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Near-Earth Laser Communications
Published in Hamid Hemmati, Near-Earth Laser Communications, 2020
Some of the popular data transmission formats in lasercom include on-off keying (OOK), PPM, and phase-shift keying (PSK). Prior to transmit signal amplification, the encoder output often feeds into an easily modulatable low-power, high-beam quality laser transmitter (oscillator) in a master oscillator power amplifier (MOPA) configuration. Even though more remains to be done, modulation and coding is a relatively mature subsystem of a lasercom transceiver. This is illustrated in Figure 1.8 where bit error rate (BER) is plotted as a function of Eb/N0, the bit energy-to-noise density for different modulation and coding schemes. The waterfall behavior of the newly developed codes reflects their high efficiency. A high code rate (the ratio of data bits to total bits transmitted in the code words) refers to high information content and low coding overhead. Chapter 6 provides an overview of channel coding techniques for airborne and spaceborne laser communications.
Viterbi Decoders: High Performance Algorithms and Architectures
Published in Keshab K. Parhi, Takao Nishitani, Digital Signal Processing for Multimedia Systems, 2018
Herbert Dawid, Heinrich Meyr, Olaf J. Joeressen
The input stream of information bits is mapped onto k-bit information symbols uk, which are input to a finite state machine (FSM) generating n > k coded bits from the information symbols. The ratio k/n (here 1/2) is called the code rate. The larger the code rate, the smaller the amount of redundancy introduced by the coder. With k = 1, only code rates 1/n are possible. Higher rate codes are known for k > 1. Alternatively, higher rate codes can be created by using a 1/n base or mother code and omitting (puncturing) a part of the coded bits after encoding as specified by a given puncturing pattern or puncture mask [5, 6, 7]. It is shown in [5, 6] that the resulting punctured codes lead to reduced decoding complexity compared to standard codes with the same code rate and k > 1 at negligible performance losses. Today, k = 1 holds for virtually all practically relevant base codes [17]; therefore we consider only this case.
Recording and reproduction
Published in Michael Talbot-Smith, Audio Engineer's Reference Book, 2013
Andy Wilson, Kenneth Gundry, Jan Arts, Jan Maes, Douglas Ford, Peter Skirrow
Error correction In order to ensure later correction of binary data, the input signal must be encoded by some encoding scheme. The data sequence is divided into message blocks, then, each message block is transformed into a longer one, by adding additional information, in a process called �redundancy�. The ratio (Data + Redundant data)/Data is known as the �code rate�. Basically, correction (and detection) of code errors can be achieved by adding to the data bits an additional number of redundant check bits. This redundant information has a certain connection with the actual data, so that, when errors occur, the data can be reconstructed again. The redundant information is known as the �errorcorrection code�. As a simple example, all data could be transmitted twice, which would give a redundancy of 100%. By comparing both versions, or by CRC, errors could easily be detected, and if some word were erroneous, its counterpart could be used to give the correct data.
Overview of the challenges and solutions for 5G channel coding schemes
Published in Journal of Information and Telecommunication, 2021
Madhavsingh Indoonundon, Tulsi Pawan Fowdur
Basically, lower PDSCH code-rate transmissions provide better error performances at a trade-off of the maximum achievable throughput due to the increased proportion of channel coding bits transmitted along with the information bits.