To understand what the article is talking about, it is necessary to understand the meaning of the word "interface". This word means the possibilities, methods and methods of interaction between two systems. The interface of the router is his connection, communication with something.

In our case, the interface is two:

1. One system is a person (user), the second system is a router itself. That is the user you need to go to the router settings and make some changes there to make it work under your requirements. This is the settings interface.
2. One system is a computer network, the second system is again the router itself. That is, he must communicate with the computer network (in fact, for which it has been created), for this, the router must have a connection with the network or by wires (LAN, WAN ports, etc.), or by Wi-Fi. This is a connection interface.

Consider both interfaces in more detail, and start with the settings.

Routher settings interface

As we already understood to set up a router, we must join him in a dialogue. That is, we give him a team, he hears us, understands, and performs. The interface, that is, the intermediary between the user and the router will perform the most common web browser (IE, Firefox, Opera, etc.). It happens as follows.

We connect the router to a computer with a network wire patch cord, or via Wi-Fi, and run a web browser. Any router has a network IP address - we enter it in address line browser. For example - 192.168.1.1.

Log in to the router settings

The address of your router is not difficult to find out - either turn it over and read it on the label under the bottom or in the router setting instructions.

The IP address of the router on the label under the bottom

We press "ENTER", and the router will immediately ask - and who I have the honor to communicate with? That is, authorization is necessary. The username and password are also indicated by the bottom of the router and in the manual. We enter them into the appropriate fields and enter the settings menu.

Routher settings

After entering the settings, it starts directly communication with the router, its configuration. For convenience for a person (but not for a computer or router), the settings are made in a convenient menu, with points and sub-clauses.

Routher settings window

All this "clearer" and the "logical" menu is needed only to a person, and it really works - set up a router very easily and quickly even to the user with small experience. This speaks about a friendly interface.

For example, we need to configure Wi-Fi.

Setting up Wi-Fi router

Of course, we go to the "Wireless" menu item, which means a wireless network.

Setting Wi-Fi Routerbut

In the window that opens, we produce the Wi-Fi network setting, nothing else. Communication user and router, mutual understanding, interface.

Network interface

Consider the second case of the interface, already physical (previously dialogue). At least at first glance and there is nothing in common between them, but there is a common interface. Only in this case already network - there is a physical connection of the router to a computer network with special connectors (ports), or a wireless connection that this case it does not matter.

Routher network interfaces on the rear panel

Input ports and physically connecting computer network wires. There are at least two kinds - "looking" into the outside world, that is, connecting to another network or provider (WAN port), and "looking" into their own internal network (LAN ports). The Linux operating system even assigned the names of these ports - WAN port has the designation "ETH0", and LAN port is "ETH1".

Wired interface

Wired connection will require a network wire. There are several varieties - twisted steam, coaxial cable and fiber optic.

Types of network cables

Each type has its own connector for connecting, that is, a coaxial cable cannot be connected to the port for twisted pair.

The most commonly used is the type of twisted pair - the golden middle between the price and the data rate. The cable connection is made to the corresponding port of the router (network interface of the router), and another end to the computer's network card (PC network interface).

Connect to computer

For different types of conductor this procedure Connections are no different, they are the same type.

Setting up WAN and LAN interfaces

By connecting the wires, we turn to the configuration of the router. With the entry procedure in the settings via the web interface, we got acquainted at the beginning of the article. Going into the settings, go to the Network tab.

Setting the wired network

Choosing a menu item will open the submenu containing separately LAN settings and Wan Port.. Go to the corresponding subparagraphs and customize the way it usually. Specifically, the settings in this article are not considered.

After entering the changes, we must press "Save" to be preserved and activated.

Wireless interface

The wires are currently going to the past, and is increasingly given to the development of wireless interfaces. These include bluetooth, infrared transmission and, of course, Wi-Fi. It is for Wi-Fi that future.

Through Wi Fi, computers and routers are combined through air through radio waves with a frequency of 2.4 GHz and 5 GHz (in the development and 6 GHz). For communication, a radio module and antenna are needed.

Wi-Fi router

Turning on the router, it creates a wireless network that you want to detect a computer and connect to it. The wireless network has a name, and by the rules of good tone - a password for connecting to it.

All network found are displayed on the desktop of the computer in the lower right corner.

List of discovered Wi-Fi networks

By clicking on the mouse twice the name of the network, we will connect to it. But first you need to configure in the router settings. How to go to the Wi-Fi settings, it was described in the first part of the article.

For the late video lesson, how to set a password to the TP-LINK router interface:

• Tutorial

Introduction

In this article, the technology of wireless local networks according to IEEE 802.11 is studied in laboratory work. The IEEE standard was developed by the Institute of Electrical Engineering Engineers (Institute of Electrical and Electronic Engineers). Hence he got his name. This standard defines the local Ethernet networks; Therefore, the TCP / IP model does not define the Ethernet network in their comments requests, and refers to IEEE Ethernet documents. All work will be performed in the Cisco Packet Tracer program.

Concept wireless networks

Many users regularly use services and wireless LAN devices (Wireless LAN - WLAN). Currently, the trend of using portable devices, such as laptops, tablets, smartphones, is growing. The concepts of "smart home" are actively developing, most of the devices of which are connected by "air". In this regard, there was a need for wireless connection in all crowded places: at work, at home, hotel, in a cafe or bookstore. With the increase in the number of wireless devices that are connected through the WLAN network, the popularity of wireless networks has grown.
Below is a simplified scheme of the network in the "House of Book" on the Nevsky Prospect in St. Petersburg.

Portable visitors computers interact with WLAN device, called a wireless access point (Access Point). Access point uses radio channel to send and receive frames (individual, complete HTML documents, which, together with other HTML documents, can be displayed in the browser window) from the client device, such as a computer. In addition, the access point is connected to the same Ethernet network as devices that ensure the work of the store, therefore buyers, and employees can search for information on remote websites.

Comparison of Wireless Local Networks with LAN

Wireless Local Networks are largely similar to local networks, for example, both types of networks allow devices to interact with each other. For both types of networks, IEEE is running (IEEE 802.3 for Ethernet and 802.11 networks for wireless networks). Both standards described the format of the network frames (header and conflict), it is indicated that the header must have a length of 6 bytes and contain the MAC address of the sender and the recipient. Both standards indicate exactly how devices on the network should determine when you can transmit a frame to Wednesday, and when it is impossible.
The main difference between the two types of networks is that energy emission technology (or radio wave technology) is used to transmit data in wireless networks), and the Ethernet network uses the transmission of electrical pulses along the copper cable (or light pulses in the optical fiber). For radio wavelength transmission, a special work is not needed, usually say that "communication happens through the air" to emphasize that there is no physical network. In fact, any physical objects on the radio signal path (walls, metal structures, etc.) are an obstacle to worsening the quality of the radio signal.

Wireless Local Network Standards

IEEE defines four basic standards of WLAN 802.11: 802.11a, 802.11b, 802.11g and 802.11n.
The following four organizations had the greatest impact on the standards of wireless networks (see table below)

Comparison of WLAN standards

Terms

DSSS (Direct Sequence Spread Spectrum - direct sequence method for spectrum expansion)
- OFDM (Orthogonal Frequency-Division Multiplexing - Multiplexing with orthogonal frequency division of channels)

In addition to the basic standards from the table, there are additional standards that are listed below.

