This letter addresses Time-Of-Arrival estimation for an indoor positioning system (IPS) made up of distributed 5G small cells by focusing on the Iterative Adaptive Approach (IAA) with Orthogonal Frequency Division Multiplexing (OFDM) signals. While IAA has been successfully applied to many other areas, its application to 5G IPS is not straightforward. In fact, even the current fast implementation of IAA is hardly compatible with 5G chips having limited computational capability, due to large number of sub-carriers of OFDM signals. To address this problem, we pursue the idea of averaging over a number of successive sub-carriers sequentially. Since our analysis shows that the direct Sub-carrier Average (SA) operation exhibits the asinc modulation effect on channel response, possibly leading to miss-detection of Direct Path (DP), we further propose a channel compensation-based SA method and provide a quantitative analysis of the signal-to-noise ratio of the DP to demonstrate its robustness. The resulting SA-based fast IAA (SA-FIAA) algorithm can achieve comparable performance as the standard IAA, while reducing computational cost by over 2 − 3 orders of magnitude, making it practically tractable in 5G IPSs. The effectiveness and computational efficiency of the proposed approach are well demonstrated through real-world experiments.

中文翻译：

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分布式 5G 小基站室内定位的快速迭代自适应方法

这封信通过关注具有正交频分复用 (OFDM) 信号的迭代自适应方法 (IAA)，解决了由分布式 5G 小型蜂窝组成的室内定位系统 (IPS) 的到达时间估计。虽然 IAA 已成功应用于许多其他领域，但其在 5G IPS 中的应用并不简单。事实上，由于 OFDM 信号的子载波数量众多，即使是当前的 IAA 快速实现也很难与计算能力有限的 5G 芯片兼容。为了解决这个问题，我们追求对多个连续子载波顺序进行平均的想法。由于我们的分析表明，直接子载波平均 (SA) 操作对信道响应表现出 asinc 调制效应，可能导致直接路径 (DP) 的漏检，我们进一步提出了一种基于通道补偿的 SA 方法，并对 DP 的信噪比进行了定量分析，以证明其鲁棒性。由此产生的基于 SA 的快速 IAA (SA-FIAA) 算法可以实现与标准 IAA 相当的性能，同时将计算成本降低超过 2-3 个数量级，使其在 5G IPS 中实际上易于处理。通过真实世界的实验很好地证明了所提出方法的有效性和计算效率。使其在 5G IPS 中几乎易于处理。通过真实世界的实验很好地证明了所提出方法的有效性和计算效率。使其在 5G IPS 中几乎易于处理。通过真实世界的实验很好地证明了所提出方法的有效性和计算效率。