Showing papers on "Pulse-position modulation published in 2016"
TL;DR: The performance of OFDM-IM is studied in terms of the achievable rate assuming an M-ary constellation and that channel state information is available at the receiver, and an interleaved grouping method is proposed for the use of subcarriers.
Abstract: Orthogonal frequency division multiplexing with index modulation (OFDM-IM) is a recently developed transmission technique that extends the principle of spatial modulation to OFDM subcarriers. In this paper, the performance of OFDM-IM is studied in terms of the achievable rate assuming an $M$ -ary constellation and that channel state information is available at the receiver. A closed-form lower bound is derived, based on which an interleaved grouping method is proposed for the use of subcarriers. In comparison with the existing grouping method, the proposed one can better benefit from the diversity effects over frequency-selective fading channels, especially when the spacing of any two subcarriers within a subcarrier group is larger than the coherence bandwidth. Through numerical results, it is revealed that OFDM-IM with interleaved grouping outperforms classical OFDM for small $M$ and certain ranges of signal-to-noise ratio. Finally, the effects of modulation types on the performance of OFDM-IM are studied. It is found that the superiority of OFDM-IM over classical OFDM is greater for phase-shift keying than for quadrature amplitude modulation.
241 citations
17 Nov 2016
TL;DR: This research explores an alternative approach of implementing an in-band, mixed-modulated waveform that combines surveillance radar and communication functions into a single signal and uses reduced phase-angle binary phase shift keying (BPSK) along with overlapped (channelized) spread-spectrum phase discretes based on pseudorandom noise sequences to encode multiple messages in a single pulse.
Abstract: As electromagnetic spectrum availability shrinks, there is growing interest in combining multiple functions, such as radar and communications signals, into a single multipurpose waveform. Historically mixed-modulation has used orthogonal separation of different message signals in different dimensions such as time or frequency. This research explores an alternative approach of implementing an in-band, mixed-modulated waveform that combines surveillance radar and communication functions into a single signal. The contribution of this research is the use of reduced phase-angle binary phase shift keying (BPSK) along with overlapped (channelized) spread-spectrum phase discretes based on pseudorandom noise sequences to encode multiple messages in a single pulse. The resulting mixed-modualted signal provides a low data rate communications message while minimizing the effect on radar performance. For the purpose of this research, radar performance will be evaluated in terms of power spectral density, matched filter auto-correlation for target detection, and the ambiguity function.
98 citations
TL;DR: The NODE project as mentioned in this paper implements a free-space optical communications (lasercom) capability on a CubeSat platform that can support low earth orbit (LEO) to ground downlink rates>10 Mbps.
Abstract: The nanosatellite optical downlink experiment (NODE) implements a free-space optical communications (lasercom) capability on a CubeSat platform that can support low earth orbit (LEO) to ground downlink rates>10 Mbps. A primary goal of NODE is to leverage commercially available technologies to provide a scalable and cost-effective alternative to radio-frequency-based communications. The NODE transmitter uses a 200-mW 1550-nm master-oscillator power-amplifier design using power-efficient M-ary pulse position modulation. To facilitate pointing the 0.12-deg downlink beam, NODE augments spacecraft body pointing with a microelectromechanical fast steering mirror (FSM) and uses an 850-nm uplink beacon to an onboard CCD camera. The 30-cm aperture ground telescope uses an infrared camera and FSM for tracking to an avalanche photodiode detector-based receiver. Here, we describe our approach to transition prototype transmitter and receiver designs to a full end-to-end CubeSat-scale system. This includes link budget refinement, drive electronics miniaturization, packaging reduction, improvements to pointing and attitude estimation, implementation of modulation, coding, and interleaving, and ground station receiver design. We capture trades and technology development needs and outline plans for integrated system ground testing.
42 citations
01 Sep 2016
TL;DR: The approach to transition prototype transmitter and receiver designs to a full end-to-end CubeSat-scale system is described, which includes link budget refinement, drive electronics miniaturization, packaging reduction, improvements to pointing and attitude estimation, implementation of modulation, coding, and interleaving, and ground station receiver design.
