16-QAM OFDM Research Articles

A Combinatorial Impairment-Compensation Digital Predistorter for a Sub-GHz IEEE 802.11af-WLAN CMOS Transmitter Covering a 10x-Wide RF Bandwidth

A new combinatorial impairment-compensation digital predistorter (DPD) for a sub-GHz IEEE 802.11af-WLAN CMOS transmitter (TX) is proposed. For the TX to cover a 10x-wide bandwidth, the DPD implements a modified dynamic deviation reduction (DDR)-based Volterra series to jointly nullify the frequency-dependent I/Q imbalance, counter-intermodulation (CIM) of mixers, and nonlinearities of power amplifier (PA) with memory effect. The interactions of those impairments are firstly analyzed using two Volterra series. After applying the tandem properties of Volterra series, interactions of all impairments can be described in one Volterra series by bonding those impairments in parallel. Coefficients of the DPD are extracted with the LeastSquare (LS) estimator, achieving lower running complexity than the existing DPDs, which were developed to handle the PA nonlinearities only. Verifications are based on both system-level simulations and silicon measurements of a 65-nm CMOS TX prototype. When the TX delivers a 6-MHz bandwidth, 2048-point, 64-QAM OFDM signal at > +10 dBm output power, the measured EVM is <;3.7% and adjacent channel leakage ratio (ACLR) is <; -40.2 dBc under individual DPD applied at each RF. A novel one-shot calibration for reuse in the entire TV-band is demonstrated also, showing EVM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&lt;;</sub> 4.2% and ACLR <; -39.8 dBc.

English

Cooperative wireless communication relay networks in OFDM-based systems have been shown to improve performance in various systems using digital modulation techniques as a form of spatial diversity, this method indeed improves the performance in comparison in various aspects of BER and SNR with fixed and random values of input applied on functions on FFT, IFFT, mixing of each other etc. to existing when filtering is necessary for band limited conditions. In this proposed paper, we are implementing the better and updation in results with the mathematical calculation in FFT, IFFT, and mixing of algorithms and terminology interfacing over the range of 256 and 512 - ary QAM OFDM techniques which are useful in communication scenarios. Scattering and conjugate plots are added for 256 and 512ary are implemented for orthogonal transmission, overlapping, narrow band sub channel or sub-carriers, transmitted in parallel data over transmission bandwidth.

Reusing Downstream Carrier in Colorless Laser Diode for Full-Duplex 64-QAM OFDM

Without the need of any inline data eraser, the downstream carrier is reused in an upstream colorless laser diode transmitter to demonstrate full-duplex bidirectional 64-QAM OFDM passive optical network (PON) at up to 18 Gb/s. Therein, the downstream signal is used to control the wavelength of upstream laser diode by injection locking, and the slave laser diode then generates the injection-locked carrier for carrying the upstream signal. Distributing the OFDM subcarriers into dual frequency regions for upstream (baseband at 0-3 GHz) and downstream (up-shifted band at 3-6 GHz) transmissions avoids the crosstalk and simplifies the full-duplex system. The downstream power splitting ratio of 60/40 is optimized for receiving/injection branches at user end. For the downstream 64-QAM OFDM data after propagating 25-km SMF, a sensitivity of received power at least -8.5 dBm is required to suppress the BER below 3.8 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> for the forward-error correction (FEC) criterion. When directly reusing the downstream carrier with unerased data to injection-lock the colorless laser diode, the 25-km SMF transmitted upstream 64-QAM OFDM data exhibits an SNR of 22.9 dB and an error vector magnitude of 4.1%, which provides a BER of 1.5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> at a received power of -5.8 dBm. Such a downstream carrier reused colorless laser diode upstream transmitter with inline eraser-free operation has shown its applicability for full-duplex quadrature amplitude modulation orthogonal frequency-division multiplexing PON.

40 Gb/s 4-QAM OFDM radio over fiber system at 60 GHz employing coherent detection

In this paper, the simulation of 60 GHz millimeter-wave radio over fiber link with 4-QAM OFDM modulation format at 40 Gb/s over 150 km SMF is proposed. The 60 GHz millimeter-wave signal is generated by the optical heterodyne method. Coherent detection has been used at the receiver to down-convert millimeter-wave signal to IF band. Introduction of the OFDM modulation in RoF-based system realizes the benefits of higher order modulations (such as 4-QAM, 16-QAM, etc.) to ensure the good spectral efficiency and multi-gigabit access. The performance of the system is analyzed by Q-factor and BER by which it can be shown that the best results are obtained at the input power of 10 dBm. The simulation results clearly demonstrate the feasibility of this 4-QAM OFDM RoF system over 150 km fiber link.

