لخّصلي

In this study, the authors demonstrated the potential of V2V and V2I in a Het-Net environment with Wi-Fi, DSRC and LTE that guarantee the optimal utilization of available communication options and minimize the corresponding backhaul communication infrastructure requirements while considering connected vehicle application requirements.For a broad range of CVT applications (i.e., safety, mobility, environmental), a viable communication option should include V2V and V2I capable of utilizing a Het-Net optimally without losing connectivity while moving from one communication network to another.Field tests revealed that the message delivery time during the handoff was much higher than the CVT safety application latency requirement of 200 ms. However, Het-Net could provide supplementary connectivity for CVT safety applications to warn vehicles upstream about any safety hazardous conditions downstream, so that they can take proactive actions to avoid the problem locations.ns-3 simulation experiments with a larger number of connected vehicles, compared to the field tests, were conducted for a DSRC and LTE Het-Net scenario to complement and validate the findings from field tests that included a limited number of connected vehicles.The handoff between networks (Wi-Fi to LTE, DSRC to LTE and vice-versa) require several seconds to establish a connection and resume the data transfer, which means that Het-Net could not be used to support time sensitive safety applications.The performance of a CVT application using Het-Net depends on the availability of multiple wireless communication options, acceptable communication latency, data security, and reliability of timely message delivery.Consequently these networks must be reconfigurable for developing such a robust synchronized Het-Net.

In this study, the authors demonstrated the potential of V2V and V2I in a Het-Net environment with Wi-Fi, DSRC and LTE
that guarantee the optimal utilization of available communication options and minimize the corresponding backhaul
communication infrastructure requirements while considering connected vehicle application requirements. Existing CVT
architecture, such as CVRIA, suggests that seamless communication for V2V and V2I are required to utilize the full potential
of CVT applications. The performance of a CVT application using Het-Net depends on the availability of multiple wireless
communication options, acceptable communication latency, data security, and reliability of timely message delivery. For
a broad range of CVT applications (i.e., safety, mobility, environmental), a viable communication option should include
V2V and V2I capable of utilizing a Het-Net optimally without losing connectivity while moving from one communication
network to another. It will require a successful handoff from one wireless network to another in a Het-Net environment.
However, these different networks have not been designed for the seamless message transfer from one network to another
for moving nodes/vehicles. Consequently these networks must be reconfigurable for developing such a robust synchronized
Het-Net. The research detailed here is the first attempt in designing and evaluating such a network for CVT applications.
A long handoff time was observed due to the time required to activate the 802.11 link and the time required for the vehicle to associate with the RSU (i.e., access point) in LTE and Wi-Fi Het-Net scenario. Field test results revealed that Het-Nets
did not compromise the performance of the traffic data collection application studied in this research. Unlike safety applications, very low latency (200 ms) is not required for traffic data collection. Het-Nets provide additional connectivity beyond
DSRC range to collect traffic data for a larger traffic network, which is required for many CVT applications. The handoff
between networks (Wi-Fi to LTE, DSRC to LTE and vice-versa) require several seconds to establish a connection and resume
the data transfer, which means that Het-Net could not be used to support time sensitive safety applications. Field tests
revealed that the message delivery time during the handoff was much higher than the CVT safety application latency
requirement of 200 ms. However, Het-Net could provide supplementary connectivity for CVT safety applications to warn
vehicles upstream about any safety hazardous conditions downstream, so that they can take proactive actions to avoid
the problem locations. ns-3 simulation experiments with a larger number of connected vehicles, compared to the field tests,
were conducted for a DSRC and LTE Het-Net scenario to complement and validate the findings from field tests that included a
limited number of connected vehicles. Results from these ns-3 simulations were similar to the field experiment results. This
study is the first of its kind to evaluate the performance of Het-Net for a seamless V2I and V2V communication for CVT
applications. This application layer handoff method for Het-Net communication developed in this study can be adopted
in future Het-Net-supported connected vehicle applications. Examinations of the feasibility and performance of Het-Net
for a traffic data collection application and a collision warning application were the focus of this research