Wireless Rf Introduction - SonicWALL SonicPoint-N Dual-Band Getting Started Manual

Wireless RF Introduction

There are currently four widely adopted standards for 802.11
wireless network types: a, b, g, and n. Although 802.11n is the
newest and highest capacity standard, each of the four
standards has its own strengths and weaknesses. This section
provides overviews of these standards.
The following section provides a brief overview of RF
technologies:
• Frequency Bands and Channels
• Data Rate and Useful Range
• 802.11 Comparison Chart
• Radio Frequency Barriers
• RF Interference - page 10
Frequency Bands and Channels
To allow multiple separate wireless networks in a shared and
confined space, the RF medium is divided into channels. For
devices in the 5GHz range (802.11a), this means the possibility
of up to 23 discrete channels. For devices using the 2.4GHz
range (802.11b, 802.11g), the wireless space is limited to a
maximum of 14 overlapping channels. As a result of these
overlapping channels, 2.4GHz technology provides only a total
of three discrete channels.
The newer 802.11n technology does not fit into either of these
categories, as it is capable of using both 2.4GHz and 5GHz, but
is limited to 14 overlapping channels for backward compatibility.
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Data Rate and Useful Range
Different 802.11 standards provide different signal
optimizations:
• 802.11b – Provides long distance, although at a lower
maximum data rate (11Mbps per channel), than
802.11a/g/n. In addition, the low data rate can only be used
across 3 non-overlapping channels.
• 802.11a – Provides a high maximum data rate per channel
with the trade-off of shorter useful range. This standard
shines in high-traffic applications because its 54Mbps rate
is available over each of the 23 non-overlapping channels
in the 5GHz range.
• 802.11g – Provides a higher maximum data rate per
channel than 802.11b and a longer range than 802.11a.
However, because it resides in the 2.4GHz range, the
maximum data rate can only be used across three non-
overlapping channels.
• 802.11n – Provides the highest maximum data rate per
channel, double the speed of any previous standard and
double the useful range. In addition, 802.11n commonly
offers Multiple Input Multiple Output (MIMO) technology to
further increase transmission rates. This standard is
capable of using both the 5GHz and 2.4GHz ranges
simultaneously for enhanced throughput.