Chaos Coding-Based QAM IQ-Encryption for Improved Security in OFDMA-PON

In this letter, we propose a quadrature amplitude modulation (QAM) encryption method based on chaos coding for security improvement in orthogonal frequency-division multiple access-based passive optical network (OFDMA-PON) systems. In the encrypted QAM symbols, the real ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">\(I\) </tex-math></inline-formula> ) and imaginary ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">\(Q\) </tex-math></inline-formula> ) parts are separately coded with key sequences, which are generated by a modified Logistic mapping. Iteration parameters of the mapping formula are set as the security keys, which are determined in each optical network unit (ONU) and then sent to optical line terminal (OLT). The key sequences for different ONUs are generated with their corresponding security keys. According to the subcarrier allocation information, downstream signal is encrypted in the OLT and then decrypted in each ONU with distinct key sequences. Encryption of 10-Gb/s 16QAM OFDM and 12.5-Gb/s 32QAM OFDM signals has been successfully implemented over 30-km standard single mode fiber in the security improved OFDMA-PON.

16-3 地デジ方式による4K60p放送の室内実験 : 現行のHD放送と同じOFDM 64QAM 変調によるISDB-T地デジ方式での、4K60p スーパーハイビジョン放送の実現に向けての2014年5月の室内実証実験の報告(第16部門 放送方式2(超高精細映像))

16-3 地デジ方式による4K60p放送の室内実験 : 現行のHD放送と同じOFDM 64QAM 変調によるISDB-T地デジ方式での、4K60p スーパーハイビジョン放送の実現に向けての2014年5月の室内実証実験の報告(第16部門 放送方式2(超高精細映像))

DOUBLE SUPPLY, LINEAR, AND HIGH EFFICIENCY PUSH AMPLIFIER DESIGN FOR ENVELOPE TRACKING POWER AMPLIFIERS IN WiMAX APPLICATIONS

In this work, a novel and efficient approach is proposed to optimize linearity and efficiency of a power amplifier used in mobile communication applications. A linear and high performance push amplifier is designed and analyzed to extract design equations for an optimum performance. The proposed push amplifier has two sections; an analog section and a switching section. The analog section provides the required linearity and the switching section guarantees the satisfaction of the total efficiency level. Double power supply scheme is used in push amplifiers to enhance its performance. Two separate power supplies are employed for linear and switching sections of push amplifiers which have different voltage levels. The implemented circuit is simulated using HSPICERF with TSMC models for active and passive elements. The proposed power amplifier (PA) provides a maximum output power of 25 dBm and power added efficiency (PAE) as high as 51% at 2.5 GHz operation frequency. At 1-dB compression point, this PA exhibits output power of 25 dBm with 48% PAE and 4.5% error vector magnitude (EVM) which is appropriate for 64QAM OFDM signals.

Secure Transmission of 2.5 Gb sec-1 16-QAM OFDM Signal with LDPC Coding in DD-OOFDM Systems

Secure Transmission of 2.5 Gb sec-1 16-QAM OFDM Signal with LDPC Coding in DD-OOFDM Systems

2 &lt;formula formulatype="inline"&gt;&lt;tex Notation="TeX"&gt;$\times$&lt;/tex&gt;&lt;/formula&gt; 2 MIMO OFDM-RoF System Employing LMS-Based Equalizer With I/Q Imbalance Compensation at 60 GHz

Multiple-input–multiple-output (MIMO) technology is a promising method to increase spectral efficiency in wireless communications. In this paper, a 60-GHz orthogonal frequency-division multiplexing radio over fiber (OFDM-RoF) system employing 2 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\times$</tex></formula> 2 MIMO wireless technology is demonstrated. With the proposed equalizer employing least mean squares (LMS) algorithm, MIMO channel mixing and I/Q-mismatch can be compensated simultaneously. 16-QAM and 32-QAM OFDM signal transmissions under forward error correction (FEC) threshold ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$1\times 10^{-3}$</tex></formula> ) are demonstrated. A data rate of 76.3 Gb/s can be achieved with a bit-loading algorithm over 25-km fiber transmission and 3.5-m wireless transmission.

Transmission of 16-QAM OFDM Signal with Secure Strategy Technique in DD-OOFDM Systems

The physical layer of optical access network is vulnerable to various attacks. As the dramatic increase of users and network capacity, the issue of physical-layer security becomes more and more important. This paper proposes a physical-enhanced secure strategy for DD-OOFDM system by employing frequency domain chaos scrambling. The FEC coding can also improve the system performance and will not influence the encrypt process. A 2.5Gb/s 16QAM LDPC-OFDM data with Logistic mapped chaos scrambling are successfully transmitted over 40km SSMF. The results show that security sequences protect the system from attacker and keep a good performance for legal receiver.

