Wi-Fi standards and their differences from each other. Wi-Fi for Beginners: Standards Wi-Fi Version 802.11 b g n

The popularity of Wi-Fi connections is growing every day, as the demand for this type of network is increasing at a tremendous pace. Smartphones, tablets, laptops, all-in-ones, TVs, computers - all our equipment supports a wireless Internet connection, without which it is already impossible to imagine the life of a modern person.

Data transmission technologies are developing along with the release of new technology

In order to choose the network that suits your needs, you need to learn about all the Wi-Fi standards that exist today. The Wi-Fi Alliance has developed more than twenty connection technologies, four of which are the most popular today: 802.11b, 802.11a, 802.11g and 802.11n. The most recent discovery of the manufacturer was the 802.11ac modification, the performance of which is several times higher than the characteristics of modern adapters.

It is a senior certified wireless technology and is widely available. The device has very modest parameters:

• Information transfer rate - 11 Mbps;
• Frequency range - 2.4 GHz;
• The radius of action (in the absence of volumetric partitions) is up to 50 meters.

It should be noted that this standard has poor noise immunity and low bandwidth. Therefore, despite the attractive price of this Wi-Fi connection, its technical component lags far behind more modern models.

802.11a standard

This technology is an improved version of the previous standard. The developers have focused on the bandwidth of the device and its clock frequency. Thanks to such changes, in this modification there is no influence of other devices on the quality of the network signal.

• Frequency range - 5 GHz;
• Range - up to 30 meters.

However, all the advantages of the 802.11a standard are equally offset by its disadvantages: a reduced connection radius and a high (compared to 802.11b) price.

802.11g standard

The updated modification goes to the leaders of today's standards wireless networks, because it supports work with common 802.11b technology and, unlike it, has a fairly high connection speed.

• Information transfer rate - 54 Mbps;
• Frequency range - 2.4 GHz;
• Range - up to 50 meters.

As you can see, the clock speed has dropped to 2.4 GHz, but the network coverage has returned to the previous indicators characteristic of 802.11b. In addition, the price of the adapter has become more affordable, which is a significant advantage when choosing equipment.

802.11n standard

Despite the fact that this modification has long appeared on the market and has impressive parameters, manufacturers are still working on improving it. Due to the fact that it is incompatible with previous standards, its popularity is low.

• Information transfer rate - theoretically up to 480 Mbit / s, but in practice it turns out half as much;
• Frequency range - 2.4 or 5 GHz;
• Range - up to 100 meters.

Since this standard is still evolving, it has a characteristic: it can conflict with equipment that supports 802.11n, just because the device manufacturers are different.

Other standards

In addition to popular technologies, the Wi-Fi Alliance has developed other standards for more specialized applications. Such modifications that perform service functions include:

• 802.11d- makes compatible wireless communication devices from different manufacturers, adapts them to the features of data transmission at the level of the whole country;
• 802.11e- determines the quality of the sent media files;
• 802.11f- manages a variety of access points from different manufacturers, allows you to work in the same way in different networks;

• 802.11h- prevents loss of signal quality under the influence of meteorological equipment and military radars;
• 802.11i- an improved version of the protection of personal information of users;
• 802.11k- monitors the load of a certain network and redistributes users to other access points;
• 802.11m- contains all corrections of standards 802.11;
• 802.11p- determines the nature of Wi-Fi devices that are in the range of 1 km and moving at speeds up to 200 km / h;
• 802.11r- automatically finds a wireless network in roaming and connects mobile devices to it;
• 802.11s- organizes a fully connected connection, where each smartphone or tablet can be a router or connection point;
• 802.11t- this network tests the entire 802.11 standard, issues test methods and their results, puts forward requirements for equipment operation;
• 802.11u- this modification is known to everyone from the development of Hotspot 2.0. It ensures the interaction of wireless and external networks;
• 802.11v- in this technology, solutions are being created to improve modifications of 802.11;
• 802.11y- unfinished technology linking frequencies 3.65-3.70 GHz;
• 802.11w- the standard finds ways to strengthen the protection of access to information transfer.

