【作者】 赵楠；

【导师】 权太范； 吴芝路；

【作者基本信息】 哈尔滨工业大学 ， 信息与通信工程， 2011， 博士

【摘要】 随着航天测控领域的迅猛发展,目前流行的统一载波测控系统已经不能满足我国航天事业的需求,因此一种新型的测控体制,统一扩频测控体制在统一载波测控体制的基础上发展起来,能够有效的克服统一载波测控系统中存在的缺点。尽管如此,统一扩频测控系统采用码分多址(Code Division Multiple Access,CDMA)或者多载波CDMA(Multi-carrier CDMA,MC-CDMA)通信体制,系统中存在若干类型的干扰,包括多址干扰、多径干扰、远近效应和CDMA体制与其它窄带通信体制之间的相互干扰等,这些干扰对统一扩频测控系统的性能以及系统容量影响很大,只有进行有效的抑制,才能充分发挥出统一扩频测控系统的优势。因此,本文重点研究了统一扩频测控系统中干扰去除的几种关键技术,包括多用户检测、功率控制和多符号检测等,进一步提高了系统的性能,以满足我国航天测控事业发展的需要。首先,无论对于CDMA体制还是MC-CDMA体制的统一扩频测控系统中的多用户检测技术,文中均采用了蚁群算法作为主要的研究手段,因此本文对蚁群算法进行了深入的研究。在介绍了几种经典的蚁群算法的基础上,提出了种群递减蚁群算法和变异蚁群算法,并对这两种方法进行了融合,提出了一种全新的种群递减变异蚁群算法。以旅行商问题为研究实例,仿真验证了文中提出的种群递减变异蚁群算法优良的性能,为后续章节种群递减变异蚁群算法多用户检测器的研究打下了基础。其次,对基于CDMA体制中的统一扩频测控系统中多用户检测技术进行了研究。CDMA体制可以分为同步CDMA体制和异步CDMA体制,分别应用于统一扩频测控系统的上行链路和下行链路中,因此CDMA体制的多用户检测技术也包括同步多用户检测和异步多用户检测。文中在分别介绍了同步和异步最优多用户检测器和几种次优线性多用户检测器的基础上,提出了种群递减变异蚁群算法同步多用户检测器和异步多用户检测器,尤其是在异步多用户检测器中,可以将多径干扰作为一个异步的用户进行检测并消除。分别针对同步CDMA体制和异步CDMA体制对种群递减变异蚁群算法多用户检测器进行性能仿真,仿真结果验证了其优良的性能,适合在统一扩频测控系统的上行和下行链路中使用,提高系统的性能。然后,研究了MC-CDMA体制统一扩频测控系统中多用户检测技术。MC-CDMA体制是将正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)和CDMA技术进行融合而提出来的,继承了这两种体制的优点,但是这两种体制的缺点仍然存在,也就是系统中存在着多址干扰和远近效应。文中在介绍了MC-CDMA体制最优多用户检测器和几种线性次优多用户检测器基础上,提出了用于MC-CDMA体制的种群递减变异蚁群算法多用户检测器。经过仿真证明,该检测器的性能优良,接近最优多用户检测,能够有效的消除多址干扰,抑制远近效应,使MC-CDMA体制统一扩频测控系统的检测性能明显提高。接下来,CDMA是个自扰系统,对远近效应非常敏感,因此研究了CDMA体制统一扩频测控系统中功率控制技术。文中给出了功率控制的系统模型并引出了预测器的相关理论,在分析了以用户为中心和以网络为中心的控制目标的基础上,提出了基于预测器的分布式多目标鲁棒功率控制算法。对本文提出的算法进行大量仿真,包括收敛速度、对抗衰落的鲁棒性能以及多目标控制性能分析等。通过仿真,验证预测器优良的鲁棒性能,并且证明了该算法可以适用于多种情况下不同的控制目标,能够有效的抑制CDMA体制统一扩频测控系统中存在的远近效应。最后,研究了PCM/FM体制的多符号检测技术。CDMA和MC-CDMA体制信号功率谱密度比较低,因此同一频段内也允许其他体制的信号同时进行通信,比如遥测领域常用的PCM/FM体制。虽然CDMA体制和MC-CDMA体制对PCM/FM信号来说可以看成背景噪声,但是这种干扰仍然会造成PCM/FM信号检测性能的下降。因此本文提出了一种易于硬件实现的基带正交复旋转多符号检测算法并进行了FPGA(Field Programmable Gate Array)实现。对该算法进行了仿真并在硬件平台上进行验证,结果表明,本文提出的算法能在Eb/N0大于5dB的情况下实现精确的位同步,并且比传统非相干鉴频算法的性能提高了3dB,能够有效解决统一扩频测控系统中异体制共通道情况下相互干扰的问题。更多还原

