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In this paper, we discuss the inter-array decoupling technique suitable for MIMO full-duplex, which uses a combination of the end-fire antenna arrangement and eigen-beamforming. An experimental evaluation clarifies that the end-fire antenna arrangement contributes to the reduction of the inter-array coupling by 18.7 dB compared with the facing antenna arrangement, and that the small antenna aperture...
Massive MIMO enables the improvement on the transmission rate without increasing the burden on the signal processing by employing a large number of antennas at a base station (BS). However, it is reported that CSI estimation itself has a large overhead when considering massive MIMO. The authors have proposed analog-digital hybrid massive MIMO configuration which eliminates CSI estimation itself by...
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,...
Next generation wireless promises high data rate using advanced MIMO techniques. Large-Scale antenna system, or massive MIMO, has been proposed as a strong candidate for broadband next generation wireless applications. However, pilot contamination is one of the major challenges that limits the promised massive gains. In this paper, a new pilot assignment procedure is proposed to mitigate the pilot...
In Cognitive Radio Networks (CRNs), the spectrum underlay approach enables primary and secondary networks to transmit simultaneously, as long as the interference from the secondary network to the primary network is below certain threshold. As the recent advancement of the underlay approach, the transparent coexistence exploiting MIMO interference cancellation was proposed. Previous works assume that...
The hopeful technique Massive MIMO is provided to increase the data rates of mobile communication, by arranging antennas to hundreds of the base stations which is the most promising solution for the fifth generation of cellular communication network. In order to cope with the huge demands of communications in the network it has been found that it is useful to have multiple receivers served in the...
Massive MIMO promises large spectral and power efficiency. However, pilot contamination, a well known challenge in massive MIMO, limits these aspired gains. In this paper, we propose a pilot hopping sequence along with a pilot reuse strategy for pilot decontamination. A simple hopping scheme is proposed and simulated in an uplink L-cells system where every user is assigned distinct pilot sequences...
This paper proposes an inter-symbol interference (ISI) suppression scheme employing periodic signals for network MIMO-OFDM systems. Network MIMO-OFDM suffers from the ISI due to long time difference of arrival (TDOA) especially in large cells. In the proposed scheme, the periodic signals generated by only the even-numbered sub-carriers are adopted for ISI-affected users while the traditional non-periodic...
This paper considers a multi-way massive multiple-input multiple-output (MIMO) relaying system. The bearing-information is exchanged among multiple users with the help of a multiple-antenna relay (the base station). The maximum-ratio (MR) processing is applied at the relay under the assumption of perfect channel state information. The spectral efficiency and the asymptotic results for the signal-to-interference-plus-noise...
At the current state in multiuser detection, MMSE detector is very popular because it exhibits a good balance between performance and complexity. Therefore, we investigate the capacity-aware version of the MMSE scheme, linear detection method. In this paper, an novel MMSE MIMO detector is proposed with respect to MMSE MIMO channel estimation. We will show how a two-step MMSE MIMO estimator can be...
Interference Alignment (IA) as an effective interference management mechanism has become a hot spot in the field of wireless communication systems in recent years. In order to investigate the significance of IA technique to downlink cellular networks, we propose a new way based on the rank constrained rank minimization theory in this paper. Our proposed algorithm aims at finding out the pre coding...
3G/4G wireless systems employed multiple antennas at both the transmitter and receiver offered significant gains over single-antenna systems. MassiveMIMO (MM) is one of the 5G technologies, which supports to increase the demand for high speed data, capacity, energy efficiency and spectral efficiency. It is known that space-time multiplexing and/or coding offer attractive means of combating fading...
In this paper, we analyze the downlink (DL) performance of superimposed pilots in time division duplexing massive multiple-input multiple-output (MIMO) systems, and show that superimposed pilots offer an increased resilience to pilot contamination with respect to time-multiplexed pilots and data. Based on a closed form expression for the DL signal-to-interference-plus-noise ratio (SINR) at the user...
This paper investigates the performance of bidirectional dynamic networks (BDN) with massive multiple input multiple output (MIMO) systems. In BDN, dynamic allocation of the number of uplink and downlink remote radio heads (RRHs) is proposed, which offers a flexible solution to balance the data traffic asymmetry without requiring the time synchronization. Intuitively, the interference between the...
The nested array, which is implemented by nonuniform antenna placement, is an effective approach to achieve O(N^2) degrees of freedom (DoF) with an antenna array of N antennas. Such DoF refers to the number of directions of incoming signals that can be resolved. With the increased number of DoF, an important application of nested array is to nullify the interference signals from multiple directions...
We study the optimality of almost blank subframes (ABSs) that are used to limit interference by muting macro base stations (BSs) in multi-antenna heterogeneous networks (HetNets). In particular, we formulate a linear program to find the optimal blanking decision that maximizes the average rate of a typical user. A closed-form condition is derived, which depends on the multi-antenna transmission schemes,...
Full duplex MIMO communication is one of the key techniques for 5G wireless communication. The main challenge in full duplex operation is the cancellation of the self-interference (SI). In this paper, Transmit Antenna Cancellation technique is considered with symmetric placement of antennas to cancel SI in full duplex MIMO systems. The performance of a full duplex system with this cancellation technique...
The combination of singular value decomposition (SVD)-based beamforming and filter bank multicarrier with offset quadrature amplitude modulation (FBMC/OQAM) has not been successful to date. The difficulty of this combination is that, the beamformers may change dramatically between adjacent subchannels, therefore destroy the orthogonality of FBMC/OQAM real-valued symbols, under frequency selective...
This paper considers the massive multiple-input multiple-output (MIMO) enabled heterogeneous cloud radio access network (C-RAN), in which both remote radio heads (RRHs) and massive MIMO macrocell base stations (BS) are deployed to potentially accomplish high throughput and energy efficiency (EE). In this network, the soft fractional frequency reuse (S-FFR) is employed to mitigate the inter-tier interference...
The asymptotic sum rate performance of multi-cell/multi-user cognitive massive multiple-input multiple-output (MIMO) systems with underlay spectrum sharing is investigated. Specifically, each cell consists of a licensed (primary) multi-user massive MIMO system and a cognitive (secondary) multi-user MIMO system which is allowed to utilize the licensed frequency spectrum provided that the intra-cell...
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