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The 5th generation of mobile communications system (5G) is nowadays expected to support very diverse applications, devices, and services such as enhanced mobile broadband (eMBB) and the Internet of things (IoTs). In order to meet the future requirements, new 5G candidate radio access technologies have been proposed and studied. For example, Massive multiple-input multiple-output (MIMO) is an attractive...
We propose a novel transmission scheme based on Tomlinson-Harashima precoding (THP) that serves as a practical downlink multi-user (MU) MIMO transmission scheme for future radio access networks. The transmission of reference signals (RSs) is an issue of THP because the modulo operation during the interference cancellation introduces ambiguities to the channel estimation if it is applied on RSs. Without...
Higher spectrum efficiency is a target of the 5th generation (5G) mobile communications system. Massive MIMO is considered as one of important technologies for that purpose. Under the practical conditions that the number of antennas on user equipment (UE) is limited, multi-user MIMO (MU-MIMO) is a probable use scenario of Massive MIMO. Furthermore, massive connectivity is another important target,...
To meet the challenging capacity requirement of 5G, a set of radio access technologies may be needed, including technologies to improve the spectrum efficiency, to utilize more available spectrum, and network densification, etc. In this paper, we focus on how to combine massive multiple-input and multiple-output (MIMO) and dense small cell (DSC) deployment to boost the system capacity. Under the framework...
This paper investigates channel state information (CSI) acquisition schemes for LTE-Advanced based 3D MIMO systems. Three different CSI acquisition schemes are introduced and compared with a system-level simulation. Simulation results for the 3D-UMi scenario show that the proposed scheme, i.e., stepwise CSI acquisition scheme based on beamformed CSI-reference signal (RS), achieves either similar or...
Massive MIMO is envisioned as one of the key technologies for the 5th generation (5G) wireless communication systems. Hybrid beamforming is a promising and feasible solution to massive MIMO due to the achievable balance between performance and implementation cost, especially for the high frequency band. Different from user data channels and signals, common channels and signals cannot benefit from...
Massive MIMO is one of the promising technologies to be employed in the next generation mobile communication systems. Multi-user transmission is the nature of massive MIMO due to the high order of degree of freedoms and large beamforming gain provided by the large scale antenna arrays mounted at the base station side. Considering this nature and the characteristics of massive MIMO channels, we propose...
As the 3GPP long term evolution (LTE) system actively evolves, advanced multi-user multiple-input multiple-output (MU-MIMO) schemes have attracted increasing interest in the engineering field. We have proposed a QR decomposition (QRD) based MU-MIMO scheme for the evolving LTE time division duplex (TDD) system to achieve high spectrum efficiency, assuming ideal channel reciprocity. In order to investigate...
With the active evolvement of 3GPP long term evolution (LTE) system, advanced multi-user multiple-input multiple-output (MU-MIMO) transmission schemes attract more and more interests in engineering field. However, in order to bring advanced MU-MIMO techniques from theory to practice, there are two major obstacles to overcome, i.e., how to obtain accurate channel state information at the transmitter...
Multiple-input multiple-output (MIMO) spatial multiplexing has been adopted by 3GPP long term evolution (LTE) to increase the peak spectrum efficiency. However, it will lose its effectiveness for cell edge users due to the inter-cell interference (ICI). Therefore, 3GPP LTE-Advanced (LTE-A) is considering to introduce some multi-cell cooperative transmission techniques to solve this problem. In this...
In 3GPP long term evolution (LTE) uplink, single transmit antenna is adopted due to its simplicity and acceptable performance. However, in order to satisfy the higher requirement of LTE-Advanced (LTE-A) on uplink spectrum efficiency, multiple transmit antennas must be supported in LTE-A uplink. At the same time, the backwards compatibility to LTE should be taken into considerations. Therefore, the...
During the past decade, multiple-input-multiple-output (MIMO) systems have received a significant attention because of its promising capacity increase over single-input-single-output (SISO) systems. In this paper, as a key technology, we present a novel M-paths MIMO detection algorithm with dynamic-layer-ordering for spatial-multiplexing MIMO systems over rich scattering wireless environment. This...
This paper proposes a novel preamble structure and a timing synchronization method for OFDM systems. The preamble structure has both properties of delayed and symmetric correlations which can afford accurate time and frequency synchronization simultaneously. A new timing metric is also proposed according to the preamble structure, which is the production of the modulus of delayed and symmetric correlation...
Multiple-input multiple- output (MIMO) and orthogonal frequency division multiplexing (OFDM) are two key techniques for broadband wireless mobile communications. In order to provide accurate channel state information (CSI) to support MIMO-OFDM transmission in doubly-selective fading channels, we propose the robust channel estimator based on two-dimensional enhanced discrete-time Fourier transform...
Channel state information (CSI) is critical for the performance of orthogonal frequency division multiplexing (OFDM) systems. In this paper, we propose time-domain minimum mean square error (MMSE) channel estimation based on subspace tracking for OFDM systems, which can increase the channel estimation accuracy as well as lower the computational complexity. Furthermore, it requires little prior channel...
This paper describes a channel estimation scheme which utilizes interlaced transmit pilots to estimate multiple input multiple output (MIMO) channel responses in orthogonal frequency division multiplexing (OFDM) systems. This least square (LS) based channel estimation scheme adopts discrete Fourier transform (DFT) to improve the estimation accuracy. The constraint condition of the estimation scheme...
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