Современные информационные технологии/ 1.Компьютерная  инженерия

Bulatova M.B.

Kostanay State University named after A. Baitursynov, Kazakhstan

Wireless computer networks

The ability to transmit the information without wires which usually ties the users to a particular point of the space has always been very attractive. And as soon as the technical possibilities became sufficient to form a new wireless services acquired two necessary components of success - easy to use and low cost, - the success was guaranteed. The last proof of this is the Mobile Telephony. However, wireless communication does not necessarily mean mobility. There is a so-called fixed wireless when interacting nodes are constantly located within a small area, for example in the specific building. [1]

Consider the types of wireless communication.

Wireless Ethernet. In traditional Ethernet you can easily use different types of network adapters, hubs and switches, if all network devices are based on one standard of Ethernet. The standard of wireless Ethernet IEEE 802.11b is supported by the trade group WECA. Wireless networks are compatible with IEEE 802.11b standard and operate at maximum speed to 11 Mbit / s what is approximately equal to the speed 10BASE-T Ethernet. IEEE 802.11b standard network can be connected with the usual Ethernet networks or also can be used in "offline" mode. The main advantage of networks IEEE 802.11b is their possibility of combining different equipment.

Wi-Fi technologies. Wireless networks running on standard IEEE 802.11b, use the same band (2.4 GHz) and many portable phones, wireless speakers and devices security systems.

Security and other possibilities. Theoretically, you can connect to a wireless network from anywhere with the appropriate network adapter, because the most models of wireless network adapters and nodes-transmitters use encryption. Some devices allow you to encode security code ESSID. You also should not forget about such standard means of identification in the network as users’ passwords. To provide better security the protection levels on the network adapters and hubs transmitters must match.

Wireless networks can have two logical topologies.

• Star shaped. This topology is used in 802.11b and Radio LAN. The nodal transmitter plays the role of concentrator because all computers are connected via the node transmitter and do not interact with each other directly.

• Point-to-point. Topology "point-to-point" is used in Home RF products and will apply Bluetooth devices. Such devices are directly connected to each other and do not require node transmitters or any other devices like hub to communicate with each other.

Thus, we can conclude that wireless communication is divided into mobile and fixed. The wireless data transmission systems are classified into four groups depending on the range of the electromagnetic spectrum: broadcast (radio) systems, microwave systems, infrared waves systems and visible light systems. The wireless communication link with a single source and several receivers are based on the base station. [1] These lines are used in mobile networks, and also in fixed access systems. Topology with multiple sources and multiple receivers is typical for wireless LANs.

So the main advantages of the wireless network are:

The wireless networks allow you to save at any cabling, if it is impossible for wired access, they are virtually uncontested. [4]

Wireless networks provide the high degree of mobility of users. It’s may have a free movement within a single domain. One more advantage is the ability to a rapid deployment and movement of the network.

The connection speed is quite high and is comparable with wired solutions; with a proper design it may provide the necessary bandwidth for users with any requirements in transmission of data, video, telephony.

And also we point out some disadvantages:

The wireless network security is significantly lower than the wire, though modern standards improve it, but the physical nature of the wireless network is such that the use of this technology for mission-critical applications is not recommended.

The functioning of the wireless network depends on the environment. Any objects in the path of the radio signal reduce its capacity and there may be interference in the operating range of household appliances, most of which are characteristic of microwaves.

Limited frequency range. According to the standard, and in accordance with legal restrictions in our country, we can use 13 radio channels. Historically, neighboring channels overlap and interfere with each other. All this leads to the fact that in the same area may be only three independent wireless network (independent bands).

The list of references

1. Olifer VG Olifer NA Networks. Principles, technologies, protocols: Textbook for universities. 3rd ed. - St. Petersburg.: Peter, 2007. - 958 s.: Il.

2. Computer Systems and Networks: Proc. Manual / VP etc. Kosarev / Under. Ed. VP and LV Kosarev Eremina. - Moscow: Finance and Statistics, 1999. - 464 ..: il.

3. A. Kulakov Omasyansky SV Networks - Select. Installation and use and adm. Kyiv, 1999. - 544.

4. Vatamanyuk AM Wireless network with their own hands. - St. Petersburg.: Peter, 2006. - 195