Abstract—In this paper an approaches for increasing the effectiveness of error detection in computer network channels with Pulse-Amplitude Modulation (PAM) has been proposed. Proposed approaches are based on consideration of special feature of errors, which are appearances in line with PAM. The first approach consists of CRC modification specifically for line with PAM. The second approach is base of weighted checksums using. The way for checksum components coding has been developed. It has been shown that proposed checksum modification ensure superior digital data control transformation reliability for channels with PAM in compare to CRC. Keywords—Pulse-Amplitude Modulation, checksum, transmission, discrete. I. INTRODUCTION HIS development of information integration on the basis of computer technologies and telecommunication systems is one of the major factors of the progress in all spheres of human activities. The main issue on technologies improvement in information exchange is the maintenance of more reliable data transmission in the buses of computing systems and in the computer network channels. This issue is becoming more relevant in the current concern. It is determined by the number of factors, amongst of which the most important is the increase of transmission speed, and thus, the increase of negative impact of signal interference. The rise in the number of errors, caused by external electromagnetic fields, is influenced by the rapid growth of their intensity, determined by dynamic expansion of mobile communication means and wireless data transmission channels in the computer networks. On the contrary, there is an ongoing expansion process in the use of information technologies in all spheres of human activities, covering the ones connected with techno genetics risk, which toughens the requirements specified for the reliability of all components of computing systems and computer networks, including digital data transmission means. Taking into account the growth of transmitted in computing systems and networks information volumes, the increase of transmission processes reliability by means of guaranteed detection of the most widespread errors is the most significant. Thus, progressive advance in the way Author is with Department of Computer Science, Al Al-Bayt University, P.O.BOX 922283, 11192, Jordan (e-mail: hamarchi@yahoo.com). of data transmission needs adequate improvement in means, which provide superior reliability of data transmission in computing systems and networks. The channels with spectral and amplitude modulation of digital data are widely used in computer networks to increase capacity [1]. The main feature of such modulation is that bit groups of the controlled block are transmitted via channel signal. The spectral modulation of digital data, in particular, is used in phone-, cable and wireless lines of computer networks [1, 2]. The error detection in such lines has specific features, which are not fully taken into account by the currently existing error detection means. Therefore, the analysis of peculiarities of error occurrence in the lines with modulation, and also the development of methods, aimed to increase the effectiveness of control means through their adaptation to detected peculiarities, are important topical issues. II. ANALYSIS OF THE MODERN STATE OF THE PROBLEM ON MAINTENANCE OF DATA TRANSMISSION RELIABILITY IN THE CHANNELS WITH AMPLITUDE MODULATION Taking into account relatively low intensity of occurrence of data transmission errors in the buses of computing systems and computer network wire lines, the use of ARQ (Automatic Repeat Request), which implies recurrent transmission of the controlled data block on error detection, is regulated by the current protocols. Cyclic redundancy checks (CRCs) and checksums (CSs) are the most wide-spread means of error detection on digital data transmission through computer systems and networks. CRC with generating polynomial in the n-degree allows to detect all odd errors, all double errors, and also error clusters, the length of which does not exceed n [3]. CS ensures detection of odd errors solely, but unlike CRC, the control with the use of CS is carried out much easier and quicker. Pulse-Amplitude Modulation (PAM) is used quite often to increase capacity in the low-frequency lines for digital data transmission through computer networks. By this type of digital data modulation the group comprised of k adjacent bits, which is called Х={x 1 ,x 2 ,…,x k }, ∀j∈{1,…,k}:x j ∈{0,1} code group, is modulated with one channel signal, which can receive 2 k levels: from 0 to (2 k -1)⋅s, where s is discrete interval of the channel signal amplitude. When РАМ channel signal is distorted, k bits, which form a code group, can be basically distorted as well. However, according to [1] the errors, which occur in such lines, have the following specific features: Increase of Error Detection Effectiveness in the Data Transmission Channels with Pulse- Amplitude Modulation Akram A. Mustafa T World Academy of Science, Engineering and Technology International Journal of Computer and Information Engineering Vol:3, No:4, 2009 858 International Scholarly and Scientific Research & Innovation 3(4) 2009 scholar.waset.org/1307-6892/7888 International Science Index, Computer and Information Engineering Vol:3, No:4, 2009 waset.org/Publication/7888