IEEE 802.11

The 802.11 standard is a family of wireless standards created by the Institute of Electrical and Electronics Engineers (IEEE). 802.11n is the most appropriate way to call Wi-Fi technology, released in 2009. It improved over previous versions of Wi-Fi with multiple radios, advanced transmit and receive techniques, and the option to use 5-band spectrum. GHz. All that means a data rate of up to 600 Mbps.

Description

The 802.11 family consists of a series of over-the-air half duplex modulation techniques that use the same basic protocol. The 802.11-1997 standard was followed by 802.11b, which was the first to be widely accepted. Later, improved versions would emerge: 802.11a, 802.11g, 802.11n and 802.11ac. Other standards in the family (c-f, h, j) are service modifications that are used to extend the current scope of the existing standard, which may also include corrections to a previous specification.

ISM band spectrum

The 802.11b and 802.11g versions use the 2.4 GHz ISM band, in the United States, for example, they operate under the Rules and Regulations of the United States Federal Communications Commission. Due to this choice of frequency band, 802.11b and 802.11g equipment may experience interference from common household appliances such as microwaves, ovens, or Bluetooth devices. That is why they must control such susceptibility to interference using Direct Sequence Spread Spectrum (DSSS) and Orthogonal Frequency Division Multiplexing (OFDM) signaling methods, respectively.

On the other hand, the 802.11a version uses the 5GHz U-NII band which, for much of the world, offers at least 23 non-overlapping channels instead of the 2.4GHz ISM frequency band which offers only three channels that do not overlap. 802.11n can use either the 2.4 GHz or 5 GHz band while 802.11ac uses only the 5 GHz band. The segment of the radio frequency spectrum used by 802.11 varies from country to country. The frequencies used by channels one through six of 802.11b and 802.11g fall within the 2.4 GHz amateur radio band. Licensed amateur radio operators can operate 802.11b/g devices.

General concepts

• Stations: computers or devices with network interface.
• Media: Two can be defined, radio frequency and infrared.
• Access point (AP): has the functions of a bridge (connects two networks with similar or different levels of link), and therefore performs the relevant plot conversions.
• Distribution system: important as they provide mobility between AP, for plots between different points of access or with terminals, they help as it is the mechanism that controls where the station is to send the plots.
• Basic Service Set (BSS): group of stations that intercom between them. Two types are defined:
  1. Independent: when the stations intercom directly.
  2. Infrastructure: when all are communicated through a point of access.
• Extended Service Set (ESS): is the union of several BSS.
• Basic Service Area: important in the 802.11 networks, since what indicates is the ability to change the location of the terminals, varying the BSS. The transition will be correct if it is carried out within the same ESS in another case it will not be possible.
• Network limits: the limits of the 802.11 networks are diffuse as different BSS can overlap.

Protocols

IEEE 802.11-1997

The original version of the 802.11 standard, from the Institute of Electrical and Electronics Engineers (IEEE), published in 1997, specifies two “theoretical” transmission speeds of 1 and 2 megabits per second (Mbit/ s) that are transmitted by infrared (IR) signals. IR is still part of the standard, although no implementations are available. It had a revision in 1999 with the intention of updating it, however today it is obsolete.

The original standard also defines the protocol "carrier sense multiple access avoiding collisions" (carrier sense multiple access with collision avoidance, CSMA/CA) as the access method. An important part of the theoretical transmission speed is used in the needs of this coding to improve the transmission quality under diverse environmental conditions, which resulted in interoperability difficulties between equipment of different brands. These and other weaknesses were corrected in the 802.11b standard, which was the first of this family to achieve wide acceptance among consumers.

IEEE 802.11a

The 802.11a revision was approved in 1999. This standard uses the same set of base protocols as the original standard, operates in the 5 GHz band, and uses 52 Orthogonal Frequency Division Multiplexing (Orthogonal) subcarriers. Frequency-Division Multiplexing, OFDM) with a maximum speed of 54 Mbit/s, making it a practical standard for wireless networks with actual speeds of approximately 20 Mbit/s. The data rate is reduced to 48, 36, 24, 18, 12, 9 or 6 Mbit/s if necessary.

