Analog m-CAP demodulation for VLC-based IoT systems

Rodrigues, Luís; Figueiredo, Monica; Alves, Luís Nero

doi:10.1109/csndsp49049.2020.9249493

Cited by 4 publications

(3 citation statements)

References 19 publications

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“…Bessel filters were found to be the most suitable for analogue m‐CAP demodulation in Ref. [19], which studied the selection of p ( k ) for hybrid m‐CAP/QAM.…”

Section: System Architecturementioning

confidence: 99%

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Carrier synchronisation in multiband carrierless amplitude and phase modulation for visible light communication‐based IoT systems

Rodrigues

Figueiredo

Alves

et al. 2023

IET Optoelectronics

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The technical feasibility of developing an Internet of Things multi‐user communication system is evaluated based on a central digital multiband carrierless amplitude and phase transmitter, which broadcasts data on multiple channels for a number of low‐cost/low‐power devices. It addresses the issue of carrier synchronisation, which is critical in real‐world implementations because of imperfections of devices and the delays of the system. A simulation model for the traditional Costas Loop is presented, along with performance results, which demonstrate the system's ability to synchronise with pull‐in and lock ranges of ±800 and ±900 Hz, respectively. The loop requires 1.194 ms to be in the locked state, allowing the system to lock within 6 symbols period. In addition, the authors measured the performance of the system in the presence of noise and interference from other modulated bands. The results showed that noise and interference did not degrade the system's performance. Although the system was unable to lock when energy was present in adjacent bands, alternative options such as a high order phase‐locked loop and hybrid frequency‐division multiple access and time‐division multiple access, can improve system performance without significantly increasing the cost and complexity of the devices.

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“…Bessel filters were found to be the most suitable for analogue m‐CAP demodulation in Ref. [19], which studied the selection of p ( k ) for hybrid m‐CAP/QAM.…”

Section: System Architecturementioning

confidence: 99%

“…In Ref. [19], it was proposed that the m‐CAP modulation could accommodate multiple user scenarios without ignoring the cost of implementing digital receivers in IoT devices. The proposed system considered a low cost and low power broadcast architecture with digital modulation for all the users, and analogue‐based homodyne Rx.…”

Section: Introductionmentioning

confidence: 99%

Carrier synchronisation in multiband carrierless amplitude and phase modulation for visible light communication‐based IoT systems

Rodrigues

Figueiredo

Alves

et al. 2023

IET Optoelectronics

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“…A full analog implementation of CAP for optical systems was previously proposed in [ 44 ], making use of analog transversal filters for optical communications. Analog demodulation of a digitally generated m-CAP signal for visible light communications was first presented in [ 45 ]. Commonly found in the literature, the digital m-CAP modulation frequency spectrum lacks guard bands; although the continuous frequency spectrum presents higher spectral bandwidth, it poses severe requirements at the receiver.…”

Section: Introductionmentioning

confidence: 99%

Optimized Analog Multi-Band Carrierless Amplitude and Phase Modulation for Visible Light Communication-Based Internet of Things Systems

Rodrigues

Figueiredo

Alves

2021

Sensors

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This paper presents a multi-user Visible Light Communication (VLC)-based Internet of Things (IoT) system using multi band-Carrierless Amplitude and Phase (m-CAP) modulation for IoT applications. The proposed system uses a digital m-CAP modulator embedded in a ceiling LED light fixture and analog receivers, aiming at low-cost, low-power, and small-sized IoT devices. The performance was evaluated in terms of the filtering stage design and the usage of guard bands. Different pairs of emitter and receiver filters were considered. While Bessel and Butterworth analog filters were tested in the analog receiver, the digital m-CAP modulator pulse shaping filter considered raised cosine filters, as well as digital matched filters for the analog Bessel and Butterworth filters. Regarding the guard bands, two approaches were considered: either by using the raised cosine roll-off factor (bandwidth compression) or by suppressing the even bands. The Bit Error Rate (BER) performance was obtained by simulation. The usage of the Bessel filter in the receiver, along with a digital matched filter, proved to be the best solution, achieving a BER lower than 10−3 for an Eb/No of 6 dB, using a third-order filter. Furthermore, guard bands should be used in order to mitigate inter-band interference in order to have improved performance when multiple users intend to simultaneously communicate.

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