Title :
On the frame-error rate of concatenated turbo codes
Author :
Takeshita, O.Y. ; Collins, O.M. ; Massey, P.C. ; Costello, D.J., Jr.
Author_Institution :
Dept. of Electr. Eng., Ohio State Univ., Columbus, OH, USA
fDate :
4/1/2001 12:00:00 AM
Abstract :
Turbo codes with long frame lengths are usually constructed using a randomly chosen interleaver. Statistically, this guarantees excellent bit-error rate (BER) performance but also generates a certain number of low weight codewords, resulting in the appearance of an error floor in the BER curve. Several methods, including using an outer code, have been proposed to improve the error floor region of the BER curve. We study the effect of an outer BCH code on the frame-error rate (FER) of turbo codes. We show that additional coding gain is possible not only in the error floor region but also in the waterfall region. Also, the outer code improves the iterative APP decoder by providing a stopping criterion and alleviating convergence problems. With this method, we obtain codes whose performance is within 0.6 dB of the sphere packing bound at an FER of 10/sup -6/.
Keywords :
BCH codes; concatenated codes; convolutional codes; error statistics; iterative decoding; turbo codes; BER performance; bit-error rate; coding gain; concatenated turbo codes; convergence problems; convolutional codes; error floor region; frame-error rate; iterative APP decoder; long frame length; low weight codewords; outer BCH code; outer code; sphere packing bound; stopping criterion; waterfall region; Bit error rate; Communications Society; Concatenated codes; Convergence; Convolutional codes; Error correction codes; Iterative decoding; Modulation coding; Signal to noise ratio; Turbo codes;
Journal_Title :
Communications, IEEE Transactions on
