Waveform Shaping Techniques for Bandwidth-Efficient Digital Modulations

The 5G wireless communication requires transmission of information with high data rate, channel capacity, QoS in addition to less PAPR. The modulation scheme is performed in the physical layer of the network. Multi Carrier Modulation (MCM) schemes are widely preferred over single carrier modulation. Orthogonal Frequency Division Multiplexing (OFDM) is a very competent modulation method used in 4G wireless communication systems. This paper concentrates on the principle, analysis and comparison of Cyclic Prefix OFDM (CP-OFDM) with the Filtered OFDM (F-OFDM) at a frequency of 15 MHz, SNR of 18dB for various modulations like QPSK, 16QAM, 64QAM and 256QAM. F-OFDM is a flexible form of OFDM technique with lesser value of the peak to average power ratio (PAPR) allowing it to be used in the 5G wireless applications.

19 - Digital modulation

Determining the effectiveness of any modulation scheme in mobile radio environment comprises reliability and error performance evaluation. The later involves determining the increase in Eb/No required to maintain a fixed BER. Thus, error performance plays a vital role in the selection of modulation scheme for specific applications. This paper begins with review of the conceptual difference between SNR and Eb/No performance metrics of communication system. The significance of BER for error performance analysis is verified by comparing the Eb/No characteristic plots for digital modulation schemes: M-PSK, M-QAM and M- FSK. The comparison parameters includes modulation order and simulation environment. The simulation environment considered are additive white Gaussian noise (AWGN) channel model and Rayleigh fading channel model. There are two important issues targeted in this paper. Firstly, the significance of the concept of multi-carrier modulation (MCM) used in wireless LAN standard IEEE802.11a is verified. The technology resolves the problem of multi-path in a piecewise manner, i.e. the linear relationship between error probability and Eb/No in case of wide-band Rayleigh fading channel is transformed into a number of narrow-band sub-channels with exponential relationship. Then, the sub-channel modulation schemes are compared by observing the effect of modulation order on BER, spectral usage, noise tolerance and trade-off issues. Finally, the inferences drawn out of the comparative analysis justifies the use of low-order PSK modulations for control and higher-order QAM for payload transmissions respectively, for OFDM implementation as in IEEE802.11a.

In this paper we test and compare different modulation strategies to be used in ultra-wide band (IR-UWB) communications. In the UWB systems of interest in this work the information is conveyed by short-duration pulses; the modulation scheme determine how the data stream is to be transmitted over those pulses. Here we test and compare several schemes based on three types of modulation. The first type is the pulse position modulation (PPM), which includes a pulse delay according to the data to be transmitted. The second is the recently proposed pulse shape modulation (PSM), that uses a different pulse shape to each data. The third one, proposed in this paper, is an M-ary modulation scheme that combines the shape and amplitude of the pulse to transmit the data, which we call pulse amplitude and shape modulation (PASM). Other M-ary schemes are tested, including the recent orthogonal M-ary PSM, based on orthogonal Hermite functions, and a new quaternary PPM scheme, also proposed here. All schemes are tested over an AWG channel.

Minimum Shift Keying (MSK) is considered to be a spectrally efficient modulation scheme, in comparison with other families of constant envelope modulation. However, its main sidelobe can be of some worry in digital data transmission, particularly over nonlinear channels. Therefore, it is practically of interest to search for efficient pulse shaping schemes, largely proposed either through baseband pulse shaping and/or filtering processing. In this paper a new pulse shaping method based on Walsh functions is proposed to be used in MSK-type signaling. A methodology is proposed for designing the optimum pulse shape; and this attains improvement in spectral efficiency (i.e., bps/Hz) over straight MSK, for the same channel bandwidth. The fractional out-of-band power is used to compare the behavior of the system under the new proposed technique. As well, error rate performance in such system is used in the evaluation of this work. Results reveal that good improvement can be attained in spectral efficiency at the expense of error rate performance when these functions are used.

Wireless communication with multicarrier modulation is very attractive for present and future communication network due to immunity to delay spread and fading. However, such systems are receptive to carrier frequency offset (CFO) due to Doppler effect in a mobile communication system. Analysis is carried out for a wireless communication system with multi carrier (MC) direct sequence (DS) code division multiple access (CDMA) technique with CFO to find the expression of SINR and the bit error rate (BER) with BPSK coherent detection receiver. The results are checked out in term of SINR and BER for various values of CFO variance, considering Gaussian distribution of CFO. The result shows that there occurs BER floor due to CFO for SC and Multi Carrier (MC) DS-CDMA and there is a power penalty at a given BER which is high for the Multi Carrier (MC) DS-CDMA compared to SC DS-CDMA. It is also observed that increasing the number of subcarriers does not affect much in MC DS-CDMA, which will definitely allow to minimize the delay spread which is a vital limitation of wireless communication system.

