What does wi-fi provide? What types of Wi-Fi networks are there? What Wi-Fi actually is and how to use it

Nowadays, almost every apartment and house has its own wireless network with Internet access. Such a network greatly simplifies the use of Internet resources. However, few people know how such a network works, what a router is, and at the same time quite a lot of people would like to understand the principle of operation of such equipment. This is exactly what will be discussed further. We will tell you how the router works and what its main functions are.

What is a router

Probably the most important question to start with is what a router is and how it works. The word router itself is English and is literally translated as “router”. This means that the device assigns certain routes.

To explain this correctly, you need to describe in at least a few words how the network works. There is a subscriber and server device. The server performs the functions of a base station. It is through it that all requests coming from subscriber PCs pass. In turn, subscriber computers issue requests, so-called data packets (each packet has a destination address), the server receives these packets and sends a response. In this scheme, the router acts as a server station.

If the router is connected to global network, then it simply redirects data packets from the PC to the server (provider), acting as an intermediary. This is the purpose of the router - to collect requests from computers and redirect them further to the provider, and the provider redirects them even further - to other server stations, and so on.

The router itself is an entire mini-computer. He has his own CPU, its own RAM and various communication modules.

Thanks to this, the router has the ability to receive and process signals, create a reliable protection scheme, control data flows, and so on.

So, we have figured out what kind of device this is, now let’s move on to the question of how a Wi-Fi router works.

Principle of operation

We already know that the operating principle of a router is to assign and redistribute data flows (certain routes) between subscriber devices and server stations. It is worth noting that the default access speed is between different devices divided equally. In other words, the router’s memory contains a certain routing table, which specifies certain protocols by which the entire system operates.

It is this table that determines the paths along which data packets are sent: it contains all the addresses of connected computers and the provider (that is, all devices that are part of the network).

Thanks to this table, an organized network is created in which each signal has its own path and does not interfere with others. Moreover, the router circuit is configured in such a way that each signal from each connected computer has the most optimal route and the minimum time to receive a response.

Of course, this is not yet the answer to the question of how a Wi-Fi router works. There are a lot of subtleties and nuances here. For example, each connected device receives its own unique address. The DHCP protocol is responsible for this. And in order to select the most optimal route for each of the connected PCs, the router sends a signal to each of the addresses from time to time. This allows you to constantly update network information, keeping the map of the entire network up to date - this is called "Dynamic Routing".

DHCP is a very convenient feature. But in some cases, for security reasons, this function must be disabled. If the DHCP server is disabled, then the network parameters (in particular the network address) are set manually, which eliminates certain errors - this is called “Static routing”.

Wireless protocols

Since we have a question about how a Wi-Fi router for the home works, it’s worth paying attention wireless communication. In fact, this is the most common radio communication. It should be noted here that there are different protocols for this communication and they operate at different frequencies:

• 802.11b – 2.4 GHz. This is an outdated protocol that allows data transfer at speeds of up to 11 Mbits;
• 802.11g is a newer solution, although it operates at the same frequency, but the connection speed has been increased to 54 Mbits;
• 802.11n is new standard, which operates at 2.4 GHz and 5 GHz. By changing the signal frequency, it was possible to avoid a lot of Wi-Fi shortcomings associated with interrupting the radio signal, and also increase the transmission speed to 300 Mbits (in theory, up to 600 Mbits). It is noteworthy here that this standard operates in two frequency ranges at once, thanks to which both old and new devices can work with this protocol.

There are other standards, but they are used extremely rarely at home, as there is simply no point in doing so. After all, most modern providers provide speeds of no more than 100 Mbits. The latest standard is 802.11ac, which allows data transfer at speeds of up to 7 Gigabits.

It is also worth noting here that the higher the speed, the smaller the coverage radius. This is due to the operating principle of radio waves. Old standards (802.11b and g) have a larger coverage radius than the new one - ac. But ac has more high speed data transmission.

Principle of operation Wi-Fi router always remains the same - an intermediary between the subscriber device and the provider. Only the method of connecting to the router changes.

Conventional desktop computers are not equipped with wireless modules and the only connection option for them is a cable connection. However, if we talk about laptops, smartphones and tablets, all of these devices are equipped with Wi-Fi modules, which allows you to connect to the network without using any wires.

It is worth noting that since a laptop (smartphone or tablet) is equipped wireless adapter, then with its help you can not only receive signals, but also distribute the network, turning your laptop into a virtual router.

The question arises, how does a Wi-Fi router work on a computer? There are no differences here. The operating system itself has a built-in routing table, and therefore, creating virtual network(distribution), you simply use this table, and the computer will perform the functions of the same router.

So, we looked at what it is - a Wi-Fi router, and how it works. Now let's look at the principle of operation of the security system. This is an important issue, since network hacking threatens the loss of personal data, which an attacker can use for his own purposes. In addition, an outside user can hack the network just to access the Internet “for free,” but many have tariffs that have certain restrictions on both speed and traffic. Therefore, you should think about safety first.

