3 Network architecture
3.1 Terms and terminology

This section provides definition for various terms used in a wireless network architecture. However, not all entries from a generic architecture exist in all technologies and the exact functionality may be different.

The 802.11 logical architecture contains several main components: station (STA), wireless access point (AP), independent basic service set (IBSS), basic service set (BSS), distribution system (DS), and extended service set (ESS). Some of the components of the 802.11 logical architecture map directly to hardware devices, such as STAs and wireless APs. The wireless STA contains an adapter card, PC Card, or an embedded device to provide wireless connectivity. The wireless AP functions as a bridge between the wireless STAs and the existing network backbone for network access.

A station (STA) might be a PC, a laptop, a PDA, a phone or whatever device having the capability to interfere the wireless medium.

An access point (AP), sometimes called a base station (BS), is a device that allows wireless devices to connect to a wired network using Wi-Fi, or related standards.

A basic service set (BSS) consists of an access point together with all associated STAs. The AP acts as a master to control the STAs within that BSS. The simplest BSS is composed of one AP and one STA.

An extended service set (ESS) is a set of one or more interconnected basic service sets (BSSs) that appears as a single BSS to the logical link control layer at any station associated with one of those BSSs.

When all of the stations in the BSS are mobile stations and there is no connection to a wired network, the BSS is called an independent BSS (IBSS). An IBSS is an ad hoc network that contains no access points, which means they cannot connect to any other basic service set.

A distribution system (DS) is the mechanism by which APs exchange frames with one another and with wired networks, if any. DS is not necessarily a network, and the IEEE 802.11 standard does not specify any particular technology for the DS. In nearly all commercial products, wired Ethernet is used as the backbone network technology.

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Figure 1.9 Independent and infrastructure basic service sets (BSSs).
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Figure 1.10 Extended service set (ESS) and mobility support.