Fig.2: two or more Access Points can be using to create overlapping "cells" and to link networks together (eg, between buildings). An Access Point is also needed to interface a wireless network to a conventional wired LAN.

Wireless networks have two big advantages: con-venience and ease of set up. They’re convenient because there are no cables to install and they’re easy to set up for exactly the same reason.

Usually, a wired network (LAN) is the most cost-effective method but it does tie the PCs to set locations. By contrast, a wireless LAN means that PCs can be moved from one location to another and still have network access – something that can be very useful for mobile users with laptops.

A wireless LAN also has advantages in situations where it’s difficult to install cables or if you don’t want to drill holes through walls. And it can save you from digging up concrete paths if you want to "connect" two buildings together.

In short, if you can’t go through it, over it or around it, a wireless network is the answer.

Wireless network cards

Although still relatively expensive, the cost of wireless networking is now on the way down. Diamond Multimedia’s HomeFree system has been popular at the bottom end of the market, although hampered by its rather leisurely 1Mb/s transmission speed.

By contrast, this new system from Eumitcom Technology (and sold by MicroGram Computers) runs at a brisk 11Mb/s, which is far more useful for business applications. It’s based on PCMCIA wireless networking cards which plug straight into the PCMCIA slots fitted to laptop computers. Howev-er, by using a "PCMCIA-to-PCI Adapter", they can be fitted to conventional PCs as well.

This view shows the Access Point (centre) and two Wireless LAN PCMCIA cards. The PCMCIA cards function as a network card and radio transceiver rolled into one and can be used without the Access Point to create a simple "Adhoc" network - see Fig.1.

Each PCMCIA card is actually a network card and radio tran-sceiver rolled into one. The omnidirectional antenna circuitry for the card is located at one end and protrudes from the laptop (or PC) by about 4cm when the card is pushed into place.

The transceiver operates in the 2.4GHz band using spread spectrum wireless technology, to ensure security and reliability. What’s more, the cards don’t really need a separate base station (or access point) to operate. All you have to do is set up several computers with these cards and you have a working network (this is known as an "Adhoc" network).

Of course, you still have to install the relevant network-ing protocols, set up workgroups and computer names, and share resources, just as you would for a conventional wired network.

The setting up procedure for the PCMCIA card is straight-forward – just insert the card into its slot, reboot the computer and install the driver when prompted. You then install the con-figuration utility software, which is supplied on a separate disk.

Transmission mode

The PCMCIA cards can either be plugged directly into a notebook computer or used with a PC by installing a PCMCIA-to-PCI adapter or a PC Card Drive.

Among other things, the configuration utility lets you set the channel number and the mode – see Fig.3. The mode is set to "Adhoc" for a small stand-alone wireless network or to "In-frastructure" if you intend using an Access Point. There are also options that allow you to encrypt the transmissions.

The configuration utility also shows the current transmis-sion rate (or throughput), as well as the link quality and signal strength from an Access Point.

The effective range for an Adhoc network running at 11Mb/s is about 30 metres (line of sight), although greater distances are possible at reduced transmission rates. In operation, the system can automatically switch down to either 5.5Mb/s, 2Mb/s or 1Mb/s for line-of-sight ranges of 50m, 100m and 120m respective-ly.

PCMCIA-to-PCI adapter

Here’s a device that you probably haven’t seen before – it’s called a "Wireless LAN PCMCIA-to-PCI Adapt-er" and it func-tions as a PCMCIA card to PCI bridge. In a nutshell, this card plugs into a spare PCI slot on your PC’s motherboard and accepts the wireless PCMCIA network card.

The card slot is accessed through a cutout in the back-plane connector – you just slide the card in until it "clicks" home, just as you would with a laptop computer.

Fig.3: the Wireless LAN Configuration Utility, lets you set the channel number and mode. It also shows the transmission rate and indicates the link quality and signal strength from an Access Point.

