Wireless Networking
Computers can be linked together with cables or the connection can be wireless (though radio communication).
Sometimes, cabling computers together is just not an option. For example: the computers must be mobile (like on a building site); they can be used in places that would be expensive to wire; the network is only temporary; or the building is protected by Heritage Listing that forbids drilling into walls and floors to lay cables.
In such cases, wireless networking is a nifty alternative. And it's not too complicated.
Instead of a normal network card, the PC (often a laptop) uses a wireless network card.
It communicates with the network using a tiny radio radio transmitter and antenna in the card. Of course its range is limited (depending on the obstacles between the card and the nearest network wireless basestation, it may reach 100-200 metres.)
Obviously the network can't hear the card unless it also has a wireless transceiver (receiver/transmitter). This is the base station.
It also has a wireless NIC in it, but since it is fixed in place, it can afford to have a more elaborate antenna (the white thing in the picture.) The base station plugs into the network like any other node.
COOL FEATURES
- Users can connect to the network anywhere in the range of the wireless infrastructure: they don't have to be tied to a location by a cable in an inconvenient place
- Many wireless devices can connect to a single base station
- Most sites have more than one base station, strategically located around the site. When communicating with a wireless PC, the wireless system will poll its base stations to find which one has the best connection to the PC and will automatically switch to that base station for communications with that PC.
- If the wireless PC is mobile (e.g. being wheeled around the building doing an inventory), the wireless system acts like a cellular phone network: as the PC moves out of range of one base station, the network instantly switches from that base station to another that will give a better connection.
- Communications between the base station and the wireless PC are encrypted for security.
So why aren't all networks wireless, if they have so many cool features? It comes down to cost versus benefit, really.
A wireless NIC costs about $AUS400 - and if you have 100 computers, that's some serious money. If most of the computers are going to be sitting on the same desk all their lives, a cabled connection is far cheaper.
Wireless networking is often a great add-on to a traditional wired network: most of the workstations are wired, but there are some that are wireless because of the way they are used (e.g. managers who are forever roaming the building having meetings can stay in constant contact with the network and are not restricted by cable locations.)
Wireless Local Area Network
A useful article taken from Computers Now sales brochure of October 2004
Making sense of it all..
A wireless local area network (WLAN) is actually nothing more than an invisible extension of the visible hardwired network most schools already have. The wireless links in a wireless network are made possible by two key sets of components: access points and wireless network adapters. Access points are radio transceivers operating on one or more frequencies and acting like satellites to send, receive, and manage information from all the computers and devices in the network. Wireless network adapters are radio transceivers housed within each computer that establish communications with the access points. Signals from an access point can travel roughly 100 metres outdoors and considerably further with addon antennas. Their efficacy indoors varies depending on obstructions, the number of users, and the industry standard they are based on.
Which one is right for your school?
There are many products on the market that conform to different wireless standards such as 802.11 a, 802.11b, 802.11g, and Bluetooth. To make an educated network building decision, one must understand the relative pros and cons of each of these technologies.
802.11
In 1997, the Institute of Electrical and Electronics Engineers (IEEE) created the first WLAN standard. They called it 802.11 after the name of the group formed to oversee its development. Unfortunately, 802.11 only supported a maximum bandwidth of 2 Mbps - too slow for most applications. For this reason, ordinary 802.11 wireless products are no longer being manufactured.
802.11b
IEEE expanded on the original 802.11 standard in July 1999, creating the 802.11b specification. 802.11b supports bandwidth up to 11 Mbps, which is comparable to traditional Ethernet.
802.11b uses the same radio signaling frequency - 2.4 GHz - as the original 802.11 standard. Being an unregulated frequency, 802.11b gear can incur interference from microwave ovens, cordless phones, and other appliances using the same 2.4 GHz range. However, by installing 802.11b gear a reasonable distance from other appliances, interference can easily be avoided.
802.11a
When 802.11b was developed, IEEE created a second extension to the original 802.11 standard called 802.11 a. Because 802.11b gained in popularity much faster than did 802.11 a, many believed that 802.11 a was created after 802.11b. In fact, 802.11 a was created at the same time. Due to its higher cost, 802.11 a fits predominately in the education/business sector, whereas 802.11b better serves the home market.
802.11 a supports bandwidth up to 54 Mbps and signals in a regulated 5 GHz range. Compared to 802.11b, this higher frequency limits the range of 802.11 a. The higher frequency also means 802.11 a signals have more difficulty penetrating walls and other obstructions. Because 802.11 a and 802.11b utilize different frequencies, the two technologies are incompatible with each other. Some vendors offer hybrid 802.11 a/b network gear, but these products simply implement the two standards side by side.
802.11g
In 2002 and 2003, WLAN products supporting a new standard called 802.11g began to appear on the scene. 802.11g attempts to combine the best of both 802.11 a and 802.11b. 802.11g supports bandwidth up to 54 Mbps, and it uses the 2.4 Ghz frequency for greater range. 802.11g is backwards compatible with 802.11b, meaning that 802.11g access points will work with 802.11b wireless network adapters and vice versa.
What Is Bluetooth?
Essentially, Bluetooth is a cable replacement technology in the form of a standard specification that permits electronic devices such as camcorders, PDAs, and computers to establish a wireless iink for convenient data exchange. A typical application would be to walk up to a printer and beam the document you want printed directiy from your laptop. The Bluetooth standard is supported by the Bluetooth Special Interest Group, a trade association with more than 2,000 members, including IBM, Intel, Microsoft, and Nokia. Bluetooth-equipped devices transmit data to each other within a 10 metre distance at about 1 or 2 Mbps utilizing the 2.4 GHz frequency band. This is the same band on which the 802.11b wireless systems operate, posing the potential for signals to interfere with each other, though technologies currently exist to minimize such interference.
Bluetooth devices also may beam signals to each other to create what is sometimes called a "personal area network," though such a network cannot offer the robust operations provided by networks based on the 802.11 family of standards.
Bandwidth.
As discovered by the millions of home users who have migrated from 56 kbps modems to broadband DSL or cable connections, higher bandwidth means less waiting while your computer accesses information from somewhere else.
When wireless networking was first introduced into schools, the 1 or 2 Mbps data transmission rate that the first iteration of the 802.11 standard offered was a limiting factor. The available bandwidth of an access point could be diluted beyond ideal quantities, particularly when users simultaneously browsed websites, opened large files, or worked with multimedia applications. That problem was lessened with the IEEE 802.11b standard, which delivered about 7 Mbps of a promised 11 Mbps transmission rate to a single user. Remember that this is shared bandwidth; the more users that are connected and actively using the system, the less bandwidth available to each user.
However with the latest 802.11g standard, demand for increased bandwidth has been addressed and bandwidth log jams experienced with the earlier standards are no longer an issue.