A fair comparison of SAC-OCDMA system configurations based on two dimensional cyclic shift code and spectral direct detection

This paper investigates shortcomings that limit the performance of optical code division multiple access (OCDMA) systems including the low cardinality and data rate as well as the high power at reception. The main drawback for such systems known as multiple access interference accompanying by phase induced intensity noise is also investigated to effeciencly propose a novel two dimensional cyclic shift (2D-CS) code to be implemented in non-coherent OCDMA systems. The developed code is based on a one dimensional cyclic shift (1D-CS) code previously provided by research works processing spectral amplitude coding for optical code division multiple access (SAC-OCDMA) systems. Numerical results obtained by this study are therefore compared to previous studies employing different codes like two dimensional extended double weight (2D-EDW), two dimensional flexible cross correlation/modified double weight (2D-FCC/MDW), two dimensional perfect difference (2D-PD), two dimensional diluted perfect difference (2D-DPD), two dimensional multi service (2D-MS) and two dimensional zero cross correlation/multi diagonal (2D-ZCC/MD) codes. Accordingly, it is demonstrated that the proposed 2D-CS code outperforms all codes given previously in terms of system capacity where the small increasing percentage is about 40% compared to 2D-ZCC/MD and 2D-MS. Systems using 2D-CS code can support until 203 simultaneous users with a total code length equal to 171. System performance investigation leads to a BER and Q-Factor closely to1.0E?12 and 1.0E?27, and 6.6 dB and 10.6 dB at 20 km of single mode fiber length using white light source and Laser, respectively. Furthermore, such a code can be easily adopted by OCDMA systems for a long distance up to approximately 55 and 100 km.

     

Nonlinear Product Codes and Their Low Complexity Iterative Decoding

This paper proposes encoding and decoding for nonlinear product codes and investigates the performance of nonlinear product codes. The proposed nonlinear product codes are constructed as N‐dimensional product codes where the constituent codes are nonlinear binary codes derived from the linear codes over higher order alphabets, for example, Preparata or Kerdock codes. The performance and the complexity of the proposed construction are evaluated using the well‐known nonlinear Nordstrom‐Robinson code, which is presented in the generalized array code format with a low complexity trellis. The proposed construction shows the additional coding gain, reduced error floor, and lower implementation complexity. The (64, 24, 12) nonlinear binary product code has an effective gain of about 2.5 dB and 1 dB gain at a BER of 10^?6 when compared to the (64, 15, 16) linear product code and the (64, 24, 10) linear product code, respectively. The (256, 64, 36) nonlinear binary product code composed of two Nordstrom‐Robinson codes has an effective gain of about 0.7 dB at a BER of 10^?5 when compared to the (256, 64, 25) linear product code composed of two (16, 8, 5) quasi‐cyclic codes.     

One-Level Simplification Method for All-Optical Combinational Logic Circuits

We propose a novel one-level simplification method for all-optical combinational logic circuits. With the proposed method, an all-optical gray code to binary coded decimal converter is successfully developed for the first time by using conventional semiconductor optical amplifiers as building elements. In comparison to the construction algorithm based on the conventional two-level simplification method, a significant improvement is observed in the Q-factor.     

A modified topology achieved in OFDM/SAC-OCDMA-based multi-diagonal code for enhancing spectral efficiency

In this paper, a modified topology-based orthogonal frequency division multiplexing–spectral amplitude coding in optical code division multiple access (OFDM–SAC-OCDMA) has been introduced. Such analysis aims to explain the effect of spectral efficiency with respect to multi-diagonal (MD) code. The new proposed technique introduces a fusion system between the two-code keying scheme and the forward error correction (FEC). The introduced analysis has targeted the effect of signal-to-noise ratio, bit error rate, and spectral efficiency with the presence of beat noise, phase incoherent intensity noise, and thermal noise. Numerical simulations have been utilized and tested in order to illustrate the validation of the (MD) code method to eliminate dominant noise. The calculation results show the following; the SNR and BER for MD under the presence of the previous discussed signal degradation is equal 161 and 1.2?×?10^?10, respectively, according to a predefined number of users 150 comparing with some existing codes such as: modified frequency hopping code, Hadamard (HD) code, modified quadratic congruence code. The proposed unipolar encoding with direct detection technique-based OFDM/SAC-OCDMA scheme achieves an enhancement in the performance of SE over the unipolar encoding with direct detection technique-based SAC-OCDMA technique by 3.455 dB. The proposed two keying scheme-based OFDM/SAC-OCDMA introduces an enhancement in the performance of the SE over the unipolar encoding with direct detection technique-based OFDM/SAC-OCDMA technique by 2.8859 dB. FEC has been applied in order to increase the spectral efficiency for different BERs, which the numerical results show that FEC provides 1.7457 dB. Finally, the total enhancement for SE was about 8.0866 dB.

