Digital Communication (Modulation Techniques, etc.)
Importance of digital communication in competitive exams and core industries
Q. What is coherence bandwidth?
Q. What is flat fading and slow fading?
A. See the answer.
Q. What is a constellation diagram?
Q. One application of QAM
A. 802.11 (Wi-Fi)
Q. Can you draw a constellation diagram of 4QPSK, BPSK, 16 QAM, etc.
A. Click here
Q. Which modulation technique will you choose when the channel is extremely noisy, BPSK or 16 QAM?
A. BPSK. PSK is less sensitive to noise as compared to Amplitude Modulation. We know QAM is a combination of Amplitude Modulation and PSK. Go through the chapter on "Modulation Techniques".
Q. Real-life application of QPSK modulation and demodulation
Q. What is OFDM? Why do we use it?
Q. What is the Cyclic prefix in OFDM?
Q. In a constellation diagram, which parameters are dominant to resist noise?
A. (1) Euclidian distance between constellation points. As Euclidian distance decreases, the effectiveness of noise increases.
(2) Signal-to-noise ratio per bit, or in plain language, power of each constellation point or transmitted power.
Q. What does Quantization actually do in a communication system/process?
A. Quantization helps produce finite signal levels rather than infinite levels.
Q. Key performance measures of bandpass modulation schemes are
A. Low pass, band pass, and high pass are three terms that may be significant. We use LPF, where the effective signal frequencies are below a specific frequency. For a high-pass signal/filter, the opposite is true. In this case, we're only interested in higher frequencies of a threshold frequency. Now, bandpass signals are signals whose operational frequency is limited to a specific range, such as f1 MHz to f2 MHz. This differentiates it from the other two categories.
Bandpass modulatiModulation in the majority of the modulations. In the context of eavesdropping, this property is quite helpful.
Q. Five applications of Ask in digital modulation techniques
A. Off-on keying is another name for it. The transmitter uses this technology to send a signal fluctuating in amplitude or volts. It usually needs power to send bit '1' and nearly little energy to send bit '0.' ASK is used because it is simple to generate and has less complex circuitry. The following are a few examples of ASK applications:
1. Radio frequency (RF) applications at low frequencies
2. Wireless communication between base stations
3. Devices for industrial networks
Q. Compression modulation techniques
A. The pulse compression approach sends the signal through a matching filter. A matched filter is a linear filter with a maximized signal-to-noise ratio.
Q. Why is it important to have voice and tone modulation
A. ModulatiModulation conversion of a low-frequency baseband signal to a high-frequency signal using a high-frequency carrier wave. Because sending a baseband signal might cause severe interference with other baseband signals if everyone sends unmodulated baseband signals, we employ modulatiModulation the signal wirelessly transferable. In some instances, though, the antenna size could be a few kilometers if we do not use modulatiModulation. You know, human voice signal has many frequencies up to 4 KHz. Keep in mind that the human voice signal has more than one frequency. A signal is described as a single tone if it has only one frequency. However, if a signal contains many frequencies, we must modulate all of those frequencies. The modular modulation is referred to as 'multi-tone modulation.'
Q. Difference between modulated and unmodulated signal
A. The term "modulated signal" refers to a signal modulated using a high-frequency carrier signal.
In the case of wireless communication, modulatiModulationial. We modulate the signal to make it a bandpass signal. As a result, there is less interference with other signals. Modulation, on the other hand, allows signal transmission to be multiplexed. As a result, even in wired communication, modulatiModulationsionally is used to convey multiple data streams simultaneously.
Q. the basic rules to be maintained for modulation's primary purposes have already been discussed, such as antenna size reduction, signal multiplexing, etc. Signals are modulated with I and Q carriers in general, according to the basic rule of modulatiModulationtters "I" and "Q" stand for "in-phase modulation" and "quadrature modulation," respectively. We modify the data streams with varying amplitudes and phases in QAM (quadrature amplitude modulation).
Q. By doing modulation, audio can be sent to which distance
A. In general, modular modulation sends a signal for various purposes. Because the frequency of a modulated signal is substantially greater than that of an unmodulated signal, unmodulated signals may travel longer distances than modulated signals. The transmission distance is a different question that is determined by various factors.
Q. Which type of questions can be asked in competitive exams on modulatiModulatione difficulty of the exam questions might range from simple to complex. You may be asked what modulatiModulation Modulation hot topics include QPSK and QAM. On the other hand, you can be questioned about modulation techniques utilized in contemporary 4G and 5G communication technology.
Q. Which modulation technique has the highest Bandwidth?
A. For Amplitude modulation
Bandwidth of DSB => 2fm (fm=frequency of Message Signal)
For SSB-SC => fm
For VSB => Slightly greater than SSB-SC due to additional guard band
For Frequency modulation and Phase modulation,
Bandwidth => 2(ฮฒ +1)fm (ฮฒ = ratio of deviation of the carrier signal to the variation of modulating signal)
Q. If modulatiModulationdone, can we get information from different calls
A. Firstly, try to understand the primary purpose of modulatiModulation. Explain with an example. In the case of 2G GSM, each channel is of 200 KHz bandwidth, and eight users can be connected to the base station or cell tower simultaneously through the same channel. They use a TDM scheme to connect eight users simultaneously. We have already mentioned in the chapter on 'Modulation' that one of the primary purposes of modulation techniques is to multiplex the data by providing different independent and simultaneous data streams.
Q. Modulation and demodulation techniques in DCT
A. DCT is used in image processing, whereas DCT is used for simplification in calculation. DCT is taken as the basis function, and then the image's DCT transform and filters' DCT transform are multiplied. As we know, in the case of the convolution of two parts, we can bear the Fourier transform of those functions. Here in DCT, it gives us an advantage in simplification in calculation.
Q. Discuss about compression modulation techniques
Q. What is the high data transfer rate in modulatiModulationodulation technique using analog input signal
A. Baseband analog signals are input in analog modulation techniques such as amplitude modulation, frequency modulation, and phase modulation. The input message signal is modulated using a high-frequency carrier wave.
Q. Why should we add carrier signal to modulated wave to generate modulated wave?
A. See answer
Q. How do we overcome the limitations of underwater wireless communication?
Q. What are the deductions made before handover in wireless communication?
Q. Wireless channels are more prone to bit error than wired channels
Q. Wireless channels are more prone to bit error than wired channels
Q. What is used to measure the reliability of communication channels?
Q. How does channel bandwidth offset communication?
A. To overcome interference between two signals, it is common practice in wireless communication to slightly vary the signal by frequency, phase, or amplitude.
Q. What are the salient features of base modulation?
Q. Coded Modulation technique needs Bandwidth when compared to ordinary Bandwidth?
Q. Do pulse modulation techniques use more power?
Q.