Wireless LAN

This article explains the theoretical aspects of WLAN technology. It covers fundamental concepts such as radio frequency behavior and Wi-Fi standards.

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Introduction

Standards Organizations

802.11 Standards

Radio Frequencies

Collision Detection

Electromagnetic Spectrum

Introduction

WLAN stands for Wireless Local Area Network. It refers to a type of wireless network that allows devices within a specific area to connect and communicate with each other wirelessly. A WLAN is commonly used to provide local network connectivity in homes, offices, schools, airports, cafes, and other public or private spaces. Key aspects of a WLAN include:

Description

Wireless Access Points (APs): These devices serve as the central connection point for wireless devices. APs transmit and receive data between the wireless devices and the wired network infrastructure. They typically connect to a wired network through Ethernet cables and provide wireless coverage within a specific area, known as a hotspot or coverage zone.

Wi-Fi Technology: Wi-Fi (Wireless Fidelity) is the most common technology used in WLANs. It is based on the IEEE 802.11 standards. These standards define the specifications for wireless communication, including data transfer rates, frequency bands, and modulation techniques.

Wireless Devices: Devices that support Wi-Fi, such as laptops, smartphones, tablets, IoT devices, and Wi-Fi-enabled printers, can connect to a WLAN. These devices have built-in wireless network interfaces (Wi-Fi adapters) that allow them to send and receive data over the wireless network.

SSID and Security: WLANs are typically secured using security protocols like WPA2 (Wi-Fi Protected Access II) or WPA3. When connecting to a WLAN, users need to provide the correct network name, known as the Service Set Identifier (SSID), and possibly a password or other authentication credentials.

Advantages of WLANs include:

Description

Mobility: WLANs provide the freedom to connect and access network resources without the constraints of physical cables, enabling users to move around within the coverage area while maintaining network connectivity.

Convenience and flexibility: WLANs eliminate the need for wired connections, making it easier to set up and expand network infrastructure. Devices can be connected to the network without the hassle of physical cables, allowing for more flexibility in device placement.

Scalability: WLANs can be easily expanded by adding more access points to accommodate a growing number of devices or to extend the coverage area.

Broad connectivity: WLANs enable devices to connect to the Internet and other network resources, facilitating seamless communication, data sharing, and access to online services.

It’s worth noting that WLANs have certain limitations, including limited range compared to wired networks, susceptibility to signal interference, and potential security vulnerabilities. However, continuous advancements in Wi-Fi technology and security measures aim to address these challenges and enhance the performance and reliability of WLANs.

Standards Organizations

There are three main organizations that establish standards in the wireless networking industry:

Description

IEEE - The Institute of Electrical and Electronics Engineers is a globally recognized professional organization dedicated to advancing technology and innovation in various fields, with a primary focus on electrical engineering, electronics, computer science, telecommunications, and related disciplines. It is a non-profit organization that brings together professionals, researchers, academics, and students from around the world. The 802.11 group was responsible for creating a WLAN standard.

IETF - The Internet Engineering Task Force is an open international community of network designers, operators, vendors, and researchers. It operates as a decentralized organization that focuses on developing and promoting Internet standards and protocols. The IETF is responsible for defining and refining various protocols and technologies that enable the functioning and growth of the Internet.

The Wi-Fi Alliance, situated in Austin, Texas, is a non-profit organization responsible for the ownership of the Wi-Fi trademark. Manufacturers have the opportunity to utilize this trademark to label their products that have been certified for Wi-Fi interoperability.

802.11 Standards

802.11 is a set of standards developed by the Institute of Electrical and Electronics Engineers (IEEE) for wireless local area networks (WLANs). The 802.11 standards define the specifications for wireless communication, including data transfer rates, frequency bands, modulation techniques, and other aspects of wireless networking.

Standard

802.11

802.11a

802.11b

802.11g

802.11n

802.11ac

802.11ax

GHz

2.4 GHz

5.0 GHz

2.4 GHz

2.4 & 5.0 GHz

5.0 GHz

2.4, 5.0 & 6 GHz

Mbps

1-2 Mbps

6-54 Mbps

1-11 Mbps

6-54 Mbps

72-600 Mbps

433-6933 Mbps

600-9607 Mbps

Year

1997

1999

2003

2009

2014

2020

Description

FHSS+GFSK / DSSS+DBPSK/DQPSK

DSSS+CCK

OFDM+BPSK/QPSK/QAM

MIMO (channel aggregation, multiple antennas)

Enhanced MIMO (channel bandwith extended from 40 to 80 MHz)

8x8 MU-MIMO, OFDMA, TWT

The table below explains the different technologies that were developed with the different 802.11 standards.

Description

FHSS (Frequency-Hopping Spread Spectrum) is a wireless communication technique where the transmitter and receiver rapidly change frequencies in a synchronized manner to increase robustness against interference and enhance security.

GFSK (Gaussian Frequency-Shift Keying) is a digital modulation technique that uses a Gaussian filter to minimize signal interference and achieve efficient data transmission in wireless communication systems.

DSSS (Direct Sequence Spread Spectrum) is a digital modulation technique that spreads the data signal across a wide range of frequencies using a spreading code, providing increased robustness against interference and improving data integrity in wireless communication systems.

DBPSK (Differential Binary Phase Shift Keying) is a digital modulation scheme where the phase shift of the carrier signal is used to represent binary data, making it less susceptible to phase shifts caused by channel impairments in wireless communication systems.

DQPSK (Differential Quadrature Phase Shift Keying) is a digital modulation scheme where the phase shift of the carrier signal is used to represent two bits of data at a time, increasing data transmission efficiency and resilience to phase shifts in wireless communication systems.