The latest and most advanced 802.11ac standard

802.11ac modification devices provide users with a completely new quality of work on the Internet. The advantages of this standard include the following:

1. High speed. 802.11ac data transmission uses wider channels and higher frequency, which increases the theoretical speed to 1.3 Gbps. In practice, the throughput is up to 600 Mbps. In addition, a device based on 802.11ac transmits more data per cycle.

1. Increased number of frequencies. The 802.11ac modification is equipped with a whole range of 5 GHz frequencies. The latest technology has a stronger signal. The high range adapter covers the frequency band up to 380 MHz.
2. 802.11ac network coverage area. This standard provides a wider network range. In addition, the Wi-Fi connection works even through concrete and drywall walls. Interference from home appliances and the neighbor's Internet does not affect your connection in any way.
3. Updated technologies. 802.11ac is equipped with the MU-MIMO extension, which ensures uninterrupted operation of multiple devices on a network. Beamforming technology detects the client's device and sends it several streams of information at once.

Having become better acquainted with all the modifications of the Wi-Fi connection that exist today, you can easily choose the network that suits your needs. It should be recalled that most devices contain a standard 802.11b adapter, which is also supported by 802.11g technology. If you are looking for an 802.11ac wireless network, then the number of devices equipped with it today is small. However, this is a very urgent problem and soon all modern equipment will switch to the 802.11ac standard. Do not forget to take care of the security of Internet access by installing a complex code on your Wi-Fi connection and an antivirus to protect your computer from virus software.

On September 14, the Institute of Electrical and Electronics Engineers (IEEE) finally approved the final version of the WiFi 802.11n wireless standard. To say that the process of adopting the specifications was delayed is to say nothing: devices supporting the first preliminary version of the standard could be bought at the end of 2006, but they did not work very stably. Distribution received devices that support the second preliminary version of the standard (draft 2.0), rid of most of the "childhood diseases". They have been on sale for about two years, and their owners do not complain about the abundance of problems with wireless communication: they work - and work. And pretty fast and stable.

How a new version Is everyone's favorite Wi-Fi better than the old one? The maximum theoretical speed for 802.11b is 11 Mbps at 2.4 GHz, for 802.11a it is 54 Mbps at 5 GHz, and for 802.11g it is also 54 Mbps at 2.4 GHz. In 802.11n, the bandwidth varies and can be either 2.4 GHz or 5 GHz, and the maximum speed reaches an amazing 600 Mbps. Of course, in theory. In practice, 802.11n manages to squeeze out a "more mundane", but still impressive 150 Mbps. We also note that due to the support of both frequency ranges, backward compatibility is achieved with both 802.11a and 802.11b / g.

Several technologies have made it possible to improve speed performance. Firstly, MIMO (Multiple Input Multiple Output), the essence of which is to equip devices with several transmitters operating at the same frequency at once, and to separate data streams between them. Secondly, the developers used a technology that allows the use of not one, but two frequency channels with a width of 20 MHz each. If necessary, they work either separately or together, merging into one wide 40-MHz channel. In addition, IEEE 802.11n uses an OFDM (orthogonal frequency multiplexing) modulation scheme - thanks to it (specifically, thanks to the use of 52 subcarriers, of which 48 are intended directly for data transmission, and 4 for pilot signals), the data rate for one spatial stream can reach 65 Mbps. In total, there can be from one to four such flows in each of the directions.

The situation with coverage areas and reception stability has also improved significantly. Remember the famous proverb "One head is good, but two is better"? So, the same principle applies here: there are now several transmitters, antennas too, which means that it will be better to catch the network of all this economy - it will most likely not be possible to be outside the access point zone located on the next floor.

