Digital Communications with Emphasis on Data Modems

ABOUT THE COVER

The three‐dimensional plot on the cover depicts the bit‐error performance as a function of the number of rows and columns of a deterministic block interleaver and deinterleaver operating in a Rayleigh fading channel. The plot corresponds to a signal‐to‐noise ratio of E_b/N_o = 6.5 dB and is generated using a Monte Carlo simulation with 10 M bits at each row–column combination. The source data bits are coded using a rate 1/2, constraint length 7, convolutional encoder and are decoded using the Viterbi algorithm with a trellis depth or memory of 31 coded bits. The coded bits are sequentially entered into the interleaver row by row and removed column by column and applied to a binary phase shift keying (BPSK) symbol modulator. The channel is modeled as a correlated Gaussian random process with the correlation coefficient selected to result in a decorrelation time corresponding to six coded bits. In the region of the plot corresponding to the lowest bit‐error performance, the loss in E_b/N_o at P_be = 10⁻⁵ compared to the additive white Gaussian noise channel is 2.7 dB. Based on these conditions and results, a reasonably sized (row,column) block interleaver is (11,51).