In this thesis, we compute the distance spectrum for non-causal generating signals and compare the different spectrum effects for different non-causal systems. The non-causal system is the system which the present output is determined by the future and the past. The distance spectrum is the list of the difference measures of any two signals and search through all the possible event paths by trellis as much as possible. We use the method of the line difference to compute the distance spectrum of non-causal generating signal systems by defining the line and the line difference to find the distance for every pair of signals. Using this method, we have computed the distance spectrum for non-causal generating signals. Finally, we compare the different spectrums for different non-causal systems of different coefficients.

Τα τελευταία χρόνια ο όγκος των δεδομένων που διακινείται μέσω δικτυακών συστημάτων είναι συνεχώς αυξανόμενος με την επιτακτική ανάγκη για αξιόπιστη επικοινωνία. Παρόλο που η εξέλιξη της τεχνολογίας επιτρέπει μεγαλύτερη ανοχή σε παρεμβολές στο τηλεπικοινωνιακό κανάλι, ο υψηλότερος ρυθμός δεδομένων προκαλεί παραμορφώσεις στο σήμα και κάνει το τηλεπικοινωνιακό σύστημα πιο επιρρεπές στον θόρυβο. Παράδειγμα τέτοιων συστημάτων αποτελούν εφαρμογές ασύρματων δικτύων όπως τα συστήματα κινητής τηλεφωνίας, οι δορυφορικές επικοινωνίες, ασύρματα τοπικά δίκτυα WiFi καθώς και ενσύρματων επικοινωνιών (ενσύρματα Modem). Η παρούσα διπλωματική επικεντρώνεται στα πρότυπα 802.11 που αφορούν ασύρματα τοπικά δίκτυα και πιο συγκεκριμένα στο πρόσφατο 802.11ac ώστε να τεθούν συγκεκριμένα κριτήρια απόδοσης. Αφενός γίνεται σχεδιασμός και υλοποίηση ενός αποκωδικοποιητή σύμφωνου με το πρότυπο λαμβάνοντας υπόψη περιορισμούς χρονισμού αλλά και επιφάνειας και επαλήθευση αυτών μέσω τεχνολογιών FPGA και ASIC. Αφετέρου μελετώνται διαφορετικές αρχιτεκτονικές υλοποίησης του αλγορίθμου (πχ high radix) και εξετάζονται τα πιθανά σχεδιαστικά trade-off. Εξετάζονται μέθοδοι αύξησης του throughput αλλά και θέματα απόδοσης που αφορούν την ικανότητα διόρθωσης λαθών. / In recent years the volume of data handled by network systems is growing with the need for reliable communication . Although the evolution of technology allows greater tolerance to interference in the telecommunication channel , higher data rate causes distortion to the signal and makes the telecommunication system more susceptible to noise. Examples of such systems are applications of wireless networks such as cellular systems , satellite communications , wireless local area networks WiFi and wired communications ( wired Modem). This thesis focuses on the 802.11 standards regarding wireless LANs and in particular in recent 802.11ac to put specific performance criteria. First is design and implementation of a decoder conforming to the model taking into account timing and surface constraints and verification technologies through FPGA and ASIC. Secondly, different architectures of the algorithm ( eg high radix) are studied and the possible design trade-off is examined. Methods of increasing the throughput and performance issues relating to error correction capability are examined.

Ever since the proposal of turbo code in 1993, there has been extensive research carried out to improve both the performance and spectrum efficiency. One of the methods used to improve the spectrum efficiency was to combine turbo code with a trellis-coded modulation scheme, called turbo trellis-coded modulation (TTCM). The scheme is used in various applications such as deep-space communication, wireless communication and other fields. It is a well established fact that an increase in an interleaver size of a TTCM system results in an improved performance in the bit error rate (BER). In this thesis repeat-punctured turbo trellis-coded modulation (RPTTCM) is proposed. In RPTTCM, the effect of repeat-puncture is investigated on a TTCM system, repetition of the information bits increases the interleaver size, followed by an appropriate puncturing scheme to maintain the respective code rate. The TTCM and RPTTCM systems are simulated in an Additive White Gaussian Noise (AWGN) channel. To understand how the RPTTCM scheme will perform in a wireless channel, the Rayleigh flat fading channel (with channel state information known at the receiver) will be used. The BER performance bound for the TTCM scheme is derived for AWGN and Rayleigh flat fading channels. Thereafter repeat-punctured is introduced into the TTCM system. The BER performance bound is then extended to include repeat-puncturing. The performances of the TTCM and RPTTCM systems are then compared. It was found that the RPTTCM system performed better at high signal-to-noise ratio (SNR) in both AWGN and Rayleigh flat fading channels. The RPTTCM scheme achieved a coding gain of approximately 0.87 dB at a BER of for an AWGN channel and 1.9 dB at a BER of for a Rayleigh flat fading channel, for an information size of N=800. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.

No description available.

Demand for capacity in wireless communication systems has been rapidly growing world- wide. This has been driven by increasing data rate requirements of cellular mobile systems, and demand for wireless Internet and multimedia services. As the available radio spec- trum is limited, higher data rates can only be achieved by designing more efficient signaling techniques. In this thesis, we propose a new transmission scheme, which benefits from the advantages of conventional space-time trellis codes (CSTTCs) but does not have the disadvantages, especially for larger signal constellations. We achieve this by developing a new class of codes, called Multilevel Space-Time Trellis Codes (IMLSTTC). The new scheme provides a scalable and promising alternative to CSTTCs, by providing the system designer with the flexibility to choose any desired balance between code performance, complexity and throughput. The proposed scheme outperforms layered schemes at high SNRs, using a smaller number of antennas.

Thesis (Ph. D.)--Ohio University, November, 2003. / Title from PDF t.p. Includes bibliographical references (leaves 84-85).

Thesis (M.E.)--University of Canterbury, 2008. / Typescript (photocopy). "June 2008." Includes bibliographical references (p. 87-96). Also available via the World Wide Web.

Thesis (M. App. Sc.)--Carleton University, 2004. / Includes bibliographical references (p. 52-55). Also available in electronic format on the Internet.

Thesis (M.S)--Ohio University, March, 2005. / Includes bibliographical references (p. 44-45)

Thesis (M.S)--Ohio University, March, 2005. / Title from PDF t.p. Includes bibliographical references (p. 44-45)