Paper Sample on Noise Based Modulation Techniques

In the past few years, there have been some noise based modulation techniques which have been developed. Of the various techniques and methods that are currently present, the Code Shifted Differential Chaos Shift Keying modulation technique offers a more efficient and more efficient performance of bits with errors (BER), the technique also offers a more precise efficiency and this is because of its Internet top-level domain modus operandi (code field approach). The QCSK modulation method has several advantages, some of which include, its rate of data is greater, and its BER results are same as those produced by the DCSK even with a similar range of frequencies used for transmitting a signal. Through the combination of merits of both the code shifted differential noise shift keying system together with Quadrature noise shift keying system, a better and more developed scheme known as CS- QCSK modulation is produced. In this paper, a new noncoherent Differential Noise Shift Keying is proposed and named Extended Differential Noise Shift Keying (CS-DCSK). Each pair of bits is modulated using two different versions of the same chaotic reference signal; the

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a first information bit is modulated with the chaotic reference signal block while the next information bit is modulated after reversing samples' order of the same reference block.

Some of the advantages of this proposed system are that it has lower noise levels and its rate of transmission of data is relatively high, and the rate is stronger compared to the currently available systems. Scientific and methodical expressions used to show the BER are derived from two channels; these two are Additive White Gaussian noise channel (which is a basic noise model. It is mostly applied in information theory for the purposes of mimicking the outcomes of a number of random processes which take place in the surrounding), the other is Rayleigh multipath fading channel. Bit-error performance in additive-white-Gaussian-noise of the proposed system is analyzed and compared with the other chaos based communication systems. Results show that the bit-error rate performance of the E-DCSK is often better than other schemes when spreading factors relatively small. At the end of this research paper, some simulation results are presented, and they indicate that the proposed method performs in a better way compared to the current chaotic modulation technique especially in regards to bit error rate.

KEYWORDS

Differential chaos shift keying (DCSK); Bit Error Rate (BER); Code shifted differential chaos shifting keying (CS-DCSK); Quadrature chaos shift keying (QCSK); Quadrature chaos shift keying (QCSK); Multiple access; Chaos based communication.

INTRODUCTION

Chaotic signals are characterized by their sensitive dependence on initial conditions and their random-like behavior. Also that, they have also had a continuous broadband power spectrum characteristic this makes them crucial in the encoding of information and messages in communications. The primary chaos shift keying (CSK) maps various symbols to different chaotic attractors, and these are generated through a dynamical system for various values of a bifurcation parameter or by entirely different dynamical systems. A consistent correlation CSK receiver is then required at the receiving end to decode the signals. Noncoherent detection is also possible provided the signals generated by the different attractors have different attributes, such as the mean of the absolute value, variance, and standard deviation. However, the optimal decision level of the threshold detector is dependent upon the signal-to-noise ratio. To be able to overcome the threshold level shift problem, differential CSK (DCSK) is proposed. The advantage of DCSK over CSK is that the threshold level is always set at zero and is independent of the noise effect. Since CSK/DCSK spreads the spectrum of the data signal over a much larger bandwidth, multiple access becomes a critical element for the practical implementation of the system. Furthermore, it is imperative that more users are included in the same bandwidth without causing excessive interference to one another. A two-user DCSK system was first proposed. In this paper, a generalized multiple access technique for use with DCSK (MADCSK) is proposed and analyzed.

The proposed scheme is simple and is in theory scalable to any number of users, provided the low-correlation property is maintained among the chaotic signal segments representing the different users. Instead of using the currently present modulation techniques, a system with a transmission medium which has a greater bandwidth in comparison to one voice channel is used. A chaotic signal which is not periodic in nature acts as a conveyance tool. The use of this bandwidth results in excellent correlation features and strength while reducing or eliminating the signals not arriving at their antenna through their respective paths. The primary foundation of noise based modulation systems for both comprehensible and incomprehensible schemes are provided as well. The working concept for the coherent system is that the recovery requires a similar duplicate of the chaotic signal. However, its impossible to cause (a set of data or files) to remain identical in more than one location in an empirical environment. A general review of the evolution and growth of the chaos techniques and methods which are based on modulation means, with their importance, is provided. To increase the efficiency of a differential chaos shift keying, a frequency modulated DCSK is integrated to solve any bit rate errors and energy issues which are present in the DCSK. There is also a study, analysis, and evaluation of the performances and productivity of the frequency modulated DCSK multipath (the propagation phenomenon that results in radio signals arriving at the receiving antenna through various paths). Evaluation and analysis are simulation based. The channels which are affected by arbitrary fading are incorporated into the model of the channel.

