Wireless 802.11 mode. AC Standard Wi-Fi

There are several varieties of WLAN-networks that differ in the signal organization circuit, data transmission rates, a radius of network coverage, as well as radio transmitter characteristics and receiving devices. Wireless networks of IEEE 802.11b standard, IEEE 802.11g, IEEE 802.11n, IEEE 802.11Ac and others were obtained.

The first in 1999, the 802.11a and 802.11b specification were approved, the devices performed according to the 802.11b standard were most widely distributed.

Standard Wi-Fi 802.11b

Standard 802.11b. Based on the broadband modulation method with direct spectrum (DSSS SPEADRUM, DSSS). The entire working range is divided into 14 channels separated by 25 MHz to eliminate mutual interference. Data is transmitted by one of these channels without switching to others. It is possible to simultaneously use only 3 channels. The data transfer rate can automatically vary depending on the interference level and distance between the transmitter and the receiver.

The IEEE 802.11b standard implements the maximum theoretical transmission rate of 11 Mbps, which is comparable to cable Network 10 Baset Ethernet. It should be borne in mind that such a speed is possible when transmitting data by one WLAN device. If a larger number of subscriber stations is simultaneously functions, the bandwidth is distributed between all and the data transfer rate per user falls.

Standard Wi-Fi 802.11a

Standard 802.11a He was adopted in 1999, nevertheless found his application only since 2001. This standard is used mainly in the United States and Japan. In Russia and in Europe, he has not received widespread.

The 802.11A standard uses a signal modulation scheme - multiplexing with orthogonal frequencies (Orthodal Frequency Division Multiplexing, OFDM). The main data stream is divided into several parallel subnotes with a relatively low transmission rate, and then the corresponding number of carriers is used to modulate them. The standard defines three mandatory data transfer rates (6, 12 and 24 Mbps) and five additional (9, 18, 24, 48 and 54 Mbps). It is also possible to simultaneously use two channels, which increases the data transfer rate by 2 times.

Standard Wi-Fi 802.11g

Standard 802.11G. Finally was approved in June 2003. It is further improvement of the IEEE 802.11b specification and implements data transmission in the same frequency range. The main advantage of this standard is an increased bandwidth - the data transfer rate in the radio channel reaches 54 Mbps compared with 11 Mbps in 802.11b. Like IEEE 802.11b, the new specification functions in the range of 2.4 GHz, however, to increase the speed, the same signal modulation scheme is used as in 802.11a - orthogonal frequency multiplexing (OFDM).

Standard 802.11g is compatible with 802.11b. Thus, the 802.11b adapters can operate in 802.11g networks (but it is not faster than 11 Mbps), and the 802.11g adapters can reduce the data transfer rate to 11 Mbps to work in old 802.11b networks.

Standard Wi-Fi 802.11n

Standard 802.11 n. September 11, 2009 was ratified. It increases the data transfer rate almost 4 times compared to standards devices. 802.11G. (The maximum speed of which is 54 Mbps), subject to use in 802.11n mode with other 802.11n devices. The maximum theoretical data transfer rate is 600 Mbps, applying data transmission at once in four antennas. One antenna - up to 150 Mbps.

The 802.11n devices function in frequency bands 2.4 - 2.5 or 5.0 GHz.

The IEEE 802.11n standard is the OFDM-MIMO technology. Most functional is borrowed from the 802.11a standard, nevertheless iEEE standard standard 802.11n It is possible to use both the frequency band adopted for the IEEE 802.11a standard and the frequency range adopted for IEEE 802.11b / g. Thus, the devices supporting the IEEE 802.11n standard can function in the frequency range or 5, or 2.4 GHz, and the specific implementation depends on the country. For Russia, the IEEE 802.11n standard device will maintain a frequency range of 2.4 GHz.

An increase in the transmission rate in the IEEE 802.11n standard is achieved due to: doubling the channel width from 20 to 40 MHz, as well as due to the implementation of MIMO technology.

