Authors V.P. Fedosov, D.G. Kovtun, A.A. Legin, A.V. Lomakina
Month, Year 11, 2015 @en
Index UDC 004.93’12, 004.93’14
Abstract The article presents the process of forming and analysis of OFDM-signal model with low- band radiation, ensure the selection of the parameters of a raised cosine window and the number of subcarriers in the formation of the guard interval. To explain the essence of forming model OFDM-signal (Orthogonal frequency-division multiplexing), justification of the method and iden- tify the effects of lowering of-band radiation is a description of the formation of the model and source of the radiation-band signal based on multipath its distribution channel radio. Research of the influence of the level-of-band radiation as a function of the length of the recession of the win- dow of the "raised cosine" in relation to the duration of the guard interval of the OFDM symbol is made on an example of OFDM-symbol having 1024 subcarriers. Among these 400 subcarriers are protective, and the remaining 624 subcarriers information. Because of the guard interval and window treatment, broadband multipath fading appears in an OFDM as the number of narrow-band subcarriers freezes without ICI and ISI. Single remainder effect of multipath is the random phase and amplitude at the subcarrier. Investigation of the effect on the duration of the guard interval band emission level duration of the window function is chosen to be the length of the cy- clic prefix, since it provides the lowest-band radiation. The duration of the prefix chosen equal 1/128, 1/16, 1/4, respectively. Analysis of the results showed that the longer the guard interval, the lower the out of band radiation. As a result of studies have shown that the level-of-band emission is reduced by 15 dB with respect to the boundaries of the detuning frequency band allocated for the communication channel at 0,75 MHz.

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Keywords Orthogonal frequency consolidation; OFDM; interference; out-of-band radiation; carrier; subcarriers; pilot-signals.
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