Additional standards

802.11 - initial 1 Mbps and 2 Mbps, 2.4 GHz and IR Standard (1997).
802.11c. - procedures for operations with bridges; Included in IEEE 802.1D (2001) standard.
802.11d. - International roaming extensions (2001).
802.11E. - Improvements: QoS, Batch Mode (Packet Bursting) (2005).
802.11h - distributed over the spectrum 802.11a (5 GHz) for compatibility in Europe (2004).
802.11i - Improved security (2004).
802.11j. - Extensions for Japan (2004).
802.11K. - Improved radio resource measurement.
802.11l - Reserved.
802.11m - Amendments and corrections for the entire group of standards 802.11.
802.11O. - Reserved.
802.11p - Wave - Wireless Access for the Vehicular Environment (Wireless access for the vehicle environment).
802.11q - reserved, sometimes confused it from 802.1q.
802.11R - Quick roaming.
802.11S. - Ess Wireless Mesh Network (Extended Service Set - Advanced Services Set; Mesh Network - Multisy Network).
802.11U. - Interaction with non-802 networks (for example, cellular).
802.11v - Wireless network management.
802.11w - Protected Management Frames (protected control frames).
802.11x - Reserved and will not be used. No need to be confused with an IEEE 802.1x access control standard.
802.11Y. - Additional communication standard, operating at the frequencies of 3.65-3.70 GHz. Provides speed up to 54 Mbps at a distance of up to 5000 m in the open space.
802.11AC. - New standard IEEE. Data transfer rate is up to 6.77 Gbps for devices having 8 antennas. Approved in January 2014.
802.11ad. - A new standard with an additional range of 60 GHz (frequency does not require licensing). Data transfer rate - up to 7 Gb / s

There are also two recommendations. The letters at them are capital.

802.11F. - Inter-Access Point Protocol (Data Exchange Protocol for Transferring Data Battle Access Points. This protocol is a recommendation that describes the optional extension of IEEE 802.11, providing a wireless access point for communication between systems of different manufacturers).
802.11t - Wireless Performance Prediction (WPP, Wireless Equipment Performance Prediction) - Test Methods (Method is a set of methods recommended by IEEE for testing networks 802.11: Methods for measuring and processing results, requirements for test equipment).

Basic devices and conditional signs in working with Wi-Fi

1. Access point is a wireless "extension" wired network

2. The router is a more "smart" device that does not just receive and transmits data, but also redistributes them according to various established rules and executes the specified commands.

3. Cloud - customized part of the network

4. Wi-Fi connection

Main ways to use Wi-Fi

1. Wi-Fi Bridge - connection of two Wi-Fi access points

2. Wi-Fi Router - Connect all devices to the Wi-Fi router (the entire network is connected by wireless).

3. Wi-Fi dot Access - Connecting part of the network for wireless work

Tasks of laboratory work.

1. Create and configure the second and third option to use Wi-Fi in Cisco Packet Tracer.
2. Configure the bridge between the two access points (the first option of using Wi-Fi) on real equipment.

Performing laboratory work.

Task number 1 (Network No. 2 option)

1. Create on the work field Packet Tracer Wi-Fi router (he is a Wi-Fi router)

2. Create a router from the provider (for example, the name of the provider is "miry-mir"). I chose the Cisco 1841 router.

3. Connect their cross-cable (dotted line), since the same type devices (routers). Connect this: one end in Router1 in FasteThernet 0/0, and the other end in Wireless Router0 in the Internet connector, since Router1 distributes us the Internet.

4. Certify the Internet router (Router1) to work with the network. To do this, let's go to the router settings twice by clicking on it and then let's go to the CLI tab (Command Line Interface).

In the "Would You Like to Enter The Initial Configuration Dialog dialog? : "(You want to log in to the initial configuration dialog box) write" No ".

We write the following sequence of commands:

Router\u003e EN.
Router # Conf T
Router (Config) #Int F0 / 0
Router (Config IF) #IP Address 120.120.0.1 255.255.255.0
Router (Config-If) #No Shut
Router (Config-If) #end
Router # WR Mem

By tradition, consider them in order.

1) EN - Enable. Advanced configuration access
2) CONF T - CONFIGURATION TERMINAL. Opens the terminal settings
3) INT FA0 / 0 - Interface Fastetersnet0 / 0. Go to the setting of the specified port (in our case to Fastethernet0 / 0)
4) IP Address 120.120.0.1 255.255.255.0 - the IP address and its mask are set. Address - 120.120.0.1 (Suppose this address gave us a provider), mask - / 24.
5) No shut - no shutdown. Enable, configured by us, interface
6) END - complete settings.
7) WR MEM - Write Memory. Saving configurations.

The connection is established.

5. Customize wireless router (Wireless Router0) to work with the network. For this, as in the case of the previous router, we turn to the settings of the router twice by clicking on it. In tabs, select the graphical user interface (GUI - Graphical User Interface). This mode will be displayed when entering the router's address in any browser.

Stop the following settings:

Internet Connection Type - Static IP
Internet IP Address - 120.120.0.2
Subnet Mask - 255.255.255.0
Default Gateway - 120.120.0.1
Router IP - 192.168.0.1
Subnet Mask (Router IP) - 255.255.255.0
Start IP Address - 192.168.0.100
Maximum Numbers of Users - 50

"SAVE SETTINGS"

Placing settings:
We have chosen static IP, since the provider issued us a white IP address (120.120.0.1/24). Default Gateway is the address of the router from the provider. Router address from wireless devices - 192.168.0.1/24. The router will hand out IP from 100 to 150.

6. Go to the Wireless tab, that is, a wireless connection.

Test the following settings:

Network Mode - Mixed
Network Name (SSID) - HaBr
Radio Band - Auto
Wide Channel - Auto
Standard Channel - 1 - 2.412Ghz
SSID Broadcast - Disabled

And at the bottom of the page click the button "SAVE SETTINGS"

Placing settings:

Mode of operation of the router We have chosen mixed, that is, any device that supports the types of the router can connect to it (in the Cisco Packer Tracer emulator is G, B and N). We set the name of the network HABR. The width of the channel router will choose himself (it is possible to choose either 20 or 40 megahertz). The frequency in the emulator is available only to 2,4GHz it and leave it. We hid the name of the network, that is, the devices will not see our Wi-Fi network until its name is introduced.

7. Configure the protection of our router. To do this, let's get into the Security tab and in the Security Mode item will select WPA2 Personal, as WPA is a vulnerable protection. Choose WPA2 Enterprise, too, is not worth it, since for her work we will need a radius server that we did not do. Encryption algorithm Leave AES and enter the code word. I put Habrahabr.

8. Add 3 devices as on the diagram (smartphone, laptop and computer). Then we will replace the connectors for RJ-45 on the Wi-Fi antenna (in the smartphone by default antenna).

9. In the Config tab, set the settings that were exhibited on the router. This operation must be done on all devices.

10. Go to the desktop of any computer and open the command line.

11. Check which addresses router issued devices. To do this, enter the ipconfig command.

As can be seen in the screenshot, the router gives the addresses from 192.168.0.100 to 192.168.0.150.

12. Check the operability of the network from any device with the Ping command. Pencing will be 2 addresses - the address of the router (192.168.0.1) and the white address (120.120.0.1), that is, we will check whether the device will be able to enter the Internet.

Again, everything works.

As a result, we got a Wi-Fi network, which is depicted in the second use

Task number 1 (Network No. 3)

2. Create an access point on the program's work field and connect it with a switchee. If you wish, the access point can be configured (Port 0 is a physical port, and Port 1 - Wireless)

3. Create another VLAN for the wireless access point.

4. Add 0 VLAN 4 in the router settings, as well as add it to the Access sheet to access the Internet.

Since we were done in previous laboratory work (via VLAN and PAT), I will not stop in detail, but I regish all commands on devices

Switch\u003e en
Switch # Conf T
Switch (Config) #vlan 4
Switch (Config-VLAN) #Name Wi-Fi
Switch (Config-VLAN) #Exit
Switch (Config) #Interface Fastethernet0 / 5
Switch (Config-If) #Switchport Access VLAN 4

Router (Sabrberface)

Router\u003e EN.
Router # Conf T
Router (Config) #Int FA0 / 1.4
Router (Config-Subif) #encapsulation DOT1Q 4
Router (Config-Subif) #IP Address 192.168.4.1 255.255.255.0
Router (Config-Subif) #No Shutdown
Router (Config-Subif) #end

Router (DHCP (Dynamic Host Configuration Protocol - Dynamic Node Setup Protocol). Network protocol that allows computers to automatically receive an IP address and other parameters required to work on the TCP / IP network)

Router # Conf T
Router (Config) #IP DHCP POOL Wi-Fi-Pool
Router (DHCP-CONFIG) #Network 192.168.4.0 255.255.255.0
Router (DHCP-CONFIG) # Default-Router 192.168.4.1
Router (DHCP-CONFIG) #Exit
Router (Config) #IP DHCP EXCLUDED-ADDRESS 192.168.4.1
Router (Config) #end

Here I will stop in more detail, since earlier we have not met with this parameter.

