共查询到18条相似文献,搜索用时 765 毫秒
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在天线性能优化问题的研究中,MIMO-OFDM 技术将 OFDM 与空时编码技术有机的结合在一起,能够大幅度的提高无线通信系统的信道容量和传输速率.为了有效地抵抗多径衰落、抑制干扰和噪声,提出了一种改进的 LS 频域信道估计的改进算法即分组 LS 频域信道估计算法.算法根据 MIMO-OFDM 系统相邻子载波频域信道响应变化缓慢的结论,把所有天线发送的 OFDM 子载波分成多组来进行信道估计.通过对算法的仿真建模并进行仿真,表明算法具有简化算法复杂度以及提高抗噪声和信道估计能力,在抗多普勒频移等方面有更好的性能.算法可为多天线系统信道估计的研究提供了设计依据. 相似文献
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信道估计是MIMO-OFDM系统实现优良传输的一项重要环节。半盲信道估计算法是将MIMO-OFDM信道矩阵进行分解,分别利用未知数据和已知导频信息来完成信道估计。在利用未知数据进行估计时,提出一种利用频域子载波分组的子空间分解方法,不仅降低了计算复杂度,而且同时提高了信道估计的精度。利用已知的导频信息和未知数据估计出来的结果,可以求得最后的信道矩阵。相对于传统的频域子空间分解的半盲估计方法,算法可以减小计算复杂度80%,同时提高了估计精度平均1~2dB。仿真结果证明了算法具有良好的性能表现。 相似文献
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单载波MIMO系统的一种抑制噪声的MMSE信道估计方案 总被引:2,自引:0,他引:2
单载波MIMO系统的频域均衡是对抗信道频率选择性衰落的有效方法,它的良好性能依赖于接收端准确的信道估计(ChannelEstimation,CE)。常见的迫零信道估计(ZF-CE)在导频频域非恒包络的情况下,会使信道估计误差增大而造成误码性能降低。本文通过设计导频结构,提出一种实用的最小均方误差信道估计(MMSE-CE)算法和抑制噪声的内插方法,构成单载波MIMO系统频域均衡的一种信道估计方案。理论分析和仿真结果表明,该方案能较好的减小导频频域能量不恒定造成的性能损失,误码性能比ZF-CE显著提高。 相似文献
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针对地空信道时变快,正交频分复用/偏移正交幅度调制(OFDM/OQAM)系统存在固有干扰的问题,提出一种信道估计算法。该信道估计算法包含一种新型的梳状导频结构和一种改进的线性插值算法。提出的新型梳状导频通过将导频周围数据置零来消除系统的固有干扰和减小子载波间干扰对信道估计的影响,且导频分布在整个时间轴上,因而可以较好的跟踪信道状态;改进的线性插值算法通过在时域插零,来减小信道噪声和系统干扰对信道估计的影响。仿真结果表明,提出的梳状导频相比于传统梳状导频具有较好的优势,可有效提高系统的抗误码性能;改进的线性插值算法相比于传统插值算法可有效提高系统的可靠性。 相似文献
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在分析多径噪声环境中信道估计经典算法的基础上,提出一种基于二维导频和降噪滤波的信道估计改进算法。文中采用的二维导频设置图案,充分保留了信道信息,从中可提取信道参数的最优初始估计。在此基础上,通过DFT/IDFT变换将信道频率响应子空间和噪声子空间分离,进行降噪滤波。仿真结果显示,在多径时变衰落信道下,利用以上两种提出的信道估计方法有效提高系统的估计性能。 相似文献
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从系统设计角度研究了MIMO—OFDM系统的信道估计方法,提出—种基于空频域的最优导频设计算法。该算法适用于快速时变和频率选择性衰落信道,在基于LS准则的信道估计算法中无需矩阵求逆运算,大大降低了复杂性。通过计算机仿真证明该算法在空频编码的信道估计中具有最小MSE性能。 相似文献
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针对基于导频污染的大规模多输入多输出系统,提出一种空间交替广义期望最大化(SAGE)迭代的信道估计算法。将发送和接收的导频符号形成完备的数据空间集,利用基于导频的最小均方误差估计器初始化信道参数,通过导频符号和软信息迭代改进并更新初始估计数据。实验结果表明,该算法通过一次SAGE迭代即可实现精度收敛,且在高信噪比及导频污染的情况下相比基于导频的估计器具有更高的估计精度及频谱效率。 相似文献
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An adaptive bit and power allocation algorithm for filtered multitone (FMT) system was proposed based on Signal Distortion Ratio (SDR). Performance of adaptive system in slow fading Rayleigh channel was analyzed. The proposed algorithm is much simpler than the others. The simulation results show that the system outperforms fixed modulation FMT system in Bit Error Ratio (BER),and it is a practical bit allocation algorithm. 相似文献
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This paper presents a new parallel transmission framework for reliable multimedia data transmission over spectrally shaped channels using multicarrier modulation. We propose to transmit source data layers of different perceptual importance in parallel, each occupying a number of subchannels. New loading algorithms are developed to efficiently allocate the available resources, e.g., transmitted power and bit rate, to the subchannels according to the source layers they transmit. Instead of making the bit error rate of all the subchannels equal as in most existing loading algorithms, the proposed algorithm assigns different error performance to the subchannels to achieve