Since the 2.4 GHz band is heavily used to the point of congestion, using the relatively unused 5 GHz band gives 802.11a a significant advantage. However, this high carrier frequency also has a drawback: the effective overall range of 802.11a is less than that of 802.11b/g. In theory, 802.11a signals are more easily absorbed by walls and other solid objects in their path due to their smaller wavelength, and as a result cannot penetrate as far as 802.11b signals. In practice, 802.11b typically has a higher range at low speeds. 802.11a also suffers from interference, but locally there may be fewer signals to interfere with, resulting in less interference and better performance.

It has 12 non-overlapping channels, 8 for wireless network and 4 for point-to-point connections. It cannot interoperate with equipment of the 802.11b standard, except if equipment that implements both standards is available.

IEEE 802.11b

The 802.11b revision of the original standard was ratified in 1999.

802.11b has a maximum transmission speed of 11 Mbps and uses the same access method defined in the original CSMA/CA standard. The 802.11b standard operates in the 2.4 GHz band. Due to the space occupied by the CSMA/CA protocol coding, in practice, the maximum transmission speed with this standard is approximately 5.9 Mbit/s over TCP. and 7.1 Mbit/s over UDP.

Products using this version appeared on the market in the early 2000s, as 802.11b is a direct extension of the modulation technique defined in the original standard. The dramatic increase in performance of 802.11b and its reduced price led to the rapid acceptance of 802.11b as the definitive wireless LAN technology.

Devices using 802.11b may experience interference from other products operating in the 2.4 GHz band.

IEEE 802.11c

It is less used than the first two, due to the implementation that this protocol reflects. The 'c' protocol is used for the communication of two different networks or of different types, as well as connecting two distant buildings with each other, as well as connecting two networks of different types through a wireless connection. The 'c' protocol is more used on a daily basis, due to the cost involved in long installation distances with fiber optics, which, although more reliable, is more expensive both in monetary instruments and in installation time.

The combined 802.11c standard is of no interest to the general public. It is just a modified version of the 802.11d standard that allows 802.11d to be combined with 802.11 compatible devices (at the layer 2 data link layer of the OSI model).

• Speed (theoric) - 600 Mbit/s
• Speed (practice) - 100 Mbit/s
• Frequency - 2.4 Ghz and 5.4 Ghz
• Bandwidth - 20/40 MHz
• Scope - 820 meters
• Year of implementation - 2009

IEEE 802.11d

It is a supplement to the 802.11 standard that is intended to allow international use of local 802.11 networks. It allows different devices to exchange information in frequency ranges according to what is allowed in the country of origin of the mobile device.

IEEE 802.11e

The IEEE 802.11e specification provides a wireless standard that enables interoperability between public, business, and residential user environments, with the added ability to address the needs of each industry. Unlike other wireless connectivity initiatives, this can be considered as one of the first wireless standards that allows working in home and business environments. The specification adds QoS and multimedia support features to the 802.11b and 802.11a standards, while maintaining compatibility with them. These features are essential for home networks and for carriers and service providers to build advanced offerings. It also includes error correction (FEC) and covers the audio and video adaptation interfaces in order to improve the control and integration in layers of those mechanisms that are in charge of managing lower range networks. The centralized management system integrated in QoS avoids collisions and bottlenecks, improving the delivery capacity in critical time of loads. With the 802.11 standard, IEEE 802.11 technology supports real-time traffic in all types of environments and situations. Real-time applications can function reliably thanks to the Quality of Service (QoS) provided by 802.11e. The objective of the new 802.11e standard was to introduce new mechanisms at the MAC layer level to support services that require Quality of Service guarantees. To meet its goal, IEEE 802.11e introduced a new element called Hybrid Coordination Function (HCF) with two types of access:

• EDCA, Enhanced Distributed Channel Accessequivalent to DCF.
• HCCA, HCF Controlled Accessequivalent to PCF.

This standard defines four categories of access to the medium (ordered from least to most priority).

• Background (AC_BK)
• Best Effort (AC_BE)
• Video (AC_VI)
• Voice (AC_VO)

In order to achieve traffic differentiation, different access times to the medium and different sizes of the contention window are defined for each of the categories.

