Wireless LANs

 Becoming more and more frequent are news reports concerning what are termed "scandals" or "sleeze". Have you ever stopped to consider how this is so? Not the "scandal" aspect, because I'm pretty sure that this is endemic... but the increasing frequency of its discovery. How is it that a newspaper gets hold of a lead? Not from the two interested parties in the so-called scandal, for they have nothing to gain and all to lose... the discovery of the latest revelation (Dec 2002) was said to originate from an e-mail....

Becoming more and more popular are local area networks.

As households get more than one computer there is a need to share information between them without the tedium of doing this by floppy disk or CDROM. In addition, it is silly not to share an expensive printer and Internet access when a means of doing this is readily available. This means is the LAN or Local Area Network. It used to be the rule that a LAN was constructed from Ethernet cards and co-axial cable. This is known as 10base-2 or 10base-5, depending on the cable loss and consequent range; it can run at 10Mbps; is relatively easy to implement; operational aspects are easy... but there are practical difficulties when it comes to the routing of cables.

Later, the ethernet was upgraded in performance to 10base-T through the use of twisted pair cables, of which the best is commonly referred to as Cat5 cable. This is a relatively lightweight cable much the same as that used to connect telephones. The plugs and sockets are slightly different, being referred to as RJ45. These systems have a few advantages over coax systems but also some disadvantages.

The first difference is speed. A twisted pair cable may run at 100Mbps, some ten times faster than the old ethernet. This may not be realised in practice however as unscreened twisted pairs may suffer from interference having the effect of reducing throughput. Coax systems are more resilient because they are screened.

Twisted pair networks require a data switch which connects networked computers in a star configuration, something that coax networks do not need. On the downside for a coax network is the fact that the system cable impedance needs to be carefully managed. There must be a precise termination resistance fitted at the end of the run of cable. If a computer is disconnected it must be done in such a way as to preserve the overall cable network impedance. Unplugging a coaxial cable can bring networking to a halt, whereas unplugging an RJ45 cable merely disconnects the associated computer from the network.

Routing of twisted pair cable to install such a network is almost as difficult however as its coax equivalent.

As a means of overcoming this, a wireless technique has been developed. This has been instituted along with legislation to make the transmission of low power signals in certain frequency bands a matter outside the requirement to have a transmitting license.

Currently the 2.4GHz band is most popular for wireless networks. Channels have been allocated and a standard (802.11b) introduced to ensure that development and production of WLANs is consistent. At the moment, data rates in the 2.4GHz band do not permit speeds to be specified in excess of 11Mbps although there are means of improving this. Weak signal performance may reduce the speed progressively until reliable operation is achieved.

A new frequency band is available, very much higher in frequency that will offer very much higher data rates.

Of course, being a radio system, security is compromised. A wired network was pretty secure but a radiated type is not. It is possible to use clever radio transmission techniques and encryption of data to partially solve the open-ness of data transmission but there is always the potential for a hacker to compromise security.

My first venture into LANs was quite recently, Oct/Nov 2002 when I obtained some USB radio modules. These came with a CD supposedly carrying the software for installing the devices into computers using Windows 98 or Windows XP. As is usual one first instals the software then plugs in the USB device. The software rattled into the first computer. A reboot and all seemed well. Plug in the USB cable and the computer freezes. I waited a few minutes and then found that the keyboard was dead. I unplugged the USB cable and the computer unfroze. What was wrong? The help files as usual are only useful once everything is working and one has become an expert in wireless networking. No use at all for sorting out basic problems...in fact the section of the help files dealing with problems was inaccessible due to an error in the acrobat file (on all CDs). I could see the title but nothing else!

Of course one does not immediately think the problem lies with the device or the software. After all. I surely am not the first user of these devices? A call to the supplier reveals that this is so. Many have been sold and no-one has had any trouble.. it must be me then I thought. Maybe it was a subtle combination of software in the computer? I tried to install it in a second computer. No joy here either. Maybe another flukish combination of software? I tried a third computer with pretty nearly the same results.

I rang the supplier again and again. Eventually I began to discover that Windows XP had its own drivers and on this the devices would appeared to have worked. After going round in circles I was eventually supplied with the address of an FTP website with a new driver. Downloading the new driver revealed that indeed the old Windows 98 version must have never been tested successfully!

How many times does this happen? Very frequently I think. I've had motherboards, graphics cards, modems and sound cards all giving trouble until new software has been obtained. I suspect that such is the rush to get things on the market, that software development seems to be inadequate. Insufficient thought is given to the poor end user. The ensuing waste of time is absolutely criminal. There is no advice given that the software may not work and one must waste hours trying to find a solution.

In the case of these WLAN modules the company responsible for their development has changed hands and it is virtually impossible for a typical user to find a solution.

Anyway back to the saga of their installation. Using the new drivers I managed to install a pair of the modules, and after a lot of experimentation, actually got them to communicate. I even managed to get them to talk between ME and XP, but as far as getting a reliable network up and running that still remains a challenge.

Having said all this, which relates to small domestic LANs, what about their use by big business? Wireless LANs have been in use in large businesses for a year or two because they provide enormous advantages in their implementation.

One can access over the Internet, together with the RF channel numbers used, what are termed wireless "hot-spots". These are city areas absolutely clogged up with radio traffic from wireless LANs. Armed with a laptop fitted with a wireless adaptor one can quickly log into a private LAN and with a few keystrokes join a network. Using tried and tested hacking principles, data in any computer within the LAN becomes "public". Download a few "dbx" files and you have a person's entire e-mail history. Not only can one read a simple e-mail, but unlike an ordinary confidential letter, most e-mails carry an entire history of the communication as a new response is often tagged onto a previous mail....

So what easier way is there to make money than sitting outside a building in a London street with a laptop and then selling the proceeds to a newspaper with no scruples, or is it "with the public interest at heart"? OK there is one. You could sit in a hotel room with a scanner set to look at the radio spectrum used by cordless phones or an older scanner (with complete UHF coverage) set to one of the mobile phone bands. Are these illegal activities? Strictly speaking no; it's only illegal to pass on to a third party what one has heard.. but newspapers seem to get away with "confidentiality" arguments after publication even though what they're doing surely is aiding and abetting the criminal activity?

Since writing this a couple of years ago a new device has appeared on the market.

When Broadband became commonly available and all family members wanted to join the Internet revolution as it were, each wanted access from their own computer. I'd been supplying small radio units that enabled a Local Area Network to be established within a customers premises. This, coupled with the features available in Windows 98 and XP to allow sharing of an Internet connection over ones LAN permitted multiple access of a single broadband connection, albeit only when the computer carrying the physical connection to the phone socket was switched on.

The new device, now being supplied by BT, AOL, Wanadoo et al, allows multiple users, equipped with LAN radio access devices, within the same area to use a common Broadband connection. This is intended of course to apply to a family group or a business but radio knows no bounds and will leak as far as the outer limits of the universe if unobstructed. Now that such a Broadband connection is permanent, at least whilst the access unit is plugged into the mains (and who ever unplugs them?), Broadband is now available, theoretically at least, to anyone within 100 metres of such a radio access device. That is, if they are equipped with a LAN radio device of the right specification!

Once all this is made public knowledge, I wonder what the result will be? Well we don't have long to wait, here at least, because the local paper just ran an article on the subject. I suppose one may never know that one's Broadband connection is being used by a neighbour, unless they're into music downloads for example and your download speed suffers, or maybe when you're cut off because your download limit has been exceeded?

Watch this space...

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