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A Simplified Analog Implementation of Cyclic Shift Chirp Encoding and Decoding for LoRa Communications
(2026-06-01)
Saelim, Nopparut
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Tuwanut, Panwit
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Pornavalai, Chotipat
Currently, LoRa wireless communication technology has become widely adopted in IoT systems due to its long-range capability and low power consumption. However, LoRa is a technology developed by Semtech, which does not disclose the details of the Cyclic Shift Chirp encoding process, a core component of LoRa signals. This lack of transparency prevents users from accessing the physical-layer structure of the signal or freely customizing key parameters such as bandwidth and spreading factor. Although such customization can enhance system flexibility, there is currently no officially disclosed method to achieve it. This research proposes a Cyclic Shift Chirp encoder/decoder circuit built from basic analog components, including adders, subtractors, comparators, and ramp generators, based on a Pulse Width Modulation (PWM) principle. This approach enables researchers and developers to generate LoRa-like signals independently and customize various parameters without introducing limitations. Moreover, the proposed circuit is simple, low-cost, and easy to understand, making it suitable for advanced research, educational experiments, and the design of communication systems that require high flexibility at the LoRa PHY layer.
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Simplified Derivative-Based Carrierless PPM Using VCO and Monostable Multivibrator
(2025-06-01)
Koseeyaporn, Jeerasuda
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Wardkein, Paramote
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Sinchai, Ananta
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Kaew-in, Chanapat
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Tuwanut, Panwit
This study proposes a derivative-based, carrierless pulse position modulation (PPM) scheme utilizing a voltage-controlled oscillator (VCO) and a monostable multivibrator. In contrast to conventional PPM systems that rely on reference carriers or complex demodulation methods, the proposed architecture simplifies signal generation by directly modulating the time derivative of the message signal. The modulated signal, when processed through standard analog demodulators, inherently yields the derivative of the original message. This behavior is first established through theoretical derivations and then confirmed by simulations and circuit-level experiments. The proposed method includes a differentiator feeding into a VCO, followed by a monostable multivibrator to generate a carrierless PPM waveform. Experimental validation confirms that, under all tested demodulation approaches—integrator-based, PLL-based, and quasi-FM—the recovered output aligns with the differentiated message signal. The integration of this output to retrieve the original message was not performed to maintain focus on verifying the modulation principle. Additionally, the study aimed to ensure the consistency of derivative recovery. Signal-to-noise ratio (SNR) expressions for each demodulator type are presented and discussed in the context of their relevance to the proposed system. Limitations and directions for further study are also identified.
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EORL: Energy Optimization via Reinforcement Learning in Software-Defined Wireless Sensor Networks
(2024-01-01)
Boonlert, Arnut
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Pornavalai, Chotipat
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Tuwanut, Panwit
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Tanessakulwattana, Sarayoot
A wireless sensor network is a collection of sensors placed in a particular area to collect and transmit data to the base station or sink. They usually have batteries as the primary power sources. If they work for a long time, their energy will be exhausted. Replacing the battery may not be cost-effective compared to developing an algorithm that optimizes energy efficiency to extend the network lifetime. This work optimizes the energy consumption of wireless sensor networks by adaptively selecting an optimal routing path in a Software-defined Wireless Sensor Networks (SDWSN) environment. A concept of the energy balance among nodes according to the current network status by the SDWSN controller using Reinforcement Learning (RL) is introduced. We propose energy optimization via reinforcement learning (EORL) for SDWSN using a minimum energy reward function and state design that considers energy consumption. The EORL algorithm then identifies the node that requires attention and selects the most energy-efficient path for that node. The performance of the EORL shows that it has a more extended network lifetime compared with other RL solutions.
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Pulse Oximetry Based on Quadrature Multiplexing of the Amplitude Modulated Photoplethysmographic Signals
(2023-07-01)
Koseeyaporn, Jeerasuda
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Wardkein, Paramote
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Sinchai, Ananta
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Kainan, Pattana
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Tuwanut, Panwit
In this research, a pulse oximeter based on quadrature multiplexing of AM-PPG signals is proposed. The oximeter is operated by a microcontroller and employs a simple amplitude modulation technique to mitigate noise interference during SpO<inf>2</inf> measurement. The two AM-PPG signals (RED and IR) are quadrature multiplexed using carrier signals with equal frequencies but a 90-degree phase difference. The study focused on noise interference caused by light intensity and hand movement. The experiment was conducted under three different levels of light intensity: 200 Lux, 950 Lux, and 2200 Lux. For each light intensity level, the SpO<inf>2</inf> level was measured under three scenarios: hand still, shadow movement over the hand, and hand shaking. A comparison between the proposed technique and the conventional method reveals that the proposed technique offers a superior performance. The relative error of the measured SpO<inf>2</inf> level using the proposed technique was less than 3.1% overall. Based on the study, the proposed technique is less affected by noise interference caused by light intensity and hand movement compared to the conventional method. In addition, the proposed technique has an advantage over contemporary methods in terms of computational complexity. Consequently, the proposed technique can be applied to wearable devices that include SpO<inf>2</inf> measurement functionality.
