Interference in Complex CDMA-OFDM/OQAM for Better Performance at Low SNR

This article is about orthogonal frequency-division multiplexing with quadrature amplitude modulation combined with code division multiplexing access for complex data transmission. It aims to present a method which uses two interfering subsets in order to improve the performance of the transmission scheme. The idea is to spread in a coherent manner some data amongst two different codes belonging to the two different subsets involved in complex orthogonal frequency-division multiplexing with quadrature amplitude modulation and code division multiplexing access. This will improve the useful signal level at the receiving side and therefore improve the decoding process especially at low signal to noise ratio. However, this procedure implies some interference with other codes therefore creating a certain noise which is noticeable at high signal to noise ratio.

Performance Analysis of Parallel Interference Cancella tion for Multi-carrier DS-CDMA

The parallel interference c an cellation for multi-carrier DS-CDMA (which is termed FDC-PIC) is proposed by integrating frequency diversity combination. The simulations are made over FDC- PIC with respect to different decision ways——hard, soft and linear decisions, respectively, and we conclude that FDC-PIC acquires superior performance improv ement over correlation reception of multi-carrier DS CDMA. With an increase in interference cancellation stages, the system performance is improved further. Th e initial 2 stages bring about the most dominant performance improvement, but up to the 3rd stage the system performance is improved little. It is also shown by the simulation results that FDC-PIC with soft decision would exhibit the best performance with a high implementation complexity, while FDC-PIC with linear de cision acquires performance comparable to that of FDC-PIC with soft decision wi th a reduced-complexity if the number of the interference cancellation stages i s the same, which indicates that FDC-PIC with linear decision has optimal perfo rmance/complexity tradeoff and therefore will be suitable for practical applica tion in future.

解决CDMA同步问题的可见光定位算法

为克服时分复用技术中需要时钟同步和频分复用系统不够灵活的问题,提出了一种基于码分复用技术的高精度可见光定位算法。算法在异步场景下实现了码元同步和可见光定位的过程,仿真结果表明,在覆盖房间80%以上的区域时,算法的平均定位误差为6.9cm,最大定位误差为11cm,适用于绝大多数室内基于位置信息的服务。此外,分析了系统定位精度与接收机视场角及接收机离地高度的关系。发现在一定范围内,接收机视场角越大,系统的定位性能越差;接收机的离地高度越大,系统的定位性能越好。

Detection optimization for resonance region radar with dense multi-carrier waveform

Unlike the existing resonance region radar systems （RRRS ） that transmit the orthogonal frequency division multiplexing （OFDM）multi-carrier waveform,the dense multi-carrier （DMC）radar waveform which has a narrower frequency interval than the traditional OFDM waveform is proposed.Therefore,in the same frequency bandwidth,the DMC waveform contains more sub-carriers and provides more frequency diversity.Additionally,to further improve detection performance,a novel optimal weight accumulation target detection （OWATD）method is proposed,where the echo electromagnetic waves at different frequencies are accumulated with the optimal weight coefficients.Then,with the signal-to-noise ratio （SNR）of echo waveform approaching infinity,the asymptotic detection performance is analyzed, and the condition that the OWATD method with the DMC outperforms the matched filter with the OFDM is presented.Simulation results show that the DMC outperforms the OFDM in the target detection performance,and the OWATD method can further improve the detection performance of the traditional methods with both the OFDM and DMC radar waveform.

A SCHEME OF M-ARY MULTI-CARRIER SPREAD SPECTRUM BASED ON WAVELET PACKET

A novel scheme of M-ary multi-carrier spread spectrum based on wavelet packet is proposed. Its performance is investigated for a multipath, slow Rayteigh fading channel. The performance advantages of the system over that based on DFT are demonstrated by both analytical and simulation methods.

Modeling and optimization of a multi-carrier renewable energy system for zero-energy consumption buildings

For the carbon-neutral,a multi-carrier renewable energy system(MRES),driven by the wind,solar and geothermal,was considered as an effective solution to mitigate CO2emissions and reduce energy usage in the building sector.A proper sizing method was essential for achieving the desired 100%renewable energy system of resources.This paper presented a bi-objective optimization formulation for sizing the MRES using a constrained genetic algorithm(GA)coupled with the loss of power supply probability(LPSP)method to achieve the minimal cost of the system and the reliability of the system to the load real time requirement.An optimization App has been developed in MATLAB environment to offer a user-friendly interface and output the optimized design parameters when given the load demand.A case study of a swimming pool building was used to demonstrate the process of the proposed design method.Compared to the conventional distributed energy system,the MRES is feasible with a lower annual total cost(ATC).Additionally,the ATC decreases as the power supply reliability of the renewable system decreases.There is a decrease of 24%of the annual total cost when the power supply probability is equal to 8%compared to the baseline case with 0%power supply probability.

