SmartSight Networks Inc MF24 ユーザーズマニュアル
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3.2 Coping with Interference
In most countries, the 2.4 GHz license free band is not regulated by a government
agency and this absence of frequency coordination can result in interference
between various systems. Fortunately, there are existing tools that can be used to
avert interference:
(1)
RF channel selection
(2)
PN code selection
(3) Security
code
(4) Antenna
selection
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Interference is probably not a concern for a Multisite network installation in a rural area.
In urban area, radio licenses are limited creating an increased demand for wireless
products at 2.4 GHz. The potential for interference is therefore greater in urban areas.
It is recommended to do a site survey with a spectrum analyzer before planning the
Multisite network to identify zones of potential interference within the band.
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Interference is probably not a concern for a Multisite network installation in a rural area.
In urban area, radio licenses are limited creating an increased demand for wireless
products at 2.4 GHz. The potential for interference is therefore greater in urban areas.
It is recommended to do a site survey with a spectrum analyzer before planning the
Multisite network to identify zones of potential interference within the band.
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(1) RF
channel
selection
At 2.4 GHz, eleven (11) non overlapping channels are available. This selection
enables the co-location of eleven (11) Multisite networks in the same area without
substantial performance degradation.
enables the co-location of eleven (11) Multisite networks in the same area without
substantial performance degradation.
(2)
PN code spreading and selection
The Microflex employs direct sequence spread spectrum coding. With this
coding scheme, a pseudo-random sequence (PN code) is used to spread the
signal over a much wider band than required by the base-band modulated data.
The wider the signal is spread, the better the radio receiver is at discriminating
between a valid signal and an interfering signal.
coding scheme, a pseudo-random sequence (PN code) is used to spread the
signal over a much wider band than required by the base-band modulated data.
The wider the signal is spread, the better the radio receiver is at discriminating
between a valid signal and an interfering signal.
The Microflex uses 16-bit PN sequences. Some radios implement longer
sequences (64 bits or more), however most unlicensed products (such as 802.11
compliant wireless LAN radios) use 11-bit PN sequences to maximize data rate
within a given bandwidth. With a 16-bit sequence, the Microflex module provides
sufficient interference rejection in most environments and to most unlicensed
products.
sequences (64 bits or more), however most unlicensed products (such as 802.11
compliant wireless LAN radios) use 11-bit PN sequences to maximize data rate
within a given bandwidth. With a 16-bit sequence, the Microflex module provides
sufficient interference rejection in most environments and to most unlicensed
products.
The best PN codes are pseudo random, non-correlating sequences of bits. With
such PN codes, two independent radio links at the same frequency will not
interfere with each other. The signal isolation provided by two distinct PN codes
is proportional to the PN code’s length.
such PN codes, two independent radio links at the same frequency will not
interfere with each other. The signal isolation provided by two distinct PN codes
is proportional to the PN code’s length.
The Microflex module supports nine (9) non-correlating PN codes. Given
sufficient antenna separation, It can be possible to co-locate nine (9) non-
sufficient antenna separation, It can be possible to co-locate nine (9) non-