MIMO and Related Diversity Techniques Improve Wireless Range and Reliability

Multiple Input/Multiple Output (MIMO) tech-niques, as well as related diversity and “smart antenna” systems, are getting ready to make a significant impact on wireless technology. Although true MIMO is only deployed in the latest WLAN hardware, it is expected to be used widely in broadband networks, with deployments expected to begin in mid to late 2008. The impetus for the development of MIMO is simple—higher data rate for a given amount of radio spectrum, compared to single channel, single antenna systems. Under practical conditions, MIMO will provide an improvement in data rate approaching the total number of antennas at either end. For example, with two anten- nas at the transmitter, there are two distinct data chan-nels being sent. Ideally, two channels can carry twice the data of a single channel. If the receiver can accurately dis- tinguish between the two channels, the net capacity can approach that doubled rate. With four channels, the rate can approach quadruple that of a single channel.