| By using electronic or other technologies electronic countermeasure reconnoiters, interferes and then destroys communication devices of the enemy, while protecting communications between ours. Electronic jamming takes an essential part in electronic countermeasure, in which electromagnetic waves and acoustic waves are generated in the aim of transmitting artificial echoes to disturb or deceive communication devices of the opponent.OFDM communication system shares the characteristics of frequency division multiplexing in analog modulation technology and the advantages of multicarrier modulation. Frequency spectrum of the transmitted signal is overlapped for high efficiency of frequency spectrum and transmission speed. OFDM communication system has occupied a leading position in WLAN, digital television and other fields after development in the last half century. Proposed in 1999, IEEE 802.11a standard shares the majority part in WLAN market, and becomes an indispensable communication module for portable PCs, smart phones and other devices.The majority of researches cannot meet the demand of communication jamming for their emphasis on radar countermeasure. It shows great importance in efficient jamming against communication systems, particularly OFDM system. Efficient low Power jamming against OFDM systems can be achieved after analyzing on the characters of OFDM system and choosing of sensitive jamming spots.As for the choice of jamming, we looked into the form of broad-band noise jamming, partial-band noise jamming, impulsive noise jamming, multitoned jamming and swept multitoned jamming. With regard to the sensibility of accurate timing, we tried delayed transmission jamming and inversed phase jamming.Conclusions can be drawn from the results that that partial-band noise jamming and multitoned jamming that focus on the subcarrier frequencies are more efficient. As for the deception jamming, delayed transmission jamming may perform more effectively. |
PDF Full Text Request