Multiuser MIMO with limited cooperation and channel state information
- Next generation wireless networks are targeting 1000x increase in capacity to meet the tremendous growth in data demand. As the number of wireless systems grows exponentially, the availability of prime wireless spectrum is becoming severely limited. Multiple-Input Multiple-Output (MIMO) technologies have emerged as a method to significantly increase spectral efficiency by creating independent spatial dimensions within a given frequency band. However, exploiting these spatial dimensions can entail significant overhead in channel estimation and user cooperation. This thesis investigates methods to make MIMO technology more effective by drastically reducing this overhead via two innovations: cognitive MIMO systems and noncoherent massive MIMO. In the first part of the thesis, we study cognitive MIMO systems that efficiently learn how to exploit empty spatial dimensions so as to avoid interfering with other systems in the same frequency band. We first consider a cognitive MIMO system where the transmitter of the first system learns the null space of the channel to the receiver of the other system by observing an affine function of the inflicted interference; a measurement that is already taking place in today's wireless networks. This measurement must either be broadcast or inferred by the power control mechanism of the interfered system. We analyze the effect of noisy measurements on the average worst-case interference reduction and show how this mechanism could be applicable in several wireless scenarios with limited cooperation across systems, including cognitive radio networks and cooperative base stations in cellular networks. In the second part of the thesis, we turn our attention to communication systems with a massive number of antennas (massive MIMO) and limited channel state information. In particular, we consider a single-shot system with single antenna transmitters and a single receiver with a large number of antennas, which only knows the large-scale fading statistics. The suggested system modulates information on the power of the symbols, and uses a receiver that decodes based only on the average energy across the antennas. We provide an optimal constellation design in terms of the achievable error exponent in the number of receiver antennas when the channel fading distribution is known. Furthermore, we provide asymptotically optimal designs with increasing constellation size for the case of perfect or imperfect knowledge of the first few moments of the channel fading distribution. We present numerical and analytical comparative results with other transmission schemes in typical scenarios and show specific examples where each design should be employed.
|Type of resource
|electronic; electronic resource; remote
|1 online resource.
|Stanford University, Department of Electrical Engineering.
|Goldsmith, Andrea, 1964-
|Goldsmith, Andrea, 1964-
|Statement of responsibility
|Submitted to the Department of Electrical Engineering.
|Thesis (Ph.D.)--Stanford University, 2015.
- © 2015 by Alexandros Manolakos
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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