WLAN adhoc mode vs infrastructure mode-Difference between adhoc mode and infrastructure mode

In Wireless LAN (WLAN) there are two system entities viz. Access Point(AP) and Stations(STAs). Stations are nothing but simple NICs(network interface cards). Both of these devices are compliant to 802.11 family of protocols. There are series of standards released under IEEE 802.11. These include 802.11a, 11b, 11g, 11n, 11ac and 802.11ad. There are two modes defined in IEEE 802.11 wlan standard viz. adhoc mode and infrastructure mode. This page on WLAN adhoc mode vs infrastructure mode describes difference between adhoc mode and infrastructure mode in WLAN networks.

WLAN Adhoc Mode

WLAN adhoc mode

In adhoc mode, WLAN wireless network is composed of only stations (802.11 compliant NICs). There will not be any access point in the network. The networked systems i.e. stations communicate directly with one another. It is also referred as IBSS(Independent Basic Service Set) or peer to peer mode.

Here communication is directly over wireless radio waves and compliant to 802.11 packets.

Adhoc mode is suitable for quick wireless connection setup in office rooms, hotels or in places where wired infrastructure is not available.

WLAN Infrastructure Mode

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 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 sub-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.

What is Difference between

Difference between 802.11 standards viz.11-a,11-b,11-g and 11-n
Difference between 11n, 11ac and 11ad
Difference between 11ac wave1 and 11ac wave2
Difference between WiMAX and WLAN standards

WLAN MAC frames Links

WLAN Association Request and response frame
WLAN authentication Request and deauthentication frame
WLAN beacon frame
WLAN passive vs active scanning frame
WLAN Probe Request and response frame
WLAN reassociation Request and response frame
WLAN RTS and CTS frame

RF and Wireless Terminologies