Channel Correlation Analysis of Distributed Access Links for Reliable Industrial Wireless Connectivity

The stringent reliability and latency requirements of industrial networks are challenged by harsh propagation environments. To design effective communication systems, a thorough understanding of the underlying channel characteristics is essential. Deploying multiple, spatially distributed Access Points (APs) is a promising strategy to overcome these challenges by creating resilient communication links through macro-diversity. This paper presents an experimental characterization of a multi-AP radio channel in a representative industrial laboratory environment, focusing on the 6 GHz band (upper FR1), enabling the investigation of frequency-dependent propagation mechanisms beyond traditional sub-6 GHz cellular bands. We analyze key statistical properties, including inter-link correlation, coherence distance, and coherence bandwidth, to assess the potential for both macro- and micro-diversity. The results demonstrate that the channels from distributed APs are largely uncorrelated, highlighting a significant opportunity for macro-diversity. Conversely, the measured coherence distances far exceed typical device dimensions, suggesting limited returns from single-device spatial diversity. An evaluation of selection combining, equal-gain combining, and maximal-ratio combining techniques confirms that distributed APs can provide substantial diversity gains, ranging from 2.6 dB to 23.1 dB. These findings validate the deployment of coordinated, distributed AP architectures as a crucial strategy for achieving robust, low-latency connectivity in future industrial settings.