# A Non-WSSUS Channel Simulator for V2X Communication Systems
## 7 Conclusions  
This article presents a simulator that allows reproducing non-WSUS multipath fading channels under arbitrary isotropic or non-isotropic scattering conditions. Furthermore, the proposed simulator allows velocity variations and non-linear trajectories of the MSs. This simulator is based on the combination of the SOC method and the Monte Carlo principle, and it can be adapted to the multicarrier transmission parameters of the schemes specified in the IEEE 802.11p and LTE-V2X standards. Therefore, the channel simulator can be used to evaluate the performance of V2X communication systems based on those standards for different scenarios of interest. In this paper, the proposed channel simulator was applied to the BER performance analysis of two channel estimation techniques for DSRC transceivers based on the IEEE 802.11p standard, namely the LS estimator and the STA estimator. Our proposal was evaluated in three propagating scenarios for road safety applications. The simulation results showed that the performance of the LS estimator largely depended on the motion profiles of the MSs, the frame length, and the scattering scenario. This is due to the underlying channel estimation procedure since the estimate is computed using only the two initial training symbols and is maintained constant until the end of the frame. Therefore, the estimation can lose its validity over time with the channel variations. An important observation of the LS estimator is that neither the non-stationarities of the channel, nor the acceleration of the MSs have a significant impact on its BER performance. Regarding the STA technique, the non-stationarities of the channel affect its performance, in addition to the losses caused by high mobility conditions, frame length, or scattering scenario. Therefore, in this work, we propose a variant of the STA technique as an alternative method for the estimation of non-WSUS channels in DSRC systems. The modified STA scheme improves its estimation performance remarkably for Eb/No levels greater than 15 dB, while for smaller values, its performance worsens since the dynamic updates are affected by the high level of noise. This variant of the STA technique is an option that must be analyzed in greater detail for its possible implementation in DSRC systems. In addition, new estimation techniques are necessary to  
Figure 11: System performance by considering the modified STA technique with different frame lengths, initial speeds of \(v_{T}=v_{R}=40\) km/h, and acceleration components of \(a_{T}=a_{R}=20\) m/s\({}^{2}\) for Scenario I.  
deal with the inherent non-stationarities that are found in vehicular channels. In this sense, the simulation framework presented here can be used as a reference for the evaluation of new transmission schemes for a V2X communication system under arbitrary scattering and mobility conditions.  
Conceptualization, J.J.J.-R., C.A.G.-V., C.A.G., J.M.L.-R., D.U.C.-D., and R.V.; methodology, J.J.-R., C.A.G.-V., and C.A.G.; software, J.J.J.-R. and C.A.G.-V.; validation, C.A.G., J.M.L.-R., D.U.C.-D., and R.V.; formal analysis, J.J.-R., C.A.G.-V., C.A.G., J.M.L.-R., D.U.C.-D., and R.V.; investigation, J.J.-R. and C.A.G.-V.; resources, J.J.J.-R., C.A.G., J.M.L.-R., D.U.C.-D., and R.V.; writing, original draft preparation, J.J.J.-R., C.A.G.-V., and C.A.G.; writing, review and editing, J.M.L.-R., D.U.C.-D., and R.V.; supervision, C.A.G.; project administration, J.J.J.-R., C.A.G., J.M.L.-R., and D.U.C.-D.; funding acquisition, J.J.J.-R., C.A.G., J.M.L.-R., D.U.C.-D., and R.V. All authors read and agreed to the published version of the manuscript.  
This research was funded by CONACYT Grant Number 254637 and by PRODEP Grant Number 511-6/2019-8024 (Folio:UASLP-PTC-642).  
The authors declare no conflict of interest.