MIMO Multiple Access Channels with Partial Channel State Information
Aubry, Augusto (2010) MIMO Multiple Access Channels with Partial Channel State Information. [Tesi di dottorato] (Inedito)
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The increasing demand for wireless communication systems has been the starting point for many research activities and discussions about the best way to make a cleaver usage of the available spectrum and the available power, in order to satisfy the requirements of the users. In these systems there are several issues which have to be taken in to account for the evaluation of their Shannon-Capacity, i.e. the maximum amount of information that can be reliably delivered: the mobility of the users, the presence of time varying obstacles, power and bandwidth limitations. A lot of efforts have been conducted for the Information-Theoretic characterization of wireless communication systems with the assumption of perfect channel state information (CSI) at the receiver side. In this Thesis an Information-Theoretic analysis of a Gaussian multiple-input multiple-output multiple access channel (MIMO MAC), with partial channel knowledge at the receiver, is provided. In particular an inner and an outer bound for the rate region of a MIMO MAC with partial CSI when the inputs are Gaussian, are derived. Moreover, the behavior of the gaps between the upper and lower bounds of the mutual information terms, which define the achievable rate region, is analyzed as function of: i) the number of the users, ii) the number of the receiving antennas, and iii) the signal to noise ratio. The problem of finding the precodings that attempt to maximize the lower bound to the sum-rate is also considered. Furthermore, the low-SNR and high-SNR regime for a MIMO MAC with partial CSI at the receiver are described. For the former, the attention is focused on the minimum energy per bit and on the multiaccess slope region, while for the latter on the high-SNR slope. The aforementioned framework turns out to be useful to describe the performance limits of two relevant scenarios of MAC systems in which only a partial CSI can be used at the receiver: Cooperative MIMO Networks and Training Based Systems. The performed analysis shows that the rates achievable over a MIMO MAC channel with partial CSI at the receiver side can be interpreted in terms of a coherent MIMO MAC channel with an increased noise level.
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