802.11n MIMO-OFDM Standard  IEEE n group  MIMO-OFDM  Increased performance  Transmitter  MAC Enhancements  Results

IEEE n  Goal was to give a throughput of at least 100 Mbps at the MAC data service access point  Needed to support existing g  Draft was created July defines data rates in 20 and 40 MHz channels-Use of 2 spatial streams with a short guard in the 40 MHz channel provides the highest possible data rate for 300 Mbps which can be increased with Modulation and Coding Schemes (MCS) in 3 and 4 spatial streams Task group was formed in July 2003

MIMO-OFDM  Increases link capacity by simultaneously transmitting multiple data streams  Uses multiple transmit and receive antennas  Able to reach data rates several times larger than current rates of g  Does not need a larger bandwidth to reach increased data rates Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing

b11Mbps g54Mbps n300Mbps Greatly increases speed over existing technologies

802.11n Transmitter –Input data is first scrambled using length-127 pseudo-noise scrambler –Same as existing technology in a –Differs for 3 and 4 spatial streams with the odds and even bits being separately encoded by two different encoders –Interleaves bits across both spatial steams so it benefits from spatial diversity and frequency diversity –Bits are then mapped to QAM symbols and a spatial stream dependent cyclic delay is applied –Mask is tighter so that the extra tones don't decrease performance in adjacent channels

MAC Enhancements  Used to help increase the net throughput with the newly defined high data rates  Aggregation- makes the packets as large as possible so that the the overhead is minimized  Reduced Inter Frame Spacing (RIFS)- allows for transmitting bursts of packets with only 2 microseconds of separation

Results of performance gains –Using MIMO-OFDM with only 2 streams is easily implemented and will increase throughput over 100 Mbps –Offers increased ranged which is about 3 times larger compared to conventional wireless LANs –Would allow for wireless video distribution and high quality streams. –Will become more useful with phones and wireless devices streaming data