WLAN Infrastructure mode:
In infrastructure mode, WLAN network is composed of stations as well as one or more access points(APs). The device Access Point is like a base station used in cellular system. All the communications between stations will go through AP. Access point is like a router.
As mentioned all the stations(e.g. wireless devices,wlan compliant laptops and PCs) communicate via Access Point(AP). As mentioned AP provides connectivity between wireless RF network and hardwired LAN network. It converts protocol from wireless 802.11 packets to 802.3 ethernet packets and vice versa.
Data packets to be transmitted from any systems(PCs) connected with LAN to wireless station will go through AP. The AP role here is to convert LAN protocol into 802.11 protocol and relay to all Stations. Here all the stations or clients receive the packet but the client whose address matches with the destination field will decode and process the received packet.
The wireless WLAN network with one AP is referred as BSS(Basic Service Set). When more than one APs are available in a network to form sib-network, it is referred as ESS(Extended Service Set).
Similar to cellular network wlan network also offers roaming. In this feature client or Station can roam among multiple APs which are using different RF frequency channels. Refer WLAN channels for 2.4GHz, 3.5GHz and 5GHz bands.
