Characteristics of multi-h coded modulation

Includes bibliographical references (leaves 74-75).Multi-h Coded Continuous-Phase Frequency Shift Keying (Multi-h CPFSK) has gained interest in recent years because it offers an additional degree of freedom in the coding of CPFSK. Similar to Trellis Coded Modulation (TCM), it does not use redundancy to achieve coding gain. Hence with properly chosen modulation indices, impact to spectral occupancy is kept to a minimum. While there has been less attention given of this method as compared with TCM, this method can also be used with data coding. In cases where data coding is to be implemented, simultaneous use of Multi-h coding can be implemented with very little increase in complexity. In this thesis, a thorough mathematical review of this technique is made. A multi-oscillator multih coded modulator is shown similar to one presented by Massey for MSK. A unique analytical tool called a multi-oscillator trellis is presented. This considers the phase transitions with respect to each of the signalling frequencies instead of the center frequency, f₀. The multi-oscillator trellis is used to determine the state machine that will switch a bank of oscillators. The purpose of the state machine is to maintain continuous phase at the multi-oscillator output while generating the proper signal frequencies according to the data and modulation index. The Maximum Likelihood Detection process at the receiver is shown as a partition of an uncoded CPFSK signal. Finally, an analysis is made to determine if a modulator with a non-linear frequencyvoltage characteristic is suitable in a coherent multi-h coded application. Much of the literature on this topic has been comparative to PSK. It is the intent of this work to use FSK and MSK as the baseline to determine how existing structures may be extended to realize the benefits of multi-h coding. The application of this coding to an 8 Mbps 23 GHz CPFSK point-to-point terrestrial communications system is also a topic of this thesis. It is in this context that the analysis is made

Efficient Decompression of Binary Encoded Balanced Ternary Sequences

International audienceA balanced ternary digit, known as a trit, takes its values in {-1, 0, 1}. It can be encoded in binary as {11, 00, 01} for direct use in digital circuits. In this correspondence, we study the decompression of a sequence of bits into a sequence of binary encoded balanced ternary digits. We first show that it is useless in practice to compress sequences of more than 5 ternary values. We then provide two mappings, one to map 5 bits to 3 trits and one to map 8 bits to 5 trits. Both mappings were obtained by human analysis and lead to Boolean implementations that compare quite favorably with others obtained by tweaking assignment or encoding optimization tools. However, mappings that lead to better implementations may be feasible

Space-Time Codes Technology

Space-time codes technology is a channel coding for wireless digital communications, where multiple antennas are employed. It improves the capacity of the transmission as well as reducing errors. Also, this technology does not require the expansion of bandwidth or time slots. In order to achieve the highest efficiency, we have to first investigate the maximum efficiency that can be achieved. Then, the code design criteria for obtaining the maximum efficiency have to be derived. Last, the code design approaches have to be proposed. The article discusses those procedures

Binary Continuous Phase Modulations Robust to a Modulation Index Mismatch

International audienceWe consider binary continuous phase modulation (CPM) signals used in some recent low-cost and low-power consumption telecommunications standard. When these signals are generated through a low-cost transmitter, the real modulation index can end up being quite different from the nominal value employed at the receiver and a significant performance degradation is observed, unless proper techniques for the estimation and compensation are employed. For this reason, we design new binary schemes with a much higher robustness. They are based on the concatenation of a suitable precoder with binary input and a ternary CPM format. The result is a family of CPM formats whose phase state is constrained to follow a specific evolution. Two of these precoders are considered. We will discuss many aspects related to these schemes, such as the power spectral density, the spectral efficiency, simplified detection, the minimum distance, and the uncoded performance. The adopted precoders do not change the recursive nature of CPM schemes. So these schemes are still suited for serial concatenation, through a pseudo-random interleaver, with an outer channel encoder

One and Two Bit Message Passing for SC-LDPC Codes with Higher-Order Modulation

Low complexity decoding algorithms are necessary to meet data rate requirements in excess of 1 Tbps. In this paper, we study one and two bit message passing algorithms for belief propagation decoding of low-density parity-check (LDPC) codes and analyze them by density evolution. The variable nodes (VNs) exploit soft information from the channel output. To decrease the data flow, the messages exchanged between check nodes (CNs) and VNs are represented by one or two bits. The newly proposed quaternary message passing (QMP) algorithm is compared asymptotically and in finite length simulations to binary message passing (BMP) and ternary message passing (TMP) for spectrally efficient communication with higher-order modulation and probabilistic amplitude shaping (PAS). To showcase the potential for high throughput forward error correction, spatially coupled LDPC codes and a target spectral efficiency (SE) of 3 bits/QAM symbol are considered. Gains of about 0.7 dB and 0.1 dB are observed compared to BMP and TMP, respectively. The gap to unquantized belief propagation (BP) decoding is reduced to about 0.75 dB. For smaller code rates, the gain of QMP compared to TMP is more pronounced and amounts to 0.24 dB in the considered example.Comment: Accepted for IEEE/OSA Journal on Lightwave Technolog