unequal error protection for different layers. The channel induced distortion in mean-square sense is minimized. We show that the proposed system can be applied nicely to both fixed length coding and variable-length coding. Asymptotic gains with respect to channel distortion are also derived. Numerical examples show that the proposed algorithm achieves significant performance improvement compared to the existing work, especially for spectrally shaped channels commonly used in in ADSL systems 相似文献
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本算法把L-通道区分成两个三边通道,从分析割值出发,确定L-型通过的初始宽度。为达到总体布线最优,采用迭代法和改进的“贪婪,算法,交替实现水平和垂直通道的布线。 相似文献
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《Journal of Network and Computer Applications》2012,35(6):2092-2104
Various burst construction algorithms for Orthogonal Frequency Division Multiple Access (OFDMA) were proposed. However, these algorithms did not consider the downlink burst characteristics that are specified in IEEE 802.16 standard. This work therefore presents the Best Block-Oriented (BBO) algorithm. BBO not only complies with the downlink burst characteristics, but also addresses three further issues that are important to obtain high throughput: BBO reduces external fragment by shrinking a burst to fit into the available bandwidth area if the available area is otherwise insufficient to accommodate it; BBO shrinks the burst area to minimize internal fragment if the requested bandwidth has been satisfied; to find the subchannels that have good channel quality, BBO evaluates the channel quality of subchannels and constructs the burst in the subchannels that provide the highest throughput. Simulation results show that BBO yields 1.2–9 times the throughput that has been achieved using previous algorithms under a heavy load. 相似文献
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为了信道传输质量得到保证,提出了一种通信信道的盲辨识与均衡算法。算法将信道建模成IIR信道并在其输出端过采样,分别对信道传输函数的AR参数和MA参数进行辨识。在辨识MA参数时将信道分解成多个子信道,使得未知信道的信息被充分利用,提高了系统辨识的精度。同时该算法不需要信道信息和输入信号的统计特性,因而具有广泛的适用性。仿真试验表明该算法具有良好的性能。 相似文献
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As the next-generation Wireless LANs (WLANs) will provide the ubiquitous high-data-rate network coverage, the traditional contention-based Medium Access Control (MAC) scheme may be unable to fulfill the requirement of efficient channel access. To address this problem, several research works have proposed the random access systems combined with Orthogonal Frequency Division Multiplex Access (OFDMA) technology. Access granularity control is a crucial issue in this combination. Specifically, this issue focuses on how to tune the subchannel bandwidth and the number of accessible subchannels towards the maximum channel utilization. This paper analyzes access granularity control in an OFDMA system that adopts a multichannel Carrier Sensing Multiple Access (CSMA) MAC and resolves contention by the frequency-domain backoff. The theoretical analysis verifies the significance of access granularity control. In addition, the simulation experiments demonstrate that the proposed dynamic access granularity control algorithms notably outperform the traditional ones that divide channel band statically and adjust the number of accessible subchannels empirically. 相似文献