LDPC Coded OFDM And It's Application To DVB-T2, DVB-S2 And IEEE 802.16e

ABSTRACT: Since the invention of Information Theory by Shannon in 1948, coding theorists have been trying to come up with coding schemes that will achieve capacity dictated by Shannon’s Theorem. The most successful two coding schemes among many are the LDPCs and Turbo codes. In this thesis, we focus on LDPC codes and in particular their usage by the second generation terrestrial digital video broadcasting (DVB-T2), second generation satellite digital video broadcasting (DVB-S2) and IEEE 802.16e mobile WiMAX standards. Low Density Parity Check (LDPC) block codes were invented by Gallager in 1962 and they can achieve near Shannon limit performance on a wide variety of fading channels. LDPC codes are included in the DVB-T2 and DVB-S2 standards because of their excellent error-correcting capabilities. LDPC coding has also been adopted as an optional error correcting scheme in IEEE 802.16e mobile WiMAX. This thesis focuses on the bit error rate (BER) and PSNR performance analysis of DVB-T2, DVB-S2 and IEEE 802.16e transmission using LDPC coding under additive white Gaussian noise (AWGN) and Rayleigh Fading channel scenarios. The power delay profile for all transmissions was adopted from the ITU channel model. For modelling the fading environment, Jakes fading channel model[7] together with ITU Vehicular-A and ITU Vehicular-B[13] power delay profile parameters were used considering also the Doppler effect. The three scenarios presented in this thesis are the following: (i) simulation of LDPC coding for DVB-S2 standard, (ii) optional LDPC coding as suggested by the WiMAX standard and (iii) simulation of DVB-T2 using LDPC without outer BCH encoder and with outer BCH encoder. During the simulations the encoding algorithm used was the Forward Substitution algorithm. Even though the second generation DVB standards and WiMAX standard has been out since 2009, not many comparative results have been published for BCH and LDPC concatenated coding schemes making use of either a normal FEC frame or a shortened FEC frame. By carrying out the work presented here we tried to contribute towards this end. Throughout the simulations, we have considered two different size images as the source of information to transmit. Performance analysis have been presented by making comparisons between BER and PSNR values and psychovisually. Keywords: Low Density Parity Check Coding; BCH coding; OFDM; WiMAX; Digital Video Broadcasting; Rayleigh Fading Channel; Shortening; Zero-Padding; Digital Image Processing; Iterative decoding. ……………………………………………………………………………………………………………………………………………………………………………………………………………………