Siemens IEEE802.11 Instruções de Operação descarregar pdf (Página 33)

Technical basics

3.4 iREF

SCALANCE W770/W730 to IEEE 802.11n Web Based Management

Configuration Manual, 11/2014, C79000-G8976-C323-03

Restrictions

● iPCF and iPCF-MC are developments of Siemens AG and function only with nodes on

which iPCF / iPCF-MC is implemented.

● With an access point with several WLAN interfaces, it is possible to use both iPCF as well

as standard WLAN at the same time.

● Access points with a WLAN interface cannot take part in the iPCF-MC procedures, iPCF

is, however, possible.

Requirements for iPCF-MC

iPCF-MC uses the two wireless interface of the access point in different ways: One interface

works as the management interface and sends a beacon every five milliseconds. The other

interface transfers the user data.

The following requirements must be met before you can use iPCF-MC:

● Only devices with two WLAN interfaces can be used as access points

● The data interface (WLAN1) and management interface (WLAN2) must be operated in

the same frequency band and must match in terms of their wireless coverage. iPCF-MC

will not work if the two wireless interfaces are equipped with directional antennas that

cover different areas.

● The management interfaces of all access points to which a client can change must use

the same channel. A client scans only this one channel to find accessible access points.

● Transmission based on IEEE 802.11h (DFS) cannot be used for the management

interface. 802.11h (DFS) is possible for the data interface.

● A client must support this feature on its WLAN interface.

3.4

iREF

How it works

If an access point has several activated antennas, the transmit power is distributed equally

on these antennas. The transmit power is subject to country-specific legal restrictions. The

maximum permitted power depends on the gain of the connected antennas. If the connected

antennas have different gains, the maximum antenna gain effectively restricts the permitted

transmit power.

iREF (industrial Range Extension Function) ensures that the data traffic from the access

point to each individual client is handled via the most suitable antenna. Which antenna is

most suitable is determined by the access point based on the RSSI values of received

packets.

Taking into account antenna gain and possible cable losses, packets are only sent via the

antennas with which the maximum signal strength at the client end can be expected.

During this time the other antennas are inactive and the legally permitted transmit power is

available for the selected antenna. The inactive antennas do not restrict the permitted

transmit power.

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