%0 Journal Article
%T Parameter Estimation of Turbo Code Encoder
%A Mehdi Teimouri
%A Ahmadreza Hedayat
%J Advances in Electrical Engineering
%D 2014
%R 10.1155/2014/282108
%X The problem of reconstruction of a channel code consists of finding out its design parameters solely based on its output. This paper investigates the problem of reconstruction of parallel turbo codes. Reconstruction of a turbo code has been addressed in the literature assuming that some of the parameters of the turbo encoder, such as the number of input and output bits of the constituent encoders and puncturing pattern, are known. However in practical noncooperative situations, these parameters are unknown and should be estimated before applying reconstruction process. Considering such practical situations, this paper proposes a novel method to estimate the above-mentioned code parameters. The proposed algorithm increases the efficiency of the reconstruction process significantly by judiciously reducing the size of search space based on an analysis of the observed channel code output. Moreover, simulation results show that the proposed algorithm is highly robust against channel errors when it is fed with noisy observations. 1. Introduction Channel code reconstruction problem is usually considered in noncooperative communication scenarios, where finding the structure and parameters of the channel code is a major goal of the receiver [1¨C14]. Since turbo codes are introduced in many standards and applications [15¨C22], blind reconstruction of turbo codes in practical noncooperative situations is a well motivated problem. This problem has been investigated in [1¨C4, 8, 11], where some of the code parameters are assumed to be known to the receiver, such as the number of input and output bits of each constituent convolutional code and the structure of puncturing matrix. Having the above parameters, the receiver becomes capable of separating the received coded stream into three sets [3]: systematic bits, parity bits of the first convolutional encoder, and parity bits of the second convolutional encoder. Now the turbo code reconstruction problem converts into three simpler reconstruction problems: two convolutional code reconstruction problems and one interleaver reconstruction problem. However, in most practical noncooperative situations, the parameters of turbo code are unknown and thus should be estimated before applying reconstruction process or to test each possible set of parameters which is highly time consuming. To the best of the authorsĄŻ knowledge, no algorithm has yet been proposed for estimating these parameters, and this paper is the first to propose a novel method to estimate above-mentioned parameters before applying the turbo code reconstruction
%U http://www.hindawi.com/journals/aee/2014/282108/