Enhancing of Chaotic ON-OFF Keying scheme

In this paper, two techniques are proposed to enhance the security and performance of Chaotic ON-OFF Keying (COOK) scheme and named as a Permutation based Chaotic ON-OFF Keying (P-COOK) and Time Reversal based COOK (TR-COOK) respectively. In the first system, bits are transmitted in frames. Samples of the modulated bits are interleaved and permutated before transmission which hides bit pattern in the transmitted signals particularly at high level of E_b/N_o. Security is maintained by considering the permutation matrix as a shared Key between transmitter and receiver. In order to recover the transmitted bits, each received frames will undergo inverse permutation transformation followed by energy detector. In the second scheme, the detection threshold is optimized by adding the chaotic signal with its mirrored version within one bit duration. Theoretical expression for the correlator output for (P-COOK) and (TR-COOK) are developed and compared with conventional COOK. Bit-Error-Rate (BER) performance for both systems are calculated and compared with conventional COOK under Additive White Gaussian Noise (AWGN) environment and with different values of spreading factor. Simulation results show that the proposed system can secure bit patterns successfully without degradation of the Bit-Error-Rate (BER) performance or use of additional bits compared with the conventional COOK while the second systems outperform BER of COOK at higher value of the spreading factors.