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Table 1 Summary of key notations

From: Trajectory planning in UAV emergency networks with potential underlaying D2D communication based on K-means

Notations Definitions
N Number of DUs
K Number of initial clusters
H Flying height
M Number of SPs
\(R_{c}^{\mathrm{max}}\) Maximum coverage radius of UAV
\({\mathbf{w}}_{d}[n]\) Coordinates of the nth DU
\({\mathbf{w}}_{u}[m]\) Coordinates of the mth SP
\({\mathbf{w}}_{u}^{k}[m_{i}]\) Coordinates of the \(m_{i}\)th SP obtained during the clustering phase
\({\mathbf{w}}_{u}^{a}[m_{a}]\) Coordinates of the \(m_{a}\)thSP obtained during the supplementary phase
\({\mathbf{w}}_{d}^{c}[n_{c}]\) Coordinates of \(n_{c}\)-th DU that can be covered during the clustering phase
\({\mathbf{w}}_{d}^{\mathrm{unc}}[n_{\mathrm{unc}}]\) Coordinates of \(n_{\mathrm{unc}}\)-th DU that cannot be covered during the clustering phase
\(r_{i}^{k}\) Sum throughput of covered DU by UAV at \(w_{u}^{k}[i]\)
\(\rho _{e}\) Joint evaluation index
\(L_{\mathrm{sum}}\) Length of UAV’s trajectory