Abstract: The nanosatellite optical downlink experiment (NODE) implements a free-space optical communications (lasercom) capability on a CubeSat platform that can support low earth orbit (LEO) to ground downlink rates>10 Mbps. A primary goal of NODE is to leverage commercially available technologies to provide a scalable and cost-effective alternative to radio-frequency-based communications. The NODE transmitter uses a 200-mW 1550-nm master-oscillator power-amplifier design using power-efficient M-ary pulse position modulation. To facilitate pointing the 0.12-deg downlink beam, NODE augments spacecraft body pointing with a microelectromechanical fast steering mirror (FSM) and uses an 850-nm uplink beacon to an onboard CCD camera. The 30-cm aperture ground telescope uses an infrared camera and FSM for tracking to an avalanche photodiode detector-based receiver. Here, we describe our approach to transition prototype transmitter and receiver designs to a full end-to-end CubeSat-scale system. This includes link budget refinement, drive electronics miniaturization, packaging reduction, improvements to pointing and attitude estimation, implementation of modulation, coding, and interleaving, and ground station receiver design. We capture trades and technology development needs and outline plans for integrated system ground testing.
40 citations
20 Mar 2016
TL;DR: Enhanced modulation formats optimized for nonlinear performance over a range of spectral efficiency are presented, improving transmission distance and maximum transmission distance.
Abstract: We present enhanced modulation formats optimized for nonlinear performance over a range of spectral efficiency. Maximum transmission distance is improved by > 600 km at PM-8QAM capacity and by > 3500 km at PM-BPSK rates.
40 citations
TL;DR: A novel three-stage DSP algorithm is proposed that exhibits equal BER performance, while significantly reducing the total required number of real additions and real multiplications and tracking the state of polarization using the proposed method is m -times more efficient.
Abstract: We study and compare two digital signal processing (DSP) approaches to recover the intensity on two orthogonal polarizations and the interpolarization phase modulation using a Stokes-vector direct detection receiver. We focus on higher order modulation of each of the three degrees of freedom allowed in Stokes-vector detection. 2 bits are encoded on each intensity of the two orthogonal polarizations, and 2 bits are encoded in the phase difference between the two polarizations, giving a 6 bits per symbol format. In this study, we propose a novel three-stage DSP algorithm and we compare this new algorithm with our earlier two-stage algorithm using the following metrics: the computational complexity and the bit error rate (BER) performance. Using the three stage approach, waveform filtering and derotation are applied in series rather than in parallel as was done in the two stage algorithm. We show that the three-stage approach exhibits equal BER performance, while significantly reducing the total required number of real additions and real multiplications. Moreover, tracking the state of polarization using the proposed method is m -times more efficient, where m is the number of taps in the first filtering stage.
37 citations
TL;DR: Ti me-line m odulation (TiM), a novel three-Dimensional modulation scheme by adding time dimension into current amplitude-phase domain schemes, is proposed, which can improve channel utilization up to 200 percent and is implemented on USRP2 and conducted comprehensive simulations.
Abstract: Channel condition varies frequently in wireless networks. To achieve good performance, devices need rate adaptation. In rate adaptation, choosing proper modulation schemes based on channel conditions is vital to the transmission performance. However, due to the natural character of discrete modulation types and continuous varied link conditions, we cannot make a one-to-one mapping from modulation schemes to channel conditions. This matching gap causes either over-select or under-select modulation schemes which limits throughput performance. To fill-in the gap, we propose ti me-line m odulation (TiM), a novel three-Dimensional modulation scheme by adding time dimension into current amplitude-phase domain schemes. With estimation of channel condition, TiM changes base-band data transmission time by artificially interpolating values between original data points without changing amplitude-phase domain modulation type. We implemented TiM on USRP2 and conducted comprehensive simulations. Results show that, compared with rate adaptation choosing from traditional modulation schemes, TiM can improve channel utilization up to 200 percent.
