分布式中继系统中信号处理关键技术研究

发布时间：2018-06-19 07:39

本文选题：分布式数字中继 + 底噪声抑制　；参考：《东南大学》2017年硕士论文

【摘要】：3GPPLTE-A中提出中继技术来扩展小区覆盖面积,将信号提供给那些阴影衰弱严重或者信号很难到达的地方,为室内以及业务密集的地方提供覆盖。中继技术能够扩大网络覆盖面积、提高系统容量、增强系统抗衰落性能、增强系统的鲁棒性,而且在高速发展的通信方式下,能够降低成本,以更节约资源的方式进行网络布局建设。中继的种类有很多,其中分布式数字中继采用一个近端单元带多个远端单元的组网方式,近端单元和远端单元之间用光纤或电缆连接,与传统的模拟中继相比具有远距离传输衰减小、性能稳定、组网方式灵活、监控功能完善、信号处理方便、通用性和兼容性强等优点,因而被广泛研究和运用。然而,分布式数字中继的运用会使得基站上行底噪声抬高,从而降低基站灵敏度,本文即研究如何通过数字信号处理的方式解决该问题。首先,本文基于分布式数字中继系统的工作原理,对一个近端单元带多个远端单元的组网方式下系统的上行底噪声做了详细的分析。通过推导分析得出,分布式数字中继系统中上行底噪声增量在工程中主要是由远端单元的自身噪声系数、上行增益和远端单元的配置数目决定。接着本文在LTE系统中,基于3GPP case1下路径损耗模型分别对传统模拟中继和分布式数字中继场景进行了上行链路仿真计算,仿真结果表明分布式数字中继较传统模拟中继链路增益效果要好,然而随着远端单元的配置数目增多时,系统底噪声将明显增加,从而影响系统性能。为此,本文基于GSM系统和LTE系统,分别提出了相应的抑制上行底噪声的方案设计。其基本原理是将接收到的上行信号经过滤波处理,得到各用户频段的数字基带信号,再对滤波后的数字基带信号进行功率检测,将检测的功率值与设定好的噪声门限做比较判决,按照一定的判断规则,若信号功率足够小,则将其判定为干扰噪声,直接置零,达到消除干扰底噪声的目的。其次,本文针对提出的GSM系统和LTE系统中分布式数字中继上行噪声抑制方案进行了详细的设计与仿真。先是介绍了 GSM系统和LTE系统上行链路信号传输的基础概念,基于MATLAB工具产生GSM和LTE上行链路信号;接着对底噪声抑制模块中的数字滤波器组、功率检测、门限设置与判别模块分别逐一做了详细的阐述和设计,并对各个模块的性能进行了仿真与分析。最终,将上述设计分别应用到GSM和LTE分布式数字中继系统中,通过仿真不同信噪比下系统的误比特率,比较了采用该底噪声抑制方案前后系统的性能,仿真结果表明采用该底噪声抑制方案后系统的上行噪声得到了很好的抑制,误比特率有了很好的改善。最后,本文针对LTE系统底噪声抑制模块进行了优化与性能分析。先是针对噪声门限的设置,采用设置噪声开启门限和噪声关闭门限两个噪声门限的方法,并且提出了自适应噪声门限的方法,使得噪声门限的值可以随着实时噪声功率大小的变化而变化,从而使得噪声判决更加准确,减少了截断和误判误差,通过误比特率仿真可以看出噪声门限优化后噪声抑制模块可以更准确的抑制干扰噪声,系统误比特率得到了进一步改善。接着本文针对底噪声抑制模块中的滤波器组进行了优化,对DFT滤波器组中的原型滤波器进行了重新设计,以减小滤波器组各滤波器之间的重叠,使得滤波效果更好。本文还针对底噪声抑制模块的性能进行了评估分析,分析了各模块的延迟对系统带来的影响,并给出了削弱影响的办法;并对滤波器组计算复杂度进行了分析,提出了采用每多个相邻的资源块作为一个滤波单元的方法来减少滤波器的阶数,使得滤波器组中计算量减少。
[Abstract]:In 3GPPLTE-A, relay technology is proposed to extend the area of cell coverage, providing the signal to places where the shadow is weak or the signal is difficult to reach. It provides coverage for indoor and business intensive places. Relay technology can expand network coverage, improve system capacity, enhance system anti fading performance, and enhance system robustness. In the rapid development of communication mode, the cost can be reduced and the network layout is built in the way of saving resources. There are many kinds of relay. In which the distributed digital relay uses a network mode with a near terminal unit with many remote units, the near end unit and the remote unit are connected by optical fiber or cable, and the traditional mode. The proposed relay is widely studied and applied in comparison with the low attenuation of long distance transmission, stable performance, flexible networking mode, perfect monitoring function, convenient signal processing, versatility and compatibility. However, the application of distributed digital relay will make the base station bottom noise raise and reduce the sensitivity of base station. This paper is to study How to solve this problem by means of digital signal processing. First, based on the working principle of distributed digital relay system, this paper makes a detailed analysis of the upper bottom noise of the system under the networking mode of a near terminal unit with multiple remote units. Through the derivation and analysis, the uplink noise increment in the distributed digital relay system is obtained. In the project, it is mainly determined by the self noise coefficient of the remote unit, the uplink gain and the configuration number of the remote unit. Then, in the LTE system, the uplink simulation of the traditional analog relay and distributed digital relay scene is calculated on the basis of the path loss model under the 