In recent years, with an ever increasing number of wireless services to be allocated within a limited frequency resource, much research has focused on the development of spectrally efficient transmission technologies at the physical layer. The most promising among these technologies is that of MIMO systems, which prescribe radio links with multiple antennas at both ends. A critical factor in determining the performance of a MIMO system is the availability of some information about the propagation channel (Channel State Information, CSI) at the receiver and, possibly, at the transmitter. This...

Multiple antenna solutions for wireless
communications are widely acknowledged as an effective
technology (in conjunction with channel coding) to increase
the link throughput as they are known to provide spatial
redundancy (or diversity order) that scales with the number
of antennas deployed. Since hardware, size and cost
constraints limit the number of antennas that can be
deployed, virtual multiple antenna links can be created by
coordinating multiple nodes with (typically) single antenna
...

Future wireless ad-hoc systems are expected to extensively rely on cooperation between terminals. On this line, cooperative retransmission protocols are particularly promising due to their opportunistic and flexible exploitation of both spatial and time diversity. In this book, some of the major issues that hinder the practical implementation of this technology are identified and pertaining solutions are proposed and analyzed. Firstly, cooperative retransmission protocols are reexamined in terms of energy efficiency and their limitation for short transmission ranges is observed. An...