Standard Wi-Fi 802.11ac

Standard 802.11As is the further development of technologies entered in the 802.11n standard. In the Specifications of the 802.11Ac standard, the VHT class is assigned to the VHT class (Very High Throughput) - with veryhigh bandwidth. 802.11As networks work exclusively in the 5 GHz band. The radio channel can be 20, 40, 80 and 160 MHz. It is also possible to combine two radio channels 80 + 80 MHz.

Comparison 802.11n and 802.11ac

Sources:

1. A.N. Steputin, A.D. Nikolaev.Mobile communication on the way to 6G . In 2 T. - 2nd ed. - Moscow-Vologda: infra-engineering, 2018. - 804c. : IL.

2. A.E. Ryzhkov, V. A. Lavrukhin heterogeneous radio access networks: tutorial. - St. Petersburg. : SPbGUT, 2017. - 92 p.

Protocol Wireless Fidelity. It was designed, scary to think in 1996. At first, he provided a user with a minimum data transfer rate. But after about three years later, new Wi-Fi standards were introduced. They increased the rate of reception and data transfer, as well as slightly increased the width of the coating. Each a new version The protocol is indicated by one or two Latin letters following the numbers 802.11 . Some Wi-Fi standards are highly specialized - they never used in smartphones. We will only talk about those versions of the data transfer protocol that an ordinary user need to know.

The very first standard did not have any letter notation. He was born in 1996 and was used for about three years. Air data when applying this protocol was downloaded at a speed of 1 Mb / s. According to modern standards, it is extremely small. But let's remember that about the exit to the "big" Internet with portable devices Then there was no speech. In those years, even WAP was not really developed, the online pages in which more than 20 KB rarely weighed.

In general, the advantages of the new technology then no one appreciated. The standard was used in strictly specific purposes - to debug equipment, remote computer configuration and other wisdom. Private users in those times about cell phone They could only dream, and the words "Wireless Data Transfer" began to be understood only after several years.

However, low popularity did not prevent the protocol to develop. Gradually began to appear devices that increase the power of the data transfer module. Speed \u200b\u200bwith the same version of Wi-Fi increased twice - up to 2 Mbps. But it was clear that this is the limit. therefore Wi-Fi Alliance (association from several large companiesestablished in 1999) had to develop new standardwhich would provide higher bandwidth.

Wi-Fi 802.11a

The first creation of the Wi-Fi Alliance became the 802.11a protocol, which also did not have oldly popular. His difference was that the technique could use the frequency of 5 GHz. As a result, the data transfer rate rose to 54 Mbps. The problem was that with a previously used frequency of 2.4 GHz, this standard was incompatible. As a result, manufacturers had to install a dual transceiver to provide work in networks on both frequencies. Do I need to say that this is not a compact solution?

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

Wi-Fi 802.11b

When designing this protocol, the creators returned to a frequency of 2.4 GHz, which has an indisputable advantage - a wide coverage area. Engineers managed to ensure that the gadgets learned to transmit data at speeds from 5.5 to 11 Mbit / s. Support this standard Immediately began to receive all routers. Gradually began to appear such Wi-Fi and in popular portable devices. For example, his support could boast the E65 smartphone. What is important, Wi-Fi Alliance provided compatibility with the very first version of the standard, thanks to which the transition period was completely unnoticed.

Until the end of the first decade of the 2000s, the 802.11b protocol was used by numerous technology. The speeds provided for them and smartphones and 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, which cannot transmit a signal to more modern versions Protocol, smartphone network still recognizes. Although you will definitely dissatisfy the speed of the data speed, since now we use completely different speed standards.

Wi-Fi 802.11g

As you have already become clear, this version of the protocol is compatible with the previous one. 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 to 54 Mbps. The release of the standard occurred in 2003. For a while, such a speed seemed even excessive, so many manufacturers of mobile phones and smartphones were slow with his introduction. Why do you need such fast data transmission, if the volume of the built-in memory in portable devices was often limited to 50-100 MB, and full-fledged Internet pages on a small screen were simply not displayed? Nevertheless, gradually the protocol won popularity, mainly at the expense of laptops.

