Super-Resolution for Achieving Frequency Division Duplex (FDD) Channel Reciprocity
Super-Resolution for Achieving Frequency Division Duplex (FDD) Channel Reciprocity
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用于实现频分双工 (FDD) 信道互易性的超分辨率
DOI：
10.1109/spawc.2018.8445970
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Y. Liu
中科院分区：
文献类型：
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作者：
Wanshan Yang;Lijun Chen;Y. Liu
发射端的信道状态信息(CSIT)使无线通信系统能够充分利用信道的自由度。时分双工(TDD)系统可以利用信道互易性从反向链路训练中获得前向链路CSIT。我们解决了对于频分双工(FDD)系统似乎不可能完成的任务，在FDD系统中，传统方法是从接收器的反馈中获得CSIT。信道状态反馈会造成时延并消耗大量的系统资源，特别是在发送天线数量很大的情况下，例如在大规模MIMO系统中。然而，如果从一个频带中的导频信号准确地估计出诸如每个单独路径的复路径增益、路径延迟和到达/离开角之类的信道参数，则可以根据这些参数来计算另一个频带中的信道状态。精确度是关键，因为频段间频差的乘积会放大微小的估计误差。对于窄带和单天线系统，无法达到所需的精度。但现在和未来的无线系统已经并将拥有越来越大的带宽和天线数量，使FDD信道互惠成为可能。为了实现FDD信道的互易性，我们提出使用超分辨率理论。另一种可能的压缩感知方法是将信道参数放在多维网格上，并对网格的每个点估计相应的复增益。我们将这两种方法应用到我们的问题中，并表明压缩感知方法不太适合这一目的，而超分辨率方法可以实现我们的目标。
Channel state information at transmitter (CSIT) allows wireless communication systems to fully utilize the degree of freedom of the channel. Time division duplex (TDD) systems can take the advantage of channel reciprocity to obtain forward link CSIT from reverse link training. We tackle the seemingly impossible task of doing the same for frequency division duplex (FDD) systems, where the conventional method is to obtain CSIT from feedback from the receiver. Channel state feedback causes delay and consumes prohibitive amount of system resource, especially when the number of transmit antennas is large, such as in massive MIMO systems. However, if the channel parameters, such as the complex path gain, path delay, and angle of arrival/departure of each individual path, are accurately estimated from pilot signals in one frequency band, the channel state in another frequency band can be calculated from these parameters. Accuracy is the key because small estimation error will be magnified by the multiplication of the frequency difference between the bands. The required accuracy is not achievable for narrow band and single antenna systems. But current and future wireless systems have and will have increasingly large bandwidth and number of antennas, making the FDD channel reciprocity possible. To achieve the FDD channel reciprocity, we propose to employ super-resolution theory. Another possible compressed sensing approach is to put the channel parameters on a multi-dimensional grid and for each point of the grid, estimate the corresponding complex gain. We adapt both approaches for our problem and show that the compressed sensing approach is not well suited for this purpose and the super-resolution approach can achieve our goal.