Modulation Scheme For Transmission Research Articles

A Novel Range-Azimuth Joint Modulation Scheme for Range Ambiguity Suppression

Range ambiguity is a technical challenge for current spaceborne synthetic aperture radar (SAR) systems. To this end, a novel range-azimuth joint modulation transmission scheme is proposed, and the corresponding imaging processing and performance analysis are detailed. Compared with the azimuth phase coding (APC) technique, this scheme fully exploits the sampling margins of the range and azimuth dimensions, resulting in the range ambiguities experiencing a double suppression effect. Starting from the range-azimuth joint modulation scheme, to obtain the best ambiguity suppression performance, the design of a nonlinear frequency modulation (NLFM) waveform with a continuous piecewise linear instantaneous frequency is formulated and tackled via a MATLAB optimization toolbox. The detailed simulation results based on LuTan-1 (LT-1) parameters illustrate that the proposed methodologies outperform the APC method and provide considerable ambiguity suppression.

High-Rate Spatial Modulation Transmission Scheme With Block-Orthogonal Structure and Block-by-Block Sphere Decoding

The work in this paper is an extension of the recently proposed stacked Alamouti based spatial modulation (SA-SM) scheme. The motivation is that by taking advantage of the existing full-diversity full-rate (FDFR) space-time code, to construct SM transmission with the properties of higher spectral efficiency, non-vanishing determinants (NVD) property, as well as fast decoding. In the proposed scheme, we still use the stacked structure to construct the signal matrix, but Alamouti code in the SA-SM scheme is replaced by the FDFR Sezginer-Sari-Biglieri (SSB) code. The combination of stacked structure with SSB code can contribute to attaining the goals of our motivation. Since the proposed SM scheme has block-orthogonal (BO) property, we call it as BO-SM. We then present a low-complexity block-by-block sphere decoding for the BO-SM scheme owing to the variables corresponding to the same block are independent. Simulation results of bit error rate (BER) performance show that the proposed BO-SM scheme outperforms some newly presented diversity-achieving SM schemes.

HCM Successive Transmission Scheme With Banded MMSE Equalization Based on Fast Convolution Over Doubly-Selective Fading Channels

A novel hybrid carrier modulation (HCM) successive transmission scheme with banded minimum mean square error (MMSE) equalization based on fast convolution (FC) is proposed and analyzed. The proposed scheme not only further suppresses the residual interference of banded MMSE equalization by the overlap-save operation of FC, but improves the spectral efficiency by removing the cyclic prefix. Additionally, the proposed HCM scheme with particular orders outperforms the single carrier modulation and the multicarrier modulation transmission scheme. Theoretical analysis and numerical simulations are presented to demonstrate the superiority of the proposed scheme at a moderate complexity over doubly-selective fading channels.

Low-Complexity Spatial Modulation for IM/DD Optical Wireless Communications

A bipolar pulse amplitude modulation (PAM)-based optical spatial modulation transmission scheme is developed for intensity modulation/direct detection optical wireless communications. In the proposed scheme, multiple light emitting diodes (LEDs) and multiple photodiodes are employed at the transmitter and receiver, respectively. The transmit LEDs are divided into two groups. The first group of LEDs transmits the positive part of the PAM symbol, while the second group of LEDs transmits the absolute value of the negative part of the bipolar PAM symbol. Besides, spatial shift keying is employed in the active LED group to improve data rate. According to the transmit strategy, a novel low-complexity receiver algorithm is developed.

