Wistron NeWeb Corporation DNURW5370 User Manual

6. What is roaming?

Roaming is the ability of a portable computer user to communicate continuously while moving

freely throughout an area greater than that covered by a single access point. Before using the

roaming function, the workstation must make sure that it is the same channel number with the

access point of dedicated coverage area.

To achieve true seamless connectivity, the wireless LAN must incorporate a number of different

functions. Each node and access point, for example, must always acknowledge receipt of each

message. Each node must maintain contact with the wireless network even when not actually

transmitting data. Achieving these functions simultaneously requires a dynamic RF networking

technology that links access points and nodes. In such a system, the user’s end node undertakes a

search for the best possible access to the system. First, it evaluates such factors as signal strength

and quality, as well as the message load currently being carried by each access point and the

distance of each access point to the wired backbone. Based on that information, the node next

selects the right access point and registers its address. Communications between end node and

host computer can then be transmitted up and down the backbone. As the user moves on, the end
node’s RF transmitter regularly checks the system to determine whether it is in touch with the

original access point or whether it should seek a new one. When a node no longer receives

acknowledgment from its original access point, it undertakes a new search. Upon finding a new

access point, it then re-registers, and the communication process continues.