37 citations
NATO1
TL;DR: In this paper, a decision tree is trained to associate channels with modulation schemes under a target bit error rate (BER) and all relevant channel characteristics (e.g., multipath spread, Doppler spread and signal-to-noise ratio).
Abstract: Underwater acoustic channels are characterised by non-stationary fading statistics and consequently, a modulation scheme optimally designed for a specific fading model will underperform when the channel statistics change. This issue can be alleviated by using adaptive modulation, i.e., the matching of the modulation scheme to the conditions of the acoustic link. However, selecting signals from a broad range of bit rates is tedious because one needs to know the relationship between the bit error rate (BER) and all relevant channel characteristics (e.g., multipath spread, Doppler spread and signal-to-noise ratio). In this work, this relationship is extracted from large amounts of transmissions of a phase-shift keying (PSK) single-carrier modem. In particular, a decision tree is trained to associate channels with modulation schemes under a target BER. The effectiveness of the proposed tree method is demonstrated by post-processing data from two experimental links off the coast of Faial Island, Azores, Portugal.
34 citations
TL;DR: By evaluating the performances of the proposed VLC systems, it is demonstrated that the OSM-aided system is capable of achieving high data rates at sufficiently high signal-to-noise ratios (SNRs) and the SPPM- aided system has a higher effective bandwidth efficiency at low SNRs, despite the fact that its attainable peak data rate is lower than that of the SM-aiding counterpart.
Abstract: In this paper, we propose a multiuser precoded visible light communication (VLC) system utilizing optical orthogonal frequency division multiplexing (OFDM), where optical spatial modulation (OSM) and spatial pulse position modulation (SPPM) are invoked for supporting high-rate data transmissions without compromising uniform illumination across multiple light-emitting diodes (LEDs). Both OSM and SPPM exploit the index of data streams for carrying additional information bits, whereas the multiuser interference occurring between different user equipments is mitigated by the MIMO precoder. By evaluating the performances of the proposed VLC systems, we demonstrate that the OSM-aided system is capable of achieving high data rates at sufficiently high signal-to-noise ratios (SNRs). In contrast, the SPPM-aided system has a higher effective bandwidth efficiency at low SNRs, despite the fact that its attainable peak data rate is lower than that of the SM-aided counterpart. Such tradeoffs indicate the potential application scenarios of the proposed schemes for achieving diverse design prerequisites.
29 citations
TL;DR: In this paper, an amplifierless IM/DD link at the 2-μm spectral band was demonstrated with pulse amplitude modulation (PAM) and 3-D carrierless amplitude and phase modulation (3-D-CAP).
Abstract: Advanced modulation formats with intensity modulation and direct detection (IM/DD) have shown promise in a short-reach optical communication system like data center interconnect. However, the conventional fiber transmission spectral window is mostly located at 850, 1310, and 1550 nm. Here, we experimentally demonstrated an amplifierless IM/DD link at the 2-μm spectral band. The signal is encoded with pulse amplitude modulation (PAM) and 3-D carrier-less amplitude and phase modulation (3-D-CAP). The encoded signal is transmitted through a 100 m-long solid-core fiber designed for single mode at 2-μm. We achieve a transmission with bit-rate of 40 Gbit/s using PAM-4 and 24 Gbit/s using CAP16. The measured bit error rates of both formats are below the forward error correction (FEC) limit of $3.8\times 10^{-3}$ . This study is the first demonstration of PAM4 and CAP transmission at 2-μm, and the results show a significant potential of advanced modulation for 2-μm optical communication.
27 citations
TL;DR: A new BTS-MAP rule is proposed based on the traditional 2-D Gray mapping rule, which increases the Hamming distance (HD) between the symbol pairs detected from the same transmit antenna (TA) and simultaneously reduces the average HD between the symbols pairs gleaned from different TAs.