Situation in Russia

In autumn, the Radio Research Institute (NIIR) will prepare standards for the use of equipment for the operation of the 802.11n wireless communication standard in Russia. Now the equipment that supports it can only be used in intranet networks, and after the adoption of the NLA, it will be possible to use it in public networks.

According to Dmitry Laryushin, director of technical policy at Intel in Russia, the approval of the standard by the IEEE institute will certainly play a positive role in the development and implementation of regulatory rules in the Russian Federation, which will pave the way for the import and use of 802.11n equipment in our country. It is worth noting that the 11n protocol in version D2.0 has been supported by Intel's WiFi products since 2007, but, following the rules adopted in Russia for the import and use of electronic equipment, the 11n option had to be disabled. Starting next year, subject to a positive decision of the State Committee for Radio Frequencies and the introduction of regulatory legal acts for this technology, Intel c products will be supplied to the Russian market. WiFi support 11n in the final version of the standard.

Not all equipment manufacturers adhere to the letter of the law: some companies have been supplying network equipment to Russia that supports the 802.11n standard for a long time. Nothing prevents manufacturers from selling laptops equipped with 802.11n WiFi modules manufactured by Intel on the Russian market.

Protocol Wireless Fidelity was designed, scary to think, in 1996. At first, it provided the user with a minimum data transfer rate. But after about every three years, new Wi-Fi standards were introduced. They increased the speed of receiving and transmitting data, and also slightly increased the width of the coverage. Each new version of the protocol is indicated by one or two Latin letters following the numbers 802.11 . Some Wi-Fi standards are highly specialized - they have never been used in smartphones. We will only talk about those versions of the data transfer protocol that the average user needs to know about.

The very first standard did not have any letter designation. It was born in 1996 and was used for about three years. Data over the air using this protocol was downloaded at a speed of 1 Mbps. By modern standards, this is extremely small. But let's remember that access to the "big" Internet from portable devices was out of the question then. In those years, even WAP was not really developed, Internet pages in which rarely weighed more than 20 Kb.

In general, no one appreciated the advantages of the new technology then. The standard was used for strictly specific purposes - for debugging equipment, remotely configuring a computer, and other tricks. Ordinary users in those days about cell phone could only dream of, and the words "wireless data transmission" became clear to them only after a few years.

However, low popularity did not prevent the protocol from developing. Gradually, devices began to appear that increased the power of the data transmission module. The speed with the same version of Wi-Fi has doubled - up to 2 Mbps. But it was clear that this was the limit. That's why WiFi Alliance(an association of several large companies, created in 1999) had to develop a new standard that would provide higher bandwidth.

WiFi 802.11a

The first creation of the Wi-Fi Alliance was the 802.11a protocol, which also did not become very popular. Its difference was that the technique could use the 5 GHz frequency. As a result, the data transfer rate increased to 54 Mbps. The problem was that this standard was incompatible with the previously used 2.4 GHz frequency. As a result, manufacturers had to install a dual transceiver to ensure network operation on both frequencies. Do I need to say that this is not a compact solution at all?

in smartphones and mobile phones this version of the protocol was practically not used. This is explained by the fact that after about a year a much more convenient and popular solution came out.

WiFi 802.11b

When designing this protocol, the creators returned to the 2.4 GHz frequency, which has an undeniable advantage - a wide coverage area. The engineers managed to ensure that the gadgets learned to transfer data at speeds from 5.5 to 11 Mbps. All routers immediately began to receive support for this standard. Gradually, such Wi-Fi began to appear in popular portable devices. For example, the E65 smartphone could boast of its support. Importantly, the Wi-Fi Alliance ensured compatibility with the very first version of the standard, making the transition period go completely unnoticed.

