There is a rat race in wireless communication to
achieve higher spectral efficiency. One technique to achieve this
is the use of multiple antenna systems i.e. MIMO systems. In
this paper we describe a wireless 4x4 Multiple Input Multiple
Output (MIMO) testbed in the 2.2 GHz band including results
from live experiments. MIMO systems have several advantages
compared to SISO (Single Input Single Output) systems. The
most important ones are higher reliability and/or higher throughput
per Herz. In this testbed we used the 802.11a OFDM
Wireless LAN standard as a basis for the MIMO system. The
experiments have been conducted at 2.2 GHz carrier using 5
MHz bandwidth. These can be divided into several subjects:
antenna spacing experiments, effects for increasing antennas,
AD accuracy and performance for different antenna topologies.
Moreover, the performance of the Zero Forcing (ZF), Minimum
Mean Square Error (MMSE) and Vertical Bell labs LAyered
Space Time (VBLAST) have been evaluated