WLAN

What Is WLAN?

A Wireless Local Area Network (WLAN) is a computer network that connects two or more devices using wireless communication within a limited area such as a home, school, campus, or office building. WLANs utilize radio waves to provide network connectivity, with Wi-Fi being one of the most common technologies employed within this system. Therefore, WLAN encompasses Wi-Fi as a fundamental component.

Benefits of WLAN

WLAN technology first emerged in the United States, primarily as a wireless extension for the last-mile network, mainly in residential areas. The demand for wireless Internet access grew due to cabling difficulties in villas and the increasing use of laptops and tablets. This led to the rapid proliferation of WLANs.

Compared to wired networks, WLANs offer several benefits:

• High Mobility: WLANs are not constrained by cables and port locations, making them ideal for scenarios where users frequently move, such as in office buildings, airport halls, resorts, hotels, stadiums, and cafes.

• Flexible Deployment: WLANs provide coverage in areas where cabling is difficult, such as subways and roadways. Wireless coverage reduces complex cabling needs, simplifying deployment, cutting costs, and enhancing scalability.

Is WLAN the Same as Wi-Fi?

Wi-Fi is a trademark of the Wi-Fi Alliance (WFA) and is based on IEEE 802.11 standards. It aims to improve interoperability between products adhering to these standards. WLAN, or wireless local area network, uses radio waves for network communication, including technologies like lasers and infrared signals, instead of physical connections.

WLANs primarily use high-frequency radio waves (2.4 GHz, 5 GHz, and 6 GHz bands) and comply with IEEE 802.11 standards. While various standards like Bluetooth and HyperLAN2 have evolved, Wi-Fi is the most widely adopted due to its simple implementation, reliable communication, high flexibility, and low cost. Hence, Wi-Fi has become synonymous with WLAN.

In essence, WLAN is a network system, while Wi-Fi is a technology within this system, making WLAN inclusive of Wi-Fi.

Are WLANs Secure?

WLANs are easy to deploy, flexible, and cost-effective. However, the transmission of service data through radio signals on WLANs can be intercepted or tampered with by attackers on open wireless channels. Common security threats include:

• No Wi-Fi Authentication: Attackers can connect to WLANs without authentication and compromise the network.

• Unencrypted Wireless Data: Attackers can intercept and modify service data transmitted on wireless channels.

• Perimeter Threats: Rogue APs advertise the same SSIDs as authorized APs, leading to data interception by attackers.

To counter these threats, various security measures are implemented:

• Link Authentication and User Access Authentication: Prevent unauthorized network use through centralized user authentication solutions.

• Data Encryption: Enhanced security using WPA3, which offers strong encryption with a 256-bit key, protecting data from being cracked.

• Detection and Containment of Rogue APs: Utilizing Wireless Intrusion Detection Systems (WIDS) and Wireless Intrusion Prevention Systems (WIPS) to detect and contain rogue APs, ensuring network protection.

WLAN Roaming

WLAN users require mobile communication, but the coverage of a single AP is limited. WLAN roaming allows a station (STA) to move from the coverage area of one AP to another without interrupting the connection, similar to cell handover in mobile phones. WLAN roaming technologies include traditional roaming, fast roaming, smart roaming, and lossless roaming.

Basic Elements of WLAN

STA: Terminals like PCs with wireless network interface cards or mobile phones supporting WLAN.

AP: Devices providing 802.11-compliant wireless access services, functioning as bridges between wired and wireless networks.

Virtual Access Point (VAP): WLAN service entities on an AP, offering wireless access services for different user groups.

Basic Service Set (BSS): An area covered by an AP where STAs can communicate with each other.

Extended Service Set (ESS): A group of BSSs sharing the same SSID.

Distribution System: Connects multiple wired or wireless LANs through wireless links between APs, enabling data exchange.

WLAN Networking Modes

In enterprise scenarios, typical WLAN networking modes include:

• Centralized AC + Fit AP Deployment: Suitable for large and midsize campuses, with centralized management by an AC that controls Fit APs through CAPWAP tunnels.

• Independent Fat AP Deployment: Fat APs provide independent Wi-Fi coverage, suitable for small-scale environments like homes or small offices.

• Centralized Leader AP + Fit AP Deployment: Fat APs with leader AP functions manage Fit APs, providing unified management and enabling STA roaming.

• Cloud-Based Deployment: Cloud APs are managed and controlled by cloud platforms, ideal for large and midsize networks, offering plug-and-play functionality and flexible expansion.

How Does WLAN Work?

On a WLAN, information is first converted into digital signals through source coding, then into radio waves via channel coding and modulation. The receiving end demodulates and decodes the radio waves back into information. The key processes involved include:

Source Coding: Converts raw information into digital signals, compressing it without distortion using coding schemes like H.264 for videos.

Channel Coding: Detects and corrects information errors, improving transmission reliability with schemes like Binary Convolutional Encoding (BCC) and Low Density Parity Check (LDPC).

Modulation: Converts digital signals into radio waves using high-frequency signals, with common technologies including Quadrature Amplitude Modulation (QAM) and Orthogonal Frequency Division Multiplexing (OFDM).

Air Interface: Invisible interfaces used for wireless communication, connecting to invisible spaces.

Channel: Pipes for transmitting information, with specific frequency bands defined by 802.11 standards for WLANs.