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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...
Unmanned aerial vehicles (UAVs) can be used as aerial base stations (BSs) to deliver broadband wireless connectivity during temporary events, at hotspot areas, or after disasters that may destroy existing communication infrastructure. Since UAV- BSs are low power nodes, their efficient placement is important to reap the maximum capacity and coverage benefits from their deployments. By making use of...
Wireless networks with directional antennas, like millimeter wave (mmWave) networks, have enhanced security. For a large scale mmWave ad hoc network in which eavesdroppers are randomly located, however, eavesdroppers can still intercept the confidential messages, since they may reside in the signal beam. This paper explores the potential of physical layer security in the mmWave ad hoc networks. Specifically,...
In this paper, we look into the issue of intra-cell uplink (UL) pilot orthogonalization and schemes for mitigating the inter-cell pilot contamination with a realistic massive multi-input multi-output (MIMO) orthogonal frequency-division multiplexing (OFDM) system model. First, we show how to align the power-delay profiles (PDP) of different users served by one BS so that the pilots sent within one...
In the future, data will be collected from a wide range of devices (the Internet of Things or IoT). This may be from simple transmit only devices such as sensors or devices with two way communications so control information can be sent to the device. A Smart Grid depends on such an infrastructure since it is used to collect energy usage data which is then used for billing as well as to make decisions...
Robust adaptive beamforming (RAB) has became a popular research topic, with various RAB techniques being proposed in the past decades. However, because the sample covariance matrix rather than the interference-plus-noise co-variance matrix is used to calculate the weight vector, the performance of the previously developed RAB techniques is not optimal. In this paper, a novel RAB algorithm, which uses...
Spectrum pooling is not typically used in current cellular networks, because it only provides a slight performance improvement while requiring heavy coordination among different cellular operators. However, these problems can be potentially overcome in millimeter-wave (mmWave) networks, thanks to the use of beamforming both at base stations and at user equipments. In this paper, we develop a joint...
Massive MIMO and beamforming is commonly considered as one of the key technologies for future cellular communications. It is targeted to solve the capacity requirements in enhanced mobile broadband and enable new services in other communication fields, e.g. machine type communications. In this work, we study M-MIMO technology in a novel approach, combining system simulations and modeling with hardware...
This paper presents a novel array configuration based on the combination of the sum and difference co-arrays. There have been many studies on the array antenna configurations which enhances the array degree of freedom (DOF), however the maximum DOF of the configurations based on the difference co-array is often limited. We try to further enhance the DOF by combining the concepts of the sum coarray...
Millimeter wave (mmWave) is a promising approach for the fifth generation cellular networks. It has a large available bandwidth and high gain antennas, which can offer interference isolation and overcome high frequency-dependent path loss. In this paper, we study the non-uniform heterogeneous mmWave network. Non-uniform heterogeneous networks are more realistic in practical scenarios than traditional...
In this paper, the effects of interference on the performance of dual-hop transmission with fixed-gain amplify-and-forward relaying is presented in terms of bit-error rate (BER). Particularly, a scenario with multiple relays and multiple antennas at destination is considered jointly with optimum combining (OC). The moment-generating function (MGF) of the signal-to-interference-plus-noise ratio (SINR)...
Most of the already existing spectrum detection algorithms are based on each channel sensing, which lowers the spectrum detection efficiency and makes detecting the spectrum holes promptly very difficult. Traditional MIMO systems are based on 2D MIMO spatial channel models, but in fact the real channel is 3D characterized. This paper proposes a novel scheduling scheme for cylindrical antenna based...
Massive multi-input multi-output (MIMO) can provide high throughput improvements by using a large number of antennas to serve a small number of terminals simultaneously. Due to channel hardening of massive MIMO, this paper directly investigates the approximate network throughput with zero-forcing beamforming (ZFBF) and conjugate beamforming (CBF) schemes when channel state information (CSI) acquisition...
Code-Division Multiple-Access (CDMA) [1] is widely used in both civil and military applications. It does take advantages from the system characteristics. For example, higher data rate and user capacity, better multipath resolution [2] and resistance to jamming, low probability of interception, accurate timing and ranging, and more importantly, stronger ability to suppress interference and jamming...
In this paper, the downlink performance of two-tier heterogenous network is investigated. We consider a scenario where the macro-tier is empowered by massive antenna-array thus allowing for Massive multiple-input multiple-output (MIMO) transmission scheduling. The small cellular network complements the macro-tier capacity. We propose a novel channel allocation mechanism which optimally splits the...
This paper investigates a multi-pair two-way massive MIMO amplify-and-forward full-duplex relay (MM-AFFDR) system over Ricean fading channels, where multiple pairs of full-duplex users exchange information within pair through a full-duplex relay with very large number of antennas (M for transmission and M for reception). Firstly, the zero-forcing reception/zero-forcing transmission (ZFR/ZFT) processing...
The mean bit error rate (BER) for the uplink of a multicarrier-code-division multiple access (MC- CDMA) cellular system is evaluated. The system employs a multiuser decorrelating detector in the receiver, a uniform antenna array at base stations and perfect power control. The scenario assumes the presence of multiple access interference (MAI), co-channel interference (CCI), additive white Gaussian...
This paper presents experimental results of our proposed null-space expansion scheme for multiuser massive MIMO in time varying channel. Multiuser MIMO transmission with proposed scheme can suppress inter-user interference (IUI) caused by outdated channel state information (CSI). The excess degrees of freedom (DoFs) of massive MIMO is exploited to perform additional null-steering...
In the next generation wireless systems, where m-MIMO and mmWave should be combined with beamforming techniques, array optimization at receiver ensuring a good SINR level can become a very large problem. Meta-heuristics can be an adequate approach to solve this problem with a mild computational effort. In this work, different meta-heuristics are implemented and applied to this problem, with Differential...
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