# Evolution of V2X Communication and Integration of Blockchain for Security Enhancements
## 3 Evolution of V2X Technologies
### Evolution of Cellular V2X  
The incorporation of a mobile network provider for V2N will facilitate the use of frequencies beyond ITS, with high service quality in low bands, and millimeter wave in 5G. It also provides low latency wide area network support for assisted driving. The introduction of NR V2X is not to replace the C-V2X technology that has already been standardized and it serves as a roadmap to commercial deployments. Its aim is to provide support and ensure all V2X applications in C-V2X efficiently. C-V2X and NR V2X are expected to coexist in the same geographic region where new vehicles will have both C-V2X and NR V2X functionality. For this, NR V2X must be able to support not only advanced V2X applications, but also basic safety applications provided by current C-V2X. The NR V2X is designed to support V2X applications that involve different levels and requirements of latency, reliability, and throughput. Table 4 gives the summary of advancements in 5G NR over LTE. Although some of these use cases require periodic traffic transmission, a substantial number of NR V2X use cases are based on efficient aperiodic transmission of messages [15]. Some of the key features and mechanisms of NR V2X are as follows:  
1. NR V2X Sidelink Modes: NR V2X defines two side link modes similar to C-V2X. The NR V2X sidelink mode 1 specifies mechanisms, which allows direct vehicle interactions within the coverage of gNodeB. On the other hand, NR V2X side link mode 2 facilitates direct vehicular communications in the out-of-coverage situation. 2. Unicast, Groupcast and Broadcast: in Rel.16, NR V2X supports sidelink unicast, groupcast, and broadcast depending upon the scenarios, such as in-coverage, out of coverage, and partial coverage scenarios. For illustration, a transmitting vehicular node that has a single receiver associated with it can transmit in unicast transmission. A vehicle platoon leader can communicate with other platoon member nodes based on groupcast transmission. 3. NR Numerologies: a main feature included in 3 GPP Rel.15 is the provision of adjustable numerologies. In comparison to a single spacing of the sub-carrier used in LTE, NR embraces various spacings in the sub-carrier, which are multiples of the LTE sub-carrier spacing. The numerology for NR is configured to work with both sub-6 GHz bands and mmWave bands. This is developed by means of multiple numerologies that are formed by the scaling of a fundamental subcarrier spacing (SCS). A scalable OFDM numerology is an improvement introduced in NR, allowing for choice between different subcarrier spacing from 15 KHz up to 480 KHz. The slot length in accordance with these numerologies often varies from 1 ms to 0.031 ms.
* Slot, Mini-slot, and Multi-slot Scheduling: in LTE, the transmission time is closely coupled to the sub frame duration, i.e., all UEs typically communicate for a duration of 1 subframe (1 msec). Besides this, if the user has only a limited amount of data to transmit, which can be accommodated in less than 14 OFDM symbols. It is inefficient to reserve the entire slot for its transmission. In NR V2X, a mini-slot solution is furnished to transfer data using only two, four, or seven OFDM symbols without any slot limits. In addition, slot aggregation (i.e., adding two or more slots to create a multi-slot) would be provided in NR V2X to account for use-cases that need the sharing of large packets. * Channel Coding: as channel coding has a major effect on the reliability, performance and throughput of wireless systems, more effective and consistent coding methods are implemented. The LTE turbo codes are substituted by LDPC coding for data channel and LTE convolution codes are substituted by Cyclical Redundancy Check (CRC) assisted polar codes for the control channel in NR V2X. * PHY layer Improvements: NR V2X will provide several other PHY layer improvements, most of which are derived from 5G NR. These involve the use of LDPC coding, higher order MCS like 64-QAM, and a dynamic number of Demodulation Reference Signal (DMRS) symbols per slot.