# Cross-Technology Interference-Aware Rate Adaptation in Time-Triggered Wireless Local Area Networks
## 3 CTI-Aware Rate Adaptation Framework
### CTI-Aware Rate Selection  
In this framework, we propose a CTI-aware rate selection algorithm that supports interference mitigation by utilizing CTI information (power estimates for each CTI signal type) derived from the CTI identification model. These algorithms are presented in Algorithms 1 and 2. Our approach has the advantage of not requiring separate communication protocols for devices using different wireless technologies, making it easy to apply to existing rate adaptation algorithms in WLANs. Specifically, Algorithm 1, measurement-based CARA (M-CARA), applies the CARA framework to an explicit rate adaptation method based on SINR measurements, and Algorithm 2, packet error-based CARA (P-CARA), applies the CARA framework to an implicit approach based on packet errors. ```
0: Number of STAs \(N\); slot duration \(T_{\text{slot}}\); signal identification period \(T_{\text{scan}}\). 0:\(MCS_{\text{SINR}}^{(k)}\) for each STA \(k\). Initialization: CTI projection table; \(MCS_{\text{SINR}}^{(k)}\) for all \(k=1,2,\ldots,N\). for slot index \(i=0\) to total number of slots do  Determine the STA \(k\) assigned to the \(i\)-th slot. Estimate the signal and noise power of STA \(k\) and update average values. if\(i\) mod \((T_{\text{scan}}/T_{\text{slot}})=0\)then  Identify CTI signals. if CTI signals are identified then  Update the CTI projection table. endif endif  Calculate SINR and derive \(MCS_{\text{SINR}}^{(k)}\) for STA \(k\)'s next transmission slot. Return \(MCS_{\text{SINR}}^{(k)}\). endfor
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**Algorithm 1** Measurement-based CTI-aware rate selection  
The MCS index can be sent to the STA via an MCS feedback message. The STA performs rate control based on the MCS index received from the AP, thereby mitigating interference from CTI in each transmission cycle. The main steps of this algorithm are as follows: (1) identify types of CTI signals every \(T_{\text{scan}}\) period; (2) if types of CTI signals are identified, predict the times of occurrence of interference based on their patterns in the time domain and update the CTI projection table; and (3) based on the CTI projection table, calculate the SINR reflecting the impact of CTI for the next cycle of the STA transmitted in the current \(T_{\text{slot}}\), and derive the MCS index accordingly. When calculating the SINR for a specific STA at the AP, the signal power and channel noise of that STA's signal are calculated using the preamble field. Table 2 is used to derive the MCS index based on the calculated SINR. The MCS index is selected according to the minimum SNR threshold required. The projection table is updated when a specific signal type is continuously identified, using the identified time intervals. The time resolution of the projection table is set to the same as the signal identification period \(T_{\text{scan}}\). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**MCS Index** & **Modulation** & **Coding** & **SNR Threshold** \\ \hline
0 & BPSK & 1/2 & 2 \\
1 & QPSK & 1/2 & 5 \\
2 & QPSK & 3/4 & 9 \\
3 & 16-QAM & 1/2 & 11 \\
4 & 16-QAM & 3/4 & 15 \\
5 & 64-QAM & 2/3 & 18 \\
6 & 64-QAM & 3/4 & 20 \\
7 & 64-QAM & 5/6 & 25 \\
8 & 256-QAM & 3/4 & 29 \\
9 & 256-QAM & 5/6 & 31 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: MCS index and SNR threshold. The P-CARA algorithm mitigates channel noise interference by adjusting the rate on the transmitter side based on ACK messages, while compensating for the impact of CTI using the CARA framework. ```
Number of STAs \(N\); slot duration \(T_{\text{slot}}\); signal identification period \(T_{\text{scan}}\); rate selection step \(m\). 0. \(flag_{\text{CTI}}^{(k)}\), \(\Delta MCS^{(k)}\) for each STA \(k\). Initialization: CTI projection table; set \(flag_{\text{CTI}}^{(k)}=\texttt{off}\); \(\Delta MCS^{(k)}=0\) for all \(k=1,2,\ldots,N\). for slot index \(i=0\) to total number of slots do if A packet is received from the STA using slot \(i\)then  Estimate the signal and noise power of the STA. Update the average signal and noise power values for the STA. Transmit an ACK message to the STA.