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New pulse oximetry detection based on the light absorbance ratio as determined from amplitude modulation indexes in the time and frequency domains
(2022-05-01)
Kainan, Pattana
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Sinchai, Ananta
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Tuwanut, Panwit
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Wardkein, Paramote
The Pandemic COVID-19 situation, a pulse Oximetry is significant to detect a varying blood oxygen saturation of a patient who needed the device to operate with continuous, rapid, high accuracy, and immune of moving artifacts. In this article, three main schemes for low-complexity pulse oximetry detection are proposed. In the first scheme, the light absorbance ratio (R) is obtained by separating the red and infrared photoplethysmography (PPG) amplitude modulation (AM) signals from the frequency-division multiplexing (FDM) signal with two different bandpass filters (BPFs), determining the ratio of modulation index of red and infrared PPG AM signals. In the second scheme, the output PPG AM signals for the red and infrared light wavelengths from the BPFs are transformed into the frequency domain such that the AC components of both PPG AM signals are the magnitudes of the highest peaks in their respective sidebands, while the DC components are the magnitude of their carrier frequencies; then, the AC/DC ratio of the red PPG AM signal is divided by the AC/DC ratio of the infrared PPG AM signal is R. In the last scheme, the FDM signal is transformed into the frequency domain without being passed through any BPF, and R is obtained in the same way as in the same second scheme. Experimental results obtained by using the first scheme have an average error of about 0.7138%, for the second and the last scheme have an average error of about 1%, and all the methods agree with the corresponding mathematical model.
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Using of an Arithmetic Sequence to Estimate Undetected Existing Circle Choice Locations
(2022-01-01)
Sinchai, Ananta
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Tuwanut, Panwit
Handling an optical mark recognition (OMR) answer sheet faces a problem of shape detection due to defections of color, resolution and shape. A typical method of shape detection thus creates false detection. The false detecting problem is that the general detecting approach fails to detect the locations of the filled shape or detects only the previous detected locations. For this work focuses on a circle choice shape. To solve such problem, an arithmetic sequence is proposed to estimate the existing circle-shaped locations undetected by the common detecting scheme. The proposed technique is verified by experimenting the OMR answer sheet having thirteen options per item. Two conditions are experimented. The first condition arbitrarily fills a circle in each item and the other one leaves the circle in each item unfilled. The experimental results have revealed that the average success rate of the proposed approach in locating the undetected existing circle shapes is 100% for both conditions.
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A Practical Circuit of Cyclic Chirp Spread Spectrum Modulation for Long Range Communication
(2022-01-01)
Sinchai, Ananta
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Saelim, Nopparut
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Pornavalai, Chotipat
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Wardkein, Paramote
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Tuwanut, Panwit
Various technologies have been utilized in long range communication to satisfy increasing usage of the internet of things in a wide large area. Recently, a modulating technique called cyclic chirp spread spectrum (CSS) modulation has attracted attention due to its low power usage and long-range coverage. However, a cyclic CSS circuit is complex to build. Hence, the objective of the work is to propose a practical circuit of cyclic CSS modulation. The proposed circuit is designed to complicated-free creation. To prove that the presented circuit is pragmatic, a simulation test is performed. The simulation results have illustrated that the designed circuit well generates a chirp modulating signal. Also, the proposed circuit is flexibly configurable.
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An Image Resizing Function Embedded in an Inverse Discrete Cosine Transform
(2022-01-01)
Sinchai, Ananta
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Tuwanut, Panwit
Image resizing is an everyday activity and can be done in either a spatial domain or a transform domain. This work realizes that an image is commonly stored in the transform domain and the transformed image must be converted back to the spatial domain to display. This work hence proposes embedding an image resizing function based on a scaled frequency (SF) in a matrix operation of inverse discrete cosine transform (IDCT) for the sake of convenience. By adopting the proposed technique called as the SF-IDCT is not only capable of resizing the transformed image to a given resolution, but also acquiring the IDCT as a by-product. Image data can be shortened or lengthened in proportion to their frequencies by varying the frequencies of the DCT basis functions. Besides, the effects of modifying the pattern of the image data are also studied. The experimental results indicate that the SF-IDCT functions well. The proposed technique reconstructs an upsized image of equal or better visual quality than those produced by existing methods. For a downsized image, the performance of the presented approach is competitive with other available methods.
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A check-in system supporting multiple attendees check-in at a time by proximity-based methods
(2021-05-19)
Sae-Lim, Nopparut
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Sinchai, Ananta
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Yiangsupapaanontr, Nathan
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Tuwanut, Panwit
Every year, tons of events are held. One essential problem of each event is a check-in process. The check-in process wastes plenty of time because each check-in unit is able to check only single participant at a time. Diverse approaches using proximity-based methods have been developed to lessen the check-in processing time. To improve the check-in processing time, these methods are surveyed in this paper. The survey has found that most proximity-based schemes still verify attendees in the same manner but consume lesser time. In addition to the survey, a solution that offers a check-in system that is capable of checking in multiple attendees at a time is proposed. The proposed solution employs beacon technology which is already installed on most mobile devices to provide a unique electronic ticket for each device. With this presented solution, each participant already having the unique electronic ticket on his/her device registered is automatically checked in when walking into an event venue. This significantly helps reduce time consumed in the check-in process.
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A performance evaluation for Internet of Things based on Blockchain technology
(2019-07-01)
Vatcharatiansakul, Nuttakit
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Tuwanut, Panwit
In this paper, the performance evaluation for Internet of Things based on blockchain Technology is proposed. In a blockchain network, all IoT devices communicate and synchronize with each other and allow device to transact with each other directly without the need of trusted intermediary. IoT devices have a smart contract associate with them which are deployed on the blockchain network. User or device who wish to use a service can transact to smart contract that associated with IoT device. Moreover, all transactions of IoT device, device-to device or human-to-device, will not only permanently store on Blockchain network but also gain the security and privacy of them. In this implementation, a private Ethereum network is chosen to use as a blockchain platform and the raspberry pi act as a lightweight node to transact with a smart contract in a full node which install on PC desktop. In addition, the performance evaluation of two realistic traffic flow, store and access transactions, such as latency, execution time and throughput are highlight.

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