User Guide

Wi-Fi Array
Installing the Wi-Fi Array 61
Figure 23. MIMO Signal Processing
MIMO signal processing uses multiple antennas to send and receive data. It takes
advantage of multipath reflections to improve signal coherence and greatly
increase receiver sensitivity (Figure 23). Multipath signals were considered to be
interference by 802.11a/b/g radios, and degraded performance. In 802.11n, these
signals are used to enhance performance. This extra sensitivity can be used for
greater range or higher data rates. The enhanced signal is the processed sum of
individual antennas. Signal processing eliminates nulls and fading that any one
antenna would see. MIMO signal processing is sophisticated enough to discern
multiple spatial streams (see Multiple Data Streams—Spatial Multiplexing). There
are no settings to configure for MIMO.
Multiple Data Streams—Spatial Multiplexing
Spatial Multiplexing transmits completely separate data streams on different
antennas (in the same channel) that are recombined to produce new 802.11n data
rates. Higher data rates are achieved by splitting the original data stream into
separate data streams. Each separate stream is transmitted on a different antenna
(using its own RF chain). MIMO signal processing at the receiver can detect and
recover each stream. Streams are then recombined, yielding higher data rates.
Frequency Across Subcarriers
Attenuation
Antenna 1 Signal
MIMO Processed Signal
Antenna 2 Signal
Antenna 3 Signal
Receiver