Router (Config) #IP DHCP POOL Wi-Fi-Pool - Creating a Pool (DBC) Addresses DHCP
Router (DHCP-Config) #Network 192.168.4.0 255.255.255.0 - a network in which DHCP is implemented and its mask
Router (DHCP-config) # Default-Router 192.168.4.1 - Default address (it is the address of the router)
Router (Config) #IP DHCP EXCLUDED-ADDRESS 192.168.4.1 - Exclusion of the address of the router from DHCP Distribution

Router (Access Sheet)

Router (Config) #IP Access-List Standard Habrahabr
Router (Config-STD-NaCl) #permit 192.168.4.0 0.0.0.255
Router (Config-Std-NaCl) #Exit
Router (Config) #Int FA0 / 1.4
Router (Config-Subif) #IP Nat Inside
Router (Config-Subif) #end

Add your smartphone to the workspace Packet Tracer and plugging the PC, server and the Internet, that is, 192.168.2.2, 192.168.3.2, 120.120.53.1.

As you can see, everything works.

Task number 2 (Network No. 1)

Unfortunately, in Packet Tracer, there is no possibility to create a Wi-Fi Bridge (it is also a repeater or repeater), but we will make it a simple action on real equipment in a graphics environment.

The equipment on which the settings will be held - the ASUS RT-N10 router and the so-called TP-LINK TL-WA850RE repeater.

Let us turn to the adjustment of the ASUS router. To do this, open the browser and enter the address of the router (by default it will open)

Go to the "Wireless Network" tab and setting the setting as in the scarlet below.

Go to the "LAN" tab (local computing network) and set the following settings.

Go to the main tab. There we can see our MAC address

Go to the TP-LINK repeater setting

We automatically automatically give the main menu and mode fast settings. Press the "output" and perform the setting yourself.

Go to the "Network" tab and exhibit the following settings.

Go to the "Wireless Mode" tab and configure the input and output stream.

In the "Profile" tab, we see all the profiles we have created. Press the "Edit" button

Configure the safety of the WPA2 key with the addition of the WPA2 key.

Go to the main menu and select "Connect" in "Wireless Connection". Next will follow the setting of the bridge. You may need to enter the password from the ASUS router.

And voila! Everything is ready!

In order not to be confused to which device to connect, you can hide SSID on ASUS router

Check Cable Connection

Ping is successful.

Wi-Fi check.

Successfully.

And view the final configuration, when connecting to the repeater.

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Prospective wireless interfaces of local networks

• Introduction
• 1.1 General concepts
• 1.4 Access points
• 2.1 Standard 802.11
• 2.4 Wi-Fi
• 2.5 Hiperlan / 2
• Conclusion
• Bibliographic list

Introduction

For several decades, people have already apply computer networks to provide communication between personnel, computers and servers in offices, large companies, educational institutions. Recently, there has been a tendency to increasingly using wireless networks.

Wireless networks are adjacent to us for many years. So, to primitive forms wireless communication You can attribute the flue signals of the American Indians, when they threw the skin of the bison skins to transfer some message to a large distance. Or the use of intermittent lighting lights for transmission by means of the alphabet of Morse information between ships, this method has been and remains an important mold in the navigation. And, of course, so popular now cell PhonesAllowing people to communicate through huge distances can also be attributed to wireless communication.

Today, the use of wireless networks allows people to "expand" their workplace and get as a result of this a number of advantages. During business trips, you can, for example, send emails waiting for a plane planting at the airport. Homeowners can easily use a common Internet connection for many PCs and laptops without laying cables.

Thus, the topic of this work is undoubtedly relevant.

Research Subject - Local Network Construction Technologies, Research Object - Wireless Local Network Interfaces.

The purpose of the work is to study the promising wireless interfaces of local networks. To achieve the goal, it is necessary to solve the following tasks:

Explore the basic aspects of building wireless local networks

Explore the technologies used to build wireless local networks.

The work of domestic and foreign authors, reference literature, periodic printing materials, information of specialized Internet resources are used as a methodological support.

1. Basic aspects of building wireless local networks

1.1 General concepts

A local computing network is called, as a rule, a network that has a closed infrastructure before going to the service provider. It may be small office network, consisting of several computers located in several cabinets, and a network of a large plant, which covers an area of \u200b\u200bseveral hectares. There are local networks (orbital centers, space stations), whose assemblies will be removed from each other at a distance of more than 10,000 km.

Local networks are closed-type networks, which is allowed to access a limited circle of users.

On the local network, computers are connected to each other by various access environments, such as copper or optical conductors, radio channels.

Wired communication on the local network is provided by Ethernet technology, wireless - Bluetooth, Wi-Fi, GPRS, etc. To ensure communication between the Local Network computers, various equipment models that support the relevant technologies are used. At the same time, the connection point between the user's computer and the local network is called a network interface or a local network interface.

In the general case, the interface is called a certain set of rules, methods and means that ensure the conditions of interaction between the elements of some system.

Currently, there is a tendency to more widespread use of wireless networks. And indeed, wireless interfaces are now available to use network services, work with e-mail and view the Web pages regardless of where the user is located.

There are many varieties of wireless communication, but the most important feature of wireless networks is that the connection is carried out between computer devices. These include personal digital assistants (Personal Digital Assistance, PDA), laptops, personal computers (PCs), servers and printers. Computer devices are considered to be those that have processors, memory and means of interaction with some network. Usually, cell phones are not related to the number of computer devices, but the latest phones and even headsets (headphones) have already have certain computing capabilities and network adapters. Everything goes to the fact that the majority will soon electronic devices will provide the ability to connect to wireless networks.

Wireless networks As a means of transmission to ensure interaction between users, servers and databases, radio waves or infrared (IR) range are used. This invisibility environment is invisible for humans. In addition, the actual transmission medium (air) is transparent to the user. Now many manufacturers integrate network interface cards (Network Interface Card, NIC), so-called network adapters, and antennas in computer devices Thus, that they are not visible to the user. It does wireless devices Mobile and convenient in use.

Wireless Local Networks provide high characteristics when transmitting data inside and outside offices, industrial premises and buildings. Users of such networks usually use laptops, PCs and PDAs with big screens and processors capable of performing resource-intensive applications. These networks are quite satisfying the requirements for compounds of computer devices of this type.

Wireless Local Networks easily provide the characteristics necessary for the uninterrupted performance of high-level applications. So, users of these networks can receive volumetric attachments in email messages or streaming video from the server.

According to its characteristics, components, costs and operations, these networks are similar to traditional wired local networks like Ethernet.

Due to the fact that the adapters of wireless local networks are already built into most laptops, many publicly available wireless network providers have begun to offer wireless local networks to provide mobile broadband access to the Internet.

Users of a number of publicly available wireless networks in the "hot" access areas, such as airports or hotels, can send and receive email messages or exit in the Internet for a specific fee (if this institution does not provide free access). The rapid increase in the number of publicly available wireless networks makes Internet available for users located in the cluster areas of people.

The prevailing for wireless local networks is the IEEE 802.11 standard, various versions of which are regulated by data transmission in the ranges of 2.4 and 5 GHz. The main problem associated with this standard is that the interaction of devices corresponding to its various versions does not ensure properly. Thus, adapters of computer devices of wireless local networks of the 802.11A standard standards do not provide connections to computer devices that comply with the 802.11b standard. There are other unsolved issues related to the 802.11 standard, for example, an insufficient degree of security.

In order to somehow solve problems associated with the application of the 802.11 device devices, the Wi-Fi Alliance organization reduced all its compatible functions into a single standard called Wireless Fidelity (Wi-Fi). If a device of wireless local networks meets the Wi-Fi standard, it practically guarantees its ability to collaboration With other devices that meet Wi-Fi standard. The openness of the Wi-Fi standard allows various users using different platforms to work in the same wireless LAN, which is extremely important for publicly available wireless local networks.

