WLAN Ad-hoc vs. Infrastructure Mode: Differences Explained

In Wireless LAN (WLAN), the main players are Access Points (APs) and Stations (STAs). Stations are essentially wireless network interface cards (NICs). Both APs and STAs adhere to the IEEE 802.11 family of protocols.

Several standards have been released under IEEE 802.11, including 802.11a, 802.11b, 802.11g, 802.11n, 802.11ac, and 802.11ad.

The IEEE 802.11 WLAN standard defines two primary modes of operation: ad-hoc mode and infrastructure mode. This article highlights the differences between these two modes in WLAN networks.

WLAN Ad-hoc Mode

In ad-hoc mode, the WLAN wireless network consists solely of stations (802.11-compliant NICs). There is no access point in the network. The networked systems, or stations, communicate directly with one another. This mode is also known as Independent Basic Service Set (IBSS) or peer-to-peer mode.

Communication occurs directly over wireless radio waves, adhering to 802.11 packet formats. Ad-hoc mode is well-suited for quickly setting up wireless connections in offices, hotels, or locations where wired infrastructure isn’t available.

WLAN Infrastructure Mode

In infrastructure mode, the WLAN network comprises both stations and one or more access points (APs). The Access Point acts as a base station, similar to those used in cellular systems. All communication between stations passes through the AP. Think of the access point as a router for wireless devices.

As mentioned, all stations (e.g., wireless devices, WLAN-compliant laptops, and PCs) communicate through the Access Point (AP). The AP provides connectivity between the wireless RF network and the wired LAN network.

It converts protocols from wireless 802.11 packets to 802.3 Ethernet packets and vice versa. Data packets transmitted from any system (PCs) connected to the LAN to a wireless station will go through the AP. The AP’s role is to convert the LAN protocol into the 802.11 protocol and relay it to all Stations.

All stations or clients receive the packet, but only the client whose address matches the destination field will decode and process the received packet.

A wireless WLAN network with a single AP is referred to as a Basic Service Set (BSS). When multiple APs are available in a network to form a sub-network, it’s called an Extended Service Set (ESS). Similar to cellular networks, WLAN networks also offer roaming capabilities. This feature allows a client or Station to roam among multiple APs using different RF frequency channels. Refer to WLAN channels for 2.4GHz, 3.5GHz, and 5GHz bands.