IEEE 802.11 Wireless LAN Technology Overview

IEEE 802.11 wireless LAN technology is a widely used standard for local area networking. It was first introduced in 1997.

The technology operates on a variety of frequency bands, including the 2.4 GHz and 5 GHz bands. These frequency bands are commonly used for wireless communication.

IEEE 802.11 wireless LAN technology has undergone several revisions, with the most recent being 802.11ax. This revision offers improved performance and capacity compared to its predecessors.

The technology supports a range of data transfer rates, including 54 Mbps, 600 Mbps, and 9.6 Gbps.

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The IEEE 802.11 standards are a crucial part of wireless networking, and they're maintained by the IEEE 802 LAN/MAN Standards Committee (LMSC).

The IEEE 802.11 standards are a set of medium access control (MAC) and physical layer (PHY) specifications for implementing Wireless Local Area Network (WLAN) communication.

The 802.11 family is a series of over-the-air modulation techniques that share the same basic protocol.

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The 802.11g standard was rapidly adopted by consumers starting in January 2003. It operates at a maximum physical layer bit rate of 54 Mbit/s, exclusive of forward error correction codes.

This speed is significantly faster than its predecessor, 802.11b. However, the presence of a 802.11b device will still reduce the speed of the overall 802.11g network.

The 802.11g standard works in the 2.4 GHz band, just like 802.11b. But it uses the same OFDM based transmission scheme as 802.11a.

The 802.11g standard suffers from the same interference as 802.11b in the already crowded 2.4 GHz range. In the US and other countries with similar regulations, there are only three non-overlapping usable channels in this range.

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The IEEE 802.11 standards provide the basis for wireless network products using the Wi-Fi brand.

The 802.11 family is a series of over-the-air modulation techniques that share the same basic protocol.

The 2.4 GHz band is divided into 14 channels spaced 5 MHz apart, beginning with channel 1 which is centered on 2.412 GHz.

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Early 802.11 products use channels that are approximately 20 MHz wide.

802.11b/g radios use one of eleven 20 MHz channels within the 2.4 GHz ISM frequency band.

The 5 GHz Unlicensed National Information Infrastructure (UNII) band has twelve non-overlapping 20 MHz channels.

802.11n products can use 20 or 40 MHz wide channels in either the ISM or UNII band.

The 80 MHz channel consists of two adjacent, non-overlapping 40 MHz channels.

The 160 MHz channels are formed by two 80 MHz channels which may be adjacent or non-contiguous.

The 2.4 and 5 GHz frequency bands did not get any bigger, so products from all of the 802.11 standards are required to share the same bandwidth.

Only if there is spectrum available can the wider bandwidths be used.

The 802.11 use of the term “channel” can often lead to confusion.

The 802.11b standard was based on DSSS modulation and utilized a channel bandwidth of 22 MHz, resulting in three "non-overlapping" channels (1, 6 and 11).

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802.11g was based on OFDM modulation and utilized a channel bandwidth of 20 MHz.

The concept of non-overlapping channels has some merit in limited circumstances, but special care must be taken to adequately space AP cells.

Each 802.11b/g/n access point actually consumes multiple overlapping channels.

Transmitting on a 40 MHz 802.11n channel in the ISM band would exacerbate this scarcity by consuming 9 channels.

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The OSI model is a layered model that describes how information moves from one networked computer to another. It defines the network communications process into seven separate layers.

The OSI model is used as a reference model for the IEEE 802.11 standards, which cover protocols and operation of wireless networks. The 802.11 standards deal with the two lowest layers of the OSI reference model, the physical layer and the Data Link layer.

The Physical Layer defines the electrical and physical specifications for devices, including the relationship between a device and a transmission medium. The Physical Layer is divided into three sub layers: the Physical Layer Convergence Procedure (PLCP), the Physical Medium Dependent (PMD) layer, and the PHY management layer.

Here are the three sub layers of the Physical Layer, each with its own specific functions:

Management Frames are a crucial part of the 802.11 protocol, allowing for the maintenance of communication between stations.

Authentication Frame is the first step in the authentication process, where the wireless network interface controller (WNIC) sends an authentication frame to the access point containing its identity.

The WNIC only sends a single authentication frame with open system authentication, and the access point responds with an authentication frame indicating acceptance or rejection.