CQI Feedback Compression Method for Multi-Carrier MIMO Transmission

In multi-user wireless communication systems,adaptive modulation and scheduling are promising techniques for increasing system throughput.However,for multi-carrier systems,they will lead to overwhelming user feedback overhead for Channel Quality Indication(CQI) in every subcarrier.In our work,novel CQI feedback schemes are proposed based on the recently proposed theory of Compressive Sensing(CS).First,the standard CS method is introduced to reduce CQI feedback overhead for multi-carrier Multiple-Input Multiple-Output transmission.In addition,via further research on the design of measurement matrix with standard CS,a novel CQI feedback scheme based on subspace CS is proposed by exploiting the subspace information of the underlying signal and the feedback rate is greatly decreased.Simulation results show that,with the same feedback rate,the throughputs with subspace CS outperform the Discrete Cosine Transform(DCT)-based method which is usually employed,and the throughputs with standard CS outperform DCT when the feedback rate is larger than 0.13 bits/subcarrier.

Multi-carrier transport in ZrTe_5 film

Single-layered zirconium pentatelluride （ZrTes） has been predicted to be a large-gap two-dimensional （2D） topolog- ical insulator, which has attracted particular attention in topological phase transitions and potential device applications. Herein, we investigated the transport properties in ZrTe5 films as a function of thickness, ranging from a few nm to several hundred nm. We determined that the temperature of the resistivity anomaly peak （Tp） tends to increase as the thickness decreases. Moreover, at a critical thickness of ~ 40 rim, the dominating carriers in the films change from n-type to p-type. A comprehensive investigation of Shubnikov-de Hass （SdH） oscillations and Hall resistance at variable temperatures revealed a multi-carrier transport tendency in the thin films. We determined the carrier densities and mobilities of two majority car- riers using the simplified two-carrier model. The electron carriers can be attributed to the Dirac band with a non-trivial Berry phase ~, while the hole carriers may originate from surface chemical reaction or unintentional doping during the microfabrication process. It is necessary to encapsulate the ZrTe5 film in an inert or vacuum environment to potentially achieve a substantial improvement in device quality.

Recognition of multi-carrier OFDM and single-carrier with alpha-stable distribution noise

In order to identify the multi-carrier orthogonal frequency division multiplexing(OFDM) and the single-carrier signal in the non-Gaussian noise environment, different features of the two signals are analyzed in terms of five parameters: generalized normalized fourth-order cumulant, the maximum value of the instantaneous amplitude power spectral density, absolute standard deviation of instantaneous phase on the section with weak signals, and position and numbers of the generalized cyclic spectrum's peak. The recognition method of the multi-carrier OFDM and single-carrier signal is proposed in the environment with alpha-stable distribution noise. Simulation results show that the recognition rate of the multi-carrier OFDM can reach 100% when the mixed signal to noise ratio(MSNR) is greater than-5 dB and the recognition rate can reach 90% for the single-carrier when the MSNR is greater than 2 dB.

ICI elimination of M-band wavelet multi-carrier modulation system

To solve the inter carrier interference （ICI） elimination problem of an M-band wavelet multi-carrier modulation system, this paper analyzes the principle of the ICI caused by the Doppler frequency shift and its mathematical expression based on the M-band wavelet multi-carrier modulation system model. Through the analysis of the mathematical expression and combining with the perfect reconstruction conditions of the filter banks, we propose the design conditions of an M-band filter to reduce and eliminate the ICI. The impulse response model of the filter design conditions and an iterative algorithm is also established. The simulation results show that the proposed ICI reduction and elimination methods can effectively improve the system performance.

On the Characteristic of Orthogonality for Multi-Carrier-Based Systems

The dominate factors caused by reasons of losing the orthogonality in fading channel including FBC (fading branch correlation), CFO (carrier frequency offset), and even the CPN (carrier phase noise) are novel discussion in this letter. The first one factor causes the ISI (inter-symbol interference), and, however, the latter two will lead to the phenomenon of CPE (common phase error) and ICI (inter-carrier interference). On the other hand, they will lead to the loss of orthogonality for the radio system with multi-carrier modulating schemes, i.e., both them mainly deteriorate a wireless communication system. Eventually, in this letter not only the analytical expressions are derived, but a three dimension numerical results from the analysis involve the three parameters also illustrated is.

Enhancing Wind Power Integration through Optimal Use of Flexibility in Multi-Carrier Energy Systems from the Danish Perspective

Denmark’ goal of being independent of fossil energy sources in 2050 puts forward great demands on all energy subsystems (electricity, heat, gas and transport, etc.) to be operated in a holistic manner. The Danish experience and challenges of wind power integration and the development of district heating systems are summarized in this paper. How to optimally use the cross-sectoral flexibility by intelligent control (model predictive control-based) of the key coupling components in an integrated heat and power system including electrical heat pumps in the demand side, and thermal storage applications in buildings is investigated.

