC, etc. One of the characteristics of the emerging edge and IoT market is the exponential growth in data as illustrated by a few statistics below:
2025年，40多个IoT设备的数据Zettabytes（ZB）占数据的一半以上。1
50% of data processed outside the data center or cloud by 2022.2
43% of AI tasks taking place on edge devices (vs. cloud) in 2023.3
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年度企业对企业（B2B）IoT收入超过300B美元。4
Most of that data will be processed, stored, and analyzed at the edge to help deliver better latency, conserve network bandwidth, and improve reliability, security, and privacy. As data growth explodes, high-bandwidth I/O capabilities along with AI will become necessary to transport and transform this data into actionable information and valuable insights. In this article, we will delve into the role played by PCI Express (PCIe) technology as the primary I/O interconnect in the IoT space.
PCIE架构为计算平台提供了I/O连接超过三十年。这是由于PCIE技术能够无缝提供具有成本效益的HVM（大量制造）友好，效率高，高带宽和低延迟解决方案，并通过六代技术演变，每提高数据速率一倍生成并与前几代具有完全的向后兼容性（图2）。
其他协议增强功能，例如精确时间测量（PTM），I/O虚拟化以及诸如链接加密之类的安全功能在物联网空间中至关重要。即使多种形式因素（例如PXI，M.2，U.2，CEM，各种形式的各种风味）已经演变以满足物联网计算连续体的各种系统的需求，但它们都使用相同的硅基于常见的PCIE基本规范的成分。
这success of PCIe architecture as a ubiquitous I/O interconnect in the IoT space is due to it being an open industry standard. And it’s backed by a robust compliance program to ensure seamless interoperability between devices made by different companies.
PCI-SIG，由800多家成员公司组成的财团分布在全球范围内，拥有并管理PCI规格并运行合规计划。我们预计PCIE技术将继续发展，以满足IOT细分市场的I/O需求。让我们仔细研究以下物联网段中如何使用PCIE架构：边缘计算，测试设备，嵌入式/工业PC和汽车。
Edge Computing
边缘位置的计算允许资源es needed to move, store, and process data closer to the source of the data or the point of service delivery(图3), catering to different levels of quality-of-service (QoS) expectations.
Based on optimized location, edge computing will be central to developing a new class of applications that require faster decision-making. Edge computing is an evolution and extension of cloud computing to transform the underlying architecture and create an environment ripe for application, service, and business model innovation.
因此，PCIE规范已广泛部署在数据中心市场中，因此位置为加速边缘解决方案的开发。驱动边缘价值主张以及PCIE技术功能如何符合此大图的三个关键性能指标包括：
Latency and determinism:高级应用,如工厂自动化、robotics, industrial process control systems, video surveillance and security, immersive media applications, autonomous vehicles, and content delivery demand sub-milliseconds to tens of milliseconds of end-to-end latency and deterministic deadline-based response. A traditional cloud-based solution can’t meet this requirement.
带宽：By 2022, 82% of IP traffic will be video content. This traffic is expensive to transport to the cloud and process at a cloud data center. End users and service providers are motivated to process video data at the edge to lower latency, reduce jitter, improve video quality, and create new revenue with value-added services such as content delivery networks (CDNs), cloud gaming, or video analytics for enhanced retail experiences and smart-city applications.
数据区域和法规合规性：随着政府实施政策来保护客户数据并维护其地理位置内的数据，例如欧盟的一般数据保护法规（GDPR），数据隐私和安全性正在推动对广泛边缘部署的需求。
PCIE架构是高带宽，低延迟和安全数据连接性标准，非常适合这些应用。Figure 4显示了本地边缘网关的简化框图以及PCIE技术如何为其内部各个子系统提供连接。
Let’s look at this in detail:
Every business needs to proactively plan for network failover for seamless operation. Wide-area network connectivity can be implemented using cellular 4G LTE/5G or wired solutions such as DSL, cable, or fiber-optic connections, each connected through PCIe. In this example, if a wired WAN connection goes down, one can failover to LTE/5G.
这router can provide multiple LAN connections using wired Ethernet or wireless LAN based on Wi-Fi modules. For example, Ethernet-based cameras can be connected to the CPU via an Ethernet switch for a digital surveillance and security (DSS) system. Wireless peripherals such as a point-of-sale (PoS) system in a retail store can connect via the Wi-Fi module.
低数据速率无线连接（例如零售商店中的手持式条形码扫描仪或架子上的温度和湿度传感器）可以通过蓝牙连接到边缘系统。为了提供办公自动化，灯泡，窗帘，遥控器等可以通过蓝牙，Zigbee或Z-Wave无线连接解决方案进行通信。
DSS and networked video recorders, medical imaging systems, etc. need to store the captured data for further processing. Storage that’s fast, reliable, and secure is critical for IoT applications. A high ratio of capacity to physical footprint, along with the ability to withstand harsh environmental conditions, also is an important consideration as edge devices are installed in outdoor harsh environments such as a petroleum refinery.
