# Enhancing Route Guidance with Integrated V2X Communication and Transportation Systems: A Review
## 4 V2X Communication Architecture
### Application of Communication Protocols in ITS  
Vehicular communications utilize several short, medium and long-range low-power wireless technologies developed and standardized over the years for the Internet of Things (IoT) applications. Standards are controlled and maintained by organizations such as IEEE, the Internet Engineering Task Force (IETF), International Telecommunication Union (ITU), Third Generation Partnership Project (3 GPP), Zigbee, and the LoRa Alliance [81]. Those standards vary in frequency bands and transmission distances. There has been a lot of investigations on whether various wireless technologies are appropriate for V2X communication or not. Several researchers have proposed medium- and long-range low-power wireless sensor technologies, including WiFi, Zigbee, BLE, and LoRa communication [99]. On the other hand, researchers have adopted various wireless technologies, including Wi-Max, IEEE 802.11p, IEEE 802.16e, as well as 3 GPP-LTE and 5G New Radio (NR) [100]. Using these technologies comes with various difficulties. To select a technology for V2X, it is crucial to consider the issues of communication such as latency, transmission range, throughput, and power consumption [98]. The transmission ranges of 4G cell and WiMAX towers, for instance, are around 50 km and 16 km, respectively [83]. Therefore, these technologies consume a lot of energy, and V2X communication is not a priority for their frequency bands. Additionally, as the range increases, each gateway is to communicate with a greater number of vehicles and forecast more routes, which would overburden the processing unit and produce more delays. ZigBee is a low-power wireless communication system that follows the IEEE 802.15.4 standard [25]. The technology uses multi-hop, mesh networking and low power consumption, which has increased in popularity for both commercial and residential purposes. It operates in the 915 MHz (America), 868 MHz (Europe), and 2.4 GHz (global), scientific, medical (ISM) band, and industrial with transmission ranges of 10-100 m. Therefore, in order to achieve the same lengths as other wireless technologies like LoRa or WiMAX, it uses multi-hop communications instead of D-D communication. However, ZigBee's multi-hop communication might result in greater latency and packet drops because of several data handovers [101]. ZigBee, however, is unable to support a heavy user load due to its Personal Area Network (PAN) foundation, which is one of its drawbacks. LoRa achieved a balance between data transmission rate and transmission range. With a data transmission rate of 300 bps-37.5 kbps, LoRa has a limited transmission range. Additionally, it is based on IEEE 802.15.4, a low-power communication standard. It enables wide area networks (WANs) via a LoRaWAN server, which is required by certain ITS applications. Such characteristics of LoRa make it appropriate for a more straightforward and efficient V2X communication that can consistently deliver data with little latency and energy requirement. LoRaWANo offers ubiquitous connectivity in indoor and outdoor applications with a raw maximum data rate of 27 kbps [102]. One drawback is that it has a relatively low throughput, which might have to restrict the amount of data that can be transmitted [83]. In urban settings, its transmission range is 2-5 km, but in a suburban environment with a clear line of sight, it can reach distances of up to 15 km [103]. Nevertheless, the very high speed offered by 3 GPP LTE and 5G NR cannot even permit streaming. This technology has the potential to provide automated traffic services and autonomous driving, as it offers faster throughput with lower latency. Further, various innovative technologies, like light detection and ranging (LiDAR), can be extensively utilized. Studies shows that LiDAR is sufficient for several V2X applications, including detecting and tracking pedestrians and vehicles [104]. An infrastructure-based LiDAR sensor approach for predicting multi-channel V2X communication performance has been proposed in [105].