WeekEnd Feature: The road goes ever on…

by Ian Thompson, CCSP Staff Editor
June 12, 2004

This week, I have been mostly eating … sandwiches. Oh, and biscuits – after all, a coffee only fills so far without something to be going along with it. “What” I hear you ask “has lead you to this height of culinary excess?” Well, I’ve been back to school, on the other side of the desk in the classroom for a week, and there was the phrase ‘buffet lunch provided’ on the course description… Time to put on the thinking heads.

What’s new at the Academy?

In truth, my IT-Tech team (all four of us) were offered places on a course that qualified for 100% funding from the European Union. Yippee! This is the reason why the UK has paid £104 billion into the EU coffers in the last 10 years and I thank the tax-payers of this fair land for the interesting trays of sandwiches and rolls, snacks and fruit. The course leads to CWNA – Certified Wireless Network Administrator – which is a vendor-neutral course that doesn’t place massively high prerequisites like, say, insisting that we were all at least half-way through our Cisco CNA.

This is, you realise, not a regular ‘jaunt’ away from the ball and chain that is English state-sector teaching today. It is, as far as I can recall, only the second time I have received such individual training (away from the regular ‘whole staff’ stuff we get five days a year). I suspect that the school wouldn’t even have considered it had it not been free, but that sheds light on the other problem facing most public-sector organisations – money is generally a problem. My school puts something like £10k per year to one side to pay for training of all staff (in total over 120) and I know that I’m setting out on a fruitless journey by asking for just one MCSE or CCNA out of that – commercial skills cost commercial sums.

Thankfully, there are various ways of working around that, and there are trusts, funds and schemes to provide part (if rarely all) of the funding. My youngest team member is now starting out on the path to Certification at about one quarter of the full cost, which was a nice surprise for all involved – not least the school, which had found the full amount out of some specialist funding and was prepared to pay this. Not as a ‘necessary evil’, but more as a realisation, finally, that this is the going rate and we need those skills. With the ‘change’, we can afford to send the other technicians on courses to suit their skills and needs, which is nice.

‘Ere, look! I’m Certified!!!

To which the world replies “You look it!”

In truth, what is the issue behind certification of skills? After all, most of us are capable of just getting on with things as required. We don’t forget crucial stuff like passwords, we can learn things in many different ways (hearing, reading, doing, watching – each of us in our own way), and generally take what we need from the experience. So long as we adopt the new information that we’ve experienced and make use of it in a productive way, our employers can put a value judgement on the success of the training.

So why certify? Well, I suppose it could look nice – a smart new certificate framed on the office wall (careful not to obscure any of the ‘Dilbert Wall’, obviously) – but more importantly, it offers tangible proof that we’ve reached a standard or level. We have something in our hands to show what new things we have in our heads. And it can’t harm to mention at future job interviews.

Sometimes, like on this course, a lot of the content is fixing what we already know, as well as introducing additional skills to make things run more smoothly. It gives us a great opportunity to try out alternative pieces of equipment and to look at the finer details of the systems we may already have specified, installed and are running. It’s also an opportunity to dig out some of the stuff we never thought would be used again… I mean, I’ve been sifting through the ol’ memory to recall schoolboy physics, diploma-level acoustics and degree-level lighting to hook into the principles of aerial design and wireless regulations.

Have you got the right driver?

I was going to call this ‘the perils of upgrading’, but I think I’ve used that once or twice before…

Various driver sets are available for WiFi kit, and each is market-specific. Let me explain…

I’ve specified a wireless infrastructure system at work, in the UK, covered by the ETSI regulatory body. ETSI have different standards from those in the US (FCC) and Japan. Broadly speaking, with the exception of Japan (on its own), the world falls into either ETSI or FCC camps, with slight variations to suit local cases. In case you’re wondering what the ‘split’ looks like, check out this spreadsheet – a Cisco range calculator – and look on the ‘2.4GHz Regulatory Info’ worksheet.

We had an unusual problem with our WiFi kit, however. Whenever one of our wirelessly-connected XP pro laptops went to hibernation, and most of the time when they just went to some intermediate level of power saving, they would BSOD and reboot within about a second of reawakening. The UK drivers did not have any option to alter the power saving features of the WiFi card, so a more recent one was sourced.

This was a US driver, but hey, at least it had more than just one measly option in the config box, and crucially it let us turn off the inbuilt power saving, and give control of this back to the OS. No more BSODs, and more stable transfers from a driver set approx 10 months younger than the boxed ones.

It was only whilst studying last week that I realised I might have problems. There I was, only concerned that the laptops might not fail through continually crashing etc, and it turns out I should be more worried about the differences between ETSI and the FCC. Crucially, the FCC allows much more power to be radiated from a transmitter than ETSI. I am no longer certain that my systems are within the limits for my locale.

Typical, everything’s bigger in America…

Yeah, but don’t get me quoting Stranglers lyrics – I’ve used up my EU-regulated lyric quota for this month with the ‘Spamming’ article a couple of weeks back.

The ETSI regulations stipulate a 100mW maximum transmitter power (EIRP – look it up…). This is enough for most needs, but studying the various dBm, dBi and dBd figures suddenly flipped a light on in my head. It is technically possible to blow the regulation figures if I pump my 100mW (steady now!) signal through an upgraded antenna. Heck, even a simple dipole will push it beyond the ETSI figure, let alone Yagi or dish versions.

The FCC seems to take a more liberal approach, allowing 4W. Flip these two limits into dBm and you get ETSI at 20dBm and FCC at 36dBm. When you start adding 13dBi Yagis onto such a card, you can see that such a setup at 100mW transmission power (which is itself 20dBm) is fine in the US, but is way over the ETSI limit – even an upgraded dipole breaks it. It seems that the £300 or so 28dBi dish antenna that we were trying is way above the maximum allowed here, but it gave about one-third of a mile range before we lost line-of sight.

But is it the hardware or the driver that controls the maximum radiated power? If it’s hardware then I’m fine – it’s UK-spec stuff and will still be within limits. If it’s the drivers – oh dear. Do you see where I’m heading? It’s possible that my search for a more stable WiFi driver could mean 100% power on the newer US version is actually a higher power than 100% on the older UK one – and the config only talks about percentage power values, not absolute mW levels.

I suspect the hardware is actually the governing item since the amplifier is on board – the driver may still have an part to play, though, since it could use firmware to limit the standard hardware (a bit like the way a modem can understand different dialling patterns in different countries). There is the small matter of the various difference frequency bands, but in this case it’s the US that is more strict.

Stop! My head’s hurting!

What does this all mean? We’ll, if you’re reading this in one of the ETSI countries, don’t assume that you can jack every transmitter up to 100mW – the aerial is more crucial in maintaining the balance, and some of the 25-mile, long distance stuff is illegal. If you’re reading it in FCC-regulated areas, make sure you get the transmitter and antenna in the same kit of parts (or ‘system’) because there the regs talk about the entire power of the system (transmitter, cables and antenna together).

Next week’s lesson; we will be having a short written class test on the bandwidth and Fresnel Zone. Please read chapters 4 and 7 of your text book.