共查询到18条相似文献,搜索用时 125 毫秒
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针对同时同频全双工无线通信系统,考虑远端到近端的无线信道为多径瑞利衰落信道,近端发射天线到接收天线的自干扰信道为加性白高斯噪声信道,分析了同时同频全双工传输场景中,自干扰射频抵消幅度及载波相位误差对OFDM误码率的影响。结果表明,在相同信干比和信噪比条件下,幅度和载波相位估计误差的绝对值越小,误码率越低;针对载波频率2.3 GHz, OFDM子载波个数4096,子载波间隔15 kHz的同时同频全双工传输方式,在信干比为-70 dB,误码率为10-2时,若期望信噪比损失小于0.8 dB,则需要射频干扰抵消的载波相位估计误差的绝对值小于610-6,幅度估计相对误差的绝对值小于310-5;若期望获得40 dB的射频自干扰抑制效果,则射频干扰抵消的载波相位估计误差的绝对值小于0.5,幅度估计相对误差绝对值小于1%。 相似文献
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高移动环境下利用无线信号空域特征实现OFDM系统的ICI消除 总被引:1,自引:0,他引:1
高移动性正交频分复用(OFDM)系统受多普勒扩展影响产生严重的子载波间干扰(ICI)。根据实际场景中无线信号的空域传播特征,采用WINNER II信道模型建模无线信道,提出利用阵列天线作为接收天线从空域角度消除ICI。该方法利用波达方向估计和波束形成网络对接收信号进行分离,并对分离后的各路信号分别做多普勒频偏补偿,最后将各路处理后的信号进行最大比合并获得多波束分集增益。仿真结果表明,所提方法可有效减小ICI和误码率平台,较处理前可获得5~7 dB的信干比增益。 相似文献
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OFDM/OQAM系统中联合迭代信道估计和信号检测 总被引:1,自引:2,他引:1
与基于复数域空间正交条件的传统正交频分复用系统(OFDM with Cyclic Prefix, CP-OFDM)有所不同,基于交错正交调制的正交频分复用系统(OFDM/Offset QAM, OFDM/OQAM)满足实数域空间严格正交条件。因此在多径衰落信道条件下,CP-OFDM系统中的信道估计方法会导致OFDM/OQAM系统严重的字符间干扰和载波间干扰。该文结合OFDM/OQAM系统结构特点,提出了一种基于迭代信道估计和信号检测算法。该算法通过信道估计器和接收到的信号互相交换信息,消除导频序列中的字符间干扰和载波间干扰,提高信道估计和信号检测的准确度。仿真分析结果表明,经过一定次数迭代处理后,OFDM/OQAM迭代信道估计性能趋近于理想信道估计性能。 相似文献
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OFDM符号是由多个子载波信号叠加而成,为确保各子载波之间的正交性,就对载波间的同步有很严格的要求,否则将造成信道间干扰和符号间干扰,严重影响OFDM系统的性能。提出一种新的基于循环前缀的OFDM时频同步算法,通过仿真,将新算法和传统的ML算法及集相关算法相比较。仿真结果表明,新算法具有更好的频偏和定时估计性能。 相似文献
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UWB系统抗干扰扩频编码的研究 总被引:1,自引:0,他引:1
将正交频分复用(OFDM)技术和正交扩频交织编码技术相结合,并引入到超宽带(UWB)通信系统中, 通过正交扩频将信息比特扩展到各个子带的子信道中,再进行交织编码,可大大提高系统抗窄带干扰能力。仿真结果表明,这种正交扩频交织编码技术具有明显的抗窄带干扰顽健性,系统信干比提高5dB左右,误比特率改善1-2个数量级。 相似文献
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基于并行干扰抵消的OFDM/OQAM系统中的信号检测方法 总被引:1,自引:0,他引:1
在多径衰落信道中,基于交错正交幅度调制的正交频分复用(OFDM with Offset QAM,OFDM/OQAM)系统使用迫零均衡器进行信号检测时,不能完全消除信道复数特性和滤波器实数正交特性引入的时域符号间干扰和频域子载波间干扰,及信道估计误差导致的误码率性能损失。该文利用对数据初始判决并重构相邻载波及符号间干扰的思想,通过分析采用迫零均衡信号检测时的残余干扰与信道估计误差干扰,提出了一种基于并行干扰抵消和迫零均衡器结合的OFDM/OQAM信号检测方法,并在IEEE 802.22技术标准的两种典型多径衰落信道中进行了计算机仿真与比较研究。仿真结果表明,与基于迫零均衡的检测方法相比,基于并行干扰抵消的迭代信号检测方法在误码率为1%时,可获得1 dB至2 dB的性能提升。 相似文献
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Hsiao-Chun Wu Yiyan Wu 《Wireless Communications, IEEE Transactions on》2007,6(5):1605-1609
The intercarrier interference (ICI) matrix for the orthogonal frequency division multiplexing systems usually has a fairly large dimension and changes over time for mobile communications. In this paper, we design the modified maximum-length shift-register sequences and propose a new distributive allocation scheme together with a linear interpolation for both pilot-aided and non-pilot-aided ICI vector estimates; this new method can combat the realistic non-circulant ICI matrix problem, where almost all other existing schemes could not perform effectively. Monte Carlo experiments show the significant advantages of our new ICI matrix estimator especially when the signal-to-noise ratio is larger than 15 dB 相似文献
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Arvind Kumar Rajoo Pandey 《AEUE-International Journal of Electronics and Communications》2009,63(7):569-575
Orthogonal frequency division multiplexing (OFDM) is a very important modulation technique in wideband wireless communication and multimedia communication systems. While, it can effectively deal with multipath delay spread produced by frequency fading channels, its main drawback is the effect of frequency offset (FO) produced by the receiver local oscillator or by motion-induced Doppler. The FO breaks the orthogonality among the subcarriers and hence causes intercarrier interference (ICI). In this paper, ICI caused by frequency drift is eliminated by equalizing the complex weighting coefficients of interference. In most of the commonly used ICI cancellation schemes, bandwidth efficiency suffers because of the requirement of redundancy in the transmission. In the proposed scheme, repetition of data symbols or transmission of training sequence is not required. Thus, the bandwidth efficiency of normal OFDM system is maintained. The improved performance of the present scheme is confirmed through extensive simulations. 相似文献
