We present a new approach to the design of the signal generated locally to enhance the performance in tracking of the time-multiplexed binary offset carrier (TMBOC) signal. Considering that the advantages of the TMBOC signal such as a high degree resistance to noise and multipath result from its BOC(6,1) segments, we propose to design the local signal with exploiting only BOC(6,1) segments, which is different from the conventional design approach using both BOC(6,1) and BOC(1,1) segments of the TMBOC signal. Separating and re-grouping the components composing the BOC(6,1) segments, we produce a local signal set and develop a special correlation procedure tailored to the local signal set. Numerical results indicate that the proposed approach achieves the TMBOC signal tracking with a higher degree of robustness to noise and multipath influences over that of the conventional approach in various urban canyon environments.

A unified decision scheme for the classification and localization of cable faults is proposed based on a two-step procedure. Having basis in the time domain reflectometry (TDR), the proposed scheme is capable of determining not only the locations but also types of faults in a cable without an excessive additional computational burden compared to other TDR-based schemes. Results from simulation and experiments with measured real data demonstrate that the proposed scheme exhibits a higher rate of correct decision than the conventional schemes in localizing and classifying faults over a wide range of the location of faults.

본 논문에서는 부반송파 분할 기반의 합성 이진 옵셋 반송파 (composite binary offset carrier: CBOC) 신호를 위한 비모호 신호추적기법을 제안한다. 제안한 기법에서는 CBOC 부반송파를 짝수 개로 분할하여 분할 부반송파들을 생성한다. 각 분할 부반송파는 수신 신호와 상관되며, 이를 통해 얻어진 상호상관함수들은 서로 결합되어 비모호 상관함수를 생성한다. 모의실험 결과를 통해 기존 기법과의 신호추적 오류의 표준 편차를 (standard deviation of tracking error: SDTE) 비교한다. 모의실험 결과, 제안한 기법은 기존 기법 대비 우수한 SDTE 성능을 제공할 뿐 아니라, 모호성 문제를 해결함에 있어 부반송파 분할 수를 선택할 수 있는 유연성을 제공함을 확인한다.

By splitting the auto-correlation of the composite binary offset carrier (CBOC) navigation signal into a group of sub-correlations and then by re-combining the sub-correlations in a novel way, the proposed CBOC correlator not only removes the side-peaks, but also sharpens the correlation peak of the auto-correlation, thus improving the tracking error performance of the CBOC navigation signal.

For detecting the presence of the primary user under malicious attacks in cooperative cognitive radio networks, we propose a detection scheme based on the order statistics and recursive updating algorithm with aging factor. The aging factor not only makes the detector sensitive to the change in the behavior of secondary users but also allows reduction in the storage space. The order statistics help select secondary users with higher degree of reputation for cooperation, and consequently, reduce the influence of malicious users. Computer simulations show the proposed scheme can defend the network against malicious attacks more effectively than the conventional scheme.

Although long pseudo-noise (PN) codes offer highly accurate positioning performance in global navigation satellite systems, their plenty of code phases essentially require a long code phase acquisition time. By splitting the PN code into multiple blocks and stacking the blocks, the folding scans multiple code phases simultaneously, thus reducing the acquisition time significantly. However, the stacking of the split blocks distorts the correlation property of the PN code, thus limiting the use of more folding for faster acquisition. Using the genetic algorithm (GA), in this paper, we design a PN code that is robust to the distortion effect caused by the folding. We first set several randomly generated binary codes as the initial genes, then evaluate the genes by simulating the mean acquisition times (MATs) of the genes. Subsequently, the GA operations including the selection, crossover, and mutation are repeatedly performed to obtain a more evolved gene. In numerical results, it is confirmed that the proposed PN code provides the reductions of 8.3% and 8.0% from the MAT and the normalized mean acquisition error (NMAE) of the conventional PN codes, respectively.