OFDM (Orthogonal Frequency Division Multiplexing) is a digital modulation technique that divides a high data rate signal into multiple low data rate subcarriers, allowing for efficient and robust transmission in wireless communication systems.

QAM (Quadrature Amplitude Modulation) is a digital modulation scheme that simultaneously varies both the amplitude and phase of the carrier signal to encode multiple bits of data per symbol, enabling higher data rates and spectral efficiency in wireless communication systems.

MIMO (Multiple-Input Multiple-Output) is a wireless communication technology that uses multiple antennas for both transmitting and receiving data, increasing data throughput, improving signal quality, and enhancing overall system performance.

MU-MIMO (Multi-User Multiple-Input Multiple-Output) is a wireless communication technology that allows a Wi-Fi access point to simultaneously communicate with multiple client devices using multiple spatial streams, improving efficiency and increasing overall network capacity.

OFDMA (Orthogonal Frequency Division Multiple Access) is a wireless communication technique that divides a channel into multiple orthogonal subcarriers, enabling multiple users to transmit and receive data concurrently, thus improving spectral efficiency and increasing the overall capacity of the network.

TWT (Traveling Wave Tube) is an electronic device that amplifies high-frequency signals by converting electrical energy into a traveling wave, commonly used in satellite communication, radar systems, and high-power microwave applications.

Radio Frequencies

Radio frequency (RF) refers to the range of electromagnetic frequencies within the electromagnetic spectrum that are commonly used for wireless communication and broadcasting. It encompasses frequencies ranging from a few kilohertz (kHz) to hundreds of gigahertz (GHz). 2.4 GHz & 5 GHz are commonly used for wireless communication, including Wi-Fi networks. A RF signal works as the medium to carry data, therefore RF signals are in the physical layer of the OSI model.

Description

Frequency Range: The 2.4 GHz band operates in the frequency range between 2,400 & 2,483.5 megahertz (MHz), while the 5.0 GHz band operates in the frequency range between 5,150 & 5,825 MHz. The 5.0 GHz band has a higher frequency than the 2.4 GHz band.

Channel Availability: The 2.4 GHz band has a larger number of available channels for wireless communication compared to the 5.0 GHz band. However, due to the larger number of devices using the 2.4 GHz band (including other Wi-Fi networks, Bluetooth devices, cordless phones, and microwaves), it can be more congested and prone to interference.

Signal Penetration and Range: Signals in the 2.4 GHz band generally have better penetration through walls, floors, and other obstacles compared to signals in the 5.0 GHz band. This means that Wi-Fi signals in the 2.4 GHz band can travel further and provide better coverage in larger areas. However, due to interference and congestion, the actual range and performance of 2.4 GHz networks can vary in different environments.

Data Transfer Rates: The 5.0 GHz band typically offers higher data transfer rates compared to the 2.4 GHz band. It provides a wider channel bandwidth and can support faster Wi-Fi standards, such as 802.11ac (Wi-Fi 5) & 802.11ax (Wi-Fi 6). The higher frequency and wider bandwidth allow for greater capacity and faster data transmission, making it suitable for applications that require high bandwidth, such as streaming high-definition videos or online gaming.

Device Compatibility: Most modern Wi-Fi devices are dual-band, meaning they can operate on both 2.4 GHz & 5.0 GHz bands. However, older Wi-Fi devices, particularly those that support only older Wi-Fi standards like 802.11b/g, may be limited to the 2.4 GHz band. Additionally, certain specialized devices, such as some IoT devices, may only support the 2.4 GHz band.

Interference and Congestion: The 2.4 GHz band is more susceptible to interference from other devices operating in the same frequency range, including Wi-Fi networks and non-Wi-Fi devices. The 5.0 GHz band, being less crowded, generally experiences less interference and can provide a more reliable and higher-performing network in environments with multiple Wi-Fi networks.

For wired networks cables are the physical medium. A RF signal works as the medium to carry data through the air, therefore RF signals are in the physical layer of the OSI model.

OSI Model

7 - Application Layer

6 - Presentation Layer

5 - Session Layer

4 - Transport Layer

3 - Network Layer

2 - Data Link Layer

1 - Physical Layer

The image below shows the 2.4 GHz band:

Each channel is 22 MHz wide. The non-overlapping channels in the 2.4 Ghz signal spektrum are 1, 6 & 11.

The tabe below shows the main differences between 2.4 & 5.0 GHz.

The image below shows the 5.0 GHz band:

The 5.0GHz signal spectrum has no overlapping channels, therefore, making it easier to avoid interference.

Radio Frequencies can naturally encounter different behaviours:

Description

Absorption: Absorption refers to the process in which electromagnetic waves are absorbed by a material or medium they encounter. When waves encounter a material that absorbs their energy, a portion of the wave's energy is converted into other forms, such as heat. The absorbed energy reduces the intensity or strength of the wave as it passes through the material.

Reflection: Reflection occurs when electromagnetic waves encounter a surface or boundary and bounce back instead of being absorbed or transmitted through it. The angle of incidence (the angle at which the wave strikes the surface) is equal to the angle of reflection (the angle at which the wave bounces off). Reflection plays a crucial role in various applications, such as radar systems, where the reflection of waves from objects helps in detection and ranging.

Scattering: Scattering refers to the phenomenon in which electromagnetic waves encounter small particles or irregularities in a medium and change their direction. The waves get scattered in different directions due to interactions with the particles, resulting in a distribution of energy. Scattering is responsible for phenomena such as the blue color of the sky, where sunlight is scattered by molecules and small particles in the atmosphere.

Refraction: Refraction occurs when electromagnetic waves pass through a medium with varying densities, causing a change in their direction. The change in direction is due to the change in the wave's speed as it transitions from one medium to another. The bending of light as it passes through a prism or the apparent bending of a straw in a glass of water are examples of refraction.

