Differential Pulse Position Modulation Research Articles

A 930 m/180 Gbps*User Underwater Coherent Optical Code-Division Multiple-Access Network Based on Hybrid 256-Differential Pulse Position Modulation and Weighted Modified Prime Code Sequence

Currently, there are three types of optical communication networks based on the communication channel between the transmitter and receiver: the optical fiber channel, visible light channel, and optical wireless channel networks. The last type has several advantages for underwater communication, wireless sensors, and military communication networks. However, this type of optical network suffers from weather conditions in free-space communications and attenuation owing to the scattering and absorption mechanisms for underwater communication. In this study, we present a new transceiver architecture of a coherent optical code-division multiple-access (OCDMA) system based on a hybrid M-ary differential pulse position modulation scheme and a spreading code sequence called weighted modified prime code for underwater communication to minimize channel dispersion, increase the transmission rate per second, enhance the network bit error rate (BER) performance, and improve network security. Using an OCDMA system, we can simultaneously expand the network coverage area and increase the number of users sharing the network over the same channel bandwidth. The simulation results in this study proved that the proposed system can accommodate 1310 active users and a network throughput of 180 Gbps*user over a transmission distance of 930 m without any repeater at a 10−9 BER performance, compared to the 45 Gbps*user network throughput and 100 m transmission distance reported in the literature.

Performance analysis toward 880 m/4.255 Gbps underwater optical wireless communication CDMA network based on hybrid M-ary differential pulse position modulation and double length modified prime code

Performance analysis toward 880 m/4.255 Gbps underwater optical wireless communication CDMA network based on hybrid M-ary differential pulse position modulation and double length modified prime code

FPGA-based PPM Modulation System Design

As a widely used modulation technique in the field of communication, PPM modulation techniques have the advantages of high interference immunity, simple coding and high-power utilization, and are often applied in practical scenarios. PPM modulation techniques can be divided into three categories. single pulse position modulation, differential pulse position modulation and multi pulse position modulation. In different application scenarios, different kinds of pulse position modulation methods should be selected for modulation. In this paper, the frame structures of these three types of pulse position modulation are discussed using the Verilog language based on FPGA, the corresponding mapping relationships for each type of pulse position modulation are given, and the design and performance of these three types of pulse position modulation demodulation systems are compared.

Analysis of bit error rate of pulse position modulation in free-space optical communication

Pulse Position Modulation (PPM) modulation is a widely used modulation method in free-space optical (FSO) communication, which has many medium forms. This work introduces and summarises the three main PPM modulation methods, L-ary pulse position modulation (L-PPM), L-ary differential pulse position modulation (L-DPPM), and L-ary multiple pulse position modulation (L-MPPM), and summarises their respective characteristics and suitable usage scenarios. At the same time, this study analyzes several cases of combining coding methods with PPM modulation methods and finds that the right coding method can make PPM modulation methods more valuable. In addition, receiver diversity and/or aperture averaging can both improve the connection error performance.

A Comprehensive Comparison and Analysis of Several Intensity Modulations Based on the Underwater Photon-Counting Communication System

Underwater wireless optical communication is facing absorption, scattering problems, which, in principle, can be greatly resolved by underwater photon-counting communication (UPCC) technology that exhibits high-sensitivity communication characteristics in long-range underwater wireless optical communication. Recent studies on UPCC are mainly focused on a single intensity modulation such as on–off keying (OOK) and pulse position modulation (PPM) technologies, and the comprehensive analysis of communication performance combing OOK modulation and digital pulse modulations remains a lack. To this, by using a UPCC system based on a single-photon avalanche diode, we reveal the communication performances of OOK, PPM, differential pulse interval modulation (DPIM), differential pulse position modulation (DPPM), and dual-header pulse interval modulation, and find that (1) the PPM has the longest transmission distance at the same bit error ratio when M > 2, but the lowest communication rate under identical modulation bandwidth and average transmit power; and (2) the DPPM and DPIM perform the optimum communication performance at the fixed communication rate when M = 8. We thus conclude that the DPPM and DPIM have advantages of low modulation bandwidth and long time slot time compared with PPM, indicating the significance of reducing the difficulty of signal synchronization and the complexity of the underwater photon-counting system accordingly.

