Bit-interleaved coded modulation

The principle of coding in the signal space follows directly from Shannon’s analysis of waveform Gaussian channels subject to an input constraint. The early design of communication systems focused separately on modulation, and error correcting codes. Bit-interleaved coded modulation (BICM) is a pragmatic approach combining the best out of both worlds: it takes advantage of the signal-space coding perspective, whilst allowing for the use of powerful families of binary codes with virtually any modulation format. As matter of fact, has established itself as a quasi-standard (de-facto) for bandwidth - and power - efficient communication, like DSL, wireless LANs, WiMax. The aim of this thesis is to describe the main aspects of the system, focusing the attention on model characteristics and on the error analysis (based on bit-error rate approximations). Finally I also consider the BICM with iterative decoding and I conclude with an overview of some applications of BIC

Book Review: A Conceptual Review of “Digital Communication Systems”

(Author: Simon Haykin, 2014)Haykin, S. 2014. Digital Communication Systems.John Wiley & Sons, Inc., Hoboken, NJ, USA.Available: <http://www.wiley.com/WileyCDA/WileyTitle/productCd-EHEP001809.html>

Forward Error Correction for High Capacity Transmission Systems

Αυτή η μελέτη διερευνά την αλληλεπίδραση μεταξύ FEC διόρθωσης σφαλμάτων προώθησης και ψηφιακού αντιστάθμιση μη γραμμικότητας DBP σε ένα κανάλι ινών μεγάλων αποστάσεων. Πρώτον, α Η προσέγγιση που βασίζεται στην έρευνα χρησιμοποιείται για τον προσδιορισμό των τεχνολογιών αιχμής στο FEC για το κανάλι ινών και προσαρμόστε τα στο τελικό σχέδιο. Οι σχεδιαστικές επιλογές περιλαμβάνουν το χρήση τετριμμένων bit κωδικοποιημένης διαμόρφωσης αρχιτεκτονικής T-BICM με συνενωμένη σχήμα κώδικα που χρησιμοποιεί έναν επαναληπτικό soft αποκωδικοποιητή. Η απαίτηση για συνενωμένη Η εφαρμογή FEC οδήγησε σε μια άλλη έρευνα για έναν κώδικα καλής απόδοσης συνδυασμός. Το ακανόνιστο LDPC και το οιονεί κυκλικό QC-LDPC, που υιοθετήθηκαν από το DVB-S2 και Τα πρότυπα IEEE 802.11, αντίστοιχα, συνδυάστηκαν με τον κώδικα σκάλας και σύγκριση με βάση τις επιτευχθείσες επιδόσεις. Αποδεικνύουμε ότι αυξάνοντας τις ίνες απόσταση μετάδοσης κατά 1/3, από 300km έως 400km, διατηρώντας παράλληλα την η ίδια απόδοση και η χρήση των ίδιων γενικών εξόδων, δηλαδή 27,5% είναι εφικτό όταν υλοποίηση του DBP με 2 βήματα/περιοχή ή 3 βήματα/περιοχή, ανάλογα με το αν το Οι επαναλήψεις αποκωδικοποίησης είναι 10 ή 5. Αυτή η μελέτη καταλήγει με την εύνοια του LDPC από το DVB-S2 πάνω από το QC-LDPC του IEEE 802.11 για κανάλι ινών μεγάλων αποστάσεων. Το συμπέρασμα βγαίνει με βάση σχετικά με την καλύτερη απόδοση για το LDPC-DVB, λόγω των μεγάλων μηκών κωδικών του και του υποστήριξη για υψηλούς ρυθμούς κωδικοποίησης με αποτέλεσμα χαμηλές γενικές απαιτήσειςThis study investigates the interplay between forward error correction FEC and digital back-propagation DBP nonlinearity compensation on a long-haul fibre channel. First, a research-based approach is used to identify the state-of-the-art technologies in FEC for the fibre channel and adapt them to the final design. The design choices includes the usage of trivial bit interleaved coded modulation T-BICM architecture with a concatenated code scheme that uses an iterative soft decoder. The requirement for a concatenated FEC implementation motivated another investigation of a well-performing code combination. The Irregular LDPC and quasi-cyclic QC-LDPC, adopted from DVB-S2 and IEEE 802.11 standards, respectively, were each concatenated with staircase code and compared based on the attained performance. We prove that increasing the fibre transmission distance by a factor of 1/3, from 300km to 400km, while maintaining the same performance and using the same overhead, i.e. 27.5\% is achievable when implementing DBP with 2 steps/span or 3 steps/span, depending on whether the decoding iterations are 10 or 5. This study concludes with favouring LDPC from DVB-S2 over IEEE 802.11's QC-LDPC for long haul fibre channel. The conclusion is made based on the better attained performance for LDPC-DVB, due to its long code lengths, and its support for high coding rates resulting low overhead requirement

