Types of Wireless Network Explained with Standards

A wireless computer network enables people to communicate and access applications and information without wires. This provides freedom of movement and the ability to extend applications to different parts of a building, city, or nearly anywhere in the world. This tutorial explains basic concepts, definitions, types, and terminology of wireless networks.

What is a wireless network?

A wireless network connects computers, laptops, smartphones, tablets, and other internet-enabled devices. Unlike traditional wired networks, which use copper wires, wireless networks use radio signals to connect devices. It allows you to move or relocate end devices without changing the network layout.

Types of Wireless Networks

There are mainly four types of wireless networks: WPANs, WLANs, WMANs, and WWANs.

WPANs (Wireless Personal Area Networks)

It is the smallest wireless network. It includes wireless devices owned by a single user. It uses two technologies to connect devices: Infra Red (IR) and Bluetooth (IEEE 802.15). Bluetooth devices can work in all directions. IR requires a direct line of sight. Bluetooth supports a longer distance. IR supports a shorter distance.

WLANs (Wireless Local Area Networks)

It connects users in a small geographic area, such as a university campus or library. It uses wireless routers and access points to provide a wider coverage area and better connectivity.

WMANs (Wireless Metropolitan Area Networks)

It connects multiple WLANs in a larger area, such as a metropolitan area. It uses antennas and cellular towers.

WWANs (Wireless Wide Area Networks)

It is the largest wireless network. It connects multiple WLANs and WMANs across the countries. It uses complex wireless infrastructure, including satellite systems.

Comparison of Wireless Network Types

Radio Frequency Transmission Factors

Radio frequencies (RF) are generated by antennas that propagate the waves into the air. Antennas fall under two different categories: directional and omnidirectional.

Directional antennas are commonly used in point-to-point configurations (connecting two distant buildings) and sometimes in point-to-multipoint configurations (connecting two WLANs). An example of a directional antenna is a Yagi antenna. It allows you to adjust the signal's direction and focus to increase the range and reach.

Omni-directional antennas are used in point-to-multipoint configurations, where they distribute the wireless signal to other computers or devices in a WLAN. An access point uses an omnidirectional antenna. These antennas can also be used for point-to-point connections, but they lack the distance that directional antennas support.

Three main factors influence signal distortion:

• Absorption objects that absorb the RF waves, such as walls, ceilings, and floors.
• Scattering objects that disperse the RF waves, such as rough plaster on a wall, carpet on the floor, or drop-down ceiling tiles.
• Reflection objects that reflect the RF waves, such as metal and glass.

Responsible body

The International Telecommunication Union-Radio Communication Sector (ITU-R) is responsible for managing the radio frequency (RF) spectrum and satellite orbits for wireless communications. It facilitates cooperation and coexistence of standards and implementations across country boundaries.

Two standards bodies are primarily responsible for implementing WLANs:

• IEEE defines the mechanical processes for implementing WLANs in the 802.11 standards, enabling vendors to create compatible products.
• The Wi-Fi Alliance certifies companies by ensuring that their products comply with the 802.11 standards, allowing customers to buy WLAN products from different vendors without worrying about compatibility issues.

Frequencies bands

WLANs use three unlicensed bands

• 900 MHz is used by older cordless phones.
• 2.4 GHz is used by newer cordless phones, WLANs, Bluetooth, microwaves, and other devices.
• 5 GHz is used by the newest models of cordless phones and WLAN devices.

900 MHz and 2.4 GHz frequencies are referred to as the Industrial, Scientific, and Medical (ISM) bands. Unlicensed bands are still regulated by governments, which may impose restrictions on their use. A hertz (Hz) is a unit of frequency that measures the change in a state or cycle in a wave (sound or radio) or alternating current (electricity) during 1 second.

How an end-user client with a WLAN NIC accesses a LAN

• To help clients find the AP easily, the AP periodically broadcasts beacons that announce its SSID (Service Set Identifier), data rates, and other WLAN information.
• SSID is a naming scheme for WLANs that allows you to group WLAN devices.
• To discover APs, clients scan all channels and listen for the beacons from the AP(s). By default, the client will associate with the AP that has the strongest signal.
• When the client associates with the AP, it sends the SSID, its MAC address, and any other security information the AP may require, depending on the authentication method configured on both devices.
• Once connected, the client periodically monitors the signal strength of the AP it is connected to.
• If the signal strength becomes too low, the client will repeat the scanning process to discover an AP with a stronger signal. This process is commonly called roaming.

SSID and MAC Address Filtering

When implementing SSIDs, the AP and client must use the same SSID value to authenticate. By default, the access point broadcasts its SSID, advertising its presence and allowing anyone to access it. To prevent rogue devices from accessing the AP, you can disable SSID broadcast on the AP. It is called SSID cloaking. To learn the AP's SSID, the client sends a null string in the SSID field of the 802.11 frame.

A rogue device could repeat the process and learn the SSID. Therefore, the APs are commonly configured to filter traffic by MAC address. You can configure a list of MAC addresses in a security table on the AP to allow access to specific devices. However, this solution has the problem that MAC addresses can be seen in the clear on the airwaves. A rogue device can easily sniff the airwaves, see valid MAC addresses, and change its MAC address to match one of them. This is called MAC address spoofing.

