802.11b

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Introduction

Ratified in 1999, 802.11b was the first standard in the family to become popularized. By using the same underlying techniques as the original 802.11 standard, it allowed mature products to reach the market very quickly after ratification. The significant increase in speed and more rigid requirements helped to push adoption and allowed 802.11b to usher WiFi into the mainstream.
Note that due to similarities between the various WiFi standards, this article discusses factors specific to the 802.11b variant. Please see the WiFi article for detailed information on those common characteristics.
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Modes

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Infrastructure

The most common 802.11b mode, infrastructure networks are based around devices called access points. When running in this mode, the access point acts as a central control station for the network and provides access to a wired network. This provides more stable communications and makes it easy for wireless devices to connect to the Internet.
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Ad-Hoc

The WiFi standards offer an additional mode called ad-hoc that allows stations to communicate directly with one another. This allows devices to form networks to be set up in the field without the requirement for additional equipment.
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Performance

802.11b networks provide a maximum theoretical throughput of 11mbps. As range increases and signal strength becomes weaker, the network will automatically step back to slower speeds (5.5/2/1mbps) to maintain the connection. This provides an adaptive system that provides the maximum throughput possible for the current conditions.
It is important to note that the rates mentioned above are theoretical transfer rates and real-world networks will never be able to reach that level. The 802.11 standards have significant overheads that limit practical transfer rates to a maximum of approximately 6mbps. Additionally, if multiple devices are active on the network that bandwidth must be shared between them.
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Range

Microwave communication is a complex topic so the range that can be obtained with these networks depends on many different variables. In common circumstances, mainstream 802.11b hardware will generally operate within a 90 meter (300 ft) range with best performance in the inner 30 meters (100 ft) of that radius. That range can be dramatically increased or decreased by the environment where the network is being used.
If more range is required, larger antenae and/or more powerful radios can be used to expand the size of the covered area. Most mainstream WiFi equipment is nowhere near the legal limits, so there is often a lot of room for improvement. Additionally, WiFi provides provisions for roaming between several access points, so large areas can be covered by a more complex network.
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Channels

While the official 802.11 specifications provide for up to 14 possible channels, most countries to not allow the use of them all. In North America, only 11 of these channels are available to users of WiFi equipment. In most other countries (Europe and most of Asia), the first 13 channels are available. The only country currently allowing all 14 channels is Japan.
Unfortunately, when used for WiFi these channels are aranged in a manner where they overlap one another. See the following diagram for an illustration of this arangement:


The 802.11b specifications require approximately 22MHz of bandwidth for each network that is in use. The channels, however, are configured in 5MHz increments so networks should be at least five channels away from others in the area. As such, approximately three 802.11b networks (operating on channels 1, 6 and 11) can operate without overlapping one another¹. Placing channels closer together will result in interference and negatively effect the throughput and range of both networks.
If more networks are required, four channels (1, 4, 8 and 11) can be used with only minimal negative effects. While these channels will still overlap, they do so at the periphery of their range so the effects are minimized.
It is important to note that the 2.4GHz ISM band is also used by bluetooth, cordless phones, video cameras and many other wireless devices. Further, some Microwave ovens may also emit significant noise in this band when they are operating. As such, the presence of any of these items within range of a wireless network can cause interference and degrade performance. The 5MHz channels are provided for this reason, as they allow WiFi networks to work around these types of interference.
¹WiFi signals do not have firm boundaries, instead they slowly decay as you get further from the centre of the channel. The 802.11 standards define the boundaries of the channel as the points where the signal is reduced to -30dB (1/1000th) of their maximum strength.

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Extensions

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'802.11b+' (Unofficial)

In late 2002 TI provided a chipset that allowed devices using it to operate at 22mbps. This system was backwardly compatible with conventional 802.11b equipment (running at 11mbps), but allowed radios to switch to the faster mode when both ends supported it. This was a proprietary extension and not part of any official IEEE standard, however it was available from a number of different equipment vendors.
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See Also

• 802.11 - Ratified in 1997, 802.11 was the basis of all other WiFi standards.
• 802.11a - Also ratified in 1999, this 5GHz variant of the standard provided higher throughput but wasn't backwards compatible with it's predecessors.
• 802.11g - A variant of the standard that provides 802.11a speeds but uses the 2.4GHz band and maintains backward compatibility with 802.11b.
• 802.11n - Still in the ratification process, this next generation protocol incorporates new technology to significantly boost throughput and range.