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For OFDM based system with Single-Frequency Networking (SFN), ICI (inter-cell interference), especially uplink ICI, becomes a bottleneck to improve system performance. Since the conventional interference management scheme with OI (overload indicator) can not show the instantaneous ICI, this paper proposes a method to reduce ICI by utilizing channel reciprocity of TD-LTE system. In the proposed scheme, UE shall make a decision whether to reduce its power or not after predicting the instantaneous ICI level according to the scheduling results. The system simulation results show that the proposed scheme can reduce the uplink ICI effectively and improve the system performance such as system spectrum efficiency, 10% user throughput, 50% user throughput, packet drop rate etc. significantly while keep 5% cell edge user throughput loss less than 5%. For example, the proposed scheme improved system spectrum efficiency about 50% and 50% user throughput gain is larger than 140%. Meanwhile, the proposed scheme controls the system ICI level and variance effectively. The mean system ICI level and variance are reduced by 4.5dB and 18dB respectively. The proposed scheme can be joint implemented with those existing ICI mitigation methods such as (soft) frequency reuse, power control etc. to further improve the system performance. 相似文献
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Phase noise in orthogonal frequency division multiplexing (OFDM) systems destroys the orthogonality of the subcarriers and inter-carrier interference (ICI) is caused. In this paper, the ICI self-cancellation scheme is adopted to combat the ICI caused by phase noise in OFDM systems. Moreover, the error coefficients are defined and the theoretical expressions of carrier to interference ratio (C/I) with and without the ICI self-cancellation scheme are separately derived. From the simulation results, it is verified that the ICI self-cancellation scheme obviously decreases the amount of the ICI caused by phase noise and the improvement of C/I could reach 10 dB when the normalized 3 dB bandwidth of phase noise is 0.4. However, the convolutional coding OFDM (COFDM) system could supply more performance gain at the expense of increasing decoder complexity compared to OFDM system with the ICI self-cancellation scheme in the frequency-selective channel. 相似文献
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多径信道下OFDM系统中的两种线性载波间干扰抑制技术 总被引:3,自引:0,他引:3
载波间干扰(ICI)是影响正交频分复用(OFDM)系统性能的重要因素。该文研究了不同延迟线长度L下的频域RAKE(F-RAKE)和频域均衡(F-FIR)两种线性ICI抑制技术。假设接收端已知信道信息,F-FIR采用最小均方误差(MMSE)准则。结果表明L=3时,F-RAKE比标准接收机的载干比(CIR)高2~5dB,而F-FIR则高出2~7dB;随着L的增加,两种接收机所能获得的CIR增益逐渐降低。从计算复杂度来看,F-FIR的计算量是F-PAKE的L倍,工程中可以通过选取不同延迟线长度和接收机结构来达到计算复杂度和性能的折衷。 相似文献
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For orthogonal frequency-division multiplexing (OFDM) communication systems, the frequency offsets in mobile radio channels distort the orthogonality between subcarriers resulting in intercarrier interference (ICI). This paper studies an efficient ICI cancellation method termed ICI self-cancellation scheme. The scheme works in two very simple steps. At the transmitter side, one data symbol is modulated onto a group of adjacent subcarriers with a group of weighting coefficients. The weighting coefficients are designed so that the ICI caused by the channel frequency errors can be minimized. At the receiver side, by linearly combining the received signals on these subcarriers with proposed coefficients, the residual ICI contained in the received signals can then be further reduced. The carrier-to-interference power ratio (CIR) can be increased by 15 and 30 dB when the group size is two or three, respectively, for a channel with a constant frequency offset. Although the redundant modulation causes a reduction in bandwidth efficiency, it can be compensated, for example, by using larger signal alphabet sizes. Simulations show that OFDM systems using the proposed ICI self-cancellation scheme perform much better than standard systems while having the same bandwidth efficiency in multipath mobile radio channels with large Doppler frequencies 相似文献
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本文为W波段辐射计设计了一副口径为300mm偏馈反射面天线,天线要求的工作频率为94.5GHz,副瓣电平低于-25dB,交叉极化电平低于-30dB,半功率波束宽度优于1?。文中采用较小偏置角以改善偏置天线的交叉极化特性,采用焦面场匹配法和模比利用法设计了匹配馈源,通过仿真优化设计,得到良好的波瓣等化电平和驻波比。测量结果表明,测量值与理论值吻合,满足辐射计的指标要求。 相似文献