*9.4. Privacy and Traffic Optimization*

The majority of the research conducted for location privacy protection in VANETs is based on the pseudonyms' changing process. The design of the privacy scheme may have an impact on the performance of other fields of the VANETs. One consideration is the impact on communication protocols, high frequency of changing pseudonym improves privacy but creates complications for the routing protocols. It degrades the performance of communication protocols that may impact the packet delivery ratio. The impact of the pseudonym changing process discussed in [67] on the packet delivery ratio is as follows: if vehicles (nodes) change their pseudonyms after every five seconds, the packet delivery ratio is about 60% to the destination. If pseudonyms are changed after every 10 s, the successful packet delivery ratio is about above 75%, while increasing duration to 30 s successful delivery ratio becomes above 85%. However, the increasing duration for pseudonym changes will reduce the level of privacy. Thus, there should be a reasonable balance between privacy protection and traffic optimization.
