Performance analysis of OFDM based DAB systems Using Concatenated coding technique Arun Agarwal* Department of Electronics and Communication Engineering ITER, Siksha „O‟ Anusandhan University Bhubaneswar-751030, India arun.agarwal23@gmail.com S. K. Patra, Senior Member IEEE Department of Electronics and Communication Engineering National Institute of Technology Rourkela-769008, India skpatra@nitrkl.ac.in Abstract — Radio broadcasting technology in this era of compact disc is expected to deliver high quality audio programmes in mobile environment. The Eureka-147 Digital Audio Broadcasting (DAB) system with coded OFDM technology accomplish this demand by making receivers highly robust against effects of multipath fading environment. In this paper, we have analyzed the performance of DAB system conforming to the parameters established by the ETSI (EN 300 401) using time and frequency interleaving, concatenated Bose-Chaudhuri- Hocquenghem coding and convolutional coding method in different transmission channels. The results show that concatenated channel coding improves the system performance compared to convolutional coding. Keywords-DAB, OFDM, Multipath effect, concatenated coding. I. INTRODUCTION Digital Audio Broadcasting (DAB) was developed within the European Eureka-147 standard [1] to provide CD quality audio programmes along with ancillary data transmission (e.g. travel and traffic information, still and moving pictures, etc.) to fixed, portable and mobile receivers using simple whip antennas [2]. In 1995, ETSI (European Telecommunications Standards Institute) adopted DAB as the only European standard for digital radio. The reception quality of analog AM/FM systems on portable radio is badly affected by Multipath fading (reflections from aircraft, vehicles, buildings, etc.) and shadowing [3]. These systems also suffer from interference from equipment, vehicles and other radio stations. DAB uses coded orthogonal frequency division multiplexing (COFDM) technology to combat the effects of Multipath fading and inter symbol interference (ISI). Additionally the VHF frequency band available for the sound broadcasting throughout the world has either saturated or fast approaching saturation. There is a need for more spectrally efficient broadcasting technology apart from conventional analog systems. Since DAB uses OFDM technology therefore the system can operate in single frequency networks (SFNs) providing the efficient usage of available radio frequency spectrum. Earlier work focused more on the effect of protection levels in diverse transmission channels, design and implementation of DAB channel decoder (physical layer) on FPGA hardware [5, 13, 14]. *The work reported was conducted at NIT, Rourkela. In this paper we propose a BCH coding based concatenated channel coding technique for improved performance of DAB system in different transmission channels. In this paper we developed a DAB base-band transmission system based on Eureka-147 standard [1]. The design consists of energy dispersal scrambler, QPSK symbol mapping, convolutional encoder (FEC), D-QPSK modulator with frequency interleaving and OFDM signal generator (IFFT) in the transmitter side and in the receiver corresponding inverse operations is carried out along with fine time synchronization [4] using phase reference symbol. DAB transmission mode-II is implemented. A frame based processing is used in this work. Bit error rate (BER) has been considered as the performance index in all analysis. The analysis has been carried out with simulation studies under MATLAB environment. Following this introduction the remaining part of the paper is organized as follows. Section II introduces the DAB system standard. Section III, provides brief overview of the DAB system. In Section IV, the details of the modeling and simulation of the system using MATLAB is presented. Then, simulation results have been discussed in Section V. Finally, Section VI provides the conclusions. II. INTRODUCTION TO DAB SYSTEM The working principle of the DAB system is illustrated in conceptual block diagram shown in Fig. 1. At the input of the system the analog signals such as audio and data services are MPEG layer-II encoded and then scrambled. In order to ensure proper energy dispersal in the transmitted signal, individual inputs of the energy dispersal scramblers is scrambled by modulo-2 addition with a pseudo-random binary sequence (PRBS), prior to convolutional coding [1]. The scrambled bit stream is then subjected to forward error correction (FEC) employing punctured convolutional codes with code rates in the range 0.25-0.88. The coded bit-stream is then time interleaved and multiplexed with other programs to form Main Service Channel (MSC) in the main service multiplexer. The output of the multiplexer is then combined with service information in the Fast Information Channel (FIC) to form the DAB frame. Then after QPSK mapping with frequency interleaving of each subcarriers in the frame, π/4 shifted differential QPSK modulation is performed. Then the output of FIC and MSC symbol generator along with the