这NVM Express (NVMe) specification is an interconnect protocol used to access high-speed storage media. It’s designed to connect high-performance NAND flash memory to compute resources over native PCIe links. It’s a streamlined memory interface with 64K I/O queues, each supporting up to 64K I/O operations, eliminating the legacy SCSI command stack and direct-attached-storage (DAS) bottlenecks associated with traditional hard-drive interfaces. This results in a uniquely tuned I/O architecture optimized for solid-state media.
Storage at the edge needs the ability to support 24x7x365 ingestion of new data and must have enough extra bandwidth and I/O capacity to handle batch and ad hoc queries against this data. A PCIe-based host interface also provides NVMe SSDs with the high bandwidth needed to process this aggregated data at the edge into knowledge and convert it into actionable intelligence.
Depending on the vertical market, IoT gateways support a host of legacy and I/O standards as well as custom I/O interfaces. Since the same CPU design is typically used to develop edge solutions servicing multiple markets to achieve economies of scale, PCIe technology provides an efficient way to connect a variety of I/O controllers to expand and aggregate these interfaces. For example, in the industrial-automation market, industrial Ethernet solutions such as EtherCAT, EtherNet/IP, PROFINET, CC-Link-IE, and serial protocols such as CIP (Common Industrial Protocol), PROFIBUS, Modbus, etc. are commonly implemented using PCIe interface aggregator chips. Similarly, BACnet for building automation and control networks, KNX, etc. are used in the building-automation industry.
增强现实技术等新兴应用部门h perception, and gesture recognition require multiple image-sensor interfaces to connect to the application processor with minimal latency between frames. A MIPI-to-PCIe bridge can interface multiple MIPI CSI image sensors and aggregate data to a PCIe output. In the industrial sector, intelligent automation system captures and processes video for building security and quality control. A PCIe bridge captures videos from HDMI, DVI, or SDI interfaces and can transfer full uncompressed video and audio to a host processor for further processing. Similar bridges with LVDS as the video input also are available to support cameras that have LVDS as the video-output interface.
Edge Computing由于其低延迟，高带宽负载商店的语义，与PCIE互连的异质计算的部署增加了。例如，边缘数据处理的增长导致使用专用的加速器用于人工智能（AI），机器学习（ML）和深度学习工作负载。这些基于PCIE的加速器执行并行计算，与传统CPU相比，AI工作负载更快。
Similarly, vision processing units (VPUs) are helping to offload vision workload involving multiple camera streams with high frame rates that have latency-critical processing requirements. A graphics processing unit (GPU) with its massive potential of parallel computing can be used in a vision workload to accelerate the processing of pixel data, in data mining, as well as other AI and ML workloads.
In applications where the algorithms and deep-learning neural networks are still evolving, reconfigurable field-programmable gate arrays (FPGAs) play a major role. Besides the acceleration functions, FPGAs provide many different connectivity options to connect to cameras, sensors, and other devices.
Test Equipment
Data acquisition is the process of measuring an electrical or physical phenomenon, such as voltage, current, temperature, pressure, or sound. From semiconductor device validation to automated production tests, PCI eXtensions for Instrumentation (PXI) systems deliver high-performance modular instruments and other I/O modules that feature specialized timing and synchronization, as well as key software features for test and measurement applications.
PXI systems use commercial PC-based PCI and PCI Express bus technology while combining rugged modular packaging. With this approach, one can meet requirements for timing, synchronization, and throughput across high-channel-count test applications.
Measurement accuracy is the most important consideration in designing any data-acquisition system. The overall performance of the system, including I/O sampling rates, throughput, and latency, are other top considerations. PXI can meet the ever-more-demanding application needs by incorporating the new PCIe standards into future products.5
Embedded/Industrial PCs
工业和嵌入式PC（IPC）是坚固的PC，旨在在恶劣的环境中连续运行（24x7），包括户外应用，例如采矿，农业和能源分配，以及工厂自动化和工艺自动化等工业应用。他们利用开放的PC体系结构并部署高级视频和AI技术。
To realize the promise of the fourth industrial revolution, known as Industry 4.0, modern automation systems have moved away from purpose-built hardware to user-friendly networked PCs with high reliability, more data storage, and greater computing power. Supervisory control and data-acquisition (SCADA) systems and manufacturing execution systems (MES) are examples of such systems.