1.2 Wireless Structure Features

The structure (or architecture) of the network defines the protocols and components necessary to meet the requirements of the applications performed in it. One of the most popular standards, on the basis of which you can consider the network structure, is the reference model of interaction of open systems (Open System InterConnection (OSI) Reference Model) developed by the International Standards Organization, ISO). OSI model covers all network functions, Grouping them in the so-called levels whose tasks are performed by various network components (Figure 1.1). The OSI reference model is also conveniently used when considering various standards and the ability to interact wireless networks.

OSI levels ensure the following network functions.

Level 7 - application level. Provides communication with users and the work of basic communication services (file transfer, email). Examples of software performed at this level - Simple Mail Transfer Protocol, SMTP, Hypertext Transfer Protocol, HTTP and File Transfer Protocol (File Transfer Protocol, FTP).

Level 6 - the level of data representation. Regulates data syntax for application level and, if necessary, transform data formats. For example, this level may convert code representing data when connecting between remote systems of various manufacturers.

Figure 1.1 Levels of the reference model OSI

Level 5 - session level. Sets the communication sessions between applications, manages them and completes them. Intermediate software And access controllers provide such a communication form through a wireless network. If the wireless network is disrupted due to the interference, the session level task is to suspend communication until the level of interference level is reduced to the permissible.

Level 4 - transport level. Provides mechanisms to create, accompaniment and properly completed virtual chains, allowing higher levels not to take care of the network implementation items. In general, these chains are connections installed between applications performed at different parts of communication circuits (for example, between a laptop web browser and server web page). At this level, it works, for example, Transmission Control Protocol, TCP.

Level 3 - network level. Provides packet routing when they are followed from the sender to the recipient. The routing mechanism provided to send packets in the direction leading to the specified destination point. This level works the Internet Protocol, IP (Internet Protocol, IP).

Level 2 - channel level. Provides access to the environment, as well as synchronization between network objects and error control. In the wireless networks at this level, access is also coordinated to the shared medium and re-transmission in case of errors when transferring data from the sender to the recipient. In most variations, wireless networks use a common method of performing functions on a channel level, regardless of the actually used means of transmission.

Level 1 - physical level. Provides a real transmission of information through Wednesday. The physical level can include radio waves and IR radiation.

By combining levels, network structures ensure the execution of the necessary functions, but the wireless networks directly use the lower levels of the above-described model. For example, the network interface board performs channel and physical levels. Other components, such as intermediate wireless network software, provide functions characteristic of a session level. In some cases, adding a wireless network can only affect lower levels, but to ensure efficient application operation in case of deterioration of the wireless network characteristics, you should not forget about higher levels.

Each level of the OSI model provides the needs of a higher level.

Thus, TCP operating at the transport level establishes a connection to the applications performed on the remote host, without considering how the lower levels provide synchronization and signal transmission.

As follows from Figure 1.1, the protocols at each level interact through the network with the level of appropriate rank. However, the actual data transmission occurs at the physical level. As a result, this structure provides a stratification process, in which a particular level inserts information of its protocol into frames, located in the lower level frames. Frame, forwarded at the physical level, in reality contains frames of all top levels.

In the destination, each level transmits the corresponding frames to all higher levels, providing the operation of protocols at the levels of the same rank.

1.3 Wireless LAN Interfaces

In wireless networks, the same components are used as in wired networks, but wireless networks should be able to convert information into a form suitable for transferring it through an air environment (medium). Although the wireless network directly includes only a part of the entire network infrastructure, the decrease in the parameters of the entire network is called, undoubtedly deterioration caused by the application of the wireless transmission medium.

Wireless networks include computer devices, basic stations and wireless infrastructure.

Network interface board, or Network Adapter (Network Interface Card), provides an interface between a computer device and a wireless network infrastructure. It is installed inside a computer device, but external network adapters are used, which, after switching on, remain outside the computer device.

Standards for the wireless network are determined how the network interface board should function. For example, a board corresponding to the IEEE 802.11b standard can interact with only a wireless network, the infrastructure of which corresponds to the same standard. Therefore, users must be attentive and take care that the fee chosen by them corresponds to the type of infrastructure of the wireless network to which they want access.

The main component of the wireless LAN - the network interface radio settlement, is often implemented based on the 802.11 standard. These radio payments usually work at one physical level - 802.11A or 802.11b / g. As a result, the radio settlement must implement the version of the standard compatible with the wireless LAN. Radio payments of wireless local networks that implement several versions of this standard at once and providing a higher interaction ability (interoperability) are becoming increasingly common.

The wireless network interface board is also characterized by a form factor determining the physical and electrical parameters of the bus interface that allows the board to interact with the computer device.

Radio payments are supplied in various form factors: ISA, PCI, PC Card, Minipci and CF. PCs typically use ISA and PCI cards, and PCCard, Mini-PCI and CF adapters.

Industry-Standard Architecture (ISA)

Industry-Standard Architecture (ISA) is an architecture corresponding to the industrial standard. The ISA bus has gained widespread since the beginning of the 80s. Although its characteristics were very low, almost all PC manufacturers until recently installed at least one connector for the ISA tire. But its characteristics could not improve the same quick as the parameters of other computer components, and high-speed alternatives to this bus are already available. The ISA bus did not have a serious impact on the characteristics of the wireless local networks of the 802.LIB standard. It is not necessary to acquire new ISA cards, as they are already outdated.

PERIPHERAL COMPONENT INTERCONNECT (PCI).

Today Local Connection Tire peripheral devices - The most popular interface for PC, since it has high characteristics. Initially developed and released PCI in 1993. Intel, and this tire still satisfies the needs of the latest models of multimedia computers. PCI fees became the first to be implemented by the "Plug-and-Play" technology, a significantly facilitating network interface board to a computer. Circuit solutions PCI can recognize compatible PCI boards and start working with operating system Computer to configure each board. It saves time and avoids errors when installing in inexperienced users.

PC Card

The PC Card design fees were developed in the early 1990s by the International Memory Players Association for IBM PC personal computers (Personal Computer Memory Card International Association, PCMCIA). PC Card is a device size with a credit card containing external memory, modems, connection devices to external devices, as well as providing compatibility with a wireless network for small computer devices, such as laptops and PDAs. The most widespread and even more popular than boards for ISA or PCI tires, as used in laptops and PDA, the number of which is growing rapidly. You can use PC Card and in a desktop PC using the adapter converting PC Card in the PCI fee, i.e. One network interface board for two computers. You can take a PC card to a business trip or to work and use it in your desktop PC in the office.

MINI-PCI.

A mini-PCI type board is a reduced version of the standard PCI board for desktop PC and is suitable for installation in small mobile computer devices. It provides almost the same features as the usual PCI fee, but its size is about four times less. The mini-PCI type board can be installed in laptops (optionally, at the request of the buyer). The serious advantage of the board of this type (using the radio channel) is that it leaves a free connector for installing a PC Card in which you can insert a memory extension or graphics accelerator. In addition, the cost of the wireless network interface board based on mini-PCI technology is usually lower. However, these boards also have drawbacks. To replace them, as a rule, it is necessary to disassemble the laptop, which is why the manufacturer's warranty can be lost. The use of a mini-PCI type board can also lead to a decrease in performance, since part of the processing (if not all processing) they pin on the computer.

CompactFlash.

For the first time, CompactFlash technology (CF) was proposed by SanDisk Corporation in 1994, but the wireless network interface CF form factor until recently was not produced. The CF card of a small size, weighs 15 g (half of the ounce) and twice the thinner PC Card. Its volume is four times less than that of the radio payment type PC Card. It has a low power consumption, thanks to which the power batteries serve significantly longer than when using PC Card devices.

