Introduction to WirelessHART Protocol

WirelessHART standard

The WirelessHART communication specification was officially recognized by the International Electrotechnical Commission (IEC) in September 2008 and became the IEC international standard for industrial wireless (IEC 62591). It can meet the process industry's requirements for reliability, anti-interference, and anti-interference in real-time factory applications. Security, networking flexibility and compatibility requirements.

WirelessHART networks support a wide variety of devices from numerous manufacturers, and products should be classified into 5 different product types:

Figure 1 WirelessHART network device types

• Field equipment: basic equipment that realizes on-site sensing or execution functions;

• Adapter: Connect to existing HART field devices to enable wireless communication capabilities;

• Gateway: enables communication between host applications and devices that are members of the wireless network;

• Network manager: Responsible for network configuration, arranging communication between network devices, managing routing tables, and monitoring and reporting the health of the wireless network;

• Handheld devices: used to configure, maintain or control plant assets.

Protocol layer

The WirelessHART protocol stack follows the OSI 7-layer protocol model architecture. Including physical layer, link layer, network layer, transport layer and application layer.

Figure 2 Comparison between OSI 7-layer protocol model and WirelessHART protocol structure

Physical layer

The WirelessHART physical layer is basically a physical layer based on IEEE 802.15.4-2006 2.4GHz DSSS. This layer defines RF characteristics such as signal pattern, signal strength, and device sensitivity. WirelessHART works in the free ISM frequency band of 2400 ~ 2483.5MHz, and its data transmission rate can be as high as 250kbit/s. This frequency band is divided into 16 channels and is numbered 11~26. The frequency spacing between two adjacent channels is 5MHz.

Data link layer

A distinctive feature of the WirelessHART standard is the data link layer based on time synchronization. The communication time slot of the WirelessHART data link layer is strictly defined as 10ms, and TDMA technology is used to support collision avoidance and deterministic communication.

Network layer and transport layer

The network layer and transport layer work together to provide secure and reliable communication for network devices. In order to support the Mesh network structure, each WirelessHART device is required to forward data to other devices.

Application layer

The application layer is the top layer of the WirelessHART standard, which defines various device commands, responses, data types and status reports. In the WirelessHART standard, communication between devices and gateways is based on commands and responses. The application layer is responsible for parsing the message content, extracting the command number, executing the specified command, and generating a response.

Security Architecture

WirelessHART network is a secure network system. Both the MAC layer and the network layer of WirelessHART provide security services. The MAC layer uses a combination of cyclic redundancy check (CRC) and message integrity code (MIC) to provide hop-to-hop data integrity services. Both sender and receiver use CCM mode and AES-128 block encryption algorithm to generate and verify MIC. The network layer employs various keys to provide end-to-end encryption and data integrity services. The WirelessHART security system defines four keys:

• When there is no network key, the public key is used to generate the MAC layer MIC.

• The network key is shared by all network devices and used by network devices to generate MICs at the MAC layer.

• The network access key is unique to each network device. When a device joins the network, the network access key is used by the network manager to authenticate the new device applying for network access.

• Session keys are created by the network manager. A session key is unique to the end-to-end connection between two network devices and is used to provide end-to-end encryption and data integrity services. Session keys can be further divided into unicast keys and broadcast keys.

WirelessHART Series Products

Microcyber's smart wireless products use WirelessHART wireless technology that focuses on process automation. It has the characteristics of self-organizing network, self-healing, low power consumption, data encryption, etc., ensuring reliable operation and flexible and fast installation. Through our wireless modules, wireless gateways, wireless adapters, wireless temperature transmitters and other products, we can quickly realize data collection, process monitoring, equipment operation, maintenance and diagnosis of complex industrial sites. Microcyber's smart wireless products have become the preferred industrial wireless communication solution for domestic end customers. Internationally renowned companies have also joined the ranks of cooperation, and have been widely used in petrochemical, electric power, metallurgy, machinery manufacturing and other fields.

Industrial Internet Access Point

Microcyber is committed to the research and development, production, sales and integrated application of industrial IoT products.

Microcyber is the first fieldbus protocol stack in China and the third in the world to pass international certification, the first fieldbus instrument in China to pass international certification, the first demonstration application of networked control system in China, and the first function in China to pass international certification, the first wireless HART product in China to pass international certification, etc.

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