# A Bibliometric Analysis and Visualization of In-Vehicle Communication Protocols
## 5 Conclusions
### Limitations and Future Research Directions  
Although this study makes a substantial contribution to understanding trends in research on in-vehicle communication, several limitations should be acknowledged. First, the analysis relies exclusively on the Scopus database. While Scopus offers extensive global coverage and consistent indexing, it does not include content from other prominent repositories such as Web of Science, IEEE Xplore, or Google Scholar. This limitation may affect the completeness of author profiles, citation metrics, and journal representation--particularly in engineering-centric or regional domains.  
Second, the bibliometric techniques applied here--such as co-citation analysis, publication volume counts, and link strength measures--tend to favor highly cited and established scholars. As a result, the analysis may under-represent contributions from early-career researchers, emerging authors, and under-resourced institutions. This inherent bias in citation-based metrics could obscure novel or interdisciplinary work that has not yet accrued significant citation counts.  
To address these limitations, future studies could:  
* Incorporate alternative impact metrics, such as altmetrics, emerging author indices, and social media or preprint citation signals, which offer complementary perspectives on scholarly influence.
* Apply temporal citation normalization or field-weighted metrics to better highlight recent and impactful publications across disciplines.
* Use content-based approaches--such as full-text analysis, keyword embedding, and topic modeling--to uncover latent themes and early-stage research clusters beyond citation frequency.  
Additionally, broadening the data collection procedure to integrate multiple databases would yield a more holistic representation of global research activity. Combining scientific methods with content analysis or natural language processing (NLP) techniques could enhance the depth and nuance of thematic interpretation. Exploring white papers, industry reports, and patent data may also provide valuable insight into how academic findings translate into real-world applications.  
Finally, future research could benefit from examining the policy landscape shaping connected vehicle technologies--for instance, how national cybersecurity regulations and smart mobility frameworks influence scholarly output and funding. Together, these enhancements would further elevate the richness and inclusiveness of bibliometric inquiry in this fast-evolving domain.  
Conceptualization, I.H., M.J.C.S.R., C.S. and F.B.; methodology, F.B. and C.S.; investigation, I.H.; data curation, I.H.; writing--original draft preparation, I.H.; writing--review and editing, M.J.C.S.R., C.S. and F.B.; visualization, I.H.; supervision, M.J.C.S.R., C.S. and F.B.; project administration, M.J.C.S.R., C.S. and F.B.; funding acquisition, M.J.C.S.R., C.S. and F.B. All authors have read and agreed to the published version of the manuscript.  
This study was developed under the project A-MoVeR-\"Mobilizing agenda for the Development of Products & Systems towards an Intelligent and Green Mobility\", operation n.o 02/C05-i01.01/2022.PC646908627-00000069, approved under the terms of the call n.o 02/C05-i01/2022--Mobilizing Agendas for Business Innovation, financed by European funds provided to Portugal by the Recovery and Resilience Plan (RRP), in the scope of the European Recovery and Resilience Facility (RRF), framed in the Next Generation UE, for the period from 2021 to 2026.  
The raw data supporting the conclusions of this article will be made available by the authors on request.  
The authors declare no conflicts of interest.