본 논문에서는 가변 샘플러 기반의 합성 이진 옵셋 반송파 (composite binary offset carrier: CBOC) 신호의 추적을 위한 비모호 상관함수 생성 기법을 제안한다. 본 논문에서는 자기상관함수의 샘플링을 통해 대칭의 상호상관함수를 생성하며, 이 때 가변 샘플러는 상호 상관함수의 zero-crossing point의 위치를 변화시켜, 최종적으로 생성되는 비모호 상관함수의 기울기를 조정하는 역할을 한다. 두 상호상관함수와 자기상관함수는 가중결합되어 비모호상관함수를 생성한다. 모의실험 결과, 본 논문을 통해 제안한 상관함수는 기존 상관함수에 비해 더욱 우수한 추적오류 표준 편차 (tracking error standard deviation: TESD) 성능을 제공함을 확인한다.

For radar detection of range-spread targets with unknown Doppler shift, we derive a detector, called the maximization in the reduced space (MRS) detector, based on simplification of the generalized likelihood ratio test. When the knowledge of Doppler frequency is unavailable, it is shown that the MRS detector performs better than the conventional detector.

We address the identification and generation of the discrete-time chaotic system (DTCS) with a two-layered recurrent neural network (RNN). First, we propose an identification procedure of the DTCS in which the RNN is required to have less layers than in the conventional procedures. Next, based on Li–Yorke theorem, we propose a generation procedure which enables us to predict a range of chaotic behavior of the DTCS in advance. Simulation results demonstrate that the proposed identification procedure, employing the Levenberg–Marquardt algorithm and a two-layered RNN, requires lower computational complexity than the conventional identification procedures at comparable performance.

Employing the generalized likelihood ratio test and semidefinite programming (SDP), we derive two detectors, called the SDP and maximization in the reduced space (MRS) detectors for range-spread targets with unknown Doppler shift. It is confirmed that, when knowledge of Doppler frequency is unavailable or imperfect, the proposed detectors perform better than the conventional detector. The MRS detector also outperforms the SDP and conventional detectors in some cases, including when the range-spread target is highly fluctuating.

We propose a cooperative cognitive radio network (CCRN) with secondary users (SUs) employing two simultaneous transmit and receive (STAR) antennas. In the proposed framework of full-duplex (FD) multiple-input-multiple-output (MIMO) CCRN, the region of achievable rate is expanded via FD communication among SUs enabled by the STAR antennas adopted for the SUs. The link capacity of the proposed framework is analyzed theoretically. It is shown through numerical analysis that the proposed FD MIMO-CCRN framework can provide a considerable performance gain over the conventional frameworks of CCRN and MIMO-CCRN.

A novel side-peak elimination scheme is proposed for unambiguous tracking of generic sine-and cosine-phased binary offset carrier (BOC) signal in this paper. In the proposed scheme, the split sub-carrier correlations (SSCs) are combined to cancel out the side-peak components. Since the SSCs are generated by splitting the sub-carrier included in all classes of sine-and cosine-phased BOC signals, the proposed scheme is not only applicable to generic sine-and cosine-phased BOC signals, but also requires no auxiliary signals. The tracking performance improvement is confirmed in numerical results.

Although the folding processor enables the global positioning system (GPS) sensor to directly acquire the correct phase of the received precision code (P code) without any prior information on the phase from auxiliary codes such as the coarse acquisition code, the output of the folding processor essentially involves considerable out-of-phase components as a result of multiple phases being used all together in the folding processor, and consequently, it could result in a poor acquisition performance.Thus, in this study, a novel folding processor is designed to reduce the number of out-of-phase components while maintaining the desirable inphase components, thus achieving a better acquisition performance.In addition, the proposed folding processor does not require the parallel correlator used in the conventional folding processor, thus lowering the complexity in implementation.Numerical results demonstrate that the proposed folding processor provides a significant improvement in acquisition over the conventional folding processor, with a lower complexity in implementation.

Taking the positions of pico-cell base stations (PBSs) into consideration, a scheme of cell range expansion (CRE) for maximum sum rate is addressed in heterogeneous multi-input multi-output multi-user wireless networks. The optimal CRE bias obtained numerically by the proposed CRE scheme with inter-cell interference coordination (ICIC) allows us to maximize the sum rate while successfully maintaining the load balance between the macro-cell base station and PBSs. Numerical results confirm that the proposed CRE scheme with ICIC can provide a higher sum rate than conventional schemes while maintaining balanced load.