Wi-Fi 802.11n

The most large-scale update of the standard happened in 2009. The Wi-Fi 802.11n protocol appeared on the light. At that moment, smartphones have already learned to reflect heavy web content qualitatively, so the new standard fell very by the way. His differences from the predecessors were to increase the speed and theoretical support of the frequency of 5 GHz (at the same time, 2.4 GHz also did not share anywhere). For the first time in the protocol, technology support was introduced Mimo.. It consists in supporting reception and data transmission simultaneously in several channels (in this case - in two). This allowed the theory to achieve a speed at 600 Mbps. In practice, it rarely exceeded 150 Mbps. The presence of interference on the signal path from the router to the receiving device, and many routers for saving were deprived of MIMO support. As well as budget devices, they still did not receive the possibility of working at a frequency of 5 GHz. Their creators were explained by the fact that the frequency of 2.4 GHz at that moment was not yet very loaded, and therefore the buyers of the router really did not lose anything.

The Wi-Fi 802.11n standard is still actively operated. Although many users have already noted a number of its flaws. First, due to the frequency of 2.4 GHz, it is not supported by the combination of more than two channels, which is why the theoretical speed limit is never achieved. Secondly, in hotels, shopping centers and other crowded, the channels begin to lay down on each other, which causes interference - Internet pages and content are loaded very slowly. All these problems solved the release of the following standard.

Wi-Fi 802.11ac

At the time of writing the article, the newest and fastest protocol. If previous views Wi-Fi Worked mainly at 2.4 GHz, having a number of restrictions, then here are strictly 5 GHz. This almost twice lowered the width of the coating. However, manufacturers of routers decide this problem Installation of directional antennas. Each of them sends a signal to its side. However, some people will still seem inconvenient for the following reasons:

• Routers are obtained bulky, as there are four or even more antennas in their composition;
• It is advisable to install the router somewhere in the middle between all the serviced premises;
• Routers with support for Wi-Fi 802.11ac consume more electricity than old and budget models.

The main advantage of the new standard is a tenfold speed growth and extended support for MIMO technology. From now on, they can be combined to eight channels! As a result, the theoretical flow of data is 6.93 Gbps. In the practice of speed is much lower, but even they are enough to look at some 4K film on the device.

Some people are the possibilities of the new standard seem unnecessary. Therefore, many manufacturers do not introduce its support in. Not always the protocol is supported and even fairly expensive devices. For example, its support is deprived (2016), which even after a decrease in the price tag cannot be attributed to the budget segment. To learn about what Wi-Fi standards support your smartphone or tablet, simply enough. To do this, look at it full specifications On the Internet, or run.

For almost two decades, from the moment the first standards of wireless communication 802.11 appeared, there are five universal: 802.11a, 802.11b, 802.11g, 802.11n and 802.11ac. With every new standard, the speed of the Wi-Fi network only increased.

It turned out that this is not the limit: they go to change new Wi-Fi Standard - 802.11 AX (or 11AX), which is focused on improving the performance of Wi-Fi in environments with a large amount of data traffic, as well as with frequent network overloads.

Wi-Fi 802.11 AX - increase in speed and tank

If you ever tried to connect to Wi-Fi at a concert or at the airport, of course, you are in know how many restrictions have a network in such a dense environment. Excess users who are trying to receive wireless signal, leads to a too long load on the network, which reduces its performance and signal stability. Standard 11AX solves this problem offering bEST SYSTEM Routing data where necessary.

The main purpose of previous standards of wireless networks was achieve maximum theoretical speed. And only the last standard - 802.11 AC - expanded the possibilities for connecting the set of antennas.

Wi-Fi 11AX still divides the frequency band to multiple channels using the OFDMA technology (Orthogonal Frequency Division Multiple Access). But, at the same time, 11AX can significantly increase the speed of the wireless network, it is better to manage it bandwidth, especially with high "traffic intensity" and overlapping networks.

What is the speed in the Wi-Fi 11AX network

The maximum speed of one stream of 802.11ac is about 866 MB / s, while one stream 802.11AX reaches 1.2 GB / s. This means the possibility of streaming the Ultra-HD 4K video with zero delay, downloading entire software packages in the blink of an eye and the ability to integrate the whole family of "smart" devices.

