The why and how of multiantenna systems

Bandwidth efficiency is of great importance for modern wireless communication systems. Increase of bandwidth efficiency normally sacrifices power efficiency, which is also important. Multiantenna systems offer the potential to improve both at the expense of utilizing multiple antennas preferably at both ends of a transmission link. We are reviewing generic performance measures for such systems in single link scenarios based on long term (LT) channel state information at the transmitter (TCSI). Extending the considerations to multiuser single cell scenarios, instantaneous TCSI will be necessary to fully exploit what multiple antennas can offer. Here we consider the problem of how to partition resources optimally to accommodate feedback of CSI from receiver to transmitter. Further extension to cellular multiuser multiantenna systems confronts us with the problem of intercell interference (ICI) which due to scheduling is a nonstationary random process. There is a huge improvement in cell sum rate to be gained, if we can make the ICI power predictable. We focus only on reviewing generic results telling us what can be achieved with multiple antennas but will not go into detailed realizations thereof.