Browsing by Author "Lu, Ssu-Han"

Now showing 1 - 5 of 5

Antenna Clustering for Distributed Large-Scale MIMO Systems
(2014)
Lu, Ssu-Han
;
Chen, Yan-Gui
;
Wang, Li-Chun
;
交大名義發表
;
National Chiao Tung University
In addition to the advantage of high capacity in conventional multiple input multiple output (MIMO) systems, distributed large scale (DLS) MIMO systems can further enhance energy efficiency and the system performance at the cell edge. Key challenges in DLS-MIMO systems include interference mitigation and complex signal processing in a large number of antennas. Thus, the concept of antenna clustering is proposed to reduce the complexity of signal processing, but the inter-cluster interference still affect the system performance seriously. In this paper, we present a dynamic antennas clustering algorithm to overcome the inter-cluster interference, while reducing the complexity of signal processing. Simulation results show that our proposed antenna clustering algorithm can improve the spectrum efficiency of 80% for cell edge users and energy efficiency of 20% compared with the existing antenna clustering techniques.
Cooperative Hierarchical Cellular Systems in LTE-A Networks
(2015-09-01)
Lu, Ssu-Han
;
Wang, Li-Chun
;
Chiang, Tsung-Ting
;
Chou, Chen-Hsiao
;
交大名義發表
In this paper, we investigate the performance of hierarchical base station cooperation (HBSC) techniques in macrocell/microcell heterogeneous networks for the Third-Generation Partnership Project Long-Term Evolution-Advanced (LTE-A) system. HBSC techniques aim at reducing the cochannel interference between a macrocell and a group of microcells by coordinating the transmissions of distributed antennas in the cell coverage area. We find that joint intra-and intersite cooperation will significantly reduce the intercell interference. Compared with the case without joint intrasite/intersite cooperation, we demonstrate that HBSC in the conventional pentagonal cell architecture can improve spectrum efficiency by 65% at the cell edge. When the narrow-beam trisector cell architecture is considered, the spectrum efficiency can be further improved by 16.42% at the cell edge.
Non-linear Effects of Receiver Amplifier for 60GHz Radio Communication
(2011)
Ku, Meng-Lin
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Lu, Ssu-Han
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Wang, Li-Chun
;
Yan, Sheng-Hong
;
電機工程學系
In this paper, we investigate the impact of a receiver amplifier on orthogonal frequency division multiplexing (OFDM) and single-carrier block transmission (SCBT) systems which are two potential air interfaces for future short-range wireless communications at 60GHz radio spectrum. We derive a generalized baseband equivalent model for the receiver amplifier by using a power series to capture the nonlinear distortion behavior with several parameters. Based on this model, we develop a simulation flow in the baseband domain for evaluating the system performance deterioration with the non-ideal receiver amplifier. Computer simulations are used to compare the performance of OFDM and SCBT systems under several radio frequency (RF) parameters, such as 1dB compression point, the 3rd-order intercept point, etc. The developed methodology across the baseband and RF can help us jointly optimize the system performance and implementation cost with the nonlinear amplifier at the receiver side.
Optimal Beamforming and Scheduling for MIMO-OFDM Uplink Transmissions in Hierarchical Cognitive Radio Systems
(2013)
Lu, Ssu-Han
;
Chen, Yen-Ming
;
Wang, Li-Chun
;
交大名義發表
;
National Chiao Tung University
Cognitive radio (CR) technology can be been applied in hierarchical cellular systems to allow concurrent transmissions for licensed (primary) and unlicensed (secondary) users to improve spectrum utilization. The major challenge of hierarchical CR systems is to manage the inter-cell interference between the primary and secondary systems. In the paper, we first present an optimal multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) uplink transmission scheme for hierarchical CR systems that can maximize the sum rate of the underlay secondary CR users, and prevent the primary systems from the severe interference of the secondary systems. The main contribution of this work is to propose a methodology to transform the signal to interference plus noise ratio (SINR) maximization problem of the secondary system into a quasi-convex form, thereby obtaining the optimal beamforming solution using a simple bisection method. Furthermore, we proposed a sub-optimal user scheduling algorithm in the secondary system to effectively mitigate the interference to the primary system.
Time Domain Coordination for Inter-cell Interference Reduction in LTE Hierarchical Cellular Systems
(2014-01-01)
Lu, Ssu-Han
;
Lai, Wen-Pin
;
Wang, Li-Chun
;
交大名義發表
;
National Chiao Tung University
In this paper, we present an interference-aware slot allocation technique to improve system performance of the hierarchical picocell/macrocell system, where low-power picocells are underlying a high-power macrocell. Although a hierarchical picocell/macrocell system can improve capacity, it also poses a challenging inter-cell interference (ICI) issue. To control the ICI between pico-cells and macro-cells, one enhanced intercell interference coordination (eICIC) technique, called almost blank subframes (ABS), was proposed in the 3rd Generation Partnership Project (3GPP) Long-Term Evolution-Advanced (LTE-A) system. Nevertheless, the current ABS mechanism in 3GPP only defines the fixed ABS ratio, which is not very spectrum efficient and can affect the macrocellular system performance. In this paper, we propose an interference-aware ABS ratio adaptation technique to enhance the total spectrum efficiency of the hierarchical picocell/macrocell system. Compared with the current fixed ABS ratio approach, the proposed method can improve the spectral efficiency of pico-cells and macro-cells by 13% and 7% at the cell edge, respectively.