Experimental demonstrations of dual polarization CO-OFDM using mid-span spectral inversion for nonlinearity compensation.

We experimentally demonstrate fiber nonlinearity compensation in dual polarization coherent optical OFDM (DP CO-OFDM) systems using mid-span spectral inversion (MSSI). We use third-order nonlinearity between a pump and the signal in a highly nonlinear fiber (HNLF) for MSSI. Maximum launch powers at FEC threshold for two 10 × 80-km 16-QAM OFDM systems were increased by 6.4 dB at a 121-Gb/s data rate and 2.8 dB at 1.2 Tb/s. The experimental results are the first demonstration of using MSSI for nonlinearity compensation in any dual polarization coherent system. Simulations show that these increases could support a 22% increase in total transmission distance at 1.2-Tb/s system without increasing the number of inline amplifiers, by extending the fiber spans from 90 to 110 km. When spans of 80 km are used, simulations reveal that MSSI system performance shows less degradation with increasing transmission distance, and an overall transmission distance increase of more than 70% is expected using MSSI.

Timing, carrier frequency and phase recovery for OFDM and Nyquist signals using a mean modulus algorithm.

Efficient algorithms for timing, carrier frequency and phase recovery of Nyquist and OFDM signals are introduced and experimentally verified. The algorithms exploit the statistical properties of the received signals to efficiently derive the optimum sampling time, the carrier frequency offset, and the carrier phase. Among the proposed methods, the mean modulus algorithm (MMA) shows a very robust performance at reduced computational complexity. This is especially important for optical communications where data rates can exceed 100 Gbit/s per wavelength. All proposed algorithms are verified by simulations and by experiments using optical M-ary QAM Nyquist and OFDM signals with data rates up to 84 Gbit/s.

Experimental demonstration of 30 Gb/s direct-detection optical OFDM transmission with blind symbol synchronisation using virtual subcarriers

The paper investigates the performance of a blind symbol synchronisation technique for optical OFDM systems based on virtual subcarriers. The test-bed includes a real-time 16-QAM OFDM transmitter operating at a net data rate of 30.65 Gb/s using a single OFDM band with a single FPGA-DAC subsystem and demonstrates transmission over 23.3 km SSMF with direct detection at a BER of 10(-3). By comparing the performance of the proposed synchronisation scheme with that of the Schmidl and Cox algorithm, it was found that the two approaches achieve similar performance for large numbers of averaging symbols, but the performance of the proposed scheme degrades as the number of averaging symbols is reduced. The proposed technique has lower complexity and bandwidth overhead as it does not rely on training sequences. Consequently, it is suitable for implementation in high speed optical OFDM transceivers.

OFDM/WDM PON With Laserless, Colorless 1 Gb/s ONUs Based on Si-PIC and Slow IC

We introduce a next-generation long-reach access optical network (35&#xA0;dB loss budget +2&#x2009;&#x2009;dB margin) delivering up to 40G/40G per passive 1&#x2236;256 optical distribution network, supporting symmetrical 1&#x2009;&#x2009;Gb/s rates per home user or up to 40&#x2009;&#x2009;Gb/s for business users (e.g., enterprises, antenna sites). The proposed system is based on a novel spectrally efficient orthogonal frequency division multiplexing/wavelength division multiplexing OFDM/WDM architecture symmetrically using 16-QAM OFDM polarization diversity in both the downstream and upstream in order to serve low-cost energy-efficient symmetric 1&#x2009;&#x2009;Gb/s optical network units (ONUs), which are self-coherent, laserless, colorless, and tunable-filter-free. Each ONU comprises a standard semiconductor optical amplifier (SOA), a silicon-based photonic integrated circuit (PIC), and mixed-signal electronic integrated circuits (ICs) performing the signal processing at a relatively slow rate as compared with the overall passive optical network (PON) throughput: digital to analog converters (DACs) and analog to digital converters (ADCs) at 417&#x2009;&#x2009;MS/s for the home user ONUs.

Signal-carrier interleaved optical OFDM for direct detection optical communication

We propose signal-carrier interleaved (SCI) optical OFDM for direct detected transmission systems. Such a scheme can be considered as a variation of self-coherent detection where the carrier and signal are supplied at the transmitter and extracted at the receiver for coherent-like detection. This provides high OSNR sensitivity while maintaining very low carrier-to-signal power ratio (CSR). Our experiment results show that with 0 dB CSR, 43.2 Gb/s 16 QAM OFDM signal can be successfully delivered over 80 km standard single mode fiber (SSMF) with 24 dB OSNR requirements at 7% FEC limit.

