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This paper presents a solution to the coherent change detection (CCD) problem using multi-polarization synthetic aperture radar (SAR) imagery. The multi-polarization SAR imagery (i.e., the day-1 reference and day-2 test images) are modeled as jointly correlated complex Gaussian vectors with unknown correlation, rho = gammaejPhi . Maximum likelihood estimates of the unknown phase and coherence parameters...
The aim of acquiring knowledge about the emotional state of a speaker is to improve the robustness of speech recognition systems, as the mechanisms producing speech vary in the presence of emotions, and also to improve the machine's perception of a speaker's emotional state so as to respond to his/her requests more appropriately. The paper proposes an approach based on genetic algorithms to determine...
Recently, many papers have been published on the designs of predistortion systems for power amplifiers (PA). Most of these studies are based on computer simulations. In this work, we examine our predistorter (PD) designs on a practical microwave PA in a laboratory setup. The objective is to validate two PDs of different design approaches. The first PD is modeled using a simplicial canonical piecewise...
In this paper, a new variant of multicarrier code division multiple access (MC-CDMA) system is proposed and analyzed for time varying multipath fading channels. At the transmitter, data bits at different frequency bands are spread in the time domain and these spread chips are circularly shifted onto different frequency bands while the time lapses. As a result, the spread data chips are assigned to...
This paper provides n framework for deriving MIMO capacity bounds that takes channel estimation error into account by using the Cramer-Rao bound (CRB). Combining the CRB with capacity analysis allows for studies of the trade-off between estimation performance and throughput. The framework is used to investigate the impact of the spatio-temporal structure found in practical channel sounding experiments...
In this article we derive the optimal (soft) RAKE MRC (maximum ratio combiner) under a sparse channel model. In contrast to many previous approaches, we do not separate the problem of channel estimation and symbol detection. Instead we treat the problem of symbol detection given data and a training sequence together. We illustrate the performance of our approach by numerical examples
A parametric model for indoor ultra-wideband (UWB) impulse response at the receiver is derived analytically based on diffusion phenomenon and stochastic differential equations (SDE). This novel approach considers the channel in continuous space instead of characterizing the discrete multipath components. It was hypothesized that the multiple wave reflections in the rich scatter indoor environment...
In wireless communications, about 25% of the bandwidth is dedicated to training symbols for channel estimation. By using a semi-blind approach, the training sequence length can be reduced while improving performance. The principle is as follows: the detected symbols (hard decision) are fed back to the channel estimator in order to re-estimate the channel more accurately. However, semi-blind approach...
In a multi-path channel an orthogonal frequency division multiplexing (OFDM) system is very robust to frequency selective fading, but it is sensitive to the time selective fading of the mobile channel. Time selectivity of the channel causes inter-carrier-interference (ICI) in OFDM, thereby degrading the performance significantly and increasing the computational complexity of the receiver. On the other...
We present a technique that improves channel estimation accuracy by using the estimates of channel coefficients from previous packets that are received from the same transmitter. A mechanism that accurately estimates the carrier and timing phase differences between successive packets is discussed. Simulations show that the performance improvement of 0.5-1 dB is obtained. The improvement is particularly...
This paper discusses audio enhancement when a strong, additive noise is present only during a known or easily detected period of moderate length (of around one second). The signals may contain intelligible components such as speech or music, and may also contain desired, but unintelligible, background components such as rivers or waterfalls. A first estimate synthesizes the unintelligible components...
In this paper, we propose an algorithm for the identification of objects from a noisy and cluttered background in video sequences. Our algorithm is based on the marked point process (MPP) framework, which provides a useful tool for integrating object spatial information into the identification process. The maximum a posteriori (MAP) estimation of a set of points corresponding to the centroids of objects...
Spectral shaping is one of the primary technical challenges in spectrally constrained multiple access applications. In this paper, we introduce an efficient spectrum shaping technique based on code-hopping CDMA. In this approach users are allowed to hop between available spreading codes with different probabilities. The proportion of time that each code is used for spreading is determined by an assigned...
Decentralized channel state information is exploited for optimal transmission policies for non-cooperative sensors in wireless networks with the multipacket reception capability. The problem is formulated as a non-cooperative game of a finite number of players and actions with a continuous channel state space. We prove the existence of a Nash equilibrium at which every sensor adopts a threshold policy...
In this paper, we introduced a new fast Fourier transform algorithm with linear multiplicative complexity for real and complex input signals. The proposed algorithm also reduces the total number of operations (arithmetic complexity, or the number of multiplications and additions) compared to the existing methods, such as Duhamel, Heideman, Burrus, Bi et al., Bouguezel et al
We consider a family of user dedicated downlink channel estimation methods in WCDMA receivers which are particularly suited for the presence of dedicated channel transmit beamforming and which assume no a priori knowledge of the path delays and the beamforming parameters. They exploit all the transmitted pilot sequences as well as the structured dynamics of the channel. First we build slot-wise least...
Suppose that a signal's bandwidth exceeds that of any available receiver, but that overlapping sub-bands of the signal are collected by multiple receivers that cover the entire signal bandwidth. An eigenanalysis method is described for reconstruction of the signal from the sub-bands. The technique produces rapid estimation of combining coefficients that maximize SNRs of combined "overlap"...
We present a new method to adaptively configure the focal-length of a pan-tilt-zoom camera to track a point target with improved accuracy. The target tracker is implemented by using a Rao-Blackwellized particle filter. The focal-length of the camera is configured to include a time varying percentage of the projected particles on the camera image plane. The performance of the adaptive zoom algorithm...
For a set of T independent N-variate Gaussian training samples (T < N), we derive maximum the likelihood (ML) estimate of its time-varying autoregressive model of order m, TVAR(m), and method to estimate the order of an autoregressive (AR) model, regardless of its stationary or time-varying nature. For the estimated order m, we then use the TVAR(m) model parameters to calculate the ML time-frequency...
In this paper we propose a morphing approach that can synthesize microphone signals with the acoustical characteristics of specific instrument. The proposed method is composed of three stages. In the first step, the short-time Fourier transform is used to represent signals as a 3-D structure. The cosine similarity measure is then applied to this pre-processed time-frequency information for locating...
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