Lancom 1821n Wireless Manual page 16

LANCOM 1811n Wireless – LANCOM 1821n Wireless
Chapter 1: Introduction
For example, the Access Point splits the data into two groups which are then
sent simultaneously via separate antennas to the WLAN client. Data through-
put can therefore be doubled using two transmitting and receiving antennas.
MIMO Client 802.11n
MIMO AP 802.11n
But how can several signals be transmitted on a single channel simultane-
ously? This was considered impossible with previous WLAN applications.
Let us consider how data is transmitted in "normal" wireless LAN networks:
Depending on antenna type, an Access Point's antenna broadcasts data in
several directions simultaneously. These electromagnetic waves are reflected
by the surrounding surfaces causing a broadcast signal to reach the WLAN cli-
ent's antenna over many different paths; this is also referred to as "multipath
propagation". Each of these paths has a different length meaning that indivi-
dual signals reach the client with a different time delay.
WLAN-Client
Access Point
These time-delayed signals interfere with each other at the WLAN client and
significantly weaken the original signal. For this reason, conventional WLAN
networks should always have a direct line of sight (LOS) between transmitter
and receiver in order to reduce the influence of reflections.
MIMO technology transforms this weakness in WLAN transmission into a
strength that allows an enormous increase in data throughput. As mentioned
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