Real & Simulated QPSK Up-Converted Signals by a Sampling Method Using a Cascaded MZMs Link

This study focuses on a novel concept of transmitting of a quadrature phase shift keying (QPSK) modulation by an electro-optical frequency up-conversion using a cascaded Mach–Zehnder modulators (MZMs) link. Furthermore, we conduct and compare the results obtained by simulations using the Virtual Photonics Inc. (VPI) (Berlin, Germany) simulator and real-world experiments. The design and operating regime peculiarities of the MZM used as a sampling up-converter mixer in a radio over fiber (RoF) system are also analyzed. Besides, the simulation and experimental results of static and dynamic characteristics of the MZM have approximately the same behavior. The conversion gain of the cascaded MZMs link is simulated over many mixing frequencies and it can decrease from 17.5 dB at 8.3 GHz to −4.5 dB at 39.5 GHz. However, in real world settings, it may decrease from 15.5 dB at 8.3 GHz to −6 dB at 39.5 GHz. The maximum frequency range is attained at 78.5 GHz for up-conversion through simulations. Error vector magnitude (EVM) values have been done to evaluate the performance of our system. An EVM of 16% at a mixing frequency of 39.5 GHz with a bit rate of 12.5 Gbit/s was observed with the considering sampling technique, while it reached 19% in real-world settings with a sampling frequency of 39.5 GHz and a bit rate of 12.5 Gbit/s.

A Carrier Parameter Decoupling Algorithm for High Order APSK Modulation

In satellite communication, carrier parameter estimation usually uses a serial structure, and the accuracy of frequency offset estimation (FOE) will greatly affect the accuracy of phase offset estimation (POE). A new carrier synchronization mode (NCSM) can realize the decoupling of carrier FOE and POE to a certain extent, but this mode is based on multibase phase shift keying (MPSK) modulation analysis, the decoupling performance is poor when uses in amplitude phase shift keying (APSK) modulation, and the decoupling performance of NCSM has a low tolerance of frequency offset. An improved carrier parameter estimation decoupling technique is proposed to solve these problems. The simulation results show that, compared with the original method, under the premise of ensuring the accuracy of carrier parameter estimation, the proposed method is more robust to the modulation mode, the POE has stronger antioffset ability, and the normalized FOE range has been significantly enhanced.

Waveform Design for Energy Efficient OFDM Transmission

In this chapter, a green radio transmission using the binary phase-shift keying (BPSK) modulated orthogonal frequency-division multiplexing (OFDM) signal is addressed. First, the OFDM transmission signal is clearly stated. For a specified performance of the system, the least transmit power occurs by the optimal OFDM shape, which is designed to minimize the average inter-carrier interference power taking into account the characteristic of the transmit antenna and the detection process at the receiver. The optimal waveform is obtained by applying the calculus of variations, which leads to a set of differential equations (known as Euler equations) with constraint and boundary conditions. Results show the transmission effectiveness of the proposed technique in the shaping of the signal, as well as its potential to be further applied to smart context-aware green wireless communications.

Hybrid FSK-PSK Waveform Optimization for Radar Based on Alternating Direction Method of Multiplier (ADMM)

In this paper, a new radar signal modulated with a hybrid of the frequency shift keying (FSK) and the phase shift keying (PSK) signal—i.e., the FSK-PSK signal—is studied. Different phase encoding sequences are used to modulate the sub-pulses to obtain lower sidelobe levels and ensure signal orthogonality. In addition, to counter intra-pulse slice repeater jamming of specific length generated by the enemy jammer, an orthogonal waveform made of sub-pulses of equal length based on the FSK-PSK modulation scheme is designed. The simulation results show that the optimized discrete phase encoding sequence can significantly enhance the orthogonality of the sub-pulse in the FSK-PSK signal and effectively suppress the slice repeater jamming. Two algorithms are proposed: (1) the low sidelobe waveform optimization algorithm based on ADMM (LSW-ADMM); and (2) the anti-slice-repeater-jamming algorithm based on ADMM (ASRJ-ADMM). Both algorithms exhibit fast convergence speed and low computational complexity.

Application of Broadband Signals to Increase Interference Immunity in Channels with Inter-Symbol Interference

Proposals for improving the noise immunity of receiving phase-shift keying signals in the conditions of inter-symbol interference caused by fading in the channel are presented. The use of Barker sequences for the expansion of modulating information pulses has been substantiated. The results of evaluating the noise immunity of Rice fading channels at various ratios of the effective voltages of the regular and diffuse signal components are presented. Proposals for the practical application of the results obtained are formulated.

