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Coordinated multipoint (CoMP) transmission is a key technique in 4G long term evolution (LTE) systems to enable broadband communication and coverage for user equipments (UEs) at the cell edge. However, as the transmit signals will reach the UE at several and varying delays, unsynchronized CoMP transmission might experience large timing offsets (TOs), imposing a significant performance loss. In this...
In multiple-input multiple-output (MIMO) systems adopting space shift keying (SSK), the use of adaptive precoder on transmitter offers the opportunity to improve its performance significantly. One major challenge in precoder operation is the difficulty in obtaining the full channel state information on transmitter (CSIT). In this work, we investigate the precoder design for SSK-MIMO systems with limited...
Multiple-input multiple-output (MIMO) systems with implicit feedback utilize uplink channel state information (CSI) for downlink transmit beamforming, relying on over-the-air channel reciprocity. We develop real-time hardware for multiuser MIMO transmission with implicit feedback based on orthogonal frequency division multiplexing (OFDM), with field programmable gate arrays (FPGAs). This paper presents...
Interference alignment (IA) is a scheme to achieve degrees of freedom (DOF) of interference network at high signal-to-noise ratio (SNR). In order to implement IA scheme in frequency-division duplexing (FDD) system, receivers feedback channel state information to transmitters. The key problem is to acquire accurate transmitter channel state information (CSIT) in the presence of the quantization error...
The availability of channel state information (CSI) at the transmitter is crucial to multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) systems to suppress interference with precoding techniques. In a MIMO-OFDM frequency division duplex (FDD) system, the amount of CSI required by the transmitter increases linear with the number of subcarriers, and therefore becomes...
This paper presents an improved decryption method aiming at covert Orthogonal Frequency Division Multiplexing (OFDM) transmission with cyclic delay diversity (CDD) featured multiple input multiple output (MIMO) technology. Particularly, we take advantage of the inherent sparse structure of multi-path wireless channel as well as Compressive Sensing (CS) technology, which has attracted a considerable...
In this paper, a robust transmission scheme for simultaneous wireless information and power transfer (SWIPT) in the presence of an eavesdropper is proposed. With imperfect channel state information (CSI) at the transmitter, the optimal transmit covariance matrix is obtained based on the maximization of the worst case harvested energy for the energy receiver (ER) while guaranteeing the achievable secrecy...
In the simultaneous wireless information and power transfer (SWIPT) system, the security becomes a major concern. This is because the energy harvesting (EH) operates with much higher received power than conventional information decoding (ID), which leads the environment vulnerable to eavesdropping. In this work, we propose a joint transceiver design to maximize physical-layer security while guaranteeing...
In this paper, we propose an opportunistic user selection criterion to obtain a multiuser diversity gain for secure communication. At the same time, we also propose a strategy for utilizing a small base station in heterogeneous networks as a helper or a jammer adaptively. Our approach is to maximize the secrecy achievable rate based on an analytically derived lower bound instead of the original objective...
We present a novel approach to network security against passive eavesdroppers by employing a configurable beam-forming technique to create tightly defined regions of coverage for targeted users. In contrast to conventional encryption methods, our security scheme is developed at the physical layer by configuring antenna array beam patterns to transmit the data to specific regions. It is shown that...
This paper presents a statistical model for off-body radio channels in an indoor multipath environment. The model considers the distance dependent mean path loss, and describes body shadowing and fast fading components in a statistical way. The modelling of wearable antennas in Body Area Networks (BANs) has been separated into antennas in the vicinity of the body (full wave simulations), including...
The outdoor deployment of small cells (SCs) in heterogeneous cellular networks for mobile communications is advantageous from both the capacity and the power consumption point of view. In practice, however, the network operators are limited by the high costs associated with the provisioning of backhaul communication and power supply to the SCs. This paper addresses these operational challenges by...
In this paper, we present the channel measurement results of vehicle-to-vehicle (V2V) measurement campaign carried out in Oulu city center, Finland. The measurements were conducted with EB Propsound CSTM at 2.3 GHz and 5.25 GHz center frequencies. The antennas were installed on the roof of the vehicles and the measurements were performed for single-input multiple-output (SIMO) antenna configuration...
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