     

All-optical four-wavelength 2R regeneration based on data-pump four-wave-mixing with offset filtering

A simultaneous all-optical 2R regeneration of 4 × 12.5 Gb/s return-to-zero (RZ) signals is demonstrated based on the data-pump four-wave-mixing in a single highly nonlinear fiber, in which the channel spacing and duty cycle are 200 GHz and 50%. Both the bidirectional configuration and time-interleaved technology are used to reduce the crosstalk from other channels. For further improving the performance of the multichannel regenerator, an offset filtering (OF) method is employed to minimize the influence from the opposite input signal. Our experiments show that the extinction ratio (ER) of regenerated signals is about two times larger than that of the degraded signals and the maximum ER improvement is about 6.5 dB. By using the offset filtering method, the sensitivity improvements of four-wavelength regenerated signals are 2.05 dB, 2.53 dB, 3.57 dB and 2.8 dB, respectively.     

2D/3D Shaped Radiation Patterns of Sunflower and Conformal Antenna Arrays Using Phase Synthesis

2D and 3D beam synthesis from different antenna array arrangements are investigated in this paper. Planar sunflower, conformal cylinderical and spherical helical array arrangements are studied. The particle swarm optimization (PSO) technique is used to predict the phase distribution on the array elements. The beam synthesis is achieved by comparing the array factor with a predetermined mask with both upper and lower limits according to the intented application requirements. Different 2D and 3D masks are used in beam synthesis as pencil, flat-top, and cosecant single beam are predicted. The planar sunflower antenna array is investigated due to its high gain, low side-lobe level (SLL) below ??20 dB and its compact size. The phase distribution of sunflower array is estimated using PSO to radiate dual-beams in different planes. Dual-beam with pencil, flat-top, and cosecant beams are obtained with different half-power beam widths. 3D conformal antenna arrays of cylindrical and spherical helical arrangements are studied. Each 3D conformal array consists of four arms shifted in position by 90° orintation angle. Each arm is designed to radiate single beam in a specific direction. Four-beams are considered to radiate in the directions of θ_1,2,3,4?=?30°, and ?₁?=?0°, ?₂?=?90°, ?₃?=?180°, and ?₄?=?270° with SLL optimized below ??17 dB. The array arrangements analysis is based on the array theory formulation, through the implemention of the estimiated equation using a home programmed MATLAB code.

     

No-reference analysis of decoded MPEG images for PSNR estimation and post-processing

We propose no-reference analysis and processing of DCT (Discrete Cosine Transform) coded images based on estimation of selected MPEG parameters from the decoded video. The goal is to assess MPEG video quality and perform post-processing without access to neither the original stream nor the code stream. Solutions are presented for MPEG-2 video. A method to estimate the quantization parameters of DCT coded images and MPEG I-frames at the macro-block level is presented. The results of this analysis is used for deblocking and deringing artifact reduction and no-reference PSNR estimation without code stream access. An adaptive deringing method using texture classification is presented. On the test set, the quantization parameters in MPEG-2 I-frames are estimated with an overall accuracy of 99.9% and the PSNR is estimated with an overall average error of 0.3 dB. The deringing and deblocking algorithms yield improvements of 0.3 dB on the MPEG-2 decoded test sequences.     

Beam-Steerable Ultra-Wide-Band Miniaturized Elliptical Phased Array Antenna Using Inverted-L-Shaped Modified Inset Feed and Defected Ground Structure for 5G Smartphones Millimeter-Wave Applications

