Inhalt des Dokuments
nat. Volker Jungnickel|
|Mittwoch, 11. Februar 2015, 10.00 Uhr,
Fraunhofer-Institut für Nachrichtentechnik, Heinrich-Hertz-Institut,
HHI, Hörsaal 009|
The objective of this lecture is to provide an introduction into the capacity limits of multi-antenna systems. The focus is on understanding the channel in real environments and to highlight implications for wireless system design. Students should have general knowledge about mobile communications and be familiar with basic multi-antenna formulas.
In the first part, the MIMO channel model is repeated using vectors for transmitted and received signals and a matrix including the channels between each transmitter and receiver. Next, models for ideal MIMO channels are introduced. Singular-value decomposition (SVD) is used as a main tool to characterize the MIMO channel and the statistics of singular values is discussed for selected channels.
In the second part, the MIMO capacity formula is used. Computation can be simplified using SVD. For specific channels, upper and lower bounds are derived.
The capacity statistics in random MIMO channels is then illustrated. Because capacity is a statistical quantity in a mobile scenario, the terms instantaneous, mean and outage capacity are introduced. Capacity scaling is discussed as a function of the number of antennas. As the channel can change in a mobile scenario, link adaptation is very useful in practice, instead of using a fixed data format, to operate the link safely in any channel condition.