Wireless data speed standards. Description of the subject area

At the beginning of the development of the Internet, the network connection was carried out network cable, which had to be carried out indoors in such a way that it would not interfere. They secured it and hid it as best they could. Old computer furniture still has holes for cable routing.

When wireless technologies and Wi-Fi networks have become popular, the need for running the network cable and hiding it has disappeared. Wireless technology allows you to receive the Internet “over the air” if you have a router (access point). The Internet began to develop in 1991, and closer to 2010 it had already become especially popular.

What is Wi-Fi

This is a modern standard for receiving and transmitting data from one device to another. In this case, the devices must be equipped with radio modules. Such Wi-Fi modules are included in many electronic devices and technology. At first they were included only in a set of tablets, laptops, and smartphones. But now they can be found in cameras, printers, washing machines, and even multicookers.

Principle of operation

To access Wi-Fi, you must have an access point. Today, such a point is mainly a router. This is a small plastic box, on the body of which there are several sockets for connecting the Internet via wire. The router itself is connected to the Internet via a network wire called twisted pair. Through the antenna, the access point distributes information from the Internet to the Wi-Fi network, through which various devices with a Wi-Fi receiver receive this data.

A laptop, tablet or smartphone can work instead of a router. They must also have an Internet connection via mobile communications via SIM card. These devices have the same data exchange principle as a router.

The method of connecting the Internet to the access point does not matter. Access points are divided into private and public. The former are used only for use by the owners themselves. The latter provide Internet access for money or free of charge to a large number of users.

Public hot spots are most often found in public places. It is easy to connect to such networks while being on the territory of this point or near it. In some places it requires you to log in, but you are offered a password and login if you use paid services of this establishment.

In many cities, their entire territory is completely covered by a Wi-Fi network. To connect to it, you need to pay for a subscription, which is not expensive. Consumers are provided with both commercial networks and free access. Such networks are built by municipalities and private individuals. Small networks for residential buildings, public institutions become larger over time, use peering agreements to interact freely with each other, work on voluntary assistance and donations from other organizations.

City authorities often sponsor similar projects. For example, in France, some cities provide unlimited Internet access to those who give permission to use the roof of the house to install a Wi-Fi antenna. Many universities in the west allow online access to students and visitors. The number of hotspots (public points) is growing steadily.

Wi-Fi standards

IEEE 802.11– protocols for low data rates, the main standard.

IEEE 802.11a– is incompatible with 802.11b, for high speeds, uses 5 GHz channels. Capable of transmitting data up to 54 Mbit/s.

IEEE 802.11b– standard for fast speeds, channel frequency 2.4 GHz, throughput up to 11 Mbit/s.

IEEE 802.11g– speed equivalent to standard 11a, channel frequency 2.4 GHz, compatible with 11b, bandwidth up to 54 Mbit/s.

IEEE 802.11n– the most advanced commercial standard, channel frequencies 2.4 and 5 GHz, can work in conjunction with 11b, 11g, 11a. The highest operating speed is 300 Mbit/s.

To understand in more detail the operation of various wireless communication standards, consider the information in the table.

Using a Wi-Fi network

The main purpose of wireless communications in everyday life is to access the Internet to visit websites, communicate online, and download files. There is no need for wires. Over time, the spread of access points throughout cities is progressing. In the future, it will be possible to use the Internet using a Wi-Fi network in any city without restrictions.

Such modules are used to create a network within a limited area between several devices. Many companies have already developed mobile applications for mobile gadgets that make it possible to exchange information via Wi-Fi networks, but without connecting to the Internet. This application organizes a data encryption tunnel through which information will be transmitted to the other party.

Information exchange is carried out much faster (several tens of times) than via Bluetooth as we know it. The smartphone can also act as a gaming joystick in conjunction with game console, or a computer, perform the functions of a remote control for a TV running via Wi-Fi.

How to use a Wi-Fi network

First you need to buy a router. You must insert the power cord into the yellow or white socket and configure it according to the included instructions.

On receiving devices with a Wi-Fi module, turn it on and search for required network and make a connection. The more devices connected to one router, the lower the data transfer speed will be, since the speed is equally divided among all devices.

The Wi-Fi module looks like a regular flash drive; the connection is made via a USB interface. It has a low cost. On mobile device you can enable an access point that will act as a router. When a smartphone distributes the Internet via an access point, it is not recommended to overload the processor on it, that is, it is not advisable to watch videos or download files, since the speed is divided between the connected and the distribution device on a residual basis.

Wi-Fi technology makes it possible to access the Internet without a cable. The source of such a wireless network can be any device that has a Wi-Fi radio module. The propagation radius depends on the antenna. WITH using Wi-Fi create groups of devices, and you can also simply transfer files.

AdvantagesWi— Fi

• No wiring required. Due to this, savings are achieved on cable laying, wiring, and time is also saved.
• Unlimited expansion of the network, with an increase in the number of consumers and network points.
• There is no need to damage the surfaces of walls and ceilings for laying cables.
• Globally compatible. This is a group of standards that works on devices manufactured in different countries.