Diffraction: Diffraction is the bending or spreading out of waves as they encounter obstacles or pass through small openings. It occurs when waves encounter an obstacle or aperture that is comparable in size to their wavelength. Diffraction causes the waves to bend around the obstacle or spread out after passing through the opening, resulting in the phenomenon of wave interference and the creation of wave patterns.

Attenuation: Attenuation refers to the decrease in the strength or intensity of electromagnetic waves as they propagate through a medium or travel over a distance. Attenuation can occur due to various factors, including absorption, scattering, and other forms of energy loss. It results in a reduction in the power or amplitude of the wave.

Free Space Path Loss: Free Space Path Loss (FSPL) is the loss of signal power that occurs as electromagnetic waves propagate through free space without any obstacles or interference. FSPL increases with the distance between the transmitter and receiver and is influenced by the frequency of the wave. It is an important factor to consider in wireless communication system design, as it determines the maximum range and coverage of the system.

Multipath: Multipath refers to the phenomenon where electromagnetic waves travel through multiple paths to reach a receiver due to reflections, diffractions, and scattering from various objects or surfaces in the environment. These multiple paths result in multiple versions of the same signal arriving at the receiver with slight delays and different phases. Multipath interference can cause signal fading, distortion, and reduced signal quality in wireless communication systems.

Gain: Gain refers to the amplification or increase in the strength or power of an electromagnetic wave. It is commonly used to describe the directional properties and performance of antennas. Antenna gain indicates how effectively an antenna can concentrate the radiated power in a particular direction, allowing for improved signal reception or transmission in that direction.

Collision Detection

Collision detection in wireless networks is a process that involves sensing and identifying when multiple devices attempt to transmit data simultaneously on the same wireless channel, resulting in a collision of signals. In wireless communication, collisions occur due to the shared nature of the wireless medium, where multiple devices contend for access to the channel. CSMA/CD (Carrier Sense Multiple Access with Collision Detection) and CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) are two different protocols used in network communication to manage how devices access the network medium.

Description

CSMA/CD is a protocol used in Ethernet networks. In CSMA/CD, before a device starts transmitting data, it first senses the network medium (carrier sense) to check if it is busy with other transmissions. If the medium is idle, the device starts transmitting. However, if another device starts transmitting at the same time, a collision occurs. When a collision is detected during transmission, the devices stop sending data and enter a backoff period before attempting to retransmit. CSMA/CD is primarily used in traditional wired Ethernet networks, and its efficiency decreases as network size and collision probability increase.

CSMA/CA is a protocol used in wireless networks, such as Wi-Fi. In CSMA/CA, the carrier sensing mechanism works similarly to CSMA/CD, where devices sense the wireless medium before transmitting data. However, in CSMA/CA, the "Collision Avoidance" aspect comes into play to minimize the chances of collisions. When a device intends to transmit, it first sends a small request to send (RTS) packet to the access point (AP) or another device, indicating its intention to transmit. The receiving device responds with a clear to send (CTS) packet, reserving the channel for the intended transmission. During this process, other devices in the vicinity defer their transmissions, reducing the likelihood of collisions. CSMA/CA is designed to address the unique challenges of wireless networks, including signal interference and hidden node problems, making it more suitable for shared wireless medium environments.

WLANs operate in a half-duplex mode, which means that devices connected to the network can either transmit or receive data at any given time, but not both simultaneously. This is in contrast to full-duplex communication, where devices can both transmit and receive data simultaneously.

Electromagnetic Spectrum

The electromagnetic spectrum refers to the range of all possible electromagnetic waves, which are forms of energy that propagate through space in the form of oscillating electric and magnetic fields. It encompasses a wide range of frequencies and wavelengths, from low-frequency waves with long wavelengths to high-frequency waves with short wavelengths.

The electromagnetic spectrum encompasses a vast range of frequencies and wavelengths. At one end, it includes extremely low-frequency (ELF) waves and radio waves with long wavelengths and low frequencies. In the middle, it encompasses microwaves, infrared radiation, visible light (which is the narrow portion visible to the human eye), ultraviolet radiation, X-rays, and at the highest frequencies, gamma rays with short wavelengths and high frequencies.

Wavelength

A wavelength refers to the distance between two consecutive points in a wave that exhibit the same phase and pattern. In a wave, there are specific points known as peaks and valleys that are relevant to understanding the concept of wavelength.

Description

Wavelength: Wavelength is the spatial length over which a wave completes one full cycle of its oscillation. It is typically denoted by the Greek letter lambda (λ). Wavelength is measured as the distance between two identical points in a wave, such as two consecutive peaks or two consecutive valleys. It is usually expressed in meters (m) or other units such as nanometers (nm) or micrometers (µm) depending on the scale of the wave.

Peaks: Peaks, also known as crests or maxima, are the highest points of a wave. They represent the positions where the amplitude of the wave reaches its maximum positive value. Peaks occur at regular intervals along the wave, and the distance between two consecutive peaks corresponds to the wavelength of the wave.

Valleys: Valleys, also known as troughs or minima, are the lowest points of a wave. They represent the positions where the amplitude of the wave reaches its maximum negative value. Similar to peaks, valleys occur at regular intervals along the wave, and the distance between two consecutive valleys is also equal to the wavelength.

Relationship to Amplitude: Amplitude refers to the maximum displacement or magnitude of the wave from its equilibrium position. It represents the intensity or strength of the wave. In a wave, the peaks and valleys are the points of maximum positive and negative amplitudes, respectively. The amplitude of a wave is not directly related to its wavelength but rather represents the extent of the wave's oscillation.

Visualizing Wavelength, Peaks, and Valleys: In a graphical representation of a wave, the wavelength can be measured by determining the distance between two consecutive peaks or two consecutive valleys. The distance between a peak and a valley is half of the wavelength.