Shared key authentication involves the WNIC sending an authentication request, receiving a challenge text from the access point, encrypting the text with its own key, and then sending the encrypted text back to the access point.

The access point decrypts the text with its own key and checks if it was encrypted with the correct key, determining the WNIC's authentication status.

Here's a list of common 802.11 management frames:

These management frames play a vital role in establishing and maintaining communication between stations in a wireless network.

The OSI model is a layered model that describes how information moves from one networked computer to another, prescribing the steps to transfer data over a transmission medium. It defines the network communications process into seven separate layers.

The OSI model is used to transfer data over a transmission medium, and it's essential for understanding how information moves between networked devices. The OSI model is a fundamental concept in computer networking.

The OSI model is divided into seven layers, each with its own specific functions and responsibilities. The seven layers are: physical, data link, network, transport, session, presentation, and application.

The OSI model is used in various network protocols, including IEEE 802.11, which deals with wireless networks. The 802.11 standard covers protocols and operation of wireless networks, focusing on the physical and data link layers.

Here are the seven layers of the OSI model:

The OSI model is a fundamental concept in computer networking, and understanding its layers and functions is essential for designing and implementing network protocols.

Device Structure is a critical component of Protocol Architecture, allowing data to be transmitted and received efficiently. The structure typically consists of layers, with each layer responsible for a specific function.

The OSI Model, a widely used framework, divides the device structure into seven layers, each with its own set of protocols and functions. The layers are stacked on top of each other, with each layer relying on the one below it to function correctly.

The physical layer, the lowest layer, defines the physical means of transmitting data, such as cables and wireless connections. It's essential to ensure that devices are compatible with each other's physical layers to ensure seamless communication.

The data link layer, responsible for error-free transfer of data frames between two devices, uses protocols like Ethernet and Wi-Fi to manage data transmission. This layer ensures that data is delivered accurately and efficiently.

The network layer, responsible for routing data between devices on different networks, uses protocols like IP and ICMP to manage data transfer. It's like a postal service, ensuring that data reaches its intended destination.

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The transport layer, responsible for ensuring reliable data transfer between devices, uses protocols like TCP and UDP to manage data transmission. This layer ensures that data is delivered in the correct order and without errors.

The session layer, responsible for establishing and managing connections between devices, uses protocols like NetBIOS and SSH to manage communication. It's like setting up a phone call, establishing a connection between two devices.

The presentation layer, responsible for formatting data for transmission, uses protocols like SSL/TLS and MIME to manage data formatting. It's like preparing a package for shipping, ensuring that data is formatted correctly for transmission.

The application layer, the highest layer, provides services to end-user applications, using protocols like HTTP and FTP to manage data transfer. It's like the final delivery, providing services to end-user applications.

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Requirements are the backbone of any protocol architecture, and in the case of 802.11 wireless networking, there are specific transmitter requirements that must be met.

The transmitter requirements for 802.11a, 802.11b, and 802.11g/n are outlined in various sections of the 802.11-2012 standard. For example, Section 16 of the standard specifies the transmitter requirements for 802.11a, including the spectral emission mask and transmit power levels.

In terms of spurious emissions, the standard specifies that 802.11a transmitters should conform to in-band and out-of-band spurious emissions as set by regulatory bodies. Similarly, 802.11g/n transmitters should also conform to in-band and out-of-band spurious emissions as set by regulatory bodies.

Transmit power levels are also an important consideration. For 802.11a, the standard specifies that transmit power levels should be measured in accordance with practices specified by the appropriate regulatory bodies. Similarly, for 802.11g/n, the standard specifies that transmit power levels should be measured in accordance with practices specified by the appropriate regulatory bodies.

Here are the specific transmitter requirements for 802.11a, 802.11b, and 802.11g/n:

In terms of carrier frequency error, the standard specifies that 802.11a transmitters should have a transmit center frequency tolerance of +/-20 ppm (20 MHz and 10 MHz), +/-10 ppm (5 MHz). Similarly, 802.11g/n transmitters should have a transmit center frequency tolerance of +/-20 ppm (5GHz band), +/-25 ppm (2.4 GHz band).

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Finally, the standard specifies the allowed relative constellation error versus data rate for 802.11a, 802.11b, and 802.11g/n transmitters. For example, for 802.11a, the standard specifies that the allowed relative constellation error is -5 dB for BPSK at 1/2 coding rate, -10 dB for QPSK at 1/2 coding rate, and so on.

