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简要介绍B3G系统需要支持高容量、高质量和高移动性的数据传输要求,而OFDM(orthogonal frequency division multiplexing,正交频分复用)技术由于非常适合于高速数据传输而成为B3G系统的热点候选传输技术。然而在高速移动环境中,OFDM系统的子载波间干扰是影响系统性能的主要因素,为了使OFDM技术更好地应用于B3G系统,对高速移动环境中OFDM系统的接收技术进行了研究,提出了一种基于EM算法的联合信道估计与检测技术的迭代接收方案。仿真结果表明,提出的接收机算法可以大大降低子载波干扰。 相似文献
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FuTURE B3G研究开发及关键技术进展 总被引:3,自引:0,他引:3
FuTURE计划系“十五”八六三计划面向Beyond 3G新一代移动通信研究开发的重大项目。文章在论述了Beyond 3G新一代移动通信系统基本需求及所面临的关键问题基础上,简要总结了FuTURE计划启动五年来在无线组网、小区划分与同频覆盖、多址与传输技术、多天线与自适应链路技术以及迭代接收技术等方面所取得的一系列被应用于现场实验系统的创新研究成果。 相似文献
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OFDM系统原理及仿真实现 总被引:2,自引:0,他引:2
OFDM是一种多载波调制方式。为建立一个完整的系统仿真模型,通常需要考虑其中的关键技术:调制方式、保护间隔以及信道模型的建立。论文在研究上述技术的基础上,建立了基于MATLAB的系统仿真模型,着重分析了OFDM系统在不同信道环境下的传输特性,对进一步深入研究OFDM技术具有一定的指导作用。 相似文献
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介绍B3G/4G中的关键技术--正交频分复用(OFDM)技术.OFDM技术是一种多载波调制技术,能有效地克服多径干扰和码间串扰.分析OFDM的原理、频谱特性和系统结构,并在TU信道下,利用Matlab仿真分析了Turbo信道编码在改善多径衰落时的影响,并得到在实际系统中选择最佳BCJR译码的迭代次数和Turbo编码的最佳编码速率等. 相似文献
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正交频分复用(OFDM)技术是下一代移动通信的核心技术之一。其最突出的优点是频谱利用率高和抗多径时延能力强,适合未来高速宽带无线通信的应用。OFDM技术通过将频率选择性多径衰落信道在频域内转换为平坦信道,减小了多径衰落的影响。根据OFDM基本原理特构建了一个OFDM通信系统仿真模型,分析了在不同调制方式、不同信道下信道编码对系统性能的影响。仿真结果表明,采用信道编码可有效的降低OFDM系统的误码率。 相似文献
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OFDM技术在Beyond3G中的应用 总被引:2,自引:0,他引:2
目前,继3G 之后的下一代移动通信系统“Beyond 3G ”或“4G ”的技术研究和标准建议工作正在紧张展开,预计下一代移动通信系统的速率可达到20M bit/s ,最高速率可达100M bit/s,国际电信联盟已经着手有关标准的制定工作。正交频分复用(O FD M )技术因其网络结构高度可扩展,具有良好的抗噪声性能和抗干扰能力以及频谱利用率高而被普遍认为是下一代移动通信系统必不可少的技术。 一、Beyond 3G 系统的特点[1,2] Beyond 3G 将是一种全IP 的网络结构(包括各种接入网与核心网),各种针对不同业务的接入系统连接到基于IP 的核心网中,形成… 相似文献
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Masahiro Kuroda Mariko Yoshida Ryoji Ono Shinsaku Kiyomoto Toshiaki Tanaka 《Wireless Personal Communications》2004,29(3-4):161-190
Secure cellular data services have become more popular in the Japanese market. These services are based on 2G/3G cellular networks and are expected to move into the next-generation wireless networks, called Beyond 3G. In the Beyond 3G, wireless communication available at a user's location is selected based on the type of the service. The user downloads an application from one wireless network and executes it on another. Beyond 3G expects core and wireless operators and allows to plug-in new wireless access. A security model that can accommodate these requirements needs to be sufficiently flexible for end users to utilize with ease. In this paper, we explain the Mobile Ethernet architecture for all IP networks in terms of the Beyond 3G. We discuss usage scenario/operator models and identify entities for the security model. We separate a mobile device into a personal identity card (PIC) containing cryptographic information and a wireless communications device that offers security and flexibility. We propose a self-delegation protocol for device authentication and use a delegated credential for unified network- and service-level authentication. We also propose proactive handover authentication using the security context between different types of wireless access, such as Third Generation Partnership Project (3GPP) and WLAN, so that the secure end-to-end communication channels established by service software on the TCP/IP are not terminated. Lastly, we raise security issues regarding the next-generation platform. 相似文献