Abstract: In spatial modulation (SM), the information bit stream is divided into two different sets: the transmit antenna index bits (TA-bits) and the amplitude and phase modulation bits (APM-bits). However, the conventional bit-to-symbol mapping (BTS-MAP) scheme maps the APM-bits and the TA-bits independently. For exploiting their joint benefits, we propose a new BTS-MAP rule based on the traditional 2-D Gray mapping rule, which increases the Hamming distance (HD) between the symbol pairs detected from the same transmit antenna (TA) and simultaneously reduces the average HD between the symbol pairs gleaned from different TAs. Based on the analysis of the distribution of minimum Euclidean distance (MED) of SM constellations, we propose a criterion for the construction of a meritorious BTS-MAP for a specific SM setup, with no need for additional feedback links or extra computational complexity. Finally, Monte Carlo simulations are conducted for confirming the accuracy of our analysis.
20 Mar 2016
TL;DR: Real-time transmission with 26-GBaud PAM-4 as a promising modulation format for data-center interconnects with operation in C-band with dispersion tolerance of up to 10 km of SSMF is evaluated.
Abstract: Real-time transmission with 26-GBaud PAM-4 as a promising modulation format for data-center interconnects with operation in C-band is evaluated. For an OSNR penalty below 2 dB a dispersion tolerance of up to 10 km of SSMF is achieved.
TL;DR: In this article, the error performance of a free space optical (FSO) downlink from a geostationary earth orbit satellite to an earth station in presence of turbulence and different weather conditions such as fog, clouds, etc.
Abstract: We evaluate the error performance of a free space optical (FSO) downlink from a geostationary earth orbit satellite to an earth station in presence of turbulence and different weather conditions such as fog, clouds, etc. Combined channel state probability density function (pdf) is derived by using log-normal model for weak turbulence, gamma–gamma model for moderate to strong turbulence and Beer–Lambert Law for weather effects. Bit error rate (BER) expressions are derived using the combined channel state pdf for on-off keying (OOK), M-ary pulse position modulation (M-PPM) and M-ary differential PPM (M-DPPM) schemes. It is observed that the link performance degrades with increase in the strength of ground level turbulence. Presence of weather conditions causes additional degradation with moderate fog causing the worst effect followed by light and thin fog with respect to clear air condition. Dense or thick fog and/or clouds may lead to complete link failure owing to their large attenuation coefficient. Further, enhancement in the link performance by using aperture averaging and receiver diversity techniques is examined and compared for all three schemes. It is seen that performance improves with increase in the receiver diameter and number of multiple independent receivers. Among the three modulation schemes, link with M-PPM scheme gives the best performance in terms of BER followed by M-DPPM and OOK schemes with or without diversity techniques. Thus, an M-PPM based FSO downlink with an array of finite sized receivers i.e., single input multiple output link can be a viable alternative for efficient data transfer in presence of atmospheric turbulence and different weather conditions from a satellite to an earth station.
05 Jul 2016
TL;DR: The GaN power device is used to replace the traditional silicon power device of switching LED driver in this paper for the purpose of increasing switching frequency of converter, and then the bandwidth of data transmission can be increased as well.
Abstract: This paper presents a LED driver for visible light communication (VLC) application, and the main purpose is to solve the low data rate problem used to be in switching type LED driver. The GaN power device is used to replace the traditional silicon power device of switching LED driver in this paper for the purpose of increasing switching frequency of converter, and then the bandwidth of data transmission can be increased as well. Also, for the purpose of high efficiency, the diode-connected GaN power transistor is utilized to replace the traditional ultrafast recovery diode used to be in switching type LED driver. The proposed LED driver is experimentally evaluated on 350mA output current, and it supports the data of pulse width modulation (PWM) dimming level encoded in pulse position modulation (PPM) scheme for VLC application. The experimental results show that the system's efficiency of 80.8% is achieved with 1Mb/s data rate.
16 May 2016
TL;DR: This paper presents a thorough study of OFDM-IM and FQAM schemes and conducts a comparison between them and the classic OFDM system, capitalizing on recent results from the literature.
