Wireless LAN & WLAN Concepts

Wireless LAN & WLAN Concepts

In this article we will discribe Wireless LAN & WLAN Concepts. The components of a wireless LAN infrastructure and wireless topologies.

What is Wireless Technology

Current business networks evolve to support people who are in continuous movement. People connect using various devices, such as desktops and laptops, tablet PCs and smartphones. This is the vision of mobility in which people can travel and take their connection to the network with them.

There are many different infrastructures (wired LAN, service provider networks) that make this type of mobility possible; However, in a business environment, the most important is the wireless LAN (WLAN) .

Benefits of Wireless LAN technology

There are many benefits of supporting wireless networks in the business and home environment . Some of the benefits include increasing flexibility and productivity, reducing costs and the ability to grow and adapt to changing requirements.

For daily operations within the office, most companies rely on LAN-based switches. However, employees are increasingly moving and want to maintain access to the company's LAN resources from other locations besides their desk.

Workers want to bring their wireless devices to meetings, their co-workers' offices, conference rooms and even customer sites and, at the same time, maintain access to office resources. Wireless networks provide this kind of flexibility .

• It can generate an increase in productivity.
• Allows access to email and other work related resources quickly and easily.
• They allow to reduce costs.
• They have the ability to adapt to changing needs and technologies.

Wireless Technologies

Wireless communications are used in a variety of professions.

While the combination of wireless technologies is continually expanding, this analysis focuses on wireless networks that allow users to move. In general terms, wireless networks are classified into the following types:

• Wireless personal area networks (WPAN) : have a range of a few meters. In WPAN, devices with Bluetooth or Wi-Fi Direct enabled are used.
• Wireless LAN (WLAN) : they have a range of about 30 m, as in a room, a home, an office and even a campus.
• Wireless wide area networks (WWAN) : they have a range of kilometers, such as a metropolitan area, a hierarchy of mobile data or even links between cities through microwave retransmissions.

Types of Wireless LAN

• Bluetooth : originally it was a WPAN IEEE 802.15 standard that uses a device pairing process to communicate over distances of up to 0.05 mi (100 m). The Bluetooth Special Interest Group ( https://www.bluetooth.org/ ) standardizes the latest versions of Bluetooth.
• Wireless fidelity (Wi-Fi) : It is an IEEE 802.11 WLAN standard that is generally implemented to provide access to the network to home and business users, which allows data, voice and video traffic to be included at distances of up to 300 m (0 , 18 mi)
• Global Interoperability for Microwave Access (WiMAX) : This is a WWAN IEEE 802.16 standard that provides access to wireless broadband services up to 30 mi (50 km) WiMAX is an alternative to cable and DSL broadband connections.
• Cellular broadband : consists of several national and international business organizations that use mobile data access from a service provider to provide cellular broadband network connectivity. Available for the first time in 1991 with second generation cell phones (2G), with higher speeds available in 2001 and 2006 as part of the third (3G) and fourth (4G) generation of mobile communications technology.
• Satellite broadband : Provides network access to remote sites through the use of a directional satellite dish that aligns with a specific satellite in the Earth's geostationary orbit (GEO). It is usually more expensive and requires a clear line of sight.

There are many types of wireless technologies available. However, this chapter focuses on 802.11 WLANs.

Radio frequencies

All wireless devices operate in the radio wave band of the electromagnetic spectrum. It is the responsibility of the Radiocommunication Sector of the International Telecommunication Union (ITU-R) to regulate the assignment of the radio frequency (RF) spectrum.

The frequency ranges, called " bands ", are assigned for different purposes. Some bands in the electromagnetic spectrum are largely regulated and are used for applications such as air traffic control and emergency response communications networks. Other bands are not licensed, such as the industrial, scientific and medical band (ISM) and the national information infrastructure band (UNII).

Wireless communication occurs in the band of radio waves (i.e. 3 Hz to 300 GHz) of the electromagnetic spectrum, as shown in Image 3. The band of radio waves is subdivided into a section of radio frequencies and a microwave frequency section.

Wireless LAN devices have transmitters and receivers tuned to specific frequencies of the radio waveband. Specifically, the following frequency bands are assigned to 802.11 wireless LANs:

• 2.4 GHz (UHF) : 802.11b / g / n / ad
• 5 GHz (SHF) : 802.11a / n / ac / ad
• 60 GHz band (EHF) : 802.11ad

802.11 Standards

The IEEE 802.11 WLAN standard defines how RF is used in ISM frequency bands without a license for the physical layer and MAC sublayer of wireless links.