Performance of Multiple Rank Modulation Based on SM-MIMO

Abstract A multiple rank modulation (MRM) scheme is proposed that provides better error performance, enhances the data rate and reduces the system demodulation complexity. Multiple input multiple output (MIMO) scheme is a technique that uses several antennas at the transmitter and receiver to minimize error and optimize data speed. MRM is a novel technique that borrows from spatial modulation-MIMO (SM-MIMO) scheme. The basic idea of this scheme involves the transmitter receiving a group of bits and subdividing them into two blocks; rank index block and signal modulation block. The rank index bit block is used to select the rank to be activated and the rank selected contains at least one active transmit antenna (TA). The signal modulation bit block is encoded in a given modulation scheme for transmission. It is then transmitted through the activated rank that contains at least one active TA. The transmitted encoded signal modulation bit block is received through the receive antenna and a receiver. The receiver estimates a rank index and the transmitted symbol from the signal received. The signal modulation bit block is finally decoded. This paper addresses the performance of MRM scheme based on error performance to run cellular fifth generation (5G). We perform and present simulation results of MIMO systems employing MRM scheme to generate bit error rate (BER) of this system.

Stacked Alamouti Based Spatial Modulation

In this paper, a high-rate and diversity-achieving spatial modulation transmission scheme is proposed, which uses the stacked Alamouti code as the transmitted signal matrix and then is named as stacked Alamouti based spatial modulation (SA-SM) scheme. In this scheme, the spatial constellation (SC) is composed of all the possible activated antennas combinations. According to a specific SC codeword, the corresponding symbols in the stacked Alamouti code are simultaneously activated. Owing to the structure of stacked Alamouti code, the SA-SM scheme can work with arbitrary even number of transmit antennas $n_{T}$ , and any number of activated antennas from 1 to $n_{T}$ . With the same number of activated antennas $n_{A}$ , the SA-SM scheme carries more symbols than the spatially modulated orthogonal space-time block codes (SM-OSTBC) scheme, thus SA-SM can achieve higher spectral efficiency. Without the need of any parameter or matrix optimization, the SA-SM scheme enjoys the non-vanishing determinants property. Moreover, owing to possessing the block-orthogonal structure, SA-SM enables faster metric computations in the QR decomposition-M detection, and then it achieves significant decoding complexity reduction without performance loss. Under various system configurations, the performance advantages of SA-SM over several existing diversity-achieving SM schemes such as GSTSK and SM-OSTBC, are shown by simulation results for various spectral efficiencies.

Spectral Analysis of Fractionally-Spaced MMSE Equalizers and Stability of the LMS Algorithm

In the communication systems that use a linear modulation scheme for transmission, the fractionally-spaced (FS) samples of the received signal constitute a wide-sense cyclostationary time series. Hence, the standard Fourier transform techniques cannot be used to study the spectral characteristics of the received FS samples or to derive the transfer function (TF) of the corresponding digital minimum mean-square error (MMSE) receiver. In this paper, an analytical expression for the TF of the FS MMSE equalizer is derived, which includes the effects of the continuous-time to discrete-time (C/D) converter used at the receiver front end. Using this TF, the sources of instability of the FS least-mean-square (LMS) algorithm and the effects of the equalizer length and sampling phase on convergence of the LMS algorithm are explained. For stabilization of the FS LMS algorithm, conditions on the front-end C/D converter are provided, such that, when satisfied the LMS algorithm becomes more stable and the learning characteristics of the modified receiver are better than the leaky-FS LMS algorithm. Theoretical results are corroborated by simulations.

Double sideband suppressed carrier modulation for stable fiber delivery of radio frequency standards

We theoretically and experimentally investigate the properties of a double sideband suppressed carrier modulation transmission scheme for long distance microwave frequency standard dissemination. The proposed method effectively doubles the transmitted frequency obtaining enhanced phase noise and stability performance. Suppressing the optical carrier also eliminates the dispersion induced signal fading. Important transmission parameters like optical modulation depth and linearity are also improved. Allan deviation and phase noise measurements prove the superior performance of the proposed modulation format.