Abstract: Recently, orthogonal frequency division multiplexing (OFDM) with index modulation (OFDM-IM) as well as frequency and quadrature amplitude modulation (FQAM) have been proven to be promising techniques for the multicarrier transmission over frequency selective fading channels by successfully mitigating the induced interference due to multipath, while at the same time boosting the overall spectral efficiency. In this paper, we present a thorough study of OFDM-IM and FQAM schemes and conduct a comparison between them and the classic OFDM system. Different configurations are considered and evaluated in terms of their spectral efficiency and error performance, capitalizing on recent results from the literature.
20 Mar 2016
TL;DR: Pareto-efficient pairs of modulation and coding are identified to achieve both higher spectral efficiency and higher nonlinearity tolerance in nonlinear fiber transmissions.
Abstract: We compare various modulation formats and variable-rate LDPC codes based on required GMI in nonlinear fiber transmissions. Pareto-efficient pairs of modulation and coding are identified to achieve both higher spectral efficiency and higher nonlinearity tolerance.
01 Oct 2016
TL;DR: This work exclusively deals with the designing of FSO systems using the simulation software Opti-system 13.0 with Amplitude Shift Keying and Pulse Position Modulation techniques, and a comparative study has been made as to which modulation technique provides better means of communication.
Abstract: The Free Space Optics (FSO) proves to be a very effective and efficient technology for wireless communication. This emerging field basically uses invisible beams of light such as ultraviolet, infrared, etc. in order to provide optical bandwidth connections providing a high data rate than other technologies. This work exclusively deals with the designing of FSO systems using the simulation software Opti-system 13.0 with Amplitude Shift Keying and Pulse Position Modulation techniques. Further their comparative study has been made as to which modulation technique provides better means of communication. The work extends to the performance analysis of FSO systems by varying different FSO parameters due to several conditions for different atmospheric turbulences including rain, fog, haze, etc. Finally the simulation results are obtained, analyzed and further discussed.
TL;DR: In this article, a hybrid fiber and free-space optical communication link using digital pulse-position modulation (DPPM) in a wavelength-division-multiplexing system is proposed and the results are presented in the form of bit error probability, required optical transmission power and power penalties.
Abstract: A hybrid fibre and free-space optical communication link using digital pulse-position modulation (DPPM) in a wavelength-division-multiplexing system is proposed. Such a system, which could provide a power efficient, robust and flexible solution to high-speed access networks, is a contender for a passive optical network solution and could readily be deployed in areas with restrictions in optical fibre installation, or alternatively as a disaster recovery network. Interchannel crosstalk and atmospheric turbulence are major impairments in such a system and could combine in some cases to degrade the system. Both impairments are investigated here and the results are presented in the form of bit error probability, required optical transmission power and power penalties. Depending on the position of the interferer relative to the desired user, power penalties of about 0.2–3.0 dB for weak turbulence and above 20 dB for strong turbulence regimes are reported for bit error rate of 10−6. DPPM scheme with a coding level of 2 show about 2 dB improvements over on–off-keying scheme.
01 Sep 2016
TL;DR: GSPPM is compared with some of the existing spatial modulation techniques, and results show that GSPPM provides an attractive trade-off between energy and spectral efficiency.
Abstract: In this paper, we investigate the performance of a spatial modulation scheme that combines the energy efficiency of pulse position modulation (PPM) with the spectral efficiency of generalized space shift keying (GSSK) for optical wireless communication system. The combined scheme is called generalized spatial pulse position modulation (GSPPM). We present the error performance analysis and validate the results through simulation. Error performance results show that the upper bound derived in the theoretical analysis is tight for all cases when the symbol error rate is below 0.1. The influence of parameters such as channel path gain and number of PPM slots on GSPPM's performance is illustrated. GSPPM is compared with some of the existing spatial modulation techniques, and results show that GSPPM provides an attractive trade-off between energy and spectral efficiency.
