ta traffic than today's most advanced 3.5G networks (which are discussed in Chapter 14). MIMO enables a network to quickly deliver multimedia content. For example, MIMO enables a 1MB picture to be downloaded in a second and a 60MB video to be downloaded in a minute. MIMO creates multiple parallel data streams between the multiple transmit and receive antennas. MIMO exploits phenomena such as multipath propagation to increase throughput, or reduce bit error rates, rather than attempting to elimi- nate the effects of multipath. It uses the multipath phenomenon to differentiate the separate signal paths from each MIMO antenna. (Telephony Online's article "Building Future Networks with MIMO and OFDM," at http://telephonyonline. com/wireless/technology/mimo_ofdm_091905/, provides a good graphic of MIMO antennas.) MIMO is a key technology associated with most of the advanced and emerg- ing wireless systems, including 3.5G and 4G. MIMO will also be used by IEEE 302.11n, the high-throughput 100Mbps WLAN standard expected to be finalized in 2007. By employing MIMO, 802.11n will offer up to eight times the coverage and up to six times the speed of current 802.11g networks. MIMO has also recently been added to the latest draft version of Mobile WiMax, described in IEEE 802.16e. A conventional radio has one input, a transmit antenna, and one output, a receive antenna. A MIMO system uses at least two transmit antennas, working simultaneously in the service of a single logical channel, and at least two receive antennas at the other end of the intended connection. In reality, the number of receive antennas in a MIMO system is usually greater than the number of transmit antennas, and performance generally improves with the addition of more receive antennas. A MIMO system uses its multiple antennas to simultaneously transmit data to the receivers in small pieces, and the receivers then process the data flows and put them back together. This process, called spatial multiplexing, proportion- ally boosts the data transmission speed 