Conference Paper: A Novel Two-Stage Detection Scheme for UWB Signal AcquisitionAbstract: This paper proposes a novel detection scheme based on multiple correlator outputs to enhance the detection performance in ultra-wideband (UWB) signal acquisition. Due to the rich multipath of UWB channels, the signal energy spreads over multiple correlator outputs, which makes each correlator output have only a portion of the signal energy, and thus, degrades the detection performance of the conventional scheme where a single correlator output is used as the decision variable for detection.... Show More
- Abstract: The conventional ultra-wideband (UWB) synchronization schemes could cause poor performance in receiver operations such as demodulation after the synchronization, since unreliable timing information corresponding to low-power multipath components might be transferred to the next stage. To solve this problem, in this paper, we propose novel synchronization schemes for UWB systems. We first derive an optimal scheme based on the maximum likelihood (ML) criterion and then develop a simpler... Show More
Conference Paper: A Rapid Code Acquisition Scheme for Optical CDMA SystemsAbstract: In this paper, we propose a novel code acquisition scheme called modified multiple-shift (MMS) for optical code division multiple access (CDMA) systems. By using the modified local code whose sign is positive or negative, the proposed MMS scheme provides a shorter mean acquisition time (MAT) than the conventional multiple-shift (MS) scheme. The simulation results demonstrate that the MAT of the MMS scheme is shorter than that of the MS scheme in both single-user and multi-user environments.
- Abstract: This paper proposes a novel spectrum sensing technique for the digital video broadcasting-terrestrial (DVB-T) systems, which utilizes the periodicity of pilot signals in the orthogonal frequency division multiplexing (OFDM) symbols. The proposed scheme can overcome the effect of the timing synchronization error by re-correlating the correlation values in the same sample distances. The numerical results demonstrate that the detection probability perfor-mance of the proposed scheme outperforms... Show More
Conference Paper: An asynchronous cooperative transmission schemeAbstract: This paper proposes a novel asynchronous transmission scheme for cooperative wireless networks using Alamouti coded orthogonal frequency division multiplexing (OFDM) modulation. The proposed scheme obviates the need for the timing synchronization at the relay nodes through a renewal of the cyclic prefix (CP) of the OFDM symbol, and achieves a cooperative diversity gain through some simple complex-valued operations at the relay node. Numerical results demonstrate that the bit error rate (BER)... Show More
- Abstract: In this paper, we propose a new periodogram-based integer frequency offset (IFO) estimation scheme robust to the fractional frequency offset (FFO) variation. We first observe the reason why the conventional IFO estimation scheme in is sensitive to the variation of the FFO, and then, propose a new IFO estimation scheme using the modified maximum-likelihood (ML) metric. The numerical results demonstrate that the proposed scheme is more robust to the variation of the FFO and has better IFO... Show More
- Abstract: 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.
- Abstract: 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... Show More
- Abstract: 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.
- Abstract: In this paper, a novel pseudo noise (PN) code acquisition scheme based on sequential estimation is proposed, which can not only achieve code acquisition for both inverted and non-inverted PN codes, but also demodulate the spreading data. Simulation 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.
Publications citing this author (5)
[Show abstract] [Hide abstract] ABSTRACT: Pseudonoise (PN) code acquisition technique based on iterative message passing algorithm (iMPA) has been proposed due to its short acquisition time and low complexity. However, the cyclic and regular nature of constructed tanner graph makes it difficult to achieve promising performance. To address this problem, this correspondence proposes a new message passing algorithm based on adaptive parity check matrix. We find multiple sets of linear sparse constraints for PN sequence by squaring the generator polynomial. The topology of the graphic models as well as the parity check matrix is adapted every a few iterations to avoid local optima. The performance of proposed algorithm is evaluated in terms of detection probability. Simulation results show that this method provides more than 3 dB gains over iMPA with fixed parity check matrix.
- In order to improve the mean acquisition time (MAT) at a bearable hardware complexity, several approaches have been proposed. Since the phase of PN sequence can be determined by the initial state of linear feedback shift register (LFSR), Baek et al.  proposed a type of acquisition method using sequential estimation, where hard chip decisions were made and loaded as initial states of LFSR. This method can effectively reduce the MAT and hardware complexity at high SNR regime.
[Show abstract] [Hide abstract] ABSTRACT: Digital terrestrial television (DTV) covers an area with radius as large as 60 km. Federal Communications Commission (FCC) and Office of Communications (Ofcom) suggests detection of DTV signal at signal strength of as low as −114 dBm and −120 dBm respectively. Thus, detection of DTV signals in low signal-to-noise ratio (SNR) is vital. Continual pilot (CP) positions in all the DTV signals are fixed. Digital Video Broadcasting Terrestrial (DVB-T), a DTV standard, is followed by most of the countries of the world. In this paper we propose a correlation based CP detection which can detect a DVB-T signal at low SNR. One CP carrier was generated at the receiver which was correlated with the received orthogonal frequency division multiplexing (OFDM) signal sequence. The correlation coefficient was then compared with a threshold correlation coefficient to identify the existence of the CP to detect the presence of a DVB-T signal and thereby spectrum hole. It was found from the simulation study for additive white Gaussian noise (AWGN) channel that signal detection at low SNR is possible compared to the time domain symbol cross-correlation (TDSC) method.
- The false alarm rate at the corresponding SNR values is 0.03 which is much below the required false alarm rate of 0.1. Figure 6shows a comparative study of the proposed correlation coefficient based CP detection method to NP based TDSC detection method for AWGN channel (TDSC-NP-AWGN ) in terms of the probability of misdetection. For TDSC method í µí± md = 0.9 at SNR −22 dB.
- College of Information and Communication Engineering (SoICE)