User's Manual

!AcroLAN Card User’s Guide Version 20002.5

Page 6 of 38

Figure 1. Ad Hoc Mode

l Infrastructure Mode

In infrastructure mode, the wireless network consists of at least one access

point connected to the wired network infrastructure and a set of wireless end

stations. This configuration is called a Basic Service Set (BSS). An Extended

Service Set (ESS) is a set of two or more BSSs forming a single sub-network.

Since most corporate WLANs require access to the wired LAN for services

(file servers, printers, Inter-net links) they will operate in infrastructure mode.

Figure 2. Infrastructure Mode

ƒƒ

ƒ Roaming

Wireless communication is limited by how far signals carry for given power output.

WLANs use cells, called microcells, similar to the cellular telephone system to extend

the range of wireless connectivity. At any point in time, a mobile PC equipped with a

WLAN adapter is associated with a single access point and its microcell, or area of

coverage. Individual microcells overlap to allow continuous communication within wired

network. They handle low power signals and “hand off” users as they roam through a

given geographic area.

The 802.11 MAC layer is responsible for how a client associates with an access point.

When an 802.11 client enters the range of one or more APs, it chooses an access point

to associate with (also called joining a Basic Service Set), based on signal strength and

Distribution System (DS)

Service Set (SS) – Multiple

le Cells

Access Point (AP)

Ethernet (802.3)