FlawsWi— Fi

• In neighboring countries, the use of a Wi-Fi network without permission is allowed to create a network in premises, warehouses, and production. To connect two neighboring houses with a common radio channel, an application to the supervisory authority is required.
• Legal aspect. Different countries have different attitudes towards the use of Wi-Fi range transmitters. Some states require all networks to be registered if they operate on premises. Others limit transmitter power and certain frequencies.
• Communication stability. Routers installed at home, of common standards, distribute a signal over a distance of 50 meters inside buildings, and 90 meters outside the room. Many electronic devices and weather factors reduce the signal level. The distance range depends on the frequency of operation and other parameters.
• Interference. In cities, there is a significant density of router installation points, so problems often arise connecting to a point if there is another point nearby that operates at the same frequency with encryption.
• Manufacturing parameters. It often happens that manufacturers do not adhere to certain device manufacturing standards, so access points may have unstable operation, and the speed differs from the declared one.
• Electricity consumption. A sufficiently large energy consumption, which reduces the charge of batteries and accumulators, increases the heating of the equipment.
• Safety. Data encryption using the WEP standard is unreliable and easy to crack. The WPA protocol, which is more reliable, is not supported by access points on older equipment. The WPA2 protocol is considered the most reliable today.
• Limitation of functions. During the transmission of small packets of information, a lot of official information is attached to them. This makes the connection quality worse. Therefore, it is not recommended to use Wi-Fi networks to organize IP telephony using the RTP protocol, since there is no guarantee of communication quality.

Features of Wi-Fi and Wi MAX

Wi-Fi network technology was primarily created for organizations to move away from wired communications. However, this wireless technology is now gaining popularity in the private sector. The types of wireless connections Wi-Fi and Wi MAX are related in the tasks they perform, but they solve different problems.

Wi MAX devices have special digital communication certificates. Complete protection of data streams is achieved. Based on Wi MAX, private confidential networks are formed, which make it possible to create secure corridors. Wi MAX transmits the necessary information, despite the weather, buildings and other obstacles.

This type of communication is also used for high quality video communication. We can highlight its main advantages, consisting of reliability, mobility, and high speed.

Among the most well-known wireless technologies are: Wi-Fi, Wi-Max, Bluetooth, Wireless USB and a relatively new technology - ZigBee, which was originally developed with a focus on industrial applications.

Figure 1 - Wireless standards

Each of these technologies has unique characteristics (see Figure 2) that define their respective applications.

Let us try to formulate the requirements that communication technology must satisfy for its successful application in industry. Let's say there is a certain industrial facility consisting of several electric pump drives, a device for collecting information from various technological sensors, for example, pressure, temperature, flow sensors, including those installed remotely, an operator console and a control room. The pumps are controlled from the operator's console, and the control room continuously monitors the system.

Figure 2 – Main characteristics of popular wireless communication standards

Obviously, the best option from the point of view of simplicity and convenience would be to unite all devices involved in information exchange into a single information network operating in the same standard. Since devices of varying complexity and, accordingly, cost can be installed at an industrial facility, the software and hardware complex that provides access for each device to the information network must be quite cheap. Also, communication technology must provide the necessary range and speed of connections. And if we take into account that an industrial installation can be supplemented with new components (for example, another pump or an information collection device), then the communication technology requires the ability to scale. And, of course, communication technology must ensure the reliability and security of information transfer. The considered case is a typical example of a distributed control system, where each of the nodes, being intelligent, performs its own local automation task, and the connections between the nodes are “weak” - mainly operational control commands and changes in settings of controlled variables, messages about the state of equipment are transmitted over the network and technological process. Each node, for example, based on a frequency converter, has its own communication channels with process sensors, and there is no need to transmit large data streams.

Analysis of wireless technologies shows that high-speed technologies Wi-Fi, Wi-Max, Bluetooth, Wireless USB are intended primarily for servicing computer peripherals and multimedia devices. They are optimized for transmitting large volumes of information at high speeds, operate mainly on a point-to-point or star topology and are unsuitable for implementing complex branched industrial networks with a large number of nodes. On the contrary, ZigBee technology has rather modest data transfer rates and distances between nodes, but has the following important advantages from the point of view of industrial use.

1.It is focused on primary use in distributed multi-microprocessor control systems with the collection of information from smart sensors, where the issues of minimizing energy consumption and processor resources are decisive.

2. Provides the ability to organize self-configuring networks with a complex topology, in which the message route is automatically determined not only by the number of operational or currently turned on/off devices (nodes), but also by the quality of communication between them, which is automatically determined at the hardware level.

3. Provides scalability - automatic commissioning of a node or group of nodes immediately after power is supplied to the node.

4. Guarantees high network reliability by selecting an alternative message transmission route in the event of outages/failures in individual nodes.

5.Supports built-in hardware AES-128 message encryption mechanisms, eliminating the possibility of unauthorized access to the network.