Out-of-band and adjacent-channel interference reduction by analog nonlinear filters

In a perfect world, we would have ‘brick wall’ filters, no-distortion amplifiers and mixers, and well-coordinated spectrum operations. The real world, however, is prone to various types of unintentional and intentional interference of technogenic (man-made) origin that can disrupt critical communication systems. In this paper, we introduce a methodology for mitigating technogenic interference in communication channels by analog nonlinear filters, with an emphasis on the mitigation of out-of-band and adjacent-channel interference. Interference induced in a communications receiver by external transmitters can be viewed as wide-band non-Gaussian noise affecting a narrower-band signal of interest. This noise may contain a strong component within the receiver passband, which may dominate over the thermal noise. While the total wide-band interference seen by the receiver may or may not be impulsive, we demonstrate that the interfering component due to power emitted by the transmitter into the receiver channel is likely to appear impulsive under a wide range of conditions. We give an example of mechanisms of impulsive interference in digital communication systems resulting from the nonsmooth nature of any physically realizable modulation scheme for transmission of a digital (discontinuous) message. We show that impulsive interference can be effectively mitigated by nonlinear differential limiters (NDLs). An NDL can be configured to behave linearly when the input signal does not contain outliers. When outliers are encountered, the nonlinear response of the NDL limits the magnitude of the respective outliers in the output signal. The signal quality is improved in excess of that achievable by the respective linear filter, increasing the capacity of a communications channel. The behavior of an NDL, and its degree of nonlinearity, is controlled by a single parameter in a manner that enables significantly better overall suppression of the noise-containing impulsive components compared to the respective linear filter. Adaptive configurations of NDLs are similarly controlled by a single parameter and are suitable for improving quality of nonstationary signals under time-varying noise conditions. NDLs are designed to be fully compatible with existing linear devices and systems and to be used as an enhancement, or as a low-cost alternative, to the state-of-art interference mitigation methods.

대용량 데이터 전송을 위한 프리코더가 적용된 공간 변조기법

대용량 데이터 전송을 위한 프리코더가 적용된 공간 변조기법

Performance analysis of two‐way opportunistic decode‐and‐forward based systems in Nakagami‐ m fading environments

This paper studies the performance of a two-way relay-based communication system with opportunistic relay selection in Nakagami-m fading environments. The authors consider a two-way wireless communication system where two nodes, acting as sources and using different modulation schemes for transmission, are unable to exchange data because of deep fading on their direct link and proceed via L relay terminals. They provide closed-form expression for the probability density function of the link between the ‘selected’ best relay and each source, and use this result to derive a closed-form expression for the average symbol error probability which, to the best knowledge of the authors, has never been done before. This result is further approximated for the high signal-to-noise ratio regions and used to develop closed-form expressions for the optimised power allocated to each node involved in the communication process. The authors asset their formulae with numerical results and interpretations to complete this work.

A sensitivity matched multicarrier modulation

We develop a multicarrier modulation scheme for transmission of compressed data. The energy allocation among subcarriers is optimized by minimizing a modified symbol error function in either AWGN or Rayleigh fading channels. It is observed that our sensitivity matched multicarrier modulation significantly outperforms the conventional multi carrier modulation. The performance gain in Rayleigh fading channels varies from 0.58 to 3.26 dB depending upon the relative sensitivity of bit groups associated with subchannels.

Multiuser soft interference canceler via iterative decoding for DSL applications

This paper presents a method to mitigate interference on a transmission system by another system with an overlapping frequency band. The systems are uncoordinated so that they cannot be made to transmit in orthogonal coding space. The transmission environment is an interference channel rather than the multiaccess channel often considered in other multiuser detection problems, for instance at the base station of a code division multiple access wireless system. Using the fact that the inputs are all from discrete constellations, it is possible to use a multiuser maximum-likelihood (ML) detector to decode the signals from the system of interest with low probability of error. However, the ML detector often requires impractical computation. A soft linear canceler is instead used to reduce the interference with a small loss of bandwidth in the system of interest. The method has a much lower complexity than a full-blown ML detector, and the soft canceler performance is close to an ML detector. The method is demonstrated on a very-high-speed digital subscriber lines system with a home local area network interference. The system of interest is using a multicarrier modulation transmission scheme such as discrete multitone, while the interfering system transmits using quadrature amplitude modulation.