Design and implementation of VLC-based smart barrier gate systems

In this paper, an innovative and smart Visible Light Communication (VLC)-based Intelligent Transportation System (ITS) is designed. The proposed system uses vehicle LED headlamps as a remote controller. Differential Pulse Position Modulation (DPPM) is utilized for the sake of its asynchronicity. The system features an innovative optical interference cancellation mechanism to address the unwanted variable DC component and AC line noise in the received signal. The feasibility of the proposed system is demonstrated experimentally in day and night conditions using an off-the-shelf LED headlights. The Bit Error Rate (BER) performance of the system in terms of angular position of the vehicle with respect to the VLC receiver at different link ranges is evaluated. The prototype successfully demonstrates the smart control over the barrier gate using the ATmega microcontrollers family for the outdoor environment. BER of lower than 10-3 is achieved for a maximum link range of 4.4 meters.

Low-Power Wireless Transceiver With 67-nW Differential Pulse-Position Modulation Transmitter

This article presents a low-power wireless narrowband (NB) transceiver consisting of a 434-MHz NB transmitter (NBTX) and a 434-MHz NB receiver (NBRX) implemented in 0.18 $\mu \text{m}$ CMOS. The NBTX utilizes differential pulse-position modulation (DPPM) to decrease consumed energy per bit (EPB) by up to 67% compared to on-off keying (OOK). The packet error performance of DPPM with a soft-decision decoding scheme is analyzed. According to the results, the packet error ratio (PER) does not deteriorate compared to OOK except at very low signal-to-noise levels. The lowest power consumption of the NBTX is 8.3 $\mu \text{W}$ when DPPM data is transmitted continuously. Utilizing packet-mode transmission, the average power consumption is 67 nW at a data rate of 4.8 kbps. The transmitted data was received with a PER of 0.1% by a receiver placed at a 30-meter distance from the NBTX. With a higher power consumption of 2.5 $\mu \text{W}$ at the same data rate, the estimated line-of-sight (LOS) uplink range is up to 200 meters. The NBRX is a mixer-first uncertain-IF receiver. A temperature-compensated ring oscillator (TCRO) is utilized as a local oscillator. Its measured deviation of frequency is from +0.1% to −1.2% over a temperature range from −40 to +85 °C. The NBRX utilizes Manchester encoding and the sensitivity is −87 to −82 dBm over the temperature range at a data rate of 40 kbps. The NBRX consumes 85 $\mu \text{W}$ .

Correcting Insertions/Deletions in DPPM Using Hidden Markov Model

Differential pulse-position modulation (DPPM) shows significant power and bandwidth efficiency, but suffers from serious insertion/deletion and substitution errors if the DPPM soft-decision symbol-by-symbol detection method is used. In this paper, based on the DPPM transmission scheme combining the watermark with the low-density parity-check (LDPC) code, and the equivalent source and channel models, we propose an efficient decoding scheme using hidden Markov model (HMM). Specifically, with the known watermark and the equivalent source and channel models, a hidden markov model is first established to estimate the insertion/deletion errors of the received symbols. Then, a hard-decision forward-backward algorithm is used to recover synchronization and output the estimate of the codeword. Finally, Belief-Propagation (BP) decoding algorithm in the logarithmic domain is performed to correct the residual substitution errors. Simulation results reveal that compared with the decoding scheme using the dynamic programming (DP) and Viterbi algorithms, the proposed decoding scheme has superior performance in correcting insertion, deletion and substitution errors in DPPM transmission.

Error rate performance of differential multi-pulse position modulation

In order to improve the efficiency of the normal pulse position modulation, differential multi-pulse position modulation (DMPPM) scheme is proposed. It has made full use of the advantages of multi-pulse position modulation (MPPM) and differential pulse position modulation (DPPM), and has become one of the most efficient modulation schemes in wireless laser communication. Based on the atmospheric channel affected only by transmission path attenuation and additive Gauss white noise, by analyzing the symbol length, the bandwidth requirement and the peak power of L-level pulse position modulation, MPPM, DPPM and DMPPM, the calculation formula of error rate for various modulation schemes is derived under the optimal demodulation conditions. The simulation results show that DMPPM has advantages on symbol length, bandwidth requirement and peak power. Under the condition of the same signal-to-noise ratio, the error rate of DMPPM is larger. Nevertheless, the error rate performance can be effectively improved by increasing the modulation order or reducing the pulse number.

Influence mechanism of repetition frequency on pulse position modulation in deep space laser communication

Taking the deep space laser communication as the application background, based on multi-pulse position modulation and differential pulse position modulation, a new differential multi-pulse position modulation (DMPPM) mode is proposed. The DMPPM theory model is set up, and a comparative study and analysis of four modulation schemes of PPM, DPPM, MPPM and DMPPM has been developed. The simulation results show that the repetition rate of the pulse laser has a great influence on the four modulation modes. DMPPM has the characteristics of the smallest average symbol length, the largest average transmitting power, the maximum peak transmitting power, the maximum unit transmission rate, the smallest bandwidth demand and a higher transmission efficiency. The analysis shows that DMPPM is greatly influenced by the repetition frequency of the laser. It is very necessary to improve the repetition rate of the laser under the premise of ensuring the peak power of the pulse laser. DMPPM can become one of the excellent modulation schemes for deep space laser communication.