The most common adapters for wireless LANs have a PC Card Tour II form factor. To connect to a PC, they are equipped with either a 16-bit PCMCIA host interface, which can be compared with an old ISA computer bus, or a 32-bit CardBus host interface that is an analogue of the PCI bus. For normal operation, 11-Mbit / s 802.11b adapter is quite enough bandwidth of the 16-bit interface, but 802.11a and 802.11b standards boards, working faster, must have the Cardbus interface - many laptops are equipped with them. It should not be thought that if the mobile computing device is new, it is necessarily equipped with a Cardbus slot. For example, the PC Card expansion unit for popular HP iPAQ pocket computers supports only 16-bit PCMCIA boards.

Most of the newly released laptops are equipped with a built-in 32-bit MINI-PCI host interface. Usually the Mini-PCI slot is under the lid on the bottom panel of the laptop. Very often, the MINI-PCI wireless network adapters are pre-installed by manufacturers on their cars. If there is no such adapter in your laptop, you can buy and install it yourself.

Stationary PC connects to a wireless LAN using either a wireless network PCI adapter, or a USB wireless interface. To install a PCI adapter, certain skills are needed, and it is worth noting here if system unit PC is located under the table, then the antenna of this adapter also turns out - you see, not the best place For her from the point of view of ensuring reliable radio communications. Wireless uSB interface It is much more convenient to install, besides, it can be placed so that nothing prevents the reception and transmission of radio signals. However, if this interface is used, a slight decrease in the data transfer rate compared to that of the PCI adapter may be observed.

1.4 Access points

The relationship between individual custom wireless network devices and the network interface board is provided using an access point.

System Software Access Point provides interaction of the parts of the wireless LAN and the distribution system of the access point. This software differentiates access points to the degree of controllability, installation and safety functions.

In most cases, the access point provides an HTTP interface that allows you to change its configuration using a custom device equipped with a network interface, and a web browser. Some access points are also equipped with the RS-232 serial interface, which can be configured through a serial cable or a user device that performs the terminal emulation and executing the Telnet program (Hyperterminal).

2. Wireless Local Network Technologies

Most often, wireless local networks are created in accordance with 802.11 and HYPERLAN / 2 standards. We will look at them.

2.1 Standard 802.11

The IEEE 802.11 standard describes a general access control protocol to the transmitting environment (Media Access Control, Mac) and several physical levels of wireless local networks. The first edition of the 802.11 standard. It was adopted in 1997, but then wireless local networks were not widely used. The situation has radically changed in 2001, when prices for components decreased sharply. The IEEE 802.11 Standard Working Group is actively working on improving the standard, seeking to improve the characteristics and security of wireless local networks. Standard 802.11 regulates the use of physical level using IR radiation, but currently there are no products in the market that correspond to this version of the standard.

2.2 LEVEL OF MAC channel level 802.11

Standard 802.11 describes one MAC level, which provides a plurality of functions to ensure the performance of 802.11 wireless local networks. The MAC level controls and supports communication between the stations of 802.11 standards (network interface radio waves and access points), coordinating access to the shared medium (in this case to the radio. The "brain" of the network, the MAC standard of 802.11, manages the physical level of 802.11, such as 802.11A, 802.11b or 802.11g, in order to solve the tasks to determine the employment or unconditions of the medium, transmission and reception of the framework of the 802.11 framework. Before transferring the frame, the station should access the environment, i.e. Shared radio channel stations. Standard 802.11 regulates two forms of access to the environment: distributed coordination function (DISTRIBUTED COODINATION FUNCTION, DCF) and point coordination function (POINT COODINATION FUNCTION, PSF). The support for the DCF mode is required and is based on a protocol that provides multiple access with the control and prevention of conflicts (Carrier Sense Multiple Access with Collision Avoidance, CSMA / CA). When working in DCF mode, the station compete for the right to access the environment and are trying to transfer frames if at this time no other station transfers (Figure 2.1). If some station transfers the frame, the rest are waiting for the canal release.

Figure 2.1 Distributed medium access form

As an environmental access to the environment (Figure 2.1), the MAC level checks the value of its network distribution vector (Network Allocation Vektor, NAV), which is located at each station the counter whose value corresponds to the time required to transmit the previous frame. The NAV value should be zero to try to try to send frame. Before sending a frame, the station calculates the time it is necessary for its transfer based on the volume of the frame and the data transmission rate on the network. The station puts the value corresponding to the named time in the Duration field (Duration Field) of the frame header. When the station receives a frame, it checks the value in its duration field and uses it as the basis for installing its NAV. Thanks to this process, the medium is reserved for use by its transmitting station.

An important aspect of the DCF mode is the rollback timer (Back-off Timer), which the station uses if the transmission environment turns out to be occupied. If the channel is used by another station, which wishes to transfer the frame to the station must be in standby mode, some random period of time and only after that again try to access the environment. This eliminates the possibility that several stations intending to transfer frames will begin to send them simultaneously. Due to the accidental delay, different stations are expected to transmit rights over different periods of time, so do not check the environment for employment in the same point in time and, finding that the channel is free, do not begin to transmit, thereby creating a collision. The rollback timer significantly reduces the number of collisions and, accordingly, repeated programs, especially when the number of active users is large.

When using local networks based on the radio channels, the transmitting station cannot listen to the medium for the occurrence of a conflict during data sending, since it is not capable of using its receiver during data transmission. Therefore, the receiving station must send confirmation (Acknowledgement, ACK) that it did not find in the resulting error frame.

If the transmitting station does not receive ASK for a certain period of time, it assumes that the collision occurred or the frame was damaged due to radio interference, and transmits it again.

In order to support the operational transmission of frames (for example, video signals), standard 802.11 optionally proposes the PCF mechanism, when using the access point guarantees a specific station access to the medium by surveying the station in a period of competing. Stations cannot transmit frames until the access point survey them for transmission frames. Time periods for data traffic based on the PCF mechanism (if possible) occur alternately with the competition periods.

The access point polls the station according to the questionnaire, then goes into competition mode, in which the stations use the DCF mechanism.

Due to this, both modes of operation are supported - synchronous and asynchronous. However, there are no network interface cards or access points that are capable of working in PCF mode.

One of the problems associated with PCF is that few suppliers support it in their products. Therefore, the possibilities commonly provided by this mechanism are inaccessible to users. However, in the future, products will support PCF, since this mechanism allows you to get the necessary quality of service (QoS).

Consider the main functions performed at the MAC level of 802.11.

Scanning

Standard 802.11 regulates both scanning options-- active and passive. During this process, the network interface radio settlement is searching for access point. Passive scanning is mandatory, when it is embedded, each network interface board scans individual channels in order to detect the best signal from the access point. Access points periodically in broadcast mode are sent a beacon (Beacon). The network interface radio payment takes these beacons and take note of the level of the corresponding signal. These beacons contain information about the access point, including its service zone identifier (Service Set iFentifier, SSID) and supported data transfer rate. The network interface radio settlement can use this information along with the signal intensity data to compare access points and make a decision on which one should connect.

Optional active scanning is carried out in a similar way, to the impression that this process is initiated by a radio network interface. It sends a broadcast sensing frame (Probe Frame), and all access points that are within a radius of action send it an answer to the probon (Probe Responce). Thanks to the active scanning of the network interface, the network interface can immediately receive answers from access points, without waiting for the transmission of the beacon signal. However, with active scanning on the network there are non-production costs caused by the transmission of the probationary frameworks and responses to them.

Stations operating in the non-planning network mode, in Standard 802.11 are called an independent basic service area (Independent Basic Service Set, IBSS). When working in this mode, one of the stations always sends beacons, thereby notifying new stations about the availability of the network. Responsibility for the transfer of this beacon lies at each station waiting for the end of the beacon interval (Beacon Interval) is still some random time. The station transmits the beacon if after the beacon interval and some random period expires this station will not receive a beacon signal from any other station. Thus, the responsibility for the transmission of beacon signals is distributed between all stations.

Authentication

Authentication is a process during which identity is checked. Standard 802.11 regulates the two forms: an open authentication system and authentication with a shared key. Open system Authentication is mandatory and carried out in two stages. The network interface radio collection initiates the authentication process by sending an access point for an authentication request frame. The access point meets the response frame to an authentication request, containing permission or failure in authentication, which is indicated in the Status Code (Status Code) field of the frame of the frame.

