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 cabled network card, the PC (often a laptop) uses a wireless network interface card (NIC). Most laptops have the wireless NIC built in, and the antenna is concealed in the lid. Older laptops might need a PC-Card NIC to be plugged in...

The wireless NIC communicates with the network using a tiny radio radio transmitter/receiver and antenna. 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, commonly called a WAP (Wireless Access Point).

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.

More modern WAPs feature multiple antennas can can manage neat tasks like load sharing.

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.

Benefits of wired networks

So why aren't all networks wireless, if they have so many cool features? It comes down to security and cost/benefit, really.

A wireless NIC for a desktop computer costs about $20 - and if you have 700 or so 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 - and more reliable.

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.)

Many organisations are fearful of the security holes a wireless component could introduce into their network. A single WAP plugged in to a network point by an employee could expose a LAN to hacking or hijacking exploits that can be hard to prevent or detect.

The other reason for opting for a wired connection is bandwidth. A large LAN with huge data traffic would be strangled by the confines of a 802.11g wireless network's 54Mbps bandwidth - the cheapest CAT cable is capable of twice that, and fibre optic backbones can shunt thousands of times that amount of data across a LAN. It will be long time before any wireless networking can rival that.

Wireless Protocols

The rules governing how wireless communications happen are called 802.11 - or 'wi-fi' amongst friends. There are different 802.11 standards that have appeared over time: 802.11a, 802.11b, 802.11g, and the new standard 802.11n. Each has offered improvements in range, signal quality, performance or security. Here are the pros and cons of each of these:

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.

802.11n

Released in 2009, 802.11n operates around the 2.4GHz frequency at 20 or 40 MHz bandwidth. It can get to between 72 or 150Mbps depending on its mode. Its range is nearly double that of 802.11g.

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 link 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.

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.