1 Hz refers to a frequency of one cycle per second. The unit “Hz” stands for hertz, which is the standard unit of frequency in the International System of Units (SI). Therefore, a cycle that occurs 500 times in a second is measured as 500 Hz.

Decibel

The decibel (dB) is a logarithmic unit used to express the relative intensity or power of a signal, sound, or measurement. It is widely used in various fields, including acoustics, telecommunications, electronics, and physics. Here are some key points about the decibel:

Description

Relative Measurement: The decibel is a relative unit of measurement that compares the value of a quantity to a reference level. It quantifies the ratio between two values rather than giving an absolute measurement. The reference level can vary depending on the specific application or context.

Logarithmic Scale: The decibel scale is logarithmic, which means that the difference between two values is expressed as a logarithm rather than a linear difference. It provides a convenient way to represent and compare a wide range of values, spanning from very small to very large quantities, on a compact scale.

Signal Power and Gain: In the context of power or signal strength, the decibel is often used to express the relative power gain or loss between two signals. When expressing power ratios, the decibel is calculated using the formula dB = 10 × log10 (P/Pref), where P is the power being measured, and Pref is the reference power. A positive decibel value represents a power gain, while a negative decibel value represents a power loss.

Sound Level: In acoustics and sound engineering, the decibel is used to measure and compare sound levels. The sound pressure level (SPL) in decibels is based on a reference sound pressure of 20 micropascals (μPa), which is considered the threshold of human hearing. The decibel scale allows for the representation of a wide range of sound intensities, from the faintest audible sounds to extremely loud noises.

Logarithmic Nature: The logarithmic nature of the decibel scale has practical implications. For example, an increase of 10 dB corresponds roughly to a doubling of power, while a decrease of 10 dB corresponds to a halving of power. This logarithmic scale enables the representation of large dynamic ranges and facilitates precise measurement and comparison of values.

Application in Telecommunications: In telecommunications, the decibel is used to measure signal strength, attenuation, and gain in various components and systems, such as antennas, amplifiers, and transmission lines. It provides a way to quantify and describe the characteristics of signals and equipment in a standardized manner.

The received signal strength of both PCs differs by 10 decibels:

Decibel is used to measure the difference in power values. 3 dB doubles the strength of a reference signal, 10 dB multiply the strength of a reference signal by ten.

Decibel

+3 dB

-3 dB

+10 dB

-10 dB

Value

/ 2

x10

/ 10

30 mW

60 mW

15 mW

300 mW

3 mW

RSSI

RSSI stands for Received Signal Strength Indicator. It is a measurement used in wireless networks to quantify the strength of a received radio signal. RSSI indicates the power level of the signal that a device, such as a smartphone, laptop, or wireless access point, receives from another device, typically a wireless router or access point.

Description

Measurement Unit: RSSI is usually measured in decibels (dBm). The value can be negative or positive, with more negative values indicating weaker signals and more positive values indicating stronger signals.

Signal Strength: RSSI provides an indication of how strong the radio signal is at the receiving device. Stronger signals generally result in better connectivity and data transmission.

Variability: RSSI can be influenced by various factors such as distance from the transmitter, obstacles, interference, and environmental conditions. As a result, RSSI readings may fluctuate even if a device is stationary.

Relative Metric: While RSSI is a useful metric for assessing signal strength, it may not directly correlate with other performance metrics like data throughput or signal quality.

Signal-to-Noise Ratio: In addition to RSSI, the Signal-to-Noise Ratio (SNR) is also considered. SNR measures the ratio of the received signal's strength to background noise or interference, providing a more comprehensive understanding of the quality of the received signal.

Use in Network Management: RSSI values are used by wireless devices and access points to make decisions about signal handoff, connection quality, and transmission power adjustments.

Wireless Topologies

Wireless networks can be designed in various different topologies:

Description

Basic Service Set (BSS) is the fundamental building block of a wireless network based on the IEEE 802.11 standard, commonly known as Wi-Fi. It consists of a single access point (AP) and the wireless devices that are associated with that AP. In a BSS, the AP acts as the central point for connecting wireless devices and providing network access. It operates on a specific channel within the wireless spectrum and has a unique Service Set Identifier (SSID) to differentiate it from other BSSs.

Extended Service Set (ESS) is formed when multiple BSSs are interconnected to provide a larger coverage area and seamless roaming for wireless devices. In an ESS, multiple APs are connected through a wired network, allowing devices to move between different APs while maintaining network connectivity. The APs within an ESS have the same SSID, enabling devices to seamlessly transition from one AP to another without interruption.

Extended Basic Service Set (EBSS) is similar to an ESS but with a key difference. In an EBSS, multiple BSSs are interconnected wirelessly rather than through a wired network. This wireless interconnection can be established using wireless distribution system (WDS) technology. EBSS allows for the extension of the network coverage area without the need for additional wired infrastructure, making it useful in scenarios where running cables is impractical or impossible.

Mesh Basic Service Set (MBSS) is a type of wireless network configuration in which multiple wireless devices, known as mesh nodes, form a self-configuring and self-healing network. Each mesh node acts as both a client and an access point, relaying data between devices and extending network coverage. This enables devices to communicate directly with each other, creating multiple communication paths and increasing network resilience. MBSS is particularly useful in scenarios where traditional infrastructure-based networks are not feasible or when robust network coverage and flexibility are required.

Independent Basic Service Set (IBSS) is a mode of operation in wireless networks based on the IEEE 802.11 standard, commonly known as Wi-Fi. In an IBSS, also referred to as an ad-hoc network or peer-to-peer network, wireless devices communicate directly with each other without the need for a central access point (AP).

AP Modes

Different Access Point modes offer specific functionalities and applications, enabling versatile wireless network configurations to suit different use cases and requirements. The list below shows the common modes for WLAN APs.

