by R. K. Bloom

Building a wireless network, part 2: Bluetooth, 802.11a, 802.11b and 802.11g

Building a wireless network, part 2: Bluetooth, 802.11a, 802.11b and 802.11g

Original: Dandsdata

Since our last meeting with the equipment for wireless networks, it has become more accessible and easier to use, it is not surprising. Other way for the technology simply does not exist.

By reducing the cost and use of improved antennas in commercial samples and in samples for home

use, the wireless web is increasingly entangles city and its suburbs, and humanity, in the meantime, enjoy the fact that more

do not need to lay cables to create a computer network. There are new standards for wireless networks.

The problem, as usual, comes down to what to choose, and why. With this and begin.

Again, Bluetooth – Network USB adapter

Bluetooth is not a protocol for wireless local area networks (WLAN), although, if necessary, the possibility of implementing such a network, all

still there. It is designed to create a WLAN in no more than a USB to Ethernet. Bluetooth is designed for computer peripherals and a variety of devices, not to connect computers Point to Point. Today, Bluetooth 1.1 devices are already widely disseminated, and work well enough.

Bluetooth uses the same allowed (not in Russia) radio range of 2.4 GHz, which built on and WLAN IEEE 802.11b, but it has a much

less bandwidth, and is not intended to work at a great distance. Bluetooth will work through a wall or two, despite the weak transmitters, which are commonly used in equipment of this standard. It is assumed that it is used to group devices, which are located quite close to each other, so you can connect them to cable. And well, that there was

wireless connectivity for such devices.

Some motherboards, notebooks and various computer manufacturers known, already have built-in Bluetooth adapters, as well as cell phones top price category, handheld PCs and other equipment. You can establish a Bluetooth on any PC with a USB port

using the small USB adapter into a keychain.

A year ago, with a Bluetooth device for home and office use have been too far from us. Now there is a large

number of devices with its support, and a lot of software with its support, so that the purchase Bluetooth adapter for PC

  1. will be fully justified.
  2. Billionton USBBT02-X – Bluetooth adapter for USB – device manufacturing company of the same name, has a very small size (59 x 20 x 8 mm). It can be purchased online for $ 45. The adapter is ideal for connecting to a USB hub, your laptop or PC with front USB ports …

Complete … provided USB extension cable, for easy connection to the USB ports located on the rear of the chassis.

This adapter belongs to the third class, which implies a maximum distance of ten meters (without obstacles). It

enough for most tasks, which are designed Bluetooth, but if you need more distance, you probably

want to buy an adapter class 1. In this case, the radius of the increase up to 100 meters.

If you want to use Bluetooth to connect two computers, you can use different models of adapters Billionton, but we

it seems that most buyers would stop at some one. With their help, you can download pictures from your phone with a built-

camera, sync your PC with the organizer, or something else.

In fact, if you combine the two computers using Bluetooth, youll see something similar to that shown in Fig. This is roughly similar to what you see when you connect to a PC of some other Bluetooth devices. Of course, the difference in the features of its operation.

Nice looks in the screenshots, works quite well, but its one of those, interesting, not Windows-standard interfaces. Who uses Internet Explorer to access FTP are already familiar with this style. Bluetooth Setting the window is too difficult to change the size, especially when you see the available services of other devices. This behavior seems a little strange.

The operating system sees a connection to Bluetooth, a serial port is fast enough (it is about five times faster than conventional COM or IrDA), and, if desired, you can organize the Windows network connection through it. One of the greatest achievements of Windows 95 brought into the world of Wintel (enough to laugh, young people in baseball caps visors ago) was the possibility of a simple association of one or more network protocols and clients to perform various network services on arbitrary network interfaces. Once Bluetooth has become just another kind of network interface in terms of Windows, just an opportunity to bind to it the appropriate protocol (TCP / IP …) and services (the Client for Microsoft Networks (Client for Microsoft Networks), service access to files and printer (File and Printer Sharing) …) on their computers.

Remember that the speed of such connections is not high – a closer look later. But if you use Bluetooth for a wireless connection between two computers, the speed will be sufficient to ensure that under normal network operations, you do not

had to be taken by surprise, and thinking what to do until the updated Network Neighborhood.

And, of course, Bluetooth allows you to play games with their colleagues, located behind the wall without an increase in UDP traffic, visible on the network

company.

You can even set an access point Bluetooth, which work just like conventional access point WLAN; you connect it to a wired network, and up to seven Bluetooth-enabled devices at the same time be able to connect to the LAN through each such access point, using PPP over Bluetooth. An interesting article about this implementation and a comparison with 802.11b, see here – just do not take the value of the speed wireline modems at the end. For download speed Bluetooth like DSL, but the modems for leased lines, whose capacity is not greatly curtailed the provider can show the result to a few hundred kilobytes per second when working with fast servers. Bluetooth with such speed can not work.

Everyone knows about the TCP / IP and access points on the division of Internet access and wireless headsets. What is really useful in practice, Bluetooth (perhaps to synchronize organizer with PC, but not for us to judge) – for transferring files back and forth. But if your Bluetooth device will not use a special program, you have to work for the good old FTP. One folder for each of the devices in the Bluetooth connection is available for use by another user, and you get access to it, just like any other FTP server, all you have to do this – to know the user name and password for another device.

In our tests, the effective transfer rate between the adapters Billionton was from 40 to 50 kilobytes per second via FTP with a small

distance and a low level of noise in the 2.4 GHz band. The theoretical peak bandwidth of Bluetooth is 723 kbit / s, which

is 88 kilobytes per second (remember, this is 1000 kilobits per bit, and kilobytes – 1024 bytes of 8 bits, and if you do not want you to think about how

of illiterate users), but its only a theory.

The values ??of peak bandwidth for a variety of data interfaces are usually the same, the throughput in

really shows how much data can be transmitted per second. Naturally, the number of bytes sent must equal the number received.

Although the peak values ??are not considered official data – not all of the information communicated is custom. If you pass

added quite a lot of overhead. Also in the minutes there is a large redundancy associated with errors

that occur in any wireless system and can significantly affect the throughput.

Thus, 50 kilobytes per second – almost everything you would expect from Bluetooth. This is sufficient for most purposes, but for those looking for a way to transferring 2 GB of MP3 files on a laptop to take with you on the road a little music, and has at his disposal eleven or twelve hours, you should choose something else.

Not the best drivers Widcomm, discussed in the recent review of Bluetooth adapter yet been installed on one of the test machines, they are well recognized Adapter Billionton. Fortunately, the Billionton software installed without problems and without the appearance of 103 dialogs that Widcomm installer offered some time ago (read previous review, if you want to know more).

The software used in conjunction with a Bluetooth adapter, can exert a strong influence on the job. Different stacks of Bluetooth (the program uses a stack of hardware drivers that are hierarchically arranged) must be compatible with each other.

Interface “Setting Bluetooth”, presented by Windows should always be the same, no matter what Bluetooth stack you use, but it does not mean that it will always work. No other version of Windows has no built-stack Bluetooth (yet), so you will be in the same situation as in the old days, when installing Winsock TCP / IP was the best choice for your computer (Win3.1) in the network.

They say that the software Billionton was very good. It still does not guarantee that the adapter will work in conjunction with any other Bluetooth device. We did not have a huge stock of Bluetooth equipment to test for compatibility with each of the devices. But if you still have a problem, then most likely the problem lies in your thousand-handsome phone, not Bluetooth adapter for $ 99. Im sure it will make you feel much better.