Code Division Multiple Access

In this paper, a time-hopping multicarrier code-division multiple-access (TH/MC-CDMA) scheme is proposed, where data is transmitted using relatively high-duration time-domain pulses with the aid of M -ary PPM (MPPM). At the receiver, information is extracted from one of the M possible time-slot positions. In TH/MC-CDMA, each symbol is transmitted using a number of time-domain pulses with each time-domain pulse modulating a subcarrier. Since each subcarrier only occupies a fraction of the system bandwidth, the time-domain pulses, hence, have a relatively high duration. Consequently, even the total system bandwidth is extremely high, the subcarrier signals may be designed so that they are not too dispersive and only a low number of independent multipath components appear at the receiver. In TH/MC-CDMA system, diversity gain may be achieved by combining the independently faded multipath com- ponents or/and by transmitting the same information symbol using several subcarriers, which are combined at the receiver. In TH/MC-CDMA, the transmitter does not conflict the problem of nonlinear fluctuation resulted from the high peak-to-average factor [6], since, in the TH/MC-CDMA transmitter, the TH pat- terns may be designed so that only one of the subcarrier signals is activated at any time instant. However, fast-Fourier trans- form (FFT)-assisted-MC demodulation technique can still be invoked for demodulating multiuser TH/MC-CDMA signals. In fact, in TH/MC-CDMA, single-user or multiuser detection can be carried out after a single FFT-MC demodulation device. In addition to the aforementioned advantages, the proposed TH/MC-CDMA may provide some other advantages, which are summarized in Section V associated with our conclusions.

Wireless communication is dramatically changing our lives. The ability to communicate anytime and anywhere increases our quality of lives and improves our business productivity. In cellular wireless systems, the network consists of numerous mobile users communicating with one or multiple base stations (BS) that are interconnected with a mobile telephony switching office. Originated from the spread-spectrum techniques, the code- division multiple access (CDMA) systems can support simultaneous digital communication among a large community of relatively uncoordinated users. CDMA exhibits potential capacity increase over the conventional time-division multiple access (TDMA) and frequency-division multiple access (FDMA), because CDMA capacity is only interference limited, while TDMA and FDMA are primarily bandwidth limited [GJP91]. The inherent frequency diversity of wideband signals enables CDMA to efficiently suppress the narrow- band interference in radio link. Direct sequence (DS) CDMA has been widely applied in the second and third generations cellular standards (IS-95, WCDMA and CDMA2000). It is also a very promising option for the next generation wireless communications.

In the context of direct-sequence (DS) code-division multiple-access (DS-CDMA) communications, there are two types of spread-spectrum schemes. The first of these spread-spectrum schemes [1]–[3] spreads the originaldata stream using a signature code in the time (T)-domain, and the spread-spectrum signalis transmitted using a single-carrier. In contrast, the second DS spread-spectrum scheme [4]–[7] spreads the originaldata stream to a number of subcarriers using a signature code in the frequency (F)-domain, and each chip of the resultant spread- spectrum signalis transmitted by a different carrier. Hence, this scheme is also referred to as multicarrier CDMA (MC-CDMA) in the literature [5], [6], [8], [9]. Furthermore, there is a family of multicarrier CDMA in which each subcarrier signalconstitutes a T-domain DS spread signal, but no F-domain spreading is employed. This family of multicarrier CDMA is usually referred to as MC DS-CDMA [5], [10]–[16]. An amalgam of these spread-spectrum schemes was proposed in [17]. This extended spread-spectrum scheme spreads the transmitted data stream using two signature codes, where one of the signature codes corresponds to the T-domain spreading, while the other corresponds to the F-domain spreading. Since the proposed multicarrier DS-CDMA scheme employs both the previously mentioned T-domain spreading and F-domain spreading, it is referred to as TF-domain spread MC DS-CDMA.

There are a number of well-known optical multiple-access schemes, which employ time, wavelength (infrared) and time-and-wavelength domains for message separation. These are Wavelength-Division Multiple-Access (WDMA), Time-Division Multiple-Access (TDMA), and Code-Division Multiple-Access (CDMA). In WDMA and TDMA a fixed amount of wavelength and time, respectively, is allocated to accommodate the individual channels. Theoretically, an infinite number of possible channels can exist, although most of these are impractical due to the implementation difficulties [LiuOO]. CDMA does not explicitly allocate a fixed amount of time to each channel but uses codes to spread the signals so that multiple channels can be transmitted concurrently. This is achieved at the expense of greater duration or bandwidth. Both WDMA and TDMA capacity is hard limited due to the number of channels determined by the total number of wavelength and time resources, where no more users can access the network once capacity is reached. Alternatively, the capacity of CDMA is soft limited as it allows flexible network capacity but at the cost of quality, the system BER depends

Abstract—In this contribution the performance of multiple- input multiple-output space-division, code-division multiple- access (MIMO SCDMA) is investigated, when the low-complexity reduced-rank detection is employed. In [1] a MIMO SCDMA sys- tem is proposed, aiming at improving the capacity of the existing direct-sequence (DS) CDMA (DS-CDMA) systems. The perfor- mance of the SCDMA system in [1] is investigated, when the full- rank multiuser detectors (MUDs) are considered. However, since the rank of the detection-related matrices in SCDMA is usually high, the complexity is extremely high, even linear detectors, such as decorrelating, minimum mean-square error (MMSE), etc. are employed. In this paper the reduced-rank detection scheme, which is derived based on the Taylor polynomial approximation (TPA), is proposed for detecting the SCDMA signal. The bit error rate (BER) performance of the MIMO SCDMA is investigated, when communicating over frequency-selective fading channels. It can be shown that the considered reduced-rank detection is capable of achieving a BER performance that is close to that of using full- rank detection, but with significantly lower detection complexity.

