Digital Pulse Interval Modulation Research Articles

Performance Analysis of Underwater Optical Communication System in Turbulent Link

Underwater wireless optical communication (UWOC) systems have been identified as a suitable replacement technology with high data rates over relatively medium transmission ranges for underwater communication. In the research, we propose a new optical hybrid modulation format for carrying the letters over underwater wireless optical communication (UWOC) system. This hybrid modulation format combines pulse position modulation (PPM) with digital pulse interval modulation (DPIM) to increase the transporting speed. The proposed UWOC system is experimentally investigated in the laboratory over a clean and turbulent water channel. The message was electrically modulated in the transmitter with PPM-DPIM format and then applied to a laser diode. The laser diode emitted light at a wavelength of 650 nm with a power of 60 mW. At the receiver, the photodiode, with its amplifier circuits, sends the received signal to the microprocessor to restore the origin message. The results showed that the received power and signal-to-noise ratio (SNR) decreased with elongating the transmission distance. In addition, the attenuation is raised with increasing distance. The bubbles source is also situated at distances of 25 cm, 50 cm, and 75 cm from the transmitter in turbulent waters. The results showed that locating the bubble source decreases the system's performance. The best results were obtained when the bubble source was 75 cm away from the transmitter. Finally, the hybrid modulation formats (PPM-DPIM) can increase the speed of letter transmission, reduce the bit error rate (BER), and minimize the effect of scattering and attenuation in water channels.

VDIU: VLC-based Debugging Information Upload Method for Self-powered Sensor Nodes

Currently, more and more self-powered sensor nodes have been deployed in remote and inaccessible areas, and thus online debugging of sensor nodes becomes more necessary and important. However, the existing sensor online debugging approaches mainly rely on original network infrastructure (such as Zigbee or NB-IoT). Once the communication infrastructure is invalid, it is almost impossible to retrieve debugging information and repair the lost self-powered sensor nodes. To this end, in our previous study, we employed the onboard optical modules of the self-powered sensor node to realize a Visible Light Communication(VLC)-based hybrid communication debugging system(VHCDS). In this paper, to improve the efficiency of uploading debugging information, we propose VDIU to optimize the digital pulse interval modulation applied in the uplink of VHCDS. This method reasonably groups and sorts the origin data to reduce the number of empty time slots (unused time slots) and complete data compression in source coding for saving energy. To improve the reliability of the uplink, we also design two frame synchronization mechanisms suitable for the receiver-side optical cameras of the uplink. One mechanism considers lightweight synchronization design via restricting the position of the frame header; the other one focuses on reducing the occupation of the downlink of VHCDS via predicting the position of the frame header using a temporal convolutional network (TCN). Experiments results illustrate that the upload efficiency using VDIU is higher 78% and 28% than DPIM and DH-PIM. Both synchronization mechanisms can arrive the similar performance, but the predicting mechanism reduces the 93% occupation on the downlink.

Various transmission codes for the control of bit error rate in both optical wired and wireless communication channels

Abstract This study clarifies the data error rates optimization for OFC/OWC channels based on different transmission codes. These codes that are namely multi bits/symbol digital pulse interval modulation (DPIM), multi bits/symbol pulse position modulation (PPM), nonreturn to zero inverted (NRZI), 4 bit data symbol/5 bit code (4B5B), and Manchester for upgrading optical wired/wireless communication systems. The optical power through OFC/OWC channels, S/N ratio, the output power at the receiver side are stimulated with high bit transmission rates. The effects of coding complexity on the Q-factor, BER, optical power, and electrical received power are also stimulated using both DPIM and PPM coding.

Threshold detection and slot clustering algorithms in DPIM-VLC systems

In this paper it is presented two adaptive threshold estimation methods for Digital Pulse Interval Modulation (DPIM) in Visible Light Communication (VLC) systems. First method, which is called I-DPIMwAL, is proposed for mobile users without Ambient Light (AL) while second scheme that is referred to as I-DPIM ensures to accomplish the mobile data transmission under AL effect. Addition to this, the paper introduces a receiver based on K-means algorithm that classifies the logical levels of DPIM slots without using any threshold value. In order to compare with improved methods, two traditional systems are considered in the simulations. The FP-DPIM, which can be called Full Perfect-DPIM, has the perfect knowledge of threshold value that is determined by using both ambient light level and distance between receiver and transmitter whereas HP-DPIM, which can be defined as Half Perfect-DPIM, uses only one static threshold value for all distances between receiver and transmitter. According to experimental results, it can be considered that AL becomes either square wave or exponential signals. In practical systems, FP-DPIM cannot know the threshold value that is caused by ambient light effect however, it was given to obtain the exact performance analysis in simulation results.