Description

Access Mode: In Access Point (AP) mode, the wireless device acts as a central hub for connecting wireless clients, such as laptops, smartphones, and IoT devices, to a wired network. It enables wireless devices to access resources and services, like internet connectivity or shared files, provided by the wired network.

Bridge Mode: In Bridge mode, the wireless device connects two separate wired networks (LANs) wirelessly, effectively creating a bridge between them. It allows devices on both networks to communicate with each other seamlessly, extending the network coverage and facilitating interconnection.

Workgroup Bridge Mode: Workgroup Bridge mode enables a wireless device to connect to a wireless network as a client while simultaneously allowing wired devices connected to its Ethernet port to access the wireless network. This mode is suitable for devices that do not have built-in wireless capabilities but need to connect to a wireless network.

Repeater Mode: In Repeater mode, the wireless device receives and retransmits the wireless signal it receives, effectively extending the wireless coverage range. It can be placed between the primary AP and the wireless clients, boosting the signal strength and improving the overall coverage of the network.

Mesh Mode: Mesh mode is a wireless networking technique in which multiple APs are interconnected to form a self-configuring and self-healing network. Each AP acts as a node and communicates with neighboring nodes, providing multiple paths for data transmission and improving network resilience. Mesh networks are particularly useful in scenarios where wired infrastructure is not feasible or in large-scale deployments.

Scanner Mode: In Scanner mode, the wireless device operates as a passive scanner, continuously monitoring the wireless channels and gathering information about nearby wireless networks. It is commonly used for site surveys, network planning, and troubleshooting, providing valuable insights into the wireless environment.

Antennas

Antennas are used to transmit the signal into the air, and the signal must be radiated with sufficient power to be received by receivers. There are different types of antennas and installations that are used in different use cases.

Description

Transmitting and Receiving: Antennas can act as transmitters or receivers. When used as a transmitter, an electrical signal is fed into the antenna, and it converts the electrical energy into electromagnetic waves that propagate through the air. As a receiver, the antenna captures incoming electromagnetic waves and converts them back into electrical signals for further processing.

Radiation Pattern: The radiation pattern of an antenna describes the directional distribution of the electromagnetic energy it emits or receives. Different antennas have various radiation patterns, such as omni-directional (radiating or receiving energy in all directions) or directional (focusing energy in specific directions). The choice of radiation pattern depends on the application and desired coverage area.

Frequency Band: Antennas are designed to operate within specific frequency bands. The size and design of an antenna depend on the frequency range it is intended to work with. Different antennas are used for various frequency ranges, such as the 2.4 GHz & 5 GHz bands in Wi-Fi or specific frequency bands in cellular communication.

Gain: Antenna gain refers to the ability of an antenna to focus or concentrate the electromagnetic energy in a particular direction. It is a measure of how effectively the antenna radiates or receives energy in a specific direction compared to an isotropic radiator (an ideal theoretical point source radiating energy equally in all directions).

Polarization: Antennas have specific polarization characteristics, which refer to the orientation of the electric field in the electromagnetic waves. Common polarizations include vertical, horizontal, circular, and elliptical polarization. To ensure proper communication, the transmitting and receiving antennas should have matching polarization.

Diversity: In some applications, multiple antennas are used to improve system performance through diversity. Diversity techniques involve the use of multiple antennas to mitigate signal fading, interference, and improve overall reliability in wireless communication.

Types of Antennas: There are various types of antennas, each designed for specific applications. Some common types include dipole antennas, monopole antennas, Yagi antennas, patch antennas, helical antennas, and parabolic antennas. The choice of antenna type depends on factors such as frequency, coverage requirements, and form factor.

The two main categories of antennas are "omnidirectional", and "directional". The image above shows the signal of an omnidirectional antenna from the top and from the side. The table below shows different Cisco WLAN access points using different types of antennas. Modern access points feature multiple antennas for a technology known as Multiple-Input Multiple-Output (MIMO), which significantly enhances wireless network performance and reliability. MIMO takes advantage of the spatial dimension to improve data throughput, increase network coverage, and mitigate signal interference.

Omnidirectional

AIR-AP2802E with omnidirectional antennas

Semi-directional

AIR-AP2602E with an external patch antenna

Directional

AIR-AP1562I with an internal unidirectional antenna

The images below show how the signal spreads when using different types of antennas. Antenna strength is measured as a reference to an isotropic rediator. dBi is a measurement of gain as compared to an isotropic radiator measured at the strongest point (focal point) of the signal.

Radiation Patterns

H-plane (Horizontal Plane) and E-plane (Vertical Plane) are terms used in the context of antenna radiation patterns to describe the two principal planes in which the antenna's electromagnetic energy is distributed.

Description

The H-plane is the horizontal plane perpendicular to the axis of the antenna. In this plane, the radiation pattern represents the distribution of energy in the horizontal direction. It is also referred to as the azimuth plane. The H-plane typically includes the angles of azimuth or azimuthal angles, which measure the angle of radiation around the horizontal axis.

The E-plane is the vertical plane that contains the antenna's axis. It is perpendicular to the H-plane and is also known as the elevation plane. In the E-plane, the radiation pattern represents the distribution of energy in the vertical direction.

The image below shows the radiation pattern of a patch antenna form the vertical, and the horizontal view point. The antenna could be classified as an semi-directional antenna because of the broad signal pattern. These charts contain no information about distance, only the shape of the signal.

The H-Plane describes the signal pattern viewed from the top, and the E-Plane describes the signal pattern viewed from the side while the antenna is placed in the middle of the radiation circle.

SSID

SSID stands for Service Set Identifier. It is a unique name assigned to a wireless network to identify and differentiate it from other nearby networks in the same vicinity. The SSID is used to help devices, such as laptops, smartphones, and other Wi-Fi-enabled devices, identify and connect to the correct network.