PCIE技术在这些PC中起着关键作用，用于存储，网络，加速器附件，甚至使用专用硬件连接到传统自动化系统。这导致了降低的资本成本（CAPEX），提高效率和简化运营以降低运营成本（OPEX），从而导致运营技术（OT）和信息技术（IT）基础架构的无缝融合。6
用于工作负载合并的系统(Fig.5)正在利用虚拟化。虚拟化将主机平台划分为多个软件定义的，孤立的环境，该环境具有由管理程序管理的共享资源。
通过多功能CPU，实时操作系统（RTOS），轻量级管理器和硬件辅助虚拟化技术的进步，这种软件定义的基础架构已成为可能。PCIE规范中的I/O虚拟化支持有助于将数据包处理到网络适配器的卸载，以及将虚拟机（VMS）直接分配到虚拟功能，包括磁盘I/O。
在控制和自动化系统中，通常需要将应用程序在子系统内的网络或设备上同步到一个公共时钟，具体级别的准确性不同，具体取决于最终用法。以太网时间敏感网络（TSN）基于IEEE1588和802.1AS标准在系统之间的同步。
PCIE规范的精确时间测量（PTM）协议使TSN网络接口卡（NICS）或其他外围设备可以将网络时间同步到CPU TIMESTAMP，并最终与软件应用程序同步。PTM最大程度地减少了翻译误差，因此以非常精确的精度增加了多个组件的事件的协调。可以通过PTM启用的时间戳在主机处理器或加速器中重新组合来自不同来源的数据，例如相机，传感器等，即使在安全至关重要的应用中，也可以执行准确的分析并采取行动。
IPC提供更大的自定义，可靠性和可扩展性，以及更长的产品生命周期。广泛的系统包括在空间约束环境中的低功率和无风扇设计，安装在表面上的工业面板安装的PC，固定在墙壁或橱柜中的工业机架PC，壁橱中的工业工作站PC以及售货店的PC或Medical PC在售货亭或医疗机构中设备。
A popular form-factor is COM Express developed by the PCI Industrial Computer Manufacturers Group (PICMG).7这ability to plug a COM Express module or standard SFF wireless modules like M.2 onto a carrier board reduces the time and cost to develop a product. The user doesn’t need to understand the typically complex details associated with high-speed signaling, RF design and tuning, etc. for the latest SoCs.
这种方法还简化了获得监管批准所需的努力，例如最终产品的FCC认证。此外，一种模块化设计方法使我们能够通过基于公共解决方案来驱动规模和更广泛采用的通用解决方案来定制解决方案，从而解决“英里宽和英寸深”的物联网市场。
汽车
十多年来，汽车电子设备的复杂性和复杂性一直在增长。8具有车载信息娱乐（IVI）系统，高级驾驶员辅助系统（ADAS）以及车辆到车辆（V2V）和车辆到所有设施（V2X）连接的现代汽车连通性，可以考虑到车轮上的数据中心，并考虑到车辆连接（V2X）(Fig. 6)。为了满足消费者对舒适性的期望并满足对乘客和行人安全的监管要求，这些系统在大众市场模型中越来越普遍，而不仅限于豪华汽车。
With the increased amount of data to be transported, stored, and processed, proven data-center technologies such as PCIe architecture are becoming very common in automotive electronic systems to connect powerful multi-socketed CPU systems. Beyond PCIe-connected GPUs, Wi-Fi, V2X, and LTE/5G cellular modules, specialized vision and AI accelerator ASICs, Ethernet NICs, and FPGAs are common in automotive electronic control units (ECUs).
As expected, this segment has very stringent regulatory, safety, and reliability requirements while operating under extreme conditions, with an expectation of availability without replacement for the entire useful life of about 15 years of a car. PCIe technology, with its high reliability and availability features, is the interconnect of choice to interface to multiple data sources comprising cameras, LiDAR, radar, and ultrasound and infrared sensors. It provides wireless connectivity through Wi-Fi, BT, LTE, 5G, and satellite for the car. It’s also used for connection to storage devices and accelerators(Fig. 7)。
Conclusion
PCIE界面由大多数高性能CPU本地支持。此外，生态系统还包括用于AI/ML加速度，网络，存储和无线连接性的各种可用设备。IP块，现成的标准表格/模块化组件，调试工具以及熟悉IT世界技术的开发人员的大量生态系统的可用性正在加速PCIE体系结构在物联网应用程序中的渗透。这桌子总结PCIE的关键属性，该属性在物联网空间中驱动最佳解决方案。
PCI-SIG凭借以后兼容的方式进行了丰富而成功的历史，以一种向后兼容的方式导航，PCI-SIG置于良好的位置，以继续领导不断发展的物联网景观前进。该开放标准组织的权力和承诺在800多个成员公司的联合创新能力的支持下，使技术敏捷，可扩展，具有成本效益，性能效率和多代元素与所有物联网段和使用模型的相关性在可预见的未来。
References
5.PXI系统联盟