The frame structure of an 802.11 packet is made up of several key components, each playing a crucial role in ensuring reliable and efficient communication.

The preamble is always present and serves as a timing reference for the receiver. In the 802.11b packet format, the preamble is either long or short, containing 144 or 72 bits respectively.

The header contains configuration information, including the signal, service, length, and CRC fields. The long header uses DSSS1M, while the short header uses DSSS2M.

The payload is the actual data being transmitted, modulated with various techniques such as DSSS1M, DSSS2M, CCK5.5M, or CCK11M.

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In 802.11a/g packet format, the preamble is divided into three parts: STF, LTF, and SIGNAL. The STF uses 1/4 of the subcarriers, while the LTF uses all 52 subcarriers.

The SIGNAL field contains 24 bits of configuration data, including the rate, length, parity, and tail fields.

The data field uses 52 subcarriers, with 48 data and 4 pilot subcarriers. The data subcarriers use BPSK, QPSK, 16QAM, or 64QAM modulation.

Here's a comparison of the preamble components in different 802.11 packet formats:

As you can see, the preamble components vary across different 802.11 packet formats, reflecting the evolution of wireless communication standards.

OFDM is a robust modulation technique used in the 802.11 standards, enabling the transmission of broadband, high data rate information by dividing the data into several interleaved, parallel bit streams modulated on a separate sub-carrier.

This technique is a robust solution to counter the adverse effects of multipath propagation and inter-symbol interference (ISI). OFDM can easily adapt to improve the channel quality by offering several modulation and coding alternatives.

The primary advantage of OFDM over single-carrier schemes is its ability to cope with severe channel conditions without complex equalization filters.

Channel Bandwidths are a crucial aspect of wireless networking. Early 802.11 products use channels that are approximately 20 MHz wide.

In the US, 802.11b/g radios use one of eleven 20 MHz channels within the 2.4 GHz ISM frequency band. Three non-overlapping channels are available: 1, 6, and 11.

Later amendments added support for 5 and 10 MHz bandwidths. 802.11a radios use one of twelve non-overlapping 20 MHz channels in the 5 GHz Unlicensed National Information Infrastructure (UNII) band.

The newer standards allow for wider bandwidths to boost throughput, but the 2.4 and 5 GHz frequency bands did not get any bigger. Products from all 802.11 standards are required to share the same bandwidth.

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OFDM (Orthogonal Frequency Division Multiplexing) is a method of encoding digital data on multiple sub-carrier frequencies, enabling the transmission of broadband, high data rate information by dividing the data into several interleaved, parallel bit streams modulated on a separate sub-carrier.

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OFDM is a robust solution to counter the adverse effects of multipath propagation and inter-symbol interference (ISI), with the ability to offer several modulation and coding alternatives that can easily adapt to improve the channel quality.

In OFDM systems, the sub-carriers overlap, conserving bandwidth, and keeping the sub-carriers orthogonal to each other controls sub-carrier interference.

A guard interval is added to help prevent inter-carrier interference (ICI), as well as ISI, and a signal with a slower data rate is more resistant to multi-path fading and interference.

The primary advantage of OFDM over single-carrier schemes is its ability to cope with severe channel conditions without complex equalization filters.

OFDM may be viewed as using many slowly modulated narrowband signals rather than one rapidly modulated wideband signal, simplifying channel equalization.

OFDM Basics can be implemented using MATLAB code examples, which provide a practical way to understand and work with OFDM concepts.

Here are some key aspects of OFDM:

You can explore WLAN technology based on IEEE 802.11 standards and links to MATLAB code examples for OFDM physical layer implementation.

Country regulations play a significant role in 802.11 standards, with each country having its own set of rules for radio spectrum allocation.

In North America, only channels 1 through 11 are allowed for 802.11 standards operating in the ISM band. This is specified in the FCC Rules and Regulations, Part 15.

Japan, on the other hand, permits the use of all 14 channels for 802.11b, and channels 1-13 for 802.11g/n-2.4.

The regulatory parameters are sent in the PHY Management Layer and are used along with the channel starting frequency given in the Country Information and Regulatory Classes Annex of the 802.11 standard.

Here's a breakdown of the available channels in the 2.4 GHz band by country:

The regdomain setting is often made difficult or impossible to change to prevent conflicts with local regulatory agencies.