It’s worth noting right away that there are different operating modes of the security system that you can configure yourself. In order to configure the security mode, you will need. Next, you need to go to the “Wireless Mode” or “Wi-Fi” section (this may be different on different models). Here you will find the “Security” or “Wireless Security” subsection.

Next, you just need to select the operating mode of the Wi-Fi router. Typically, home networks use the simplified security system WPA-PSK or WPA2-PSK. To avoid certain troubles, it is best to choose the mixed mode WPA-PSKWPA2-PSK mixed. After selecting this mode, all that remains is to assign (create and enter) a complex password and save the settings.

If speak about corporate networks, then everything is more complicated here. Such networks require a higher level of protection, since theft of corporate data entails more serious consequences. Therefore, many routers have a security mode such as WPA-WPA2 Enterprise. Here I will just clarify that this function used only system administrators in serious companies, when protection comes first.

So we spent short review How the router works - for dummies. Of course, this is a very broad topic and there are many nuances here. But in general, we looked at the purpose of the router and the very essence of its work.

How the router works: Video

Wi-Fi technology wireless transmission network information packets. This means complete elimination of wires, which is very convenient in many situations. For example, the Russian media boasted: from now on, ground broadcasts of telemetry (on-board parameters) of Soyuz-5 rockets will be carried out via Wi-Fi (IEEE 802.11 group of standards). The system simulates a router-workstation connection. The project is going through the design documentation development stage. The management of the cosmodrome is tired of the cables covering the runway. New system will significantly increase reliability and ease of use.

Wireless communication will allow you to connect and put together otherwise literally incompatible devices. Recently, Q-Stick engineers offered TV owners an original solution: make the device fully functional desktop computer. Not surprisingly, the smart device is already equipped with a processor, graphics accelerators, and an operating system. Left a little random access memory add, and the built-in access point will help establish communication between home gadgets.

Usage

The core of the system is the broadcast router (access point, base station). To become a member of the network, a computer or telephone must be equipped with wireless modules. The specified combination of equipment is usually called a station. The packet is transmitted by the center via broadcast. Carrier reception does not guarantee 100% delivery. Much is determined by external conditions and signal level.

Providers and public institutions decorate the walls with characteristic stickers, providing unlimited or paid access. They install routers at home, setting the conditions for using the resource themselves.

Router

The evolutionary router was the base station of the star topology, used by prehistoric Hawaiian developers (60-70s of the 20th century). The principle of broadcasting is still in use today. network equipment. And not only on-air. Surprisingly, today it is logical to begin the presentation of the principle of operation of a router with cable options. The radio channel is more like a public event, where the announcer, who has captured the microphone, conveys information to the audience. Adjacent rows hear each other, and this became the technical background for the introduction of the ad-hoc concept (communication without a router). However, the announcer’s voice is still louder.

A router is traditionally called a piece of equipment that redirects network data packets. Requires at least two computer networks. The home domain is separated from the external domain by the values ​​of assigned IP addresses. Sometimes (in the office of a large company) the block acts as a receiver for the services of several providers, departments, etc. From the outside, all PCs appear to the observer as having the same IP. Macs are different though.

A wireless router is characterized by the ability to send information over the air using a radio channel and electromagnetic waves.

The movement of a network packet is often represented as a chain of information transmission between node routers. The electronics reads the address of the packet, transmitting information in the right direction. Downstream wireless flow is often broadcast. Information is transmitted simultaneously to all participants. A professional router uses an address table, a protocol, substituting addresses, but home administrators often avoid complex configuration.

Well-known routers simply organize a gateway between the home segment and what is located outside (provider, Internet, and so on).

Interfaces and features

In response to the needs of the audience, manufacturers certainly provide the router with a wireless channel. Incoming traffic bypasses a physical Ethernet channel or optical fiber. Hybrid options are not excluded, but this applies more to large enterprises.

Internal tables will allow you to create galaxies of subnets, but a home user rarely appreciates the full range of possibilities. The output interfaces of the thicket are Ethernet cables and a wireless Wi-Fi channel. Enterprise versions like the Cisco CRS-1 are truly unique. Many models are still equipped with the ability to broadcast the IEEE 802.11 protocol.

Varieties

Routers are often arranged in branches of a tree structure, where throughput channels is gradually decreasing. Home Internet is no exception. Subscriber models are usually referred to by the capacious term SOHO. According to tradition, this includes equipment serving 1-10 workstations. The legislation of individual countries provides further clarification according to which equipment is purchased and manufactured. For example, New Zealanders consider a group of 6-19 employees to be a small office. The numbers below are described by the term “micro”.

The patterns for each level of the tree structure are very different. They produce special models for home users, organizations, and providers. The commercial success of the technology is ensured by the coverage of the maximum target audience with minimal effort. We have to greatly reduce prices, making the concept accessible to the masses.

SOHO

The variety will be shown below. wireless standards, as a tribute to European traditions. For now, let’s note the features of the hardware implementation of routers that correspond to the historical aspects of the development of offices in the West. A major achievement in computer communications technology at the end of the 20th century was the possibility of territorial separation (division) of large departments. Decentralization often greatly increased productivity, necessitating the production of SOHO routers.

