# 3 GPP 5G V2X Error Correction Coding for Various Propagation Environments: A QoS Approach
## 6 Conclusions and Future Work  
V2X systems have been very popular in the research community in the last few years and attracted great interest both in the academic community and in the industry. Briefly, 3 GPP 5G V2X systems are quite demanding systems since they require low latency and very high reliability in high-density and high-mobility communication environments. Based on this reasoning, it is necessary to have a coding scheme that is sufficiently efficient to meet the reliability requirements of the communication system and at the same time be complexity efficient to meet the latency requirements set by the communication environment. In this article, we implement five different stochastic 5G V2X propagation models, namely, highway-LOS, highway-NLOSv, urban-LOS, urban-NLOS and urban-NLOSv. Based on these models, we investigate all the 4G-based and 5G-based coding schemes, i.e., BCJR, logBCJR, maxlogBCJR, SOVA, polar and LDPC, and examine their performance in terms of FER vs. SNR for 128-bit frames. From our simulation results, we prove the FER superiority of the BCJR-based algorithms. A 128-bit frame size was used as a representative sample of small-data frames to draw conclusions for small-frame 5G V2X services. In addition to the FER performance of the coding schemes, we thoroughly analyzed the impact of the velocity, channel state and traffic model on the V2X telecommunication systems and showed that a highway environment is more sensitive to traffic and channel changes. Additionally, we examined the 5G V2X QoS characteristics that were defined by 3 GPP and 5 GAA, i.e., reliability, power, range, vehicle speed, throughput, end-to-end latency, number of vehicles and vehicle density, and investigated their behavior for each QoS scenario, propagation model and coding scheme in order to derive the most efficient coding scheme for each QoS parameter. This approach and analysis are the novelty of this work, where all possible 3 GPP 5G V2X propagation models, all 4G and 5G coding schemes, as well as 3 GPP and VGAa QoS features, are combined in order to extract in-depth conclusions on the performance and QoS efficiency of the coding schemes. Our analysis shows that BCJR-based coding algorithms are the best choice for the reliability-based QoS parameters and that polar and SOVA are the best choices for the latency-based QoS parameters. Finally, we extracted and determined an overall QoS evaluation, and we concluded that polar and maxlogBCJR have the best overall QoS efficiency, although the optimal feature field differs for these two algorithms. This study is part of extensive research on the utilization of turbo coding in small-frame 5G V2X communications, in terms of FER performance and QoS efficiency. Thus, in future work, the behavior of FER vs. SNR performance as well as the QoS performance of the turbo codes in a dynamic communication system, where the communication model and channel state vary in time according to some probabilistic criteria, will be examined. In that way, we will investigate if turbo coding is a 5G-V2X-compatible coding solution in more realistic communication scenarios, where the channel state changes dynamically between LOS, NLOS and NLOSv and the traffic model changes in time between urban and highway in a real-time communication scenario. Furthermore, smaller V2X frame lengths can be investigated in order to investigate massive machine-type communication (mMTC)-compatible communications. Finally, our ultimate future objective is an extensive investigation of a holistic and dynamically reconfigurable coding scheme that uses FER performance and QoS features for choosing the most suitable decoder. Such a design could be supported by artificial intelligence principles, and trade-offs should be determined among performance, QoS and computational complexity. Conceptualization, D.C., C.C. and D.K. ; methodology, D.C., C.C. and D.K. ; software, D.C.; validation, D.C., C.C. and D.K. ; formal analysis, D.C., C.C. and D.K. ; investigation, D.C., C.C. and D.K. ; resources, D.C., C.C. and D.K.