ASCOM VoWiFi System System Description page 12

System Description
Ascom VoWiFi System
• Space-time block coding: A transmitter uses more antennas than signal streams to
redundantly transmit the transmit signal. This increases the reliability of the signal at
the receiver, and reduces the error rate.
• Transmit beamforming: A transmitter uses multiple antennas to focus the signal
strength in the direction of the receiver. This increases the signal-to-noise ratio at the
receiver.
802.11n devices can use either 20 MHz or 40 MHz channels. The 40 MHz channels are two
adjacent 20 MHz channels that are bonded together, thereby more than doubling the
effective data rate. It is possible to have one to two non-overlapping 40 MHz channel in the
2.4 GHz band, and nine to eleven in the 5 GHz band, depending on country regulations.
802.11n devices have the option of using a short Guard Interval (GI). GI is the period of time
in between symbols, and are used to reduce the interference between symbols. 802.11a/b/
g devices use a GI that is 800 ns long, but 802.11n devices have the option of using a GI
that is either 800 or 400 ns long.
The 802.11n specification includes the following restrictions:
Radio Band:
Maximum Data Rate:
Operating channels in the 2.4 GHz band:
Operating channels in the 5 GHz band:
Maximum number of non-overlapping 20 MHz
channels:
Maximum number of non-overlapping 40 MHz
channels:
Typical Indoor Range
Typical Outdoor Range (Line of Sight)
a. With basic antenna and maximum power level.
Figure 4. .
Figure 6. 20 MHz and 40 MHz channels in the 2.4 GHz and 5 GHz bands
7 September 2011 / Ver. G
a
:
a
:
2.4 GHz
5 GHz
600 Mbps
Same as 802.11b/g
Same as 802.11a
2.4 GHz band: 3
5 GHz band: 19–24 (depending on
country regulations)
ETSI: 19
FCC: 24
2.4 GHz band: 1–2 (depending on
country regulations)
ETSI: 2
FCC: 1
5 GHz band: 9–11 (depending on
country regulations)
ETSI: 9
FCC: 11
30 m / 100 ft
100 m / 330 ft
TD 92313EN
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