Superimposed Chaos Sequence On IQ Baseband Signals for OFDM-Based Cognitive Radio Channel Estimation

In this paper, the superposition of deterministic chaotic sequences on the I and Q parts of the QPSK symbols are used to extract information about the changes on the channel. The proposed method is used under an OFDM-Based Cognitive Radio (CR) constraints, to perform channel estimation and equalization. As the proposed scheme does not involve the use of pilot tones, it provides a gain on the spectrum, meaning more subcarriers are used for data transmission at the cost of minimum power consumption, particularly in the low SNR system performance. It is relevant to highlight that the spectrum available for secondary users is fragmented and any bandwidth increase is valuable. Also, the simulation results show that when there is no power balancing between the data and the deterministic sequences the gain decreases as the signal power increases, showing the need for power management assigned to the training sequence.