Orthogonal frequency division multiplexing (OFDM) is a superior technology for the high-speed data rate of wire-line and wireless communication systems. The OFDM has many advantages over other techniques such as its high capacity and immunity against multipath fading channels. However, one of the main drawbacks of the OFDM system is the high-peak-to-average power ratio (PAPR) that leads the system to produce in-band distortion and out-of-band radiation because of the non-linearity of the high-power amplifiers. Therefore, numerous techniques have been proposed to overcome the PAPR problem such as selective mapping, partial transmit sequence (PTS), clipping, and nonlinear companding. In this paper, the PTS technique was analytically reviewed as one of the important methods to reduce the high PAPR problem. The PAPR performance and the computational complexity level are discussed in terms of modifying the PTS technique in the frequency domain, time domain and modulation stage (inverse fast Fourier transform block). Moreover, the numerical statistic comparison of the current modified-PTS methods is introduced, and the criteria for selecting the suitable modified-PTS method in the OFDM system are also given. The simulation and the numerical calculations results show that the rows exchange-interleaving PTS scheme is the best method for reducing the PAPR value with low complexly in the frequency domain, and the cooperative PTS method is the best among the modulation stage methods, while the cyclic shift sequence PTS method achieves the superior performance in PAPR reduction and computational complexity for the time domain methods.

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A Review of Partial Transmit Sequence for PAPR Reduction in the OFDM Systems

In order to overcome the effect of the Multiple Access Interference (MAI) and noises, and increase the number of the simultaneous users, the multiplexing capacity and data rate, this paper proposes a novel design of a two dimensional spectral/spatial code named Two Dimensional-Single Weight Zero Cross Correlation (2D-SWZCC) based on a single weight code which is characterized by a zero cross correlation and a high number of users. The proposed code is developed to be implemented in non-coherent Optical Code Division Multiple Access (OCDMA) systems. Numerical results of the design construction show that the proposed code enhances the system performance by improving its capacity, reducing the signal-to-noise ratio, and increasing the data rate. The system output performance for active user number is equal to 1.09, 1.54, 2.14, 2.215, 3.89 and 5.14 times than those of, Two Dimensional Multi-Diagonal (2D-MD), Two Dimensional Dynamic Cyclic Shift (2D-DCS), (1D-SWZCC), Two Dimension Perfect Difference (2D-PD), Two Dimensional Hybrid Flexible Cross Correlation- Modified Double Weight (FCC/MDW) and Two Dimensional Extended Enhanced Double Weight (2D-extended-EDW) codes, respectively. It can save an effective power around −3.2 dBm and −1.4 dBm at the level of the receiver compared to 2D-DCS and 2D-MD codes. Moreover, the system performance has been studied using Optisystem software. The simulation results show that the system respects the optical transmission property accommodating four users for a power of the source equal to −10 dBm, and the data rate is 1 Gbps.

Development of a novel two-dimensional-SWZCC - Code for spectral/spatial optical CDMA system

Development of new two-dimensional spectral/spatial code based on dynamic cyclic shift code for OCDMA system

Spectral/spatial optical CDMA code based on Diagonal Eigenvalue Unity

This article presents a detailed survey on both asynchronous and synchronous Optical Code-Division Multiple-Access (OCDMA) systems based on 1-D, 2-D, and 3-D codes, distinctively. Accordingly, different coding schemes along with their multiplexing capacity, correlation features, advantages and drawbacks are addressed and benchmarked. Additionally, different detection techniques such as direct and coherent detection and their capability to handle Multiple Access-Interference are also discussed. Furthermore, the main OCDMA systems from the last two decades are summarized considering their coding schemes, performance, device components, and applications. Therefore, a new comparative study in terms of spectral efficiency and bit error rate for 1-D, 2-D, and 3-D asynchronous and synchronous OCDMA systems is carried out. Numerical results shown that the 3-D MD code stands out among the codes with superior performance as well as support to higher data rates and number of users.