Speeds that can be obtained depending, of course, from the network and the equipment it uses. A large professional network that already has a powerful signal will obviously have significantly greater speed than networks in small companies. One way or another, you can achieve a fourfold increase in the current signal, which means a significant increase in the total capacity of the network.

Lower speed? In addition to improving productivity and range, 11AX is designed to increase the capacity of 2.4 GHz frequency ranges and 5 GHz in various environments - from home to school, enterprises, airport, stadium, etc. does not have the slightest value where you will use the Wi network -Fi, you can achieve an increase in the current speed 4 times.

Efficiency of Wi-Fi 11AX Standard

Speed \u200b\u200bis not the only important factor. 11AX also aims to implement the mechanisms that provide a consistent and reliable data flow for a larger number of users. This means increasing productivity and maintain the connection even in the case of a large amount of network traffic.

Standard 11AX operates both at a frequency of 2.4 and 5 GHz, while maintaining the existing channel bandwidths and, at the same time, increasing network capacity and expanding data transfer methods into several devices.

Standard 11AX Also supports orthogonal multiple access to frequency separation (OFDMA) - technology created to improve bandwidth mobile networks LTE.

In its current application, each time the router transmits data to the device, it uses the entire bandwidth in the channel, regardless of the data type or the number of information that are actively loaded. Thanks to OFDMA, these channels can be divided, which increases the amount of data that you can simultaneously transmit and accept.

Moreover, new Standard 802.11 AX Allows you to plan the "Awakening" time when the connection is allowed (which reduces the load). 11AX supports not only 1024QAM coding, to transfer more information units to the symbol, but also the long OFDM symbols for greater channel bandwidth and smaller interference.

Features and advantages Wi-Fi 11AX

Most Wi-Fi users understand that the connection of multiple devices reduces the network bandwidth, resulting in slowing down, not the necessary caching and communication breaks.

A new standard that is also called High-Efficiency Wireless (HW) provides another Wi-Fi management level.

The standard includes the following main functions:

• Backward compatibility with previous wireless standards wi-Fi networks (802.11 A / B / G / N / AC)
• The possibility of working on 5 GHz bands and 2.4 GHz simultaneously (and not one or other, as in previous standards).
• 2/5/10 MHz channel width for more than 20 MHz width bands.
• Increased throughput and performance:
  • 1.5 times faster than 802.11 AC
  • 3.8 times faster than 2.4 GHz 802.11 N
• Large bandwidth on objects with high user density (for example, in stadiums)
• Up to 8 times faster than devices without MU-MIMO, thanks to the use of top and bottom links (DL / UL) MU-MIMO
• 20% more airtime from the router, which means that you can transmit more data
• Improved power management to increase battery life
• Color BSS - in other words, any network will receive your color, so that they are easy to distinguish

When Starting Standard 11AX

Due to the fact that Wi-Fi 11AX increases the average data transfer rate In terms of one user, this standard is best suited for high-density environments, such as hotels, apartment buildings and campuses.

When the devices of many users are connected to the same network, they have to compete for the available resources and transmit data sequentially, one by one. Thanks to 11AX, several devices can simultaneously transmit data using the same frequency and the same network.

I.e Wi-Fi in Standard 11AX - This is not only an increase in the speed of the network. This standard improves performance and eliminates problems caused by overflow and overload Wi-Fi.

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

From the very beginning it was so that some standards work at the physical level, some - at the level of data environment, and the rest are higher levels of the interaction model open Systems.

There are the following groups of standards:

IEEE 802.11A, IEEE 802.11b, IEEE 802.11g, IEEE 802.11n and IEEE 802.11ac add the operation of the network equipment (physical level).
IEEE 802.11d standard, IEEE 802.11e, IEEE 802.11i, IEEE 802.11j, IEEE 802.11h and IEEE.
802.11R - environment parameters, radio channel frequencies, security tools, methods of transmitting multimedia data, etc.
IEEE 802.11F IEEE 802.11 The principle of interaction of points of access to each other, the operation of radio resources, etc.

IEEE 802.11

Standard IE it is 802.11 He was the "primary" among the standards of the wireless network. Work on it began in 1990. As it should be, this was done by the working group from IEEE, the purpose of which was the creation of a single standard for radio equipment, which worked at 2.4 GHz. At the same time, the task is to achieve a speed of 1 and 2 Mbit / s using DSSS and FHSS methods, respectively.

