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Optimal linear precoding in multiuser MIMO systems: A large system analysis
 in Proceedings of Globecom 2014
, 2014
"... Abstract—We consider the downlink of a singlecell multiuser MIMO system in which the base station makes use of N antennas to communicate with K singleantenna user equipments (UEs) randomly positioned in the coverage area. In particular, we focus on the problem of designing the optimal linear prec ..."
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Abstract—We consider the downlink of a singlecell multiuser MIMO system in which the base station makes use of N antennas to communicate with K singleantenna user equipments (UEs) randomly positioned in the coverage area. In particular, we focus on the problem of designing the optimal linear precoding for minimizing the total power consumption while satisfying a set of target signaltointerferenceplusnoise ratios (SINRs). To gain insights into the structure of the optimal solution and reduce the computational complexity for its evaluation, we analyze the asymptotic regime where N and K grow large with a given ratio and make use of recent results from large system analysis to compute the asymptotic solution. Then, we concentrate on the asymptotically design of heuristic linear precoding techniques. Interestingly, it turns out that the regularized zeroforcing (RZF) precoder is equivalent to the optimal one when the ratio between the SINR requirement and the average channel attenuation is the same for all UEs. If this condition does not hold true but only the same SINR constraint is imposed for all UEs, then the RZF can be modified to still achieve optimality if statistical information of the UE positions is available at the BS. Numerical results are used to evaluate the performance gap in the finite system regime and to make comparisons among the precoding techniques. I.
1Large System Analysis of Base Station Cooperation for Power Minimization
"... IEEE Abstract—This work focuses on a largescale multicell multiuser MIMO system in which L base stations (BSs) of N antennas each communicate with K singleantenna user equipments. We consider the design of the linear precoder that minimizes the total power consumption while ensuring target user ..."
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IEEE Abstract—This work focuses on a largescale multicell multiuser MIMO system in which L base stations (BSs) of N antennas each communicate with K singleantenna user equipments. We consider the design of the linear precoder that minimizes the total power consumption while ensuring target user rates. Three configurations with different degrees of cooperation among BSs are considered: the coordinated beamforming scheme (only channel state information is shared among BSs), the coordinated multipoint MIMO processing technology or network MIMO (channel state and data cooperation), and a single cell beamforming scheme (only local channel state information is used for beamforming while channel state cooperation is needed for power allocation). The analysis is conducted assuming that N and K grow large with a non trivial ratio K/N and imperfect channel state information (modeled by the generic GaussMarkov formulation form) is available at the BSs. Tools of random matrix theory are used to compute, in explicit form, deterministic approximations for: (i) the parameters of the optimal precoder; (ii) the powers needed to ensure target rates; and (iii) the total transmit power. These results are instrumental to get further insight into the structure of the optimal precoders and also to reduce the implementation complexity in largescale networks. Numerical results are used to validate the asymptotic analysis in the finite system regime and to make comparisons among the different configurations. I.
Large System Analysis of Base Station Cooperation for Power Minimization
"... AbstractThis work focuses on a largescale multicell multiuser MIMO system in which L base stations (BSs) of N antennas each communicate with K singleantenna user equipments. We consider the design of the linear precoder that minimizes the total power consumption while ensuring target user rates ..."
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AbstractThis work focuses on a largescale multicell multiuser MIMO system in which L base stations (BSs) of N antennas each communicate with K singleantenna user equipments. We consider the design of the linear precoder that minimizes the total power consumption while ensuring target user rates. Three configurations with different degrees of cooperation among BSs are considered: the coordinated beamforming scheme (only channel state information is shared among BSs), the coordinated multipoint MIMO processing technology or network MIMO (channel state and data cooperation), and a single cell beamforming scheme (only local channel state information is used for beamforming while channel state cooperation is needed for power allocation). The analysis is conducted assuming that N and K grow large with a non trivial ratio K/N and imperfect channel state information (modeled by the generic GaussMarkov formulation form) is available at the BSs. Tools of random matrix theory are used to compute, in explicit form, deterministic approximations for: (i) the parameters of the optimal precoder; (ii) the powers needed to ensure target rates; and (iii) the total transmit power. These results are instrumental to get further insight into the structure of the optimal precoders and also to reduce the implementation complexity in largescale networks. Numerical results are used to validate the asymptotic analysis in the finite system regime and to make comparisons among the different configurations.
Analysis and Management of Interference in 5G Reverse TDD HetNets
"... Abstract—This work analyzes a heterogeneous network (HetNet), which comprises a macro base station (BS) equipped with a large number of antennas and an overlaid dense tier of small cell access points (SCAs) using a wireless backhaul for data traffic. The static and low mobility user equipments (UEs ..."
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Abstract—This work analyzes a heterogeneous network (HetNet), which comprises a macro base station (BS) equipped with a large number of antennas and an overlaid dense tier of small cell access points (SCAs) using a wireless backhaul for data traffic. The static and low mobility user equipments (UEs) are associated with the SCAs while those with mediumtohigh mobility are served by the macro BS. A reverse time division duplexing (TDD) protocol is used by the two tiers. We evaluate and characterize the performance of the system through the power consumption of uplink (UL) and downlink (DL) transmissions under the assumption that target rates must be satisfied and imperfect channel state information is available. The large system analysis is used to provide concise formulae for the asymptotic UL and DL transmit powers and precoding vectors under the above assumptions. Numerical results are used to validate the analysis in different settings and to make comparisons with alternative network architectures. I.