Organization of a ZigBee network

ZigBee is a relatively new wireless communication standard that was originally developed as a means for transmitting small amounts of information over short distances with minimal power consumption. In fact, this standard describes the rules for the operation of a hardware and software complex that implements wireless interaction of devices with each other.

The ZigBee protocol stack is a hierarchical model built on the principle of the seven-layer model of data transfer protocols in open OSI (Open System Interconnection) systems. Stack includes levels IEEE standard 802.15.4, responsible for implementing the communication channel, and software network and application support layers defined by the ZigBee specification . The implementation model of the ZigBee communication standard is presented in Figure 3.

Figure 3 – Multi-level model of the ZigBee communication standard

The IEEE 802.15.4 standard defines two lower layers of the stack: the media access layer (MAC) and the physical propagation layer (PHY), that is, the lower protocol layers wireless transmission data . The alliance defines the software layers of the ZigBee stack from the Data Link Control to the ZigBee Profiles. Reception and transmission of data over a radio channel is carried out at the PHY physical level, which determines the operating frequency range, modulation type, maximum speed, number of channels (Table 1). The PHY layer activates and deactivates the transceiver, detects the energy of the received signal on the working channel, selects a physical frequency channel, indicates the quality of communication when receiving a data packet, and evaluates free channel. It is important to understand that 802.15.4 is a physical radio (radio transceiver chip) and ZigBee is a logical network and software stack that provides security and routing functions.

Next in the structure of the ZigBee stack is the IEEE 802.15.4 MAC medium access control layer, which performs entry and exit from the network of devices, network organization, generation of data packets, implementation of various security modes (including 128-bit AES encryption), 16- and 64-bit bit addressing.

The MAC layer provides various network access mechanisms, support for network topologies from point-to-point to multi-cell network, guaranteed data exchange (ACK, CRC), supports streaming and packet data transmission.

To prevent unwanted interactions, it is possible to use time division based on the CSMA-CA (Carrier Sense Multiple Access and Collision Avoidance) protocol.

ZigBee time division is based on the use of a synchronization mode in which slave network devices, which are in a “sleep” state most of the time, periodically “wake up” to receive a synchronization signal from the network coordinator, which allows devices inside the local network cell to know at what point in time carry out data transfer. This mechanism, based on determining the state of the communication channel before the start of transmission, can significantly reduce (but not eliminate) collisions caused by data transmission by several devices simultaneously. The 802.15.4 standard is based on half-duplex data transmission (a device can either transmit or receive data), which does not allow the CSMA-CA method to be used for collision detection - only for collision avoidance.

The stack specification provides three types of devices: coordinator, router, and end device. Coordinator initializes the network, manages its nodes, stores information about the settings of each node, sets the frequency channel number and network identifier PAN ID, and during operation can be a source, receiver and relay of messages. Router is responsible for choosing the delivery path for a message transmitted over the network from one node to another, and during operation can also be a source, receiver or relay of messages. If routers have the appropriate capabilities, they can determine optimized routes to a specific point and store them for later use in routing tables. End device does not participate in network management and message relaying, being only a source/receiver of messages.

Among the properties of ZigBee, special mention should be made of support for complex network topologies. It is due to this, with a relatively short maximum communication range of two nearby devices, that it is possible to expand the coverage area of ​​the network as a whole. This is also facilitated by 16-bit addressing, which allows more than 65 thousand devices to be combined into one network.

Figure 4 – ZigBee network topologies

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, monoblocks, TVs, computers - all our equipment supports a wireless Internet connection, without which it is no longer possible to imagine the life of a modern person.

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

In order to choose a network suitable for 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 most in demand today: 802.11b, 802.11a, 802.11g and 802.11n. The manufacturer's most recent discovery was the 802.11ac modification, the performance of which is several times higher than the characteristics of modern adapters.

Is a senior certified technology wireless connection and is characterized by general accessibility. The device has very modest parameters:

• Information transfer speed - 11 Mbit/s;
• Frequency range - 2.4 GHz;
• The range 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 throughput. Therefore, despite the attractive price of this Wi-Fi connection, its technical component lags significantly behind more modern models.

802.11a standard

This technology is an improved version of the previous standard. The developers focused on the device’s throughput and clock speed. Thanks to such changes, this modification eliminates the influence of other devices on the quality of the network signal.

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

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

802.11g standard

The updated modification becomes a leader in today's standards wireless networks, since it supports work with the widespread 802.11b technology and, unlike it, has a fairly high connection speed.

• Information transfer speed - 54 Mbit/s;
• Frequency range - 2.4 GHz;
• Range of action - up to 50 meters.

As you may have noticed, the clock frequency has dropped to 2.4 GHz, but the network coverage has returned to its previous levels typical for 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 been on the market for a long time 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 speed is theoretically up to 480 Mbit/s, but in practice it is half as much;
• Frequency range - 2.4 or 5 GHz;
• Range of action - up to 100 meters.

