International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / Digital modulation schemes that are power and bandwidth efficient are highly desirable. After non-linear amplification has been done, signal modulation schemes having constant or quasi-constant envelopes are not as susceptible to spectral regrowth as those with non-constant envelopes. Since such distortion generates interference in the adjacent channels, the power operation of the amplifier in non-constant envelope modulations is typically backed off, resulting in systems with reduced power efficiency. On the other hand, constant envelope modulation may have different bandwidth spectra. This paper examines the statistical characteristics of N-GMSK and N-FQPSK [1] signals to assess the bandwidth efficiency in the presence of amplifier nonlinearities.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Bandwidth is a precious commodity. In order to make the best use of what is available, better modulation schemes need to be developed, or less data needs to be sent. This paper will investigate the option of sending less data via data compression. The structure and the entropy of the data determine how much lossless compression can be obtained for a given set of data. This paper shows the data structure and entropy for several actual telemetry data sets and the resulting lossless compression obtainable using data compression techniques.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / In this paper, we extended the matched filter bound (MFB) of time-discrete multipath Rayleigh fading channels derived in [1,2] for multiscale wavelet signaling communication.

International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / Shaped Offset QPSK (SOQPSK), as proposed and analyzed by Terrance Hill, is a family of constant envelope waveforms that is non-proprietary and exhibits excellent spectral containment and detection efficiency. Results for two variants, defined as SOQPSK-A and -B, have previously been presented. However, it remains to be seen whether or not even more attractive choices exist. This paper explores the bandwidth and power efficiency trade-offs of the entire SOQPSK family using computer simulations and analytical performance bounds.

International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The greatest threat to the DOD Test and Training Test Centers is the loss of the Radio Frequency (RF) spectrum used in transmitting digital data generated by the test instrumentation during the evaluation of weapon systems. The T&E ranges use the RF spectrum for data generated by status reporting, GPS/TSPI, telemetry, target control, range safety, situational awareness, video, voice communication, etc. In the past the ranges developed their data links independently of one another. The Flexible Interoperable Transceiver (FIT) Data Link Standard identifies protocols and technology that provides for interoperability and spectral efficiency, and can be applied to most RF transmission requirements at the test ranges and training centers.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / Shaped BPSK (SBPSK) and Shaped Offset QPSK (SOQPSK), as defined in various MIL standards, are widely employed on SATCOM links because they offer an attractive combination of good spectral efficiency, constant envelope characteristics, and interoperability with legacy equipments. More recently, numerous terrestrial applications of OQPSK and similar waveforms (Feher-patented FQPSK) have been proposed. The present paper describes a simple non-proprietary modification of the MIL-STD SOQPSK waveform which offers spectral containment and detection efficiency comparable to or better than FQPSK-B (Revision A1), while preserving a constant envelope characteristic and backward compatibility with existing equipment.

Η παρούσα διπλωματική εργασία εκπονήθηκε στο Εργαστήριο Ασύρματης Τηλεπικοινωνίας του τμήματος Ηλεκτρολόγων Μηχανικών και Τεχνολογίας Υπολογιστών. Ο στόχος της εργασίας αυτής ήταν η μελέτη της προκαλούμενης βελτίωσης στην απόδοση εύρους ζώνης με χρήση πολλαπλών συστημάτων HAPS σε κοινή περιοχή κάλυψης. Με γνώμονα τη συνεχώς αυξανόμενη ανάγκη του σύγχρονου ανθρώπου για ευρυζωνικές υπηρεσίες υψηλών ταχυτήτων σε περιοχές οι οποίες είναι φτωχές σε τηλεπικοινωνιακή κάλυψη καθώς και σε περιοχές με αυξημένη τηλεπικοινωνιακή κίνηση καταλήγουμε στο συμπέρασμα ότι οι τηλεπικοινωνίες με τη χρήση εναέριων πλατφορμών (HAPS) οι οποίες δρουν σε πολύ χαμηλότερο ύψος από τους δορυφόρους και με σημαντικά μικρότερες ισχείς , αποτελούν μια πολλά υποσχόμενη τεχνολογία για τα επόμενα χρόνια. Σημαντικός παράγων στον οποίο βασίζεται οι τεχνολογία των HAPS είναι η εξοικονόμηση του φάσματος συχνοτήτων με τη χρήση κοινής συχνότητας εκπομπής από όλες τις πλατφόρμες , γεγονός που οδηγεί βαθμιαία σε αύξηση των παρεμβολών που λαμβάνουν οι χρήστες. Στόχος μας ήταν να προσδιορίσουμε τις κατάλληλες συνθήκες και παραμέτρους ώστε ο χρήστης στο έδαφος να λαμβάνει έναν ικανοποιητικό λόγο σήματος προς θόρυβο συν παρεμβολές (CINR) ώστε να υπάρχει επαρκές εύρος ζώνης για τις τηλεπικοινωνιακές του ανάγκες. Για την εξαγωγή των γραφικών παραστάσεων χρησιμοποιήθηκε το πρόγραμμα Matlab R2010b. / This diploma thesis was developed at the Laboratory of Wireless Communications, at the Department of Electrical an Computer Engineering. The objective of this work was to study the improvement in the bandwidth efficiency that occurs by using multiple high-altitude-platformsystems (HAPS) serving a common coverage area. Considering the even increasing need of the modern people for high speed broadband applications in areas that have poor telecommunication coverage and also in areas that have an increased telecommunication traffic we came to the conclusion that the use of the HAPS operating in lower altitude comparing to the satellites and using even lower power levels, is a very promising technology for the years to come. A very important factor on which the HAPS technology is based on is the saving of the frequency spectrum by using the same transmission frequency from all the platforms, a fact that leads to an increasing interference level that the users receive. Our goal was to determine the proper conditions and parameters so as to the users on the ground receive a satisfying level of CINR in order to have enough bandwidth efficiency for his telecommunication needs. In order to export the graphics, we used Matlab R2010b.