Synchronization is highly used in digital communications, and its role is analyzed as well. In the receiver, there are double pieces of chaotic signals which are connected; the binary notations are decrypted and interpreted using the symbol present in the output of the correlates. The differential chaos shifting key communication channels take advantage of the continuous and repetitive inherent quality of the chaotic signals, the channels start from light binary communications and evolve into complex demodulators (devices or instruments designed to detect the presence of a particular object or substance and to emit a signal in response). The evaluation of the productivity of the two-part DCSK multipath is through the use of general association link detector. The Quadrature (a phase difference of 900 between two waves of the same frequency, as in the color difference signals of a television screen) CSK can be described as a prototype of DCSK containing many levels. The CSK working operation is through the production chaotic functions which are at right angles and statistically independent. The system permits the snowballing of the rate of data which uses a similar range of frequencies as those of the DCSK.

There is a discussion on the productivity of the differential chaos shifting keying system through a channel that has Rayleigh fading or Ricean fading. It is also imperative to look into the many access methods having distinct chaos shift keying through the use of an iterated function which is one dimension of nature. The function can produce chaotic signals for each and every user. The frequency modulated quadrature chaos shift keying can provide an inbuilt wideband signal; these signals have a steady rate of energy. The overall velocity of the chaos shift key is increased through clustering together of FM-QACSK which contain high energy. It is important to note that Code shifted differential chaos shifting keying applies the code domain method to improve the bit error productivity and the efficiency of the signals bandwidth. All the signals that contain data and information are transmitted concurrently. The proposed SC-QCSK is an improved and modified version of a combination of Quadrature chaos shift keying, and Code shifted differential chaos shifting keying. It has fewer shortcomings, minimizing on the various weaknesses of its components and maximizing on the strengths of the two systems while providing very high rates of data.

OVERVIEW ON CHAOS BASED MODULATION SCHEMES

So as to get a better understanding of the Code shifted differential chaos shifting keying system, it is important to explain the following system methods: Differential chaos shift keying, Quadrature chaos shift keying, and Code shifted differential chaos shifting keying.

Differential Chaos Shift Keying (DCSK)

In this method, one segment of information is symbolized by a binary function chaotic sample. There is the transmission of a signal which contains two elements. The first element is referred to as reference signals (these are mostly two dimensional). The second element is referred to as information bearing signals. These contain the information that is being transmitted. Supposing there is a transmission of bit X, the information bearing signal will be the transposed replica value which makes it enable for a program to access datum whether indirectly or directly. The datum can be recorded which are contained in the storage devices of any devices. Consequently, the formula for the calculation of the n-th symbol will be as shown below:

Ti < t< (ti + T2 ) . (1)

T stands for the symbol duration. Extraction of the original data or information takes place in the receiver. The extraction process follows a particular process; the evaluation and calculation of the relationship between the sample functions which have been transmitted. After this, the supplied correlators data is sampled through a variety of symbol periods. After the sampling process is over, the output is sent to the device which calculates the base numeral system; the numeric values can only fall between two distinct symbols, either zero (0) or one (1).

Quadrature Chaos Shift Keying

Just like in differential chaos shift keying, every symbol period that is present in the Quadrature Chaos Shift Keying contains two units. The main difference is that the signals which contain information hold double segments of data through the use of the Quadrature Chaos Shift Keying method. This method produces a swifter and faster rate of data, and this is because of its ability to transmit double bits and segments of information at the same time. Generation of chaotic signals in this method is in a manner which is both orthogonal and normalized functions of x and y. However, in a sample function, t is taken to be x, and this represents the chaotic reference signal. Upon making the assumption that that particular signal contains an average numerical value of zero, then;

X (t) Fk sin (kt + k) (2)

k = 1

X(t) is used to represent the chaotic reference signal waves which have a phase difference of 900 between them, but they contain the same frequency. This numerical value is calculated through the modification of every phase of every Fourier rate of vibration, by a margin or extent of p/2. Consequently, the final equation will be as follows:

y (t) Fk sin (kt + k -/2 )(3)

k = 1

The two signals are right angles at interludes, and the equation will be,

E b (a1 Cx (t T/2) + a 2 cy (t T/2) (4)

Eb is used to represent the bit energy which is used over a time and distance period of T/2, those should be at right angles.

Cx(t-T/2) is used to represent the chaotic signal which has time dur...