Table of various 802.11 standards:

èHSDPA (High-Speed Downlink Packet Access) ofwel Super 3G is een upgrade van UMTS (3G)

802.11n goedkeuring verwacht in 2006

Huidige Pre-N toestellen met 8-maal groter bereik en 6-maal grotere snelheid dan de g-standaard.

MutipleInput/MultipleOutput (mimo); hiermee zijn snelheden tot 300 Mbps mogelijk

Opmerking: # niet op alle Access points terug te vinden

èAirgo Networks ( mimo) vermeldt bij gecomprimeerd verkeer een maximumsnelheid van 120 Mbps, nog altijd sneller dan gangbare bekabelde Ethernet-netwerken.

è 802.11a Channel Numbers

Why is it that 802.11a channel numbers go 40, 44, 36, 48, and so forth, instead of 1, 2, 3, 4, 5, like 802.11b/g channels? What happened to the in-between channels, and why don’t they start with 1?

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802.11a uses frequencies between 5 GHz and 6 GHz, but due to differences between the laws and regulations of individual countries, it doesn’t use exactly the same frequencies in every country. Because of these regulatory differences, the IEEE decided to use a versatile channel numbering scheme. The frequencies between 5 GHz and 6 GHz are divided into 5 MHz intervals, and each interval is assigned a sequential channel number. So, for example, a channel centered on the frequency 5.000 GHz would be channel 0, a channel centered on frequency 5.005 GHz would be channel 1, and so forth. The general formula for converting from a channel number to a frequency is

Central Frequency = 5 GHz + (5 MHz * Channel Number)

This starts to explain why the channel numbers don’t start with 1. In the United States, the rules under which 802.11a operates require that the lowest channel number be 36, which equates to a center frequency of 5.180 GHz. Use of frequencies below that number is prohibited by FCC regulations. So why not just call the channel that is at 5.180 GHz channel number 1? Because devices in other countries can use frequencies below 5.180, so what channel number would they use? Channel -1? A generic channel numbering method for all frequencies between 5 GHz and 6 GHz allows for unambiguous channel numbering no matter what frequencies a given country allows.

802.11a’s channel numbers skip frequencies for two reasons. First, 802.11 channels are spaced 20 MHz apart, to prevent interference between them. This means that two consecutive 802.11a channels have a difference of 4 channel numbers between them. Remember that each 802.11a channel number represents 5 MHz of spectrum, so a 20 MHz channel covers 4 channel numbers. This means that channels 36, 40, 44, and 52 are all consecutive 802.11a channels. Second, the channels skip numbers because the frequency bands 802.11a uses in the United States have gaps in them. This explains any skip in the channel numbers of more than four channel numbers.

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