International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / A new constant envelope modulation scheme and architecture for QPSK by cubic spline interpolation methods which increase spectral efficiency and power efficiency, named FQPSK-L, is presented. This modulation technique is an extension of the Feher Quadrature Shift Keying (FQPSK) patented technologies, see Ref [1]. Being a constant envelope modulation, FQPSK-L can operate with class C power amplifier without spectrum regrowth. We achieve a more compact spectrum with comparable bit error rate performance. For example, FQPSK-L is about 20% more spectral efficient than GMSK BTb=0.3 from 40 to 70 dB attenuation point. Moreover, FQPSK-L intrinsically has spikes at fc ± 0.5fb, fc ± 1.0fb, fc ± 1.5fb, ... which are useful for carrier recovery, symbol time recovery and fading compensation. In Rayleigh fading channel, FQPSK-L outperform GMSK BTb=0.3 by 0.8 dB. FQPSK-L is an excellent scheme for wireless and satellite communications which require high spectral and power efficiency.

International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The aeronautical telemetry community is investigating alternative modulation methods to the commonly used non-return-to-zero (NRZ) pulse code modulation (PCM)/frequency modulation (FM). This paper outlines the important characteristics being investigated. Measured data comparing the spectral occupancy and bit error probability (BEP) performance of PCM/FM with that of a prototype constant envelope Feher’s quadrature phase shift keying (FQPSK) modulator and demodulator will also be presented. Measured results in several radio frequency bands demonstrate that the 99.99% and -60 dBc bandwidths of filtered FQPSK are only approximately one-half of the corresponding bandwidths of optimized PCM/FM even when the signal is non-linearly amplified. The signal energy per bit to noise power spectral density (E /N ) required for a BEP of 1×10 b 0 -5 for non-optimized FQPSK was approximately 12 dB which is approximately the same as limiter discriminator detected PCM/FM.

International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / A new constant envelope modulation scheme for OQPSK, called FQPSK-O, is presented. This modulation technique is an extension of the Feher Quadrature Shift Keying (FQPSK) patented technologies, see Ref[l]. This scheme uses cubic spline interpolation to generate very smooth baseband waveforms in order to increase the spectral and power efficiency. Being a constant envelope modulation, FQPSK-O can operate with class C power amplifier without spectrum regrowth. We achieve a more compact spectrum with comparable bit error rate performance. For example, the spectrum of FQPSK-O is 25% narrower than that of GMSK with BT(b)=0.3 and FQPSK-1 with hardlimiter [2] at -40 dB attenuation point. For coherent demodulation under AWGN channel, FQPSK-O has almost the same BER performance as FQPSK-1 with hardlimiter. Both of them are better than GMSK with BT(b)=0.3 for BER < 10^-4. In Rayleigh fading channel, FQPSK-O outperforms GMSK with BT(b)=0.3 by 2 dB. FQPSK-O is an excellent scheme for wireless and satellite communications which require high spectral and power efficiency.