A differential spatiotemporal position correlation detection method for underwater moving targets

Ocean turbulence is an important factor affecting the development of underwater wireless optical communication (UWOC). To improve the error characteristics of the underwater optical communication system, we propose a differential detection-based multi-receiver-multi-transmitter (MIMO) underwater laser communication transmission method. Additionally, we derive the expressions for calculating the average BER of the MIMO underwater wireless optical communication system with differential detection and non-differential detection in the case that the two transmitted beams are completely uncorrelated. The error characteristics of the MIMO system are simulated and analyzed from the perspective of ocean turbulence intensity and link distance. The simulation results show that the differential detection method has a lower average BER compared to the non-differential detection method in the case of moderate-to-strong ocean turbulence. In addition, the differential detection methods do not have the error floor effect, and non-differential detection methods have the error floor effect. The more the turbulence intensity affects the average BER of the MIMO UWOC system with the increase of the communication link distance, the more obvious is the effect of the turbulence intensity on the average BER of the MIMO UWOC system. Accordingly, the simulation analysis shows that the differential detection method is more suitable for the construction of communication links under long-distance and medium-strong turbulence.

The multiuser detection is a signal processing tech- nique which enhances the performance and capacity in DS- CDMA technology. Since its complexity issue was too expensive to handle, there was focus on the suboptimal detectors. In this paper we propose a hybrid method called adaptive differential interference cancellation method (ADIC) which is a hybrid of the differential interference cancellation method and which is then combined in a adaptive way to determine a weight matrix which will map the outcome of the differential interference cancellation method to come out with a better performance. This paper also looks into the computational cost of different methods using the floating point operation (flops) which is a good estimation of the comparative computational cost if not the exact one. I. INTRODUCTION The conventional DS-CDMA match filter detector fails to combat these issues due three prominent drawbacks: unrealis- tic ucorrelated code, near-far problem (even with strict power control (1)), and tough multiple access interference (MAI). Many advanced signal processing approaches have been made to improve the performances of these kinds of detectors. In this paper we will study the different approaches that were made in this field and implement these methods to reach a conclusion about the detection methods. As the name of the topic suggests the focus of our work will be study and propose cost effective better performing multiuser detection method. We will explore Multiuser Detection Techniques in Synchronous CDMA environment. Multi-user detection deals with the development and ap- plication of joint demodulation and interference cancellation cancellation techniques for improved detection of a desired set of digital signals in the presence of multiple access interfer- ence, intersymbol interference and noise. Since veterbi forward dynamic algorithm (2) is used in case of Optimum multiuser detection (3) the complexity grows in with the increase in the number of users. Hence the complexity is immense which increases exponentially with the increase in the number of users. Looking ahead for lower complexity hence lesser cost of implementation, the paper proposes the use of sub-optimal linear detectors (4). The sub-optimal detector the paper next focuses on is Decorrelator type of Detector (5) which is optimal in least squares. This detector out performs the optimal detector in many respects. Then the Minimum Mean Square Error (MMSE) linear detector is proposed which tries to minimize the squared error from the required transformation. It is one of the most popular detectors in use due to its easiness to implement and its lower complexity. But then in the above detection methods the decisions made were based on certain linear transformation criterion and there are missing efforts to check the performance in between the detection process to improvise the transformation method better detection. So then the paper proposes Adaptive multiuser detection. Then the paper focuses on Interference cancellation methods which utilize the feedback to reduce Multiple Access Interference (MAI) in the detected bits. Under the Interference Cancellation umbrella the Successive Interference Cancellation (SIC) (6), (7) method is explored and simulated to observe the results. Then the next method which performs better than SIC and more commonly used in real life, called Parallel Interference Cancellation (PIC) (6), (8) is also implemented. Before going ahead to implement the final proposed detection method, this paper implements Differential Interference Cancellation (DIC) (9) method. And then this paper finally proposes an Inter- ference Cancellation method called the Adaptive Differential Interference Cancellation Multiuser Detection method which is cost effective in comparison to other Interference Cancellation methods as we will require lesser hardware (multipliers as in the SIC or Parallel Interference Cancellation (PIC)) for that matter. More ever since we are using adaptive method the desired BER can be further reduced. This proposed method will be discussed in detail in the following section.

An alternative to differential detection in optical data storage is magnetic circular dichroism (MCD) detection. The MCD system has increased light efficiency when compared to the commonly used differential detection method. Also, the signal amplitude for MCD detection can be twice as large as for differential detection when an s-p phase difference of 90° is introduced in the medium. Modeling results show that a thin-film device can introduce the necessary s−p phase difference. Our signal-to-noise analysis indicates that the MCD system rejects polarization noise. Experimental results on coupon samples verify that the signal from MCD detection can be twice as large as from differential detection.

In order to suppress occasional jamming signal and to improve the use of the local oscillator power, a differential detection method is proposed in LDV scheme employing two photodetectors, where the main detector receives the Doppler signal while the auxiliary one detects outside jamming signals. The effectiveness of the method is verified through jamming signal rejection experiment. Theoretical analysis and simulation indicate that the SNR of the system is sacrificed to eliminate jamming signal. The differential detection decreases the SNR of the system since the noise yielding in two differential currents are mutually independent and cannot be eliminated. The jamming signal rejection experiment shows that the differential detection is capable to reduce nearly 90% of the amplitude of the occasional jamming signal, thus improving the measurement accuracy of the Doppler frequency and further improving the velocity measurement precision.