Over the years, several implementations of the IEEE 802.11 standard were developed. Here are these standards:

• 802.11 : released in 1997 and now obsolete, it is the original WLAN specification that worked in the 2.4 GHz band and offered speeds of up to 2 Mb / s.
• IEEE 802.11a : launched in 1999, operates in the 5 GHz frequency band, less populated, and offers speeds up to 54 Mb / s.
• IEEE 802.11b : launched in 1999, it operates in the 2.4 GHz frequency band and offers speeds of up to 11 Mb / s.
• IEEE 802.11g : launched in 2003, it operates in the 2.4 GHz frequency band and offers speeds of up to 54 Mb / s.
• IEEE 802.11n : launched in 2009, it operates in the 2.4 GHz and 5 GHz frequency bands, and is known as a “dual band device”. Typical data rates range from 150 Mb / s to 600 Mb / s, with a range of up to 70 m (0.5 mi).
• IEEE 802.11ac : launched in 2013, it operates in the 5 GHz frequency band and provides data rates ranging from 450 Mb / s to 1.3 Gb / s (1300 Mb / s).
• IEEE 802.11ad : launched in 2014 and also known as " WiGig ", it uses a triple band Wi-Fi solution with 2.4 GHz, 5 GHz and 60 GHz, and offers theoretical speeds of up to 7 Gb / s.

Wi-Fi Certification

The standards ensure interoperability between devices made by different manufacturers. The three organizations that influence WLAN standards worldwide are the following:

• ITU-R : regulates the assignment of the RF spectrum and satellite orbits.
• IEEE : specifies how RF is modulated to transport information. It maintains the standards for local and metropolitan area networks (MAN) with the family of LAN and MAN IEEE 802 standards. The dominant standards in the IEEE 802 family are 802.3 Ethernet and 802.11 WLAN.
• Wi-Fi Alliance : Wi-Fi Alliance® ( http://www.wi-fi.org ) is a global nonprofit trade association dedicated to promoting the growth and acceptance of WLAN networks.

Wi-Fi Alliance certifies Wi-Fi compatibility with the following products:

• IEEE 802.11a / b / g / n / ac / ad support
• IEEE 802.11i secure with WPA2 ™ and Extensible Authentication Protocol (EAP)
• Wi-Fi Protected Setup (WPS) to simplify device connection
• Wi-Fi Direct to share media between devices
• Wi-Fi Passpoint to securely simplify connection to Wi-Fi coverage zone networks
• Miracast Wi-Fi to display seamless video between devices

Figure 1 shows the Wi-Fi Alliance logos that identify compatibility with a specific feature. Devices that display specific logos support the identified feature. The devices can display a combination of these logos.

Comparison between WLAN networks and a LAN

WLANs share a similar origin with Ethernet LANs. The IEEE adopted the 802 LAN / MAN portfolio of computer network architecture standards. The two dominant 802 working groups are Ethernet 802.3 and WLAN 802.11 . However, there are important differences between them.

WLANs use RF instead of wires in the physical layer and the MAC sublayer of the data link layer. Compared to the cable, the RF has the following characteristics:

• The RF has no limits, like the limits of a wrapped cable.
• The RF signal is not protected from outside signals, as is the cable in its insulating sheath.
• RF transmission is subject to the same challenges inherent in any wave-based technology, such as commercial radio.
• RF bands are regulated differently in each country.

WLANs also differ from wired LANs as follows:

• WLANs connect clients to the network through wireless access points (APs) or a wireless router, rather than through an Ethernet switch.
• WLANs connect mobile devices that, in general, are battery powered, instead of connected LAN devices.
• WLANs support hosts that dispute access to RF media (frequency bands).
• WLANs use a different frame format than wired Ethernet LANs.
• WLANs have major privacy inconveniences because radio frequencies can leave the premises.

WLAN Components

The simplest wireless network requires at least two devices. Each device must have a radio transmitter and a radio receiver tuned to the same frequencies.

However, most wireless implementations require the following:

• Terminals with wireless NICs
• Infrastructure device, such as a wireless router or AP

Wireless NICs

To communicate wirelessly, the terminals require a wireless NIC that incorporates a radio transmitter or receiver and the software driver necessary for it to work.

Laptops, tablet PCs and smartphones now include integrated wireless NICs. However, if a device does not have an integrated wireless NIC, a USB wireless adapter can be used .

Wireless home router

The type of infrastructure device to which a terminal is associated and with which it is authenticated varies according to the size and requirements of the WLAN.

For example, a home user normally interconnects wireless devices through a small integrated wireless router. These smaller integrated routers work like the following:

• Access point : provides 802.11a / b / g / n / ac wireless access.
• Switch : provides a 10/100/1000, full-duplex, four-port Ethernet switch for wired devices.
• Router : provides a default gateway for connection to other network infrastructures.

For example, the Cisco Linksys EA6500 router, shown in Image 8, is usually deployed as a residential or small business wireless access device.