Multi Input Multi Output (MIMO) and phased array systems are considered a key technologies to realize the 5G communication systems. Therefore, the purpose of this research is the suggestion of a novel mm-wave Ultrawide Band (UWB) antenna design with compact and straightforward layout suitable for both MIMO and phased array systems. Hence, the designed antenna array has been studied separately as a MIMO antenna and as a phased array antenna to carefully assess the performance of each system. The single antenna design is an elliptical patch antenna where the design novelty lies in the combination of a modified inset-feed and defected ground structure to provide a large bandwidth without any compromise in the radiation performance, nor in antenna size and design simplicity. The Design process are performed using CST MWS software, where the Rogers RT/Duroid 5880 substrate is chosen to construct the antenna. A broadband characteristic of 8.7 GHz from 26 to 34.7 GHz with two resonant frequencies at 28 GHz and 33 GHz is obtained. A good radiation properties are achieved, where the gain is greater than 4.5 dB while the radiation efficiency exceeds 97% over the operating band. The MIMO and phased array antennas are made up of 12-elements of the single UWB-antenna arranged linearly along the width-edge of the smartphone mainboard. The MIMO antenna proves a high diversity performance in terms of Diversity Gain (DG), Envelope Correlation Coefficient (ECC), Total Active Reflection Coefficient (TARC), Channel Capacity Loss (CCL) and Mean Effective Gain (MEG), owing to the low mutual coupling less than ??20 dB, which is obtained using a separating slits between the elements. In addition, the suggested phased array provides a highly stable gain up to 15 dB over the entire bandwidth at broadside direction, besides the wide scanning range of?±?60° at 28 GHz and?±?40° at 33 GHz. Hence, the attained results assure that the suggested antenna could be appropriate for incorporation in 5G smartphones and other wireless devices and can be effectively used for both phased array and MIMO applications.

     

3–5 GHz FSK-OOK ultra wideband transmitter based on memristive ring oscillator

The compatibility of a memristor with CMOS technology has attracted the attention of many researchers to explore its application further. In this work, an ultra low-power and low-complexity ultra wideband (UWB) chirp transmitter based on memristive ring oscillator (RO) is designed in 0.18 µm TSMC CMOS technology. The Chirp waveform was chosen because of its low side-lobes and large time-bandwidth product, which allows for more spectrum use. OOK and FSK modulation are supported by the proposed UWB chirp transmitter. The chirp frequency is controlled linearly with time across the pulse duration using memristors. The binary data "1" and "0" are encoded using distinct chirp frequencies in FSK TX. The simulation results show a maximum TX output pulse of 457 mV _Vpp with a pulse width of 21 ns. The overall DC power consumption for a pulse repetition frequency (PRF) of 20 MHz is 0.328 mW, equivalent to an energy consumption of 16.4 pJ/pulse. The simulated output amplitude for OOK TX is 453 mV Vpp with a pulse width of 48 ns and a PSD of ? 10 dB over a frequency range of 3.2 to 4.8 GHz. The overall power consumption at 10 MHz PRF is 0.136 mW, which corresponds to an energy consumption of 13.6 pJ/pulse.

     

Performance enhancement of BPSK-SIM- and DPSK-SIM-based FSO downlink over atmospheric turbulence using aperture averaging and receiver diversity

In this paper, we evaluate the bit error rate (BER) performance of a free-space optical satellite downlink by considering the atmospheric turbulence effects using binary shift keying subcarrier intensity modulation and differential phase shift keying subcarrier intensity modulation (DPSK-SIM). The performance of the link is enhanced using aperture averaging and receiver diversity. The closed form mathematical expressions of BER for BPSK-SIM and DPSK-SIM schemes are derived and analyzed. It is observed that on varying the turbulence level, the performance of the link degrades when the turbulence level increases. The improved BER of 10^?12 and 10^?10 at signal-to-noise ratio of 30 dB of the link for both BPSK-SIM and DPSK-SIM is obtained by using aperture averaging (aperture diameter, D?=?10 cm) and receiver diversity with optimal combining.

     

Tri-Band Two Elements Antenna

In this work, an antenna that consists of two connected radiating elements is presented. The antenna has three operating bands, namely 2.5 GHz band, 3.5 GHz band, and narrow or wide 5.5 GHz band. To get a narrow 5.5 GHz band, a band-reject filter that eliminates the higher part of the third operating band is used. Measurements show that the antenna gain is 3.1 dB at 2.5 GHz; meanwhile at 8 GHz it has a gain of 4.9 dB. Adding a metallic reflector, a maximum gain of 5.8 dB has been measured at 3.7 GHz.

     

High Performance Microstrip Low Pass Filter for Wireless Communications

A microstrip low-pass filter using T-shaped resonators is designed to achieve an ultra-sharp transition band and high suppression level. The performance of the resonators is investigated based on an LC equivalent circuit and a transfer function to compute the equations of the transmission zeros. This filter has an acceptable stopband with high insertion loss (28 dB) by adopting a rectangular suppressor. Also, the width of the transition band is 0.09 GHz (with – 3 and ? 40 dB attenuation levels), that exhibits a very high sharpness (ξ = 411 dB/GHz). The proposed filter with a 3 dB cut-off frequency (f_c) of 1.32 GHz presents a high return loss in the passband (17 dB) and high figure of merit of 57,073. The designed filter is fabricated and measured, demonstrating sufficient agreement between the simulation and experimental results.