Work on the creation of the standard ended in 7 years. The goal was achieved but speed. Which provided a new standard, turned out to be too small in modern needs. Therefore, the Working Group from IEEE began developing new, more high-speed, standards.
The 802.11 Standard Developers took into account the features of the cellular architecture of the system.

Why cells? Very simple: it is enough to remember that the waves apply to different directions on a certain radius. It turns out that the externally resembles a cell. Each such cell is running under the control of the base station, which is the access point. Often the honeycomb is called basic service area.

So that the basic service areas can communicate with each other, there is a special distribution system (DISTRIBUTION SYSTEM. DS). The disadvantage of the 802.11 distribution system is the impossibility of roaming.

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

This standard is designed and focused on equipment functioning in frequency band. 2400-2483.5 MHz. In this case, the radius of the cell reaches 300 m, without limiting the topology of the network.

IEEE 802.11A.

IEEE 802.11a. This is one of the promising standards of a wireless network, which is designed to work in two radioappales - 2.4 and 5 GHz. The OFDM method used allows you to achieve a maximum data rate of 54 MBT / s. In addition to this, other speeds are provided for specifications:

• mandatory 6. 12 H 24 MBT / C;
• optional - 9, 18.3g. 18 and 54 MBT / s.

This standard also has its advantages and disadvantages. Of the advantages, we can note the following:

• using parallel data transfer;
• high transfer rate;
• the ability to connect a large number of computers.

The disadvantages of the IEEE 802.1 1A standard are:

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

To achieve high data transmission rates, the IEEE 802.1 1A standard uses in its work the QAM quadrature amplitude modulation technology.

IEEE 802.11b.

Work on standard IEEE 802 11b. (Other Name IFEE 802.11 High Rate, High throughput) was completed in 1999, and the name Wi-Fi is connected with it (Wireless Fidelity, Wireless Accuracy).

The work of this standard is based on the direct spectrum expansion (DSSS) using the Walsh eight-bit sequences. In this case, each data batch is encoded using the additional codes (SSK) sequence. This allows you to achieve a data rate of 11 Mbps.

Like the basic standard, IEEE 802.11b works with a frequency 2.4 GHz, Using no more than three non-overlapping channels. The radius of the network is about 300 m.

A distinctive feature of this standard is that if necessary (for example, with a deterioration in the quality of the signal, great remoteness from the access point. Different interference) data transfer rate can decrease up to 1 MBT / s. On the contrary, finding that the signal quality has improved, network equipment automatically increases the transfer rate to the maximum, this mechanism is called a dynamic speed shift.

In addition to the IEEE 802.11b standard equipment. Often encountered equipment IEEE 802.11n *. The difference between these standards is only in the data transfer rate. In the latter case, it is 22 Mbps due to the use of the binary batch machine coding method (P8SS).

IEEE 802.11d.

Standard IEEE 802.11d. Defines the parameters of physical channels and network equipment. It describes the rules relating to the allowed transmitter radiation power in frequency bands permissible by law.

This standard is very important, because radio waves are used for the operation of network equipment. If they do not match the specified parameters. Could prevent other devices. Working in this or nearby frequency range.

IEEE 802.11

Since the networks can be transmitted data from different formats and importance, there is a need for a mechanism that would define their importance and assigned the necessary priority. The standard is responsible for it. IEEE 802.11e, designed to transfer streaming video or audio data with guaranteed quality and delivery.

IEEE 802.11f.

Standard IEEE 802.11f Developed with a celle of providing authentication of network equipment (workstation) when the user's computer is moved from one access point to the other, that is, between network segments. At the same time, the protocol for exchanging service information IAPP (Inter-Access Point Protocol)It is necessary to transfer data between access points at the same time an effective organization of the work of distributed wireless networks is achieved.

IEEE 802.11g.

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

• mandatory -1; 2; 5,5; 6; eleven; 12 and 24 Mbit / s;
• possible - 33; 36; 48 H 54 Mbps.

