Title :
Masked M-QAM OFDM: A simple approach for enhancing the security of OFDM systems
Author :
Chorti, Arsenia ; Kanaras, Ioannis
Author_Institution :
CCM Dep., Middlesex Univ., London, UK
Abstract :
This paper investigates the secure transmission of Orthogonal Frequency Division Multiplexing (OFDM) signals, masked under non-orthogonal FDM signals of approximately the same overall bandwidth. Carrier orthogonality of traditional OFDM is intentionally violated in order to generate an encrypted signal at the physical layer, without any loss in bandwidth efficiency or extra overhead. A symmetric secret key is used for the modulation of part of the FDM signal while the original information symbol modulates the remaining carriers. The encrypted FDM signal generation takes place in an IFFT stage by simple truncation of part of its output. At the receiver, a straightforward suppression of the induced Inter-Carrier Interference (ICI) is performed before the OFDM demodulator, based on knowledge of the secret key. The key holder subsequently uses the traditional OFDM FFT demodulator to extract the information symbol. We demonstrate that an eavesdropper cannot demodulate the transmitted FDM signal by reduced complexity detection methods due to its severe ill-conditioning. Conversely, they have to rely on vectorial Maximum Likelihood detection of exponential complexity. Furthermore, in real noisy environments the eavesdropper detection capability is further affected by the abrupt shrinking of the FDM demodulator detection regions.
Keywords :
OFDM modulation; demodulators; fast Fourier transforms; intercarrier interference; maximum likelihood detection; quadrature amplitude modulation; radio receivers; telecommunication security; FDM signal modulation; IFFT stage; OFDM FFT demodulator; OFDM signal; OFDM system; carrier orthogonality; eavesdropper detection; encrypted FDM signal generation; exponential complexity; information symbol; inter-carrier interference suppression; masked M-QAM OFDM; maximum likelihood detection; nonorthogonal FDM signal; orthogonal frequency division multiplexing; real noisy environment; receiver; secure transmission; symmetric secret key; system security; Bandwidth; Cryptography; Data mining; Demodulation; Frequency division multiplexing; Interference suppression; OFDM modulation; Physical layer; Security; Signal generators;
Conference_Titel :
Personal, Indoor and Mobile Radio Communications, 2009 IEEE 20th International Symposium on
Conference_Location :
Tokyo
Print_ISBN :
978-1-4244-5122-7
Electronic_ISBN :
978-1-4244-5123-4
DOI :
10.1109/PIMRC.2009.5450168