The magazine of the Melbourne PC User Group Wireless Network Products: What Do the Standards Mean? Gary Winder |
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Gary Winder explains the topic in a way that many will appreciate as we get closer and closer to wireless networking |
If you have an interest in wireless networking and you've seen ads for such products, you might be a little confused about the speed you can get from the latest and greatest wireless equipment, or what else it might offer, and what other equipment will it work with. It all boils down to the standards to which the particular equipment conforms and whether or not that suits your needs.
There are a lot of terms that may seem confusing to newcomers — terms like WiFi, Bluetooth, and protocols that are ever so similar, all starting with "802.11". They just don't appear to mean very much. This article will focus on the 802.11 standard suite which is relevant to the most popular Wireless devices that PC users like you and I are likely to encounter.
All wireless devices that we can buy from the local PC store operate in two frequency ranges. The first is the 2.4 -2.4835 GHz frequency range, or radio spectrum. The downside of wireless equipment operating in this range is that it has to compete with a multitude of other devices using the same range, such as cordless phones, microwave ovens, Bluetooth devices, video senders, motion sensors, wireless video cameras and other wireless equipment. The second range is the 5.15 - 5.35 GHz and 5.725 - 5.825 GHz radio spectrums, and at the moment there are not as many consumer devices in this spectrum as there are in the 2.4 GHz spectrum, and the spectrum is bigger, which means more space for devices to share.
802.11
The first generation of wireless networking equipment used the 802.11 standard and had a maximum bandwidth of 2 Mbit/s. You don't see much of it today as it was quite expensive when it was first introduced and slow compared to 10 BaseT wired networks. It could connect at either 1 or 2 Mbit/s, dependent upon signal quality. Given its age, it is also referred to as 802.11 legacy.
Although not extremely popular, there are still bits of hardware out there. Just be sure you check out that possibility if you happen to be going to buy some cheap second hand wireless equipment.
802.11b
Wireless networking really took off in popularity with the introduction of 802.11b standard. This had an increased maximum speed of up to 11 Mbit/s and is backwards compatible with the old 802.11 standard because it is simply a high speed extension of the original 802.11 signaling techniques. This also means it can work with both plain 802.11 equipment and 802.11b equipment.
802.11b is also marketed under the term 'WiFi' with a cute little logo.
There are several different speeds at which devices will connect to each other. These speeds are automatically worked out by the devices and are based upon signal quality. So, you may not get 11 Mbit/s, it depends upon things like distance, walls, interference or any combination of those. Connection speeds are 11, 5.5, 2 and 1 Mbit/s.
The attraction with 802.11b equipment is its popularity and affordability as prices have dropped considerably since 802.11 was introduced. As with the original 802.11 equipment, 802.11b has to compete with other wireless devices. The 2.4 GHz spectrum is becoming increasingly populated with devices. It's a bit like a room full of people all trying to talk at once, thus making it harder for you to hear the person you are listening to. There are documented instances in some highly populated areas in the USA of people having issues getting their wireless network to be reliable, as there are so many other people close by with their own wireless networks — they are all competing for the same radio spectrum.
There are also proprietary enhancements to the 802.11b standard, enhancements that can double the transfer rate to 22 Mbit/s. However, these are not supported by all manufactures. They are often advertised as 802.11b+. You cannot be sure that they will inter operate with a different brand that might also have a plus '+' offering available.
802.11a
802.11a was developed after 802.11b. This may seem confusing until you realise that the letter designations represent the work of different IEEE working groups, derived from (and addressing specific problems or limitations of) the original 802.11 standard. It does not indicate the order in which they were released.
The major difference between 802.11b and the 802.11a specification is that the latter operates in the 5.15 -5.35 GHz and 5.725 -5.825 GHz frequency bands with a maximum transfer rate of 54 Mbit/s. The 5 GHz frequency range is not as crowded as the 2.4 GHz spectrum and is bigger. The additional room can help to avoid interference and congestion. Devices that use this standard are usually more expensive. One other issue to note is that the higher frequency tends to attenuate (or get weaker) faster than 802.11b and 802.11g devices, so it is harder to get them working well through walls and over large distances.