Until the end of the first decade of the 2000s, it was the 802.11b protocol that was used by numerous technologies. The speeds they provided were enough for smartphones, portable game consoles, and laptops. Support this protocol and almost all modern smartphones. This means that if you have a very old router in your room that cannot transmit a signal using more modern versions of the protocol, the smartphone will still recognize the network. Although you will definitely be dissatisfied with the speed of data transfer, since now we use completely different speed standards.

WiFi 802.11g

As you already understood, this version of the protocol is backwards compatible with the previous ones. This is explained by the fact that the operating frequency has not changed. At the same time, engineers managed to increase the speed of receiving and sending data up to 54 Mbps. The standard was released in 2003. For some time, this speed seemed even redundant, so many manufacturers of mobile phones and smartphones were slow to implement it. Why is such a fast data transfer needed if the amount of built-in memory in portable devices was often limited to 50-100 MB, and full-fledged Internet pages were simply not displayed on a small screen? Still, the protocol gradually gained popularity, mainly due to laptops.

WiFi 802.11n

The most ambitious update of the standard happened in 2009. The Wi-Fi 802.11n protocol was born. At that moment, smartphones had already learned how to display heavy web content with high quality, so the new standard came in handy. Its differences from its predecessors consisted in increased speed and theoretical support for the frequency of 5 GHz (at the same time, 2.4 GHz has not disappeared either). For the first time, technology support was introduced into the protocol MIMO. It consists in supporting the reception and transmission of data simultaneously over several channels (in this case, over two). This allowed in theory to achieve speeds of 600 Mbps. In practice, it rarely exceeded 150 Mbps. The presence of interference on the signal path from the router to the receiving device affected, and many routers lost MIMO support to save money. As well as budget devices still did not get the opportunity to work at a frequency of 5 GHz. Their creators explained that the 2.4 GHz frequency at that moment was not yet heavily loaded, and therefore the buyers of the router did not really lose anything.

The Wi-Fi 802.11n standard is still actively exploited. Although many users have already noted a number of its shortcomings. First, due to the 2.4 GHz frequency, it does not support combining more than two channels, which is why the theoretical speed limit is never reached. Secondly, in hotels, shopping centers and other crowded places, channels begin to overlap each other, which causes interference - Internet pages and content are loaded very slowly. All these problems were solved by the release of the next standard.

WiFi 802.11ac

At the time of writing, the newest and fastest protocol. If the previous Wi-Fi types worked mainly at a frequency of 2.4 GHz, which has a number of limitations, then strictly 5 GHz is used here. This almost halved the width of the coverage. However, router manufacturers solve this problem by installing directional antennas. Each of them sends a signal in its direction. However, some people will still find it inconvenient for the following reasons:

• Routers are bulky, since they contain four or even more antennas;
• It is advisable to install the router somewhere in the middle between all serviced premises;
• Routers with 802.11ac Wi-Fi support consume more electricity than older and budget models.

The main advantage of the new standard is a tenfold increase in speed and enhanced support for MIMO technology. From now on, up to eight channels can be combined! This results in a theoretical data stream of 6.93 Gbps. In practice, the speeds are much lower, but even they are quite enough to watch some 4K movie online on the device.

To some people, the possibilities of the new standard seem redundant. Therefore, many manufacturers do not implement support for it in . The protocol is not always supported even by quite expensive devices. For example, it is deprived of its support (2016), which, even after lowering the price tag, cannot be attributed to the budget segment. Finding out which Wi-Fi standards your smartphone or tablet supports is easy enough. To do this, see its full specifications online, or run .

