Key Considerations When Planning Industrial Wi-Fi for AS/RS & AGV Systems

Modern factories are increasingly deploying automated storage and retrieval systems (AS/RS) and automatic guided vehicles (AGVs) in their facilities to optimize production efficiency and reliability. This has led to an increase in traffic on factory floors and within industrial facilities. To be able to monitor and control the AS/RS and AGV systems, as well as other moving equipment, control centers in these factories need uninterrupted connectivity. Wi-Fi-based technologies are emerging as the most popular communication method used in AS/RS and AGV systems because they are flexible, easy to implement, scalable, and futureproof. In this article, we discuss some key points to consider when planning a Wi-Fi network for AS/RS and AGV systems.

Plan Before Deploying a Wi-Fi Solution

Before you start installing Wi-Fi access points (AP) in your facility, you must carefully plan the wireless network that you want to build. Some of the key considerations when planning a Wi-Fi network for AS/RS and AGV systems include:

• Evaluating the Network Capacity and Coverage Required

Evaluating the data rate and coverage required for your application is the first step in setting up a good Wi-Fi network. For example, the data rates supported in 802.11g networks are in the range of 6 to 54 Mbps. If the data coverage circle of an AP is smaller, a client device that connects to the AP will benefit from a higher data rate. In addition, the data rate also depends on the transmitter power of the AP. Since a set of network parameters may give different results in different environments, overlapping the network coverage areas (circles) so that each coverage circle overlaps with the previous one at a certain ratio can help clients, installed on moving equipment, stay connected at all times. Restricting the maximum number of clients that can connect per AP also helps maintain stable connections.

• Tackling the Hidden Node Issue

Even when the Wi-Fi coverage is good and the RF signal is strong, you may not get good throughput. Physical obstacles, such as walls, in your factory may be preventing some APs and client from “hearing” each other, leading to the collision of Wi-Fi signals. The RTS/CTS exchange mechanism can be used to avoid collisions between the AP and client signals.

/>

• Mitigating the Effects of Interference

Interference is one of the key performance inhibitors in a Wi-Fi network. Interference can be of three types:

    • – Adjacent channel interference
    • – Co-channel interference
    • – Non-Wi-Fi interference

The first two types are from Wi-Fi sources. Your Wi-Fi network can also be affected by signals from non-Wi-Fi sources such as Bluetooth devices and microwave ovens. You should identify such sources of interference and carefully plan the location of your APs so that you get the maximum possible coverage for client devices.

• Ensuring Seamless Roaming for Clients

Wi-Fi networks have limited coverage, which means multiples APs need to be installed to ensure full coverage in a factory or warehouse. The Wi-Fi client installed on moving parts of the AS/RS or on AGVs must roam from one AP to another as they move around the facility to maintain the connection. Clients typically take a short roaming recovering time (3 to 5 seconds) when they roam between APs. This is not permissible in industrial operations because AGVs and other moving equipment will not be able to report their location to the control center during this period. The roaming recovery time should be in the millisecond range so that the clients do not disconnect from the network and can continue to report the status and location of their host when they roam from one AP to another.

• Selecting and Deploying Antennas

Selecting the right antenna type for the APs and the clients installed on moving vehicles, such as AGVs, is a key factor in building stable Wi-Fi networks. The main principle to be followed when installing antennas, be it on a rack structure or moving path/direction of vehicles, is to ensure that the radiation planes of the transmitting and receiving antennas overlap at all times. This will provide adequate coverage and reliable communication.

• Protecting Against the Impact of Extreme Environments

Some AGVs operate under harsh environmental conditions, such as cold-storage warehouses where the electrical equipment needs to be able to operate at sub-zero temperatures. Therefore, it is essential to have isolation protection at the power input and sometimes also on the antenna ports so that electrical interference does not damage the mobile radios.

Moxa’s Solution

The AWK Series AP/bridge/client solution offers the following capabilities that can help develop reliable wireless solutions for your AS/RS and AGV systems.

    • – Reliable Networks for mobile operations
    • – Maximum Wi-Fi coverage
    • – Compact size