IntroductionIt all started back around the 1990 when the amount of chaostype communication systems started expanding and began to exploit theproperties of chaotic waveforms. The amount of potential non-linear signals hadwas virtually unimaginable. Due to so much upside many communicationapplications have been specifically designed when energy, data transfer rate,and synchronization are important parameters. A major focus took place withnon-coherent chaos-based systems being able to implement the advantages ofchaotic signals and noncoherent detection and to avoid needing chaoticsynchronization, which in the presence of additive noise exhibits a weakperformance. This paper will describe the application of Chaos engineering forwireless communication systems explaining their pros, and cons to society andexplain exactly how chaos engineering can be implemented to ensure a moreprotected and secure communication channel where data is still efficientlytransmitted.
In order to really understand what chaos engineering is you mustfirst understand the meaning of the eachterm. Synchronization in schemes are based on coherent detection, it also enablesand allows timing as well as recovery. Carrier recovery refers to thereproduction or recovery, at the receiver’s end of the carrier signal producedin the transmitter. Once both transmitter and receiver oscillators are matched,coherent demodulation of the modulated baseband signal is possible. On itsturn, timing recovery refers to the need that both coherent and noncoherentreceivers have to know the exact time and duration of each received symbol in astream, in order to be able to assign decision times and reset the initialconditions of the correlator6. Simply speaking chaos synchronization means wea specific form of carrier recovery will be utilized and implemented in orderto fully recover the carrier’s signal.Previous WorkIn the last twenty-five years cell phones and morespecifically wireless communication have seen a rise in usage and demand.
Withthis increase in demand Multi carrier (MC) transmission has become basically anecessity. MC transmission happens when the signal being sent is divided intodifferent “sub” signals which are sent in a parallel manner over the channel tobe transmitted and then received by the receiver. This allows for informationto transfer at a faster rate than if it were to have the same sample rateserially.
Chaos Shift Keying (CSK) is a digital modulation where each symbol tobe transmitted is encoded as coefficients of a linear combination of signalsgenerated by different chaotic attractors 3. Transmission and reception ofthe signal relies basically upon the transmitter and receiver of the systembeing synchronized. However, this is not always the case as in a non-coherentsystem. Which leads to the introduction of the two types of system detection,coherent and non-coherent. Synchronization of the coherent system allowsrecovery of both the carrier and timer.
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Basically the systems carrier recoveryis the capability for the receiver to duplicate the signal that has been sentfrom the transmitter. This specific signal decoding method is called chaos-passfiltering which use the property of synchronous systems to discard thenon-chaotic part of the signal, which allows the message to be separated fromthe chaotic carrier signal 3. Anon-coherent receiver doesn’t need the carrier signal’s phase information whichis beneficial in the fact that it doesn’t require complex/expensive carrierrecovery circuit 2. A proposed systemwith a non-coherent receiver, named differential chaos shift keying (DCSK)system, in which chaotic synchronization is not used or needed on the receiverside, delivers a good performance in multipath channels. Furthermore,differential non-coherent systems are better suited than coherent ones for timeand frequency selective channels 1. DCSK is a variant of CSK with two mapswhose basis sequences consist of repeated segments of chaotic waveforms. Totransmit a “1” two equivalent sections of length N/2 are sent.
To transmit a”0″ the second segment is multiplied by (?1). The decision on the transmittedbit is based on the correlation between these two segments and the decisionthreshold is zero, independently of the channel noise 2. One major problemwith using DCSK and a non-coherent CSK is the need to use aperiodic signals,which means that the energy per signal is distinct at each symbol andnon-uniform. Essentially because we’re using an aperiodic and have differentenergy values the receiver can have errors that will occur even when thechannel is ideal and noiseless which is obviously troublesome. The major weaknessof the DCSK system is an infiltrator is able to realize the chaotic sequence.
Anumber of recent studies have proved that an intruder can recover chaoticsequences by blind estimation methods and use the sequences to detect symbolperiod, which will result in the original data being exposed. To overcome thissecurity weakness, this paper proposes a novel chaotic DSSS technique, wherethe symbol period is varied according to the nature of the chaotic spreadingsequence in the communication procedure. The data with variable symbol periodis multiplied with the chaotic sequence to perform the spread-spectrum process.Discrete-time models for the spreading scheme with variable symbol period andthe despreading scheme with sequence synchronization are presented andanalyzed. Multiple-access performance of the proposed technique in the presenceof the additional white Gaussian noise (AWGN) is calculated by means of boththeoretical derivation and numerical computation 5. With this knowledge an intruder is no longerable to identify the symbol period, even with adequate data of the chaoticsequence applied.
