How Wi-Fi roaming works?

The Wi-Fi is a wireless network technology which enables to create local wireless networks. Wi-Fi is created on standard IEEE 802.11 (ISO/CEI 8802-11) and is a local area network that uses high frequency radio signals to transmit and receive data over distances of a few hundred feet; uses Ethernet protocol. Generally, Wi-Fi permits to establish connections between computers, high-rate connections, by two modes: Infrastructure and Ad-Hoc. In Ad-Hoc mode, equipments communicate directly immediately. The infrastructural mode is regularly used with Wi-Fi. Here, on the contrary, computers are connected with an Access Point, which is an obligatory central point to all the communications.

The both modes need some information to function: the Service Set Information (SSID), the channel, the data encryption method, a password. We have some stations which correspond to any material with an integrated Wi-Fi, except from an access point. The connection station-access point is done through two phases: Authentication, where the station willing to enter Wi-Fi network has to authenticate itself, and Association. After Authentication, the station is associated and can broadcast on the network. The access point, on his turn, will relay that information to the aimed receivers.

What is Roaming?

The roaming is a technology which enables a station to change his Access Point, internationally, while remaining connected to the network.  In GSM, Roaming is a possibility offered by mobile operators and which permits the customer to use his mobile all over the world without change phone number. To accomplish this, operators have to conclude Roaming agreement with foreign operators. For instance, if you come from South Africa to England, you will be able to keep your South Africa’s number if and if only you’re South African operator conclude a Roaming contract with an England operator in the area you are. In GSM, while in Wi-Fi, Roaming, Handover, are used to represent the same action.

How Wi-Fi roaming works:

The roaming is not integrated to Wi-Fi, even if Wi-Fi is a wireless network. Contrarily to GSM, Wi-Fi didn’t introduce the notion of itinerancy, which justifies roaming absence in the standard IEEE 802.11 (ISO/CEI 8802-11). But today, with the cheapness and the benefits of wireless networks, most company have the willing to use Wi-Fi in all their premises. And they need to pass from an Access Point to another, while remaining connected. So, some operator tried to implement roaming in Wi-Fi through protocols like the Inter Access Point Protocol which need a distribution system to broadcast information between Access Points. This leads to the creation of a “trial and use” (standard 802-11 F) used further by operators to implement their own methods. With standard 802-11 F, the station is re-associated, instead of associated during the connection on a new Access Point. Also, the Access Point has to monitor continuously access to the distribution system.  In the Standard 802-11 F, the station chooses the Access Point it wants to connect on and it operates like this: 

•  A station arrival in the association of areas covered by many Access Points 
•  Moving of a station in the association of areas covered by many Access Points
• Card notification requirement.

Some functions enable the three exchanges seen above. There are request, confirm, indication, response. The first function, request, corresponds to a station arrival in the association of areas covered by many Access Points. Confirm indicates if the function request ends correctly. An Access Point sends a function indication after a request to signal his association with the station aimed. And finally, the function response by which the old Access Point send to the new Access Point all the network information about the aimed station.

The standard 802-11 F failed due to the roaming slowing down. But Wi-Fi roaming goes ahead with the development of proprietor solutions.