# Bandwidth-Based Wake-Up Radio Solution through IEEE 802.11 Technology
## 5 Wake-Up Radio System Evaluation  
In this section, we evaluate the proposed WuR system and compare the performance of the one bit per symbol and of the two bits per symbol WuC, considering legacy IEEE 802.11 transmitters. \begin{table}
\begin{tabular}{c c} \hline \hline
**Signal Bandwidth** & **Codification Scheme** \\ \hline
20 MHz & 00 \\
40 MHz & 01 \\
80 MHz & 11 \\
160 MHz & 10 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Codification scheme. Figure 10: (a) Signal level at filter output of the third chain of Figure 6, (b) BER at the output of the third chain of the WuRx of Figure 6, vs. distance, employing 80 MHz and 160 MHz signals. Again, we have used the Matlab software tool and the functions from the WLAN System Toolbox for the generation of IEEE 802.11 frames and their transmission through a communication channel, including multi-path and fading effects. In addition to propagation model B, also model F from TGn/ac [26] has been used, which is employed for large open indoor and outdoor scenarios. We consider a bit stream of 10,000 random bits for the one bit per symbol WuC and of 20,000 for the two bits per symbol WuC, thus, transmitting 10,000 IEEE 802.11 signals (i.e., WuC symbols) in both scenarios. Signals are generated according to the coding scheme described in Section 4. Obviously, IEEE 802.11n transmissions can only be employed for the one bit per symbol WuRx with 20 MHz and 40 MHz signal bandwidths since IEEE 802.11n does not support larger bandwidths. Moreover, note that, although the different IEEE 802.11 amendments (i.e., IEEE 802.11n/ac/ax) introduce some changes at the PHY, the generated signal for different bandwidths (i.e., 20, 40, 80, and 160 MHz) is read by the proposed WuRx of Section 4. Thus, independently of the specific PHY used at the WuTx, the WuR solution is suitable for the different amendments from IEEE 802.11n-2009 on, given that the spectral mask at different bandwidths is almost identical for all of them [23; 27; 28]. Recall that the WuRx is intended to detect energy over different bandwidths, which are common to all amendments operating in the 2.4 and 5 GHz ISM bands; that is, from IEEE 802.11n to IEEE 802.11 ax (both included). A transmission power of 1 W is considered at 5 GHz; therefore, we only show the evaluation at 5 GHz using an IEEE 802.11 ac WuTx. We take the different alternatives into account for our evaluation and show BER performance at WuRx output as a function of the distance between WuTx and WuRx in Figure 11a,b for propagation models B and F, respectively. The largest operational range (BER = 0), from 1 m to 18 m for model B and from 1 m to 50 m for model F, is achieved by the approach using one bit per symbol encoded with 20 MHz and 80 MHz signals. The scenario with one bit per symbol employing 20 MHz and 160 MHz signals shows the same performance as for the case including 20 MHz and 80 MHz signals and, thus, it has not been included in Figure 11. The system with two bits per symbol decreases the operational range (BER = 0) from a maximum distance of 18 m to 12 m for model B, and from a maximum of 50 m to 30 m for model F. On the other hand, it allows a higher bit rate (32.81 kbps in front of 16.14 kbps and 17.26 kbps, using one bit per symbol and IEEE 802.11 ac and IEEE 802.11n, respectively; 27.17 kbps in front of 13.58 kbps for IEEE 802.11 ax). The worst operational range (up to a maximum distance of around 10 m for model B, and up to a maximum of 20 m for model F) is achieved for one bit per symbol and signal bandwidths of 20 MHz and 40 MHz. Slope values are smoother for the approach with better performance (1 bit/symbol 20-80 MHz), i.e., larger operational range, as the wider bandwidth difference among signals eases the differentiation between them, thus presenting a lower error rate. On the opposite, slope values are steeper for worse approaches, i.e., those with shorter operational range, as the smaller bandwidth difference between signals conduct to high error rate in the differentiation process.