802.11g
This standard provides a throughput of up to 54 Mbit/s and it operates in the 2.4 GHz frequency band but uses a different radio technology in order to boost overall bandwidth. This gives you the speed of 802.11a and the same long range reach of the 2.4 GHz range. It offers the speed of 802.11a and the backward compatibility with 802.11b without having to resort to dual band devices. In the real world, devices in the 2.4 GHz band are claimed to get greater coverage than devices in the 5 GHz band.
As 802.11g is a high speed extension of 802.11b, all products that support 802.11g will also support 802.11 and 802.11b clients, so this means a lot of backwards compatibility with older products. It also has the ability to work out the optimum connection speed and can fall back to slower speeds should the signal deteriorate. 802.11g devices can connect at a wide range of speeds, 54, 48, 36, 24, 18, 12, 11, 9, 6, 5.5, 2 and 1 Mbit/s.
Proprietary enhancements are also applied to 802.11g to give speeds up to a maximum data rate of up to 108 Mbit/s.
You can now purchase what are known as dual band cards, even "Tri" bands that support 802.11a, 802.11b and 802.11g all on the one card. This means that the card has additional circuitry for both the 5 Gigahertz and 2.4 gigahertz spectrums. Supporting both spectrums requires more complexity on the device and therefore higher cost.
The other 802.11s...
These are lesser used wireless standards, but are handy to know, nevertheless.
802.11d
This standard allows for a wireless device to configure itself for different "regulatory domains". For example, an Access Point (AP) is configured for use in a country that has different licensing requirements than other countries. A user might travel to this country with his equipment configured in such a way that using it would be breaking the law. However if his equipment supports 802.11d, when it is turned on it would receive 802.11d information from the local Access Point and reconfigure itself for correct operation in that region. This could mean that the maximum transmit power is lowered, or the channel is changed.
802.11e
This standard is becoming more important in the corporate sector, as it implements Quality Of Service (QOS). You may have heard about QOS in other network discussions, such as routers and Wide Area Network links. It is supposed to manage different types of traffic on a link to ensure that time critical data gets through the network link first. This is important if you want to run services on your wireless network that would be unusable or annoying if the data was delayed, such as voice services (voice over IP), audio or video services.
802.11f
If you have a very large network with multiple Access Points (APs) and you wish to roam between them without dropping your connection, then this is the standard your APs need to use. It is an inter-AP protocol that enables APs from different manufacturers to keep track of which one you are connected to, and to enable you to move from one AP to another without dropping the connection.
It also provides a basic security mechanism for the network. If the network sees the same device address (MAC address) used on two different APs, it knows something is wrong (like a hacker) and acts accordingly.
802.11h
This standard was developed in response to possible interference from other devices operating in or near the 5 GHz spectrum such as radars or satellites. It has mainly come about from European regulators and is to enable an 802.11a device to detect other devices in or near the 5 GHz spectrum and take steps to avoid any interference such as selecting a different channel or lowering the power output. This is similar to 802.11d, but for the 5 GHz band.
802.11i
You may have heard that security for wireless connections is very weak. This standard is designed to fix that problem. It is currently a work in progress, but it is expected to offer the best level of security to date in a standard wireless device. It is quite possible that older devices can be upgraded to support this protocol once it is finalised. That is, if your equipment manufacturer wants to offer it as a firmware upgrade instead of preferring you to buy a new product.
802.11j
Only applicable for Japan which has a slightly different radio spectrum allocated for 5 GHz operation (4.9 - 5 GHz)
802.11k
This protocol enables some of the higher level radio management functions to be viewed and managed externally.
802.11ma
Think of 802.11ma as a maintenance update to a few of the protocols listed and mainly consists of technical and documentation updates.
802.11n
Look out for this one. It will be the next big thing in wireless standards if it works out. Still a work in progress at the moment. The aim is to improve speed over existing offerings of up to 100 Mbit/s.
Hopefully now you have a better understanding of what all the 802.11 standards mean, and how each one fits in with your wireless networking plans. So, what should you buy? Well, that's a big can of worms, but the flavour of the month would have to be 802.11g.
Happy networking.
About the Author
Gary Winder, winder@iinet.net.au has been in IT for 15 years supporting PCs, Networks and WANs, and is always looking for new challenges.
Reprinted from the June 2004 issue of PC Update, the magazine of Melbourne PC User Group, Australia
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