# Effective PSCCH Searching for 5G-NR V2X Sidelink Communications
## 3 Proposed Effective PSCCH Searching
### Proposed Effective PSCCH Searching Based on Correlation
As expected, the correlation-based algorithm is better for high SNR regime, when compared with the correspondent Blind algorithm result. In the high SNR regime, we have for \(N_{RB}^{SL}=50\), a total runtime \(T_{1}=0.9\,\mathrm{s}\), and \(T_{2}=0.4\,\mathrm{s}\), which are approximately the same values as the ones obtained in Section 3.4, and for \(N_{RB}^{SL}=100\), we have \(T_{1}=3.0\,\mathrm{s}\) and \(T_{2}=1.6\,\mathrm{s}\). Therefore, in both cases the runtime savings were considerable. Finally, Figure 9 shows the same results of Figure 8, but in a normalized way to the highest time, so that we can analyze the results without these being associated with a specific CPU. In the high SNR zone, the gap for \(N_{RB}^{SL}=50\) is \(30.8\%\), while for \(N_{RB}^{SL}=100\) it is \(26.9\%\). This means that the proposed correlation-based algorithm, even though it continues to show a clear improvement over the Blind algorithm, lost some effectiveness by increasing the \(N_{RB}^{SL}\). This is associated with the fact that the bandwidth is greater, and that more samples are being processed in calculating the correlations. Figure 8: Average time for PSCCH search/decoding (seconds). Figure 9: Normalized average time for PSCCH search/decoding (%). ## 5 Conclusions

In this paper, we developed an effective PSCCH searching algorithm for 5G-NR V2X sidelink communications. In the proposed approach, we firstly computed all the correlations between the received signal and the PSCCH DMRS, and the remaining conventional processing to decode the PSCCH was only performed over the subchannels with higher correlation. The Proposed algorithm was compared with the conventional Blind algorithm that ensured the best possible performance in terms of PSCCH detection. The results showed that the proposed algorithm achieves the same performance in terms of SCI BLER and throughput, but with a much shorter runtime. For \(N_{RB}^{SL}=50\), the runtime of the Proposed algorithm was less than half of the Blind algorithm, which is an important improvement because the PSCCH detection and decoding have a very significant weight in the overall processing of the receiver. Furthermore, the average number of attempts to decode the PSCCH always tends to be one for high SNR, regardless of bandwidth. Thus, the proposed PSCCH searching algorithm is efficient for very high bandwidths, which are expected in 5G-NR communications. However, it would be interesting in future work to reduce the runtime in the calculation of correlations, which has significant weight in the Proposed algorithm. Finally, the Proposed algorithm could clearly replace the blind approaches for PSCCH searching in all schemes presented in [15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26]. Therefore, it could be an interesting approach for real-time systems, since it ensures a significant reduction of runtime and it is compatible with several schemes proposed in the literature. Investigation, J.D. and R.M. ; Supervision, A.S., P.M. and R.M. ; Validation, A.S., P.M. and R.M. ; Writing--original draft, J.D. and R.M. ; Writing--review and editing, A.S. and P.M. All authors have read and agreed to the published version of the manuscript. This work was financially supported by Fundo European de Desenvolvimento Regional (FEDER) through the POCI-01-0247-FEDER-046962 (5 GAUTO) and by FCT/MCTES through national funds and when applicable co-funded EU funds under the project UIDB/50008/2020-UIDP/50008/2020. The authors declare no conflict of interest. +++ ==WARNING: Truncated because of repetitions==
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