Short-Time Fourier Transform-Brillouin Optical Time-Domain Reflectometry (STFT-BOTDR) implements STFT over the full frequency spectrum to measure the distributed temperature and strain along the optic fiber, providing new research advances in dynamic distributed sensing. The spatial and frequency resolution of the dynamic sensing are limited by the Signal to Noise Ratio (SNR) and the Time-Frequency (T-F) localization of the input pulse shape.T-Flocalization is fundamentally important for the communication system, which suppresses interchannel interference (ICI) and intersymbol interference (ISI) to improve the transmission quality in multicarrier modulation (MCM). This paper demonstrates that theT-Flocalized input pulse shape can enhance the SNR and the spatial and frequency resolution in STFT-BOTDR. Simulation and experiments ofT-Flocalized different pulses shapes are conducted to compare the limitation of the system resolution. The result indicates that rectangular pulse should be selected to optimize the spatial resolution and Lorentzian pulse could be chosen to optimize the frequency resolution, while Gaussian shape pulse can be used in general applications for its balanced performance in both spatial and frequency resolution. Meanwhile,T-Flocalization is proved to be useful in the pulse shape selection for system resolution optimization.

Continuous phase modulation is a well understood modulation scheme which utilizes a constant envelope signal with inherent memory to create a bandwidth efficient waveform. The pulse shapes defined for CPM modulation influence the bandwidth, demodulation complexity, and power efficiency and can be spread across multiple symbols. This paper investigates a novel modulation scheme that is comprised of a family of pulse shapes which add parallel branches to the existing CPM trellis. The resulting modulation scheme maintains the power efficiency of the underlying modulation while increasing the data rate of the waveform. The spectral efficiency is not affected by the increase in data rate while the receiver complexity is reduced. The first part of the paper outlines the standard CPM modulation and a pair of complementary (non-orthogonal) phase pulse shapes is presented. The corresponding effect on bandwidth, power efficiency, and receiver complexity is analyzed and the advantages of this modulation technique are discussed. Then, a novel methodology for generating a family of optimal pulse shapes is discussed and various generation methods are compared. The spectral and power efficiencies of the resulting M-ary waveform are then compared to an equivalent, standard CPFSK modulation.

The significance of digital communication has been well accepted all over the world. It has been widely used in wireless networks like satellite communication, and 4G and 5G technologies as it provides high data connectivity and efficiency. For long-distance transmission and reception of signals, maintaining the signal quality is very important and therefore an efficient modulation and demodulation scheme is required. In this paper, the quadrature phase shift keying (QPSK) modulation scheme is being presented. Its several advantages over other digital modulation techniques made it one of the best forms of digital modulation. The concept of software-defined radio has been used as a test bed for implementing QPSK modulation. Simulation of QPSK modulation and demodulation process is performed in Laboratory Virtual Instrument Engineering Workbench software, and the digital transmission and reception of signals are done through Universal Software Radio Peripheral. The signal experiences sampling, quantization, filtering, encoding, modulation, demodulation, decoding, with and without the addition of additive white Gaussian noise on the graphical interface of NI LabVIEW. Several investigations have been done on digital modulation, but they are covered entirely on simulation in any software. In this paper along with the implementation of modulation and demodulation part, the transmission and reception of the signal are also performed using USRP.

Record high 19.125 Gb/s real-time end-to-end dual-band optical OFDM (OOFDM) transmission is experimentally demonstrated, for the first time, in a simple electro-absorption modulated laser (EML)-based 25 km standard SMF system using intensity modulation and direct detection (IMDD). Adaptively modulated baseband (0-2GHz) and passband (6.125 ± 2GHz) OFDM RF sub-bands, supporting line rates of 10 Gb/s and 9.125 Gb/s respectively, are independently generated and detected with FPGA-based DSP clocked at only 100 MHz and DACs/ADCs operating at sampling speeds as low as 4GS/s. The two OFDM sub-bands are electrically frequency-division-multiplexed (FDM) for intensity modulation of a single optical carrier by an EML. To maximize and balance the signal transmission performance of each sub-band, on-line adaptive features and on-line performance monitoring is fully exploited to optimize key OOFDM transceiver and system parameters, which includes subcarrier characteristics within each individual OFDM sub-band, total and relative sub-band power as well as EML operating conditions. The achieved 19.125 Gb/s over 25 km SMF OOFDM transmission system has an optical power budget of 13.5 dB, and shows almost identical bit error rate (BER) performances for both the baseband and passband signals. In addition, experimental investigations also indicate that the maximum achievable transmission capacity of the present system is mainly determined by the EML frequency chirp-enhanced chromatic dispersion effect, and the passband BER performance is not affected by the two sub-band-induced intermixing effect, which, however, gives a 1.2dB optical power penalty to the baseband signal transmission.