Since this standard is still evolving, it has its own characteristics: it may conflict with equipment that supports 802.11n only because the device manufacturers are different.

Other standards

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

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

• 802.11h- prevents loss of signal quality due to the influence of meteorological equipment and military radars;
• 802.11i- improved version of protecting users’ personal information;
• 802.11k- monitors the load on a particular network and redistributes users to other access points;
• 802.11m- contains all corrections to 802.11 standards;
• 802.11p- determines the nature of Wi-Fi devices located within a range of 1 km and moving at speeds of up to 200 km/h;
• 802.11r- automatically finds a wireless network while roaming and connects mobile devices to it;
• 802.11s- organizes a full mesh connection, where each smartphone or tablet can be a router or connection point;
• 802.11t- this network tests the entire 802.11 standard, provides testing methods and their results, and sets requirements for the operation of the equipment;
• 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- this technology creates solutions to improve 802.11 modifications;
• 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 transmission.

The latest and most technologically advanced standard 802.11ac

802.11ac modification devices provide users with a completely new quality of Internet experience. Among the advantages of this standard, the following should be highlighted:

1. High speed. When transmitting data over the 802.11ac network, wider channels and higher frequencies are used, which increases the theoretical speed to 1.3 Gbps. In practice, throughput is up to 600 Mbit/s. In addition, an 802.11ac-based device transmits more data per clock 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 a 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 plasterboard walls. Interference that occurs during the operation of home appliances and the neighbor’s Internet does not in any way affect the operation of your connection.
3. Updated technologies. 802.11ac is equipped with the MU-MIMO extension, which ensures smooth operation of multiple devices on the network. Beamforming technology identifies the client's device and sends several streams of information to it at once.

Having become more familiar with all the Wi-Fi connection modifications that exist today, you can easily choose the network that suits your needs. Please remember 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, the number of devices equipped with it today is small. However, this is a very pressing problem and soon all modern equipment will switch to the 802.11ac standard. Don’t forget to take care of the security of your Internet access by installing a complex code on your Wi-Fi connection and an antivirus to protect your computer from virus software.

Wireless computer networks - is a technology that allows you to create computer networks, fully compliant with the standards for conventional wired networks (eg Ethernet), without the need for cabling. Microwave radio waves act as information carriers in such networks.

Wireless technologies - subclass information technologies, serve to transmit information over a distance between two or more points, without requiring them to be connected by wires. Infrared radiation, radio waves, optical or laser radiation can be used to transmit information.

Currently, there are many wireless technologies, most often known to users by their marketing names, such as Wi-Fi, WiMAX, Bluetooth. Each technology has certain characteristics that determine its scope of application.

Approaches to classification of wireless technologies

A short but concise way of classification can be to simultaneously display the two most significant characteristics of wireless technologies on two axes: maximum information transfer speed and maximum distance.

We propose to consider the first 3, most common, categories in more detail.

WPAN a wireless network designed to organize wireless communication between various types of devices in a limited area (for example, within an apartment, office workplace). The standards that define how a network operates are described in the IEEE 802.15 family of specifications. Let's consider the two most promising standards: Bluetooth and ZigBee.

Bluetooth— production specification for wireless personal area networks (WPAN). Bluetooth enables the exchange of information between devices such as personal computers(desktop, pocket, laptops), Cell phones, printers, digital cameras, mice, keyboards, joysticks, headphones, headsets on a reliable, free, universally available radio frequency for short-range communication.

Bluetooth allows these devices to communicate when they are within a radius of up to 200 meters from each other (range varies greatly depending on obstacles and interference), even in different rooms.
The operating principle is based on the use of radio waves. Bluetooth radio communication is carried out in the ISM band (Industry, Science and Medicine), which is used in various household appliances and wireless networks (licensing-free range 2.4-2.4835 GHz). Bluetooth uses Frequency Hopping Spread Spectrum (FHSS). The FHSS method is easy to implement, provides immunity to broadband interference, and the equipment is inexpensive.
According to the FHSS algorithm, in Bluetooth the carrier frequency of the signal changes abruptly 1600 times per second (in total, 79 operating frequencies with a width of 1 MHz are allocated, and in Japan, France and Spain the band already has 23 frequency channels). The sequence of switching between frequencies for each connection is pseudo-random and is known only to the transmitter and receiver, which synchronously switch from one carrier frequency to another every 625 μs (one time slot). Thus, if several receiver-transmitter pairs operate nearby, they do not interfere with each other. This algorithm is also an integral part of the system for protecting the confidentiality of transmitted information: the transition occurs according to a pseudo-random algorithm and is determined separately for each connection. When transmitting digital data and audio (64 kbit/s in both directions), different encoding schemes are used: the audio signal is not repeated (as a rule), and digital data will be retransmitted if a packet of information is lost.
The Bluetooth protocol not only supports point-to-point connection, but also point-to-multipoint connection.

