# Correlation Technologies for Emerging Wireless Applications
## 5 Conclusions  
In this paper, we have presented correlation technologies for measuring the power density of mobile devices using OTA testing. Measurements obtained using minimally invasive electro-optical (EO) probes are compared to full-wave 3D EM solvers (EMPIRE, HFSS, CST), demonstrating excellent agreement for applications at mmWave frequencies.  
New ASIC-embedded smart connectors are developed for bringing correlation-based signal processing close to antenna modules. The influence of separation distance between the device under test (DUT) and the probing system (PS) is studied using spatial correlation functions and their propagation attributes implemented through FPGA programming based on convolutional algorithms (_cognition ready array-processing_). Proposed correlation-based energy-density and power-density metrics in providing stronger robustness to noise represent valuable insights to mobile equipment manufacturers, network operators, and standardization bodies. Perspectives for optically synchronized interferometric correlation technologies are drawn for accurate measurements in noisy environments of stochastic EM fields using power-spectra, energy-spectra, and entropy metrics. At baseband frequencies, ongoing work is relative to new DSP-based convolutional accelerators compliant with IEEE  
Figure 12: Dual-channel with delay lines and power-splitting for noise decorrelation (**a**). Test-bench solution including broadband delay lines and power-splitters for noise decorrelation using IQ signals (**b**).  
P1765 standard for pushing EVM [24] measurement solutions to industrial testing both in connectorized and OTA configurations using correlation technologies. Implementation of DSP-based convolutional accelerators into advanced FD-SOI-ASIC platforms for co-integration with adaptive RF/mmWave front-end modules will enable real-time extraction of auto-correlation and cross-correlation functions of stochastic signals for mobile devices and systems.  
The proposed correlation technologies will enable an efficient combination of information signal theory (IT) and physical information theory (PT) into a unified approach: _Shannon's entropy_ can be directly related to _Boltzmann's entropy_. The Shannon-McMillan-Breiman theorem [31] provides a formal basis for such a unified approach where Shannon's entropy can be directly related to Boltzmann's entropy for accurate extraction of key parameters characterizing the quality of RF wireless systems such as signal-to-noise ratio (SNR), Error Vector Magnitude (EVM), channel capacity (CA), data rate (DR) and antennas tuning in MIMO applications.  
Beyond classical RF applications, proposed correlation technologies will foster new perspectives in creating natural bridges between \"Correlation\" and \"Intrication\", in the quantum-physics sense, that can be leveraged for future Qubit-based coding, encryption, and signal-processing. Quantum computing and quantum radar [46; 47; 48; 49; 50; 51; 52; 53; 54; 55; 56; 57; 58] sensing-related applications will benefit from such holistic correlation technologies [59; 60; 61]. Spintronics-based sensing solutions introduced in [61] will enable new correlation-aware wireless communication systems.  
Conceptualization, S.W.; methodology, S.W. Validation Measurement versus 3D Modeling of DUT, F.F., T.V.D., D.B.; Measurement using EO Probing, L.D., G.G.; writing--original draft preparation, S.W.; writing--review and editing, S.W.; DSP and FPGA analysis, V.H. All authors have read and agreed to the published version of the manuscript.  
This research was funded by eV-Technologies.  
The authors are very grateful to [PERSON] for ongoing work on Correlation-based EVM measurement of MIMO systems.  
The authors declare no conflict of interest.  
The following abbreviations are used in this manuscript:  
FF-CF Field-Field correlation functions  
OTA Over-The-Air  
ASIC Application Specific Integrated Circuit  
EVM Error Vector Magnitude  
DSP Digital Signal Processing  
FD-SOI Fully Depleted Silicon-On-Insulator  
EO Electro-Optical