Description

Network Identification: When you search for available Wi-Fi networks on your device, you see a list of SSIDs representing different networks. This allows users to choose the network they want to connect to.

Broadcasting: Most wireless routers and access points broadcast their SSIDs so that nearby devices can discover and display them in the list of available networks. However, SSID broadcasting can be disabled for added security, making the network "hidden." Hidden networks require users to manually enter the SSID when connecting.

Case Sensitivity: SSIDs are case-sensitive, meaning that "MyNetwork" and "mynetwork" are considered different SSIDs by devices.

Privacy and Security: While SSIDs help identify networks, they are not a secure form of authentication. Network security relies on other mechanisms, such as encryption methods and authentication protocols (e.g., WPA2, WPA3).

Default SSIDs: Many routers come with a default SSID provided by the manufacturer. Changing the default SSID to something unique helps improve network security by making it more challenging for potential attackers to guess the network's identity.

Network Management: In larger environments, multiple access points may be deployed to cover a broader area. These access points may use the same SSID, allowing devices to roam seamlessly between them without repeatedly reconnecting.

Length and Character Limitations: SSIDs can vary in length and characters, but they are typically limited to a specific number of characters (32 or 64 characters, for example) to ensure compatibility with devices.

Roaming

Roaming in the context of wireless networking refers to the ability of a mobile device, such as a smartphone, laptop, or tablet, to seamlessly switch its connection from one wireless access point (AP) to another while maintaining an ongoing network session. This is particularly important in environments with multiple access points, such as a large office building, airport, or campus, where a single AP's coverage might not extend throughout the entire area.

Description

Continuous Connectivity: Roaming allows a device to stay connected to the network and maintain communication, even when moving between different coverage areas served by different access points. This is crucial for tasks like voice calls, video streaming, online gaming, and data transfer.

Handoff: When a device roams, it initiates a process known as a handoff or handover. This involves the device disassociating from the current access point and associating with a new one. The handoff process aims to ensure a seamless transition without interrupting the ongoing network activities.

Signal Strength and Quality: Roaming decisions are often based on the signal strength and quality of the available access points. Devices typically look for access points with a stronger signal to ensure stable and efficient communication.

AP Overlapping Coverage: In environments with overlapping coverage areas of different access points, devices might choose to switch to an access point that offers better signal quality or lower congestion.

Fast Roaming Protocols: To minimize the interruption during handoff, fast roaming protocols like 802.11r (Fast BSS Transition) & 802.11k (Radio Resource Measurement) are used. These protocols optimize the handoff process by pre-authenticating devices with neighboring access points and providing accurate information about nearby access points.

Network Load Balancing: Roaming can also be used for load balancing purposes, where devices are directed to connect to less congested access points to distribute the network traffic evenly.

Roaming Aggressiveness: Devices can have different roaming aggressiveness settings, which determine how quickly they switch to a new access point. Higher roaming aggressiveness might lead to faster handoffs but could also result in unnecessary switches.

Smoother User Experience: Roaming ensures that users can move around within a wireless network environment without experiencing noticeable disruptions in their network connections. This is especially important for applications that require a continuous and stable connection.

Power over Ethernet

POE stands for Power over Ethernet. It is a technology that allows electrical power to be transmitted along with data over Ethernet cables, typically used to connect network devices such as wireless access points, IP cameras, and VoIP phones to a network. This eliminates the need for separate power cables, simplifying installations and improving flexibility.

Description

Single Cable Solution: With POE, both data and power are delivered over a single Ethernet cable, reducing clutter and the need for multiple cables at the installation site.

Standardized: POE operates based on standardized protocols like IEEE 802.3af, IEEE 802.3at (also known as POE+), and IEEE 802.3bt (POE++) to ensure compatibility between devices from different manufacturers.

PSE and PD: In a POE setup, there are two main components: the Power Sourcing Equipment (PSE) and the Powered Device (PD). The PSE provides the power, typically located in a switch or injector, while the PD consumes the power, such as an IP camera or wireless access point.

Power Levels: POE+ and POE++ support higher power levels compared to the original POE standard. POE+ can deliver up to 30W of power per port, while POE++ can deliver up to 60W or even 100W of power per port.

Auto-Negotiation: POE-enabled devices perform auto-negotiation to determine whether the connected equipment supports POE. If both devices are compatible, the necessary power is supplied over the Ethernet cable.

Voltage and Current: POE operates with different voltage levels and current ratings depending on the specific standard and power level. Devices must support the required voltage and current to function properly.

Distance Considerations: The maximum distance over which POE can reliably transmit power depends on the cable type and power level. Cat5e and Cat6 cables are commonly used for POE installations.

Use Cases: POE is widely used in scenarios where electrical outlets are scarce or not conveniently located, such as mounting wireless access points on ceilings or installing IP cameras in outdoor locations.

Reduced Installation Costs: POE simplifies installation, reduces labor costs, and avoids the need for hiring electricians to install additional power outlets.

Remote Management: Some POE-enabled devices can be remotely powered down or restarted, which can be useful for maintenance and troubleshooting.

The image below shows a POE network switch:

WLAN Controller

A Wireless LAN (WLAN) Controller is a central device used to manage and control a network of wireless access points (APs) in an enterprise or larger-scale wireless network deployment. It serves as a centralized point of control for configuring, monitoring, and managing various aspects of the wireless network infrastructure. Key functions and features of a WLAN Controller:

Description

Centralized Management: The WLAN Controller provides a single interface through which network administrators can manage multiple APs across different locations. This centralized management simplifies tasks such as configuration, firmware updates, and security settings.

