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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...
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...
Non-orthogonal multiple access (NOMA) utilizing transmit power difference and advanced successive interference canceller (SIC) receivers has been considered as a candidate radio access technology for future wireless communication systems. Single-user multiple-input multiple-output (SU-MIMO) is one of the key technologies in Long-Term-Evolution (LTE) systems. Thus, it has been proved to combine with...
Non-orthogonal multiple access (NOMA) utilizing power domain and advanced receiver has been considered as a very promising candidate radio access technology for future wireless communication systems. Hybrid automatic repeat request (HARQ), as an indispensable part of link adaptation, plays a very important role in reliable high speed packet data service through exploiting retransmission diversity...
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...
The paradigm shift toward smartphones caused distinct traffic expansion in mobile networks. Indeed, the total amount of traffic in Japan is glowing nearly 1.8-fold in yearly basis during the past few years. To cope with this problem, many mobile operators are now speeding up their deployment of LTE/LTE-A. In this paper, current situation of LTE deployment in Japan, including area deployment and spectrum...
This paper proposes an adaptive non-linear distortion noise control method for low-priority systems under spectrum sharing environments. The proposed method adaptively controls distortion noise power of a transmitter to improve reception quality of shared bands with transmission power control. The distortion power is reduced to meet a required transmission quality. In this paper, the spectrum property...
In this study, we investigate the potential of cognitive radio systems (CRSs) with the aim of using the white space (WS) in Public Cellular Networks (PCNs). We first clarify the difficulties specific to PCN WS usage and propose a CRS technique with Cognitive-radio Supportive Accommodation System (CSAS) as a scheme to overcome the difficulties. The main concept of the scheme is that CSAS, which is...
This paper proposes a non-linear distortion noise control method for secondary systems in spectrum sharing. The proposed method is based on conventional clipping and filtering methods, and adaptively shapes distortion noise power to improve reception quality of secondary users with transmission power control. In this paper, optimal clipping levels to control in-band distortion noise are investigated,...
In this paper, we propose a system level simulation method based on the full 3-dimensional area model, for heterogeneous networks wherein an Urban Macrocellular System (UMa) and Indoor Hotspot Systems (InH) share the same frequency band. To enable more realistic performance evaluations with moderate computational complexity, our method selects statistical propagation models appropriate to each pair...
A theoretical analysis of the capacity achievable by an open-access cognitive radio system is provided, when the system uses spectrum allocated to a macro cellular system. The analysis is based on [7], where a theoretical analysis of the achievable capacity by a closed-access cognitive radio system is given and, in addition, considers the condition in which all mobile stations close to a cognitive...
An efficient multipath-based user selection (MPUS) algorithm for multiuser beamforming in multiple-input multiple-output (MIMO) distributed antenna systems (DAS) is presented in this paper. Motivated by the idea behind the M algorithm of MIMO detection, in this paper, we generate a scheduling tree having M nodes. From each of the M retained nodes, the M "best" users having the largest branch...
This paper proposes a multi-layer mushroom reflectarray to achieve a wide angle of reflection (AOR) reflectarray at a super high frequency that can be used to improve the Multiple-In-Multiple-Out capacity in a line-of-sight environment. The paper also presents a detailed design chart to satisfy the desired AOR by applying LC resonant circuit theory. A 70 degree-AOR reflectarray at 11 GHz is designed...
Multi-layer mushroom reflectarray with parasitic layers can control capacitance value theoretically using parasitic layers number. This paper studies the frequency characteristics of the Multi-layer mushroom reflectarray with parasitic patches using LC resonant circuit theory. To use the reflectarray for propagation improvement, this paper investigate reflection angle for oblique incidence using reflectarray...
CA(Carrier aggregation) is one of the most important techniques for LTE-Advanced system because of its capability to support wide bandwidth while achieving backward compatibility. In order to improve performance of control information transmission, cross-carrier scheduling is to be supported, i.e. control information on one CC (Component Carrier) can assign radio resource on another CC. Design of...
An important and widely used detection technique is cyclostationarity-based feature detection because the method does not require prior information such as the signal bandwidth or frame format, and time and frequency synchronization are likewise not required. The problem with conventional cyclostationarity-based feature detection is that the detection probability of weak signals degrades if multiple...
Dynamic frequency management is considered to be beneficial for the uncoordinated self-deployment of Home eNB (HeNB) in LTE-A heterogeneous networks. In this paper, a new autonomous component carrier (CC) selection scheme is proposed that dynamically selects the CC with efficient inter-cell signaling design. The CC selection criterion is to minimize the interference contribution composed of the incoming...
CA (Carrier aggregation) is one of the most important techniques for LTE-Advanced system because of its capability to support wide bandwidth while achieving backward compatibility. This paper focuses on enhancements of downlink control channel resource allocation for CA system in order to improve the performance of control information transmission in cross-carrier scheduling. A novel metric, named...
This paper investigates the downlink system level performance for Layer-3 (L3) and Layer-1 (L1) relays with orthogonal frequency division multiple access (OFDMA) used in LTE-Advanced. Various practical factors are taken into account in the evaluations such as the processing delay and upper-bound of the amplifier gain of the L1 relay, capacity limitation of the backhaul channels, and empty buffer status...
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