Gradually, small-sized models reached private households. And today the number of router channels significantly exceeds the average statistical needs of the population. Some models even come with their own operating systems(Linux).

Scalability

Typical routers aim to easily scale the network through simple expansion and the use of a central station. The speed of the periphery drops significantly, sharply reducing the usefulness of the technology. Security is a separate issue. Today, the harmful effects of microwave radiation, including 2.4 GHz, used by commercial communications, are considered proven.

Etymology

Commercial use of the current name began no earlier than August 1999. The American one was fiddling with Wi-Fi advertising company Interband with British roots. Among the creations of the creative giant is a 5-level method for assessing the economic value of a brand. The 2016 Annual Report contains the following first 10 lines:

1. Apple.
2. Google.
3. Coca-Cola.
4. Microsoft.
5. Toyota.
6. Samsung
7. Amazon
8. Mercedes-Benz.
9. General Electric.

In August 1999, the company's managers were hired by Phil Belanger to come up with a name more euphonious than “IEEE 802.11b Direct Sequence.” The result is intended to be a parody of hi-fi (high-fidelity acoustic equipment). The first syllable hinted at the wireless nature of the communication channel. In addition, the company proposed a logo that is now well-known, imitating the Chinese mandala of fighting opposites (yin and yang).

The Alliance's advertising slogan played on the awkward combination of wireless clarity. Wits immediately dubbed the association the Wireless Clarity Alliance Inc. Although IEEE partially confirmed the rumors, the phrase in question was never the official name.

How to spell

The organization's letterers adhere to the same type of spelling of Wi-Fi. Considering the specifics of the mandala logo (see above), one can see in this a confrontation between the concept of quality and the fact of transmitting information wirelessly. Simply put, the incompatibility of these two concepts. In fact, the quality of wireless transmission is steadily improving. The following spellings are considered incorrect:

Story

You're probably wondering why people created a billion wireless technologies. To Wi-Fi you should add:

1. Generations of mobile communications (far from one standard).
2. Bluetooth.

At one time there was serious rivalry, but high specialization prevailed. Each protocol solves a narrow range of problems. The formulation of the question causes the usual surprise of domestic specialists. Russian universities continue to train personnel with relatively broad competencies. Western educational institutions are sharply tailoring their diploma to a specific segment of the labor market. Continuing the analogy, we see the complete similarity of the variety of highly specialized standards with the legendary monopolies of the beginning of the industrial revolution. If the USSR had decided to dictate fashion to the planet, everything could have looked different.

The history began with the concept of the interface computer, formulated (1966) by Donald Davis. In fact, the machine did the work of a router, forwarding packets. Before this, strictly two network nodes directly connected by cable could communicate. The use of routers greatly simplified the organization of communications. Initially, the idea was denoted by the short term “gate”; the first implementation is considered to be the IMP board, designed to provide communications for US defense computers.

Hawaiian Islands

The mid-60s were filled with Cold War fears. Canada's air defense lines were cut through; the significant length of the fortifications required the creation of a central coordination computerized system that calculated algorithms for the allies' further actions. Americans quickly realized the benefits of emerging digital technologies. The question of the appearance of the first networks became a matter of time. Soon (1969) super-large computers united the cable industry.

The year 1974 connected the Canadian defense lines with a host of information jumpers. In parallel, the United States, remembering the experience of Pearl Harbor, decided to connect Hawaii. The islands began broadcasting (1971) to the mainland using the ALOHA protocol, which laid the foundation for the future IEEE 802.11 standard.

ALOHA

A demonstration of performance took place in warm June. Do you see? New technology could have become dominant among cellular operators, since it covered the ocean, but the struggle of standards created a different picture. Dedicated frequencies appeared only in 1985.

ALOHA protocol used new way access to the medium (channel resources). Wireless communications duplicated wired and satellite channels. ALOHA was quickly tested in these two categories:

• Ethernet
• Marisat

The developers of the University of Hawaii under the command of Norman Abramson started in September 1968. List of participants:

1. Thomas Gaarder.
2. Franklin Kuo.
3. Shu Lin.
4. Wesley Peterson.
5. Edward Weldon.

It was planned to adapt relatively cheap commercial equipment for local communication between the islands' computers. June 1971 pleased with the first successes. The packet, bypassing the airwaves, then reached the terminal via RS-232 (COM port 9.6 kBit/s). The first topology strongly resembled stars. The central hub produced the broadcast. The fact of successful reception of the message was confirmed by an affirmative packet. The station repeated the message if necessary. The technology completely resolved the issue of collisions. The use of addressing simplified the resolution of any conflicts. Transmission and reception were carried out simultaneously: any failed attempt (collision) obliged the node to wait before starting a repeat session.

ALOHA was the first to use broadcast broadcasting, which is now the basis for creating Ethernet networks. The first government communications (ARPANET) sent packets strictly between two nodes. The absence of the need to capture a token significantly simplified both the implementation of the protocol and the equipment used.

• The channel was called a random access line.