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TD-SCDMA移动通信系统的增强和演进 总被引:2,自引:0,他引:2
时分-同步码分多址(TD-SCDMA)作为具有中国自主知识产权的第三代移动通信标准之一,即将全面商用化。TD-SCDMA未来的增强和演进是目前热点问题之一,各种方案不断提出,但还没有一个结合短期发展和长期发展的可持续发展计划。根据采用的关键核心技术不同,文章提出了TD-SCDMA增强和演进的4阶段论:第一阶段为当前的TD-SCDMA阶段;第二阶段是TD-SCDMA短期演进,即HSxPA阶段(包括HSDPA、HSUPA和HSPA演进);第三阶段是长期演进阶段;最后一阶段是基于TD-SCDMA的时分双工(TDD)超3G(B3G)或者第4代移动通信系统阶段。详细描述了演进过程中每个阶段的主要特点,以及多输入多输出(MIMO)、正交频分复用(OFDM)等新技术在演进过程的使用。 相似文献
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TIAN Qing-hua ZHANG Qi TAO Ying LIU Nai-jin XIN Xiang-jun ZHANG Li-jia XU Da-xiong 《中国邮电高校学报(英文版)》2013,20(3):37-42,77
Orthogonal frequency division multiplexing (OFDM) is attracting more attention for its capability of high speed transmission. However, the OFDM possesses an obvious shortage in its high ratio of the peak power to the average power (PAPR), which has become the main issue holding it back to be applied to the broadband satellite communication system. OFDM combined with time division multiplexing (TDM), dividing the subcarriers of OFDM into some blocks in time tune, can decrease the high PAPR of OFDM. Meanwhile, the advantages of OFDM can be preserved. In this paper, OFDM/TDM is applied to the broadband satellite communication system. This paper theoretically analyses OFDM/TDM system model as well as its restraining effect on PAPR, and proposes frequency domain multiplexing-pilot (FDM-Pilot) channel estimation algorithm. Simulation results show OFDM/TDM in broadband satellite communication system has approving performance and decreased the PAPR. 相似文献
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现有通信系统的调制技术限制了信号速率的进一步提高,即将推出的第四代(4G)移动通信系统需要更优良的调制技术。正交频分复用(OFDM)技术是很受欢迎的高速率无线通信技术,结合OFDM的调制技术将在4G系统中得到广泛应用。文中概要介绍了4G系统的特点及关键技术,然后系统介绍了OFDM多载波原理,最后重点介绍了多载波码分多址(MC-CDMA)和正交频分复用时分多址(OFDM-TDMA)两种多载波调制(MCM)技术。 相似文献
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Analysis and characterization of intercarrier and interblock interferences for wireless mobile OFDM systems 总被引:2,自引:0,他引:2
Hsiao-Chun Wu 《Broadcasting, IEEE Transactions on》2006,52(2):203-210
OFDM has been applied in a wide variety of wireless communications in recent years since it has the advantage over the conventional single-carrier modulation schemes when enduring the frequency-selective fading. However, intercarrier-interference (ICI) and interblock interference (IBI) due to the Doppler effect, carrier frequency drift of local oscillators and multipath fading limit the capability of OFDM systems. In this paper, a new generalized mathematical model for intercarrier and interblock interferences is derived for wireless mobile OFDM systems, in which Doppler frequency drift, local carrier frequency offset, multipath fading, and cyclic prefix coding are all present in reality. Such a new ICI/IBI model can be applied for OFDM performance evaluation in different environments. This new formulation of IBI and ICI provides a generalized framework which includes special ICI models appearing in the previous literature. Besides, the derived OFDM performance evaluation analysis in this paper can greatly benefit OFDM designers for wireless multimedia networks and digital video broadcasting technologies. 相似文献
