TABLE OF CONTENTS The IEEE 802.11n draft standard (scheduled to be ratified in 2008) uses advanced Multiple Input Multiple Output (MIMO) radio techniques, using two or more simultaneously active antennas combined with two or more transmitter and receiver channels. MIMO promises to provide order-of-magnitude increases in physical (PHY) data rates along with increased resistance to interference and greater effective range (distance between the transmitter and receiver). However, these techniques are particularly difficult to test, as they are both complex and highly sensitive to the RF environment in which they are deployed. This chapter covers some of the special needs and approaches for testing MIMO devices and systems.
Note that as much of this technology is just being developed, and the whole area of MIMO in wireless LANs (WLANs) is still very much in its infancy, many of the test techniques and approaches are still under research and development. This chapter should, however, arm the prospective test engineer with enough background to get a start on the MIMO testing process. Before diving into test techniques, however, we will take a reasonably detailed look at what MIMO is and how it works.
MIMO is the term given to a technique whereby multiple antennas, transmitters, and receivers are exploited in an RF multipath environment (see Chapter 3) to provide a radio link with increased information capacity, improved interference suppression, greater range, and higher fading resistance. The term "MIMO" encompasses a number of different techniques, ranging from relatively simple smart antenna systems...