The new technology quickly captured the minds of developers, serving as the basis for the creation of Ethernet, Wi-Fi, satellite communications, ARDIS, CDPD, GSM, Mobitex networks. A significant drawback of the first implementation is the incomplete use of the channel resource, since there is no way to prevent collisions. Mobile operator I liked the concept too. Signaling of 1G networks is partially implemented with ALOHA.

The random access technique is familiar to European GSM developers, who set the local fashion for mobile communications. Auxiliary channels helped transmit SMS (2G) and even served as a reliable means of delivering Internet packets (GPRS).

Ad-hoc mode

Later they released a version of the protocol for interacting clients directly, bypassing the star base station (Access Point). The concept was first proposed (1996) by Chai To and implemented (IEEE 802.11a) by the Lucent WaveLAN module in the IBM ThinkPads line. The original plan was to cover a one-mile radius. The attempt was a success, noted by Mobile Computing magazine (1999).

Formally, ad-hoc became part of the standard only in 2002. Today the technology is ready to seriously compete with Wi-Fi Direct. Networks devoid of routers immediately fell in love with gamers. The corresponding options help “virtual” access points share Internet access.

Attention! Microwave radiation is harmful to the user's health.

IEEE 802.11

Today Wi-Fi uses several bands:

1. 900 MHz.
2. 2.4 GHz.
3. 3.6 GHz.
4. 5 GHz.
5. 60 GHz.

The basic version dates back to 1997, but the length of previous developments covers over 10 years. The first version of IEEE 802.11a, which is still in use today, appeared two years later. Classified military technologies prevented civilians from taking advantage of science-intensive concepts. The beginning of Perestroika of the USSR in 1985 allowed the FCC committee to develop an ISM band frequency plan, allowing the use of dedicated bands by doctors and industry. For a long time the area was limited to specific uses.

In 1991, American giants AT&T and NCR Corporation offered the Netherlands the use of wireless cash registers. The data transmission technology (1-2 Mbit/s) is called WaveLAN. The 1997 IEEE 802.11 version is very similar to the store version:

• Two speeds (1-2 Mbit/s).
• Forward error correction technology.
• Three options for implementing the physical layer: infrared channel (only 1 Mbit/s), pseudo-random frequency tuning of the radio channel, direct sequence spread spectrum method.

Eliminating the bugs took 2 years, and now the capabilities of the 1997 project are completely outdated.

Father of Wi-Fi

Vic Hayes was a member of the standardizing organization for 10 years before the introduction of the IEEE 802.11a protocol. This allows historians to call the mentioned person the father of Wi-Fi. The main feature was the introduction of orthogonal frequency division multiplexing. The 5.8 GHz band was initially proposed. A similar technology is described in section 18 of the 2012 release, covering the speed range of 1.5 - 54 Mbit/s. Although the original concept has changed significantly, manufacturers still use the term IEEE 802.11a to describe the characteristics of 5.8 GHz equipment.

"Thanks" to mistakes real speed the first implementation rarely exceeded 20 Mbit/s. A significant advantage was the use of a low-value frequency range, but the peculiarities of microwave propagation greatly reduced the range of action of new systems. The first version of the protocol is much inferior to b/g. Theoretically, there is almost zero permeability through the walls. In practice, option b exhibits similar shortcomings. Imitating others wireless channels,IEEE 802.11a is susceptible to interference. The disadvantage is compensated by the low signal permeability (which means there is little chance of crossing the neighbor’s router).

The basis for creating a channel is 52 orthogonal subcarriers. Supported data rates: 48, 36, 24, 18, 12, 9, 6 Mbit/s. 12-13 non-overlapping channels have been identified. Implementation is highly dependent on country legislation. Some states allow more than 24 channels within the 5.47-5.725 GHz band. Conflicts with b are completely excluded, since the order of frequencies is different.

Parent patent

Although Vic Chase is idolized by the owners wireless devices, the new invention became possible thanks to the presence of patents in 1992, 1996. Australian astronomer John O'Sullivan and Co. (Graham Daniels, Terence Percival, John Dean) developed a key principle as part of a failed CSIRO program, described by experts as:

• A failed experiment to detect exploding black holes comparable in size to atomic ones.

Therefore, serious researchers still give parental rights to the specified group of space explorers. As of April 2009, CSIRO had received over $1 billion from 14 companies willing to improve the technology. This became the reason for the raider seizure of the title of the creator of the technology. If you want to work via Wi-Fi, you need permission from the monopolist. Capital inflows continue. American companies paid another 220 million to the homeland of the kangaroo (2012) for the right to use the technology.

This is interesting! The Test Bed local network was selected as a participant in the national exhibition of the History of 100 World Objects.

Development

Generation B has surpassed the capabilities of cash registers fivefold. The connection provided a bitrate of 11 Mbit/s. It was this state of affairs that ensured massive commercial success, and 1999 is considered the year of the creation of the world-famous Wi-Fi Alliance organization. The profits were shared by a dozen large companies:

1. 3Com.
2. Nokia.
3. Zebra Technologies.
4. Aironet.
5. Harris Semiconductor.

