A Closed-Form Expression of Instantaneous Bit Error Rate for BIC-OFDM Systems

The instantaneous bit error rate (I-BER) is a direct representation of system performance given a particular channel realization. The I-BER knowledge enables wireless system to combat fading channel impairments by properly adapting transmission parameters. In this paper, we derive the I-BER for a bit-interleaved coded orthogonal frequency division multiplexing (BIC-OFDM) system. In high signal-to-noise ratio (SNR) regions, under the assumption that an erroneous symbol contains only one bit error, a codeword pairwise error probability (PEP) is approximated by a symbol PEP. The above assumption is used again to evaluate the symbol PEP for an arbitrary QAM with Gray labeling. Compared with a previously obtained result, the new I-BER expression provides a tighter upper bound for convolutional coded BIC-OFDM systems. We also discuss a practical use of the I-BER in a link adaptation process.