# Analysis of the Scalability of UWB Indoor Localization Solutions for High User Densities
## 3 UWB Regulations and PHY Considerations
### Detect And Avoid (DAA)  
Detect And Avoid is an active mitigation technique, which means that any decision is made upon measurements from the environment. More precisely, it is based on the identification of other radio signals and, if any transmitting device (victim system) is sensed, the TX power is lowered down  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Frequency (GHz)**} & \multicolumn{2}{c}{**Maximum Mean Power Spectral Density (e.i.r.p.) (dBm/MHz)**} \\ \cline{2-4}  & **LT1** & **LT2** & **LEAS** \\ \hline \(f\leq 1.6\) & \(-90\) & \(-90\) & \(-90\) \\ \(1.6<f\leq 2.7\) & \(-85\) & \(-85\) & \(-85\) \\ \(2.7<f\leq 3.1\) & \(-70\) & \(-70\) & \(-70\) \\ \(3.1<f\leq 3.4\) & \(-70\) & (-41.3 with DAA) 1  & \((-41.3\,1^{2}\) \\ \(3.4<f\leq 3.8\) & \(-80\) & (see note 1 for fixed outdoor) & \(-21.3\) 1 \\ \(3.8<f\leq 4.2\) & \(-70\) & (-41.3\(\,1^{2}\) \\ \(4.8<f\leq 6\) & \(-70\) & (see note 1 and 3 for outdoor) & \(-41.3\) 1 \\ \(6<f\leq 8.5\) & \(-41.3\) & \(-70\) & \(-70\) \\ \(8.5<f\leq 9\) & \(-64\) & \(-70\) & \(-70\) \\ \(9<f\leq 10.6\) & \(-65\) & \(-70\) & \(-70\) \\ \(f>\)10.6 & \(-85\) & \(-85\) & \(-85\) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Maximum mean power spectral density (dBm/MHz) for UWB systems.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Frequency (GHz)**} & \multicolumn{2}{c}{**Maximum Peak Power Spectral Density (e.i.r.p.) (dBm in 50 MHz)**} \\ \cline{2-4}  & **LT1** & **LT2** & **LEAS** \\ \hline \(f\leq 1.6\) & \(-50\) & \(-50\) & \(-50\) \\ \(1.6<f\leq 2.7\) & \(-45\) & \(-45\) & \(-45\) \\ \(2.7<f\leq 3.1\) & \(-36\) & \(-36\) & \(-36\) \\ \(3.1<f\leq 3.4\) & \(-36\) & (0 with DAA) 1  & (0 with DAA) 1  \\ \(3.4<f\leq 3.8\) & \(-40\) & (see note 1 for fixed outdoor) & \(20\) 1  \\ \(3.8<f\leq 4.2\) & \(-60\) & (see note 1 and 3 for outdoor) & \(20\) 1  \\ \(4.2<f\leq 4.8\) & \(-60\) & (see note 1 and 3 for outdoor) & \(20\) 1  \\ \(4.2<f\leq 4.8\) & \(-60\) & (see note 1 and 3 for outdoor) & \(20\) 1  \\ \(4.2<f\leq 4.8\) & \(-60\) & (see note 1 and 3 for outdoor) & \(20\) 1  \\ \(4.2<f\leq 4.8\) & \(-60\) & (see note 1 and 3 for outdoor) & \(0\) 1  \\ \(4.8<f\leq 6\) & \(-30\) & \(-30\) & \(-30\) \\ \(6<f\leq 8.5\) & \(0\) & \(-30\) & \(-30\) \\ \(8.5<f\leq 9\) & \(-25\) & \(-70\) & \(-30\) \\ \(9<f\leq 10.6\) & \(-25\) & \(-30\) & \(-30\) \\ \(f>10.6\) & \(-45\) & \(-45\) & \(-45\) \\ \hline \hline \end{tabular}
\end{table}
Table 3: Maximum peak power (dBm in 50 MHz) for UWB systems.  
to a non-interfering level or alternatively, the transmission is deferred until the victim disappears. As outlined in Tables 2 and 3, a maximum mean e.i.r.p density of \(-41.3\) dBm/MHz and a maximum peak e.i.r.p. of 0 dBm are allowed in the 3.1 GHz-4.8 GHz and 8.5 GHz-9 GHz bands when using DAA but the main criteria to determine which power level can be used, is the distance to the victim system. DAA adopts a zone model wherein different distances correspond to different zones. The main principle is that by sensing the channel it is possible to estimate the distance to the victim system by measuring the power level. The area around the victim is divided in discrete zones and the transmission power is modulated accordingly, e.g., in the last zone, the device can operate without restriction. In a basic model with two zones, i.e., non interference zone and free zone, the signal received from the victim system is compared with a threshold level  
\[D_{thresh}=P_{TX\_victim}-I \tag{1}\]  
where \(P_{TX\_victim}\) is the transmit power of the victim system and \(I\) is the minimum needed isolation.  
Another possibility to mitigate the effect of interfering systems, is to use passive mitigation techniques such as Low Duty Cycle, which is described in the next paragraph.