The venture was helped by numerous sponsors (more famous ones): Apple, Samsung, LG, Microsoft, Qualcomm, Sony. The organization was engaged in certification and testing. In fact, she acted as a trendsetter in the industry. The IEEE members split off in 1999 and began calling themselves WECA. The name Wi-Fi Alliance was born in 2002. Now the headquarters is located in Austin (USA), Texas, the organization has over 550 member companies.

Certification

A company wishing to produce equipment provides prototypes to the Alliance. Wi-Fi Alliance members are the full rights holders of the trademark and logo. Electromagnetic compatibility, package structure, security protocols, quality, and energy management modes are tested. Interoperability with previously certified devices is assessed. The set is starting standard applications. The three pillars of receiving a positive assessment are:

1. Successful interaction with any class devices.
2. Availability of backward compatibility. A necessary measure to ensure that end users do not need to constantly upgrade hardware.
3. Degree of accounting for innovations. The committee constantly publishes the latest fashion. The ability of the manufacturer to correctly grasp the voice of progress is considered an advantage.

There are mandatory and optional certifications. In addition, the organization is engaged in related technologies: Wi-Fi Direct, Wi-Fi Aware.

Future

Data transfer speeds are constantly increasing. The 2016 version combines basic capabilities 5 implementations at once:

The ac variant surpassed the technical capabilities of wired Ethernet for the first time. For this purpose, a carrier frequency of 5 GHz, a channel width of up to 160 MHz, and parallel transmission of packets by multiple nodes (MIMO) are used. The modulation level reached 256 QAM. The total speed of implementation in 2013 (channel width 80 MHz, frequency 5 GHz) reached 1.3 Gbit/s. Devices designed for the 160 MHz band of the “second wave” generation will transmit 4 streams simultaneously.

Ad will introduce the 60 GHz (millimeter wave) carrier. Since the value is significantly higher than the established standard, products are supposed to be marked with a WiGig sticker. However, certification is carried out by the good old Wi-Fi Alliance. A peak throughput of 7 Gbps is expected. The first commercial router was announced (January 2016) by TP-Link.

The af implementation intended to cover the “white spots” of the television band (54-790 MHz). Cognitive radio technologies will transmit information about the level of interference to the base station. The hardware will independently determine its own location, adjusting the broadcast parameters in accordance with local legislation.

The physical layer is formed by orthogonal frequency division multiplexing. The protocol is a logical continuation of IEEE 802.11ac. Relatively low frequencies television range will significantly increase the range. Small channel width (6-8 MHz) allows flexible adjustment specifications organized communication channel.

The range is characterized by comparatively low speeds, however, the use of simultaneous transmission of 4 frequency channels by four antennas will allow you to reach the limit of 426-568 Mbit/s (depending on the channel width).

In addition to the above, the 2016 version eliminates certain outdated functions, others are marked as “superfluous” (will be removed later). Information structure The document has a high degree of orderliness.

What is WiFi?

WiFi - wireless way connections based on everything we know electromagnetic radiation. The WiFi signal is classified as radio waves, respectively, it has the same properties, characteristics and behavior. Radio waves, in turn, obey almost the same physical laws as light: they propagate in space at the same speed (almost 300,000 kilometers per second), are subject to diffraction, absorption, attenuation, scattering, etc.

The main characteristics of a radio wave, and therefore a WiFi signal, are its length and frequency (frequency range). The last parameter means the alternating current frequency required to produce a wave of the required length and is used to classify radio waves. Another definition of frequency is the number of waves passing through a specific point in space per second.

There is a distribution of radio waves by range, depending on frequency, approved by the International Telecommunication Union (ITU, English abbreviation - ITU).

The scope of radio waves depends on the frequency range. This could be television, radio, mobile connection, radio relay communication, etc. In general, the radio frequency airwaves are quite busy: the use of all ranges is literally scheduled:

Including this WiFi wireless connection. It uses decimeter and centimeter waves of ultra-high and ultra high frequency(UHF and microwave) in the frequency ranges of 2.4 GHz, 5 GHz and other rarely used: 900 MHz, 3.6 GHz, 10 GHz, 24 GHz.

The main advantage of WiFi communicationreflected in its second name -wireless connection. It is the absence of wires, coupled with the ever-increasing data transfer speed, that is key point when choosing this connection method.

If we are talking about home users- wireless communication is convenient, it allows you not to be tied to a specific place in the apartment to access the Internet.

If we're talking about corporate communications, about provider services, then sometimes laying a cable for data transmission is expensive, impractical or even impossible. For example, you need to distribute the Internet in the private sector, lay a backbone channel through a gorge, to a remote locality, etc. In this case, WiFi comes to the rescue. The problem area is overcome using a wireless channel.

Relationship between WiFi signal frequency and wavelength

Wavelength characteristics are relatively rarely used in WiFi equipment parameters. However, sometimes, to understand the physical properties and behavior of a wireless signal under various conditions, it is good to understand the relationship between frequency and wavelength of radio waves.

General rule: The higher the frequency, the shorter the wavelength. And vice versa.

Formula for calculating wavelength:

WiFi signal wavelength (meters)= Speed ​​of light (in m/sec) / Signal frequency (in hertz).

Speed ​​of light in m/sec = 300,000,000.

