RTS TR-240 Especificaciones descargar pdf (Pagina 63)

802.11 Wireless / RF Interference

The BTR-240 system offers many benefits by operating in the

2.4GHz ISM frequency band. The main reason is that it allows

users to operate without a license requirement in most countries.

The 802.11 protocol also has world-wide acceptance which

permits users to travel with their system to locations where

802.11 devices are allowed.

Along with the many benefits of the 802.11 technology, there are

some constraints. Because the 802.11 protocol is license-free and

so widely adopted, there exist numerous devices that utilize these

frequencies all over the world. These devices must coexist and

share the RF spectrum. When multiple devices that are sharing

the RF spectrum are located in close proximity to each other, they

create wireless interference.

Wireless interference for 2.4GHz could come from a wide

variety of sources including: Bluetooth enabled devices,

microwave ovens, cordless telephones, cellular phones with

Wi-Fi capabilities, and other nearby Wi-Fi access points.

In the presence of wireless interference, users of the BTR-240

system may experience performance degradation. Performance

degradation may be in the form of capacity reduction, wireless

range reduction, or audio quality degradation in the form of

“break-up”.

How to Avoid RF Interference?

In some environments, RF interference can be controlled, and in

others, it cannot. There are numerous ways that a BTR-240

system operator can avoid a significant impact to RF interference.

1. Analyze the Environment

•

The ClearScan intelligence in the BTR-240 will scan the

environment for surrounding Wi-Fi access points and

select the optimal RF channel to operate. A ClearScan

should be performed prior to the event. If a user suddenly

experience performance degradation while operating, it

is possible that a new source of RF interference became

present and ClearScan could be run again.

•

There are many RF site surveying tools available that

will detect more 2.4GHz interference than other Wi-Fi

access points. This could be used to identify an optimal

RF channel to operate on.

2. Prevent the Interference from Transmitting

•

In some cases, it may be possible to find the source of

interference and shut it down. Other Wi-Fi devices may

include nearby laptop/desktop computers or Wi-Fi

enabled mobile phones. These devices should be shut

down or their Wi-Fi capabilites could be temporarily

disabled when operating near a BTR-240 system. Other

non-Wi-Fi devices would be Bluetooth headsets,

microwave ovens, and cordless telephones. These

devices should also be turned off and not operating near a

BTR-240 system.

3. BTR-240 Location and Antennas

•

The omni-directional antennas supplied with the

BTR-240 provide a wireless coverage area in a circle

around the BTR-240 equally in all directions which gives

wireless users the ability to roam in all directions. This

also means that the antennas will pick up interference

from all these directions. Make sure the BTR-240 is

located at the center of the wireless coverage area.

•

If the users are co-located, a directional antenna may be

used as a better antenna option. This will provide a

wireless coverage area in one direction and prevent

coverage and interference from other directions.

•

Ensure that a BTR-240 is spaced far enough away from

interfering sources including other access points and

other BTR-240s, even if operating on “non-overlapping”

RF channels. Refer to Table 7-1 in Section 7 for

separation distances.

•

Prevent a BTR-240 from having LOS to other BTR-240s

or access points, even if operating on “non-overlapping”

RF channels.

4. BTR-240 and BTR-24 Cell Type Deployment

•

Multiple base stations (BTR-240s and BTR-24s) can be

deployed and linked to provide a wider coverage area or

wireless coverage in separate locations.

•

If users are co-located in multiple areas and/or separated

by a large distance, linking multiple base stations with

smaller antenna gains would be a better option than a

single base station with large antenna gain to minimize

interference and provide the same coverage area.

•

Keep coverage areas separate and do not allow coverage

areas from multiple BTR-240s, BTR-24s or other access

points to overlap.

5. Reduce the Number of Full-Duplex Users

•

Any users that do not really need to be in full-duplex

mode (transmitting all the time), should be placed in

half-duplex mode (transmitting only while the <TALK>

button is pressed). This reduces the capacity load and

will perform significantly better in an environment that

contains interference.

6. Move Wireless Users to Wired

•

If wireless users are located near the base station and do

not need roaming capabilities, they could be attached to

the base station via Ethernet cable. This would reduce the

wireless capacity load and perform significantly better in

an environment that contains interference.

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RTS TR-240 Especificaciones Pagina 63

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