Blind Demodulation of Pass Band OFDMA Signals and Jamming Battle Damage Assessment Utilizing Link Adaptation
AIR FORCE INSTITUTE OF TECHNOLOGY WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
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This research focuses on blind demodulation of a pass band OFDMA signal so that jamming effectiveness can be assessed referred to in this research as BDA. The research extends, modi es and collates work within literature to perform a new method of blindly demodulating of a passband OFDMA signal, which exhibits properties of the 802.16 Wireless MAN OFDMA standard, and presents a novel method for performing BDA via observation of SC LA. Blind demodulation is achieved by estimating the carrier frequency, sampling rate, pulse shaping lter roll off factor, synchronization parameters and CFO. The blind demodulators performance in AWGN and a perfect channel is evaluated where it improves using a greater number OFDMA DL symbols and increased CP length. Performance in a channel with a single multi-path interferer is also evaluated where the blind demodulators performance is degraded. BDA is achieved via observing SC LA modulation behavior of the blindly demodulated signal between successive OFDMA DL sub frames in two scenarios. The rst is where modulation signaling can be used to observe change of SC modulation. The second assumes modulation signaling is not available and the SCs modulation must be classi ed. Classi cation of SC modulation is performed using sixth-order cumulants where performance increases with the number of OFDMA symbols. The SC modulation classi er is susceptible to the CFO caused by blind demodulation. In a perfect channel it is shown that SC modulation can be classi ed using a variety of OFDMA DL sub frame lengths in symbols. The SC modulation classi er experienced degraded performance in a multi-path channel and it is recommended that it is extended to perform channel equalization in future work.
- Electricity and Magnetism
- Non-Radio Communications