After simplifying the formula we get: Wavelength in meters = 300/ Frequency in MHz.

WiFi signal properties

Absorption.

The main condition for creating a wireless link over a distance of more than a hundred meters is direct visibility between equipment installation points. Simply put, if we are standing next to one WiFi access point, then our gaze directed towards the second point should not rest against a wall, forest, multi-story building, hill, etc. ( That's not all, you also need to take into account interference in the Fresnel Zone, but more on that in another article.)

Such objects simply reflect and absorb WiFi signal, if not all, then the lion's part of it.

The same thing happens indoors, where the signal from WiFi router or the access point goes through walls to other rooms/to other floors. Each wall or ceiling “takes away” a certain amount of efficiency from the signal.

On a short distance, for example, from a room router to a laptop, the radio signal still has a chance, having overcome the wall, to still reach the target. But over a long distance of several kilometers, any such weakening significantly affects the quality and range of WiFi communication.

The percentage of Wi-Fi signal degradation when passing through obstacles depends on several factors:

• Wavelengths. In theory, the longer the wavelength (and lower the Wi-Fi frequency), the greater the penetrating power of the signal. Accordingly, WiFi in the 2.4 GHz range has b O greater penetrating power than in the 5 GHz range. In real conditions, the implementation of this rule very closely depends on the structure and composition of the obstacle the signal passes through.
• Obstacle material , more precisely, its dielectric properties.

*Effective distance percentage - this value means what percentage of the initially calculated range (in open areas) the signal will be able to travel after overcoming the obstacle.

For example, if in an open area the Wi-Fi signal range is up to 200 meters, then after passing through an untinted window it will decrease to 140 meters (200 * 70% = 140). If the next obstacle to the same signal is a concrete wall, then after it the range will be a maximum of 21 meters (140 * 15%).

Note that water and metal are the most effective WiFi absorbers, since they are electrical conductors and “take” a large number of signal energy. For example, if at home there is an aquarium on the Wi-Fi path from the router to your laptop, then there will almost certainly not be a connection.

This is why during rain and other “wet” precipitation there is a slight decrease in the quality of the wireless connection, since water droplets in the atmosphere absorb the signal.

This factor partially affects the attenuation of WiFi transmission in the foliage of trees, since they contain a large percentage of water.

• Angle of incidence of the beam on the obstacle. In addition to the material of the obstacle through which the Wi-Fi signal passes, the angle of incidence of the beam is also important. So, if a signal passes through an obstacle at a right angle, it will provide less loss than if it hits it at an angle of 45 degrees. It's even worse if the signal passes through the obstacle at a very sharp angle. In this case, roughly speaking, you can safely multiply the wall thickness by 10 and calculate WiFi transmission losses according to this value.

Avoiding obstacles.

Scientifically, this behavior of a WiFi beam is called diffraction, although in reality the concept of diffraction is much more complex than simply “bending around obstacles.”

In general, we can derive the rule - the shorter the wavelength (higher the frequency), the worse it bends around obstacles .

This rule is based on a well-known physical property of a wave: if the size of an obstacle is smaller than the wavelength, then it bends around it. In general, it logically follows from this that the shorter the wavelength, the fewer options remain for obstacles that it can, in principle, bypass, and therefore it is assumed that its envelope ability is worse.

In practice, bending means less dispersion of the wave as a beam of energy around an obstacle, and less signal loss.

Let's take the popular frequencies 2.4 GHz (wavelength 12.5 cm) and 5 GHz (wavelength 6 cm). We see confirmation of the rule in the example of passing through a forest area. The standard sizes of leaves, trunks, and branches of trees, on average, will be less than 12.5 cm, but more than 6 cm. Therefore, a 5 GHz WiFi signal when passing through dense foliage will be “lost” almost completely, while 2, 4 GHz will do better.

Therefore, WiFi equipment operating in the 900 MHz band is used in conditions where there is no direct visibility of the signal - its wavelength is 33.3 cm, which allows it to go around more obstacles. However, one must take into account the size of the expected obstacles and understand that a 900 MHz signal will not be able to “bypass” a concrete wall located perpendicular to the direction of the signal. Here the penetrating abilities of the wave will already play a role, which, as we have already said, are quite good for low-frequency signals.

This is also why for normal operation wireless equipment, using a frequency of 24 GHz (wavelength 1.25 cm), absolutely clear visibility is necessary, because all obstacles larger than a centimeter will reflect and absorb the signal.

As we have already mentioned, the water content of the leaves, as well as the wavelength, also play a role in the passage of the signal through the forest.

Natural attenuation.

How far could a WiFi signal travel if it had ideal line-of-sight conditions? In any case, not indefinitely, because the greater the range of the wireless “flight”, the more the signal attenuates on its own. This happens for 2 reasons:

The earth's surface absorbs part of the signal energy. The higher the WiFi frequency, the more intense the absorption.

The WiFi signal, even from the most narrowly directed antenna, is not distributed in a straight line, but in a beam. Accordingly, the further the distance, the wider the beam becomes, the less signal power per unit area, and the less signal energy reaches the receiving antenna.

Signal reflections.