A reported is presented on the first communication system using vectorial modulation schemes above 500 GHz. Using Schottky-based electronic technologies at 588 GHz, potentialities of high-level multi-carrier modulation schemes for wireless links are analysed. The wireless link is composed of an emitter with a sub-harmonic mixer for up-conversion from 294 to 588 GHz and carrier modulation. A pumped zero-bias detector is used at reception. Mono-carrier signalling is realised using an up to 32-symbol modulation scheme and multi-carrier terahertz transmission is also achieved using several modulation schemes in parallel.

Adaptive sample rate converters (SRC) for the multi-standard mobile transceiver have been designed. GSM, UMTS and HIPERLAN2 standards have been chosen to establish the requirements for the SRCs. In the transmitter, the output signal of the data modulator is sampled at the symbol or chip frequency specified by the standards and needs to be converted into a common updating frequency of the D/A-converter. Pulse shaping and emission mask requirements are taken into account. In the receiver, A/D-conversion is also performed at a common fixed clock rate. Thus the SRC is needed to convert the A/D-converter sampling rate into a symbol or chip frequency that will be applied for further baseband signal processing. Channelization requirements defined by the standards are used as criteria for the performance analysis in the receiver. Based on the performance analysis, the complexity analysis is covered. It includes computational complexity, gate count, area and power consumption estimation for the chosen platform.

Visible light communication (VLC) is considered a breakthrough wireless communication technology that has been proven capable of achieving very high data rates. This is a key advantage in indoor communication scenarios, since the vast majority of wireless traffic is witnessed in indoor communications. In every wireless system, the trade-off between achievable throughput, transmit signal power and corresponding error rate performance is largely dependent upon the considered modulation format. This is also the case in VLC systems, which are typically characterized by stringent performance requirements. Motivated by this, in the present contribution we introduce the space shift keying (SSK) modulation scheme in the context of non-orthogonal-multiple-access (NOMA) communications, which have been shown to be a performance enhancer of indoor based VLC systems. Based on this, all network users in the considered set up receive the same superimposed signal of all NOMA users, which is transmitted from the activated transmitters corresponding to the multiplexed SSK users information. Based on this and assuming a unique maximum likelihood detection, we quantity the system performance in terms of the corresponding bit error rate (BER) performance at each receiver. This analysis leads to the development of useful insights of theoretical and practical interest, which are expected to be useful in the effective design, implementation and deployment of SSK in NOMA based VLC systems.

Choice of ultra wideband (UWB) pulse shapes has become an interesting challenge such that the spectral limits of the frequency band approved by the Federal Communications Commission (FCC) can be utilised efficiently. In this paper, we compare the efficiency of various UWB pulse shapes based upon their power spectral density (PSD) and autocorrelation functions (ACF). We propose a set of prolate spheroidal wave functions (PSWF) for a typical M-ary pulse shape modulation (PSM) scheme. In the process, we show closed form expressions for the ACF of PSWF-based UWB pulse shapes of different orders.

The ripple modulation (RM) is a technique that provides a variable output voltage by using the output voltage ripple of a switching-mode power converter. It was proposed to reproduce the communication signal of a visible light communication transmitter, thus avoiding the use of power inefficient linear power amplifiers. However, the RM has a major drawback: it has not been reported how to reproduce multicarrier modulation (MCM) schemes, which are the preferred modulation schemes due to their high performance in wireless communications. In this paper, it is demonstrated that the RM can be used to reproduce MCM schemes by considering the envelope and the instantaneous phase of the communication signal. Moreover, the control system of the power stage is described in detail, explaining how to modulate both the width and the phase of the gate signals, the calculation of the phase shift that is required for tracking the envelope, etc.