Siemens EF 711 Series Betriebsanweisung PDF herunterladen (Seite 92)

Configuring the Wireless AP

SCALANCE WLC711

3-4 C79000-G8976-C260-03, 07/2012, User Guide, V8.11

The Unlicensed National Information Infrastructure (U-NII) bands all lie within the 5-GHz band,

designed for short-range, high-speed, wireless networking communication.

The Wireless AP supports the full range of 802.11a:

• 5.15 to 5.25 GHz — U-NII Low Band

• 5.25 to 5.35 GHz — U-NII Middle Band

• 5.47 to 5.725 GHz — UNII 2+

• 5.725 to 5.825 GHz — U-NII High Band

Siemens Wireless 802.11n AP

The SCALANCE IWLAN 802.11n AP delivers total data rates of up to 450Mbps, depending on its

configuration. The improved throughput of 450 Mbps is spread over a number of simultaneous

users so that the Wireless 802.11n AP provides mobile users with an experience similar to that of a

wired 100 Mbps Ethernet connection — the standard for desktop connectivity.

To configure the SCALANCE IWLAN 802.11n AP to achieve this high link rate, see “Achieving

High Throughput with the Wireless 802.11n AP” on page 3-37.

Note:

The Wireless 802.11n AP is backward-compatible with existing

802.11a/b/g networks.

Note:

The Wireless 802.11n AP cannot operate as a stand-alone access point.

MIMO

The mainstay of 802.11 AP is MIMO (multiple input, multiple output) — a technology that uses

advanced signal processing with multiple antennas to improve the throughput. MIMO takes

advantage of multipath propagation to decrease packet retries to improve the fidelity of the

wireless network.

The 802.11n AP’s MIMO radio sends out one or two radio signals through its three antennas. Each

of these signals is called a spatial stream. Because the location of the antennas on the 802.11n AP is

spaced out, each spatial stream follows a slightly different path to the client device. Furthermore,

the two spatial streams get multiplied into several streams as they bounce off the obstructions in

the vicinity. This phenomenon is called multipath. Since these streams are bounced from different

surfaces, they follow different paths to the client device. The client device, which is also 802.11n

compliant, also has multiple antennas. Each of the antennas independently decodes the arriving

signal. Then each antenna’s decoded signal is combined with the decoded signals from the other

antennas. The software algorithm uses the redundancy to extract one or two spatial streams and

enhances the streams' signal to noise ratio.

The client device too sends out one or two spatial streams through its multiple antennas. These

spatial streams get multiplied into several steams as they bounce off the obstructions in the

vicinity en route to the 802.11n AP. The 802.11n AP's MIMO receiver receives these multiple

streams with three antennas. Each of the three antennas independently decodes the arriving

signal. Then each antennas's decoded signal is combined with the decoded signals from the other

antennas. The 802.11n AP's MIMO receiver again uses the redundancy to extract one or two

spatial streams and enhances the streams' signal to noise ratio.

By using the multiple streams, MIMO doubles the throughput.

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