To achieve such indicatively uses coding using the sequence of additional codes (SSC). The orthogonal multiplexing method (OFDM), the hybrid coding method (SSC-OFDM) and the two-batch coding method (RVS).

It is worth noting that by the same velocity can be achieved by different methods, but the mandatory data transfer rates are achieved only with the help of methods SSC PRA OFDM, And possible speeds using the SSC-OFDM and RVSS methods.

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

IEEE 802.11h

Standard IEEE 802.11h Designed to effectively control the transmitter radiation power, selecting the carrier frequency of transmission and generation of the necessary reports. It makes some new algorithms in the Environment Access Protocol MAS (Media Access Control, Medium Access Control), as well as in the physical level of the IEEE 802.11a standard.

First of all, this is due to the fact that in some countries the range 5 GHz Used to broadcast satellite televisionFor radar tracking of objects, n t. p., which may interfere with the operation of the wireless network transmitters.

The meaning of the IEEE 802.11h standard algorithms is. That when the reflected signals are detected (interference), the wireless network computers (or transmitters) can dynamically switch to another range, as well as lower or increase the power of transmitters. This makes it possible to more efficiently organize the work of street and office radio networks.

IEEE 802.11i

Standard IEEE 802.11i Designed specifically to improve the security of the wireless network. To this end, various encryption and authentication algorithms have been created, the functions are sewn when exchanging information, the possibility of generating keys, etc.:

• AES. (Advanced Encryption Standard, an advanced data encryption algorithm - an encryption algorithm that allows you to work with keys length 128. 15) 2 and 256 bits;
• Radius. (Remote Authentication Dial-in User Service, User Remote Authentication Service) is an authentication system with the ability to generate keys for each session and management of them. including package authentication algorithms, etc.;
• TKIR (Temporal Key Integrity Protocol, time key integrity protocol) - data encryption algorithm;
• Wrap. (Wireless Robust Authenticated Protocol, Sustainable Wireless Authentication Protocol) - Data Encryption Algorithm;
• SSMR (Counter with Cipher Block Chaining Message Authentication Code Protocol) - data encryption algorithm.

IEEE 802.11 J.

Standard IEEE 802.11j. Designed specifically for the use of wireless networks in Japan, namely to work in the additional radio frequency range 4.9-5 GHz. The specification is designed for Japan and expands the 802.11 standard standard with an extra channel of 4.9 GHz.

On the this moment The frequency of 4.9 GHz is considered as an additional range for use in the United States. From official sources it is known that this range is prepared for use by public and national security.
This standard expands the range of operations of the IEEE 802.11a standard devices.

IEEE 802.11n.

To date, the standard IEEE 802.11n. The most common of all standards relating to wireless networks.

The basis of the 802.11n standard:

• Increase data transfer rate;
• Expansion of the coating zone;
• An increase in the reliability of signal transmission;
• Increase bandwidth.

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

At the physical level (PHY), an enhanced signal processing and modulation was implemented, the ability to simultaneously transmit a signal through four antennas is added.

On the network level (Mac) implemented more effective use Available bandwidth. Together, these improvements make it possible to increase the theoretical data transfer rate to 600 Mbps - an increase of more than ten times, compared with 54 Mbps standard 802.11a / g (currently these devices are already considered outdated).

In reality, the performance of the wireless LAN depends on numerous factors, such as data transmission medium, radio frequency, device placement, and their configuration.

When using the 802.11n devices, it is extremely important to understand which improvements were implemented in this standard, to which they affect, as well as they combine and coexist with networks of the outdated standard 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 main points of the 802.11n standard is technology support Mimo. (Multiple Input Multiple Output, multichannel input / output).
Using the MIMO technology, the ability of simultaneous reception / transmission of multiple data streams through several antennas, instead of one.

Standard 802.11n. Determines the various antenna configurations "MHN", starting with "1x1" before "4x4."(The most common" 3x3 "or" 2x3 "configurations today). The first number (m) determines the number of transmit antennas, and the second number (n) determines the number of receiving antennas.

For example, access point with two transmitters and three receiving antennas is "2x3" mimo-The device. In the future, I will describe this standard in more detail.