【Abstract】 With the rapid development in the space telemetry tracking and control (TT&C) field, the popular unified microwave TT&C system (UMTTCS) can not meet the requirements of the space industry in our country. Hence, a novel TT&C system, unified spread spectrum TT&C system (USSTTCS) has developed from the UMTTCS, and it can overcome the shortcomings of the UMTTCS effectively. However, some kinds of interferences exist in USSTTCS, such as multi-access interference, multipath interference, near-far effect, mutual interference between code division multiple access (CDMA) system and other narrow-band communication system and so on, because it applies CDMA or multicarrier CDMA (MC-CDMA) communication systems. These interferences affect the performance and system capacity of USSTTCS greatly, and the advantages of the USSTTCS will be made full use of only when the interferences are eliminated effectively. Therefore, several key techniques for eliminating the interferences in USSTTCS, such as multiuser detection, power control, and multi-symbol detection, have been studied in this dissertation to further improve the performance of the system and meet the requirements of the space TT&C industry in our country.Firstly, ant colony optimization (ACO) algorithm is used as the key technique to solve the multiuser detection problem in USSTTCS based on either CDMA of MC-CDMA system, hence the ACO algorithms are researched thoroughly in the dissertation. After introducing several traditional ACO algorithms, the population declining ACO algorithm and mutated ACO algorithm are proposed, and then a novel population declining mutated ant colony optimization (PDMACO) algorithm is proposed by combining these two algorithms together. The performance of PDMACO algorithm is evaluated through simulation using traveling salesman problem as simulation example, and it lays the foundation of the research in PDMACO multiuser detector in the following chapters.Secondly, the multiuser detection in the USSTTCS based on CDMA is researched. The CDMA system can be classified as synchronous CDMA system and asynchronous CDMA system, and they are used in the uplink and downlink of the USSTTCS respectively. Hence, the multiuser detection in CDMA system can also be classified as synchronous multiuser detection and asynchronous multiuser detection. The optimal multiuser detector and several linear suboptimal multiuser detectors are introduced, and then the PDMACO synchronous and asynchronous multiuser detectors are proposed. Especially in the asynchronous multiuser detector, the multipath interference can be seen as the signal of an asynchronous user to eliminate. The performance of the PDMACO synchronous and asynchronous multiuser detectors is simulated, and the results show that the PDMACO multiuser detector can achieve superior performance and it is suitable to be applied in the uplink and downlink of the USSTTCS respectively, and it can greatly improve the performance of the system.Thirdly, the multiuser detection in the USSTTCS based on MC-CDMA is researched. MC-CDMA system was proposed by combined orthogonal frequency division multiplexing (OFDM) and CDMA techniques, so it possesses the merits of these two systems and it also inherits the drawbacks of these two systems, which include multi-access interference and near-far effect. After introducing the optimal multiuser detector and several linear suboptimal multiuser detectors, the PDMACO multiuser detector for MC-CDMA is proposed in this dissertation. The simulation results show that the performance of the proposed detector is excellent and close to that of the optimal multiuser detector, and it can eliminate the multi-access interference and near-far effect effectively and improve the detection performance of the USSTTCS based on MC-CDMA greatly.Fourthly, CDMA system is a self-interfered system and it is very sensitive to the near-far effect, hence the power control technique in the USSTTCS based on CDMA is researched. The system model is introduced and the theory of estimator is given. Then the user-centric and network-centric control objectives are analyzed and the distributed multi-objective robust power control algorithm based onestimator is proposed in this dissertation. Plenty of simulations are taken about the speed of convergence, robust performance to the channel fading and multi-objective control analyzing. The simulation results show that the algorithm based on H_∞estimator is robust and it can adapt to different control objectives in several situations. The proposed algorithm can resist the near-far effect in the USSTTCS based on CDMA effectively.Lastly, the multi-symbol detection technique in PCM/FM system is researched. The power spectral density of CDMA and MC-CDMA signal is relatively low, hence other communication systems can exist in the same frequency band simultaneously, for example, the popular PCM/FM system in telemetry fields. Although the signal of CDMA or MC-CDMA system can be seen as background noise by PCM/FM system, the interference can decrease the performance of the PCM/FM detection. Therefore, a novel easily implemented baseband quadrature complex rotation multi-symbol detection (BQCR-MSD) algorithm is proposed and implemented on FPGA. Plenty of simulations are taken and it is also validated on the hardware platform, and the results show that the proposed algorithm can be accurately bit-synchronized when Eb/N0 is larger than 5dB, the detection performance of the conventional non-coherent frequency discriminator is improved 3dB by the proposed algorithm, and it can solve the mutual interference problem in the case of different systems and same channel in the USSTTCS effectively.更多还原