Comparison of Channel Estimation in Mobile WiMAX (IEEE 802. 16e) DL-PUSC System

Fourth generation (4G) wireless based on worldwide interoperability for microwave access (WiMAX) systems are a new promising technology that support high data rate transfer. Channel Estimation of system is carried out by finding Channel impulse response (CIR) of pilot subcarrier using LS or LMMSE algorithms and then finding Channel Frequency Response (CFR) at data subcarrier is done by time and frequency Interpolation of Pilot CIR. This paper presents BER performance for 16QAM & 64QAM Coded OFDM System evaluated at different Doppler frequencies. Results show that Channel Estimation over Coded-OFDM system gives better performance than OFDM.

SSMI cancellation in direct-detection optical OFDM with novel half-cycled OFDM

Half-cycled DDO-OFDM transmission and reception was successfully demonstrated to resist SSMI without spectra efficiency reduction for the first time. The receiver sensitivity was improved by 2 and 1.5 dB in QPSK and 16QAM OFDM with 40-km SSMF-28 transmission, respectively.

A 53-to-75-mW, 59.3-dB HRR, TV-Band White-Space Transmitter Using a Low-Frequency Reference LO in 65-nm CMOS

A TV-band white-space transmitter covering a 16x-wide spectrum from 54 to 864 MHz is described. It features a systematic codesign between the architecture and circuits to address the harmonic-mixing problem. Specifically, it incorporates two-stage 6-/14-path harmonic-rejection mixers and low-Q passive-RC/-CLC filters to manage the unwanted harmonic emission fully on chip, achieving an uncalibrated harmonic rejection ratio (HRR) of minimally 59.3 dB (16 samples) for all in-/out-band harmonics. The employed 8-/16-phase LO generator is based on injection-locked 4-/8-phase correctors and even-ratio-only frequency dividers to save the LO-path power (2.5 to 14.2 mW) while lowering the required reference LO frequency (432 to 864 MHz). Without any predistortion, the EVM tested under a 64-QAM OFDM digital-TV signal is 2.9% at 96 MHz, 3.3% at 384 MHz, and 4.0% at 600 MHz. The first (second) adjacent channel leakage ratio is -46 dBc ( -43 dBc) at 6 MHz (12 MHz) offset. The power consumption is 53.1 to 75.2 mW and active area is 0.93 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> in 65-nm CMOS.

SER Performance of M-ary QAM OFDM System under AWGN Channel

is a multicarrier technique in which modulated data streams are divided into number of parallel substreams which occupies a very less bandwidth. However, full justice was done in proper utilization of bandwidth in OFDM where subcarriers overlap orthogonally. In this paper, the performance analysis of M-ary QAM-OFDM wireless communication systems affected by AWGN in terms of Symbol Error Rate is presented. The MATLAB script based model of the M-ary QAM-OFDM systems with normal AWGN channel is made for study of error performance. Lastly a comparative study of error performance of 64,128 and 256 QAM-OFDM system is made showing the effects of increase in value of M on SER.

Coherently wavelength injection-locking a 600-μm long cavity colorless laser diode for 16-QAM OFDM at 12 Gbit/s over 25-km SMF

The coherent injection-locking and directly modulation of a long-cavity colorless laser diode with 1% end-facet reflectance and weak-resonant longitudinal modes is employed as an universal optical transmitter to demonstrated for optical 16-QAM OFDM transmission at 12 Gbit/s over 25 km in a DWDM-PON system. The optimized bias current of 30 mA (~1.5Ith) with corresponding extinction ratio (ER) of 6 dB and the external injection power of -9 dBm is (are) required for such a wavelength-locked universal transmitter to carry the 16-QAM and 122-subcarrier formatted OFDM and data-stream. By increasing external injection-locking from -9 dBm to 0 dBm, the peak-to-peak chirp of the OFDM data stream reduces from 7.7 to 5.4 GHz. The side mode suppression ratio (SMSR) of up to 50 dB is achieved with wider detuning range between -0.5 nm to 2.0 nm under an injection power of 0 dBm. By modulating such a colorless laser diode with an OFDM data stream of 122 subcarriers at a central carrier frequency of 1.5625 GHz and a total bandwidth of 3 GHz, the transmission data rate of up to 12 Gbit/s in standard single-mode fiber over 25 km is demonstrated to achieve an error vector magnitude (EVM) of 5.435%. Such a universal colorless DWDM-PON transmitter can deliver the optical OFDM data-stream at 12 Gbit/s QAM-OFDM data after 25-km transmission with a receiving power sensitivity of -7 dBm at BER of 3.6 × 10(-7) when pre-amplifying the OFDM data by 5 dB.