The basic IEEE 802.11 standard was developed in 1997 to organize wireless communication over a radio channel at a speed of up to 1 Mbps. in the frequency range of 2.4 GHz. Optionally, that is, with special equipment on both sides, the speed could be raised to 2 Mbps.
Following it, in 1999, the 802.11a specification was released for the 5GHz band with a maximum achievable speed of 54 Mbps.
After that, WiFi standards were divided into two used ranges:

2.4GHz band:

The radio frequency band used is 2400-2483.5 MHz. divided into 14 channels:

802.11b- the first modification of the basic Wi-Fi standard with speeds of 5.5 Mbps. and 11 Mbps. For its operation, DBPSK and DQPSK modulations, DSSS technology, Barker 11 and CCK coding are used.
802.11g- a further step in the development of the previous specification with a maximum data transfer rate of up to 54 Mbps (the real one is 22-25 Mbps). It is backward compatible with 802.11b and has a wider coverage area. Used: DSSS and ODFM technologies, DBPSK and DQPSK modulations, arker 11 and CCK coding.
802.11n- currently the most modern and fastest WiFi standard, which has a maximum coverage area in the 2.4 GHz band, and is also used in the 5GHz spectrum. Backwards compatible with 802.11a/b/g. Supports 20 and 40 MHz channel width. Used technologies ODFM and ODFM MIMO (multichannel input-output Multiple Input Multiple Output). The maximum data transfer rate is 600 Mbps (at the same time, the real efficiency is on average no more than 50% of the declared one).

5 GHz band:

The radio frequency band used is 4800-5905 MHz. divided into 38 channels.

802.11a- the first modification of the basic IEEE 802.11 specification for the 5GHz radio frequency band. Supported speed - up to 54 Mbps. The technology used is OFDM, BPSK, QPSK, 16-QAM modulations. 64QAM. The encoding used is Convoltion Coding.

802.11n- Universal WiFi standard supporting both frequency ranges. Can use both 20 and 40 MHz channel width. The maximum achievable speed limit is 600 Mbps.

802.11ac- this specification is now actively used on dual-band WiFi routers. Compared to its predecessor, it has a better coverage area and is much more economical in terms of power supply. Data transfer rate - up to 6.77 Gb / s, provided that the router has 8 antennas.
802.11ad- the most modern Wi-Fi standard today, which has optional 60 GHz band.. Has a second name - WiGig (Wireless Gigabit). Theoretically achievable data transfer rate is up to 7 Gbps.

Today we will review all existing standards IEEE 802.11, which prescribe the use of certain methods and data rates, modulation methods, transmitter power, frequency bands on which they operate, authentication methods, encryption, and much more.

From the very beginning, it has developed so that some standards work at the physical level, some - at the level of the data transmission medium, and the rest - at higher levels of the open systems interaction model.

There are the following groups of standards:

IEEE 802.11a, IEEE 802.11b, IEEE 802.11g, IEEE 802.11n and IEEE 802.11ac complete the operation of network equipment (physical layer).
IEEE 802.11d, IEEE 802.11e, IEEE 802.11i, IEEE 802.11j, IEEE 802.11h and IEEE.
802.11r - environment parameters, radio channel frequencies, security tools, methods for transmitting multimedia data, etc.
IEEE 802.11f IEEE 802.11c - the principle of interaction between access points, the operation of radio bridges, etc.

IEEE 802.11

Standard IE EE 802.11 was the "firstborn" among wireless networking standards. Work on it began in 1990. As expected, this was done by a working group from the IEEE, whose goal was to create a single standard for radio equipment that operated at a frequency of 2.4 GHz. At the same time, the task was to achieve speeds of 1 and 2 Mbps using the DSSS and FHSS methods, respectively.

Work on the creation of the standard ended after 7 years. The goal was achieved but the speed. provided by the new standard turned out to be too small for modern needs. Therefore, a working group from the IEEE began the development of new, faster standards.
The developers of the 802.11 standard took into account the peculiarities of the cellular architecture of the system.

Why cellular? Very simple: just remember that the waves propagate in different directions for a certain radius. It turns out that outwardly the zone resembles a honeycomb. Each such cell operates under the control of a base station, which is an access point. Often referred to as honeycomb base service area.

In order for the basic service areas to communicate with each other, there is a special distribution system (Distribution System. DS). The downside of the 802.11 distribution system is the inability to roam.