IEEE 802.11f

This is a recommendation for access point vendors that allows products to be more compatible. It uses the IAPP protocol that allows a roaming user to seamlessly switch from one access point to another while on the move no matter what brands of access points are used in the network infrastructure. This property is also known simply as roaming. Its maximum distance is 50 m

IEEE 802.11g

In June 2003, a third modulation standard was ratified: 802.11g, which is the evolution of 802.11b. This uses the 2.4 Ghz band (just like 802.11b), but operates at a maximum theoretical speed of 54 Mbit/s, which on average is 22.0 Mbit/s actual transfer speed, similar to the of the 802.11a standard. It is compatible with the b standard and uses the same frequencies. Much of the design process for the new standard was taken by making both models compatible. However, in networks under the g standard, the presence of nodes under the b standard significantly reduces the transmission speed.

Equipment that works under the 802.11g standard reached the market very quickly, even before its ratification, which was given approximately on June 20, 2003. This was partly due to the fact that to build equipment under this new standard, it was possible to adapt those already designed to the standard b.

Currently, equipment with this specification is sold, with powers of up to half a watt, which allows communications over 50 km with satellite dishes or appropriate radio equipment.

There is a variant called 802.11g+ capable of reaching 108 Mbps transfer rate. It generally only works on equipment from the same manufacturer as it uses proprietary protocols.

802.11g and 802.11b interaction

802.11g has the advantage of being able to coexist with the 802.11a and 802.11b standards, this because it can operate with DSSS and OFDM RF Technologies. However, if it is used to implement users working with the 802.11b standard, the performance of the wireless cell will be affected by it, allowing only a transmission speed of 54 Mbps. This degradation is due to the fact that 802.11b clients do not understand OFDM.

Assuming that you have an access point that works with 802.11g, and currently a client with 802.11b and another 802.11g are connected, since the 802.11b client does not understand the OFDM forwarding mechanisms, which are used by 802.11g, collisions will occur, which will cause data to be resent, further degrading our bandwidth.

Assuming that the 802.11b client is not currently connected, the Access Point sends frames that provide information about the Access Point and the wireless cell. Without the 802.11b client, the following information would be seen in the frames:

NON_ERP present: no
Use Protection: no

ERP (Extended Rate Physical) refers to devices that use extended data rates, in other words, NON_ERP refers to 802.11b. If they were ERPs, they would support the high transfer rates that 802.11g supports.

When an 802.11b client associates with the AP (Access Point), the latter alerts the rest of the network about the presence of a NON_ERP client. Changing their plots as follows:

NON_ERP present: yes
Use Protection: yes

Now that the wireless cell knows about the 802.11b client, the way information is sent within the cell changes. Now when an 802.11g client wants to send a frame, it must first warn the 802.11b client by sending an RTS (Request to Send) message at 802.11b rate so that the 802.11b client can understand it. The RTS message is sent as a unicast. The 802.11b receiver responds with a CTS (Clear to Send) message.

Now that the channel is free to send, the 802.11g client sends its information at speeds according to its standard. The 802.11b client perceives the information sent by the 802.11g client as noise.

The intervention of an 802.11b client in an 802.11g type network is not limited only to the cell of the Access Point in which it is connected, if it is working in an environment with multiple APs in Roaming, the APs to which the 802.11b client is not connected will transmit frames with the following information to each other:

NON_ERP present: no
Use Protection: yes

The previous frame tells them that there is a NON_ERP client connected to one of the APs, however, as Roaming is enabled, it is possible that this 802.11b client connects to one of them at any time, so they must use security mechanisms throughout the wireless network, thus degrading the performance of the entire cell. This is why clients should preferably connect using the 802.11g standard. Wi-Fi (802.11b/g).

IEEE 802.11h

The 2000 802.11h specification is a modification of the 802.11 WLAN standard developed by the IEEE LAN/MAN Standards Committee Working Group 11 (IEEE 802) and released in October 2003. 802.11h tries to solve problems derived from the coexistence of 802.11 networks with radar or satellite systems.

The development of 802.11h follows some recommendations made by the International Telecommunication Union (ITU) that were motivated mainly by the requirements that the European Radiocommunications Office (ERO) deemed appropriate to minimize the impact of opening the band of 5 GHz, generally used by military systems, to ISM applications (ECC/DEC/(04)08).

In order to meet these requirements, 802.11h provides 802.11a networks with the ability to dynamically manage both frequency and transmit power.

Dynamic Frequency Selection

DFS (Dynamic Frequency Selection) is a functionality required by WLANs operating in the 5 GHz band in order to avoid co-channel interference with communication systems. radar and to ensure uniform use of available channels.

