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本文考虑了单载波频域预处理技术作为多用户大规模MIMO下行链路通信的传输方案。首先,根据系统模型推导出宽带多用户大规模MIMO下行链路预编码的形式,其中包括匹配滤波(MF)和迫零(ZF)预编码方案。随后,通过理论推导和仿真验证得到两种预编码方案下OFDM与SC-FDP的用户和速率表达式,结果显示SC-FDP在大规模MIMO场景下拥有与OFDM相似的用户和速率。然后,通过仿真实验对比OFDM与SC-FDP的峰均比(PAPR),结果表明在用户数目较少的情况下,SC-FDP相对于OFDM具有更小的PAPR,随着用户数增加,两者之间差异逐渐减小。最后,对多用户MIMO下行链路中OFDM与SC-FDP的运算复杂度进行比较,二者系统复杂度相当,而SC-FDP主要运算任务在基站端完成。基于以上比较分析,SC-FDP在宽带多用户大规模MIMO下行链路中是一种很有潜力的传输方案。 相似文献
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本文根据MB-OFDM-UWB系统的特点,提出了将OFDM技术和MSFH(多级跳频)技术结合的全部载波多址接入方案.该多址方案有二级构成,其中前一级使用OFDM,设计时参考了Multi-band OFDM Physical Proposal for IEEE 802.15 TaskGroup3a中的物理层建议,后一级采用跳频模块,并将基于余数域的多级跳频图案应用到该多址方案中,不仅大大减小了多用户碰撞的概率,而且有利于超宽带信号的生成.理论分析和仿真结果表明,基于OFDM和多级跳频结构的全部载波多址接入方案在系统容量、误比特率性能、抗干扰等方面具有诸多的优势.在8用户情况下,当系统误比特率为10~(-2)时,基于该结构的全载波方案比TH-PPM多址方案改善信噪比5dB左右. 相似文献
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基于Jake信道模型的单载波与OFDM系统性能比较 总被引:2,自引:1,他引:1
在介绍正交频分复用(OFDM)系统与单载波频域均衡系统原理基础上,针对第四代移动通信系统中无线传输中由时变多径时延扩展和Doppler频移所引起的符号问干扰ISI,在上行链路中采用单载波调制及频域均衡。依据IEEE WorkingGmup802.20的草案及根据改进的Jake信道模型,选用QPSK、4QAM、64QAM等调制方式对单载波系统进行仿真,并与OFDM系统进行性能比较。结果表明,该方案性能与OFDM系统相当,同时有效地克服了OFDM系统的缺点。 相似文献
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利用小波包变换的多载波调制避免了OFDM技术中由多径效应引起的载波的正交性损失,同时降低了为此加入的循环前缀引起的信噪比损失,因而使用小波包变换的多载波CDMA系统(WPT-CDMA)性能优于传统的OFDM—CDMA系统。但在MIMO多用户传输环境下,接收机端的约束最小均方(CLMS)自适应波束形成算法在信号方向向量存在偏差及采样样本数目较少的情况下,会出现收敛速度慢、输出性能下降、不稳定等问题。针对这些问题本文提出应用在WPT—CDMA系统中的基于最差性能的鲁棒CLMS算法。从理论分析与仿真实验的结果都可以看到系统性能的改善。 相似文献
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多用户正交频分复用(OFDM)系统中,充分利用多载波系统的多用户分集进行合理无线资源分配,能够显著提高系统容量和最大限度提高频谱利用率。经过广泛的研究,很多有效资源分配算法已经被提出来。重点讨论了单小区多用户OFDM系统关于子载波、比特及功率等无线资源的分配问题,介绍现有的研究成果,包括常见的模型及求解方法,并介绍近期的研究热点,包括多小区系统、多入多出(MIMO)系统等。 相似文献
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Orthogonal Frequency Division Multiplexing (OFDM) is a very robust transmission procedure in multipath and frequency selective
radio channels. A Frequency Division Multiple Access (FDMA) resource allocation technique offers the opportunity of a detailed
link adaptation scheme. The combination of these transmission- and multiple access techniques in OFDM-FDMA is an ideal and
very strong candidate for the downlink of future fourth generation (4G) mobile communication systems. This technical combination
offers high cell capacities by exploiting the inherent multiuser diversity effect of the system. To apply OFDM-FDMA in the
uplink, the time and carrier synchronization accuracy becomes very important. Non-ideal synchronization of the user signals
to the carrier frequency of the base station leads to intercarrier interferences (ICI). In this paper, an analytical model
for the ICI consideration in the uplink of a multiuser OFDM-FDMA based system is derived. The impact of the carrier frequency
offset (CFO) on the performance of a cellular multiuser system with respect to different subcarrier allocation schemes is
analyzed.