ZigBee is the name of a set of upper-level network protocols using small, low-power radio transmitters based on the IEEE 802.15.4 standard. This standard describes wireless personal area networks (WPANs). ZigBee targets applications that require long runtimes battery life battery-powered and high data transmission security at low data rates.

The ZigBee 1.0 specification was ratified on December 14, 2004 and is available to members of the ZigBee Alliance. More recently, the ZigBee 2007 specification was posted on October 30, 2007. The first application profile, ZigBee Home Automation, was announced on November 2, 2007. ZigBee operates in the Industrial, Scientific, and Medical (ISM) radio bands: 868 MHz in Europe, 915 MHz in the US and Australia, and 2.4 GHz in most countries in the world (under most jurisdictions in the world). As a rule, ZigBee chips are commercially available, which are combined radio and microcontrollers with Flash memory sizes from 60K to 128K from manufacturers such as Jennic JN5148, Freescale MC13213, Ember EM250, Texas Instruments CC2430, Samsung Electro-Mechanics ZBS240 and Atmel ATmega128RFA1.

ZigBee can wake up (i.e. go from sleep to active) in 15 milliseconds or less, and the device's response latency can be very low, especially compared to Bluetooth, where the latency from sleep to active is typically up to three seconds . Since ZigBee is in sleep mode most of the time, power consumption can be very low, resulting in long battery life.

WLAN (Wireless Local Area Network)

This category of wireless network is designed to connect various devices to each other, similar to a LAN based on twisted pair or fiber optics, and is characterized by high data transfer rates over relatively short distances. The interaction of devices is described by the IEEE 802.11 family of standards, which includes more than 20 specifications.
In this regard, many people mistakenly do not see the difference between Wi-Fi and IEEE 802.11. Currently, Wi-Fi refers to a brand name that indicates that a particular device meets the 802.11a, 802.11.b, 802.11.g specifications.
Thus, the IEEE 802.11 family can be divided into three classes 802.11a, 802.11b, 802.11 i/e/…/w.

IEEE 802.11a one of the standards for wireless local networks, which describes the principles of operation of devices in the ISM frequency range (frequency band 5,155,825 GHz) according to the OFDM (Orthogonal Frequency Division Multiplexing) principle. The band is divided into three operating zones with a width of 100 MHz, and for each zone the maximum radiated power is defined as 50 mW, 250 mW, 1 W. It is assumed that the last frequency zone will be used to organize communication channels between buildings or external objects, and the other two zones within them. The edition of the standard, approved in 1999, defines three mandatory speeds of 6, 12 and 24 Mb/s and five optional speeds of 9, 18, 36, 48 and 54 Mb/s. However, this standard has not been adopted in Russia due to the use of part of this range by departmental structures. Possible solution This problem can be addressed by the 802.11h specification, which is complemented by algorithms for efficient selection of frequencies for wireless networks, as well as tools for managing spectrum use, monitoring radiated power, and generating relevant reports. The range of devices in enclosed spaces is about 12 meters at a speed of 54 Mb/s, and up to 90 meters at a speed of 6 Mb/s, in open spaces or in a line of sight zone of about 30 meters (54 Mb/s), and up to 300 meters at 6 Mb/s. However, some manufacturers are introducing acceleration technologies into their devices, which make it possible to exchange data in Turbo 802.11a at speeds of up to 108 Mb/s.

IEEE 802.11b the first standard that became widespread (it was the one that originally bore the Wi-Fi trademark) and made it possible to create wireless local networks in offices, houses, and apartments. This specification describes the principles for interoperability of devices in the 2.4 GHz (2.42.4835 GHz) band, divided into three non-overlapping channels using DSSS (Direct-Sequence Spread-Spectrum) technology and, optionally, PBCC ( Packet Binary Convolutional Coding, binary convolutional coding). According to this modulation technology, a redundant set of bits is generated for each transmitted bit useful information, due to this, there is a higher probability of recovering the transmitted information and better noise immunity (noise and interference are identified as a signal with an unequal set of bits and therefore are filtered out). The standard defines four mandatory speeds: 1, 2, 5.5 and 11 Mb/s. As for the possible radius of interaction between devices, it is about 30 meters in enclosed spaces at a speed of 11 Mb/s, and up to 90 meters at a speed of 1 Mb/s, in open spaces or in the line of sight about 120 meters (11 Mb/s). s), and up to 460 meters at 1 Mb/s. In the face of ever-increasing data flows, this specification has practically exhausted itself, and it has been replaced by the IEEE 802.11g standard.

