[Day 11] 10. WLAN (Wireless LAN)

WLAN Overview

A Wireless LAN (WLAN) is a local area network that uses wireless communication (like Wi-Fi) to connect devices within a limited area, such as a home, office, or campus, enabling data transfer without physical cables.

1. Media: Radio Frequency
   WLAN uses radio frequency for communication, similar to wired connections but without physical cables.

2. Frequency Bands:

   • 2.4 GHz and 5.0 GHz: These are the public frequency bands used for WLAN; other bands are reserved for military use.

3. 802.11 Standards:

   • 802.11b (2.4 GHz): Up to 11 Mbps; offers longer range due to lower frequency.
   • 802.11g (2.4 GHz): Up to 56 Mbps; also provides good range.
   • 802.11n (5.0 GHz): 150-300 Mbps; suitable for IoT devices but has a shorter range (around 10 meters with obstacles).
   • 802.11a/b: Backward compatible with earlier standards.

4. Range Considerations:
   No fixed distance for WLAN coverage; range can be affected by obstacles like wood and glass, which significantly reduce signal strength.

5. SSID and Channel:

   • SSID(Service Set Identifier): Example name (e.g., "Sunbeam").
   • Channel: Set to auto (1-15).

6. Modes of Operation:

   • Ad-Hoc (IBSS): Direct device-to-device communication without a central access point.
   • Infrastructure Mode: Connects wireless devices to a wired network via an Access Point (AP), functioning like a hub. These are the ones that are used these days. Though, we can configure mode back to Ad-Hoc.

7. Network Types:

   • IBSS (Independent Basic Service Set): Peer-to-peer network without an AP.
   • BSS (Basic Service Set): A BSS consists of a single Access Point and all the devices (stations) connected to it. The AP facilitates communication within the network and connects the wireless devices to the wired network.
   • ESS (Extended Service Set): An ESS is made up of multiple BSSs that are interconnected through a wired network. Each BSS has its own AP, allowing devices to roam between different BSSs while maintaining connectivity. The APs work together to provide a seamless network experience.

Precautions for ESS Implementation

When implementing an ESS to avoid frame duplication and ensure optimal performance, consider the following:

1. Channel Selection:
   Use non-overlapping channels for your APs. In the 2.4 GHz band, channels 1, 6, and 11 are recommended because they do not overlap, minimizing interference and potential frame duplication.

2. Wireless LAN Controller (WLC):
   Implement a Wireless LAN Controller to manage multiple APs. The WLC helps in coordinating channel assignments and power levels across APs, preventing overlapping coverage areas and ensuring efficient resource management.

3. SSID Configuration:
   Ensure all APs in the ESS use the same SSID, which helps devices seamlessly roam between APs without connection interruptions.

4. Proper Placement of APs:
   Strategically place APs to provide adequate coverage while avoiding signal overlap that could lead to interference and frame duplication.

5. Monitor and Adjust:
   Continuously monitor the network for performance issues and adjust channel assignments and AP placements as necessary to optimize the network.