# Extending the Coverage of IEEE 802.15.4z HRP UWB Ranging
## 2 UWB Local Regulations and UWB Pulse Characteristics  
UWB means using ultra-wideband technology, and the local regulations in Table 2 must be applied worldwide. As shown in Table 2, UWB involves frequency-related regulations, such as the frequency band or frequency bandwidth used, and output power, such as average power and peak power. Among the local regulations in Table 2, the output power regulations are applied globally; that is, the output power of the UWB transmitter must satisfy both 1 the average power spectral density (PSD) of \(-\)41.3 dBm/MHz at 1 ms and 2 the peak PSD of 0 dBm/50 MHz. This is explained in Figure 1. Assuming that one pulse has a bandwidth of 500 MHz, the pulse width is approximately 2 ns. The peak power of one 2-ns pulse must be less than 10 dBm/500 MHz according to 2 the peak PSD regulation. In addition, when there are multiple pulses during a 1-ms period, the average power, which is the accumulated effect of these pulses, must be less than \(-\)14.3 dBm/500 MHz according to 1 the average PSD regulation. \begin{table}
\begin{tabular}{c c} \hline \hline  & **Local Regulation** \\ \hline Frequency & 3.1–10.6 GHz 1  \\ Average power & \(-\)41.3 dBm/MHz@1 ms \\ Peak power & 0 dBm/50 MHz \({}^{\vartriangle}\) \\ Bandwidth & More than 450 MHz (1 MHz RBW, 10 dB bandwidth) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Local regulation for UWB worldwide. The reason for having two criteria is because the average power changes depending on the number of pulses. For example, if there is only one pulse with a bandwidth of 500 MHz per 1 ms, as shown in Figure 1a, then the peak power will have a rather large value of 42.7 dBm/500 MHz under 1 the average PSD regulation. This means that although the average output is small, the peak power is quite large, and thus it can interfere with other wireless devices for a short period of time. Therefore, according to local regulation 2, the peak power must be limited to 10 dBm or less even if there is one pulse. Accordingly, the case where both local regulations are satisfied is when the peak power is 10 dBm and the number of pulses is 1862 for a UWB pulse with a bandwidth of 500 MHz, as shown in Figure 1b. In this case, the average power becomes \(-14.3\) dBm/500 MHz, and thus both local regulations 1 and 2 are satisfied. Regarding spectral emissions, the IEEE 802.15.4z standard does not specify a mandatory adjacent channel power rate (ACPR) or spectral mask requirements, unlike narrowband communication standards. Therefore, our link-budget optimization focuses solely on complying with the average and peak power constraints defined by worldwide UWB regulations. Now, based on this local regulation for the output power, let us find out the number of pulses per 1 ms, peak power, and average power when a UWB device is used for communication or radar. First, since UWB radar measures the distance by using the time difference between the transmitted pulse and the pulse backscattered from the target, the pulse repetition frequency (PRF) is determined by the maximum measurement distance. For example, Novelda's UWB x4 module, a representative UWB radar module, uses a pulse with a bandwidth of 1.5 GHz (pulse width of approximately 0.67 ns) and waits for the pulse for 65.8 ns after transmitting the pulse [30]. When this time is converted into a distance, it is 9.87 m. Since the actual operating range of Novelda's UWB radar is only 1-2 m, it is possible to use more pulses, but in this case, the average power exceeds \(-14.3\) dBm/MHz and thus cannot be used; that is, the pulse number and peak power of the UWB radar are determined by local regulations 1 and 2, as shown in Figure 2a. Next, the currently commercialized IEEE 802.15.4z-based UWB communication method is HRP UWB with a relatively high PRF [7]. In Figure 1, when the peak power is 10 dBm, the number of pulses with a bandwidth of 500 MHz possible for 1 ms is 1862, and using more pulses than this number is called HRP UWB.