A Geography-Inspired and Self-Adaptive Clustering Algorithm: A Study in Channel Measurement

TL;DR

The paper tackles the challenge of clustering MPCs in a single PDAP snapshot and linking them to physical scatterers without prior information. It introduces a geography-inspired, self-adaptive clustering algorithm that builds contour lines in the PDAP, extracts characteristic points on contour ridges, and uses these CPs to guide MPC clustering and scatterer reconstruction. A new performance metric, the power gradient consistency index, is proposed to capture the radially decreasing power profile around cluster centers, and the approach is validated on outdoor THz measurements, achieving decimeter-level scatterer localization (RMSE around 0.1 m) and superior internal clustering metrics compared with conventional methods. The method provides physical interpretability, is robust to threshold choices, and generalizes across frequencies and scenarios, making it practically impactful for channel modeling and localization in high-frequency wireless systems.

Abstract

The phenomenon that multi-path components (MPCs) arrive in clusters has been verified by channel measurements, and is widely adopted by cluster-based channel models. As a crucial intermediate processing step, MPC clustering bridges raw data in channel measurement and cluster characteristics for channel modeling. In this paper, a physical-interpretable and self-adaptive MPC clustering algorithm is proposed, which can locate both single-point and wide-spread scatterers without prior knowledge. Inspired by the concept in geography, a novel metaphor that interprets features of MPC attributes in the power-delay-angle profile (PDAP) as topographic concepts is developed. In light of the interpretation, the proposed algorithm disassembles the PDAP by constructing contour lines and identifying characteristic points that indicate the skeleton of MPC clusters, which are fitted by analytical models that associate MPCs with physical scatterer locations. Besides, a new clustering performance index, the power gradient consistency index, is proposed. Calculated as the weighted Spearman correlation coefficient between the power and the distance to the center, the index captures the intrinsic property of MPC clusters that the dominant high-power path is surrounded by lower-power paths. The performance of the proposed algorithm is analyzed and compared with the counterparts of conventional clustering algorithms based on the channel measurement conducted in an outdoor scenario. The proposed algorithm performs better in average Silhouette index and weighted Spearman correlation coefficient, and the average root mean square error (RMSE) of the estimated scatterer location is 0.1 m.

Figures (14)

• Figure 1: Schematic diagram of the proposed clustering algorithm.
• Figure 2: The example of contour lines.
• Figure 3: The example of a contour line tree.
• Figure 4: The algorithm of contour line tree construction.
• Figure 5: The example of characteristic points.