     

准循环多进制LDPC码构造

该文研究准循环多进制LDPC码的构造,给出多进制LDPC码的设计流程和构造方法.详细讨论了多进制LDPC码的性能影响因素,综合考虑了环长和环的连通性对性能的影响,研究了母矩阵扩展中偏移因子的选择以及GF(q)上非零元素替代.同时提出了次优解的搜索方法,以降低搜索复杂度.最后,将提出的方法用于不同阶数下LDPC码的构造.仿真结果表明,通过新方法构造得到的多进制LDPC码与二进制码相比,在BPSK调制方式下在误帧率10-4附近有0.2 dB的性能提升;在有限域阶数与调制阶数匹配的情况下,有更大的性能提升.与相近码长,相同码率的多进制循环码相比,该文构造得到的多进制LDPC码在误帧率10-4附近有0.25 dB的性能提升.     

Mutual Coupling Reduction of MIMO Antenna Array Using Meta-FCRR

In order to reduce mutual coupling interference of between both adjacent antenna elements, a practical scheme for metamaterial is reported in this paper. The study shows that the permittivity and permeability of metamaterial based on fold complementary ring resonator (FCRR) can well be anastomosed in electromagnetic field. The antenna array using co-planar waveguide mode to expound the multiple input multiple output (MIMO) performance are further proposed. The results of simulated antenna array with FCRR indicate that the coupling of about 30.5 dB, 14 dB and 20.2 dB are reduced at resonance frequency (at 2.4 GHz, 6.15 GHz and 9.2 GHz). Meanwhile the experimental measure results can meet the simulation data. Additionally, the envelope correlation coefficient (ECC), diversity gain (DG), voltage standing wave ratio (VSWR) are better characteristics in contrasting to without FCRR, making the solution viable for MIMO antenna arrays.

     

Design and analysis of integrated all-optical $$2\times 4$$ decoder based on 2D photonic crystals

In the development of the technology of all-optical integrated circuits, the logic gates play considerable role in the progress of optical components. As one of the main building-blocks of an optical system, a high-performance 2*4 all-optical decoder is proposed and studied based on nonlinear effects in a photonic crystal ring resonator. The proposed structure consists of 1*2 decoders which are combined to operate as a unique 2*4 decoder and this will let us to extend the design to decoders with increased inputs. An optical bias is used to interact with input signals, and each output port is enabled for a given code in the input code. Numerical simulation methods such as plane wave expansion and finite difference time domain are performed to study the operation of proposed structure. Results of simulations show that for an on-state output, the highest achievable power is about 87% and the lowest value is 40%. For the case of 40%, the on/off ratio of outputs is at least 2.22 which ensures the acceptable resolution needed for detection of on-state. Maximum cross-talk about ?10 dB and insertion loss about ?8.8 dB is obtained for proposed decoder.     

A Reconfigurable TDMP Decoder for Raptor Codes

A Raptor code is a concatenation of a fixed rate precode and a Luby-Transform (LT) code that can be used as a rateless error-correcting code over communication channels. By definition, Raptor codes are characterized by irregularity features such as dynamic rate, check-degree variability, and joint coding, which make the design of hardware-efficient decoders a challenging task. In this paper, serial turbo decoding of architecture-aware Raptor codes is mapped into sequential row processing of a regular matrix by using a combination of code enhancements and architectural optimizations. The proposed mapping approach is based on three basic steps: (1) applying systematic permutations on the source matrix of the Raptor code, (2) confining LT random encoding to pseudo-random permutation of messages and periodic selection of row-splitting scenarios, and (3) developing a reconfigurable parallel check-node processor that attains a constant throughput while processing LT- and LDPC-nodes of varying degrees and count. The decoder scheduling is, thus, made simple and uniform across both LDPC and LT decoding. A serial decoder implementing the proposed approach was synthesized in 65 nm, 1.2 V CMOS technology. Hardware simulations show that the decoder, decoding a rate-0.4 code instance, achieves a throughput of 36 Mb/s at SNR of 1.5 dB, dissipates an average power of 27 mW and occupies an area of 0.55 mm².     

