# Implementation of a Fast Link Rate Adaptation Algorithm for WLAN Systems
## 6 Discussion and Conclusions
For example, [45] showed that SampleRate in [10] achieved a much lower throughput than the LA based on the effective SNR LQM. The proposed LA algorithm in our paper is based on the most accurate LQM, subcarrier SNR--MI, and also based on the adaptive mapping such that the algorithm is robust to mapping table errors and channel variations. Furthermore, it can attain above 94% of the theoretical max rate under fast fading as well, as was previously underscored in Table 2. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Throughput [Mbps] (Normalized Rate)**} & \multicolumn{5}{c}{**Normalized Doppler**} \\ \cline{2-6}  & **1 m** & **5 m** & **10 m** & **30 m** \\ \hline \multirow{2}{*}{\begin{tabular}{c} ARF \\ (Normalized Rate) \\ \end{tabular} } & 32 & 31 & 28 & 24 \\  & (0.94) & (0.90) & (0.82) & (0.70) \\ \hline \multirow{2}{*}{\begin{tabular}{c} PBLA \\ (Normalized Rate) \\ \end{tabular} } & 15.0 & 17.7 & 18.3 & 18.1 \\  & (0.44) & (0.51) & (0.54) & (0.53) \\ \hline \multirow{4}{*}{\
\begin{tabular}{c} APBLA \\ (Normalized Rate) \\ \end{tabular} } & ACK offset (dB) & 32 & 32.3 & 32.1 & 32.2 \\  & 0.01 & (0.94) & (0.94) & (0.94) & (0.94) \\ \cline{2-6}  & ACK offset (dB) & 31.3 & 32.6 & 32.5 & 32.8 \\  & 0.03 & (0.92) & (0.95) & (0.95) & (0.96) \\ \cline{2-6}  & ACK offset (dB) & 22.1 & 26.8 & 27.7 & 30.6 \\  & 0.1 & (0.65) & (0.78) & (0.81) & (0.89) \\ \cline{2-6}  & ACK offset (dB) & 15.8 & 19.0 & 19.5 & 21.0 \\  & 0.3 & (0.46) & (0.55) & (0.57) & (0.61) \\ \hline \multirow{2}{*}{
\begin{tabular}{c} Theoretical max. rate \\ (Normalized rate) \\ \end{tabular} } & 34.0 & 34.4 & 34.1 & 34.3 \\  & (1.00) & (1.00) & (1.00) & (1.00) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Performance comparison table. The proposed algorithm, APBLA, is associated with rate adjustment through the modulation and coding scheme. Power control and antenna selection in MIMO are not associated since the target system assumed is a \(1\times 1\) wireless local area network chip with no null data packet or sounding. A fast link adaptation algorithm to maximize the throughput with preamble-based MMI calculation supplemented by the ACK mechanism to adaptively adjust the SNR offset is proposed, simulated, implemented, and tested in this paper. As additional remarks, the requirements imposed on the RF chain to guarantee the throughput gain of APBLA compared with ARF are that the RX RF chain should exhibit little RF gain variation from packet to packet, and also the SNR mismatch from the RF gain mismatch between the TX RF and the RX RF should be all but time invariant, albeit this mismatch between TX and RX can be compensated for by means of the SNR offset employed by APBLA. Conceptualization, C.S.P. ; data curation, S.P. ; formal analysis, S.P. ; funding acquisition, C.S.P. ; investigation, S.P. ; methodology, S.P. ; project administration, C.S.P. ; resources, S.P. ; software, C.S.P. ; supervision, S.P. ; validation, C.S.P. ; visualization, C.S.P. ; writing--original draft preparation, C.S.P. ; writing--review and editing, S.P. All authors have read and agreed to the published version of the manuscript. This paper was supported by Konkuk University in 2018. Not applicable. No new data were created or analyzed in this study. Data sharing is not applicable to this article. The authors declare no conflict of interest.