Most of us use wireless networks these days – at home, in public places, sometimes at work – yet even among those of us who specify and buy the kit there’s a widespread lack of knowledge about how Wi-Fi really works.
This is hardly surprising, since the quality of the information out there on the internet is pretty ropey (although nowhere near as bad as the info you’ll find printed on the boxes or in the instruction manuals of typical Wi-Fi kit).
I’ve seen advice such as, “if you find your neighbour is using a particular Wi-Fi channel, try switching your own router to one of the adjacent channels”, and “there are 13 usable Wi-Fi channels, so even in a crowded area you should be able to find a free one”. As you’ll see if you read on, both of these statements betray quite remarkable ignorance about 802.11 wireless networking.
So let’s start with a quick technical overview of Wi-Fi as it stands today, and how it got here. Back in the early 1990s, there were several different wireless networking products on the market but no standard.
The original 802.11 specification also allowed transmission rates of just 1 or 2Mbits/sec, which may sound slow now but back in the 1990s was plenty fast enough for most jobs
The market was dominated by names such as Xircom, Netwave, Proxim and even IBM, but none of their kit could talk to each other. Then, in 1997, the original 802.11 standard was ratified, which finally enabled interoperability between different manufacturers’ products.
The original 802.11 used the 2.4GHz frequency band (from 2.412 to 2.484), which is one of the ISM bands originally reserved by international treaty for industrial, scientific or medical purposes. Interestingly, when these ISM bands were initially defined, “communication” was specifically excluded from their uses.
More recently, the bands have been opened up for other uses, so that non-IT applications regularly employ it (2.45GHz, for example, which is slap-bang in the middle of the Wi-Fi spectrum, is the frequency of the magnetron inside the microwave oven that warms your soup).
The original 802.11 specification also allowed transmission rates of just 1 or 2Mbits/sec, which may sound slow now but back in the 1990s was plenty fast enough for most jobs. Don’t forget that most internet access was still via 56Kbits/sec dial-up lines back then.
As you can see in the Wi-Fi Timeline box, in addition to the 2.4GHz band certain Wi-Fi variants such as 802.11a and some 802.11n kit operate at 5GHz. I’ll ignore these for the rest of this column, since most domestic and SME kit runs at 2.4GHz, and that’s what you’re most likely to encounter.
802.11 actually splits the 2.4GHz radio band into a number of fixed-frequency channels, with the main 13 channels starting at 2.412GHz for channel 1 and increasing in 5MHz increments, so that channel 13 is at 2.472GHz. The odd man out is an extra channel 14, which sits 12MHz above channel 13, but you can safely ignore that unless you’re reading this in Japan – the only country where it can be legally used.
Likewise, channels 12 and 13 are illegal in the USA, which is why the first thing most wireless networking boxes do when you set them up is ask what country or region you’re located in.
Some sneaky UK-based users living in wireless-congested areas such as large apartment blocks have been known to tell their kit that they live in Japan to allow them to use channel 14. That’s illegal, so there’s no way that I could possibly recommend that you try it.
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