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Implementing fast roaming technology

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  • peter shishko
  • August 1, 2022
  • Antaira Technologies, LLC – formerly Aaxeon Technologies
  • feature
Implementing fast roaming technology
Implementing fast roaming technology

Modern factories rely heavily on artificial intelligence-driven processes to optimize every step of production and also rely on accurate data collected by a multitude of sensors. Historically, factories have used slow cable-driven serial protocols such as RS-232 cable and twisted pair for RS-422/485. With the development of new technologies there has been a shift to Ethernet-based communications. Two main factors play an important role in this process. The price of Ethernet nodes has fallen with the advent of cheap microcontrollers containing Ethernet communication hardware fully integrated into a single chipset, and advanced sensors providing data flow are incompatible with older serial buses. .

Wi-Fi communication (wireless Ethernet) is a key technology for providing all the required metrics from sensors. Free yourself from cables for unrestricted 3D movement. Typical 802.11ac wireless communication extends up to 100m. This distance is usually not sufficient and multiple access points (APs) are installed to cover a large operational area. In a go-to-wireless scenario, the client (vehicle or robot) should switch communication to the next stronger signal AP. The best solution is to implement 802.11r throughout your infrastructure. Manage switching mechanisms with transitions of less than 50 ms. In some locations, existing Wi-Fi infrastructure does not support 802.11r, but installations need to be moved, requiring rapid transition times.

One answer in this situation is an enhanced Wi-Fi client that can actively monitor its surroundings and prepare for new AP connection opportunities before the traditional die-down and drop-off connection process occurs. This interrupts communication for more than a minute. Fast roaming takes an active approach, looking for new APs when communication is still good. Excellent throughput and fast transitions are guaranteed with switching times of less than 150ms.

IEEE 802.11r wireless roaming

Roaming has been a desired feature of wireless devices for decades, with the introduction of the IEEE 802.11r standard in 2002. It is still in extensive development using the primary foundations published in IEEE 802.11r-2008. The main goal of 802.11r was to handover wireless connections between many APs along a client’s travel path without significant delays. This is especially important for Voice over Internet Protocol (VoIP) applications where human speech requires transmission times of 50ms or more to avoid noticeable interruptions.

The new 802.11r standard enables speed with secure and seamless handoffs with preconfigured authentication and quality of service (QoS) configurations before switching to the next AP.Achieves stable data throughput without delays caused by normal authentication processing (Figure 1).

Figure 1: The 802.11r standard improves speed with secure and seamless handoffs with preconfigured authentication and QoS configurations before switching to the next AP. This allows for steady data throughput without the delays caused by the normal authentication process.

Fast roaming procedure

  • Authentication and QoS: Two technologies are transitioning nicely in this step. Not only is the device connected to her one AP, but the APs have the same privileges in terms of communication priority. Important for VoIP scenarios where latency can affect human conversations.
  • Exchange 802.11r (2a – cable, 2b – wireless): This special protocol allows all the necessary information to be exchanged before the client’s travel path, making the transition smooth and fast.
  • Travel Path: This is how the client moves along the available APs.

Fast roaming is especially useful for older installations where the existing infrastructure does not support 802.11r. However, it is not as efficient as 802.11r. This seeks to bridge the gap with systems without roaming technology where traditional disconnection and reconnection occurs with new APs. This process can take some time, sometimes longer than a minute. It’s frustrating when a slow-moving client is operating with a very weak AP signal and another AP with a strong signal level is readily available within range. (Figure 2).

Figure 2: AP with strong signal levels available within range.

Fast roaming infrastructure requirements

  • Same Service Identifier (SSID)
  • same password
  • Same security mode
  • same band
  • Same channel width.

For fast roaming technology to work properly, you must use APs with the same SSID and security key. When fast roaming is enabled, client devices are configured to scan for surrounding APs. If the Received Signal Strength Indication (RSSI) signal level is relatively high and client devices can concentrate on providing maximum data throughput, you should set the Slow Scan Time Interval to specify relatively slow scans. Next, you need to specify the RSSI threshold level that indicates the imminent need for a new connection. Once this level is reached, the client device will perform a fast scan looking for new APs. Once detected, it will authenticate and auto-connect to the new AP while disconnecting the current connection.

This active process eliminates weak signals that have been stolen from the link and prepares new connections as needed. In addition, scanning has two channel modes. One mode is “Normal” and works when all channels are scanned. The other mode is ‘intelligent’ and works, for example, when client devices come and go to the same AP. In this scenario, the devices are smart and can learn and automatically seek out those AP channels. This will further accelerate the reconnection process.

To implement 802.11r, your wireless infrastructure must support this standard. Most systems supporting 802.11r require a wireless LAN controller in addition to the AP, and since the AP is controlled by the wireless LAN controller, this usually requires a significant additional investment. For applications that don’t have the necessary infrastructure or have cost constraints, fast roaming technology can provide many of the same benefits at a much lower cost.

Fast roaming application

An example of where this scenario has been deployed is a warehouse application with autonomous robots. Robots navigate the warehouse, stock shelves and fulfill orders. A legacy Wi-Fi network was already in place to support employees connecting PCs, tablets, and phones, but the network lacked the equipment needed to support 802.11r. The solution was to equip each robot with a wireless router that could implement fast roaming technology at a fraction of the cost of installing an entirely new wireless network. (Figure 3).

Figure 3: Attaching a wireless router to each robot enables fast roaming technology.

All images courtesy of Antaira Technologies
This feature was originally published in the June 2022 issue Intec magazine.

About the author

Peter Szyszko is the Director of Engineering at Antaira Technologies.

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