Polycom H340 - Manual (Page 9)

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Deploying SpectraLink e340, h340 and i640 Wireless Telephones BEST PRACTICES GUIDE
October 2010
2400 MHz
2483 MHz
2412 2417 2422 2427 2432 2437 2442 2447 2452 2457 2464
1 6 11
2
3
4
5
7
8
9
10
22 MHz
Figure 3 - 802.11b Channels
2.2.2 AP Transmission Power and Capacity
The AP transmit power should be set so that the handsets receive the required minimum signal strength, as defined
in Section 2.1.2 of this document. For deployments with higher AP density, lower transmit power settings are
typically required to prevent channel interference. Maximum AP power settings vary by band and by channel, and
can vary between countries. Local regulations should always be checked for regulatory compliance considerations.
In addition, maximum power output levels may vary by AP manufacturer. Where possible, all APs should be set to
the same transmit power level within a given radio type.
It is crucial to then set the transmit power of the handset to match the transmit power of the APs for that band. This
will ensure a symmetrical communication link. Mismatched transmit power outputs will result in reduced range, poor
handoff, one-way audio and other quality of service or packet delivery issues. SpectraLink Wireless Telephones
support transmission power settings in the range from 5mW to 100mW (in the United States). The transmit power
setting on the handset should match the AP’s actual configured transmit power. Any AP antenna gain will increase
signal gain in both directions.
Regardless of the selected power level settings, all APs and handsets must be configured with the same settings to
avoid channel conflicts or unwanted cross-channel interference. For access points that support automatic
transmission power adjustments, Polycom recommends using only static power settings to ensure optimal
performance.
In mixed 802.11b/g environments, Polycom recommends configuring the transmit power of the 802.11b and 802.11g
radios to the same setting, if they are separately configurable. For example, set both radios to 30mW to ensure
identical coverage on both radios. For mixed 802.11a/b/g environments, where the AP utilizes all three radios types,
AP placement should first be determined by modeling for the characteristics of 802.11a, since this environment will
typically have the shortest range. Then, the transmit power of the 802.11b and 802.11g radios should be adjusted to
provide the required coverage levels and cell overlap for those networks, within the already established AP locations.
2.2.3 Interference
Interference on a wireless network may originate from many sources. Microwave ovens, Bluetooth devices, cordless
phones, wireless video cameras, wireless motion detectors, and rogue APs are among the many potential interfering
RF (radio frequency) sources. In general, devices that employ or emit radio frequency signals within a given radio
coverage area will have the potential to cause unwanted interference.