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5 - CoMP Schemes Based on Interf.-Aware Transceivers or Interf. Coord.
- from Part II - Practical CoMP Schemes
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- By Lars Thiele, Institute, Berlin, Thomas Wirth, Institute, Berlin, Malte Schellmann, European Research Center, Thomas Haustein, Institute, Berlin, Volker Jungnickel, Institute, Berlin
- Edited by Patrick Marsch, Gerhard P. Fettweis, Technische Universität, Dresden
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- Book:
- Coordinated Multi-Point in Mobile Communications
- Published online:
- 05 August 2012
- Print publication:
- 21 July 2011, pp 41-80
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- Chapter
- Export citation
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Summary
In this chapter, we introduce CoMP schemes where no or little information is exchanged between cooperating base stations. In Section 5.1, we observe an interference-aware downlink transmission scheme where each base station performs individual intra-cell beamforming, while the terminals are able to mitigate inter-cell interference to a certain extent through a particular interference estimation and rejection concept. The level of base station cooperation is then increased in Sections 5.2 and 5.3, where joint multi-cell scheduling and link adaptation, and multi-cell coordinated beamforming are investigated, respectively.
Downlink Multi-User Beamforming with Interference Rejection Combining
In this section, we evaluate a non-cooperative downlink transmission scheme, i.e. where no explicit cooperation takes place between base stations (BSs), but where interference-aware transmission and reception is performed within cells. The BSs perform intra-cell precoding based on limited feedback from the user equipments (UEs), in conjunction with interference-aware scheduling and interference rejection combining (IRC) at the terminal side. This section is based on “Interference-aware scheduling in the synchronous cellular multi-antenna downlink”, by L. Thiele, M. Schellmann, T. Wirth and V. Jungnickel, which appeared in [TSWJ09]. © 2009 IEEE.
Introduction
Transmission with multiple antennas both at the transmitting and receiving ends of a wireless link has become increasingly mature in recent years. From theory, the fundamental capacity gain of the multiple-input multiple-output (MIMO) radio link, being proportional to the minimum of the number of transmit and receive antennas, is well understood for an isolated point-to-point link.
9 - Channel Knowledge
- from Part III - Challenges Connected to CoMP
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- By Wolfgang Zirwas, Munich, Germany, Lars Thiele, Fraunhofer Institute for Telecommunications, Tobias Weber, University of Rostock, Nico Palleit, University of Rostock, Volker Jungnickel, Institute, Berlin
- Edited by Patrick Marsch, Gerhard P. Fettweis, Technische Universität, Dresden
-
- Book:
- Coordinated Multi-Point in Mobile Communications
- Published online:
- 05 August 2012
- Print publication:
- 21 July 2011, pp 193-218
-
- Chapter
- Export citation
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Summary
In this chapter, we address the issue how channel knowledge - referring to both desired channels and the channels towards interferers - needed for various CoMP schemes can be made available where it is needed. We first investigate channel estimation techniques at the receiver side in Section 9.1, and then discuss how the obtained channel knowledge can be efficiently fed back to the transmitter side in Section 9.2, which is for example a crucial requirement for the downlink CoMP schemes investigated in Sections 6.3 and 6.4. The chapter shows that standard channel estimation and feedback concepts can principally be extended to enable CoMP in general. However, it also becomes apparent that large CoMP cooperation sizes may be considered questionable in practice, due to the fact that weak links cannot be estimated accurately, and the involved pilot and channel state information (CSI) feedback overhead may become prohibitive.
Channel Estimation for CoMP
One of the main challenges for CoMP schemes like joint transmission (JT) is to obtain accurate channel information in a multi-cell mobile radio environment with acceptable overhead for pilot signals.
The section is structured as follows. In Subsection 9.1.1, main characteristics of the mobile radio channel and state-of-the-art estimation and interpolation techniques like Wiener filtering will be introduced, with a special focus on channel prediction. For CoMP, the analysis then has to be extended to multiple channel components and multi-cell scenarios, which will be done in Subsections 9.1.2 and 9.1.3, respectively.
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