13-05-2013, 04:47 PM
Multiple-Input-Multiple- Output (MIMO) Systems
Multiple-Input-Multiple.ppt (Size: 482.5 KB / Downloads: 232)
Aspirations
High data rate wireless communications links with transmission rates nearing 1 Gigabit/second (will quantify a “bit” shortly)
Provide high speed links that still offer good Quality of Service (QoS) (will be quantified mathematically)
Antenna Configurations
Theoretically, the 1Gbps barrier can be achieved using this configuration if you are allowed to use much power and as much BW as you so please!
Extensive research has been done on SISO under power and BW constraints. A combination a smart modulation, coding and multiplexing techniques have yielded good results but far from the 1Gbps barrier
Data Units
Will use the following terms loosely and
interchangeably,
Bits (lowest level): +1 and -1
Symbols (intermediate): A group of bits
Packets (highest level): Lots and lots of
symbols
Diversity
Each pair of transmit-receive antennas provides a signal path from transmitter to receiver. By sending the SAME information through different paths, multiple independently-faded replicas of the data symbol can be obtained at the receiver end. Hence, more reliable reception is achieved
A diversity gain d implies that in the high SNR region, my Pe decays at a rate of 1/SNRd as opposed to 1/SNR for a SISO system
The maximal diversity gain dmax is the total number of independent signal paths that exist between the transmitter and receiver
For an (MR,MT) system, the total number of signal paths is MRMT