Pilot symbol assisted modulation (PSAM) is widely used to obtain the channel state information (CSI) needed for coherent demodulation. It allows the density of pilot symbols to be dynamically chosen depending on the channel conditions. However, the insertion of pilots reduces the spectral efficiency, more severely when the channel is highly time-variant and/or frequency-selective. In these cases a significant amount of pilots is required to properly track the channel variations in both time and frequency dimensions. Alternatively, non-coherent demodulation does not require any CSI for the demodulation independently of the channel conditions. For the particular case of up-link (UL) based on massive single input - multiple output (SIMO) combined with orthogonal frequency division multiplexing (OFDM), we propose to replace the traditional reference signals of PSAM by a new differentially-encoded data stream that can be non-coherently detected. The latter can be demodulated without the knowledge of the CSI and subsequently used for the channel estimation. We denote our proposal as hybrid demodulation scheme (HDS) because it exploits both the benefits of a coherent demodulation scheme (CDS) and a non-coherent demodulation scheme (NCDS) to increase the spectral efficiency. The mean squared error (MSE) of the channel estimation, bit error rate (BER), achieved throughput and complexity are analyzed to highlight the benefits of this differential data-aided channel estimation as compared to other approaches. We show that the channel estimation is almost as good as PSAM, while the BER performance and throughput are improved for different channel conditions with a very small complexity increase.

中文翻译：

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上行大规模SIMO-OFDM的差分数据辅助信道估计

导频符号辅助调制（PSAM）被广泛用于获得相干解调所需的信道状态信息（CSI）。它允许根据信道条件动态选择导频符号的密度。然而，导频的插入降低了频谱效率，当信道具有高度时变和/或频率选择性时，频谱效率会更严重。在这些情况下，需要大量的导频来正确跟踪时间和频率维度上的信道变化。备选地，非相干解调不需要独立于信道条件的任何CSI用于解调。对于基于大规模单输入多输出（SIMO）结合正交频分复用（OFDM）的上行链路（UL）的特殊情况，我们建议用一种新的差分编码数据流代替PSAM的传统参考信号，该数据流可以非相干检测。后者可以在不知道CSI的情况下进行解调，然后用于信道估计。我们将我们的建议表示为混合解调方案（HDS），因为它利用了相干解调方案（CDS）和非相干解调方案（NCDS）的优势来提高频谱效率。分析了信道估计的均方误差（MSE），误码率（BER），已实现的吞吐量和复杂性，以突出此差分数据辅助信道估计与其他方法相比的优势。我们表明，信道估计几乎与PSAM一样好，