Turbo Coded OFDM with Large Number of Subcarriers

Spyridon K. Chronopoulos, Giorgos Tatsis, Panos Kostarakis

Physics Department, University of Ioannina, Ioannina, Greece.

DOI: 10.4236/jsip.2012.32021                

Abstract

Wireless communication systems have greatly advanced during the last years. A significant contributor in these systems’ performance has been Orthogonal Frequency Division Multiplexing (OFDM). Since its invention, it is considered to be a technological leap. This leap in splitting an information stream in multiple frequency carriers has been adapted by various scientists working on the development of wireless systems. Moreover, as OFDM presented excellent tolerance of channel fading and noise signals, the evolvement in terms of speed and reliability was consequent, because only a small stream of information is lost due to noise effects. OFDM along with the knowledge that Turbo codes is another excellent scheme of reducing BER, has triggered us to expand our research. So, we experimented in simulation level not only in joining OFDM with Turbo Codes but even in finding a better Turbo scheme compared to a typical PCCC, SCCC and a Convolutional encoder with Viterbi decoder. As the last goal has already been accomplished, in this paper is presented the new OFDM system consisted of our Turbo scheme. The analysis of the previous system took into consideration the effects of an AWGN channel. Also, this noise analysis was conducted using a simulation platform with specific attributes such as transmitting and receiving fixed number of subcarriers (2048 carriers after IFFT block) while using different types of convolutional concatenated codes, such as PCCC (Parallel), SCCC (Serial) and the new PCCC scheme. The results clearly show not only the improvement in the BER performance of the Turbo Coded OFDM systems (compared to others consisted of Viterbi decoders) but the overall superiority of the proposed design.

Keywords

Orthogonal Frequency Division Multiplexing; Cyclic Prefix; Zero Padding; Turbo Codes; Parallel Convolutional Concatenated Codes; Serial Convolutional Concatenated Codes; Iterative Decoding; Noise Variance

Conflicts of Interest

The authors declare no conflicts of interest.

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