Symbol timing recovery for GMSK modulation based on squaring algorithm

A new all-digital symbol timing estimator for GMSK signals is proposed. It is based on the squaring algorithm and has a feedforward structure. Performance in AWGN channel is assessed by computer simulation, and is compared with the modified Cramer-Rao bound and other existing algorithms. The performance of the proposed estimator is shown to be close to that of ML algorithm.published_or_final_versio

A Pan-Function Model for the Utilization of Bandwidth Improvement and PAPR Reduction

Aiming at the digital quadrature modulation system, a mathematical Pan-function model of the optimized baseband symbol signals with a symbol length of 4T was established in accordance with the minimum out-band energy radiation criterion. The intersymbol interference (ISI), symbol-correlated characteristics, and attenuation factor were introduced to establish the mathematical Pan-function model. The Pan-function was added to the constraints of boundary conditions, energy of a single baseband symbol signal, and constant-envelope conditions. Baseband symbol signals with the optimum efficient spectrum were obtained by introducing Fourier series and minimizing the Pan-function. The characteristics of the spectrum and peak-to-average power ratio (PAPR) of the obtained signals were analyzed and compared with the minimum shift keying (MSK) and quadrature phase-shift keying (QPSK) signals. The obtained signals have the characteristics of a higher spectral roll-off rate, less out-band radiation, and quasi-constant envelope. We simulated the performance of the obtained signals, and the simulation results demonstrate that the method is feasible

Design And Realization Of Gmsk Modem

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2006Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2006Bu çalısmada, GMSK modülatörü ve demodülatörünün tasarımı yapılmıstır.Genel sayısal haberlesme teknikleri anlatılmıstır. Bazı modülasyon türleri ele alınmıstır. GMSK modülasyonu detaylı olarak anlatılmıstır. Sistem, modülatör ve demodülatör, MATLAB de modellenmistir. Haberlesme sistemlerinde önemli olan, gürültü, çok yollu sönme, kanallar arası girisim olguları MATLAB de modellenip simule edilmistir. Tüm sistemin performansı simule edilmistir. Haberlesme asenkron olarak gerçeklestiğinden dolayı, örnekleme zaman hataları ve frekans hatalarını karsılamak için senkronizasyon yapılmıstır. Tasarlanan modem TI 5509 sayısal isaret islemcisinde kodlanmıstır.In this study design of a GMSK modulator and demodulator is done. General digital communication techniques are described. Some modulation schemes are explained. The GMSK modulation is explained in detail. The system, modulator and demodulator, is modelled by MATLAB. The tasks concerning communication systems such as noise, multipath fading and co-channel interference is modelled and simulated by MATLAB. Overall system performance of the modem is evaluated. As the communication is done in an asynchronous manner, synchronization is utilized in order to compansate for sampling timing errors and frequency offsets. The designed modem is coded on a TI 5509 DSP chipset.Yüksek LisansM.Sc

Non-data aided digital feedforward timing estimators for linear and nonlinear modulations

We propose to develop new non-data aided (NDA) digital feedforward symbol timing estimators for linear and nonlinear modulations, with a view to reducing the sampling rate of the estimators. The proposed estimators rely on the fact that sufficient statistics exist for a signal sampled at the Nyquist rate. We propose an ad hoc extension to the timing estimator based on the log nonlinearity which performs better than existing estimators at this rate when the operating signal-to-noise ratio (SNR) and the excess bandwidth are low. We propose another alternative estimator for operating at the Nyquist rate that has reduced self-noise at high SNR for large rolloff factors. This can be viewed as an extension of the timing estimator based on the square law nonlinearity. For continuous phase modulations (CPM), we propose two novel estimators that can operate at the symbol rate for MSK type signals. Among the class of NDA feedforward timing estimators we are not aware of any other estimator that can function at symbol rate for this type of signals. We also propose several new estimators for the MSK modulation scheme which operate with reduced sampling rate and are robust to carrier frequency offset and phase offset