Design and Implementation of Indoor Visible Light Communication System based on High Order PAM

At present, most indoor visible light communication systems use switch keying, pulse position modulation and digital pulse interval modulation. These three modulation methods cannot effectively overcome the inter-symbol interference caused by the multipath effect in the visible light communication system. Compared with the above three modulation methods, high-order pulse amplitude modulation (Pulse Amplitude Modulation, PAM) transmits more bits in the same symbol, which can further improve the modulation efficiency and the communication rate of the system. At a given data rate, the inter-symbol interference caused by multipath effects can be reduced. Using TMS32C6748 floating-point DSP as the control chip of the optical communication system, an indoor visible light communication system based on high-order PAM is designed and implemented. The communication performance of the system is verified by building an experimental platform. The experimental results show that the communication system has the advantages of low bit error rate, high modulation efficiency, and high reliability, and meets the requirements of high-performance indoor visible light communication systems.

AUV Link Mobile Ad-Hoc Network Examination

Wireless optical communication systems allow reliable communication in the ultraviolet (UV) range, and protected from intentional suppression and interception, both in the presence and in the absence of direct visibility between the transmitter and the receiver. Currently, the actual and insufficiently explored direction is the development and research of mobile ad-hoc networks (MANET) with a UV communication channel. To analyze the capacity of a mobile network of UV communications with different spatial orientation of network nodes, it is necessary to take into account not only their coordinates and elevation angles but also azimuths. NLOS UV bandwidth models have been developed using three types of modulation: on-off keying (OOK), pulse-phase modulation (PPM), digital pulse interval modulation (DPIM) with a different number of guard intervals. The noted advantages of DPIM, which are most important for the implementation of a mobile self-organizing network with a UV channel, are: it does not require symbolic synchronization of the transmitter and receiver, it requires a smaller frequency band compared to PPM, it has a higher energy efficiency compared to OOK. A parametric approximation of losses in the NLOS UV channel has been performed, taking into account the azimuthal deviations of the transmitter and receiver for specific parameters of the communication system. Has been done a performance simulation of the MANET network with an ultraviolet communication channel Has been calculated values of the bit error rate (BER), and bit rate for a system with different types of modulation with low, medium, and high noise levels in the channel. With the use of parametric approximation of losses in the channel, are analyzed the BER and the bitrate of the UV communication system with an azimuthal deviation within 30 degrees. Based on the obtained simulation results, prospects for the further development of mobile self-organizing networks with a UV channel are indicated to improve their reliability and performance.

Ordered Sequence Detection and Barrier Signal Design for Digital Pulse Interval Modulation in Optical Wireless Communications

This paper proposes an ordered sequence detection (OSD) for digital pulse interval modulation (DPIM) in optical wireless communications. Leveraging the sparsity of DPIM sequences, OSD shows a comparable performance to the optimal maximum likelihood sequence detection with much lower complexity. Compared with the widely adopted sample-by-sample optimal threshold detection (OTD), it considerably improves the bit-error-rate (BER) performance by mitigating error propagation. Moreover, this paper proposes a barrier signal-aided digital pulse interval modulation (BDPIM), where the last of every $K$ symbols is allocated with more power as an inserted barrier signal. BDPIM with OSD (BDPIM-OSD) can limit the error propagation between two adjacent barriers. To reduce the storing delay when using OSD to detect extremely large packets, we propose BDPIM with a combination of OTD and OSD (BDPIM-OTD-OSD), within which long sequences are cut into pieces and separately detected. Approximate upper bounds of the average BER performance of DPIM-OTD, DPIM-OSD, BDPIM-OSD, and BDPIM-OTD-OSD are analysed. Simulations are conducted to corroborate our analysis. Optimal parameter settings are also investigated in uncoded and coded systems by simulations. Simulation results show that the proposed OSD and BDPIM bring significant improvement in uncoded and coded systems over various channels.

