Dahae Chong

Cancellation of Correlation Side-Peaks for Unambiguous BOC Signal Tracking

Based on a combination of the sub-correlation functions composing the autocorrelation of the binary offset carrier (BOC), we propose a novel cancellation scheme of correlation side-peaks to solve the ambiguity problem in the BOC signal tracking. The proposed scheme is applicable to both generic sine- and cosine-phased BOC signals without requiring any auxiliary signal in the receiver. Avoiding the ambiguity problem, the proposed scheme is confirmed from numerical results to provide a better tracking accuracy than the conventional schemes.

A distance measuring scheme based on repeated use of PN sequence

This paper proposes a novel distance measuring scheme based on repeated PN sequence for ultra wide-band vehicle radar systems. The proposed scheme measures the distance between a vehicle and an obstacle based on repeated use of a single short pseudo random sequence. Simulation results show that the proposed scheme provides a shorter mean distance measuring time while keeping a similar measurement error performance to that of the conventional scheme.

A New GNSS Synchronization Scheme

Due to multiple side-peaks in the binary offset carrier (BOC) autocorrelation function, BOC signal synchronization is one of the most challenging tasks for global navigation satellite systems (GNSSs) including Galileo and global positioning system (GPS). Recently, a novel correlation function with reduced side-peaks was proposed for BOC signal synchronization by Julien (6); however, Juliens correlation function still has the side-peaks and can be possible only for sine phased BOC( n,n), where n is the ratio of the pseudo random noise (PRN) code rate to 1.023 MHz. In this paper, we propose a new correlation function for BOC signal synchronization, investigating how multiple side-peaks arise in BOC autocorrelation function. The proposed correlation function does not have any side-peaks and can be generated for any type of BOC signal, sine/cosine phase BOC(kn,n), where k is the ratio of a PRN chip duration to the period of a square wave sub-carrier used in BOC modulation. In addition, an efficient correlator structure is presented for generating the proposed correlation function.

An Improved Timing Synchronization Scheme for BOC Signals

Binary offset carrier (BOC) signal synchronization is one of the most important steps to recover the transmitted information in a global navigation satellite system (GNSS) such as Galileo and global positioning system (GPS). Generally, BOC signal synchronization is achieved based on the correlation between the received and locally generated BOC signals. Thus, the multiple side-peaks in BOC autocorrelation are one of the main error sources in synchronizing BOC signals. Recently, a novel correlation function with reduced side-peaks was proposed for BOC signal synchronization by Julien [8]; however, Juliens correlation function not only still has the side-peaks, but also is only applicable to sine phased BOC(n, n), where n is the ratio of the pseudo random noise (PRN) code rate to 1.023 MHz. In this paper, we propose a new correlation function for BOC signal synchronization, which does not have any side-peaks and is applicable to general types of BOC signals, sine/cosine phased BOC(kn, n), where k is the ratio of a PRN chip duration to the period of a square wave sub-carrier used in BOC modulation. In addition, an efficient correlator structure is presented for generating the proposed correlation function.

An Alamouti Coding Scheme for Asynchronous Cooperative Communication Systems over Frequency Selective Fading Channels

This paper addresses a novel Alamouti coding scheme for asynchronous cooperative communication systems over frequency selective fading channels. In the proposed scheme, the Alamouti coded form at the destination node is constructed through a simple combination of symbols at the source node, instead of the time-reversal operation at the relay nodes used in the conventional scheme. Numerical results show that the proposed scheme achieves a higher order cooperative diversity than that of the conventional scheme.

A two-stage acquisition scheme based on multiple correlator outputs for UWB signals

In ultra-wideband (UWB) channels, the signal energy in the acquisition receiver spreads over correlator outputs due to rich multipaths, making the output of each correlator have only a small portion of the total energy. To enhance the acquisition performance for UWB signals by exploiting the signals spread over a number of correlator outputs, this paper proposes a two-stage acquisition scheme. In the proposed scheme, decision variables are formed by combining a multiple of correlator outputs, allowing it possible to make use of the signal energy spread over the outputs jointly. Simulation results show that the proposed scheme can provide a gain of about 0.6dB over the conventional schemes in various UWB channel environments.

Low Complexity Sequential Estimation Scheme for Pseudo Noise Code Acquisition

In this paper, a low complexity sequential estimation scheme for pseudo noise (PN) code acquisition is proposed, which can not only achieve code acquisition for both inverted and non-inverted PN codes, but also demodulate the spreading data. Numerical results show that the proposed scheme has approximately half the complexity of the conventional scheme while exhibiting a similar mean acquisition time performance to that of the conventional scheme.

Robust estimators for frequency offset of OFDM in non-Gaussian noise

This paper addresses robust estimation for the frequency offset of orthogonal frequency division multiplexing in non-Gaussian noise channels. We first propose a maximum-likelihood (ML) estimator in non-Gaussian noise modeled as a complex isotropic Cauchy process, and then present a simpler, yet still robust, estimator based on the ML estimator. From numerical results, it is confirmed that the proposed estimators offer a substantial performance improvement over the conventional estimators in non-Gaussian noise channels.

A pilot-aided integer frequency offset estimation scheme robust to influence of timing offset for OFDM-based DVB-T systems

A pilot-aided integer frequency offset (IFO) estimation scheme robust to the timing offset is proposed for orthogonal frequency division multiplexing (OFDM)-based digital video broadcasting-terrestrial (DVB-T) systems. The proposed scheme first produces correlation values between each continual pilot (CP) and a predetermined scattered pilot (SP), and then, recorrelates the correlation values in order to reduce the influence of the timing offset. Simulation results show that the proposed IFO estimation scheme is robust to the timing offset and has better estimation performance than the conventional scheme.

A New UWB Synchronization Scheme Using Multipath Components Jointly

In ultra-wideband (UWB) systems, conventionally, the synchronization is to align time phases of a locally generated template and any of multipath components to within an allowable range. However, the synchronization with a low-power multipath component could incur significant performance degradation in receiver operation (e.g., detection) after the synchronization. On the other hand, the synchronization with a high-power multipath component can improve the performance in receiver operation after the synchronization. Generally, the first one among multi- path components has the largest power. Thus, the synchronization with the first path component can make better performance than that with a low-power component in receiver operations after the synchronization. Based on which, we first propose an optimal decision rule based on a maximum likelihood (ML) approach, and then, develope a simpler suboptimal decision rule for selecting the first path component. Simulation results show that the optimal and suboptimal decision rules have better performance than the conventional decision rule in UWB multipath channels.