For the past decade, the demand for personal communications services has been increasing dramatically. Wireless systems provide the most promising means of telecommunications. Currently, three channel access schemes are mostly considered: Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA). There has been much interest in CDMA techniques as an alternative to both TDMA and FDMA methods in wireless communications systems. Among the advantages of CDMA is its ability to combat multipath fading of the radio link due to the frequency diversity offered by the wideband nature of its signal. CDMA offers potential capacity increases over the narrowband techniques. This capacity increase is mainly due to the fact that CDMA performance is interference-limited whereas narrowband systems are bandwidth-limited.

The communication system of self-driving vehicles has characteristics that reason its characteristic performance obstacles: rapidity of the vehicle, fast change topology, lack of a fixed protection system, undefended medium communication and density of vehicles. All these obstacles made autonomous vehicles expose big challenges before explicitly on roads. However, we proposed new communication system which help driverless vehicles to overcome these obstacles. In more details, communication system of cars is heavily depended on efficient scheme that is code division multiple access (CDMA), more details in next section [37,38].

OCDMA (Optical Code Division Multiple Access) is a huge research area where it attracts many interesting research for decades. The importance of the system lies in the acquisition of certain characteristics that allow it to be interesting technique such as flexibility in high speed access network, high security, dynamic bandwidth assignment, large and effective bandwidth utilization [1]. OCDMA can be divided into five important schemes: frequency hopping [2], [3], time spreading [4], [5], spectral amplitude coding (SAC) [6], [7] and spatial coding [8], [9]. Due to the ability of suppression of Multiple Access Interference (MAI) completely by the spectral coding and mitigation Phase Induced Intensity Noise (PIIN), the spectral amplitude coding (SAC- OCDMA) has attracted a more interest recently [10], [11].

Digital Code Division Multiple Access (CDMA) scheme allows many users to transmit and receive at the same time using a single channel. CDMA techniques can use synchronous or asynchronous mechanisms. The work in this paper uses the less studied asynchronous mechanism. The transmitter and receiver are synchronized with the help of a delay element. The simulation and synthesis carried out using VHDL tool shows minimum power consumption and an increase in the overall speed of the system.

This paper provides the idea of performance of multi user optical code division multiple access asynchronous net- works with bit error rate and multiple access interference with the help of encoding process along with EDFA structure. Proposed scheme architecture provides less interference as compared to the normal optical code divi- sion multiple access networks. Multiple access interfe- rence is always been a limitation factor in optical CDMA networks and we have tried to refine the communication by decreasing the interference and bit error rate. Experi- mentation considers 6 users for the communication struc- ture and shows similar results as suggested by interfe- rence cancellation technique with differential detection process.

In a CDMA system, the different users can be identified and, hopefully, separated at the receiver by means of their characteristic individual signature pulses (sometimes called the signature waveforms), that is, by their individual codes (Schulze and Lǜders, 2005). The conventional code division multiple access technique used in third generation system faces serious limitations by channel dispersion, causing inter symbol interference (ISI), and it requires advanced signal processing algorithms to contain it. Multi carrier CDMA (MC-CDMA) employing multiple stream of data channel can combat channel dispersion, hence ISI, thereby increasing system capability to accommodate a higher number of users and its data rate requirements (Kumar and Chellappan, 2009).

For a long time, personal authentication issue has received more attention in people's daily lives, law enforcement, and business. The purpose of personal authentication is to confirm or determine the identity claims by individuals. Besides its applications has been widely used in building access, automatic systems, computers and mobile phones [1]. Personal authentication serves both verification and identification, each has a specific application. the verification mode, based on one-to- one comparison to check whether a person's identity is as requested; whereas, the identification mode, based on one-to-many comparisons in order to distinguish the person's identity. Traditionally, the personal authentication process is based on what you hold (e.g. keys and ID cards) or what you know (e.g. passwords). Approaches like this have several drawbacks. First, the user can lose or forgotten has knowledge and tokens. Second, the perpetrator can plead that the ID card or his password was stolen and deny their wrongdoing. Third, there is 'spoofing' attack risk, so that any person who has the key can access all services. Further, the people

the value is a number of multiple of tapes, because the number of columns in standard Turing matrix is a multiple of tapes (=t |S|), in the first tape q=0, in the second tape q=1, then in the τ’th tape q=τ-1, then

