TY - JOUR TI - Improvement of gallager upper bound and its variations for discrete channels AU - Xenoulis, K. AU - Kalouptsidis, N. JO - IEEE Transactions on Information Theory PY - 2009 VL - 55 TODO - 9 SP - 4204-4210 PB - SN - 0018-9448, 1557-9654 TODO - 10.1109/TIT.2009.2025576 TODO - Coset weight and distance distributions; Gallager bound; Inverse exponential sum inequality; Maximum-likelihood (ML) decoding; Word and bit error probabilities, Bit error rate; Decoding; Distribution functions; Maximum likelihood, Probability TODO - A new tight upper bound on the maximum-likelihood (ML) word and bit-error decoding probabilities for specific codes over discrete channels is presented. It constitutes an enhanced version of the Gallager upper bound and its variations resulting from the Duman-Salehi second bounding technique. An efficient technique is developed that, in the case of symmetric channels, overcomes the difficulties associated with the direct computation of the proposed bound. Surprisingly, apart from the distance and input-output weight enumerating functions (IOWEFs), the bound depends also on the coset weight distribution of the code. © 2009 IEEE. ER -