A novel low density parity check coded differential amplitude and pulse position modulation free-space optical system for turbulent channel

Based on the proposed partly equidifferent mapping and its specific Differential Amplitude and Pulse Position Modulation (DAPPM) demodulation, a modified FSO scheme for turbulent channel is designed and analyzed. The novel Low Density Parity Check (LDPC) coded 4×4 and 4×8 DAPPM Free-Space Optical communication (FSO) system is constructed. The Monte Carlo simulation results show approximately 2dB transmit power reduction against classical LD-PC-DAPPM at the identical Bit-Error-Rate in strong turbulent channel. The proposed partly equidifferent mapping is compatible with other modulations, so it enables widespread adoption in other coded FSO systems.

Performance of free space optical communication systems over exponentiated Weibull atmospheric turbulence channel for PPM and its derivatives

In this paper, we have characterized the performance of an intensity modulation/direct detection (IM/DD), free space optical (FSO) communication system in terms of average symbol error rate (SER) over exponentiated Weibull (EW) atmospheric turbulence channel. The system of interest uses on-off keying (OOK) and various pulse position modulation (PPM) schemes. Expressions to assess the SER performance of the modulation techniques under EW atmospheric turbulence channel are derived. Aperture averaging effect on SER performance is also presented. Numerical results are displayed for mentioned modulation techniques and compared graphically under weak, moderate and strong turbulence regime. The simulation results exhibit that for the same peak power, differential amplitude pulse position modulation (DAPPM) provides superior performance than the other modulation schemes considered in this paper.

Real-Time 138-kb/s Transmission Using OLED With 7-kHz Modulation Bandwidth

In this letter, we experimentally demonstrated a visible light communication (VLC) system using an organic light-emitting diode (OLED). Despite using a very simple combination of differential pulse position modulation and comparator, our bit rate to OLED’s 3-dB modulation bandwidth ratio was 19.7 times. Thus, our prototype performed better than most reported VLC with OLED systems employing complex modulation, equalization, and synchronization methods. Moreover, using the asynchronous transmission approach, our prototype was able to provide a stable bit rate of 138 kb/s over a transmission distance of 40 cm, which is four times farther than other similar reports. Last but not least, to the best of our knowledge, our prototype was the first to demonstrate real-time transmission of VLC using OLED at this bit rate and distance.

Hybrid direct-detection differential phase shift keying-multipulse pulse position modulation techniques for optical communication systems

In this paper, a hybrid differential phase shift keying-multipulse pulse position modulation (DPSK–MPPM) technique is proposed in order to enhance the receiver sensitivity of optical communication systems. Both binary and quadrature formats are adopted in the proposed systems. Direct-detection DPSK schemes that are based on an asymmetric Mach–Zehnder interferometer with a novel ultrafast discrete delay unit are presented to simplify the receiver implementation. Expressions for the bit-error rate (BER) of the proposed hybrid modulation techniques are derived taking into account the effect of the optical amplifier noise. Under the constraints of the same transmitted data rate, bandwidth, and average received optical signal-to-noise ratio, the BER performances of the proposed schemes are then evaluated numerically and compared with that of traditional differential binary phase shift keying (DBPSK), differential quadrature phase shift keying (DQPSK), and MPPM schemes and with that of recent hybrid schemes. Furthermore, a comparison between the proposed systems and the traditional ones is held in terms of the bandwidth-utilization efficiency. Our results reveal that the proposed hybrid schemes are more energy-efficient and have higher receiver sensitivity compared with the traditional ones while improving the bandwidth-utilization efficiency. The proposed DPSK–MPPM system is ready to accommodate adjustable (or variable) bit rates, by virtue of the programmable delay integrated to the receiver system.