The wireless router connects to the DLS modem of the ISP and announces its services by sending signals containing its shared service set identifier (SSID). The internal devices wirelessly detect the router's SSID and try to associate and authenticate with it to access the Internet.

Wireless Solutions for companies

Organizations that provide wireless connectivity to their users require a WLAN infrastructure to provide additional connectivity options.

The network of a small business shown in Image 9 is an 802.3 Ethernet LAN. Each client (that is, PC1 and PC2) is connected to a switch using a network cable. The switch is the point where clients access the network. Note that the wireless AP also connects to the switch.

Wireless clients use the wireless NIC to detect nearby APs that advertise their SSID. The clients then try to associate and authenticate with an AP. After authentication, wireless users have access to network resources.

Wireless access points

APs can be categorized as stand-alone APs or controller-based APs.

Autonomous AP

Autonomous APs, sometimes referred to as “ heavy APs ,” are autonomous devices that are configured using the Cisco CLI or a GUI.

Autonomous APs are useful in situations where only one pair of APs is required in the network. Optionally, multiple APs can be controlled using the wireless domain services (WDS) and can be managed using the Cisco Works Wireless LAN Solutions (WLSE) engine.

In Image 10, a stand-alone AP is shown in a small network. If wireless demands increase, more APs would be required. Each AP would function independently of the other APs and would require manual configuration and administration.

Controller-based APs

Controller-based APs are devices that depend on the server and do not require initial configuration. Cisco offers two controller-based solutions.

Controller-based APs are useful in situations where many APs are required on the network. As more APs are added, a WLAN controller automatically configures and manages each AP.

In Image 11, a controller-based AP is shown in a small network. Notice how a WLAN driver is now required to manage APs. The benefit of the driver is that it can be used to manage many APs.

Note : Some AP models may operate in standalone mode or in controller-based mode.

802.11 WLAN topologies

Wireless LANs can use different network topologies. The 802.11 standard identifies two main modes of wireless topology:

• Ad hoc mode : when two devices connect wirelessly without the help of an infrastructure device, such as a router or a wireless AP. Examples include Bluetooth and Wi-Fi Direct.
• Infrastructure mode : when wireless clients connect via a router or wireless AP, such as in WLANs. The APs are connected to the network infrastructure through the cable-connected distribution system (DS), such as Ethernet.

Ad hoc mode

There is an ad hoc wireless network when two wireless devices communicate peer-to-peer (P2P) without using APs or wireless routers.

For example, a client's workstation with wireless capability can be configured to operate in ad hoc mode, allowing another device to connect to the station. Bluetooth and Wi-Fi Direct are examples of ad hoc mode.

There is a variation of the ad hoc topology when a smartphone or tablet PC with cellular data access is allowed to create a personal wireless coverage area. Sometimes, this feature is called " network anchoring ."

Generally, a wireless coverage zone is a quick temporary solution that allows a smartphone to provide the wireless services of a Wi-Fi router. Other devices are associated and authenticated with the smartphone to use the Internet connection. Apple's iPhone calls this feature " Internet Sharing ", while Android devices call it " Network tethering and portable coverage zone ."

Infrastructure mode

The IEEE 802.11 architecture consists of several components that interact to provide a WLAN that supports clients. It defines two basic components of the infrastructure mode topology: a set of basic services (BSS) and a set of extended services (ESS).

Basic Services Set

A BSS consists of a single AP that interconnects all associated wireless clients. In Image 13, two BSS are shown.

The circles represent the coverage area within which BSS wireless clients can remain communicated. This area is called the " basic services area " (BSA).

If a wireless client leaves your BSA, you can no longer communicate directly with other wireless clients within the BSA. The BSS is the basic component of the topology, while the BSA is the real coverage area (the terms BSA and BSS are often used interchangeably).

The Layer 2 MAC address of the AP is used to uniquely identify each BSS and is called the “ basic service set identifier. " (BSSID). Therefore, the BSSID is the formal name of the BSS and is always associated with a single AP.

 Extended Service Set

When a single BSS provides insufficient RF coverage, two or more BSSs can be joined through a common distribution system (DS) to form an ESS.

Wireless clients in one BSA can now communicate with wireless clients in another BSA within the same ESS. Clients with mobile wireless connection can be moved from one BSA to another (within the same ESS) and can be connected without inconvenience.

The rectangular area represents the coverage area within which members of an ESS can communicate. This area is called the “ extended services area ” (ESA). An ESA often involves several BSS in overlapping or separate configurations.

Each ESS is identified by an SSID and, in an ESS, each BSS is identified by its BSSID. For security reasons, additional SSIDs can be propagated through the ESS to segregate the level of network access.