## 3 Literature Review and Related Work
### Fingerprinting-Based Positioning Implementing Fingerprint Images Processed Using CNNs
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Ref.** & **Year** & **Fingerprints** & **Discretized Positioning** & **CNN** & **Fingerprints** & **Side** \\  & & **Used** & **Area Size** & **Type** & **Image** & **Inform.** \\ \hline
[116] & 2020 & RSS & 1.6 m \(\times\) 1.6 m & 2D & Finger. arranged in a matrix & No \\ \hline
[117] & 2020 & RSS & 25 m \(\times\)25 m to 200 m \(\times\)200 m & 2D & Finger. arranged in a matrix & No \\ \hline
[118] & 2020 & RSS & 1.0 to 2.0 m [88] & 2D & Finger. arranged in a matrix & No \\ \hline
[119] & 2020 & RSS & 0.75 m \(\times\) 0.75 m & 2D & Finger. arranged in a matrix & No \\ \hline
[120] & 2020 & SNR & 0.3 m \(\times\) 0.3 m & 2D & Beam covariance matrix & Yes 32 \\ \hline
[121] & 2020 & Radio beams & From dataset; see [121] & 2D & Number of beams by time samples & (Yes) - \\ \hline
[122] & 2020 & Radio beams & From dataset; see [122] & 2D & Number of beams by time samples & (Yes) - \\ \hline
[123] & 2021 & CSI: amplitude differences & 1.0 m \(\times\) 1.0 m, 0.6 m \(\times\) 0.6 m, and 0.5 m \(\times\) 0.5 m & 2D & Finger. arranged in a matrix of 30 time samples & (Yes) 3 \\ \hline
[124] & 2021 & RSS & 38.0 m mean dist., outdoor & 2D & Finger. arranged in a matrix & No \\ \hline
[125] & 2021 & RSS & Bounding box with estimated position in 40 m \(\times\) 40 m area & 2D & Finger. arranged in a matrix & No \\ \hline
[126] & 2021 & RSS & Not specified & 2D & Finger. arranged in a matrix & No \\ \hline
[127] & 2021 & RSS and phase difference & 2.0 m \(\times\) 2.0 m & 2D & Finger. arranged in a matrix & No \\ \hline
[128] & 2021 & CSI & 1.0 m \(\times\) 1.0 m & 2D & Amplitude feature map & (Yes) 3 \\ \hline
[129] & 2021 & CSI: AoA, amplitude & 1.8 m \(\times\) path width & 2D & 30 subcarriers by 30 time samples & (Yes) 3 \\ \hline
[130] & 2021 & Geomagnetic & Not specified & 2D & Sequence of fingerprints arranged in a matrix & Yes 700 \\ \hline
[131] & 2021 & Geomagnetic & 0.6 m \(\times\) 0.6 m & 2D & Sequence of fingerprints arranged in a matrix & Yes 10 \\ \hline
[132] & 2021 & RSS & Ref. points spaced between & 2D & Finger. arranged in a matrix sorted by the spatial relationship of the access points & No \\ \hline
[133] & 2021 & CSI: amplitude & Not specified & 2D & Finger. arranged in a sub-window & Yes 16 \\ \hline
[134] & 2021 & RSS & 1.0 m \(\times\) 1.0 m, 1.5 m \(\times\) 1.5 m & 2D & Matrix of scaled diff. of fingerp. & No \\ \hline
[135] & 2021 & CSI: amplitude & Not specified & 2D & 30 subcarriers by 30 time samples & (Yes) 3 \\ \hline
[136] & 2021 & RSS & 2.0 m \(\times\) 2.0 m & 2D & Finger. arranged in a matrix & No \\ \hline
[137] & 2021 & RSS & Ref. points spaced at 0.5 m & 2D & Finger. arranged in a matrix of the topology of the access points & No \\ \hline
[138] & 2022 & RSS & Ref. points spaced at 1.0 m & 2D & Finger. arranged in a matrix of the time and frequency & No \\ \hline
[139] & 2022 & RSS & 5.0 m \(\times\) 5.0 m to 40.0 m & 2D & Finger. arranged in a matrix of the topology of the access points & No \\ \hline
[140] & 2022 & CSI: phase & 0.5 m \(\times\) 0.5 m & 2D & 30 subcarriers by 30 time samples & (Yes) 3 \\ \hline
[141] & 2022 & CSI: amplitude & 1.2 m \(\times\) 1.2 m & 2D & 30 subcarriers by 200 time samples & No \\ \hline
[142] & 2022 & RSS and other & 1.0 m \(\times\) 1.0 m & 2D & Four measurements by time sampl. & No \\ \hline
[143] & 2022 & RSS & 0.2 m \(\times\) 0.2 m & 2D & Matrix of vertical–horizontal beams & No \\ \hline
[144] & 2022 & RSS & 1.0 to 2.0 m [88] & 2D & Finger. arranged in a matrix & No \\ \hline
[145] & 2022 & RSS & According to [87] & 2D & Finger. arranged in a matrix & No \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._The discretized positioning area sizes or equivalent area sizes assumed from the given reference points for each article surveyed are listed in the table. These were reviewed in order to obtain an insight into the granularity or resolution of the discretized positioning area sizes used in the different scenarios and later compare them to the area sizes considered in our proposal.