WLAN Components

Wireless NICs

Wireless deployments require a minimum of two devices that have a radio transmitter and a radio receiver tuned to the same radio frequencies:

  • End devices with wireless NICs
  • A network device, such as a wireless router or wireless AP

To communicate wirelessly, laptops, tablets, smart phones, and even the latest automobiles include integrated wireless NICs that incorporate a radio transmitter/receiver. However, if a device does not have an integrated wireless NIC, then a USB wireless adapter can be used, as shown in the figure.

Note: Many wireless devices you are familiar with do not have visible antennas. They are embedded inside smartphones, laptops, and wireless home routers.

USB Wireless Adapter

a USB wireless adapter with a visible antenna plugged into a laptop

Wireless Home Router

The type of infrastructure device that an end device associates and authenticates with varies based on the size and requirement of the WLAN.

For example, a home user typically interconnects wireless devices using a small, wireless router, as shown in the figure. The wireless router serves as an:

  • Access point – This provides 802.11a/b/g/n/ac wireless access.
  • Switch – This provides a four-port, full-duplex, 10/100/1000 Ethernet switch to interconnect wired devices.
  • Router – This provides a default gateway for connecting to other network infrastructures, such as the internet.
small wireless router with three visible antenna and ports on the back

A wireless router is commonly implemented as a small business or residential wireless access device. The wireless router advertises its wireless services by sending beacons containing its shared service set identifier (SSID). Devices wirelessly discover the SSID and attempt to associate and authenticate with it to access the local network and internet.

Most wireless routers also provide advanced features, such as high-speed access, support for video streaming, IPv6 addressing, quality of service (QoS), configuration utilities, and USB ports to connect printers or portable drives.

Additionally, home users who want to extend their network services can implement Wi-Fi range extenders. A device can connect wirelessly to the extender, which boosts its communications to be repeated to the wireless router.

Wireless Access Points

While range extenders are easy to set up and configure, the best solution would be to install another wireless access point to provide dedicated wireless access to the user devices. Wireless clients use their wireless NIC to discover nearby APs advertising their SSID. Clients then attempt to associate and authenticate with an AP. After being authenticated, wireless users have access to network resources. The Cisco Meraki Go APs are shown in the figure.

AP Categories

APs can be categorized as either autonomous APs or controller-based APs.

Autonomous APs

These are standalone devices configured using a command line interface or a GUI, as shown in the figure. Autonomous APs are useful in situations where only a couple of APs are required in the organization. A home router is an example of an autonomous AP because the entire AP configuration resides on the device. If the wireless demands increase, more APs would be required. Each AP would operate independent of other APs and each AP would require manual configuration and management. This would become overwhelming if many APs were needed.

Controller-based APs

These devices require no initial configuration and are often called lightweight APs (LAPs). LAPs use the Lightweight Access Point Protocol (LWAPP) to communicate with a WLAN controller (WLC), as shown in the next figure. Controller-based APs are useful in situations where many APs are required in the network. As more APs are added, each AP is automatically configured and managed by the WLC.

Notice in the figure that the WLC has four ports connected to the switching infrastructure. These four ports are configured as a link aggregation group (LAG) to bundle them together. Much like how EtherChannel operates, LAG provides redundancy and load-balancing. All the ports on the switch that are connected to the WLC need to be trunking and configured with EtherChannel on. However, LAG does not operate exactly like EtherChannel. The WLC does not support Port Aggregation Protocol (PaGP) or Link Aggregation Control Protocol (LACP).

Wireless Antennas

Most business class APs require external antennas to make them fully functioning units.

Omnidirectional Antennas

Omnidirectional antennas such as the one shown in the figure provide 360-degree coverage and are ideal in houses, open office areas, conference rooms, and outside areas.

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Directional Antennas

Directional antennas focus the radio signal in a given direction. This enhances the signal to and from the AP in the direction the antenna is pointing This provides a stronger signal strength in one direction and reduced signal strength in all other directions. Examples of directional Wi-Fi antennas include Yagi and parabolic dish antennas.

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MIMO Antennas

Multiple Input Multiple Output (MIMO) uses multiple antennas to increase available bandwidth for IEEE 802.11n/ac/ax wireless networks. Up to eight transmit and receive antennas can be used to increase throughput.

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WLAN Operation