Standard IEEE 802.11 provides for the operation of computers without an access point, as part of one cell. In this case, the functions of the access point are performed by the workstations themselves.

This standard is designed and focused on equipment operating in the frequency band 2400-2483.5 MHz. At the same time, the cell radius reaches 300 m, without limiting the network topology.

IEEE 802.11a

IEEE 802.11a this is one of the promising wireless network standards, which is designed to operate in two radio bands - 2.4 and 5 GHz. The OFDM method used makes it possible to achieve a maximum data transfer rate of 54 Mbt/s. In addition to this, the specifications provide for other speeds:

• mandatory 6. 12 n 24 Mbt/s;
• optional - 9, 18.3G. 18 and 54 Mb/s.

This standard also has its advantages and disadvantages. Among the advantages, the following can be noted:

• use of parallel data transmission;
• high transmission speed;
• the ability to connect a large number of computers.

The disadvantages of the IEEE 802.1 1a standard are:

• smaller network radius when using the 5 GHz band (approximately 100 m): J high power consumption of radio transmitters;
• higher cost of equipment compared to equipment of other standards;
• use of the 5 GHz band requires special authorization.

To achieve high data rates, the IEEE 802.1 1a standard uses QAM technology in its work.

IEEE 802.11b

Work on the standard IEEE 802-11b(another name for IFEE 802.11 High rate, high bandwidth) was completed in 1999, and the name Wi-Fi (Wireless Fidelity, wireless accuracy) is associated with it.

The operation of this standard is based on Direct Spread Spectrum (DSSS) using eight-bit Walsh sequences. In this case, each data bit is encoded using a sequence of additional codes (SSC). This makes it possible to achieve a data transfer rate of 11 Mbps.

Like the base standard, IEEE 802.11b operates at a frequency 2.4GHz using no more than three non-overlapping channels. The range of the network is about 300 m.

A distinctive feature of this standard is that, if necessary (for example, when signal quality deteriorates, a large distance from the access point, various interferences), the data transfer rate can be reduced up to 1 Mbnt / s. On the contrary, when the network equipment detects that the signal quality has improved, it automatically increases the transmission speed to the maximum. This mechanism is called dynamic speed shifting.

Except for IEEE 802.11b standard equipment. common equipment IEEE 802.11b*. The difference between these standards is only in the data transfer speed. In the latter case, it is 22 Mbit / s due to the use of the binary packet convolutional coding (P8CC) method.

IEEE 802.11d

Standard IEEE 802.11d determines the parameters of physical channels and network equipment. It describes the rules regarding the permitted radiation power of transmitters in the frequency ranges allowed by law.

This standard is very important because radio waves are used to operate network equipment. If they do not match the specified parameters. This may interfere with other devices. operating in this or a nearby frequency range.

IEEE 802.11e

Since data of different formats and importance can be transmitted over the network, there is a need for a mechanism that would determine their importance and assign the necessary priority. This is the responsibility of the standard IEEE 802.11e, designed to stream video or audio data with guaranteed quality and delivery.

IEEE 802.11f

Standard IEEE 802.11f developed with a network equipment (workstation) authentication cell when moving the user's computer from one access point to another, that is, between network segments. At the same time, the protocol for the exchange of service information comes into effect. IAPP (Inter-Access Point Protocol), which is necessary for data transfer between access points. In this case, an effective organization of the work of distributed wireless networks is achieved.

IEEE 802.11g

The second most popular standard today can be considered the standard IEEE 802.11g. The purpose of creating this standard was to achieve a data transfer rate 54 Mbps.
Like IEEE 802.11b. The IEEE 802.11g standard is designed to operate in the 2.4 GHz frequency band. IEEE 802.11g prescribes mandatory and possible data rates:

• mandatory -1;2;5.5;6; eleven; 12 and 24 Mbps;
• possible - 33; 36; 48 n 54 Mbps.