Perancangan Model Simulator dan Performansi Kesalahan Bit untuk Variasi Tipe Modulasi Digital Dalam Lingkungan Kanal Additive White Gaussian Noise (AWGN)

Penelitian ini dibuat berdasarkan permasalahan pada penelitian sebelumnya, dimana belum menampilkan gelombang sinyal sesudah melewati kanal Additive White Gaussian Noise (AWGN), serta menampilkan hasil simulasi perbandingan kesalahan bit yang ditampilkan dalam bentuk grafik kurva untuk berbagai tipe modulasi. Selain itu gelombang sinyal probabilitas kesalahan bit masih ditampilkan terpisah serta belum melakukan analisa antara perhitungan dengan hasil simulasi. Maka pada penelitian ini akan dilakukan pengembangan pada source code dan juga dibuatnya graphical user interface (GUI) Matlab beserta dengan perhitungan teoritisnya. Pada hasil simulasi jumlah bit minimal sebesar 100 bit didapatkan untuk modulasi amplitude Shift Keying (ASK), untuk modulasi frekuency shift keying (FSK) dan untuk binary phase shift keying (BPSK). Sedangkan pada jumlah bit maksimum bit sebesar 500 bit didapatkan untuk modulasi ASK, untuk modulasi FSK, dan untuk modulasi BPSK. Dari dua data tersebut menunjukan bahwa data simulasi sudah sesuai dengan teori yang ada, dimana semakin besar energi bit yang digunakan maka bit error rate (BER) yang dihasilkan akan semakin kecil. Kesesuaian simulasi dengan teori didukung juga oleh hasil perhitungan probabilitas kesalahan bit. Hasil simulasi dan teoritis probabilitas kesalahan bit memiliki karakteristik yang sama, dimana modulasi BPSK memiliki penurunan probabilias kesalahan bit yang lebih kecil dibandingkan modulasi ASK dan FSK. Selain itu didapatkan bahwa hasil perhitungan mengalami penurunan kesalahan bit yang lebih kecil serta ideal pada Eb/N0 yang sama untuk setiap percobaannya.

A Simple and Robust Equalization Algorithm for Variable Modulation Systems

This paper proposes a simple and robust variable modulation-decision-directed least mean square (VM-DDLMS) algorithm for reducing the complexity of conventional equalization algorithms and improving the stability of variable modulation (VM) systems. Compared to conventional adaptive equalization algorithms, known information was used as training sequences to reduce the bandwidth consumption caused by inserting training sequences; compared with conventional blind equalization algorithms, the parameters and decisions of the equalizer were determinate, which was conducive to a stable equalization performance. The simulation and implementation results show that the proposed algorithm has a better bit error rate (BER) performance than that of the constant modulus algorithm (CMA) and modified constant modulus algorithm (MCMA) while maintaining the same level of consumption of hardware resources. Compared to the conventional decision-directed least mean square (DDLMS) algorithm, the proposed algorithm only needs to make quadrature phase shift keying (QPSK) symbol decisions, which reduces the computational complexity. In parallel 11th-order equalization algorithms, the operating frequency of VM-DDLMS can reach up to 333.33 MHz.

Intelligent Matching of the Control Voltage of Delay Line Interferometers for Differential Phase Shift Keying-Modulated Optical Signals

In optical communications, differential phase shift keying (DPSK) provides a desired modulation format that offers high tolerance to nonlinear effects in high-speed transmissions. A DPSK demodulator converts the phase-coded signal into an intensity-coded signal at receivers. One demodulation scheme is called balanced detection and is based on a tunable delay line interferometer (DLI). Demodulation performances are determined by the phase delay generated by the DLI, while the phase delay is controlled by a tunable driving voltage on the DLI device. However, a problem in the dynamic adjustment of the control voltage prevents the application of DPSK demodulators. The receivers need to scan the whole control voltage range of the DLI and find the control voltage that maximizes the demodulation performance, but the scan-based method needs to undergo a very long searching time. In our work, we found that the relation between DLI control voltages and demodulation performance can be predicted rapidly by a feedforward neural network (FNN). In this paper, we propose a new method to quickly locate the best DLI control voltage based on an FNN. We also verify the proposed method in simulations and telecommunication systems, and the results show that the proposed method can significantly improve the efficiency of resolving the best demodulation voltages.