Capacity Analysis of a Peripheral Nerve Using Modulated Compound Action Potential Pulses

Artificial neural stimulation of a peripheral nerve can create an in-body data communications channel. We propose the stimulation of a peripheral nerve using energy-harvesting arrays of nanodevices, embedded in biocompatible tissue patches. The resulting extracellular compound action potential (CAP) pulse can provide a data bit-stream for communicating with an embedded receiver. Our objective is to determine the maximum achievable transmission range of a CAP along a nerve and the maximum sustainable bit rate. We model the generation of a CAP and then compute the reduction in amplitude and the spreading of the pulse with propagation distance. The channel capacity is calculated for ON–OFF keying (OOK) and digital pulse interval modulation. We show that the transmission range depends on the number and diameters of the activated neurons contributing to the CAP amplitude and width. Our modulation analysis demonstrates the effects of attenuation, background noise, the neural refractory period, and pulse broadening on the achievable bit rate. We show how a maximum OOK bit rate of 200 bit/s can be sustained over transmission distances greater than 100 mm. The proposed approach provides a low bit rate, unidirectional asynchronous transmission system that could, for example, deliver simple instructions to an embedded drug-delivery system.

Intersatellite Communication System Based on Visible Light

Future space missions will be driven by factors such as the need for reduced cost of spacecraft without diminished performance, new services, and capabilities including reconfigurability, autonomous operations, target observation with improved resolution and servicing (or proximity) operations. Small satellites, deployed as a sensor network in space, can through intersatellite communication (ISC) enable the realization of these future goals. Developing the communication subsystem that can facilitate ISC within this distributed network of small satellites require a complex range of design tradeoffs. For small satellites, the general design parameters that are to be optimized for ISC are size, mass, and power, as well as cost (SMaP-C). Novel and efficient design techniques for implementing the communication subsystem are crucial for building multiple small satellite networks with capability for achieving significant data-rates along the intersatellite links (ISLs). In this paper, we propose an alternative approach to radio frequency and laser ISLs for ISC among small satellites deployed as a sensor network in low earth orbit. For short to medium range ISLs, we present an LED-based visible light communication (VLC) system that addresses the SMaP constraints, including capability for achieving significant data rates. Our research is focused on the development of the physical layer for pico-/nano class of satellites with prime consideration for the impact of solar background illumination on link performance. We develop an analytical model of the intersatellite link (ISL) in MATLAB and evaluate its feasibility and performance for different intensity modulation and direct detection schemes. Using a transmitted optical power of 4 W and digital pulse interval modulation, a receiver bandwidth requirement of 3.5 MHz is needed to achieve a data rate of 2.0 Mbits/s over a moderate link distance of 0.5 km at a BER of 10−6.

Simulation and Analysis of Power Spectral Density for Digital Pulse Interval Modulation

In free space optical communication the signal power is changing with the bandwidth therefore PSD curves are very important in the link design. The power spectral density(PSD) of intensity modulation scheme i.e. Digital Pulse Interval Modulation (DPIM) has been presented. Results which are generated by simulations of an experimental system are presented. Which shows that DPIM has higher transmission capacity compared with digital pulse position modulation (DPPM) and is less complex to implement

Effect of different weather conditions on BER performance of single-channel free space optical links

This paper studies and compares the performance of on-off keying (OOK), pulse position modulation (PPM), digital pulse interval modulation (DPIM) and dual-header pulse interval modulation (DH-PIM) schemes in FSO channels in the presence of different weather conditions. The bit error rate (BER) curves for these modulations are simulated. Moreover, a performance comparison between these modulation techniques is provided. Generally, in the absence of turbulence OOK-NRZ (non-return-to-zero) and PPM is found to achieve a better BER performance as compared to DPIM and DHPIM. In the presence of fog, OOK-NRZ and PPM is better than DPIM and DH-PIM by approximately 1dB at BER 1e-3. While, in case of rain, OOK-NRZ and PPM is better than DPIM and DH-PIM by approximately 1.5dB at BER 1e-3. Moreover, in case of snow, OOK-NRZ and PPM is better than DPIM and DH-PIM by approximately 1.7dB at BER 1e-3. Additionally, in the presence of turbulence, in case of weak turbulence, OOK-NRZ and PPM is better than DPIM and DH-PIM by approximately 8dB and 10dB, respectively at BER 1e-3. Furthermore, in case of moderate turbulence, OOK-NRZ and PPM is better than DPIM and DH-PIM by approximately 6dB and 8dB, respectively at BER 1e-3. Finally, in case of strong turbulence, OOK-NRZ and PPM is better than DPIM and DH-PIM by approximately 3dB and 4dB, respectively at BER 1e-3.