IEEE 802.11g a wireless network standard that is a logical development of 802.11b, in the sense that it uses the same frequency range and is backward compatible with devices that comply with the 802.11b standard (in other words, 802.11g equipment must be compatible with the older 802.11b specification). At the same time, this representative of the family of specifications, as expected, tried to take all the best from the pioneers 802.11b and 802.11a. So, the basic principle of modulation is borrowed from 802.11a OFDM together with CCK (Complementary Code Keying) technology, and additionally the use of PBCC technology is provided. Thanks to this, the standard provides six mandatory speeds of 1, 2, 5.5, 6, 11, 12, 24 Mb/s, and four optional speeds of 33, 36, 48 and 54 Mb/s. The coverage radius is increased in enclosed spaces to 30 meters (54 Mb/s), and up to 91 meters at a speed of 1 Mb/s; within line of sight, communication is available at a distance of 120 meters at a speed of 54 Mb/s, and when removed at 460 meters it is possible to work at a speed of 1 Mb/s.
The set of specifications 802.11 i/e/…/w, which we have identified as a separate class, is mainly intended to describe the functioning of various service components and the development of new technologies and standards for wireless communications. For example, the operation of wireless bridges, requirements for physical parameters channels (radiation power, frequency ranges), specifications aimed at different categories of users, etc. In terms of add-ons and new standards for organizing wireless networks from this group, we have already considered 802.11.h. As another example, let's look at 802.11n. According to the international consortium EWC (Enhanced Wireless Consortium), the use of 802.11n is a high-speed standard, which is backward compatible with 802.11a/b/g, and data transfer rates will reach 600 Mb/s. This will allow you to use it in tasks where using Wi-Fi limited by insufficient speed.

IEEE 802.11n- version of the 802.11 standard for Wi-Fi networks.
This standard was approved on September 11, 2009. The 802.11n standard increases data transfer speeds by up to four times compared to 802.11g devices (which have a maximum speed of 54 Mbps), when used in 802.11n mode with other 802.11n devices. Theoretically, 802.11n is capable of providing data transfer rates of up to 600 Mbit/s (IEEE 802.11ac standard up to 1.3 Gbit/s), using data transmission over four antennas at once. One antenna - up to 150 Mbit/s.
802.11n devices operate in the 2.4-2.5 or 5.0 GHz bands.
In addition, 802.11n devices can operate in three modes:

• Legacy, which provides support for 802.11b/g and 802.11a devices;
• Mixed, which supports 802.11b/g, 802.11a and 802.11n devices;
• “pure” mode - 802.11n (it is in this mode that you can take advantage of the increased speed and increased data transmission range provided by the 802.11n standard).

The draft version of the 802.11n standard (DRAFT 2.0) is supported by many modern network devices. The final version of the standard (DRAFT 11.0), which was adopted on September 11, 2009, provides speeds of up to 600 Mbps, multiple input/output, known as MIMO, and greater coverage. As of 2011, there are a small number of devices that comply with the final standard. For example, the company D-LINK, its main products underwent standardization in 2008. There are respectable companies involved in re-standardizing basic products.
IT-Wave LLC offers equipment that meets the latest market requirements, such as, as well as a series of products. The presented equipment is built on the basis of this standard, but has wider functionality, thanks to proprietary developments by Proxim and Infinet.

WMAN (Wireless Metropolitan Area Networks)- city-scale wireless networks. Provide broadband access to the network via a radio channel.
The IEEE 802.16 standard, published in April 2002, describes the wireless MAN Air Interface. 802.16 is a so-called “last mile” technology that uses the frequency range from 10 to 66 GHz. Since this is the centimeter and millimeter range, a “line of sight” condition is necessary. The standard supports point-to-multipoint topology, frequency-division duplex (FDD) and time-division duplex (TDD) technologies, with quality of service (QoS) support. Audio and video transmission is possible. The standard defines a throughput of 120 Mbit/s per channel at 25 MHz.
The 802.16a standard follows the 802.16 standard. It was published in April 2003 and uses the frequency range from 2 to 11 GHz. The standard supports mesh networking. The standard does not impose a “line of sight” condition.

802.16e(mobile WiMAX) is a wireless Internet technology developed by South Korean telecommunications companies (WiBro (short for Wireless Broadband)).
The technology uses time multiplexing, orthogonal frequency division, and a channel width of 8.75 MHz. It was supposed to achieve higher data transfer rates than mobile phones can use (as in CDMA standard 1x) and provide mobility for broadband connections.
In February 2002, the Korean government allocated 100 MHz band in the 2.3-2.4 GHz range, and in 2004 the specifications were codified in the Korean WiBro Phase 1 standard, which were then included in the international standard IEEE 802.16e (Mobile WiMAX ). Base stations of this standard provide a total throughput of up to 30-50 Mbit/s for each operator and can cover a radius from 1 to 5 km. Connectivity remains for moving objects at speeds up to 120 km/h, which is significantly better than local wireless networks - their limit is approximately the same as walking speed, but worse than networks cellular communications- up to 250 km/h. Real testing of the network in Busan during the APEC summit showed that real speeds and restrictions are much lower than in theory.
The standard supports QoS - priorities in data transfer different types, which allows you to reliably transmit video streams and other data that is sensitive to channel delays. This is the advantage of the standard over fixed WiMAX (802.16d). Also, its requirements are much more detailed in detail than in the WiMAX standard.
The first versions of the Yota (Skartel) network were built using equipment of this standard.

