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This paper investigates the joint robust beamforming and artificial noise design in two-user interference networks, where one of the two pairs is wiretapped by an external eavesdropper, and only imperfect eavesdropper's channel state information (ECSI) is available for the two pairs. Under individual transmission power constraint, our goal is to maximize the worst-case achievable secrecy rate of the...
The dynamic stochastic resource optimization problem in heterogeneous cloud radio access networks (H-CRANs) is researched in this paper, characterizing the cooperative beamforming with fronthaul capacity and queue stability constraints. To make the average energy efficiency (EE) of remote radio heads (RRHs) arbitrarily close to the optimum and maintain system queue stability, the EE optimization problem...
As a promising multiple access techniques for 5th generation (5G) wireless systems, non-orthogonal multiple access (NOMA) has received many attentions recently. In this paper, we study the NOMA based downlink multi-user beamforming system, where the base station (BS) tries to transmit information to multiple user clusters and each beam serves one user cluster compromising of two users simultaneously...
Millimeter wave (mmWave) technologies can enable current mobile communication systems to achieve higher data rates. However, wireless channels at mmWave frequencies experience higher isotropic path loss. Therefore, employing a suitable beamforming algorithm is an indispensable element of any mmWave system. Traditional multiple-input multiple-output (MIMO) systems employ digital beamforming where each...
In order to exploit millimeter wave (mmWave) bands for 5G communications, challenges mainly due to blockage and strong dependency on beamforming operation need to be overcome. In this work, we address some of the fundamental issues related to the use of mmWave bands for 5G communications, from propagation channel characteristics and modeling to the implications on system and network architecture design...
In this paper, the problem of distributed beamforming for cognitive radio systems with frequency-selective channel is studied. Our proposed scheme is based on the filter-and-forward (FF) relay beamforming approach and aims to maximize the received signal to interference plus noise ratio (SINR) at the secondary destination, while suppressing the interference introduced to the primary user. This scheme...
Massive MIMO is envisioned as one of the key enabling technologies for 5G wireless and beyond. While utilizing the spatial dimension to reduce interference and increase capacity in multi-user scenarios, massive MIMO base stations present several unique implementation challenges due to their large physical size and the high datarate generated by all the elements. To be cost-effective and energy efficient,...
Millimeter wave (mmWave) systems will likely employ large antenna arrays at both the transmitters and receivers. A natural application of antenna arrays is simultaneous transmission to multiple users, which requires multi-user precoding at the transmitter. Hardware constraints, however, make it difficult to apply conventional lower frequency MIMO precoding techniques at mmWave. This paper proposes...
Next generation cellular networks will experience the combination of femtocells, millimeter-wave (mmW) communications and massive antenna arrays. In addition to benefits in terms of an increased communication capacity, this mix of technologies can be fruitfully exploited to enable high-accuracy indoor positioning. In fact, thanks to the high beamforming capability of massive arrays, mobile terminal...
This paper investigates the impact of the channel code rate and of the antenna processing method on the behavior of a wireless network in which interference cancellation enables the coexistence of multiple concurrent communications between different node pairs that share the same communication medium. Moving from an exhaustive Monte Carlo evaluation of the capture probability in deterministic and...
Coordination is foreseen to be an important component of future mobile radio networks. It is especially relevant in heterogeneous networks, where high power base stations produce strong interference to an underlying layer of low power base stations. This work investigates the impact of the interference from base stations which are not part of the cooperation. This interference is called out of cluster...
Millimeter wave (mmWave) communication is being seen as a disruptive technology for 5G era. In particular, 60GHz frequency band has emerged as a promising candidate for multi-Gbps connectivity in indoor and hotspot areas. In terms of network architecture, cloud radio access network (CRAN) has emerged as the most promising architectural alternative to enable efficient baseband processing and dynamic...
The vast interconnectivity of devices in the Internet of Things (IoT) and Cyber-Physical systems under wireless environments facilitates information exchange, but challenges network security. In this paper, cooperative beamforming for secure communications is studied in wireless cyber-physical systems, where two legitimate devices communicate with the help of amplify-and-forward (AF) relays, and the...
In this paper, we propose a secrecy communication scheme for half-duplex amplify-forward relay networks in the presence of multiple eavesdroppers. Unlike conventional relay network, we consider that the relay is “green”, i.e., it is powered by the energy harvested from the relay observations. The transmission can be divided into two time slots. In the first time slot, the source and destination transmit...
Massive multiple input multiple output (MIMO) millimeter wave (MMW) communications allow for a compact implementation and efficient beamforming. In this paper we focus on the problem of estimating the massive MIMO channel in a code modulated path sharing multi-antenna (CPMA) architecture, when a limited number of radio frequency (RF) chains is available, and beamforming is performed through a combination...
Millimeter Wave (mm-w), especially the 60 GHz band, has been receiving much attention as a key enabler for the 5G cellular networks. Beamforming (BF) is tremendously used with mm-w transmissions to enhance the link quality and overcome the channel impairments. The current mm-w BF mechanism, proposed by the IEEE 802.11ad standard, is mainly based on exhaustive searching the best transmit (TX) and receive...
This paper addresses the research question on how digital beamsteering algorithms can be combined with analog beamforming in the context of millimeter-wave communication for next generation (5G) cellular systems. Key is the use of coarse quantisation of the individual antenna signals next to the analog beamforming. The extreme case of single bit quantization is analyzed. Direction-of-Arrival (DoA)...
In this paper, we investigate the outage performance of an amplify-and-forward (AF) multiple input multiple output (MIMO) opportunistic relay selection system under time-varying channels. A practical scenario is considered, where both the relay selection and the beamforming transmission are performed with outdated channel state information (CSI), due to channel fluctuations and delays involved in...
This paper presents a secure beamforming design to prevent eavesdropping on multiple-input multiple-output (MIMO) device-to-device (D2D) communication. The devices communicate via a trusted relay which performs physical layer network coding (PNC), and multiple eavesdroppers are trying to intercept the device information. The beamforming design is based on minimizing mean square error of the D2D communication...
This paper considers a heterogeneous downlink cloud radio access network (C-RAN) where all the base stations (BSs) in the network are connected to a central processor (CP) via capacity-limited backhaul links. Under this model, we investigate the message-sharing transmission strategy where the CP shares each user's message with a fixed subset of BSs, which then serve the user through joint beamforming...
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