Comparative Study and Packet Error Rate Analysis of Advance Modulation Schemes for Optical Wireless Communication Networks

The selection of modulation schemes is an essential stage for every communication network. In optical wireless communication, the analysis of modulation schemes is needed to improve the transmitters and receivers to reinforce the received signal energy. In this work, comparative investigation of key attributes of various modulation schemes used in optical communication systems. Conventional schemes, including on off keying and pulse position modulation, are used as reference to analyze the advanced modulation schemes such as digital pulse interval modulation (DPIM)/dual header pulse interval modulation (DH-PIM) in terms of some benchmark parameters such as transmission power, bandwidth requirement, capacity of system, symbol length, packet correction rate and frequency of transmissions and retransmissions. DH-PIM shows the potential benefit of reduced transmission power, minimum bandwidth and shortest possible symbol length while DPIM offers quick transmission rates with least error rates. The overall complexity involved in modulation schemes is also found to be dependent of network types which are being implemented. In this work, recommendations are made based upon the types of network and capacity of information.

Spectral analysis of intensity modulation schemes in free space optical communications

In this study, power spectral densities (PSDs) of intensity modulation schemes used in free space optical communications namely, on-off keying (OOK), pulse-position modulation (PPM), digital pulse interval modulation (DPIM), pulse amplitude and position modulation (PAPM) and differential amplitude pulse interval modulation (DAPIM) have been derived. The bandwidth requirements of these schemes are determined from the occurrence of the first null in the PSDs. For comparison we have considered OOK, 8-PPM, 8-DPIM, 2 × 4-PAPM and 2 × 4-DAPIM. Among all the schemes considered, the bandwidth requirement of 2 × 4-DAPIM is the least. Although 8-PPM has the least effect of baseline wander and the maximum detected optical power among all the schemes considered, the bandwidth requirement is very high. This may not be desirable in certain cases. The PSD curves are quite important in the link design as these will give information on how the signal power is changing with the bandwidth. If the noise PSD is also known then these curves can be used to determine the optimum bandwidth for maximum signal-to-noise ratio. The results are helpful in the selection of modulation scheme for free space optical links and to determine how the power content of the signals is affected by filters and other devices in the link.

Packet error rate analysis of digital pulse interval modulation in intersatellite optical communication systems with diversified wavefront deformation.

Diversified wavefront deformation is an inevitable phenomenon in intersatellite optical communication systems, which will decrease system performance. In this paper, we investigate the description of wavefront deformation and its influence on the packet error rate (PER) of digital pulse interval modulation (DPIM). With the wavelet method, the diversified wavefront deformation can be described by wavelet parameters: coefficient, dilation, and shift factors, where the coefficient factor represents the depth, dilation factor represents the area, and shift factor is for location. Based on this, the relationship between PER and wavelet parameters is analyzed from a theoretical viewpoint. Numerical results illustrate the validity of theoretical analysis: PER increases with the depth and area and decreases if location gets farther from the center of the optical antenna. In addition to describing diversified deformation, the advantage of the wavelet method over Zernike polynomials in computational complexity is shown via numerical example. This work provides a feasible method for the description along with influence analysis of diversified wavefront deformation from a practical viewpoint and will be helpful for designing optical systems.

교란대기 지상 광무선 통신에서 변조방식에 따른 패킷 오류율 비교

지상 광무선 통신에서 대기의 교란 및 대기 입자에 의한 광의 감쇄가 있을 때, 대기교란의 강도 및 가시도가 수신 광 강도에 미치는 영향을 해석하였다. 광신호는 On-Off Keying(OOK), Pulse Position Modulation(PPM) 및 Digital Pulse Interval Modulation(DPIM)의 방식으로 변조하였다. 교란대기 하에서 각 변조방식에 대해 광 전송 거리에 따른 광수신 전력을 계산하고 이를 이용하여 전송거리에 따른 패킷 오류율(packet error rate: PER)을 계산하였다. 광신호를 전송하기 위한 광원의 파장은 850nm, 1310nm 및 1550nm을 선택하였다. 대기는 약 교란 상태로 가정하여 대기 굴절률 구조상수 <TEX>$Cn2{\approx}10-14m-2/3$</TEX>, 대기의 가시도 V=2km로 하였다. 약교란 대기 상태에서 세가지 변조방식 중 DPIM 방식이 우수하며, 광 신호의 전송을 위한 파장으로는 1550nm가 PER 성능이 우수함을 알 수 있었다. In the terrestrial optical wireless communication(OWC), the performance is affected by atmospheric turbulence and particles in the air. The received signal power loss mainly is caused by turbulence and scattering. To minimize the adverse atmospheric effects, the OWC used optical signal modulation, such as OOK, PPM and DPIM. In this paper, the packet error rate(PER) was analyzed above three modulation methods to ground optical link in atmospheric turbulence, scattering and link distance. The OWC system used three wavelengths which are 850nm, 1310nm and 1550nm. I assumed the atmospheric turbulence intensity is weak, so the refractive index is <TEX>$Cn2{\approx}10-14m-2/3$</TEX> and the visibility is 2km. The numerical results shown that the L-DPIM scheme and the wavelength 1550nm are better than other modulation methods and wavelengths.