Wireless Standards Comparison Chart

The IEEE (Institute of Electrical and Electronic Engineers) is developing WiFi 802.11 standards.

IEEE 802.11 is the base standard for Wi-Fi networks, which defines a set of protocols for the lowest transfer rates.

IEEE 802.11b- describes b O higher transmission speeds and introduces more technological restrictions. This standard was widely promoted by WECA ( Wireless Ethernet Compatibility Alliance ) and was originally called WiFi .
Frequency channels in the 2.4GHz spectrum are used ().
Ratified in 1999.
RF technology used: DSSS.
Coding: Barker 11 and CCK.
Modulations: DBPSK and DQPSK,
Maximum data transfer rates (transfer) in the channel: 1, 2, 5.5, 11 Mbps,

IEEE 802.11a- describes significantly higher transfer rates than 802.11b.
Frequency channels in the 5GHz frequency spectrum are used. ProtocolNot compatible with 802.11 b.
Ratified in 1999.
RF technology used: OFDM.
Coding: Conversion Coding.
Modulations: BPSK, QPSK, 16-QAM, 64-QAM.
Maximum data transfer rates in the channel: 6, 9, 12, 18, 24, 36, 48, 54 Mbps.

IEEE 802.11g - describes data transfer rates equivalent to 802.11a.
Frequency channels in the 2.4GHz spectrum are used. The protocol is compatible with 802.11b.
Ratified in 2003.
RF technologies used: DSSS and OFDM.
Coding: Barker 11 and CCK.
Modulations: DBPSK and DQPSK,
Maximum data transfer rates (transfer) in the channel:
- 1, 2, 5.5, 11 Mbps on DSSS and
- 6, 9, 12, 18, 24, 36, 48, 54 Mbps on OFDM.

IEEE 802.11n- the most advanced commercial WiFi standard, currently officially approved for import and use in the Russian Federation (802.11ac is still being developed by the regulator). 802.11n uses frequency channels in the 2.4GHz and 5GHz WiFi frequency spectrums. Compatible with 11b/11 a/11g . Although it is recommended to build networks targeting only 802.11n, because... requires configuration of special protective modes if backward compatibility with legacy standards is required. This leads to a large increase in signal information anda significant reduction in the available useful performance of the air interface. Actually, even one WiFi client 802.11g or 802.11b will require special settings the entire network and its immediate significant degradation in terms of aggregated performance.
The WiFi 802.11n standard itself was released on September 11, 2009.
WiFi frequency channels with a width of 20MHz and 40MHz (2x20MHz) are supported.
RF technology used: OFDM.
OFDM MIMO (Multiple Input Multiple Output) technology is used up to the 4x4 level (4xTransmitter and 4xReceiver). In this case, a minimum of 2xTransmitter per Access Point and 1xTransmitter per user device.
Examples of possible MCS (Modulation & Coding Scheme) for 802.11n, as well as the maximum theoretical transfer rates in the radio channel are presented in the following table:

Here SGI is the guard intervals between frames.
Spatial Streams is the number of spatial streams.
Type is the modulation type.
Data Rate is the maximum theoretical data transfer rate in the radio channel in Mbit/sec.

It is important to emphasize that the indicated speeds correspond to the concept of channel rate and are the limiting value using this set technologies within the framework of the described standard (in fact, these values, as you probably noticed, are written by manufacturers on the boxes of home WiFi devices in stores). But in real life, these values ​​are not achievable due to the specifics of the WiFi 802.11 standard technology itself. For example, “political correctness” is strongly influenced here in terms of ensuring CSMA/CA ( WiFi devices constantly listen to the air and cannot transmit if the transmission medium is busy), the need to acknowledge each unicast frame, the half-duplex nature of all WiFi standards and only 802.11ac/Wave-2 can begin to bypass this, etc. Therefore, the practical effectiveness of outdated 802.11 standards b/g/a never exceeds 50% under ideal conditions (for example, for 802.11g the maximum speed per subscriber is usually no higher than 22Mb/s), and for 802.11n the efficiency can be up to 60%. If the network operates in protected mode, which often happens due to the mixed presence of different WiFi chips on different devices on the network, then even the indicated relative efficiency can drop by 2-3 times. This applies, for example, to a mix of Wi-Fi devices with 802.11b, 802.11g chips on a network with WiFi 802.11g access points, or a WiFi 802.11g/802.11b device on a network with WiFi 802.11n access points, etc. Read more about .

In addition to the basic WiFi standards 802.11a, b, g, n, additional standards exist and are used to implement various service functions:

. 802.11d. To adapt various WiFi standard devices to specific country conditions. Within the regulatory framework of each state, ranges often vary and may even differ depending on geographic location. The IEEE 802.11d WiFi standard allows you to adjust frequency bands in devices from different manufacturers using special options introduced into the media access control protocols.

. 802.11e. Describes QoS quality classes for the transmission of various media files and, in general, various media content. Adaptation of the MAC layer for 802.11e determines the quality, for example, of simultaneous transmission of audio and video.

