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The robustness of the time reversal (TR) scheme in a non stationary channel environment has been previously studied for ultra-wide band (UWB) channels. However, its robustness with different bandwidth specially for bandwidths significantly lower than ultra-wide bandwidths has not been established. In this paper, the performance of a TR communication system has been studied for large number of bandwidths...
By employing the regularized block diagonalization (RBD) preprocessing technique, the multi-user multi-input multi-output (MU-MIMO) broadcast channel is decomposed into multiple parallel independent single user multi-input multi-output (SU-MIMO) channels and achieves the maximum diversity order at high data rates. The computational complexity of RBD, however, is relatively high due to two singular...
We consider the problem of designing binary antipodal uniquely decodable (errorless) code sets for overloaded code-division multiplexing applications where the number of signals K is larger than the code length L. Our proposed errorless code set design aims at identifying the maximum number of columns that can be potentially appended to a Sylvester-Hadamard matrix of order L, while maintaining the...
For the design and performance evaluation of advanced wireless communication systems employing multiple-input multiple-output (MIMO) technologies, realistic MIMO channel models with a good tradeoff between accuracy and complexity are indispensable. This paper compares the statistical properties of the two latest standardized MIMO channel models: Long Term Evolution-Advanced (LTE-A) and IMT-Advanced...
This paper addresses the problem of feedback design for MU-MIMO (multi-user multiple input multiple output) transmission in 3GPP Long Term Evolution (LTE) systems. The CSI (channel state information)-based feedback introduced in the latest release of LTE, Rel-10 is adopted in MU-MIMO transmission and potential performance gains are demonstrated over Rel-8 CQI/PMI (channel quality indicator/precoding...
This paper proposes means to exploit the additional degrees of freedom that can be achieved by using beam-tilting antennas for the purposes of multiuser communication without substantially increasing investment in system resources. Specifically, by using such beam-tilting antennas the wireless channel can be used as a means to spread the users in space rather than in frequency as is currently the...
In this paper, we study adaptive transmission mode switching between statistical and instantaneous channel state information (CSI) aided single-user (SU) and multiuser (MU) precoding for a two-user downlink system, where two transmit antennas are equipped at the base station and each mobile user has one receive antenna. In the case where only statistical CSI (SCSI) is available at the transmitter,...
Detection of cyclostationary primary user (PU) signals in colored Gaussian noise for cognitive radio systems is considered based on looking for a cycle frequency at a particular time lag in the cyclic autocorrelation function (CAF) of the noisy PU signal. We explicitly exploit the knowledge that under the null hypothesis of PU signal absent, the measurements originate from colored Gaussian noise with...
A technique to predict the channel transfer functions into time direction and into frequency direction in multiple antenna systems is investigated in this paper. Having channel state information in a mobile radio system at both sides of the transmission link is crucial for many sophisticated transmission techniques. Typically, only receiver side channel state information can be achieved based on the...
Modeling the link quality is essential in achieving and maintaining stable communication and minimizing energy consumption by controlling packet transmissions across a wireless sensor network. The quality of the communication links is a function of many variables including location, distance, direction and time. In this paper, we investigate the statistical channel models for spatial and temporal...
In this paper we present some channel measurement results of distributed multiple-input multiple-output (D-MIMO) systems inside a MD-82 aircraft. Channel capacity and spatial correlation are analyzed from the measured channel matrix. Capacity results of 7 different systems (six D-MIMO systems and a SISO system) are discussed. It is found that D-MIMO systems yield significant capacity gains as compared...
In this paper the hardware setup and a field trial of a transmitter delay diversity (DD) system for DRM+ (Digital Radio Mondiale, Mode E) in ‘urban’ areas in the city of Hannover are presented. DD should help against destructive interferences resulting in signal dropouts, especially for slow receiver velocities. A closer look is taken on the spatial correlation of the channel paths and their influence...
A sensor network's motes observe the environment, make estimates based on observations with spatially correlated noise sources, and then send/relay these estimates to a Cluster-Head (CH). A novel scheme based on dithered quantization and channel compensation is used to ensure that each mote's local estimate received by the CH is unbiased. Based on an upper bound of the noise covariance matrix, the...
Support-Vector Machines (SVM) have received a great interest in the machine learning community since their introduction, especially in Outlier Detection in Wireless Sensor Networks (WSN). The Quarter-Sphere formulation of One-Class SVM (QS-SVM), extends the main SVM ideas from supervised to unsupervised learning algorithms. The QS-SVM formulation is based only on Spatio-Temporal correlations between...
In this paper we propose a reduced-complexity two-stage time and frequency synchronization approach for OFDM systems, operating in multipath channels. The proposed approach exploits a single-symbol preamble with a repetitive structure, composed of two identical m-sequences. The first coarse stage, based on a sliding correlation, finds out the reduced uncertainty interval over which the second fine...
In order to save energy of sensors in the process of gathering data and transmitting information, Compressive Sensing (CS), as a novel and effective signal transform technology, has been used gradually in Wireless Sensor Networks (WSNs). In traditional usages of CS techniques in the previous literatures, the sparsities of the signals has to be known beforehand, which is much more importance for their...
Sensor selection is to pick out an appropriate subset of active sensors for reliable collaborative sensing. Naturally, the selected sensors should be as uncorrelated as possible to have more independent sensing outputs for information fusion. In this paper, various uncorrelation metrics are unified by the concept of Bregman divergence. The sensor selections are then systematically formulated as NP-hard...
This paper is concerned with the study of confidential communication through independent and identically distributed (i.i.d.) and evenly correlated Rayleigh fading channels, where a single antenna transmitter communicates with the corresponding receiver in the presence of an eavesdropper. Both the receiver and eavesdropper are equipped with multiple antennas and employ diversity combining receptions...
Measurement studies of YouTube show that there are some distinctive properties regarding to video sharing service, e.g., small clip size, suggestion links between related clips. This observation motivates us to explore the possibility to use peerassisted approach to offload content providers. Specifically, we want to leverage the suggestion links between video clips to construct cooperative caching...
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