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Copyright of Iraqi Journal for Electrical & Electronic Engineering is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper proposes a peak to average power ratio (PAPR) reduction companding scheme for single carrier frequency division multiple access. The proposed technique has multi-level compression (MLC) stages where a signal is adjusted according to its instant value with respect to these levels. To validate MLC function, PAPR, bit error rate (BER), average power (P_av), and power spectral density (PSD) are evaluated throw simulation. MLC improved PAPR significantly with low BER degradation. Using 16-QAM, MLC enhances PAPR by 4.38 dB while only 1.6 dB additional SNR is required to maintain 10^(-3) BER. MLC performance is compared with the recent companding techniques; Mu-law, Exponential, Trapezoidal, and tangent rooting. The BER simulation results show the superiority of MLC over these techniques. For PAPR reduction, different from other techniques, both Mu-law and MLC reduce PAPR significantly with close values. Finally, the Exponential and MLC preserve P_av with less side lobes in PSD. [ABSTRACT FROM AUTHOR]

In this paper, a system for the purpose of signals encryption using the technique of independent component analysis has been proposed. The proposed system mixes the original signal with arbitrary number of random signals in order to obtain a highly encrypted signal like noise. The number of random signals is indicated by an attached key signal preceding the encrypted signal. In order to increase the encryption strength, the number of random signals is changed at each signal transmission. An independent component analysis technique is utilized to separate signals and select the original signal by a designed selector. A set of parameters has been adopted to measure the encryption quality and decryption capability. Promising encryption results represented by up to - 48.35 dB for segmental spectral signal to noise ratio and 0.00037 correlation coefficient between the original and the encrypted signals are obtained. As well, an efficient signal decryption is achieved with 45.85 dB signal to noise ratio and nearly 1 correlation coefficient value between the original and reconstructed signals. In conclusion, the proposed system is a good candidate to be adopted in developing highly reliable security transceiver systems. [ABSTRACT FROM AUTHOR]