To achieve such indicators, coding is used using a sequence of additional codes (SSC). the orthogonal frequency multiplexing method (OFDM), the hybrid coding method (SCK-OFDM) and the binary packet convolutional coding method (PBCC).

It is worth noting that the same speed can be achieved by different methods, but the required data rates are only achieved using methods SSK n OFDM, and possible velocities using the SCK-OFDM and RVSS methods.

An advantage of IEEE 802.11g equipment is compatibility with IEEE 802.11b equipment. You can easily use your computer with an IEEE standard network card. 802.11b to work with an IEEE 802.11g access point. and vice versa. In addition, the power consumption of the equipment of this standard is much lower than the equivalent equipment of the IEEE 802.11a standard.

IEEE 802.11h

Standard IEEE 802.11h designed to efficiently control the transmitter power, select the transmit carrier frequency and generate the desired reports. It introduces some new algorithms to the media access protocol MAC(Media Access Control, media access control), as well as in the physical layer of the IEEE 802.11a standard.

This is primarily due to the fact that in some countries the range 5 GHz used for broadcasting satellite TV, for radar tracking of objects, etc., which may interfere with the operation of wireless network transmitters.

The meaning of the algorithms of the IEEE 802.11h standard is that. that when reflected signals (interference) are detected, wireless network computers (or transmitters) can dynamically switch to another band, as well as reduce or increase the power of transmitters. This allows you to more effectively organize the work of street and office radio networks.

IEEE 802.11i

Standard IEEE 802.11i designed specifically to improve the security of your wireless network. For this purpose, various encryption and authentication algorithms have been created, functions are protected when exchanging information, the ability to generate keys, etc.:

• AES(Advanced Encryption Standard, advanced data encryption algorithm) - an encryption algorithm that allows you to work with keys with a length of 128. 15) 2 and 256 bits;
• RADIUS(Remote Authentication Dial-In User Service, remote user authentication service) is an authentication system with the ability to generate keys for each session and manage them. including algorithms for checking the AUTHENTICITY of packages, etc.;
• TKIR(Temporal Key Integrity Protocol, temporal key integrity protocol) - data encryption algorithm;
• WRAP(Wireless Robust Authenticated Protocol, stable wireless authentication protocol) - data encryption algorithm;
• SSMR(Counter with Cipher Block Chaining Message Authentication Code Protocol) - data encryption algorithm.

IEEE 802.11j

Standard IEEE 802.11j designed specifically for use in wireless networks in Japan, namely for operation in an additional radio frequency band 4.9-5 GHz. The specification is intended for Japan and extends the 802.11a standard with an additional 4.9 GHz channel.

4.9 GHz is currently being considered as an additional band for use in the US. It is known from official sources that this range is being prepared for use by public and national security agencies.
This standard extends the operating range of IEEE 802.11a devices.

IEEE 802.11n

Today the standard IEEE 802.11n the most widespread of all wireless networking standards.

At the heart of the 802.11n standard:

• Increasing the data transfer rate;
• Expansion of the coverage area;
• Increasing the reliability of signal transmission;
• Increase in throughput.

802.11n devices can operate in one of two bands 2.4 or 5.0 GHz.

At the physical layer (PHY), advanced signal processing and modulation has been implemented, the possibility of simultaneous signal transmission through four antennas has been added.

The network layer (MAC) implements more efficient use of available bandwidth. Together, these improvements increase the theoretical data rate to 600 Mbps– more than ten times more than 54 Mbps of 802.11a/g (these devices are now considered obsolete).

In reality, wireless performance local network depends on numerous factors such as transmission medium, radio frequency, device placement and configuration.

When using 802.11n devices, it is critical to understand exactly what enhancements have been made to the standard, what they affect, and how they fit together and coexist with legacy 802.11a/b/g wireless networks.

It is important to understand which additional features of the 802.11n standard are implemented and supported in new wireless devices.