Recently, Vehicular Ad-hoc Networks (VANET) becomes more popular and widely deployed all over the roads across the world. Most of modern cars are equipped with Wireless modules which provides vehicles to communicate with each other’s and with communication control points [1]. Enhancing Inter-Vehicle communication and roadside communication are considered as the most popular wireless communication research topic. VANET allows road vehicles to notify other vehicles about traffic jams, sudden stops and other hazardous road conditions[2]. The huge number of expected benefits of VANET and number of supporting vehicles are likely become the most realized implementation of mobile Ad hoc networks Short range IEEE 802.11 can be used for vehicles communications using suitable radio interface technology[3]. However a new slandered for both physical and MAC layer has been developed to meet the requirement of communication between vehicles, IEEE 802.11p [4] is an approved amendment to the IEEE 802.11 standard which provides Wireless Access in Vehicular Environments (WAVE). Enhancements

Today, data security is the main objective to protected personal data from unauthorized access users, because of the high-speed development of unsecured networks. The aim of apply symmetric-key algorithms is to produce a good encrypt data in order to safety transmitted information through unsecure networks; such goal is achieve by design efficient keystream generator mechanism. However, there are many properties should be taken in consideration to design a good ciphers including; implement strong and high- speed keystream generation, utilize a complex invertible round functions, as well as time execution and security level. This paper suggested a new technique for design efficient keystream generator mechanism called Hybrid Chaotic Keystream Generator (HCKG) that is suitable for symmetric image encryption. HCKG generator passes through four stages; firstly, choose the chaotic maps, including, Chebyshev, Tent, Gaussian, Henon, and Duffing maps. The secondly stage, exponential function [exp(x)] and the next stage is machine words multiplexer to find the floating-point representation group of random numbers. The final stage, random matrix table as a dynamic substitution box (S-box) depend on random key, shifting, logistic maps for (1D, 2D, 3D), and particle swarm algorithm. Visual Studio was employed as a programming language to implement the algorithms of proposal system. The output of HCKG is testing in several measurements represent including complexity, time execution and avalanche criterion balance; the numerical results show that the keystream generation successfully passed through NIST (statistical package tests for randomness). Finally, image encryption for the corresponding algorithm was done; preliminary results show that HCKG algorithm has good cryptographic strength and resistant against security attacks. Keywords: Cryptography, Symmetric key, Chaotic Maps, Image encryption, NIST

3. ARTIFICIAL NEURAL NETWORK The Artificial Neural Network (ANN) is a learning algorithm commonly used by multiple layers of perceptron to alter the weight associated with its hidden neurons. Artificial Neural Network is one of representation of the human brain to process simulation on learning. Artificial are used and implemented using computer programs to sort out of a number of calculation process learning. Artificial neural network is determined 3 points: a. Pattern of neural relationship

The total distributed search architecture for all our big datasets is beyond the scope of this paper; for an informal description, we refer the reader to a Twitter real-time engineering blog post. SAMA simply returns a list of tweets that do not satisfy a Boolean query. SAMA is written in Java, Javascript and C-sharp, primarily for three reasons: to take advantage of the existing Lucene Java codebase, to fit into Twitter’s JVM-centric development environment, and to take advantage of the easy-to-understand memory model for concurrency offered by Java and the JVM. Although this decision has inherent performance challenges, with careful engineering and memory management we believe it is possible to build systems that are comparable to real-time performance. SAMA, like most modern retrieval engines, maintains its inverted index concurrently. Postings remain in the front-end before being forwarded to the user in forward chronological order (most recent last), then are traversed backwards (most recent first); this is accomplished by maintaining a pointer to the current end of each posting list. We believe this index organization is an interesting and noteworthy aspect of SAMA. Our model supports different query lengths: one term, two term and phrase, and results are returned in reverse chronological order (most recent first). Query evaluation is relatively straightforward, and we were able to use our Lucene query model algorithm for conjunctive queries corresponding to intersections of posting lists, disjunctive queries corresponding to unions and phrase queries corresponding to intersections with positional constraints. Lucene provides abstractions for posting lists and traversing postings, and we provide implementation for our custom indexes; otherwise, we can reuse existing Lucene query evaluation code. The actual query evaluation algorithm isn’t particularly interesting, but how we handle concurrency (i.e. concurrent index reads and writes) in a multi-threaded framework is certainly worth discussing. The following section addresses this.

The values got for the compatibility factor of IT flexibility, showed that compatibility significant in cloud deployed systems. The lowest average values were gotten with respect to cloud based systems deployed enterprise to accomplish integration, regardless of whether companies are limited by their decision of operating systems (OS), and whether software applications can be effortlessly transported and utilized platforms or across several cloud providers. The findings showed that cloud based systems avoid users from choosing their favored operating system, or transferring their software application among cloud based systems, and that cloud based systems delay access to outside users, which in thusly make cloud implementation more compatible. This research results were reliable with previous studies which determined that a positive correlation exists between IT flexibility and IT effectiveness Tallon

ABSTRACT This paper addresses the problem of global practical output tracking for a class of high-order time-delay uncertain non-linear systems via state feedback.. On the basis of the h[r]

Based on the calculation of the production costs described in table 1, the profit of each type of Batik Madura among-others Batik Tulis with one coloring is IDR 12,832; Batik Tulis with [r]