Spectrally and Energy Efficient Wireless Communications: Signal and System Design, Mathematical Modelling and Optimisation

This thesis explores engineering studies and designs aiming to meeting the requirements of enhancing capacity and energy efficiency for next generation communication networks. Challenges of spectrum scarcity and energy constraints are addressed and new technologies are proposed, analytically investigated and examined. The thesis commences by reviewing studies on spectrally and energy-efficient techniques, with a special focus on non-orthogonal multicarrier modulation, particularly spectrally efficient frequency division multiplexing (SEFDM). Rigorous theoretical and mathematical modelling studies of SEFDM are presented. Moreover, to address the potential application of SEFDM under the 5th generation new radio (5G NR) heterogeneous numerologies, simulation-based studies of SEFDM coexisting with orthogonal frequency division multiplexing (OFDM) are conducted. New signal formats and corresponding transceiver structure are designed, using a Hilbert transform filter pair for shaping pulses. Detailed modelling and numerical investigations show that the proposed signal doubles spectral efficiency without performance degradation, with studies of two signal formats; uncoded narrow-band internet of things (NB-IoT) signals and unframed turbo coded multi-carrier signals. The thesis also considers using constellation shaping techniques and SEFDM for capacity enhancement in 5G system. Probabilistic shaping for SEFDM is proposed and modelled to show both transmission energy reduction and bandwidth saving with advantageous flexibility for data rate adaptation. Expanding on constellation shaping to improve performance further, a comparative study of multidimensional modulation techniques is carried out. A four-dimensional signal, with better noise immunity is investigated, for which metaheuristic optimisation algorithms are studied, developed, and conducted to optimise bit-to-symbol mapping. Finally, a specially designed machine learning technique for signal and system design in physical layer communications is proposed, utilising the application of autoencoder-based end-to-end learning. Multidimensional signal modulation with multidimensional constellation shaping is proposed and optimised by using machine learning techniques, demonstrating significant improvement in spectral and energy efficiencies

Reduced Receivers for Faster-than-Nyquist Signaling and General Linear Channels

Fast and reliable data transmission together with high bandwidth efficiency are important design aspects in a modern digital communication system. Many different approaches exist but in this thesis bandwidth efficiency is obtained by increasing the data transmission rate with the faster-than-Nyquist (FTN) framework while keeping a fixed power spectral density (PSD). In FTN consecutive information carrying symbols can overlap in time and in that way introduce a controlled amount of intentional intersymbol interference (ISI). This technique was introduced already in 1975 by Mazo and has since then been extended in many directions. Since the ISI stemming from practical FTN signaling can be of significant duration, optimum detection with traditional methods is often prohibitively complex, and alternative equalization methods with acceptable complexity-performance tradeoffs are needed. The key objective of this thesis is therefore to design reduced-complexity receivers for FTN and general linear channels that achieve optimal or near-optimal performance. Although the performance of a detector can be measured by several means, this thesis is restricted to bit error rate (BER) and mutual information results. FTN signaling is applied in two ways: As a separate uncoded narrowband communication system or in a coded scenario consisting of a convolutional encoder, interleaver and the inner ISI mechanism in serial concatenation. Turbo equalization where soft information in the form of log likelihood ratios (LLRs) is exchanged between the equalizer and the decoder is a commonly used decoding technique for coded FTN signals. The first part of the thesis considers receivers and arising stability problems when working within the white noise constraint. New M-BCJR algorithms for turbo equalization are proposed and compared to reduced-trellis VA and BCJR benchmarks based on an offset label idea. By adding a third low-complexity M-BCJR recursion, LLR quality is improved for practical values of M. M here measures the reduced number of BCJR computations for each data symbol. An improvement of the minimum phase conversion that sharpens the focus of the ISI model energy is proposed. When combined with a delayed and slightly mismatched receiver, the decoding allows a smaller M without significant loss in BER. The second part analyzes the effect of the internal metric calculations on the performance of Forney- and Ungerboeck-based reduced-complexity equalizers of the M-algorithm type for both ISI and multiple-input multiple-output (MIMO) channels. Even though the final output of a full-complexity equalizer is identical for both models, the internal metric calculations are in general different. Hence, suboptimum methods need not produce the same final output. Additionally, new models working in between the two extremes are proposed and evaluated. Note that the choice of observation model does not impact the detection complexity as the underlying algorithm is unaltered. The last part of the thesis is devoted to a different complexity reducing approach. Optimal channel shortening detectors for linear channels are optimized from an information theoretical perspective. The achievable information rates of the shortened models as well as closed form expressions for all components of the optimal detector of the class are derived. The framework used in this thesis is more general than what has been previously used within the area