WEP

WEP (Wired Equivalent Privacy) was the first security solution for WLANs that employed encryption. It uses a static 64-bit (40-bit) key and a 24-bit initialization vector (IV). IV is sent in clear-text. Since it uses a weak encryption algorithm and sends the IV in clear text, it can be easily broken. To alleviate this problem, the key was extended to 104 bits, including the IV in the updated version. However, either variation can easily be broken in minutes on modern computers.

802.1x EAP

The Extensible Authentication Protocol (EAP) is a layer-2 protocol that enables a wireless client to authenticate to the network. There are two varieties of EAP: one for wireless and one for LAN connections, commonly called EAP over LAN (EAPoL).

One concern in wireless networking is how to allow a WLAN client to communicate with devices behind an AP. Three standards define this process: EAP, 802.1x, and Remote Authentication Dial In User Service (RADIUS). EAP defines a standard way to encapsulate authentication information, such as a username and password or a digital certificate, that the AP can use to authenticate the user. 802.1x and RADIUS define how to encapsulate EAP information for transmission across the network.

WPA

Wi-Fi Protected Access (WPA) was designed by the Wi-Fi Alliance as a temporary security solution to support 802.1x and enhancements to WEP until the 802.11i standard was ratified. WPA can operate in two modes: personal and enterprise mode.

Personal mode was designed for home or SOHO usage. A pre-shared key is used for authentication, requiring you to configure the same key on the clients and the AP. In this mode, no authentication server is required, unlike the official 802.1x standards. Enterprise mode is intended for large companies, where an authentication server centralizes clients' authentication credentials.

WPA2

WPA2 is the IEEE 802.11i implementation from the Wi-Fi Alliance. Instead of using WEP, which uses the weak RC4 encryption algorithm, the much more secure Advanced Encryption Standard (AES)–counter mode CBC-MAC Protocol (CCMP) algorithm is used.

IR (Infrared radiation)

It is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of microwave radiation. The name means "below red" (from the Latin infra, "below"), red being the color of visible light of longest wavelength.

Bluetooth

It is an industrial specification for wireless personal area networks (PANs). Bluetooth provides a way to connect and exchange information between devices like personal digital assistants (PDAs), mobile phones, laptops, PCs, printers, and digital cameras via a secure, low-cost, globally available short-range radio frequency.

FHSS (Frequency-hopping)

It is a method of transmitting radio signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver. Spread-spectrum transmission offers these advantages over a fixed-frequency transmission:

• Highly resistant to noise and interference.
• Signals are difficult to intercept. A Frequency-Hop spread-spectrum signal sounds like a momentary noise burst or simply an increase in the background noise for short Frequency-Hop codes on any narrowband receiver except a Frequency-Hop spread-spectrum receiver using the exact same channel sequence as was used by the transmitter.
• Transmissions can share a frequency band with many types of conventional transmissions with minimal interference. As a result, bandwidth can be utilized more efficiently.

DSSS (Direct-sequence spread spectrum)

It is a modulation technique in which the transmitted signal occupies a bandwidth wider than the information signal. For the same reason, it is called spread spectrum. It uses a single channel to transmit data across all frequencies within it.

Complementary Code Keying (CCK) is a method for encoding transmissions at higher data rates, such as 5.5 and 11 Mbps, while still allowing backward compatibility with the original 802.11 standard, which supports only 1 and 2 Mbps. 802.11b and 802.11g support this transmission method.

OFDM

Orthogonal frequency-division multiplexing, also called discrete multitone modulation (DMT), is a transmission technique based on frequency-division multiplexing (FDM). OFDM (Orthogonal Frequency Division Multiplexing) increases data rates by using spread-spectrum modulation. 802.11a and 802.11g support this transmission method.

IEEE 802.11a / IEEE 802.11h

This is also a physical layer enhancement. IEEE 802.11a provides significantly higher performance than 802.11b, with a maximum of 54 Mbps. Unlike 802.11b, the 802.11a standard operates in the 5.47-5.725 GHz frequency range and is not subject to the same interference from other commercial electronic products. This higher-frequency band enables significantly higher communication speeds in the 2.4 GHz range.

802.11g APs are backward compatible with 802.11b APs. This backward compatibility with 802.11b is handled through the MAC layer, not the physical layer. On the negative side, because 802.11g operates at the same frequency as 802.11b, it is subject to the same interferences from electronic devices such as cordless phones. Since the standard’s approval in June 2003, 802.11g products have been gaining momentum and will most likely become as widespread as 802.11b products. Table II-1 displays basic 802.11b/a/g characteristics.

The typical range of operation for 802.11b is 150 feet in a floor divided into individual offices by concrete or sheet rock, about 300 feet in semi-open indoor spaces such as offices partitioned into individual workspaces, and about 1000 feet in large open indoor areas. Disadvantages of 802.11b include interference from electronic products such as cordless phones and microwave ovens.

Conclusion

Wireless networking has transformed how you connect, communicate, and share information. By offering flexibility, mobility, and convenience, wireless networks have become an essential part of modern networking. Understanding the types of wireless networks, their standards, and key technologies enables you to make informed decisions about setup, security, and usage.