IEEE 802.11g

None in any wireless standard is not specifically described roaming rules, that is, the client's transition from one zone to another. It intends to do in standard IEEE 802.11g.

Standard IEEE 802.11ac

It promises gigabit wireless speeds for consumers.

Initial draft technical specification 802.11AC. confirmed working Group (TGAC) last year. While ratification Wi-Fi Alliance Expected at the end of this year. Despite the fact that the standard 802.11AC. while in the project stage and still need to be ratified Wi-Fi Alliance and Ieee. We are already starting to see Gigabit Wi-Fi products available on the market.

Characteristics of the new generation standard Wi-Fi 802.11ac:

WLAN 802.11AC. Uses a number of new methods to achieve a huge productivity growth towards theoretically maintains gigabit potential and ensuring high bandwidths, such as:

• 6Ghz. band
• High modulation density up to 256 QAM.
• Wider bandwidth - 80mhz for two channels or 160mhz for one channel.
• Up to eight multiple input multiple output spatial streams.

Multiplayer MIMO low power consumption 802.11ac put new problems for the development of engineers working with the standard. Next, we will discuss these problems and affordable solutions that will help develop new products based on this standard.

Wider bandwidth:

802.11AC has a broader bandwidth 80 MHz or even 160 MHz compared to the previous up to 40 MHz in the 802.11n standard. The broader bandwidth leads to improved maximum bandwidth for digital Systems Communication.

Among the most complex design and production tasks - generation and analysis of broadband signals for 802.11ac. It will take testing equipment capable of processing 80 or 160 MHz to test transmitters, receivers and components.

To generate 80 MHz signals, many RF signal generators do not have a sufficiently high sampling frequency to support the typical minimum 2x dysrelation ratio, which will result in the necessary signals. Using the correct filtering and sampling the signal from the WaveForm file, it is possible to generate 80 MHz signals with good spectral characteristics and EVM.

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

These signals can be applied to external I / Q. Like vector generator generator inputs for RF frequency conversion. In addition, you can create 160 MHz signals using 80 +80 MHz mode supporting standard to create two segments 80 MHz in separate MCG or ESG signal generators, moving the radio signals.

MIMO:

Mimo. It is using multiple antennas to increase communication system performance. You could see some Wi-Fi Points Access with more than one antenna. Which stick out of them - these routers use MIMO technology.

Checking MIMO designs is a change. Multichannel generation and analysis of signals can be used to represent the performance of MIMO devices. And assist in troubleshooting and verifying projects.

Linence amplifier:

Linence amplifier is characteristic and amplifier. With which the output signal of the amplifier remains a faithful input signal as increasing. Actually linearity amplifiers are linear only to the limit after which the output is saturated.

There are many methods to improve the linearity of the amplifier. Digital Presets is one of these techniques. Software design automation as SystemVue provides an application. Which simplifies and automates the digital design design for power amplifiers.

Compatibility with previous versions

Although the 802.11n standard is used for many years. But still there are also many routers and wireless devices of older protocols. Such as 802.11b and 802.11g, though they are really little. Also when moving to 802.11ac, Old Wi-Fi standards will be supported and advanced compatibility.

That's all for now. If you still have questions, you can safely write me in,

The ability to create a local network without using cables looks very tempting and the advantages of this approach are obvious. Take, for example, a standard apartment. When creating a local network, the first question that occurs in front of the owner of the computer is how to hide all the cables so that they are not confused under their feet? For this, it is necessary or purchased special boxes that are attached to the ceiling or walls, or use other methods, including the most obvious, for example, hide cables under the carpet.

However, few people want to spend time, money and effort on the cable laying so that he does not get into the eyes. In addition, there is always a risk of carrying out a certain cable segment, resulting in the network for separate computer Or all computers will be inoperable.

The solution to this problem is wireless networks (WLAN). The main technology used to create wireless wireless networks - wi-Fi technology. This technology is rapidly gaining popularity, and many homemade local networks Created on it. Currently, there are three basic Wi-Fi Standards, each of which has certain characteristics, standards 802.11b, 802.11a and 802.11g. We are talking about the most popular standards, because in reality they are much more, and some of them are still undergoing the standardization process. For example, 802.11n standard equipment is already sold, but the standard is still developing.