A WiFi signal, like any radio wave, like light, is reflected from surfaces and behaves similarly. But there are nuances here - some surfaces will absorb the signal (fully or partially), and some will reflect (fully or partially). This depends on the surface material, its structure, the presence of irregularities on the surface and the WiFi frequency.

Uncontrolled signal reflections degrade its quality. Partially - due to the loss of the total signal energy (to put it simply, “not everything reaches the receiving antenna” or reaches it after reflections, with delays). Partly due to interference with a negative influence, when the waves overlap in antiphase and weaken each other.

Interference can also have a positive effect if WiFi waves overlap each other in the same phases. This is often used to boost signal strength.

Data density.

The WiFi frequency also affects another important parameter - the amount of data transferred. There is a direct connection here - the higher the frequency, the more data per unit of time can be transmitted. Perhaps this is why the first high-performance RRL from Ubiquiti - as well as its more powerful modification - were released at 24 GHz.

Why is it difficult to give a definite answer: how far will the WiFi signal be transmitted by the equipment?

The physical properties and behavior of radio waves in the surrounding world are quite complex. You cannot take one parameter and use it to calculate the range of a wireless signal. In each specific case, the range will be influenced by various environmental factors:

• Signal absorption by obstacles, the earth's crust, and the surface of water bodies.
• Diffraction and signal scattering due to obstacles in the path.
• Signal reflections from obstacles, ground, water and the resulting interference waves. 2.4 GHz and 5 GHz.

  The main differences between 2.4 GHz and 5 GHz:

  2.4 GHz. Wavelength 12.5 cm. Refers to decimeter waves of ultra-high frequency (UHF).

  • In real conditions, the signal range is shorter due to the wider Fresnel zone, which is most often not compensated by the fact that the signal at this frequency is less susceptible to natural attenuation.
  • Better penetration of small obstacles, such as dense forested areas, due to good penetration and obstacle avoidance.
  • There are fewer relatively non-overlapping channels (3 in total), which means “traffic jams” - crowded airtime, and as a result - poor communication.
  • Additional noise pollution of the airwaves by other devices operating at the same frequency, including mobile phones, microwaves, etc.

  5 GHz. Wavelength 6 cm. Refers to centimeter waves of ultra-high frequency (microwave).

  • Larger number of relatively non-overlapping channels (19).
  • B OGreater data capacity.
  • Longer signal range due to the fact that the Fresnel Zone is smaller.
  • 5 GHz waves overcome obstacles such as tree foliage and walls much worse than 2.4.

  Ranges 900 MHz, 3.6 GHz, 10 GHz, 24 GHz For us it’s more exotic, but they can be used:

  For work in conditions where standard ranges are densely occupied.

  If you need to create wireless connection between two points in the absence of direct visibility (forest and other obstacles). This applies to a frequency such as 900 MHz (in our country it must be used with caution, since cellular operators operate on it).

  If you do not need to obtain a license from regulatory authorities to use the frequency. This advantage is often found in presentations of foreign manufacturers, but for Ukraine this is not entirely relevant, since the licensing conditions in our country are different.

  IEEE is working on the adoption of new standards and, accordingly, the use of other frequencies for WiFi. It is possible, for example, that in the near future the 60 GHz band will also be used for wireless transmission.Just as it is possible that in the future some frequencies currently owned by WiFi will be “squeezed out” in favor of, for example, cellular operators.

  
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Good day.

Today, any modern user has an idea of ​​what Wi-Fi is. But do you know everything about him? In this article you will find an explanation of this term, information about its appearance, standards, advantages and disadvantages.

Wi-Fi: what is it?

Wi-Fi is a method of transmitting data over the Internet over short distances without the use of wires. More precisely, Wi-Fi is a standard for broadband communication equipment, on the basis of which local networks Wireless LAN.

If you look deeply, this term is not the Internet, which many people think it is. It displays the trademark of the company that came up with this technology - the Wi-Fi Alliance. It is developed based on the IEEE 802.11 standard, and any device that complies with it can be tested by this company, as a result of which it will receive a certificate and the right to apply the Wi-Fi logo.

Explanation of the term

The abbreviation Wi-Fi is derived from Hi-Fi, which in English stands for High Fidelity - high precision. The abbreviations are similar in sound and essence, so, according to the developers, users should have a positive association when meeting a new term.

The first two letters in it hid the already mentioned word Wireless, which in translation means wireless. However, now the concept of Wi-Fi has taken root in our society so much that it is no longer considered an abbreviation, but is an independent term.

Scope of use

The technology was invented for providing the Internet in places where it is not possible to run wires: for example, houses remote from the city, buildings of historical value, etc. However, now Wi-Fi is used everywhere. With its help, various companies and establishments offer free Internet access to attract customers and show their modernity.

Most people install such an access point at home. Since it allows you to connect to the network from different gadgets while within the coverage area. Thus, thanks to Wi-Fi, you are not tied to one place, as is the case with a desktop computer to which an Internet cable is connected.