Configuration and Provisioning: Administrators can configure network settings, such as SSIDs, security protocols, Quality of Service (QoS) policies, and more, on the WLAN Controller. These settings are then pushed out to all associated APs, ensuring consistent network configuration.

Security and Authentication: WLAN Controllers facilitate the implementation of security measures, such as encryption protocols (WPA2, WPA3), user authentication (802.1X, PSK, EAP), and guest network access controls. Security policies can be applied uniformly to all APs.

Load Balancing and Roaming: WLAN Controllers manage client distribution across APs to balance network traffic and prevent overloading of individual APs. They also help facilitate seamless roaming by coordinating the handoff of client devices between APs as users move within the network.

Radio Resource Management: Controllers can optimize radio frequency (RF) settings by adjusting channel selection, power levels, and interference mitigation techniques. This helps improve overall network performance and reliability.

Monitoring and Analytics: WLAN Controllers gather real-time data from APs, allowing administrators to monitor network health, performance metrics, and user behavior. Analytics can aid in diagnosing issues and planning network expansions.

Guest Access and Captive Portals: Many WLAN Controllers offer guest network features, including captive portals for guest authentication, customizable splash pages, and bandwidth controls.

Scalability: WLAN Controllers are designed to scale with growing network demands. As the network expands, administrators can add more APs while still managing them from a single controller.

Redundancy and High Availability: To ensure network uptime, some WLAN Controllers support redundancy and failover mechanisms. If one controller fails, another can take over seamlessly.

Security and Policy Enforcement: Controllers enforce security policies, ensuring that all APs adhere to the same security standards and providing protection against unauthorized access and potential security breaches.

Security

Security in Wireless Local Area Networks (WLANs) is crucial to protect sensitive data, prevent unauthorized access, and maintain the integrity of the network. Various security measures are employed to ensure the confidentiality, authenticity, and availability of data in WLANs. Some key security aspects in WLANs include:

Description

Encryption: Encryption is used to protect data during transmission and storage. Strong encryption protocols, such as WPA2 (Wi-Fi Protected Access 2) with AES (Advanced Encryption Standard), are used to encrypt data packets, ensuring that only authorized recipients can read the data.

Authentication: WLAN authentication verifies the identity of devices or users attempting to connect to the network. Methods like WPA-PSK (Pre-Shared Key), 802.1X with EAP (Extensible Authentication Protocol), and certificate-based authentication are used to authenticate users, providing secure access control.

Access Control: Access control mechanisms, such as MAC filtering and captive portal authentication, are used to control which devices are allowed to connect to the WLAN. MAC filtering allows administrators to specify permitted MAC addresses, while captive portal authentication requires users to log in via a web-based portal before accessing the network.

Intrusion Detection and Prevention: Intrusion Detection Systems (IDS) and Intrusion Prevention Systems (IPS) monitor network traffic for suspicious activities and attempts to breach the network. They can detect and respond to potential threats, mitigating security risks.

Network Segmentation: WLAN segmentation involves dividing the network into separate segments or VLANs (Virtual LANs). It helps isolate sensitive data and limit the impact of a potential security breach by containing it within a smaller segment.

Guest Access: Guest access provides a separate network for visitors and guests, keeping them isolated from the main internal network. Captive portal authentication is commonly used to control guest access.

Security Updates and Patch Management: Keeping access points, routers, and other WLAN devices up to date with the latest firmware and security patches is essential to address known vulnerabilities and ensure overall network security.

Rogue AP Detection: Rogue Access Points (APs) are unauthorized APs that can pose security risks. WLANs employ rogue AP detection to identify and mitigate rogue devices that might be trying to intercept or manipulate data.

Physical Security: Physical security measures, such as limiting physical access to access points and using tamper-resistant hardware, help prevent unauthorized tampering with WLAN equipment.

Authentication

Authentication is vital for preventing unauthorized access, data breaches, and malicious activities. It is the process of verifying the identity of a user, device, or system to ensure that the claimed identity is legitimate and authorized to access specific resources or services. It is essential to use the most up-to-date and secure protocols to safeguard wireless communication and prevent unauthorized access to sensitive data.

Description

Open Authentication: Open Authentication is a simple and insecure method used in Wi-Fi networks, where no authentication or password is required to connect. Devices can freely associate with the network, making it susceptible to unauthorized access and data interception.

WEP (Wired Equivalent Privacy): WEP is an early Wi-Fi security protocol that provides basic encryption to protect wireless communication. However, WEP is weak and vulnerable to attacks, and its use is strongly discouraged due to its inability to provide robust security.

EAP (Extensible Authentication Protocol): EAP is an authentication framework used in Wi-Fi networks to support various authentication methods, such as username-password, certificates, or token-based authentication. It enables secure and flexible authentication for users and devices connecting to the network.

WPA/WPA2 (Wi-Fi Protected Access): WPA and WPA2 are Wi-Fi security protocols designed to address the vulnerabilities of WEP. They use stronger encryption methods and the Temporal Key Integrity Protocol (TKIP) or Advanced Encryption Standard (AES) to enhance security. WPA2, being more secure, is widely used and recommended for modern Wi-Fi networks.

WPA3 (Wi-Fi Protected Access 3): WPA3 is the latest iteration of Wi-Fi security protocols, designed to further enhance Wi-Fi security and address vulnerabilities found in WPA2. It introduces features like individualized data encryption, resistance against offline dictionary attacks, and improved authentication methods, making it more robust against various attacks.