TL;DR: It is demonstrated that WiFi OFDM back-channel communication is feasible in various modulation formats, such as pulse position modulation, pulse phase shift keying, or frequency shift keied, and Comprehensive bit error rate performance analysis of various WiFi back-Channel communication schemes is derived and validated in realistic multi-path frequency selective fading channels.
Abstract: This paper presents innovative back-channel wireless communication techniques for ultra-low power (ULP) devices. The concept of embedded back-channel communication is proposed to enable a variety of new applications by inter-connecting heterogeneous ULP devices through existing orthogonal frequency division multiplexing (OFDM)-based WiFi (IEEE 802.11a/g/n/ac) networks. The proposed back-channel communication allows ULP devices to decode messages embedded in WiFi OFDM packets even if these ULP devices are incapable of demodulating OFDM. The proposed back-channel signaling has unique properties that are easily detectable by non-WiFi ULP receivers consuming sub- $mW$ of active power. The proposed scheme eliminates the need for specialized transmitter hardware or dedicated channel resources for embedded back-channel signal transmission. Instead, carefully sequenced data bit streams will generate back-channel messages from already-deployed WiFi infrastructure without any hardware modification. This paper demonstrates that WiFi OFDM back-channel communication is feasible in various modulation formats, such as pulse position modulation, pulse phase shift keying, or frequency shift keying. Systematic algorithms are unveiled to create back-channel messages in various modulation formats from a WiFi standard compliant datapath. Comprehensive bit error rate performance analysis of various WiFi back-channel communication schemes is derived and validated in realistic multi-path frequency selective fading channels.
01 Oct 2016
TL;DR: Simulation results show that the proposed spatial modulation systems with frequency and quadrature amplitude modulation (FQAM)/frequency and phase shift keying (FPSK) achieves significantly better bit error performance (BER) than traditional SM system and FQAM/FPSk system using maximum likelihood (ML) detector.
Abstract: Spatial Modulation (SM) is a recently developed transmit technique, and it has attracted wide interests for it gains higher transmit rate than single-input-single-output (SISO) system and provides simpler transceiver structure and lower power consumption compared with traditional MIMO system. In this paper, we propose the spatial modulation systems with frequency and quadrature amplitude modulation (FQAM)/frequency and phase shift keying (FPSK), which combine frequency shift keying (FSK) and quadrature amplitude modulation (QAM)/phase shift keying (PSK). Simulation results show that the proposed scheme (i.e. FQAM/FPSK-SM) achieves significantly better bit error performance (BER) than traditional SM system and FQAM/FPSK system using maximum likelihood (ML) detector, and it can assign information flexibly among the constellation modulation, the index of the active antenna and the index of the active frequency. We also compare and analyze system performance and complexity of optimal detector and sub-optimal detector.
TL;DR: In this paper, an effective RLL line coding scheme is proposed in order to enhance the brightness and BER performance as compared with conventional RLL coding schemes in IEEE 802.15.7 VLC standard.
Abstract: In visible light communication (VLC), on–off keying (OOK) is able to achieve the best BER performance as compared with variable pulse position modulation. However, OOK has a significant defect that the dimming levels (i.e. brightness) of illumination are greatly affected by the input ratio of 0 and 1 bits. To overcome this drawback, OOK with run length limited (RLL) line codes such as Manchester code or 8B10B block code has been studied in IEEE 802.15.7 VLC standard. However, those mechanisms cannot support the dimming levels more than 50%. Also, spectral efficiency of those mechanisms is reduced and then it is causative of BER performance degradation. An effective RLL line coding scheme is proposed in order to enhance the brightness and BER performance as compared with conventional RLL coding schemes. The simulation results demonstrate that the proposed coding scheme is superior to Manchester code and 8B10B block code in terms of the brightness and BER performance.
09 May 2016
TL;DR: In this article, the authors demonstrate the transmission of 30Gbit/s three-dimensional carrierless-amplitude phase modulation (3D-CAP) signals over 12-km single mode fiber (SMF) using bandwidth-limited devices.
