Sidelobe Suppression Using Extended Active Interference Cancellation with Self-Interferences Constraint for Cognitive OFDM Systems
Tóm tắt
Recently, increasing attention is paid to improving the spectrum utilization in cognitive OFDM systems. To enable coexistence between secondary users and primary users, a scheme, called as extended active interference cancellation (EAIC), was proposed for the effective sidelobe suppression of OFDM signals. However, with the EAIC method, the cancellation signals cause self-interferences to OFDM data subcarriers, which seriously degrades the symbol-error-rate performance, especially, when a high order modulation is used. In this paper, we analyze the self-interferences and formulate the minimization of both the total sidelobe power and the self-interferences as a optimization problem, which could be solved by least square method with acceptable complexity for OFDM communication systems nowadays. Simulation results show that the proposed EAIC-IC scheme provides a good sidelobe suppression performance of about 38.0 dB with signal-to-noise ratio loss less than 0.10 dB at symbol-error-rate of 10 − 3 when 64 QAM modulation is employed. Moreover, the proposed EAIC-IC scheme can provide an arbitrary tradeoff between the sidelobe suppression and the symbol-error-rate performance via adjusting the constraint parameter.
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