When answering the question of what Wi-Fi is, it is important to understand. Wi-Fi is not the Internet as a type, but only a way to connect to a device that already has access to the Internet. Wi-Fi technology is similar to (communication using radio waves). It works approximately the same, but is applied in a different direction.

Organization of a wireless network

In order for you to be able to use wireless Internet, you will need a device with an appropriate receiver (smartphone, tablet, laptop, modem for a regular computer), a router, and an established connection with a service provider.

They are provided by individual organizations or mobile operators. Having signed an agreement with them, you install a router at home or in another place, which has a built-in radio module that receives and sends out a signal. A similar device should be in the gadget from which you will access the Internet.

As a rule, the cable is supplied to the provider. But in places where this is not possible, service providers transmit the Internet to the client’s access point also via Wi-Fi. But for this, their router must be located in a nearby area. Which is much more powerful than those installed by ordinary users.

By the way, instead of a router, you can use your smartphone, which will act as a modem if you use the Internet mobile operator. This connection is called tethering or teasing.

Network without a router

It is worth highlighting the standard Wi-Fi connections Direct. Which allows two or more devices to communicate without the mediation of a router. When connecting for the first time, the gadgets themselves determine which one will be the access point.

This technology is relevant in cases where, for example, you need to transfer a document from a computer to a printer for printing. Or you want to view photos from your phone on a large monitor without the help of a wire. Thus, with using Wi-Fi Direct you can organize a wireless home network.

Pros and cons of Wi-Fi

The advantages are:

• The absence of wires allows you to expand the scope of the Internet and reduce the cost of connection.
• There is no binding to one place.

• You can go online not only from desktop computer, but also from a mobile device.
• Several users can connect to the Internet at once.
• Wide distribution and wide range of devices certified by the Wi-Fi Alliance.
• Requires a password when connecting a new device, which ensures the security of the connection.

Now about the disadvantages:

• There is no connection to a place - yes. But there is a connection to the signal source.
• Due to the fact that Bluetooth devices also operate at the 2.4 GHz frequency of the IEEE 802.11 standard, microwaves and other equipment, communication quality may be degraded.
• Although the signal penetrates furniture and walls, obstacles still somewhat reduce its power.
• Bad weather conditions also degrade network performance.

As you already know, the basic Wi-Fi connection standard is IEEE 802.11, which defines a set of protocols for the lowest data transfer rates. It has many subspecies, so it would take a long time to list them all.

I will name the main ones:

• 11b. Appeared in 1999. Describes a higher speed than the basic one, but still insufficient by today's standards - 11 Mbit/s. The safety of the standard is also low. Protected by WEP encryption protocol, which does not have good functionality. Operates at a frequency of 2.4 GHz. Nowadays it is practically not used, except for equipment that does not support other standards.
• 11a. Released in the same year as "b", but differs in frequency (5 GHz) and speed (maximum 55 Mbit/s).
• 11g. It replaced the two previous versions in 2003. Is more perfect. His average speed is 55 Mbit/s, and when using devices that support SuperG or True MIMO technologies, it can reach 125 Mbit/s. The level of security is also enhanced thanks to the WPA and WPA2 protocols.
• 11n. The most modern standard, which appeared in 2009. Operates on both 2.4 GHz and 5 GHz, so is compatible with all the options above. It has a high level of security, as it is encrypted with the same protocols as “g”.

That's all about what Wi-Fi is.

Enjoy your Internet surfing.

It was created in 1998 at the CSIRO Radio Astronomy Laboratory in Australia. The creator of the wireless data exchange protocol is engineer John O'Sullivan. The term "Wi-Fi" was originally coined as a play on words with a "hint" to Hi-Fi (High Fidelity). Despite the fact that at first some press releases included the phrase “Wireless Fidelity” (or “wireless accuracy”), at the moment such wording is not used, and accordingly the term “Wi-Fi” is not deciphered in any way. How does the wireless data transfer standard, Wi-Fi, work? About this in today's episode!

The principle of Wi-Fi operation is based on the use of radio waves, and the data exchange itself resembles radio communications. Typically, a Wi-Fi network diagram contains at least one access point and at least one client. It is also possible to connect two clients when the access point is not used, and the clients are connected via network adapters"directly". Adapters on each computer convert digital data into radio signals that are sent to other network devices. They also convert incoming radio signals from external network devices into digital data. Radio transmitters and receivers on the same Wi-Fi network operate at the same frequencies and use the same type of data modulation into radio waves.

To connect to a network, you need to know the network ID. The access point transmits it using special signaling packets at a speed of 0.1 Mbit/s every 100 milliseconds. Therefore, 0.1 Mbps is the lowest Wi-Fi data transfer speed. Knowing the network ID, the client can find out whether a connection to a given access point is possible. When two access points with identical IDs come within range, the receiver can choose between them based on signal strength data. Wi-Fi standard gives the client complete freedom in choosing connection criteria.

Wi-Fi standards are constantly improving. In January 2014, the IEEE (I-triple I) 802.11ac standard was adopted, the data transfer speed of which can reach several Gbit/s. There is also the IEEE 802.22 standard, intended for use in rural areas and allowing you to receive data within a radius of 100 km at speeds up to 22 Mbit/s.