Abstract: We experimentally demonstrate the transmission of 30-Gbit/s three-dimensional carrierless-amplitude-phase modulation (3D-CAP) signals over 12-km single mode fiber (SMF) using bandwidth-limited devices. To our best acknowledge, this is the highest speed transmission of 3D-CAP with fiber distance over 10 km.
TL;DR: This letter proposes a novel SM-based MIMO system with index modulation technique (SM-MIMO-IM), which provides significant performance improvements and additional diversity gain compared to the classical SM and other some techniques given in the literature.
Abstract: Multiple-input multiple-output systems with spatial modulation (MIMO-SM) have been recently proposed for high data rate, low complexity transmission schemes. However, in the SM, the antenna of the transmitter is randomly activated by the spatially modulated information bit sequence. Due to bad conditions of the active antenna's channel determined by the SM technique, the system would be likely to transmit frame with errors. This causes a significant reduction in the system performance. In this letter, to eliminate the bad effects of the channel assignment of the SM, we propose a novel SM-based MIMO system with index modulation technique (SM-MIMO-IM) when operating over i.n.d. and i.i.d. Rayleigh fading channels. The average symbol error rate (SER) and bit error rate (BER) of the proposed scheme are derived. It can be seen from numerical results that SM-MIMO-IM provides significant performance improvements and additional diversity gain compared to the classical SM and other some techniques given in the literature. Furthermore, the proposed mathematical analyses have been verified through the Monte-Carlo simulations.
TL;DR: A low-complexity detector (LCD) for binary CPM with small modulation index is proposed, which can generate appropriate metrics for the soft decision decoding, which is desirable in a coded CPM system.
Abstract: Binary continuous phase modulation (CPM) with modulation index $h = 0.5$ can be approximated by a linear modulation, which leads to a low-complexity serial receiver. By reconstructing CPM signals generated with a small modulation index into equivalent CPM signals with modulation index $h = 0.5$ , a low-complexity detector (LCD) for binary CPM with small modulation index is proposed. The complexity of the resulting detector is significantly reduced with respect to that of optimal coherent receivers with negligible performance loss. In addition, the detector can generate appropriate metrics for the soft decision decoding, which is desirable in a coded CPM system.
03 Mar 2016
TL;DR: This paper analyzes OFDM system inimitability in AWGN and Rayleigh fading channel using M-QAM modulation schemes and demonstrates that the BER increases as the modulation order increases.
Abstract: The concert of wireless communication systems depends on wireless channel environment. By properly analyzing the wireless channels, we can develop an efficient wireless communication system. M-QAM modulation schemes are preferred because in this scheme more than one bit can be grouped and transmit at a time, which is very effective for band limited channels. M-QAM (M-Quadrature Amplitude Modulation) is the most effective digital modulation technique as it is more power efficient for larger values of M. In this paper, we analyze OFDM system inimitability in AWGN (additive White Gaussian Noise) and Rayleigh fading channel using M-QAM modulation schemes. Rayleigh fading channel is describe by Clarke and Gans model. The performance measured in terms of bit error rate (BER) is evaluated for M = 4, 8 and 16 modulation schemes of M-QAM numerically and verified our analytical results by computer simulation. It has been demonstrated that the BER increases as the modulation order increases.
Patent•
IBM1
TL;DR: In this article, a four-level pulse amplitude modulation (QAM) receiver with a non-return-to-zero majority voting circuit coupled to the outputs of the samplers is presented.
Abstract: A four-level pulse amplitude modulation receiver has a four-level pulse amplitude modulation mode and a non-return-to-zero modulation mode. First, second, and third four-level pulse amplitude modulation samplers are coupled to an input. Each of the samplers has a corresponding output in turn including a corresponding binary decision of the first, second, and third samplers. A four-level pulse amplitude modulation decoder circuit has inputs coupled to the outputs of the samplers. The four-level pulse amplitude modulation decoder circuit is active in the four-level pulse amplitude modulation mode. The receiver also includes a non-return-to-zero majority voting circuit coupled to the outputs of the samplers. The non-return-to-zero majority voting circuit has an output and is configured to output a majority decision of the corresponding binary decisions of the samplers, and is active in the non-return-to-zero modulation mode.
