China
Africa
Explore chapters and articles related to this topic
Coding and Modulation for Free-Space Optical Communications
Published in Hamid Hemmati, Near-Earth Laser Communications, 2020
In Phase Shift Keying (PSK), information is encoded into the phase of the carrier. We'll consider the simplest case, binary PSK (BPSK). Let xk∈{0,1} be the k-th bit transmitted by the source. In BPSK, xk is mapped to a pulse of light of duration Ts seconds a(t)=R{2Pavejω0(t+xkπ)},t∈((k−1)MTs,kMTs]
Low-Power Baseband Processors for Communications
Published in Christian Piguet, Low-Power Processors and Systems on Chips, 2018
Digital modulation is the process of mapping a bit stream to a stream of complex samples. The first (and sometimes the only) step in the digital modulation is to map groups of bits to a specific signal constellation, such as binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), or quadrature amplitude modulation (QAM). These are different ways of mapping groups of bits to the amplitude and phase of a radio signal). In most cases, a second step, domain translation, is applied. In an orthogonal frequency division multiplexing (OFDM) system (i.e., a modulation method where information is sent over a large number of adjacent frequencies simultaneously), an inverse fast fourier transform (IFFT) is used for this step. In a direct sequence spread spectrum (DSSS) system (e.g., direct sequence-code division multiple access [DS-CDMA], a “spread spectrum” method of allowing multiple users to share the RF spectrum by assigning each active user an individual “code”), each symbol is multiplied with a spreading sequence of ones and minus ones. The final step is symbol shaping, which transforms the square wave to a band-limited signal using a finite impulse response (FIR) band-pass filter. This is necessary to make sure no parts of the transmitted signal are outside the permitted frequency band.
Basic of 5G Networks: Review
Published in Ashish Bagwari, Geetam Singh Tomar, Jyotshana Bagwari, Advanced Wireless Sensing Techniques for 5G Networks, 2018
A.N. Ibrahim, M.F.L. Abdullah, M.S.M. Gismalla
QAM is widely used in mobile communications and is mainly used in LOS for microwave systems, coaxial cables, and satellite communications. QAM transmits the information data by modulating the amplitudes of two carrier waves, using straight amplitude modulation for the analog signal and Amplitude Shift Keying (ASK) for the digital signal. QAM requires linear amplifiers and coherent detection [59]. QAM has a moderate energy efficiency, excellent bandwidth, and complexity on the receiver side because it needs to track the frequency, phase, and amplitude of the carrier and also track the sampling time and symbol rate [59]. Some of common forms of QAM include 16QAM, 32QAM, 64QAM and 128QAM. In QAM, the signal in two carriers is shifted in phase by 90°, hence it will be modulated and the output consists of both phase and amplitude variations which may also be considered as a mixture of amplitude and phase modulations [3].
Sub-Sampled Time Domain Sparse Information in Wired OFDM and STBC-OFDM Systems
Published in IETE Technical Review, 2022
The binary input data stream at the OFDM transmitter is encoded in order to generate parity bits that are used for error correction on the receiver side (Forward Error Correction – FEC). Then, the data and the parity bits are interleaved (to avoid burst errors) and mapped to symbol constellations like Quadrature Phase Shift Keying (QPSK), or q-order Quadrature Amplitude Modulation (q-QAM). The N, modulated symbols Xk (0≤k < N) are complex numbers that form a parallel input to an N-point IFFT that generates the time symbols xn (0≤n < N) that are serially transmitted over the wired or wireless channel after appending a Cyclic Prefix (CP) for Inter-Symbol Interference (ISI) avoidance.
Alternative Approaches to Program Memristor and Reduce the Effect of Random Telegraphic Noise
Published in IETE Journal of Research, 2022
P. Michael Preetam Raj, M. P. Srinivasan, Souvik Kundu
Over the last one decade, memristor has emerged as the most promising two terminal circuit element owing to its important advantages such as improved scalability (< 10 nm), low power consumption (few µW), compatibility with CMOS fabrication process and its inherent ability to perform in-memory computing [1–5]. Since its inception, memristor has become an important component for modern day electronics with applications in various fields such as non-volatile memories, analog systems, digital electronics, neuromorphic computing and FPGA based reconfigurable systems [6–12]. In the era of modern electronics, it is capable of replacing the widely used metal oxide semiconductor (MOS) devices [13], which have reached fundamental device scaling limitations [5,14,15]. It is well known that frequency based modulation techniques were widely utilized for electronic applications [16]. Signals modulated through such techniques possess important advantages of high noise resilience and low power consumption, when compared to other existing modulated signals [16]. An important class of frequency based modulation technique is frequency shift keying (FSK) in which the digital data is in the form of a sine wave where each bit value is assigned a certain high frequency [17]. In FSK modulation, the digital data is stored in the frequency of the modulated signal. For example, within an m-ary FSK, m types of data get transmitted through utilizing m different frequencies [17]. Researchers have demonstrated that memristance changes with the frequency of the externally applied power source [12,18]. Hence, one can program memristance through utilizing frequency based modulation techniques in order to develop noise immune and low power consumption based electronic systems. Further, there is a necessity to develop advanced modulation mechanisms in order to increase the degree of freedom in programming the devices.
Secrecy sum-rate based illegitimate relay selection
Published in Australian Journal of Electrical and Electronics Engineering, 2023
where and represent the binary phase shift keying (BPSK) and the quadrature phase shift keying (QPSK) modulations, respectively. The BPSK modulation is considered for the performance analysis. Substituting the derived CDF expression into (26), the secrecy error probability metric’s analytical derivations can be obtained.