3GPP case1, and the simulation results show that the distributed number is in the distributed number. The result is better than the traditional analog relay link. However, with the increase of the configuration number of the remote unit, the noise of the system bottom will be significantly increased, thus affecting the performance of the system. Therefore, based on the GSM system and the LTE system, the corresponding scheme to suppress the uplink noise is proposed. The basic principle is to receive the uplink letter. After filtering, the digital baseband signal of each user frequency band is obtained, and then the power of the digital baseband signal after filtering is detected. The power value of the detection is compared with the set noise threshold. In accordance with certain judgment rules, if the signal power is small enough, it is judged as interference noise and directly zero, so as to eliminate interference. The purpose of bottom noise. Secondly, in this paper, the distributed digital relay uplink noise suppression scheme in GSM and LTE systems is designed and simulated in detail. First, the basic concept of GSM system and LTE system uplink signal transmission is introduced, GSM and LTE uplink signals are generated based on MATLAB tools; and then bottom noise is used. The digital filter bank of the suppression module, the power detection, the threshold setting and the discriminant module are elaborated and designed in detail, and the performance of each module is simulated and analyzed. Finally, the above design is applied to the GSM and LTE distributed digital relay system, by simulating the bit error of the system under the different signal to noise ratio. The performance of the system with the background noise suppression scheme is compared. The simulation results show that the uplink noise of the system is well suppressed after the noise suppression scheme, and the bit error rate has been improved well. Finally, the optimization and performance analysis of the LTE system base noise suppression module are carried out. The method of setting the threshold of noise opening and closing the threshold of noise to close the threshold of two noise threshold is adopted, and a method of adaptive noise threshold is proposed, which makes the value of the noise threshold change with the change of the real time noise power, thus making the noise decision more accurate, reducing the truncation and misjudgment error and by mistake ratio. The special rate simulation shows that the noise suppression module can more accurately suppress the interference noise after the noise threshold optimization, and the system bit error rate has been further improved. Then this paper optimizes the filter banks in the bottom noise suppression module, and redesigns the prototype filter in the DFT filter bank to reduce the filter banks. The overlapping of each filter makes the filtering effect better. In this paper, the performance of the bottom noise suppression module is evaluated and analyzed, the effect of the delay on the system is analyzed, and the method to weaken the influence is given. The complexity of the filter group is analyzed and the use of each adjacent resource block is proposed. As a filter unit, the order of the filter is reduced, and the computation amount in the filter bank is reduced.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.5

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