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OFDM技术在4G中的应用 总被引:2,自引:0,他引:2
首先给出了正交频分复用(OFDM)技术的概念,详细叙述OFDM技术的基本原理和研究现状,阐述OFDM的关键技术及在4G中的应用,给出了4G的技术规范、技术要求和国内外对4G中关键技术的研究现状。分析表明OFDM技术在不增加带宽的情况下能提高系统容量,是4G移动通信技术中的核心技术。最后给出OFDM在今后的4G移动通信系统中的研究方向。 相似文献
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同步是OFDM系统中非常关键的问题。文章先分析了OFDM系统不同的同步技术,在此基础上讨论了OFDM的时频同步算法,最后指出了不同同步算法的应用。只要合理地选择适当的同步算法,就可以实现OFDM系统的同步。 相似文献
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Multiuser MIMO OFDM Based TDD/TDMA for Next Generation Wireless Communication Systems 总被引:1,自引:1,他引:0
Multiple-input multiple-output (MIMO) wireless technology in combination with orthogonal frequency division multiplexing (MIMO
OFDM) is an attractive air-interface solution for next-generation wireless local area networks (WLANs), wireless metropolitan
area networks (WMANs), and fourth-generation mobile cellular wireless systems. In this paper, one multiuser MIMO OFDM systems
with TDD/TDMA was proposed for next-generation wireless mobile communications, i.e., TDD/TDMA 4G, which can avoid or alleviate
the specific limitations of existing techniques designed for multiuser MIMO OFDM systems in broadband wireless mobile channel
scenarios, i.e., bad performance and extreme complexity of multiuser detectors for rank-deficient multiuser MIMO OFDM systems
with CDMA as access modes, extreme challenges of spatial MIMO channel estimators in rank-deficient MIMO OFDM systems, and
exponential growth complexity of optimal sub-carrier allocations for OFDMA-based MIMO OFDM systems. Furthermore, inspired
from the Steiner channel estimation method in multi-user CDMA uplink wireless channels, we proposed a new design scheme of
training sequence in time domain to conduct channel estimation. Training sequences of different transmit antennas can be simply
obtained by truncating the circular extension of one basic training sequence, and the pilot matrix assembled by these training
sequences is one circular matrix with good reversibility. A novel eigenmode transmission was also given in this paper, and
data symbols encoded by space–time codes can be steered to these eigenmodes similar to MIMO wireless communication systems
with single-carrier transmission. At the same time,, an improved water-filling scheme was also described for determining the
optimal transmit powers for orthogonal eigenmodes. The classical water-filling strategy is firstly adopted to determine the
optimal power allocation and correspondent bit numbers for every eigenmode, followed by a residual power reallocation to further
determine the additional bit numbers carried by every eigenmode. Compared with classical water-filling schemes, it can also
obtain larger throughputs via residual power allocation. At last, three typical implementation schemes of multiuser MIMO OFDM
with TDMA, CDMA and OFDMA, i.e., TDD/TDMA 4G, VSF-OFCDM and FuTURE B3G TDD, were tested by numerical simulations. Results
indicated that the proposed multiuser MIMO OFDM system schemes with TDD/TDMA, i.e., TDD/TDMA 4G, can achieve comparable system
performance and throughputs with low complexity and radio resource overhead to that of DoCoMo MIMO VSF-OFCDM and FuTURE B3G
TDD. 相似文献