Book: Wireless Communications over MIMO Channels: Applications to CDMA and Multiple Antenna Systems
Publisher: John Wiley & Sons
Mobile radio communications are evolving from pure telephony systems to multimediaplatforms offering a variety of services ranging from simple file transfers and audio andvideo streaming, to interactive applications and positioning tasks. Naturally, these serviceshave different constraints concerning data rate, delay, and reliability (quality-of-service(QoS)). Hence, future mobile radio systems have to provide a large flexibility and scalabilityto match these heterogeneous requirements. Additionally, bandwidth has becomean extremely valuable resource emphasizing the need for transmission schemes with highspectral efficiency. To cope with these challenges, three key areas have been the focus ofresearch in the last decade and are addressed in this book: Code division multiple access(CDMA), multiple antenna systems, and strong error control coding.CDMA was chosen as a multiple access scheme in third generation mobile radio systemssuch as the universal mobile telecommunication system (UMTS) and CDMA 2000.The main ingredient of CDMA systems is the inherent spectral spreading that allows acertain coexistence with narrow band systems. Owing to the large bandwidth, it generallyprovides a higher diversity degree and thus a better link reliability. Compared to secondgeneration mobile radio systems, the third generation offers increased flexibility like differentand much higher data rates as required for the large variety of services. The frequencyreuse factor in such cellular networks allows neighboring cells to operate at the same frequency,leading to a more efficient use of the resource frequency. Moreover, this allowssimpler soft handover compared to the ‘break before make’ strategy in global system formobile communication (GSM) when mobile subscribers change the serving cell. The maindrawback of CDMA systems is the multiuser interference requiring appropriate detectionalgorithms at the receiver.Multiple antenna systems represent the second major research area. Owing to their highpotential in improving the system efficiency they have already found their way into severalstandards. On one hand, multiple antennas at the receiver and transmitter allow the transmissionof several spatially separated data streams. For point-to-point communications, thisis termed space division multiplexing (SDM), and in multiuser scenarios, it is called spacedivision multiple access (SDMA). In both the scenarios, the system’s spectral efficiencycan be remarkably increased compared to the single antenna case. On the other hand, thelink reliability can be improved by beamforming and diverse techniques.