Authentication with shared key is optional and carried out in four stages. The process is based on the definition of whether the authenticated device has the correct WEP key. "The network interface radio settlement starts it, sending an access point for authentication to authentication. Access point, by placing Call Text (Challenge Text) to the Answer Frame Body sends it to the network interface . The network interface radio settlement uses its WEP key to encrypt the call text and sends it back to access point in another authentication frame. Access point decrypts the call text and compares it with the original. If both texts are equivalent, the access point suggests that the network interface radio pay is correct key. Access point Ends the exchange sequence by sending an authentication frame interface radio interface with a resolution or refusal network. Many hackers know how to overcome the barrier created by authentication with the joint key, so relying on such a security system if you need to provide high level Safety is not worth it.

Binding

After the authentication process is completed, the network interface radio settlement must be attached to the access point, only after that it can send data frames.

The binding (Association) is required to exchange important information between the radio interface of the network interface and the access point, for example, on supported data transfer rates. The network interface radio settlement initiates the binding process by sending a frame with a binding request containing data such as SSID and a supported data transfer rate. The access point is responsible by sending a response frame to a binding request containing the association identifier and other information on the access point. After the network interface radio payment and the access point will complete the binding process, they can transmit one other data frame.

WEP.

If the optional WEP mode is available, the wireless network interface board, before passing any frame, encrypts its body (but not a header) using general key. Receiving station, having received a frame, decrypts it using a common key. Standard 802.11 does not regulate the key distribution method, which makes wireless Local 802.11 standard networks vulnerable to listening. However, version 802. HI of this standard increases the degree of security by introducing 802.11x mechanisms and more reliable encryption.

RTS / CTS.

Optional transmission availability mechanisms (Request to Send) and receiving availability (Clear to Send) allow access point to monitor the process of using the transfer media that activated the RTS / CTS function. When using most of the network interface radio library, users can set the maximum frame volume, when the network interface radio settlement is exceeded by the RTS / CTS mode. For example, when specifying a frame volume of 1000 bits, the RTS / CTS mode will be used for all frames with a volume of more than 1000 bits. Through the use of the RTS / CTS mode, the problems of the hidden node are softened (when two or more radio messages of the network interface cannot hear one other, although they are tied to one access point).

If the network interface radio settlement has activated the RTS / CTS mode, it is before sending the data frame, sends the access point of the RTS frame. The access point answers it by the CTS frame, thereby indicating that the network interface radio settlement can send a data frame. Simultaneously with the shipment of the CTS frame, the access point suggests the duration of the frame duration of the frame header, which holds other stations from the transfer to the station that transmitting the RTS frame can be transmitted and the data frame. This avoids the collisions caused by the problem of the hidden node. The exchange of RTS / CTS frames accompanies the transmission of each data frame, the volume of which exceeds the threshold installed on the corresponding radio interface radio wave.

2.3 Physical levels of the 802.11 standard

Several physical levels of the 802.11 standard are satisfying the various requirements for networks with different applications.

Initial 802.11

Initial Standard 802.11, ratified in 1997, includes the physical levels on which the spectrum expansion is performed by jumping frequency (Frequency Hopping Spreadrum, FHSS) and high-speed transmission with the spectrum expansion by direct sequence (High-Rate Direct Sequence Spreadrum, HR- DSSS). The data transfer rate reaches 2 Mbps, the connection is carried out in the 2.4 GHz band "When using the FHSS technology, broadband signals occupy the entire range of 2.4 GHz, allotted for such purposes.

You can configure access points operating in FHSS mode, 15 different frequency switching schemes so that they do not create mutual interference. Thanks to this, up to 15 access points can effectively work in the FHSS water and the same zone mode.

Since the current version of the 802.11 standard with the FHSS mode provides the maximum data transfer rate of only 2 Mbps, few companies offer FHSS-based solutions for wireless local networks intended for deploying indoors. Current networks are currently available based on 802.11A, 802.11b and 802.11g standards. In addition, the FHSS mechanism is not able to interact with other physical levels of the 802.11 standard. However, the Networks based on FHSS are a good solution for "point-several point" systems, designed for outdoor deployment. This is due to the fact that FHSS technology is more resistant to radio interference, the level of which outside the premises may be very high.

The DSSS Standard 802.11 systems also provide a transmission rate of only 2 Mbps, but are compatible with the latest physical level, 802.11b. Therefore, the user in the laptop of which is installed radio-pay interface of the 802.11 DSSS network interface, can interact with 802.11b access access points. However, this situation is unlikely, since the radio payment of the 802.11 DSSS standard network interface is no longer sold.

802.11A.

At the end of 1999, IEEE issued a standard 802.11 A, which regulates the data transfer in the 5 GHz band using the orthogonal frequency division multiplexing technology (Orthogonal Frequency Division Multiplexing, OFDM), and the data transfer rate is provided up to 54 Mbps. However, products that implement this technology have not been available until 2000, mainly due to difficulties arising from the development of electronic circuits operating in this range.

The 802.11A standard devices are operated in the range of 5 GHz, providing data transfer rate to 54 Mbps with a radius of up to 90 m, which depends on the actual data rate. Points of access and radio payment interface of the 802.11A network interface appeared on the market at the end of 2001, so the share installed equipmentcorresponding to this standard is insignificant compared to the number of 802.11b standards. It is recommended to carefully examine compatibility problems that may occur when the 802.11 A network is deployed.

An important advantage of the 802.11A standard is that it offers an increased bandwidth due to the use of 12 individual, non-recipient channels. it a good choice If necessary, support many concentrated in a small zone of users and high-performance applications, such as streaming video. In addition to higher characteristics than 802.11b systems, 802.11A networks have a higher bandwidth than 802.11g networks.

Another advantage of the 802.11A standard is that the 5 GHz range is still not widely used, which allows users to achieve high performance. Most of those who create interference devices, such as microwave ovens and cordless phones, operate in the 2.4 GHz band. Since the potential of radio domain in the 5 GHz band below, the deployment of the wireless LAN is less risky.

The potential problem of the networks of standard 802.11 A is their limited range of action, which is mainly due to their work in the range of higher frequencies (5 GHz). When operating at speeds up to 54 Mbps, the range of 90 m is limited in most cases. In order to ensure the operation of the network within the specified zone, it is necessary to set more access points than when using the 802.11b devices.

However, if you compare the networks of standards 802.L1B and 802.11A, it turns out that the user of the 802.11A network has the ability to transmit data at a higher speed for the same distances as the user of the 802.11b network network before it loses the ability to establish a connection. But at the same time, the 802.11b network user user can continue to work with a low data transfer rate - 1 or 2 Mbps - large distances than characteristic of the 802.11A network.

Undoubted complexity is that standards 802.11A and 802.11b / g are incompatible. So, the user, the computer device of which is equipped with a radio wave of 802.11b standard, cannot be attached to the access point corresponding to the 802.11A standard, and vice versa. Manufacturers solve this problem by offering multi-mode radio payments that support both standards - 802.11A and 802.11b.

The 802.11A standard modulator converts a binary signal to an analog form using various modulation methods, depending on which data transfer rate was selected. For example, when operating at a speed of 6 Mbps, the PHYSICAL LAYER MEDIUM DEPENDENT, PMD) uses binary relative phase manipulation (Differential Binary Phase SHIFT KEYING, DBPSK), in which the phase phase shifts are shifted, reflecting various combinations of binary discharges . With higher transmission rates (54 Mbps), quadrature amplitude modulation (QAM) is used. In this case, the data bits are represented by changing the central transmission frequency, as well as changes in the amplitude of the signals in addition to the phase shifts.

802.11b.

Along with the 802.11a IEEE standards ratified the standard 802.11b, which is an expansion of the initial standard 802.11, based on expanding the spectrum by the method of direct sequence in the range of 2.4 GHz. The transmission rate at the same time reaches 11 Mbps. The access points and radio information interface of the 802.11b network interface began to appear on the market since 1999, therefore a significant number of networks established by the present time comply with the 802.11b standard.