A novel scheme of all optical header extraction for optical packet switching network

A novel scheme of all optical header extraction using a semiconductor optical amplifier-Mach-Zehnder-Interferometer with asymmetric control light is proposed for optical packet switching with all-optical header processing at a header rate of 20 Gb/s and payload rate of 80 Gb/s in this article. The scheme parameters are discussed and analyzed to optimize the performance of optical header extraction with the proposed scheme. Numerical analysis and simulation show that a more than 17 dB contrast ratio can be achieved for the optical header separation when the input optical signal energy is as low as 0.2 pJ. In addition, the system structure is simple, stable, and photonic integratable.     

Source-channel optimized trellis codes for bitonal imagetransmission over AWGN channels

We consider the design of trellis codes for transmission of binary images over additive white Gaussian noise (AWGN) channels. We first model the image as a binary asymmetric Markov source (BAMS) and then design source-channel optimized (SCO) trellis codes for the BAMS and AWGN channel. The SCO codes are shown to be superior to Ungerboeck's codes by approximately 1.1 dB (64-state code, 10^-5 bit error probability), We also show that a simple “mapping conversion” method can be used to improve the performance of Ungerboeck's codes by approximately 0.4 dB (also 64-state code and 10 ^-5 bit error probability). We compare the proposed SCO system with a traditional tandem system consisting of a Huffman code, a convolutional code, an interleaver, and an Ungerboeck trellis code. The SCO system significantly outperforms the tandem system. Finally, using a facsimile image, we compare the image quality of an SCO code, an Ungerboeck code, and the tandem code, The SCO code yields the best reconstructed image quality at 4-5 dB channel SNR     

A novel gray image representation using overlapping rectangular NAM and extended shading approach

In this paper, inspired by the idea of overlapping rectangular region coding of binary images, we extend the SDS design, which is based on overlapping representation from binary images to gray images based on the non-symmetry and anti-packing model (NAM). A novel gray image representation is proposed by using the overlapping rectangular NAM (RNAM) and the extended Gouraud shading approach, which is called ORNAM representation. Also, we present an ORNAM representation algorithm of gray images. The encoding and the decoding of the proposed algorithm can be performed in O(n log n) time and O(n) time, respectively, where n denotes the number of pixels in a gray image. The wrong decoding problem of the hybrid matrix R for the overlapping RNAM representation of gray images is solved by using the horizontal, vertical, and isolated matrices, i.e., H, V and I, respectively, which are used to identify the vertex types. Also, we put forward four criteria of anti-packing homogeneous blocks. In addition, by redefining a codeword set for the three vertices symbols, we also propose a new coordinate data compression procedure for coding the coordinates of all non-zone elements in the three matrices H, V and I. By taking some idiomatic standard gray images in the field of image processing as typical test objects, and by comparing our proposed ORNAM representation with the conventional S-Tree Coding (STC) representation, the experimental results in this paper show that the former has higher compression ratio and less number of homogeneous blocks than the latter whereas maintaining a satisfactory image quality, and therefore it is a better method to represent gray images.     

Performance Analysis of Parallel Concatenation of LDPC Coded SISO-GFDM System for Distinctive Pulse Shaping Filters using USRP 2901 Device and its Application to WiMAX

The increasing demand for high data rates requires channel error control codes for the upcoming fifth generation. This article presents an investigation of the parallel concatenation of low-density parity-check codes (PC-LDPC) in the fifth generation proposed waveform candidate called generalized frequency division multiplexing (GFDM). PC-LDPC codes are obtained by dividing the long and high complexity single LDPC codes into small two lower complexity codes, and these designed codes are applied to the 5G-GFDM waveform. Since the GFDM signal transmits data in both the time and frequency domain, these PC-LDPC codes can deal with two-dimensional errors. This channel coded GFDM system is integrated into Universal software radio peripheral (USRP) device for real-time implementation. The Attainment of the proposed transceiver is verified by computation of BER under distinctive channel coding techniques like convolutional, Golay, Bose-Chaudhuri-Hochquenghem (BCH), extended length single LDPC code. The different pulse shaping filters such as Raised Cosine (RC), Root Raised Cosine (RRC), Gaussian, and Xia 4th order filter are applied to the GFDM under the Gaussian noise and Rayleigh fading channel to compute Out of band (OOB) power. The PC-LDPC coded GFDM outperforms LDPC by 6.5 dB in the RRC filter for roll-off factor rate 0.5 under the Rayleigh fading channel. PC-LDPC code outperforms LDPC code with a coding gain of 2 dB was observed in IEEE 802.16 Transceiver.