A WLAN is a wireless computer network that links two or more devices using wireless communication to form a LAN within a limited area such as a home, school, campus, or office building. A WLAN is a network system wherein Wi-Fi is one of the most common technologies in this system. Therefore, WLAN includes Wi-Fi.
WLAN technology first appeared in the United States. It was primarily used as a wireless extension of the last-mile network and was mainly applied in households. At that time, the American people had a strong demand for wireless Internet access due to the cabling difficulties (most Americans living in villas with courtyards) and the popularity of laptops and tablets. This in turn accelerated the proliferation of WLANs.
Compared with wired networks, WLANs have the following benefits:
Wi-Fi is a trademark of the WFA, and is also a wireless network communication technology based on IEEE 802.11. The WFA has announced the use of Wi-Fi to improve the interoperability of products in compliance with IEEE 802.11 standards.
WLAN is short for wireless local area network. Quite simply, WLANs provide network communication using radio waves such as lasers and infrared signals, instead of physical connections. They provide wireless network communication using high-frequency radio waves (such as those on the 2.4 GHz, 5 GHz, and 6 GHz frequency bands) and comply with IEEE 802.11 standards. WLAN in our daily life refers to that implemented based on IEEE 802.11 standards. During the evolution and development of WLAN, various technical standards have emerged, such as Bluetooth, Wi-Fi, and HyperLAN2. Among them, Wi-Fi is now most commonly used due to its advantages such as simple implementation, reliable communication, high flexibility, and low implementation costs. Gradually, Wi-Fi becomes a synonym of WLAN.
Simply put, WLAN is a network system, while Wi-Fi is a technology in this network system. Therefore, WLAN includes Wi-Fi.
WLANs are easy to deploy and expand, flexible, and cost-effective. On WLANs, service data is transmitted through radio signals. As such, service data can easily be intercepted or tampered with by attackers when being transmitted on open wireless channels.
Common WLAN security threats are as follows:
To cope with the preceding security threats, differentiated security protection measures are required to protect against network attacks, for example:
On a WLAN, users require mobile communication. The signal coverage of a single AP, however, is limited. As such, users often move from the coverage area of an AP to that of another AP. To prevent network interruptions while users move between different APs, the concept of WLAN roaming is introduced.
WLAN roaming is a process wherein a station (STA) — when moving to the boundaries between two APs — associates with the new AP and disconnects from the original AP, during which connections are not interrupted. Simply put, WLAN roaming is similar to cell handover for a mobile phone. When a mobile phone moves from the coverage area of a base station to that of another base station, the mobile phone still enjoys uninterrupted and seamless call experiences.
Common WLAN roaming technologies include traditional roaming, fast roaming, smart roaming, and lossless roaming.
Virtual access point (VAP): a WLAN service entity on an AP. You can create different VAPs on an AP to provide wireless access services for different user groups.
In enterprise scenarios, typical WLAN networking modes include the following:
The AC + Fit AP architecture is widely used for Wi-Fi network deployment in large and midsize campuses, such as shopping malls, supermarkets, hotels, and enterprise offices. The AC manages and controls all Fit APs connected to it through CAPWAP tunnels. The AC delivers configurations to Fit APs in batches, eliminating the need to configure APs one by one. This greatly reduces WLAN management and maintenance costs. Additionally, STAs can roam between Fit APs because their access authentication is centrally managed by the AC.
In small-scale Wi-Fi coverage scenarios, only a few APs are required. If an additional AC is deployed, the WLAN cost is increased. In such a scenario, Fat APs are recommended if STA roaming is not required. If STA roaming is required, cloud APs are recommended.
A Fat AP can provide Wi-Fi coverage independently without the need of an additional management and control device. However, because the Fat AP controls STA access independently, STAs cannot roam between Fat APs. The STAs can use the Wi-Fi network only within the coverage area of the connected Fat AP.
Therefore, Fat APs are typically deployed to provide small-scale Wi-Fi coverage in home or small office environments. In enterprise scenarios, the AC + Fit AP and cloud management platform + cloud AP networking modes are typically used.
The leader AP function is an extended function of Fat APs. Like an AC, a Fat AP enabled with the leader AP function can be deployed to build a WLAN together with multiple Fit APs. On this WLAN, the Fat AP manages and configures the Fit APs in a unified manner, enabling STAs to easily roam between APs. In the leader AP + Fit AP networking architecture, a Fat AP can be considered as a combination of an AC and a Fit AP. Without the leader AP function, the Fat AP can manage only its own Fit AP module. With the leader AP function configured, the Fat AP can also manage other Fit APs.
Cloud APs provide similar functions as Fat APs, and can be deployed to build small WLANs in home or small office environments. Similar to the AC + Fit AP architecture, the cloud management platform + cloud AP architecture allows cloud APs to be centrally managed and controlled by the cloud management platform. Therefore, this architecture is also applicable to large and midsize networks.
Cloud APs are plug-and-play and are easy to deploy. They can be flexibly expanded out of space restrictions. Therefore, cloud APs are widely used in multi-branch scenarios.
On a WLAN, the transmit end first applies source coding to convert information into digital signals that allow for circuit calculation and processing, and then into radio waves by means of channel coding and modulation. After receiving the radio waves, the receive end demodulates and decodes the radio waves and converts them into information. The information may be an image, a text, a sound, or the like. The transmit and receive ends are connected over interfaces and channels.
