The Utility of Coded Multilevel Communications Systems

A design tool, called the Utility Chart, was introduced at this Congress in 1967. It is based on the utility, a definition of the efficiency of a communications link. The utility relates the normalized transmission rate (bit density) to the signal-to-noise ratio. This kind of definition of the communications efficiency is based on a paper by R. W. Sanders published in I960 . The definition has been modified to meet more closely the requirements of practical communications designers. The present paper compares the various methods of coded multilevel communications systems with the help of the utility chart. Coded communications is a term introduced by Viterbi in 1959. This term is generally used to designate all kinds of digital communications systems that translate a set of input messages into a set of transmission messages. The translation rule is called a code or, more specifically, a code book

Analysis of Various Algorithmic approaches to Software-Based 1200 Baud Audio Frequency Shift Keying Demodulation for APRS

Digital communications continues to be a relevant Field of study as new technologies appear and old methodologies get revisited or renovated. The goal of this research is to look into the old digital communication scheme of Bell 202 [67] used by APRS and improve software based demodulation performance. Improved performance is defined by being able to correctly decode more packets in an efficient, real time, manner. Most APRS demodulation is currently done using specialized hardware since that yields the best performance. This research shows that through using Sivan Toledo\u27s javAX25 [72] software package, new demodulation algorithms can be implemented that decode more Bell 202 encoded AX.25 packets than the existing software could. These improvements may help drive the adoption of software demodulation since it is a low cost alternative to specialized hardware

A case study on the communications subsystem for cubesat

Due to the overwhelming increment transmission and reception of information around the world, Satellite Communications have become an essential application in our lives. Proof of this, are the continuous investments made by technology companies to develop new and improved communication satellite systems. This project focuses on the transmission of data, from the different meteorological stations placed all around Brazil, to the Cubesats set in the brazilian satellites (SCD‐1,SCD-­2 and CBERS). It also studies the reception in the Cubesat, and the transmission of all the information accumulated to the main reception Station in Cuiabá. The main objective of this simulation evaluation is to determine the Bit Error Rate performance of the models with different modulations and convolutional code in a noisy communication channel. M-­Ary Phase Shift Keying (M-PSK) and Gaussian Minimum Shift Keying (GMSK) modulation techniques are used for this simulation evaluation of the coded communication system. For the model based simulation evaluation the MATLAB/SIMULINK is chosen as the investigating tool. Monte Carlo method of simulation is used for plotting the results in between Bit Error Rate (BER) and Signal to Noise ratio (Eb/No)

Software and hardware implementation techniques for digital communications-related algorithms

There are essentially three areas addressed in the body of this thesis. (a) The first is a theoretical investigation into the design and development of a practically realizable implementation of a maximum-likelihood detection process to deal with digital data transmission over HF radio links. These links exhibit multipath properties with delay spreads that can easily extend over 12 to 15 milliseconds. The project was sponsored by the Ministry of Defence through the auspices of the Science and Engineering Research Council. The primary objective was to transmit voice band data at a minimum rate of 2.4 kb/s continuously for long periods of time during the day or night. Computer simulation models of HF propagation channels were created to simulate atmospheric and multipath effects of transmission from London to Washington DC, Ankara, and as far as Melbourne, Australia. Investigations into HF channel estimation are not the subject of this thesis. The detection process assumed accurate knowledge of the channel. [Continues.

Adaptive equalizers for multipath compensation in digital microwave communications

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Constellation Shaping for Bit-Interleaved LDPC Coded APSK

An energy-efficient approach is presented for shaping a bit-interleaved low-density parity-check (LDPC) coded amplitude phase-shift keying (APSK) system. A subset of the interleaved bits output by a binary LDPC encoder are passed through a nonlinear shaping encoder whose output is more likely to be a zero than a one. The "shaping" bits are used to select from among a plurality of subconstellations, while the unshaped bits are used to select the symbol within the subconstellation. Because the shaping bits are biased, symbols from lower-energy subconstellations are selected more frequently than those from higher-energy subconstellations. An iterative decoder shares information among the LDPC decoder, APSK demapper, and shaping decoder. Information rates are computed for a discrete set of APSK ring radii and shaping bit probabilities, and the optimal combination of these parameters is identified for the additive white Gaussian noise (AWGN) channel. With the assistance of extrinsic-information transfer (EXIT) charts, the degree distributions of the LDPC code are optimized for use with the shaped APSK constellation. Simulation results show that the combination of shaping, degree-distribution optimization, and iterative decoding can achieve a gain in excess of 1 dB in AWGN at a rate of 3 bits/symbol compared with a system that does not use shaping, uses an unoptimized code from the DVB-S2 standard, and does not iterate between decoder and demodulator.Comment: to appear in IEEE Transactions on Communication

The design and application of power line carrier communication and remote meter reading for use in integrated services and broadband - integrated services digital networks

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