28,604 research outputs found
Cooperative Communications with Partial Channel State Information in Mobile Radio Systems
Future 4G mobile radio cellular networks are considered OFDM-MIMO systems. Cooperative communication based on coordinated base stations is a very promising concept to perform inter-cell interference management. This thesis deals with the concept of cooperative communication from its information-theoretic background to its practical system design. The main focus is a practical design of the joint detection scheme in the uplink and the joint transmission scheme in the downlink with partial channel-state information (CSI), i.e., significant CSI and imperfect CSI.Zukünftige zellulare 4G-Mobilfunksysteme können als OFDM-MIMO-Systeme betrachtet werden. In solchen zukünftigen Mobilfunksystemen ist kooperative Kommunikation, basierend auf koordinierten Basisstationen, ein sehr vielversprechendes Konzept zum Interzellinterferenzmanagement. Die vorliegende Arbeit behandelt das Konzept der kooperativen Kommunikation vom informationstheoretischen Hintergrund bis hin zum praktischen Systemdesign. Der Schwerpunkt der vorliegenden Arbeit liegt auf dem praktischen Design kooperativer Kommunikationssysteme mit partieller Kanalkenntnis
Uplink CoMP under a Constrained Backhaul and Imperfect Channel Knowledge
Coordinated Multi-Point (CoMP) is known to be a key technology for next
generation mobile communications systems, as it allows to overcome the burden
of inter-cell interference. Especially in the uplink, it is likely that
interference exploitation schemes will be used in the near future, as they can
be used with legacy terminals and require no or little changes in
standardization. Major drawbacks, however, are the extent of additional
backhaul infrastructure needed, and the sensitivity to imperfect channel
knowledge. This paper jointly addresses both issues in a new framework
incorporating a multitude of proposed theoretical uplink CoMP concepts, which
are then put into perspective with practical CoMP algorithms. This
comprehensive analysis provides new insight into the potential usage of uplink
CoMP in next generation wireless communications systems.Comment: Submitted to IEEE Transactions on Wireless Communications in February
201
Sum-Rate Maximization for Linearly Precoded Downlink Multiuser MISO Systems with Partial CSIT: A Rate-Splitting Approach
This paper considers the Sum-Rate (SR) maximization problem in downlink
MU-MISO systems under imperfect Channel State Information at the Transmitter
(CSIT). Contrary to existing works, we consider a rather unorthodox
transmission scheme. In particular, the message intended to one of the users is
split into two parts: a common part which can be recovered by all users, and a
private part recovered by the corresponding user. On the other hand, the rest
of users receive their information through private messages. This
Rate-Splitting (RS) approach was shown to boost the achievable Degrees of
Freedom (DoF) when CSIT errors decay with increased SNR. In this work, the RS
strategy is married with linear precoder design and optimization techniques to
achieve a maximized Ergodic SR (ESR) performance over the entire range of SNRs.
Precoders are designed based on partial CSIT knowledge by solving a stochastic
rate optimization problem using means of Sample Average Approximation (SAA)
coupled with the Weighted Minimum Mean Square Error (WMMSE) approach. Numerical
results show that in addition to the ESR gains, the benefits of RS also include
relaxed CSIT quality requirements and enhanced achievable rate regions compared
to conventional transmission with NoRS.Comment: accepted to IEEE Transactions on Communication
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