Transmitter Power Control

TPC (Transmitter Power Control) is a functionality required by WLANs operating in the 5 GHz band to ensure that the transmitted power limitations that can be transmitted are respected. available for different channels in a certain region, so that interference with satellite systems is minimized.

IEEE 802.11i

It is aimed at addressing the current security vulnerability for authentication and encryption protocols. The standard encompasses the protocols 802.1x, TKIP (Temporary-Secure Key Protocol), and AES (Advanced Encryption Standard). It is implemented in Wi-Fi Protected Access (WPA2). The standard was ratified on June 24, 2004.

IEEE 802.11j

It is equivalent to 802.11h, in the regulation of Japan. It was specially designed for the Japanese market and allows wireless LAN operation in the 4.9 to 5 GHz band to conform to the Japanese standards for radio operation for indoor, outdoor, and mobile applications. The amendment has been incorporated into the published IEEE 802.11-2007 standard.

IEEE 802.11k

Allows wireless switches and access points to calculate and value the radio frequency resources of the clients of a WLAN network, thus improving its management. It is designed to be implemented in software, to support it the WLAN equipment only needs to be updated. And, of course, for the standard to be effective, both the clients (WLAN adapters and cards) and the infrastructure (WLAN access points and switches) must be compatible.

IEEE 802.11n

In January 2004, the IEEE announced the formation of an 802.11 Working Group (Tgn) to develop a new revision of the 802.11 standard. Actual transmission speed could reach 650 Mbps (meaning theoretical transmission speeds would be even higher), and should be up to ten times faster than a network under the 802.11a and 802.11g standards, and about forty times faster. faster than a network under the 802.11b standard. It was also expected that the scope of operation of the networks would be greater with this new standard thanks to the MIMO technology (Multiple Input – Multiple Output), which allows the use of several channels at the same time to send and receive data. thanks to the incorporation of several antennas (3). There are also other alternative proposals that may be considered. The standard is already written, and has been implemented since 2008. At the beginning of 2007, the second draft of the standard was approved. Previously, there were already devices that were ahead of the protocol and offered this standard unofficially (with the promise of updates to comply with the standard when the final one was implemented).

Unlike other versions of Wi-Fi, 802.11n can work in two frequency bands: 2.4 GHz (the one used by 802.11b and 802.11g) and 5 GHz (the one used by 802.11a). As a result, 802.11n is compatible with devices based on all previous editions of Wi-Fi. In addition, it is useful that it works in the 5 GHz band, since it is less congested and in 802.11n it allows to achieve higher performance.

The 802.11n standard was ratified by the IEEE organization on September 11, 2009 with a speed of 600 Mbps in the physical layer.

Most products are to the "b" or "g", however, the 802.11n standard has already been ratified, which raises the theoretical limit to 600 Mbps. There are currently several products that comply with the "N" with a maximum of 600 Mbps (80-100 stable).

The 802.11n standard makes simultaneous use of both 2.4 Ghz and 5 Ghz bands. The networks that work under the 802.11b and 802.11g standards, after the recent ratification of the standard, are beginning to be mass-produced and are the subject of promotions by the different Internet Service Providers, so that the massification of said technology seems to be on the way.

All the versions of 802.11xx provide the advantage of being compatible with each other, so that the user will not need anything more than its integrated Wi-Fi adapter to be able to connect to the network.

Without a doubt, this is the main advantage that differentiates Wi-Fi from other proprietary technologies, such as LTE, UMTS and Wimax, the three mentioned technologies are only accessible to users by subscribing to the services of an operator that is authorized for use of radioelectric spectrum, through a national concession.

Most manufacturers already incorporate 802.11n Wi-Fi equipment into their production lines, for this reason the ADSL offer is usually accompanied by 802.11n Wi-Fi in the domestic user market.

It is known that the future replacement standard for 802.11n will be 802.11ac with transfer rates greater than 1 Gb/s.

IEEE 802.11p

This standard operates in the 5.90 GHz and 6.20 GHz frequency spectrum, especially suitable for automobiles. It will be the basis of dedicated short-range communications (DSRC). DSRC technology will allow the exchange of data between vehicles and between cars and road infrastructure. It also adds wireless access in vehicular environments or WAVE (wireless access in vehicular environments), a vehicular communication system. This improvement is widely used in the implementation of Intelligent Transport Systems (ITS). This includes the exchange of data between vehicles with each other and between vehicles and the infrastructure of the roads on which they travel.