A new modulation scheme of visible light communication

In order to use white light emitting diode (LED) as a lighting source and communication part, a new modulation scheme called reverse dual header pulse interval modulation (RDH-PIM) is proposed for indoor visible light communications based on the analyses of the structures of on-off keying (OOK), pulse position modulation (PPM), digital pulse interval modulation (DPIM) and dual header pulse interval modulation (DH-PIM). After analyzing and comparing the symbol structure, bandwidth requirement and average transmission power of different modulation methods, the slot error rate is derived. Simulation results show that OOK has the minimum bandwidth, while RDH-PIM has the highest average transmission power and its bandwidth efficiency is obviously better than those of PPM and DPIM. Hence, RDH-PIM is superior in optical wireless communication systems.

Research on Modulations of Wireless Optical Communication System Based on RS Code under Weak Turbulence Atmosphere Channel

The free space optical (FSO) system model is analyzed based on on-off keying (OOK), pulse position modulation (PPM), differential pulse position modulation (DPPM) and digital pulse interval modulation (DPIM) under the weak turbulence atmosphere. To improve the system performance, one effective way is to use forward error correction (FEC).The bit error rate (BER) calculating formula of uncoded system is derived under all above the modulations firstly, then as a benchmark, under the case of independent with identical distribution, the average bit error rates of RS coded system are derived, respectively. Simulations of the average bit error rate performance of these systems are done. Simulation results show that, PPM has the best bit error rate performance, RS coded is efficient to get the code gain and to improve jamming-rejection capability of system.

Adaptive differential amplitude pulse‐position modulation technique for optical wireless communication channels based on fuzzy logic

Optical wireless communication has the potential for extremely high data rates of up to tens of Gb/s. In this study, a hybrid modulation technique named adaptive differential amplitude pulse-position modulation (DAPPM) is proposed to improve channel immunity by utilising optimised modulation to channel. The unit transmission rate, channel capacity, peak-to-average power ratio, bandwidth requirement and power requirement of the DAPPM were determined and compared with other modulation schemes such as on–off key, pulse-amplitude modulation, pulse-position modulation (PPM), differential PPM and multilevel digital pulse interval modulation. The simulation results show that DAPPM gives better bandwidth and power efficiency depending on the number of amplitude level (A) and the maximum length (L) of a symbol. In addition, the fuzzy logic module is developed to assist the adaptation process of DAPPM. Mamdani fuzzy logic method is used in which the decisions made by the system will be approaching to what would be decided by the user in the real world.

Packet error rate analysis of OOK, DPIM, and PPM modulation schemes for ground-to-satellite laser uplink communications

Performance of on-off keying (OOK), digital pulse interval modulation (DPIM), and pulse position modulation (PPM) schemes are researched for ground-to-satellite laser uplink communications. Packet error rates of these modulation systems are compared, with consideration of the combined effect of intensity fluctuation and beam wander. Based on the numerical results, performances of different modulation systems are discussed. Optimum divergence angle and transmitted beam radius of different modulation systems are indicated and the relations of the transmitted laser power to them are analyzed. This work can be helpful for modulation scheme selection and system design in ground-to-satellite laser uplink communications.

Packet error rate analysis of DPIM for free-space optical links with turbulence and pointing errors

In this Letter, we investigate the packet error rate (PER) performance of digital pulse interval modulation (DPIM) for free-space optical (FSO) links under the combined effect of turbulence and pointing errors. The theoretical model is developed by considering the effect of some important parameters, including turbulence condition, beamwidth, receiver aperture size, jitter variance, data rate, transmitted optical power, etc. A closed-form average PER expression for DPIM is derived for this fading channel. The results of numerical simulation are further provided to verify the validation of our model. This work can be helpful for selecting DPIM in the FSO system design.