Ad hoc Networks
There are two basic structures for WLANs:
Both topologies are supported in IEEE 802.11.
Ad hoc network is also known as IBSS
(Independent Basic Service Set) configuration. Logically, this
configuration is analogous to a peer-to-peer office network in which no single
node is required to function as a server. Ad hoc WLANs include a number of nodes
or wireless stations that communicate directly with one another on a
peer-to-peer basis, without using an access point (AP) or any connection to a
wired network.
Figure 1 Ad-hoc network (IBSS)
IBSS is useful for quickly and easily setting up a wireless network at anyplace where a wireless infrastructure does not exist or is not required for services, such as a hotel room, convention center, or airport, or where access to the wired network is barred (such as for consultants at a client site). Generally, Ad hoc implementations cover a limited area and aren’t connected to any larger network.
In this mode - also called an AP topology - client
devices link up to a wired network through an access point (AP). This is a more
common configuration emphasizing that the WLAN does not replace the wired LAN
but extends the functionality to wireless devices. A single AP can typically
support between 15 and 250 users depending on technology, configuration and
usage with a range of between 20 and 500m [1]. This is called a Basic service
Set (BSS). WLANs are scalable with multiple APs to reduce congestion and
increase the coverage area. A set of two or more APs forming a subnetwork is
called an Extended Service Set (ESS).
Fig.2 Infrastructure Network