Extended Code Index Modulation Scheme Based on Reversible Elementary Cellular Automata Encryption
In order to address the problems of limited pseudo noise(PN)code resources in direct sequence spread spectrum system and degraded bit error rate(BER)performance of code index mo-dulation system,this paper proposes an extended code index modulation(E-CIM)scheme based on reversible elementary cellular automata encryption.First,to address the problem of limited PN code resources,a method of iterating PN codes using chaotic rules of elementary cellular automata is proposed to achieve the purpose of extending PN codes.In addition,to address the problem of BER degradation of code index modulation,this paper pro-poses a code index modulation scheme with reversible elementary cellular automata encryption,in which the information bits are cut into modulation bits and mapping bits at the transmitter side,and mapped into modulation symbols and spreading code inde-xes,respectively.The in-phase component is spread using the spreading code of the corresponding index,while the mapped bits are encrypted using the reversible elementary cellular automata,The orthogonal component is spread by the spreading code corresponding to the index selected by the encrypted mapped bits.Simulation and analysis results show that under the same spec-trum efficiency conditions,the BER performance of E-CIM is superior to that of the CIM and GCIM schemes by about 2～4 dB and superior to that of the N-CSK-CIM scheme by about 0.5dB in an additive Gaussian white noise channel when the BER is 10-5.
Direct sequence spread spectrumCode index modulationElementary cellular automataBit error rate
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