Role of Walsh Codes and pseudorandom noise sequences in CDMA

Chawla, Puneet; Singh, Balwinder

doi:10.1109/ieem.2014.7058804

Cited by 7 publications

(3 citation statements)

References 4 publications

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“…The dot product between a certain array and another array must be 0. Walsh codes [20] converted from −1 to 0 without the code consisting entirely of 1 satisfy this condition. Therefore, due to the property of Walsh codes, the measurement time must be a power of 2.…”

Section: Basic Ideamentioning

confidence: 99%

“…To solve this problem, we propose a new measurement method for EEM using spread spectrum [19]. In the proposed method, as a modulation step, multiple excitation wavelengths of light are modulated using different orthogonal codes [20] and simultaneously irradiated. Next, the fluorescence intensity is measured and then, as a demodulation step, the detected signal is converted into fluorescence intensity at each excitation wavelength based on the orthogonal codes.…”

Section: Introductionmentioning

confidence: 99%

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Dynamic lighting using spread spectrum technique to eliminate ambient light effects for EEM measurements

Sadamoto,

Nakauchi

2024

Optical Sensing and Detection VIII

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The excitation-emission matrix (EEM) is a three-dimensional scan that investigates the fluorescence intensities at each excitation and emission wavelength combination to provide valuable information. During EEM, it is important to eliminate the effects of ambient light in real environments because it can interfere with the EEM measurements. The conventional method subtracts reflected ambient light intensities from the EEM signals. However, this method removes time-invariant components but not time-varying components. To solve this problem, we propose a novel dynamic lighting using the spread spectrum technique. In the proposed method, multiple wavelengths are modulated according to different orthogonal codes and simultaneously irradiated. The fluorescence intensities are then detected and, subsequently, the EEM is reconstructed based on the orthogonal codes. This proposed method allows us to not only eliminate the time-invariant components but also average the fluorescence intensities to suppress the time-varying components. We performed EEM measurements using a sample of nicotinamide adenine dinucleotide + hydrogen (NADH) irradiated with ambient light with a maximum illuminance of 1000 lx. We measured EEM using both our proposed method and the conventional method. We further calculated the correlation coefficient between the EEM under each ambient light intensity and the EEM measured by the conventional method under the condition of no ambient light as a reference. The results showed that the correlation coefficient of the proposed method was higher than that of the conventional method. Therefore, the proposed method is more effective than the conventional method at suppressing the ambient light effect.

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Section: Basic Ideamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dynamic lighting using spread spectrum technique to eliminate ambient light effects for EEM measurements

Sadamoto,

Nakauchi

2024

Optical Sensing and Detection VIII

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“…Techniques used to generate CDMA codes form wireless systems are modified to work with the optical domain, however, these are not directly applicable. In Samanta et al (2019), optical Walsh-Hadamard (Chawla and Singh 2014) codes is implemented using Mach-Zehnder interferometer (MZI).…”

Section: Related Workmentioning

confidence: 99%

Optical orthogonal code generation scheme and grouping of codes for optical CDMA systems

Chauhan¹,

Kumar

Gautam

2020

Int J Syst Assur Eng Manag

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To exploit the attractive features of CDMA systems and the tremendous bandwidth provided by optical communication such as fiber, VLC, and Li-FI channel, a new system is emerging and is known as optical code division multiple access. These systems require optical orthogonal codes (OOCs). This paper presents an algorithm to design OOCs and determines the auto-correlation (k a ) and cross-correlation (k c ) constrains of codes. The grouping of these OOCs for desired k a and k c is done using a low complexity bipartite method. Design of codes, groups, and simulation for performance analysis in terms of multiple access interference is done using MATLAB programming. The bipartite scheme for grouping finds all possible groups and it reduced the time of computation. The memory requirement of the scheme is also reduced together with computational complexity.

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A fast-sensing readout circuit in 240 Hz enabled by code division multiple access (CDMA) implemented for an ultra-thin on-cell flexible capacitive touch panel

Chang

Chao²,

Wang

et al. 2020

Microsyst Technol

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Role of Walsh Codes and pseudorandom noise sequences in CDMA

Cited by 7 publications

References 4 publications

Dynamic lighting using spread spectrum technique to eliminate ambient light effects for EEM measurements

Dynamic lighting using spread spectrum technique to eliminate ambient light effects for EEM measurements

Optical orthogonal code generation scheme and grouping of codes for optical CDMA systems

A fast-sensing readout circuit in 240 Hz enabled by code division multiple access (CDMA) implemented for an ultra-thin on-cell flexible capacitive touch panel

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