The structure of the usual wireless network is practically no different from the structure of the wired network. All computers in the network are equipped with wireless adapterwhich has an antenna and connects to the PCI connector of the computer (internal adapter) or the USB connector (external adapter). For laptops can be used as external uSB adaptersSo adapters for PCMCIA connector, in addition, many laptops are originally equipped with Wi-Fi adapter. Computer interaction I. portable systems, equipped wi-Fi adapters, Provided by an access point that can be considered an analogue of the switch on the wired network.

Currently, there are three main standard wireless networks:

• 801.11b;

Consider these standards in more detail.

Standard 802.11b. was the first Wi-Fi certified standard. All devices compatible with 801.11b must have an appropriate sticker with Wi-Fi inscription. The main characteristics of 801.11b look like this:

• data transfer rate up to 11 Mbps;
• radius of up to 50 m;
• the frequency is 2.4 GHz (coincides with the frequency of some radiotelephones and microwave ovens);
• the 802.11b devices have the smallest, compared to other Wi-Fi devices, price.

The main advantage 801.11b is universal availability and low price. There are also significant drawbacks, such as low data transfer rate (almost 9 times less than the speed in the 100Base-TX network) and the use of radio frequency that coincides with the frequency of radio emission of some household devices.

Standard 802.11a. It was designed to solve the problem of low network bandwidth 801.11b. Characteristics 801.11A are presented below:

• radius of action up to 30 m;
• frequency 5 GHz;
• incompatibility with 802.11b;
• higher price of devices, compared with 802.11b.

Advantages are obvious - data transfer rate up to 54 Mbps and operating frequency not used in household appliancesHowever, this is achieved at the expense of a lower radius of action and the lack of compatibility with the popular 802.11b standard.

Third Standard, 802.11g.Gradually gained great popularity due to the data rate and compatibility rate from 802.11b. The characteristics of this standard are as follows:

• data transfer rate up to 54 Mbps;
• radius of up to 50 m;
• frequency 2.4 GHz;
• full compatibility with 802.11b;
• the price was practically equal to the cost of 802.11b devices.

802.11g standard devices can be recommended to create a wireless home network. Data transfer rates 54 Mbps and an action radius up to 50 m from the access point will be enough for any apartment, however, for a larger room, the use of wireless communication can be unacceptable.

Let's say about the 802.11n standard, which will soon turn out three other standards.

• data transfer rate up to 200 Mbps (and in the theory and up to 480 Mbps);
• radius of action up to 100 meters;
• frequency 2.4 or 5 GHz;
• compatibility with 802.11b / g and 802.11a;
• price decreases rapidly.

Of course, 802.11n is the coolest and promising standard. The radius of action is larger and the transfer rate is multiple times higher than in three other standards. However, do not rush to run to the store. 802.11n has several flaws that you need to know.

One of the best 802.11n standard routers.

The most important thing is to enjoy all the advantages of 802.11n, it is necessary that all devices in the wireless network support this standard. If one of the devices works in the standard, say, 802.11g, then the 802.11n router will be translated into the compatibility mode, and its advantages in speed and range are simply disappeared. So you want the 802.11n network - it is necessary that all devices that will be in the wireless network support this standard.

Moreover, it is desirable that the 802.11n devices are from one company. Since the standard is still being developed, different companies are implementing its capabilities, and often there are incidents when wireless device From ASUS standard 802.11n does not want to work normally with Linksys, etc.

So before introducing 802.11n at home, think if you took into account these factors. Well, read, of course, they write people in the forums, where they are actively discussing this topic.

If there are several rooms in the apartment with walls from reinforced concrete, the transmission rate is already 20-30 m below the maximum. The data transfer rate from the access point to the device will decrease in proportion to the distance to the device, since the speed will be reduced automatically to hold the steady signal.

It is desirable not to place an access point next to household or office devices, such as microwave ovens, radiotelephones, faxes, printers, etc. .

By making a decision to implement wireless networkYou should select the appropriate equipment to which it has already been said earlier, two key components - access point and wireless adapters. This is told in the article. “ “.