01 Dec 2016
TL;DR: This paper proposes a low complexity maximum likelihood timing estimator for pulse position modulation with inter-symbol guard times which significantly outperforms the prior art in this domain and achieves the Cramer-Rao bound.
Abstract: Deep space optical communications promises orders of magnitude growth in communication capacity, supporting high data rate applications such as video streaming and high- bandwidth science instruments. Pulse position modulation is the modulation format of choice for deep space applications, and by inserting inter-symbol guard times between the symbols, the signal carries the timing information needed by the demodulator. Accurately extracting this timing information is crucial to demodulating and decoding this signal. In this paper we propose a low complexity maximum likelihood timing estimator for pulse position modulation with inter-symbol guard times which significantly outperforms the prior art in this domain. We show that this estimator can achieve the same performance as prior estimators with an order of magnitude less signal flux, or multiple orders of magnitude less flux- accumulation time. Further we show that this estimator achieves the Cramer-Rao bound, making it asymptotically efficient. This method does not require an explicit synchronization sequence, freeing up channel resources for data transmission.
TL;DR: The performance of DBPSK-MPPM technique is evaluated in long-haul transmission using GN-model and the BER expression is extended to address fiber nonlinearity.
Abstract: In this paper, we evaluate the performance of hybrid differential phase shift keying-multipulse pulse position modulation (DPSK-MPPM) techniques in long-haul nonlinear-dispersive optical fiber transmission. An expression for the nonlinear interference variance is obtained analytically using the Gaussian noise (GN) model. We derive upper-bound expressions that take into account the fiber nonlinearity impact on the DPSK-MPPM system’s performance for both bit- and symbol-error rates (BER and SER). The tightness of the BER’s upper bound is verified using Monte Carlo simulation. The numerical analysis is carried out based on the proposed setup supplemented by a realistic simulation scenario for the DPSK-MPPM long-haul optical transmission system. Our results reveal that while the hybrid DPSK-MPPM technique outperforms both traditional DPSK and MPPM techniques under amplified spontaneous emission (ASE) noise (linear limit), it is less robust when fiber nonlinearity is considered. However, under the impact of low nonlinearity, the performance of a hybrid technique still surpasses the traditional ones. We also discuss the effect of some wavelength-division multiplexing (WDM) parameters on optimal system performance. The nonlinear interference penalties on the maximum reachable distances by both hybrid and traditional modulation systems are then investigated at a forward-error correction (FEC) requirement (BER=10−3). In particular, at an average launch power of −8 dBm, the hybrid DQPSK-MPPM system with a total frame length of eight time slots including two signal time slots outreaches a traditional DQPSK system by 950 km.
10 May 2016
TL;DR: In this article, an adaptive modulation technique by using digital pulse interval modulation (DPIM) was introduced to obtain the maximum throughput under average power constraint. And the results indicated that adaptive DPIM outperforms previous adaptive modulation schemes based on PPM.
Abstract: Free space optical link provides a number of advantages in terms of high data rate, resistance to jamming and license free data transmission. Atmospheric turbulence is a great challenge in clear sky when an optical wave is propagated through the atmosphere. Since turbulence-induced fading changes slowly, adaptive techniques can be used to mitigate the problem of fading. Compared to classical adaptive modulation schemes, here, we introduce an adaptive modulation technique by using digital pulse interval modulation (DPIM) to obtain the maximum throughput under average power constraint. We present numerical results in terms of throughput and outage probability for nominal values of FSO system. Our results indicate that adaptive DPIM outperforms previous adaptive modulation schemes based on pulse position modulation (PPM).