One of the highlights of the 802.11n standard is the support for MIMO(Multiple Input Multiple Output, Multi-channel input / output).
With the help of MIMO technology, the ability to simultaneously receive / transmit several data streams through several antennas, instead of one, is implemented.

Standard 802.11n defines various "MxN" antenna configurations, starting with "1x1" before "4x4" (the most common today are the "3x3" or "2x3" configurations). The first number (M) specifies the number of transmit antennas and the second number (N) specifies the number of receive antennas.

For example, an access point with two transmit and three receive antennas is "2x3" MIMO-device. In the future, I will describe this standard in more detail.

IEEE 802.11g

None of the wireless standards clearly describe the rules of roaming, that is, the transition of the client from one zone to another. This is intended to be standard. IEEE 802.11.

IEEE 802.11ac standard

It promises gigabit wireless speeds for consumers.

Initial draft technical specification 802.11ac confirmed by the working group (TGac) last year. while the ratification WiFi Alliance expected at the end of this year. Although the standard 802.11ac still in the draft stage and still to be ratified Wi-Fi Alliance and IEEE. We are already starting to see gigabit Wi-Fi products available in the market.

Features of the next generation Wi-Fi 802.11ac:

WLAN 802.11ac uses a range of new techniques to achieve huge performance gains to theoretically support gigabit capacity and deliver high throughputs, such as:

• 6GHz band
• High modulation density up to 256 QAM.
• Wider bandwidths - 80MHz for two channels or 160MHz for one channel.
• Up to eight Multiple Input Multiple Output spatial streams.

802.11ac low power multi-user MIMO poses new development challenges for engineers working with the standard. In the following, we will discuss these issues and available solutions to help develop new products based on this standard.

Wider Bandwidth:

802.11ac has a wider bandwidth of 80 MHz or even 160 MHz compared to the previous 40 MHz in 802.11n. Wider bandwidth results in improved maximum throughput for digital communication systems.

Among the most complex design and manufacturing challenges is the generation and analysis of high bandwidth signals for 802.11ac. Testing of equipment capable of handling 80 or 160 MHz will be required to test transmitters, receivers and components.

To generate 80 MHz signals, many RF signal generators do not have a high enough sample rate to support the typical minimum 2X oversampling ratio that will result in the desired signal patterns. Using the correct filtering and resampling of the signal from the Waveform file, it is possible to generate 80 MHz signals with good spectral characteristics and EVM.

To generate signals 160MHz, a wide range arbitrary waveform generator (AWG). Such as Agilent 81180A, 8190A can be used to create analog I/Q signals.

These signals can be applied to external I/Q. As inputs of vector signal generator for RF frequency conversion. In addition, it is possible to create 160 MHz signals using the 80 + 80 MHz mode that supports the standard to create two 80 MHz segments in separate MCG or ESG signal generators, then combining the radio signals.

MIMO:

MIMO is the use of multiple antennas to improve the performance of a communication system. You may have seen some Wi-Fi access points with more than one antenna. That stick out of them - these routers use MIMO technology.

The test of MIMO designs is change. Multi-channel signal generation and analysis can be used to understand the performance of MIMO devices. And assist in troubleshooting and checking projects.

Linear Amplifier:

The Linear Amplifier is a characteristic and an amplifier. By which the output of an amplifier remains true to the input as it rises. In reality, linearity amplifiers are linear only up to a limit, after which the output saturates.

There are many methods to improve the linearity of an amplifier. Digital pre-emphasis is one such technique. Design automation software how SystemVue provides the application. Which simplifies and automates digital predistortion design for power amplifiers.

Compatibility with previous versions

Although the 802.11n standard has been around for many years. But many routers and wireless devices of older protocols still work. Such as 802.11b and 802.11g, though there are really few of them. Also in the transition to 802.11ac, old Wi-Fi standards will be supported and backwards compatible.

That's all for now. If you have any other questions, feel free to write to me at