An architecture of decision feedback differential phase detection (DF-DPD) of M-ary DPSK signals is proposed. Conventional differential detection of M-ary DPSK signals uses the phase difference between a current symbol and the previous symbol. This method can make the receiver architecture simple. But it has poorer BER performance than coherent detection because it uses the previous noisy signal as the phase reference. To improve the BER performance of conventional differential detection, multiple symbol differential detection methods, such as maximum likelihood differential detection (ML-DD), Viterbi-DD, decision feedback differential detection (DF-DD), and DF-DPD, using L-1 past detected symbols, have been proposed. As L increases, the BER performance of DF-DPD improves but the complexity of the architecture increases dramatically. Thus, this paper proposes the simplified DF-DPD architecture, replacing the conventional delay and addition architecture with one accumulator. The proposed architecture also has a good BER performance with minimizing the phase error of the current received symbol using the accumulated phase differences of all DPD. The simulation results show that the BER performance of the proposed architecture approaches that of coherent detection.

Although differential detection methods having superior fading resistance and, in general are effective in digital land mobile communications systems, phase shifts due to frequency offsets become a major factor that deteriorates the error rate in these differential detection methods. Although various frequency‐offset compensating methods have been studied and developed, the maximum amount of frequency offset that can be compensated is limited due to the ambiguity of the phase, which has become a problem in estimating the phase shift due to a frequency offset.In this paper, a method for compensating frequency offset by double differential encoding of transmission data sequences, which allows a resolution of the forementioned problem even when a large frequency offset occurs, is proposed and the error rate performance in the application of a /4‐shift QPSK scheme is evaluated by computer simulation. As a result, it is shown that the proposed method has superior compensating performance on land mobile communications channels.

This paper describes refractive index measurements for verifying a novel optical cavity based sensor using a differential detection method. Two low cost laser diodes at the wavelengths of 780 nm and 850 nm are used. The optical cavity is created by a SU-8 to SU-8 bonding of two silver sputtered glass substrates. The intensities of two lasers are measured by an sCMOS camera after the cavity is filled with a refractive index of fluid. We employed a differential detection method which calculates differential values using measured intensities in order to enhance sensitivity. Combined with the noise analysis, the limit of detection of refractive index is estimated to be 6.944 × 10−6 R.I.U.

Multi-group cancer outlier differential gene expression detection

In an optical disk system which uses a short wavelength laser diode and a high numerical aperture objective lens, it is necessary to detect and compensate for the disk tilt, because the coma aberration deteriorates the read/write characteristics and the tilt margin becomes narrower. This paper presents a new radial and tangential tilt detection method for rewritable optical disks, which is based on the intensity distribution of the reflected light from the disk. This method features high sensitivity (about 0.37/° for radial direction and about 0.51/° for tangential direction) and is suitable for high-frequency servo operation. Moreover, it can be combined with the differential push-pull detection method and the land/groove detection method by using three beams. Experimental results have demonstrated the validity of this method.

The methods of image edge detection based on the differential, wavelet transform and image morphology are introduced in the paper. Differential operator edge detection method is based on the edge of the adjacent regions' boundary that is not continuous with the gray, using derivative to detect the edge, Wavelet transform edge detection is by means of selecting the appropriate wavelet function to make wavelet detail component to truely reflect the image of the local gray mutations point, The basic idea of mathematical morphology is to use some forms of structural elements to measure and extract the corresponding shape of the image to attain the objective of image analysis and recognition.

We report the real-time and label-free detection of direct disaccharide binding to a lectin using a differential surface plasmon resonance detection method that allows for measurement of nanomolar concentrations of disaccharides.

A low-energy inductive coupling transceiver is proposed for Cm-range multimedia data transmission in mobile device applications. The Transmission Time Control (TTC) scheme is proposed to reduce the transmitter energy consumption to 0.475 pJ/b, and the Adaptive Gain Control (AGC) scheme is adopted to make the receiver energy consumption be 0.825 pJ/b. The planar-type inductor with self-resonance frequency of about 200 MHz fabricated on the flexible substrate achieves a data rate over 50 Mbps. To compensate for the weakly coupled channel, the receiver sensitivity is enhanced by the differential detection method (DDM) of the nodal voltages across the receiver inductor. With this method, the communication distance is increased up to 7 cm, and channel misalignment tolerance is enhanced up to 2 cm. The proposed transceiver is implemented within 1.5 × 2.37 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> in 0.18-μ m CMOS process and operates with 1-V supply.

High-sensitivity dynamic analysis of dissolved gas in oil based on differential photoacoustic cell

We report an optical cavity based biosensor using a novel differential detection method for point-of-care applications. Two laser diodes allow for multiplexing capability along with the ability to enhance the responsivity using differential detection. The laser wavelengths are chosen so that the optical intensities of two lasers change monotonically with opposite slopes upon the adsorption of desired biomarkers. The cavity width, PMMA thickness, and silver thickness have been optimized to achieve a large change in scaled differential value. We chose biotinylated BSA detection with Avidin as a receptor molecule to demonstrate the proposed design. Avidin is attached directly to the PMMA layer by physisorption. Then, biotinylated BSA is introduced to the sample and the intensities of the laser diodes are measured by a sCMOS camera. A change in the scaled differential value will correlate to the binding of biotinylated BSA. In this presentation, we will discuss simulation results, fabrication procedures, and preliminary measurement results.

The sub-land/sub-pit affects the characteristic of the tracking error signal which is generated by the conventional differential phase detection (DPD) method in the signal waveform modulation multi-level (SWML) read-only disc. To solve this problem, this paper proposes a new tracking error detection method using amplitude difference. Based on the diffraction theory, the amplitude difference is proportional to the tracking error and is feasible to be used for obtaining the off-track information. The experimental system of the amplitude difference detection method is developed. The experimental results show that the tracking error signal derived from the new method has better performance in uniformity and signal-to-noise ratio than that derived from the conventional DPD method in the SWML read-only disc.