多径异步LSC-DS-CDMA信号伪码估计

针对多径环境下异步长短码直扩码分多址信号(long and short code direct sequence code division multiple access,LSC-DS-CDMA)伪码估计难的问题,提出一种基于张量分解和联合估计的伪码估计方法,采用重叠窗对接收信号进行分段并构建张量模型。为改善传统线性步长搜索算法结合梯度下降的方法分解因子矩阵收敛较慢的问题,提出改进的线性步长搜索算法,结合使用动量梯度下降法对各子张量进行Tucker分解得到各因子矩阵,所需的迭代次数大大减少;利用接收增益矩阵和移位相乘解决复合码的排序模糊和幅度模糊问题;利用最大似然准则联合估计复合码和多径信道后,使用梅西算法和相关运算估计每个用户的长码和短码。仿真结果表明,该方法能够有效估计多径异步LSC-DS-CDMA信号的伪码。

基于CDMA网络的时间校准系统方案设计

针对大型场所不同房间内时钟显示不统一的问题,本文设计了一种基于CDMA网络的时间校准系统方案,其具有成本低、精度高、无累计误差等特点,具有较强的实用价值。

解决CDMA同步问题的可见光定位算法

为克服时分复用技术中需要时钟同步和频分复用系统不够灵活的问题,提出了一种基于码分复用技术的高精度可见光定位算法。算法在异步场景下实现了码元同步和可见光定位的过程,仿真结果表明,在覆盖房间80%以上的区域时,算法的平均定位误差为6.9cm,最大定位误差为11cm,适用于绝大多数室内基于位置信息的服务。此外,分析了系统定位精度与接收机视场角及接收机离地高度的关系,在一定范围内,接收机视场角越大,系统的定位性能越差;接收机的离地高度越大,系统的定位性能越好。

工程教育背景下MATLAB在通信原理教学中应用

在工程教育专业认证的背景下,为有效开展通信原理课程的综合实践,提升教学效果,将MATLAB设计引入教学活动中。以工程教育理念为指导,改进传统实践教学不足。以CDMA设计为案列,介绍新思路下教学设计与实施过程,注重培养学生解决复杂工程问题能力,构建多方面综合教学考核评价体系,激励学习主观能动性。实验结果表明,该方法有效可行,满足工程教育专业认证人才培养需求。

CDMA装配技术在制冷主机房机电安装中的运用

制冷机房是一种机电工程,涉及到大量的材料与设备。这些材料和设备安装在一起会给主机房的安装造成很多困难。本文分析了制冷主机房的结构特点,在此基础上提出了一种 CDMA 装配技术,这种方法不仅可以将电气与电子工程施工中大量用到的直平法,预埋法,套筒法等方法与 CDMA 技术结合起来,而且可以保证各专业施工不交叉、不矛盾。最后通过案例验证了该方法的可行性。

正交通道中码分干扰对载波捕获的影响分析及研究

在多功能数字基带的信号处理过程中,由于正交通道的码分干扰较大,传统的FFT算法无法进行载波捕获。文中从理论上分析了正交通道中扩频码对FFT算法的影响,并进行了仿真分析,最后提出双向搜索捕获算法和增加平方算法两种方法在消除码分干扰中的应用。双向搜索捕获算法在完成码捕获的同时能获得多普勒频率;增加平方算法能有效消除码分多址的影响,精确计算多普勒频率,简单实用。实验结果表明,两种消除码分干扰的算法各有优点,在实际工程应用中可根据需要选择使用。

不相关多子集零相关区序列集的构造

在多小区环境下的准同步码分多址(quasi-synchronous code-division multiple-access,QS-CDMA)系统中,不相关多子集零相关区(zero correlation zone,ZCZ)序列集不仅可以消除一定时延内来自相同小区的信号干扰,而且可以完全消除来自相邻小区的信号干扰。针对如何基于仿酉矩阵构造多子集ZCZ序列集的问题,设计了两种构造方法。具体地,通过构造具有一定特性的多个初始矩阵,再结合仿酉矩阵,进而利用不同的初始矩阵产生不同的ZCZ序列集,且序列集间互不相关。所提方法的核心是多个初始矩阵的设计,方法1通过对离散傅里叶变换(discrete Fourier transform,DFT)矩阵进行分块与叠加实现,方法2利用已有的不相关多子集ZCZ序列集实现。由两种方法得到的构造结果,其参数趋近于最优,为解决多小区环境下的干扰抑制问题提供了新的序列设计方法。

WPDM-CDMA系统中的LS与MMSE信道估计算法仿真分析

针对无线衰落信道工作下的WPDM-CDMA(小波包变换多载波码分多址)系统特点建立系统仿真模型。探讨在WPDM-CDMA系统中的信道估计问题。分析了2种常见信道估计方法:最小平方误差(LS)和最小均方误差(MMSE)信道估计算法。在Matlab环境下编写相关信道估计算法程序,通过仿真分析比较两种算法的均方差和误码率。结果表明:性能上MMSE算法远优于LS算法,但MMSE算法的运算量比LS算法大很多。