共查询到18条相似文献,搜索用时 56 毫秒
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正交频分多址(OFDMA)是以OFDM调制为基础的新一代无线接入技术,在这种方式中,多址是通过给每个用户分配可用子载波总数的一部分来实现的。介绍了一种OFDMA下行链路的实时动态子载波分配算法,算法根据各个子载波对各个用户的瞬时信道增益,在使系统总的发送功率最小的准则下,为各用户分配最优的子载波组。最后用MATLAB语言仿真实现了该算法.仿真结果表明该算法性能要优于传统的静态子信道方案。 相似文献
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初始Ranging过程是WiMAX系统上行链路中的重要过程,首先对基于差分法的Ranging检测算法进行了深入分析,然后提出了一种改进算法,该改进算法提高了低SNR下的检测率,且时偏估计的准确度大大提高,能够直接支持超远距离覆盖,解决了WiMAX系统上行接入受限问题。最后通过计算机仿真比较了改进算法的性能,仿真结果表明,所提出的改进算法在技术复杂度和系统性能上具有较大的优势。 相似文献
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一种自适应的OFDMA系统下行分组调度算法 总被引:1,自引:0,他引:1
提出了一种适合于OFDMA(正交频分多址接入)系统的资源分配与调度算法,该算法利用物理层的信道信息和MAC层的队列状态信息,并综合考虑了数据分组传输的时延要求和业务的优先级,采取资源块与子载波分配相结合的资源分配方式。仿真结果表明,该算法在吞吐量和公平性方面都得到了较好的改善。 相似文献
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利用逐次干扰抵消多用户检测结构,结合空时RAKE接收机,提出一种空时逐次干扰抵消多用户检测算法.仿真结果表明,该算法相比传统空时RAKE接收机有近5 dB的增益,误码率有了相当的改进. 相似文献
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小区搜索是IEEE 802.16e系统的关键技术之一.由此提出了一种低复杂度的快速联合小区搜索和整数倍频偏估计算法的VLSI结构.该结构采用差分估计方法,有效地解决了频率选择性衰落信道对检测性能的影响.详细描述了该结构的各组成单元和设计方法,并在Altera公司的EP2S130器件上进行了仿真综合验证.验证结果表明,该模块最高工作频率为103.7MHz,能够正常应用于IEEE 802.16e接收机或其他类似通信系统. 相似文献
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IEEE802.16e标准增强了对用户移动性的支持。基于IEEE802.16e的OFDMA系统下行链路,分析和改进符号定时和频率同步的算法,并给出AWGN和ITUVehicularA信道下系统的仿真性能。 相似文献
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文章介绍了基于IEEE802.16e协议的野战指挥所无线局域网的框架设计。首先简要介绍了802.16e协议,其次提出了基于802.16e协议的野战指挥所无线局域网的设计方法。对于野战条件下,快速、高效组建野战指挥所无线局域网,提供保密、实时、可靠、高速、大容量、多类型的业务具有一定的借鉴意义。 相似文献
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Feng‐Ming Yang Wei‐Mei Chen Tzu‐Kai Cheng Jean‐Lien C. Wu 《International Journal of Communication Systems》2012,25(7):926-942
Because the bandwidth usage of wireless transmission is limited, one of the major research topics in this field is to improve system throughput by supporting multiple users with limited bandwidth resources. Although there are several studies on cross‐layer designs for improving system throughput, previous research on quality‐of‐service guarantee and fairness are relatively rare. This study proposes a cross‐layer subcarrier permutation (CLSP) mechanism that uses cross‐layer strategies to select suboptimal subcarriers. Service flows simulations in the IEEE 802.16e system indicate that CLSP achieved a lower delay time and a long‐term fairness among multiple users. Experimental results further show that the throughput of CLSP is 28 percent higher than that of the partial usage of subchannels model using the orthogonal frequency division multiple access technique. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Zhaoyang Zhang Peng Cheng Xiangwei Zhou Peiliang Qiu 《International Journal of Communication Systems》2009,22(4):375-398
System synchronization and channel estimation are two key problems of IEEE 802.16e Orthogonal Frequency Division Multiplex Access (OFDMA) downlink system. According to the standard, system synchronization is completed through the cell search procedure, which includes two steps: frame detection and cell‐ID identification. First, based on the special time‐domain (TD) and frequency‐domain (FD) structures of the preamble, we propose two novel frame detection ms: the TD algorithm and the FD algorithm. Their robustness performance is nearly the same, and the complexity of the FD algorithm is only of that of the TD algorithm. Then, an efficient cell‐ID identification algorithm is proposed, in which the necessary correlation length can be dramatically shortened even without any a priori channel knowledge. Thereby, it greatly reduces the cell search time. As for the problem of channel estimation, a cluster‐based channel estimation method is proposed. It is based on the special pilot distribution of IEEE 802.16e and utilizes the continuity of channel variations to mitigate the impact of time‐variant channel. System simulation results show that the proposed algorithms are both robust and efficient. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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Jaeho Chung Yusuk Yun Seungwon Choi 《International Journal of Communication Systems》2011,24(12):1627-1646
This paper details the downlink performance analysis of a MIMO (Multi‐Input Multi‐Output) system that combines adaptive beamforming (ABF) and spatial multiplexing (SM) procedures. The combination of MIMO signal processing with ABF is applied to WiBro (Wireless Broadband), the South Korean orthogonal frequency division multiple access (OFDMA) system that follows the IEEE 802.16e standard. Performance analysis is based on the results of experiments and simulations obtained from a prototype system implementation and fixed‐point simulator. Both the prototype experiments and simulations demonstrate that the ABF‐MIMO OFDMA system improves the required signal to noise ratio (SNR) over the conventional MIMO OFDMA system by 3 dB (QPSK)/2.5 dB (16‐QAM) for the frame error rate of 1% in the WiBro signal environments. From the implementation of the prototype system and its experimental results, we verify the feasibility of the ABF‐MIMO technology for realizing a practical WiBro base station. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献