An important advantage of the 802.11b standard is that the corresponding devices provide it with a relatively large range. It can be calculated that in most cases the use of indoors the range of communication will exceed 270 m. The increased radius of action allows you to establish a significant number of access points when deploying a wireless LAN in the same building where the 802.11A network can be installed.

The lack of an 802.11b standard is that only three non-reciprocating channels can be selected in the 2.4 GHz band. Standard 802.11 Determines 14 channels (only channels from the 1st to 11th are allowed to use in the United States, to work in which access points can be configured, but each of the transmission channels occupies about a third of the total range of 2.4 GHz. Many companies use only non-recipient channels 1, 6 and 11 so that the access points do not create mutual interference. This limits the total bandwidth of the 802.11b networks, so they are well suited only to perform an average performance application applications, such as email and watching Web pages.

Another disadvantage of 802.11b networks is their potential susceptibility to interference from other radio devices. For example, wireless phone, operating in the range of 2.4 GHz, can create serious interference to the wireless LAN standard 802.11b, which is why users feel the deterioration of its characteristics. microwaves And other devices operating in the range of 2.4 GHz can also interfere.

802.11b devices are used by DSSS technology to scatter the signal of the data frame for subchannels of the range of 2.4 GHz, the width of each of which is 22 MHz. This leads to an increase in the noise immunity of the communication compared to when signal transmission is carried out in a narrow frequency band. Therefore, FCC allows you to acquire a license to use devices that work with the expansion of the spectrum.

The standard modulator802.11b converts the extended binary signal to an analog form using various modulation methods, depending on which data is transmitted. For example, when operating at a speed of 1 Mbps at the PMD level, a binary relative phase manipulation is used (Differential Binary Phase SHIFT KEYING, DBPSK). The modulator simply shifts the phase of the central transmission frequency so that in the data stream can be distinguished binary 1 from binary 0.

For transmission with a speed of 2 Mbps, PMD uses the relative quadrature phase manipulation (Differential Quadrature Phase Shift Keying, DQSK), which is similar to DBPSK, except that four possible phase shifts are used to represent every two data bits. Due to this ingenious process, it is possible to transfer a flow of data at 2 Mbps when using the same bandwidth, which is necessary for transmission at a rate of 1 Mbps in the case of other modulation methods. Similar methods are used in transmitting data with higher speeds - 5.5 and 11 Mbps.

802.11G.

IIEE ratified the 802.11g standard in 2003. It is compatible with the 802.11b standard and regulates the increased transmission rate (54 Mbps in the 2.4 GHz band).

It uses multiplexing with orthogonal frequencies (Orthogonal Frequency Division Multiplexing, OFDM).

The strength of the 802.11g standard is that it is inversely compatible with standard 802.11b. Companies that have already unfolded 802.11b networks, in general, can upgrade access points to ensure their compatibility with standard 802.11g devices, simply by upgrading software and hardware. it effective method Translation of the network company to a new level. But the existing client devices of the 802.11b standard during operation in the 802.11g standard require the introduction of protection mechanisms that limit the characteristics of the wireless local network as a whole. This is due to the fact that the 802.11b devices due to the differences in the modulation methods used cannot determine when the 802.11g standard devices transmit. Therefore, both types of devices should declare their intention to use the transmission medium using the type of modulation clear for both.

The disadvantages of 802.11b standards, such as the susceptibility to potential radio interference and the presence of only three non-interpretable channels, and inherent in the networks of 802.11g standards, as they work in the same range of 2.4 GHz. Therefore, the network of standards802.11g have limited bandwidth compared to the 802.11A networks.

2.4 Wi-Fi

Alliance Wi-Fi (Wi-Fi Alliance), which began its work under the name "Wireless Ethernet Compatibility Association" or simply "WECA Association" (Wireless Ethernet Compatibility Alliance, WECA) is an international non-commercial organization engaged in marketing and interaction issues Components of wireless LANs of the 802.11 standard standards. Alliance Wi-Fi is a group that spins the Wi-Fi brand, which falls under all varieties of wireless networks, complying with the 802.11 standard (802.11A, 802.11b and 802.11g), as well as all the standards of this type that will appear in the future . The Wi-Fi Alliance also promotes Wi-Fi's secure access technology (Wi-Fi Protected ACCESS, WPA), a link between the WEP repeatedly criticized mechanism and 802.11 defense standards.

Alliance Wi-Fi has the following goals:

Provide worldwide certification that encourages manufacturers to adhere to 802.11 standards when developing wireless local network components;

Promote sales of certified Wi-Fi products for applying them at home, small offices and enterprises;

Test and certify Wi-Fi products in order to ensure network interaction.

Wi-Fi certification is a process due to which the possibility of interaction between the components of wireless local networks, such as access points and radio payments, made in various form factors. To obtain a certificate to their products, the company must become a member of the Wi-Fi alliance.

The Alliance is guided by the approved testing programs for product certification for interaction with other certified Wi-Fi components. After the product is successfully tested, its manufacturer gets the right to use the "Certified Wi-Fi" logo for each individual product, as well as on its packaging and instructions for use.

Wi-Fi certification gives customers confidence in that. that they acquired the components of a wireless local network that meet the requirements of ensuring interaction with products of many other manufacturers. The Wi-Fi logo on the product means that it meets compatibility testing requirements and will surely work together with Wi-Fi-certified products of other suppliers.

The WEP mechanism does not provide a sufficient level of security for most applications performed in wireless local networks of enterprises.

Since it uses a static key, WEP is easy to hack using already existing software. It encourages information technology managers to use more dynamic WEP forms.

However, these improved security mechanisms are proprietary, which makes it difficult to ensure their support to client devices from other suppliers. Therefore, the Wi-Fi alliance made considerable efforts for effective standardized protection of wireless local networks, identifying the WPA mechanism as providing network interaction. When using WPA, a network medium formed by radio wavelets of the network interface of different types of 802.11, can enjoy the benefits of extended encryption forms.

wireless Network Interface Protocol

2.5 Hiperlan / 2

Hiperlan / 2 standard for high-performance local radio network (High Performance Radio LAN) is a standard for a wireless local network developed by a broadband access unit for radio channels (Broadband Radio Access Networks (BRAN) Division) of the European Telecommunication Standardization Institute EUROPEAN TELECOMMUNICATIONS STANDARTS INSTITUTE, ETSI). This standard regulates the use of efficient, high-speed wireless local network technology, which satisfies all the requirements of the spectrum distribution rules adopted in Europe.

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When all components for the connection from the Internet are already purchased, you can start connecting. So, configuring the Wi-Fi wireless network depends on the main device represented by a personal computer, a laptop. Setting worldwide network The Internet directly depends on the operating system of the personal computer.

Any Wi-Fi camera for Windows is also running, after taking into account the features of the equipment provided. The user-chosen system necessarily contains a window that displays a special network connection management item.

If you need to install wireless connection In Windows XP, you should consider the difference between the current product of computer companies and previous versions.

Configuring Wi-Fi Wireless Network in Windows XP is considered more complicated than in Windows 7.

Windows XP. First, the user must select the "Start" menu of the control panel Network connections" Then find the "wireless connection" and click on it. After enabling this command, the connection is adjusted, but you should view the available wireless networks by selecting the appropriate item.

For the main device to work in a specified direction, it is required to "change the order of network preference". When a new window appears, you can already put a marker near " Using windows To customize the network, "and click on" Advanced ". Next, it will be necessary to return to "Change the procedure for network preferences" and remove the marker with the "key is automatic". Then the network data is entered, and "OK" is pressed to confirm.

Wireless network access for Windows 7

Configuring Wi-Fi Wireless Network in Windows 7 begins with the "Control Panel", in which " Extra options Systems.

Then the transition to the "Computer Name" tab and clicks the Edit option.
After that, the action on the monitor appears window with the names of the computer or domain. The personal working device itself must have a unique name. If this name had to be changed, then the computer is restarted.

Setting the parameters for connecting the Internet in Windows 7

Next click on the wired connections icon, which is located in the lower right of the monitor. Here a "network management center and shared access" appears. It must be selected by pressing the confirmation key. From the list that appears, you allocate the "Add" option and create a computer-computer network. To continue clicking "Next".