The 2.4 GHz band is divided into 14 channels spaced 5 MHz apart, beginning with channel 1 which is centered on 2.412 GHz.

Each channel is not entirely separate, as RF energy can "bleed" into frequencies for several adjacent channels. This means that each 802.11b/g/n access point actually consumes multiple overlapping channels.

The 802.11b standard was based on DSSS modulation and utilized a channel bandwidth of 22 MHz, resulting in three "non-overlapping" channels (1, 6 and 11).

However, even these non-overlapping channels may cause unacceptable degradation of signal quality and throughput if not adequately spaced.

The 802.11g standard, based on OFDM modulation, utilized a channel bandwidth of 20 MHz, which occasionally leads to the belief that four "non-overlapping" channels (1, 5, 9 and 13) exist.

This is not the case, and the potential non-overlapping channels in the 2.4 GHz bands are highlighted in Figure 9.

Transmitting on a 40 MHz 802.11n channel in the ISM band would exacerbate the scarcity by consuming 9 channels: the center frequency plus four channels on the left and four on the right.

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Country Regulations play a crucial role in determining the availability of 802.11 channels. Each country has its own set of rules and regulations that govern the use of radio spectrum.

In Japan, all 14 channels are available for 802.11b, and channels 1-13 are allowed for 802.11g/n-2.4. This is in contrast to Spain, which initially allowed only channels 10 and 11, and France, which allowed only channels 10, 11, 12, and 13. However, both Spain and France have since expanded their allowed channels to 1 through 13.

The US allows only channels 1 through 11 for 802.11 standards operating in the ISM band, and these devices may be operated without a license, as allowed in Part 15 of the FCC Rules and Regulations.

Here's a breakdown of the 802.11 2.4 GHz channels available by country:

Regulatory parameters are sent in the PHY Management Layer and are used along with the channel starting frequency given in the Country Information and Regulatory Classes Annex of the 802.11 standard.

Testing is a crucial step in ensuring your WLAN device meets regulatory requirements. The IEEE 802.11 standard defines the conditions for transmitter testing, but it doesn't include over-the-air control of test mode functions.

To test a device, you'll need to access its test ports, either on the device itself or on a module. This is because testing must be performed via these ports, not wirelessly.

The physical layer modulation formats and coding rates of IEEE 802.11 determine how data is sent over the air and at what data rates.

Direct-Sequence Spread Spectrum (DSSS) was used in the early 802.11 standards, while Orthogonal Frequency Division Multiplexing (OFDM) is used by many of the later standards.

The newer modulation methods and coding rates are generally more efficient and sustain higher data rates.

Table 6 highlights modulation formats for each of the 802.11 standards, showing how different methods and rates are used across various standards.

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OFDM is a primary modulation technique used today, offering increased data rates and efficiency.

The 802.11n wireless networking standard uses frame structure, physical layer components, and key functionalities for increased data rates.

The WLAN physical layer, as defined by the IEEE 802.11 standard, includes frame structure, OFDM, and transmitter/receiver architectures for WiFi networks.

The 802.11ac frame format includes components such as L-STF, L-LTF, L-SIG, VHT-SIG-A/B, VHT-STF, VHT-LTF, and Data, each serving a specific function.

IEEE 802.11ac is a standard that provides higher throughput in the 5 GHz band, with expected multi-station WLAN throughput of at least 1 Gbps and a single link throughput of at least 500 Mbps.

This standard leverages the 802.11n and 802.11a structure to ensure backwards compatibility and co-existence, allowing developers to focus on the new features needed to achieve the throughput requirements.

The 802.11ac specification extends the air interface concepts of 802.11n, including wider RF bandwidth (up to 160 MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and high-density modulation (up to 256-QAM).

To achieve these higher speeds, 802.11ac devices can use multiple spatial streams, with up to 8 streams supported in phase 2.

The standard also introduces several new features, including wider channel bandwidths (80+80 MHz and 160 MHz), higher modulation support (optional 256QAM), and multi-user MIMO (MU-MIMO).

Here's a summary of the key features and differences between 802.11ac phases:

Devices that use only the mandatory parameters can achieve a data rate of approximately 293 Mbps, while devices that take advantage of the phase 2 parameters can achieve almost 7 Gbps.

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