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In this letter, a sphere decoding (SD) based noncoherent multiple symbol detection (MSD) scheme is proposed for differential space-time block coded (DSTBC) ultra-wideband (UWB) impulse radio systems. Exhaustive search based maximum likelihood (ML) MSD is impractical in DSTBC-UWB systems since its complexity exponentially increases with observation window size. To decrease the computational complexity,...
In this paper, we propose a novel transmit preprocessing scheme using Channel Selection (CS) to jointly design PreRake and Precoding for multiple-input multiple-output Ultra-Wideband (MIMO-UWB) communications. The PreRake technique is implemented to exploit the advantage of multipath diversity and can achieve spatial multiplexing based on our proposed CS. The combination of CS and PreRake transforms...
Synchronization is a crucial task and big challenge for ultra-wideband (UWB) systems, especially in the presence of inter-symbol interference(ISI) and inter-frame interference (IFI). This paper proposes a blind synchronization and demodulation algorithm that is capable of mitigating ISI and IFI for noncoherent UWB system. Employing a series of codeword matching and averaging operations, the proposal...
Existing inter-frame interference (IFI) and intersymbol interference (ISI) mitigation schemes for noncoherent UWB Impulse Radio (UWB-IR) mainly focus on signal processing after nonlinear autocorrelation receiver (AcR) or energy detector (ED). Steering the wheel, a simple but effective IFI and ISI pre-mitigation scheme is proposed in this paper, which realizes IFI and ISI mitigation before ED. Block...
In this paper, a joint blind synchronization and demodulation scheme is developed for ultra-wideband (UWB) impulse radio systems. Based on the prior knowledge of the direct-sequence (DS) spread codes, the proposed approach can achieve frame-level synchronization with the help of frame-rate samples. Taking advantage of the periodicity of the DS spread codes, the frame-level synchronization can be carried...
In this paper, a novel synchronization algorithm dispensing with searching is proposed for UWB communications. By adopting a stream of alternating orthogonal pulses, frame-level synchronization can be achieved without training sequence involved. Without any searching procedure, the timing offset estimator is obtained in a closed form, therefore considerably reducing the synchronization time. Simulations...
Relying on judicious training symbols, we can construct a redundance-included demodulation template (RDT) from the received signal. When the RDT is available, there are two approaches to select. One is to demodulate transmitted symbols directly by the RDT, which does not require timing acquisition, and thereby has considerably lower complexity. The alternative is to first acquire the timing offset...
In this paper, two novel space-time coded modulation and corresponding noncoherent detection schemes for Ultra-Wideband (UWB) impulse radio system are proposed. An additional orthogonality is introduced to original Orthogonal Space-Time Block Code (OSTBC) for performance enhancement in the proposed two schemes, which is termed as Dual Orthogonal Space-Time Coded Modulation (DOSTCM). The specially...
In this paper, a blind two-step synchronization algorithm is proposed for direct-sequence (DS) ultra-wideband (UWB) communication systems. In the first step, the start of individual frames is estimated via simple square, overlap-add operation and energy detection technique. Then the first frame in each symbol is identified by exploiting the randomicity of DS codes and information symbols at the second...
One of the biggest challenges in ultra-wideband impulse radio (UWB-IR) is timing acquisition. To accomplish synchronization, a novel modulation scheme is presented in this paper. Relying on the unique signal structure and the first order- statistics of the received signal, the timing offset can be acquired by energy detection even if in the presence of inter-frame interference (IFI) and inter-symbol...
One of the biggest challenges in ultra-wideband (UWB) communications is the accurate and rapid timing acquisition for the receiver. This paper presents a timing acquisition scheme dispensing with searching for UWB communications. Without training sequence involved, timing offset parameter is estimated by exploiting a stream of alternating orthogonal pulses, and frame-level synchronization can be achieved...
A novel transmit-reference (TR) signaling scheme for UWB systems is proposed in this paper, where by invoking m-sequence codes the reference and data pulses are transmitted side by side to increase the data rate. This structure enables demodulation with a conventional correlation receiver despite existing server inter-pulse interference (IPI). For higher output SNR, an improved demodulation scheme...
In this paper, a novel scheme is developed for chip-level timing in UWB communications. To accomplish the proposed algorithm, the time hopping (TH) code is transformed to the spread time hopping (STH) code firstly, without changing ideas of UWB modulation. Invoking the cyclic autocorrelation of STH code, the timing parameter is acquired without training sequence. Desirable performance is brought out...
In this paper, a novel quasi-4PPM modulation is presented firstly for UWB systems, and then the corresponding synchronization and demodulation schemes are proposed. Due to the nature of the unique signal structure, the information bits are transmitted and demodulated by twos, which doubles the transmission efficiency compared with conventional existing methods under the same condition. Besides, the...
In this paper, we propose a new blind synchronization algorithm for ultra-wideband (UWB) systems based on pseudo random time-hopping (TH) codes. The synchronization parameter is acquired by using integrate-and-dump (I&D) among several segments (these segments are chosen according to a user-specific TH codes) of the observation waveform and peak-picking the outputs of the I&D device. Due to...
A low-complexity blind channel estimation algorithm is proposed for ultra-wideband (UWB) wireless communication systems in dense multipath environments. To accurately estimate channel impulse response (CIR), the proposed algorithm exploits an unconventional denoising fast Fourier transform (FFT) to perform deconvolution. The denoising FFT employs the discrete wavelet transform (DWT) to compute discrete...
This paper deals with channel estimation for ultra-wideband (UWB) wireless communication systems in dense multipath environments. An improved Kalman filter algorithm is proposed for estimating and tracking the channel impulse response (CIR) of time-varying channels. This algorithm includes two steps: frequency-domain pre-filter and Kalman filter. By introducing frequency-domain pre-filter to simplify...
In this paper, a low complexity blind synchronization algorithm is proposed for ultra wideband (UWB) communication systems in the multipath environment. Using the first order statistics of the received signal, the proposed algorithm is carried out without aided data. The synchronization parameter and nuisance ones are separated from each other on account of the structure of the Vandermonde matrix,...
In this paper, a novel rapid synchronization algorithm is proposed for UWB systems with noncoherent receivers based on an energy capture scheme, fully exploiting adequate multipath component. Only one symbol observation is required to acquire synchronization, which speeds up the overall synchronization process. And the lower complexity is achieved via not only the synchronization scheme but also the...
In this paper, a novel two-stage synchronization algorithm is proposed employing an energy capture scheme in the first stage and a correlation-and- comparison method in the second stage, fully exploiting adequate multipath component. Only one symbol observation is required to achieve frame synchronization, which speeds up the overall synchronization process with higher accuracy and lower complexity...
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