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Multiuser (MU) - multiple input multiple output (MIMO) techniques are attractive to increase the downlink spectrum efficiency since they allow a small number of antennas at each user station (STA). In MU-MIMO systems, the transmission performance is affected by the STA combination that is spatially multiplexed in the same frequency and same time slot. Thus, the AP needs to determine the optimum STA...
TDD multiuser downlink MIMO channels with delayed channel state information at the transmitter (CSIT) are considered. Block diagonalization is applied at the base station (BS). In order to cope with the inter-user interference caused by the delayed CSIT, we develop a novel capacity estimation method at first and then propose robust delayed CSIT aware multimode selection schemes based on the estimation...
Block Diagonalization (BD) algorithm is a generalization of channel inversion scheme in multiuser multi-input multi-output (MIMO) broadcast channels. Although the BD algorithm is effective in removing interuser interference, it has a drawback that additional information should be delivered to the receiver. Recent work on BD with vector perturbation (VP) avoids the need for additional information and...
In this paper, we present a high-performance hybrid linear precoding scheme for the downlink of multiuser multiple-input multiple-output (MU-MIMO) systems based on the combination of an iterative modified regularized block diagonalization (IMRBD) precoding and minimum mean square error (MMSE) precoding. The proposed hybrid diversity maximization (HDM) scheme aims to maximize the diversity gain by...
Opportunistic beamforming is a promising technique for downlink channels in cellular systems. When opportunistic beamforming is to support multiple users at a time, beams should be formed to avoid interference and this requires the feedback of channel state information (CSI) from users to a base station (BS). With limited feedback, to minimize the impact of interference, the best beamforming matrix...
We solve the rate balancing problem in the downlink for a multiuser multiple-input-multiple-output (MIMO) system with multiple linear transmit covariance constraints. In particular, we adopt a linear transceiver structure to maximize the worst-case rate of the user while satisfying multiple linear transmit covariance constraints. The original rate balancing problem in the downlink is more complicated...
This paper considers the joint precoder design problem for multiple-input single-output (MISO) systems with coordinated base stations (BSs). We consider maximization of the total sum rate with per BS antenna power constraint problem. For this problem, we propose a novel linear iterative algorithm. The problem is solved as follows. First, by introducing additional optimization variables and applying...
In this paper, we propose a new downlink multi-user multiple-input multiple-output (MIMO) precoding scheme based on maximizing the successive signal to leakage plus noise ratio (SSLNR). The work is motivated by the precoding scheme developed by Sadek, Tarighat and Sayed by maximizing the signal to leakage plus noise ratio (SLNR), which does not impose any restriction on the number of antennas at the...
In this paper, we develop linear precoding methods for cognitive radio (CR) multi-user multiple-input multiple-output (MU-MIMO) broadcast systems where unlicensed secondary users (SUs) simultaneously use the same spectrum of the licensed primary user (PU). When the zero-forcing block diagonalization (ZF-BD) precoder is extended to the CR network, a noise enhancement problem occurs. Therefore, we propose...
Inter-cell interference coming from multiple base stations (BS) in adjacent cells limits the capacity of wireless cellular networks. In this paper, we exploit the uplink-downlink duality principle and BS cooperation to design linear and nonlinear downlink inter-cell interference management techniques for multi-user multiple-input-multiple-output (MIMO) systems. The proposed linear algorithm can effectively...
Multi-cell cooperative transmission is attracting much attention. This technology improves the cell-edge throughput since multiple base stations cooperate with each other in transmitting signals to the cell-edge user. One basic implementation of multi-cell cooperative transmission is inter-sector cooperation, in which a base station with three sectors uses its own equipment to realize multi-cell cooperative...
In this paper we analyse the downlink performance of a rank adaptive multiple input multiple output (MIMO) system in a busty traffic cellular network. A LTE-Advanced system with multiple component carriers was selected as a study case. To highlight the advantage of using MIMO techniques, we used a single input multiple output (SIMO) system as a baseline for performance comparison. The gain mechanisms...
Optimum capacity scaling in the downlink of a single-cell multiple-input-multiple-output communication system can be achieved by a communication strategy called opportunistic beamforming in which information carrying beams are randomly formed and users are opportunistically scheduled based on their partial channel state information. Even though opportunistic beamforming reduces the amount of feedback...
An adaptive subband chip-equalizer is investigated for downlink multiple-input multiple-output (MIMO) direct-sequence (DS) ultra-wideband (UWB) systems to cope with the inter-symbol interference (ISI) and the multiple-access interference (MAI) in multipath fading channels. The subband decomposition technique is employed to improve substantially the downlink reception of mobile-terminal receivers without...
Typical formulations of max-min weighted SIR problems involve either a total power constraint or individual power constraints. These formulations are unable to handle the complexities in multicell networks where each base station can be subject to its own sum power constraint. This paper considers the max-min weighted SIR problem subject to multiple weighted-sum power constraints, where the weights...
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