LDPC-coded OFDM-system with BPSK modulation: Performance comparison with uncoded OFDM system

This paper proposes an automated algorithm to correct loss of sub-carriers in Orthogonal Frequency Division Multiplexing (OFDM) system using Low-Density Parity-Check (LDPC) codes. OFDM transmits data on high bit-rate but high-peak-to-average ratio PAPR, subcarriers-loss due to deep fades in multipath causes 2-dimensional errors i.e., in time and frequency-domain, and inter-symbol-interference (ISI) etc. occurs in multipath OFDM system. In order to reduce such OFDM errors, error correcting codes have been used by researchers like Turbo-code, LDPC-code, ReedSolomon-code, Alamouti-code etc. LDPC-coded OFDM system is employed in the paper to correct 2D error and make improvement in OFDM BER curve. LDPC was first introduced by Gallager during his graduation in 1962. The main purpose for LDPC selection amongst all error correcting codes is its performance which is near Shannon limit. Information bits are encoded using LDPC and modulated using binary phase-shift-keying (BPSK). Then, OFDM system transmit subcarriers on channel and is demodulated using BPSK and decoded using LDPC at receiver to recover original information bits. Results show that LDPC-coded-OFDM performed better than un-coded-OFDM in terms of BER vs Eb/No (energy-per-bit to spectral-noise ratio) in decibels.