IEEE 802.11r

Also known as Fast Basic Service Set Transition, its main feature is to allow the network to establish security protocols that identify a device to the new access point before it leaves the current one and go to it. This function, which once stated seems obvious and indispensable in a wireless data system, allows the transition between nodes to take less than 50 milliseconds. A period of time of this magnitude is short enough to maintain communication via VoIP without perceptible interruptions.

IEEE 802.11v

It was published in 2011. It will serve to allow remote configuration of client devices. This will allow management of the stations in a centralized way (similar to a cellular network) or distributed, through a data link layer mechanism (layer 2). This includes, for example, the network's ability to monitor, configure, and update client stations. In addition to improved management, new capabilities provided by the "11v" They are broken down into four categories:

1. energy saving mechanisms with VoIP Wi-Fi handheld devices in mind;
2. positioning, to provide new location-dependent services;
3. timer, to support applications that require a very precise calibration;
4. coexistence, which brings together mechanisms to reduce the interference between different technologies on the same device.

IEEE 802.11w

It is a protocol that is part of IEEE 802.11 based on the 802.11i protocol, it serves to protect WLAN networks against subtle attacks on wireless management frames (WLAN).

Not finished yet. TGw is working on improving the access control layer of the IEEE 802.11 medium to increase the security of the authentication and encryption protocols.

WLANs send system information in unprotected frames, which makes them vulnerable. This standard will be able to protect networks against disruption caused by malicious systems creating detached requests that appear to be sent by valid equipment. An attempt is made to extend the protection provided by the 802.11i standard beyond the data to the management frames, responsible for the main operations of a network. These extensions will have interactions with IEEE 802.11r and IEEE 802.11u.

IEEE 802.11ac

IEEE 802.11ac (also known as WiFi 5 or WiFi Gigabit) is an enhancement to the IEEE 802.11n standard, developed between 2011 and in 2013, and finally approved in July 2014.

The standard consists of improving transfer rates up to 433 Mbit/s per data stream, theoretically achieving rates of 1.3 Gbit/s using 3 antennas. It operates within the 5 GHz band, extends the bandwidth up to 160 MHz (40 MHz on 802.11n networks), uses up to 8 MIMO streams, and includes high-density modulation (256 QAM).

IEEE 802.11ax

IEEE 802.11ax, also referred to as Wi-Fi 6 or Wi-Fi 6th Generation by the Wi-Fi Alliance, is designed to operate in the spectrums existing 2.4 GHz and 5 GHz networks. Introduces OFDMA to improve global spectrum efficiency. use at 6 GHz and without a license, so any provider can use it free of charge.

Channels and frequencies

IEEE 802.11b and IEEE 802.11g

The channel identifiers, center frequencies, and regulatory domains for each channel used by 802.11b and 802.11g:

The 802.11b and 802.11g standards use the 2.4 GHz band. In this band, 11 channels usable by Wi-Fi equipment were defined, which can be configured according to particular needs. However, the 11 channels are not completely independent (one channel overlaps and causes interference up to a channel 4 channels away). The signal bandwidth (22 MHz) is greater than the separation between consecutive channels (5 MHz), therefore a separation of at least 5 channels is necessary in order to avoid interference between adjacent cells, since when using channels with a separation of 5 channels between them (and at the same time each of these with a separation of 5 MHz from its neighboring channel) then a final separation of 25 MHz is achieved, which is greater than the bandwidth used by each channel of the 802.11 standard, which is 22 MHz. Traditionally, channels 1, 6, and 11 are used, although the use of channels 1, 5, 9, and 13 (in European domains) has been documented as not detrimental to performance from the network.

This channel assignment is usually done only at the access point, since the "clients" automatically detect the channel, except in cases where an "Ad-Hoc" or point-to-point network is formed when there is no point of access.

IEEE 802.11a

The channel identifiers, center frequencies, and regulatory domains for each channel used by IEEE 802.11a:

Despite the fact that the spread spectrum and modulation are different, in the 5 GHz band a bandwidth close to 20 MHz is maintained, so that the separation requirement of 5 channels of the 2, 4 GHz is maintained.

In Europe, to avoid interference with existing satellite communications and radar systems, it is necessary to implement dynamic control of frequencies and automatic control of transmission powers; therefore, 802.11a networks must incorporate the modifications of 802.11h.