Efficient modulation technique for optical code division multiple access networks: differential pulse position modulation

In this study, the authors study a fibre-optic local area network deploying optical code division multiple access technique with differential M-ary pulse position modulation (DPPM). The authors present the performance analysis of DPPM signalling using a double optical hardlimiter receiver structure considering the impairment caused by interference of other users. The analysis assumes a set of bit asynchronous transmitters employing generalised optical orthogonal codes for their DPPM signalling (GOOC-DPPM). Using mathematical analysis and simulations, the authors have demonstrated that GOOC-DPPM improves both frame error probability and the maximum achievable network throughput compared with M-ary PPM modulation scheme. It is also indicated that using generalised OOC codes instead of strict OOC codes in DPPM modulation can increase the number of users who can simultaneously transmit data in the network. The authors have analysed the stability of GOOC-DPPM in a multi-user system and demonstrated its stability. Moreover, the performance of the proposed scheme is evaluated when its important design parameters such as code length, code weight and multiplicity index of the modulation are changed. The findings led the authors to provide some guidelines for proper selection of these parameters to be used for efficient system design.

New hybrid reverse differential pulse position width modulation scheme for wireless optical communication

In order to improve the power efficiency and reduce the packet error rate of reverse differential pulse position modulation (RDPPM) for wireless optical communication (WOC), a hybrid reverse differential pulse position width modulation (RDPPWM) scheme is proposed, based on RDPPM and reverse pulse width modulation. Subsequently, the symbol structure of RDPPWM is briefly analyzed, and its performance is compared with that of other modulation schemes in terms of average transmitted power, bandwidth requirement, and packet error rate over ideal additive white Gaussian noise (AWGN) channels. Based on the given model, the simulation results show that the proposed modulation scheme has the advantages of improving the power efficiency and reducing the bandwidth requirement. Moreover, in terms of error probability performance, RDPPWM can achieve a much lower packet error rate than that of RDPPM. For example, at the same received signal power of −28 dBm, the packet error rate of RDPPWM can decrease to 2.6×10−12, while that of RDPPM is 2.2×10−8. Furthermore, RDPPWM does not need symbol synchronization at the receiving end. These considerations make RDPPWM a favorable candidate to select as the modulation scheme in the WOC 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.

Error Probability of DPPM UWB Systems over Nakagami Fading Channels with Receive Diversity

We consider differential-pulse position modulation (DPPM) in an ultra wideband (UWB) communication system. A typical format for a DPPM signal in a UWB system is derived from that of a pulse position modulation (PPM) signal. The error probabilities of a UWB DPPM system with receive diversity over additive white Gaussian noise (AWGN) and Nakagami fading channels are derived. Both single-user and multiuser environments are considered. Performance results are presented which show that the frame error rate (FER) with DPPM is better than that with PPM, and the FER performance can be improved significantly by receive diversity.

Link Energy Minimization in IR-UWB Based Wireless Networks

Impulse Radio Ultra WideBand (IR-UWB) communication has proven to be an important technique for supporting high-rate, short-range, and low-power communication. In this paper, using detailed models of typical IR-UWB transmitter and receiver structures, we model the energy consumption per information bit in a single link of an IR-UWB system, considering packet overhead, retransmissions, and a Nakagami-m fading channel. Using this model, we minimize the energy consumption per information bit by finding the optimum packet length and the optimum number of RAKE fingers at the receiver for different transmission distances, using Differential Phase-shift keying (DBPSK), Differential Pulse-position Modulation (DPPM) and On-off Keying (OOK), with coherent and non-coherent detection. Symbol repetition schemes with hard decision (HD) combining and soft decision (SD) combining are also compared in this paper. Our results show that at very short distances, it is optimum to use large packets, OOK with non-coherent detection, and HD combining, while at longer distances, it is optimum to use small packets, DBPSK with coherent detection, and SD combining. The optimum number of RAKE fingers are also found for given transmission schemes.

Performance of differential pulse-position modulation (DPPM) with concatenated coding over optical wireless communications

The concatenation of marker and Reed–Solomon codes in order to correct insertion/deletion errors in differential pulse-position modulation (DPPM) over optical wireless communications is presented. The concatenated code decoding algorithms with hard-decision and soft-decision detection are presented. The performance of the hard-decision coded DPPM system is evaluated over both nondispersive and dispersive channels via analysis and simulation. It is shown that the coding gain provided by the concatenated code is approximately 4 dB when the code rate is about 0.7 and the channel is nondispersive. Over a dispersive channel, the coded system performs better than the uncoded system when the ratio of delay spread to bit duration is not high. A soft-decision detector is employed to combat intersymbol interference. The soft-decision decoding algorithm, which has low complexity and can be practically implemented, is described. The performance over nondispersive and dispersive channels is evaluated by analysis and simulation. It is shown that the soft-decision system requires approximately 2 dB less transmit power than the hard-decision system for additive white Gaussian noise and low-dispersive channels. Soft decoding also provides a performance improvement in high-dispersive channels.