Modulation & Demodulation:
Wireless communication relies heavily on modulation and demodulation. By modulating with a high frequency carrier signal, we can convert the frequency of the original baseband signal to a very high frequency. Because, in many ways, a low frequency baseband signal is unsuitable for wireless communication. Modulation, on the other hand, increases channel capacity by delivering many data streams via a single channel at the same time. Because of this property of modulation, we employ it in wired communication as well. In a communication system, the modulation process is performed on the signal right before transmission from the antenna.
Signal Processing at receiver side for wireless communication:
To recover the signal, we perform the exact opposite on the receiver side. If we execute signal encoding on the transmitter side, we must also do signal decoding on the receiver side. If we modulate on the TX side, we must demodulate on the RX side, as indicated in the diagram above. At the end of process, receiver sends the feedback to the transmitter or sender so that sender can be informed whether the data packet is successfully received or not.
Acknowledgement / Feedback from Receiver Side in Wireless Communication:
It is essential to inform sender / transmitter that specific message / data packets have been received for reliable communication. For TCP transmission protocol sender sends a data packet to receiver. Then at receiver side it checks whether whole data packets have been transferred or not. If it received by receiver then it sends acknowledgement to transmitter. If not then whole packet is retransferred again.
Deep Dive:
If the source is analog in nature, we use the sampling and quantization approach to digitalize the signal. However, before transmission, we modulate the message signal with a high-frequency carrier signal. In fact, the signals that travel over a wireless channel are analog in nature. We typically don't need to apply modulation while using wired communication. We employ line coding techniques such as RZ, NRZ, duo binary, Manchester waveform, etc. to convert the digitalized signal into various waveforms.
Modulation Constellation Diagrams BER vs. SNR BER vs SNR for M-QAM, M-PSK, QPSk, BPSK, ... 1. What is Bit Error Rate (BER)? The abbreviation BER stands for bit error rate, which indicates how many corrupted bits are received (after the demodulation process) compared to the total number of bits sent in a communication process. It is defined as, In mathematics, BER = (number of bits received in error / total number of transmitted bits) On the other hand, SNR refers to the signal-to-noise power ratio. For ease of calculation, we commonly convert it to dB or decibels. 2. What is Signal the signal-to-noise ratio (SNR)? SNR = signal power/noise power (SNR is a ratio of signal power to noise power) SNR (in dB) = 10*log(signal power / noise power) [base 10] For instance, the SNR for a given communication system is 3dB. So, SNR (in ratio) = 10^{SNR (in dB) / 10} = 2 Therefore, in this instance, the signal power i