A Comparative Study of Asynchronous and Synchronous OCDMA Systems

A new two dimensional spectral/spatial multi-diagonal code for noncoherent optical code division multiple access (OCDMA) systems

Orthogonal frequency division multiplexing (OFDM) is a promising modulation technique for transmitting large amounts of digital data through radio waves. One major drawback in OFDM communication is peak-to-average power ratio (PAPR). Mainly because of the nonlinearity of the high power amplifier, these results in high out-of-band radiation, inter-carrier interference, and bit error rate performance degradation. Partial transmit sequences (PTS), an attractive technique of PAPR reduction, provides significant PAPR reduction performance for (OFDM) signals. It essentially involves partitioning the OFDM data frame into disjoint sub-blocks. Adjacent partitioning (AP) scheme can be regarded as the best of the existing partitioning schemes when PAPR reduction performance and cost are considered together. In this paper, we study the impact of the size of PTS partitions on the performance through varying the size of the disjoint sub-blocks partition and comparing the PAPR reduction performance of three well known sub-block partitioning schemes namely Adjacent Partitioning (AP), Interleaved Partitioning (IP) and Pseudorandom Partitioning (PRP). Simulation results showed that performance of these PTS schemes largely depends on the chosen size of the partitions.

Performance of PTS techniques with varied partition size in PAPR reduction of OFDM system

The design of the code is an important issue in an OCDMA systems, in which it can be constructed in one dimension or multi-dimensions. The two dimensional (2-D) code provides high spectral density and large number of subscribers. In this paper a literature review on noncoherent 2-D code families of OCDMA system is presented. The 2-D code is constructed by spreading the optical pulses in two dimensions. Generally, three popular schemes of 2-D OCDMA: spectral/time, spectral/spatial and time/spatial schemes. The most popular schemes are spectral/time and spectral/spatial. In the spectral/time, a different wavelengths are spread in different time slots. While the wavelengths are spread into many optical fibers in spectral/spatial scheme. Each scheme has a merits and demerits so that a tradeoff must be made to choose the suitable scheme for a specific application.

Review on two dimensional code of noncoherent OCDMA systems

Peak-to-Average Power Ratio (PAPR) reduction is an attractive research topic among the OFDM transmission research communities. Partial Transmit Sequence (PTS) has been a promising candidate out of the proposed PAPR reduction techniques without any distortion. In any PTS system, partitioning of the OFDM frame into disjoint sub-blocks is a crucial step. Adjacent partitioning (AP) is a rather simple partitioning scheme achieving attractive PAPR reduction performance. In this paper, we investigate effects of the length variability of disjoint sub-blocks on AP based PTS systems. In order to compare performance of variable length adjacent partitioning with the ordinary PTS scheme, we simulated other partitioning schemes, namely, interleaved, pseudorandom and fixed length adjacent partitioning for various types of modulation. Simulation results showed that the variable length adjacent partitioning is better than interleaved partitioning. However, it has worse PAPR reduction performance compared to the traditional adjacent and pseudorandom techniques.

Effect of partition length variability on the performance of adjacent partitioing PTS in papr reduction of OFDM systems

In this research we study the elevations of cities and the water resources specially at the dams reservoirs and the distance between them(dams & cities), we use the Google Earth program to determine these elevations and calculate the difference between the average level (elevation) of water at the dam and the average level of cities, which we want to supply it by water, in order to save electrical power by using the energy of supplied water through pipe line from dams to the cities, the pressure of supplied water must be calculated from the difference in elevations(head). The saving of energy can be achieved by two ways. The first is the energy saving by reduce the consumed power in the pumping water from river, which is used for different purposes. The second is the hydroelectric power generated by establishing a micro hydroelectric generator on the pipe line of the water supplied.

Using water energy for electrical energy conservation by building of micro hydroelectric generators on the water pipelines that depend on the difference in elevation

Rasim Azeez Kadhim

Papers

A new two dimensional spectral/spatial multi-diagonal code for noncoherent optical code division multiple access (OCDMA) systems

Performance of PTS techniques with varied partition size in PAPR reduction of OFDM system

Review on two dimensional code of noncoherent OCDMA systems

Effect of partition length variability on the performance of adjacent partitioing PTS in papr reduction of OFDM systems

Using water energy for electrical energy conservation by building of micro hydroelectric generators on the water pipelines that depend on the difference in elevation