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We develop a novel opportunistic beamforming scheme referred to as doubly opportunistic beamforming (DOBF), which is doubly selective in both users and beams based on a new type of channel state information (CSI) feedback to improve the limited feedback downlink system performance. DOBF benefits from very flexible scheduling at the transmitter, compared to the conventional opportunistic beamforming...
The K/2 degrees of freedom (DoF) of the K-user Gaussian interference channel (GIC) are well known to be achievable for almost all constant real channel coefficients. In this paper, we investigate the sum-rate behavior of the K-user GIC at finite SNR. To this end, we derive closed-form upper bounds on the sum capacity for the symmetric real and semi- symmetric complex cases. We further show how large...
This letter investigates how user grouping, more specifically group partitioning, affects the sum-rate performance of a two-stage multiuser MIMO precoding scheme referred to as joint spatial division and multiplexing (JSDM). Taking a clustered user geometry model into account, we propose a new criterion for user grouping to noticeably improve the sum-rate performance of JSDM. Numerical results confirm...
In the LTE-advanced system, cell edge user equipments (UEs) are affected by interference signals transmitted from other cells. For this reason, an inter cell interference coordination (ICIC) technique is required. The goal of ICIC is to improve cell coverage and increase cell edge throughput. In this paper, through a system level simulation, we show the user throughput of each multiple-input multiple-output...
The interaction of nitrogen with Si(111)-7x7 surfaces at elevated temperatures ranging from 600 to 900 o C was investigated by using a scanning tunneling microscope (STM). Silicon nitride islands in a nanometer scale were formed upon nitrogen exposure at temperatures above 700 o C. In the initial stage of nitridation, those islands were formed preferentially at the step edges and then...
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