相似文献
Hermann RohlingEmail: |
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对于使用OFDM传输技术的多载波系统,将OFDM技术与传统的多址接入方案,FDMA和TDMA相结合,可以实现多用户OFDM系统,这样派生出两种多址接入方案:OFDM-FDMA和OFDM-TDMA。研究了这两种多址技术,并基于IEEE 802.16a协议比较了他们的性能,用Matlab语言仿真实现了这两种多址系统。仿真结果表明OFDM-FDMA系统的误比特率性能要优于OFDM-TDMA系统。 相似文献
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For the transmission of flexible andhigh data rates in future mobile communicationsystems, the multicarrier transmission technique(Orthogonal Frequency Division Multiplexing, OFDM) canbe regarded as a possible alternative tosingle-carrier transmission that is used in today'ssystems. One of the advantages of OFDM is theflexibility concerning modulation and multiple accesstechniques. Since in OFDM the total bandwidth isdivided into a large number of subcarriers, it can beflexibly shared among all the users. In addition, themodulation scheme can be individually chosen for eachsubcarrier, thus granting the possibility of anadaptation to the radio channel characteristics. Inthis paper, the combination of two different multipleaccess schemes, OFDM-FDMA and OFDM-TDMA, and anappropriate adaptive modulation technique isconsidered for the downlink of a communication system.Different degrees of adaptivity are analysed andcompared to show the benefit of an ``intelligent'multiple access and modulation strategy. For thegiven parameters and assumptions, OFDM-TDMA withadaptive modulation yields an improvement of 6 dB insignal-to-noise ratio (SNR) at a bit error rate (BER)of 10-2. When OFDM-FDMA with adaptive subcarrierallocation is applied, the SNR gain amounts to 12.5 dB(BER of 10-2). 相似文献
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Fernando Ciriaco Taufik Abro Antonio Fischer de Toledo Paul Jean E. Jeszensky 《Wireless Communications and Mobile Computing》2011,11(6):767-782
This work aims at proposing the use of the evolutionary computation methodology in order to jointly solve the multi‐user channel estimation (MuChE) and detection problems at its maximum‐likelihood, both related to the direct sequence code division multiple access (DS/CDMA). The effectiveness of the proposed heuristic approach is proven by comparing performance and complexity merit figures with that obtained by traditional methods found in literature. Simulation results considering genetic algorithm (GA) applied to multipath, DS/CDMA and MuChE and multi‐user detection (MuD) show that the proposed genetic algorithm multi‐user channel estimation (GAMuChE) yields a normalized mean square error estimation (nMSE) inferior to 11%, under slowly varying multipath fading channels, large range of Doppler frequencies and medium system load, it exhibits lower complexity when compared to both maximum likelihood multi‐user channel estimation (MLMuChE) and gradient descent method (GrdDsc). A near‐optimum multi‐user detector (MuD) based on the genetic algorithm (GAMuD), also proposed in this work, provides a significant reduction in the computational complexity when compared to the optimum multi‐user detector (OMuD). In addition, the complexity of the GAMuChE and GAMuD algorithms were (jointly) analyzed in terms of number of operations necessary to reach the convergence, and compared to other jointly MuChE and MuD strategies. The joint GAMuChE–GAMuD scheme can be regarded as a promising alternative for implementing third‐generation (3G) and fourth‐generation (4G) wireless systems in the near future. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Precoding and channel state information sharing in cooperative macro base stations and femto sites
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H. Long W. Xiang Y. Zhang J. Wang K. Zheng W. Wang 《International Journal of Communication Systems》2014,27(10):2030-2047
Femto cell technology is a promising solution for indoor coverage of cellular systems. The interference between macro and femto cells can be mitigated via cooperation between the macro base station (BS) and the inside femto sites (FSs). In this paper, the idea of multi‐cell multi‐input and multi‐output is introduced, whereby the macro BS shares the same frequency band with the inside FSs in support of the femto users. Both single‐user and multi‐user precoding at the macro BS are proposed to support the cooperative transmission between the macro BSs and FSs. In single‐user precoding and multi‐user precoding without power allocation, only the angle information of the FS‐user channels is required to be sent from the users to the macro BS. If the magnitude information is also sent by each user, multi‐user precoding with power allocation can be employed to support cooperation between macro BSs and FSs, which is an extension of the classical water‐filling optimization problem. Theoretical derivations and an iterative algorithm are both presented to solve this optimization problem. Analytical and simulation results with respect to the signal received with interferences validate the effectiveness of cooperation between the macros BSs and FSs.Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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The next‐generation packet‐based wireless cellular network will provide real‐time services for delay‐sensitive applications. To make the next‐generation cellular network successful, it is critical that the network utilizes the resource efficiently while satisfying quality of service (QoS) requirements of real‐time users. In this paper, we consider the problem of power control and dynamic channel allocation for the downlink of a multi‐channel, multi‐user wireless cellular network. We assume that the transmitter (the base‐station) has the perfect knowledge of the channel gain. At each transmission slot, a scheduler allots the transmission power and channel access for all the users based on the instantaneous channel gains and QoS requirements of users. We propose three schemes for power control and dynamic channel allocation, which utilize multi‐user diversity and frequency diversity. Our results show that compared to the benchmark scheme, which does not utilize multi‐user diversity and power control, our proposed schemes substantially reduce the resource usage while explicitly guaranteeing the users' QoS requirements. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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捅要:研究了多用户多输入多输出(MIMO)系统在有限反馈下的一种结合单位预编码与用户调度算法的方案。在该系统中每一用户都具有多个接收天线,该方案具有较大的多用户分集增益和较小的计算复杂度,从而能够减少系统中的用户间干扰。每个用户独立地决定自己的天线合并矢量,并将最优波束矢量以及对应的估计信干噪比通过有限反馈信道反馈给基站,此时基站获取了相应的用户信道信息和用户间干扰信息。基于接收到的反馈信息,基站从预定义的码本中选取和速率最大的最优子集进行系统预编码,然后依照预编码矩阵调度欧氏距离最小的用户且用户个数不超过发送天线的数目。仿真结果显示该方案有效地改善了系统速率,特别是在用户数目较多或者信道环境较好的情况下。 相似文献