. 802.11f. Aimed at unifying the parameters of Access Points Wi-Fi standard various manufacturers. The standard allows the user to work with different networks when moving between coverage areas of individual networks.

. 802.11h. Used to prevent problems with weather and military radars by dynamically reducing radiated power Wi-Fi equipment or dynamically switching to another frequency channel when a trigger signal is detected (in most European countries, ground stations tracking weather and communications satellites, as well as military radars, operate in bands close to 5 MHz). This standard is necessary requirement ETSI requirements for equipment approved for operation in the countries of the European Union.

. 802.11i. The first iterations of the 802.11 WiFi standards used the WEP algorithm to secure Wi-Fi networks. It was believed that this method could provide confidentiality and protection of the transmitted data of authorized wireless users from eavesdropping. Now this protection can be hacked in just a few minutes. Therefore, the 802.11i standard developed new methods for protecting Wi-Fi networks, implemented at both the physical and software levels. Currently, to organize a security system in Wi-Fi 802.11 networks, it is recommended to use Wi-Fi Protected Access (WPA) algorithms. They also provide compatibility between wireless devices various standards and various modifications. WPA protocols use an advanced RC4 encryption scheme and a mandatory authentication method using EAP. The stability and security of modern Wi-Fi networks is determined by privacy verification and data encryption protocols (RSNA, TKIP, CCMP, AES). The most recommended approach is to use WPA2 with AES encryption (and don't forget about 802.1x using tunneling mechanisms, such as EAP-TLS, TTLS, etc.). .

. 802.11k. This standard is actually aimed at implementing load balancing in the radio subsystem of a Wi-Fi network. Usually wireless local network The subscriber device usually connects to the access point that provides the strongest signal. This often leads to network congestion at one point, when many users connect to one Access Point at once. To control such situations, the 802.11k standard proposes a mechanism that limits the number of subscribers connected to one Access Point and makes it possible to create conditions under which new users will join another AP even despite more weak signal from her. In this case, the aggregated network throughput increases due to more efficient use of resources.

. 802.11m. Amendments and corrections for the entire group of 802.11 standards are combined and summarized in a separate document under the general name 802.11m. The first release of 802.11m was in 2007, then in 2011, etc.

. 802.11p. Determines the interaction of Wi-Fi equipment moving at speeds up to 200 km/h past fixed points WiFi access, located at a distance of up to 1 km. Part of the Wireless Access in Vehicular Environment (WAVE) standard. WAVE standards define an architecture and a complementary set of utility functions and interfaces that provide a secure radio communications mechanism between moving vehicles. These standards are developed for applications such as traffic management, traffic safety monitoring, automated payment collection, vehicle navigation and routing, etc.

. 802.11s. A standard for implementing mesh networks (), where any device can serve as both a router and an access point. If the nearest access point is overloaded, data is redirected to the nearest unloaded node. In this case, a data packet is transferred (packet transfer) from one node to another until it reaches its final destination. This standard introduces new protocols at the MAC and PHY levels that support broadcast and multicast transmission (transfer), as well as unicast delivery over a self-configuring point system Wi-Fi access. For this purpose, the standard introduced a four-address frame format. Implementation examples WiFi networks Mesh: , .

. 802.11t. The standard was created to institutionalize the process of testing solutions of the IEEE 802.11 standard. Testing methods, methods of measurement and processing of results (treatment), requirements for testing equipment are described.

. 802.11u. Defines procedures for interaction of Wi-Fi standard networks with external networks. The standard must define access protocols, priority protocols and prohibition protocols for working with external networks. At the moment, a large movement has formed around this standard, both in terms of developing solutions - Hotspot 2.0, and in terms of organizing inter-network roaming - a group of interested operators has been created and is growing, who jointly resolve roaming issues for their Wi-Fi networks in dialogue (WBA Alliance ). Read more about Hotspot 2.0 in our articles: , .

. 802.11v. The standard should include amendments aimed at improving the network management systems of the IEEE 802.11 standard. Modernization at the MAC and PHY levels should allow the configuration of client devices connected to the network to be centralized and streamlined.

. 802.11y. Additional communication standard for the frequency range 3.65-3.70 GHz. Designed for latest generation devices operating with external antennas at speeds up to 54 Mbit/s at a distance of up to 5 km in open space. The standard is not fully completed.

802.11w. Defines methods and procedures for improving the protection and security of the media access control (MAC) layer. The standard protocols structure a system for monitoring data integrity, the authenticity of their source, the prohibition of unauthorized reproduction and copying, data confidentiality and other protection measures. The standard introduces management frame protection (MFP: Management Frame Protection), and additional security measures help neutralize external attacks, such as DoS. A little more on MFP here: . In addition, these measures will ensure security for the most sensitive network information that will be transmitted over networks that support IEEE 802.11r, k, y.

802.11ac. A new WiFi standard that operates only in the 5GHz frequency band and provides significantly faster O higher speeds both for an individual WiFi client and for a WiFi Access Point. See our article for more details.

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