In the fields with the names and network parameters, the data is addicted to the need. Then confirm the actions and include general access Connections to the Internet. Wireless Wi-Fi Windows 7 will start working immediately after clicking Close.

Connecting Windows 8 to Wi-Fi

Initially installed settings on personal computers or laptops do not always allow you to connect to a wireless network without any problems. After all, the Windows 8 operating system may not see wireless adapterAlthough it is necessarily present.

Configuring Wi-Fi Wireless Network in Windows 8 usually begins with pressed icon with an asterisk. After that, a list of proposed wireless networks appears on the monitor. One of them should be selected by typing the required security code. The above action is confirmed by the "Next" button.

When it comes to home network, it is better to choose sharing. With a normal connection, the asterisk near the division icon disappears, and the signal acceptance level begins.

Conducting wireless communications with tenth versions

Operational windows system 10 different from previous versions additional settingsproviding for use touch screens. The necessary drivers are also automatically updated here. Because of this additional feature Setting up Wi-Fi wireless network in Windows 10 does not cause special difficulties. The user can simply click on the icon in the lower right corner of the monitor and decide on the available network.

Connect Wi-Fi on Windows 10

It is also possible to automatically select the connection, putting a tick near the corresponding item. If the Wi-Fi adapter is not connected, then a cross is depicted on a marker with divisions instead of an asterisk. It is easy to fix by pressing a specific button.

Most often, the wireless network is protected by a password that you want to enter into the window that appears when connected, and confirm.

On modern computers and laptops there is already a built-in special radio receiving for sending and receiving information at a distance without using wires. For this reason, setting wi-Fi connections Take place without much difficulty.

In wireless networks, the same components are used as in wired networks, but wireless networks should be able to convert information into a form suitable for transferring it through an air environment (medium). Although the wireless network directly includes only a part of the entire network infrastructure, the decrease in the parameters of the entire network is called, undoubtedly deterioration caused by the application of the wireless transmission medium.

Wireless networks include computer devices, basic stations and wireless infrastructure.

Network interface board, or Network Adapter (Network Interface Card), provides an interface between a computer device and a wireless network infrastructure. It is installed inside a computer device, but external network adapters are used, which, after switching on, remain outside the computer device.

Standards for the wireless network are determined how the network interface board should function. For example, a board corresponding to the IEEE 802.11b standard can interact with only a wireless network, the infrastructure of which corresponds to the same standard. Therefore, users must be attentive and take care that the fee chosen by them corresponds to the type of infrastructure of the wireless network to which they want access.

The main component of the wireless LAN - the network interface radio settlement, is often implemented based on the 802.11 standard. These radio payments usually work at one physical level - 802.11A or 802.11b / g. As a result, the radio settlement must implement the version of the standard compatible with the wireless LAN. Radio payments of wireless local networks that implement several versions of this standard at once and providing a higher interaction ability (interoperability) are becoming increasingly common.

The wireless network interface board is also characterized by a form factor determining physical and electrical parameters Bus interface that allows the board to interact with a computer device.

Radio payments are supplied in various form factors: ISA, PCI, PC Card, Minipci and CF. PCs typically use ISA and PCI cards, and PCCard, Mini-PCI and CF adapters.

Industry-Standard Architecture (ISA)

Industry-Standard Architecture (ISA) is an architecture corresponding to the industrial standard. The ISA bus has gained widespread since the beginning of the 80s. Although its characteristics were very low, almost all PC manufacturers until recently installed at least one connector for the ISA tire. But its characteristics could not improve the same quick as the parameters of other computer components, and high-speed alternatives to this bus are already available. The ISA bus did not have a serious impact on the characteristics of the wireless local networks of the 802.LIB standard. It is not necessary to acquire new ISA cards, as they are already outdated.

PERIPHERAL COMPONENT INTERCONNECT (PCI).

Today, the local bus connection of the peripheral devices is the most popular interface for PC, since it has high characteristics. Initially developed and released PCI in 1993. Intel, and this tire still satisfies the needs of the latest models of multimedia computers. PCI fees became the first to be implemented by the "Plug-and-Play" technology, a significantly facilitating network interface board to a computer. PCI circuit solutions can recognize compatible PCI cards and start working with a computer operating system to configure each board. It saves time and avoids errors when installing in inexperienced users.

The PC Card design fees were developed in the early 1990s by the International Memory Players Association for IBM PC personal computers (Personal Computer Memory Card International Association, PCMCIA). PC Card is a device size with a credit card containing external memory, modems, connection devices to external devices, as well as providing compatibility with a wireless network for small computer devices, such as laptops and PDAs. The most widespread and even more popular than boards for ISA or PCI tires, as used in laptops and PDA, the number of which is growing rapidly. You can use PC Card and in a desktop PC using the adapter converting PC Card in the PCI fee, i.e. One network interface board for two computers. You can take a PC card to a business trip or to work and use it in your desktop PC in the office.

A mini-PCI type board is a reduced version of the standard PCI board for desktop PC and is suitable for installation in small mobile computer devices. It provides almost the same features as the usual PCI fee, but its size is about four times less. The mini-PCI type board can be installed in laptops (optionally, at the request of the buyer). The serious advantage of the board of this type (using the radio channel) is that it leaves a free connector for installing a PC Card in which you can insert a memory extension or graphics accelerator. In addition, the cost of the wireless network interface board based on mini-PCI technology is usually lower. However, these boards also have drawbacks. To replace them, as a rule, it is necessary to disassemble the laptop, which is why the manufacturer's warranty can be lost. The use of a mini-PCI type board can also lead to a decrease in performance, since part of the processing (if not all processing) they pin on the computer.

For the first time, CompactFlash technology (CF) was proposed by SanDisk Corporation in 1994, but the wireless network interface CF form factor until recently was not produced. The CF card of a small size, weighs 15 g (half of the ounce) and twice the thinner PC Card. Its volume is four times less than that of the radio payment type PC Card. It has a low power consumption, thanks to which the power batteries serve significantly longer than when using PC Card devices.

The most common adapters for wireless LANs have a PC Card Tour II form factor. To connect to a PC, they are equipped with either a 16-bit PCMCIA host interface, which can be compared with an old ISA computer bus, or a 32-bit CardBus host interface that is an analogue of the PCI bus. For normal operation, 11-Mbit / s 802.11b adapter is quite enough bandwidth of the 16-bit interface, but 802.11a and 802.11b standards boards, working faster, must have the Cardbus interface - many laptops are equipped with them. It should not be thought that if the mobile computing device is new, it is necessarily equipped with a Cardbus slot. For example, the PC Card expansion unit for popular HP iPAQ pocket computers supports only 16-bit PCMCIA boards.

Most of the newly released laptops are equipped with a built-in 32-bit MINI-PCI host interface. Usually the Mini-PCI slot is under the lid on the bottom panel of the laptop. Very often, the MINI-PCI wireless network adapters are pre-installed by manufacturers on their cars. If there is no such adapter in your laptop, you can buy and install it yourself.

Stationary PC connects to a wireless LAN using either a wireless network PCI adapter, or a USB wireless interface. To install a PCI adapter, certain skills are needed, and here it is worth noting that if the PC system unit is located under the table, then there is also an antenna of this adapter - you agree, not the best place for it in terms of ensuring reliable radio communications. The USB wireless interface is much more convenient to be installed, besides, it can be placed so that nothing prevents the reception and transmission of radio signals. However, if this interface is used, a slight decrease in the data transfer rate compared to that of the PCI adapter may be observed.

Access points

The relationship between individual custom wireless network devices and the network interface board is provided using an access point.

System Software Access Point provides interaction of the parts of the wireless LAN and the distribution system of the access point. This software differentiates access points to the degree of controllability, installation and safety functions.

In most cases, the access point provides an HTTP interface that allows you to change its configuration using a custom device equipped with a network interface, and a web browser. Some access points are also equipped with the RS-232 serial interface, which can be configured through a serial cable or a user device that performs the terminal emulation and executing the Telnet program (Hyperterminal).