EAP

EAP, or Extensible Authentication Protocol, is a framework that defines various authentication protocols used in wireless networks, point-to-point (P2P) connections, and other network access scenarios. EAP itself is not a specific authentication method but rather a framework that allows for the use of different authentication protocols within its structure. EAP is commonly used in wireless networks, such as Wi-Fi networks, to secure the authentication process between a client (like a laptop or smartphone) and an authentication server. Some popular EAP methods include EAP-TLS (Transport Layer Security), EAP-PEAP (Protected Extensible Authentication Protocol), EAP-LEAP (Lightweight Extensible Authentication Protocol), and EAP-TTLS (Tunneled Transport Layer Security). There are several variations of EAP (Extensible Authentication Protocol), each designed to address specific security and authentication requirements.

Description

EAP-TLS (Transport Layer Security): Utilizes digital certificates for both the client and the server to establish a secure TLS tunnel for authentication.

EAP-PEAP (Protected Extensible Authentication Protocol): Encapsulates EAP within a TLS tunnel, providing an additional layer of security. Often used with a server-side digital certificate.

EAP-MSCHAPv2 (Microsoft Challenge Handshake Authentication Protocol version 2): Developed by Microsoft, this EAP method is commonly used for Windows-based environments. It relies on a username & password combination and is often used in conjunction with EAP-TTLS or PEAP.

EAP-TTLS (Tunneled Transport Layer Security): Creates a TLS tunnel similar to EAP-PEAP but is more extensible, allowing for a variety of authentication methods within the tunnel.

EAP-SIM (Subscriber Identity Module): Originally designed for GSM (Global System for Mobile Communications) networks, it uses SIM cards to authenticate mobile devices on the network.

EAP-AKA (Authentication and Key Agreement): Similar to EAP-SIM, it is used for authentication in mobile networks, often in 3G & 4G/LTE environments.

EAP-FAST (Flexible Authentication via Secure Tunneling): Designed to address the vulnerabilities of EAP-TLS, it creates a secure tunnel using a protected inner method, typically with username/password authentication.

EAP-GTC (Generic Token Card): Provides a generic framework for token-based authentication.

EAP-TNC (TNC = Trusted Network Connect): Used for network access control and endpoint integrity checking.

EAP-IKEv2 (Internet Key Exchange version 2): Integrates EAP into the IKEv2 protocol, commonly used in VPNs (Virtual Private Networks).

Encryption

Encryption is a security process used to protect sensitive data by converting plain, readable information (plaintext) into an unreadable format (ciphertext). It ensures data confidentiality and integrity during transmission and storage, making it challenging for unauthorized individuals to access or manipulate the information.

Description

TKIP (Temporal Key Integrity Protocol) is a security protocol used in Wi-Fi networks to improve the security of data transmission. It was designed as an upgrade to the weak WEP (Wired Equivalent Privacy) protocol. TKIP uses a per-packet key mixing technique, periodically changing encryption keys, and includes a Message Integrity Check (MIC) to enhance security. However, TKIP is now considered outdated and less secure compared to modern encryption standards.

AES (Advanced Encryption Standard) is a widely adopted symmetric encryption algorithm, renowned for its strong security and efficiency. AES operates on fixed-size blocks of data and uses a secret encryption key to transform plaintext into ciphertext and vice versa. It is commonly used in various applications, including secure communication, data storage, and cryptographic protocols. AES with 128-bit, 192-bit, or 256-bit key lengths is the standard for modern encryption.

Authentication Methods

Authentication methods are mechanisms used to verify the identity of devices or users attempting to connect to a Wi-Fi network. These authentication methods help ensure that only authorized users or devices gain access to the network and its resources. Several WLAN authentication methods exist, and they can be broadly categorized into the following types:

Description

Pre-Shared Key (PSK) Authentication: PSK authentication, also known as WPA-PSK or WPA2-PSK, uses a shared secret, such as a password or passphrase, which is known to both the client device and the wireless access point (AP). The client provides this key during the connection process, and if it matches the one stored in the AP, the client is granted access. PSK is commonly used for securing home and small business Wi-Fi networks.

iPSK (Identity Pre-Shared Key): iPSK, or Identity Pre-Shared Key, is an enhanced form of PSK used in enterprise Wi-Fi networks. Unlike a standard PSK where one shared key is used for all clients, iPSK assigns unique individualized PSKs to each user or device. These individual PSKs are associated with the user's identity (e.g., username, device MAC address) and can be managed centrally by an authentication server or network management system. iPSK offers better security and control, as compromising one user's credentials does not affect the security of others.

802.1X Authentication: 802.1X is a port-based network access control protocol that provides more secure authentication for enterprise Wi-Fi networks. It uses the Extensible Authentication Protocol (EAP) to enable clients to provide their credentials (e.g., username and password) to an authentication server, such as a RADIUS server. The server then validates the credentials, and based on the result, grants access or denies access to the network.

Captive Portal (Web-based) Authentication: Captive portal authentication requires users to authenticate by providing login credentials through a web-based portal before accessing the internet or network resources. Users are typically redirected to the portal when they try to access the internet, and they must enter valid credentials to gain network access. Captive portal authentication is commonly used in public Wi-Fi hotspots, hotels, and other guest networks.

Certificate-based Authentication: Certificate-based authentication uses digital certificates to verify the identity of clients and the network. Client devices present a digital certificate during the authentication process, and the server validates the certificate to determine if the client is authorized to access the network. This method is commonly used in enterprise Wi-Fi networks and provides strong security.

MAC-Filtering

MAC filtering, also known as MAC address filtering or Access Control List (ACL), is a security feature used in wireless networks to control device access based on the Media Access Control (MAC) addresses of their network interface cards (NICs). A MAC address is a unique identifier assigned to each network device, and it is hardcoded into the device's hardware.

Description

In MAC filtering, the network administrator creates a list of permitted MAC addresses (allowlist) or blocked MAC addresses (denylist) in the wireless router or access point. Devices attempting to connect to the Wi-Fi network must undergo MAC address verification before being granted access. It is not a very secure method because MAC addresses can be changed easily.

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