Fig.4: the Wireless LAN Configuration Utility is automatically launched at start-up and is minimised to the PC's System Tray.

Installing this card is straightforward enough, although your PC will need to have a couple of spare interrupt request lines (IRQs) – one for the adapter card itself and another for the PCMCIA card. The supplied setup diskette includes drivers for Windows 95 OSR2, Windows 98, Windows NT and Windows 2000. The setup program automatically identifies the operating system and installs the correct driver. You then slide the PCMCIA wireless LAN card into place and install the driver for this device.

In case you’re wondering, the PCMCIA-to-PCI Adapter works only with the wireless PCMCIA LAN cards. If you want to use other PCMCIA cards in a PC, take a look at MicroGram’s "PC Card Drive". This device looks very similar to the other unit but has two slots and works with Type 1, 2 & 3 PCMCIA cards.

In fact, it’s the PC Card Drive that’s pictured in this article. Naturally, it’s more expensive than the other adapter card (see below).

Access Point

An "Access Point" is required if you want to connect your wireless LAN to a conventional LAN. In addition, an Access Point effectively doubles the range between wireless PCs on the net-work, since it acts as a base station. You can also set up multi-ple Access Points with overlapping coverage areas so that mobile users can freely roam from one "cell" to the next.

Fig.5: the Access Point also comes with a configuration utility. Clicking the Scan button displays any detected Access Points, as shown here.

Fig.6: double clicking an Access Point in Fig.5 brings up the dialog box shown above, so that you can assign it a temporary IP address.

Similarly, two Access Points can be used to link two build-ing together, using Point-to-Point mode.

Disarmingly simple in appearance, the Access Point is housed in a grey plastic box and is fitted with an omnidirection-al antenna at the back. Also on the back panel are an RJ-45 socket for connection to a standard network hub, plus an RS-232 socket which provides alternative connectivity direct to a PC.

The Access Point also comes with a configuration utility which can be installed on any machine on the network – either wireless or wired.

Clicking the Scan button in this utility detects the Access Point and displays it as shown in Fig.5. You then assign a temporary IP address to the Access Point (see Fig.6), after which you use the Access Point’s built in web server to assign a permanent address and to make other configuration changes (Fig.7).

Alternatively, you can configure the Access Point to obtain its IP address from a DHCP server on the network.

The bottom line

Fig.7: the Access Point comes with an inbuilt web server. This lets you change the configuration settings, including assigning a permanent IP address, subnet mask and default gateway. The IP can also be obtained from a DHCP server.

We tested the system by fitting wireless PCMCIA cards to two computers – one a laptop, the other a conventional PC (via the PC Card Drive). To complete the setup, we plugged an Access Point into the hub on our wired network.

Initially, we set the mode to Adhoc so that we could test the wireless network between the two computers fitted with the PCMCIA cards. The network came straight up – no problems.

We then set the mode to Infrastructure" and scanned for the Access Point. It too came straight up and after running the configuration software, we had access between the wireless ma-chines and the wired segment of the LAN.

In short, it all worked – what more can we say?

Cost and availability

Unfortunately, you’re still paying for the R&D for this type of gear, so it’s not exactly as "cheap as chips". At the time of writing, the Access Point (Cat. 11339) was priced at $1155; the Wireless LAN PCMCIA card (Cat.11340) at $490; and the Wireless LAN PCMCIA-to-PCI Station Adapter (Cat.11344) at $79 (prices include GST).

The PC Card Drive (Cat.6523) retails for $259 but note that you don’t need this card unless you want to fit other types of PCMCIA cards to a PC. Normally, you would use the much cheaper PCMCIA-to-PCI Station Adapter instead.

Further information is available from MicroGram Computers, Unit 1, 14 Bon Mace Close, Berkeley Vale 2261. Phone (02) 4389 8444. Their website is at www.mgram.com.au or you can email info@mgram.com.au for up-to-date pricing.