Fig. 5From: Leveraging MIMO-OFDM radio signals for device-free occupancy inference: system design and experimentsSpace-frequency correlation. a Frequency correlation \(r_{f_{2},\,f_{25}}^{\ell _{j}}\) versus all links. b Space correlation \(r_{\ell _{1},\ell _{9}}^{f_{i}}\) versus all sub-carriersBack to article page