Rapid Roaming provides many of the same advantages of 802.11r wireless at a much lower cost in areas where necessary infrastructure does not exist. An enhanced WIFI client monitors surroundings and prepares new possible access points (APs) connection opportunities before die-down and drop-off connection processes take place.

Modern factories heavily rely on Artificial Intelligence (AI) driven processes in order to optimize every step of production. Often, the sensors used to collect data for AI were connected with slow cable-driven serial protocols with RS-232 cables or twisted pairs for RS-422/485. With the development of newer technologies, however, there has been a transition to Ethernet-based communication.

Two main factors played a key role in this process: one, the price of Ethernet nodes went down with the advent of cheap microcontrollers that included fully integrated Ethernet communication hardware in one chipset, and two, sophisticated new sensors came to market that were not compatible with old serial buses.

IEEE 802.11R wireless roaming system diagram

Rapid roaming WIFI

To solve these problems, WIFI communication has become a key technology to deliver metrics from sensors, providing freedom from cables and to allow unrestricted 3D movements by a client in motion such as a vehicle or robot.

The trouble is that 802.11ac wireless communication extends only 100 meters, a distance normally not sufficient for reliable service and requiring multiple access points (AP) be installed to cover a large area of operation. A moving vehicle or robot needs to constantly switch over communication to the next strong signal access point.

The best solution is the implementation of 802.11r across the infrastructure that manages the switch-over mechanism with below 50ms transition. However, some areas of a factory or warehouse may not support 802.11r. In this situation, Antaira’s new Rapid Roaming enhanced WIFI client is an ideal solution, as it monitors surroundings and prepares new possible access points (APs) connection opportunities before die-down and drop-off connection processes take place. Supported by the new Antaira ARS-7235-AC-T dual-radio industrial WAP, Rapid Roaming protocols seek a new AP when communication is still healthy, assuring superior throughput and faster transitions with below 150ms switch time.

IEEE 802.11R wireless roaming

Roaming has been a desired feature in wireless devices for decades. In 2002, the IEEE 802.11r standard was introduced and is still under heavy development with major fundamentals published in IEEE 802.11r-2008. The main goal of 802.11r was to hand over wireless connections between numerous APs along a client travel path without significant delay.

It has been particularly important for Voice over Internet Protocol (VoIP) applications where human conversation requires 50ms or better of transmission time to avoid undesired noticeable interruptions. The 802.11r standard allowed for speed with secure and seamless handoffs where authentication and Quality of Service (QoS) configurations were preconfigured ahead of switching to the next AP. It made for a stable throughput of data without delays caused by the regular authentication process.

To implement 802.11r, the wireless infrastructure needs to support this standard. This typically will require significant additional investment as most systems that support 802.11r must have a Wireless LAN Controller in addition to the APs that are then controlled by the Wireless LAN Controller.

Applications where necessary infrastructure does not exist and there are cost restrictions, then Antaira Rapid Roaming technology can provide many of the same advantages at a much lower cost.

Steps of fast roaming

Authentication and QoS

In this step, two technologies are properly transitioning. Not just units are connected to one AP, but it has the same privileges in respect to communication priority. It is important in voice-over IP scenarios when delays could affect the human-to-human conversation.

Exchange 802.11r (2a – cable, 2b – radio)

This special protocol allows exchange of all necessary information ahead of travel path of a client, making the transition smooth and fast.

Travel path

This is the way Client travels along the available APs.

Infrastructure requirements for rapid roaming include:

1. Same Service Identifier (SSID)
2. Same Password
3. Same Security Mode
4. Sand Band
5. Same Channel Width

In order for the rapid roaming technology to work correctly, it is necessary to use an AP with the same SSID and security key. When rapid roaming is enabled, the client device will be configured to scan for the surrounding APs. It is necessary to set slow scan time intervals to specify relatively slow scans when Received Signal Strength Indication (RSSI) signal levels are high and the client device can comfortably concentrate on delivering the maximum data throughput.

Next, specify the RSSI threshold level that will indicate an imminent need for a new connection. When this level is reached, the client device will be performing fast scans looking for a new AP. When it is detected it will authenticate and auto-connect to the new AP while simultaneously dropping the current connection. This active process eliminates weak signals deprived of links and prepares a new connection ahead when needed.

A warehouse uses autonomous robots that move about stocking shelves and fulfilling orders. A legacy WIFI network to support employees but the network did not have the equipment to support 802.11r.

Additionally, there are two modes of channels for scanning. One mode is “standard” and it works when all the channels are scanned.

The other mode is “intelligent” and it works when a client device for example goes back and forth along the same APs. In this scenario, it can learn those APs channels and look for them auto matically, further speeding up the reconnection process.

Warehouse wireless system

One example of where this scenario plays out is in a warehouse application with autonomous robots that move about the warehouse stocking shelves and fulfilling orders. Here, a legacy WIFI network was already in place to support employees connecting their PCs, tablets and phones, but the network did not have the necessary equipment to support 802.11r.
Antaira was able to provide the solution by fitting each of the robots with an ARS-7235-AC wireless router that could implement Rapid Roaming technology at a fraction of the cost of installing an entirely new wireless network.

Technology report by Antaira