# Narrowband Internet-of-Things to Enhance the Vehicular Communications Performance
## 2 Modified V2V Benchmark  
This section will introduce the V2V benchmark based on LTE wireless infrastructure. It consists of a clustering topology that is used to enhance both the connectivity and the transmission data rate among the vehicles. Moreover, it covers the proposition of using the full-duplexing process and the MIMO deployment structure. Then, it describes the modification of the proposed benchmark based on the W-DFT process and the use of the Harmonic Wavelets (HW). Figure 1 depicts the V2V benchmark for N-moving vehicles based on LTE structure. It is clearly shown that there are two scenarios: V2V communications-based Ad-Hoc and communications through the LTE infrastructure. In this benchmark, N vehicles communicate with each other under the IEEE802.11 p protocol through one node called cluster's head (CH). Previously in our published work [19], the performance of the communication's link through CH has been studied based on two factors, namely power management, and link reliability. Accordingly, our new benchmark will be based on a pre-checked reclustering algorithm. This is clearly depicted in Figure 1.  
To fulfill the requirements of the benchmark in Figure 1, both the physical layer and medium access control layers are modified to include the OFDM transceiver with 52 orthogonal subcarriers-inverse fast Fourier-transform (IFFT) stage, 2/3 convolutional encoder stage, and a 16-APSK modulation stage. In each transceiver, multiple antenna deployment is introduced to combat the radio channel effect. Each e-Node B (e-NB) in the LTE structure can realize the process of the communications among vehicles; the communicating process under the V2V system. In each moving node (vehicle), there will be one transmitting link and four receiving links. Therefore, the SPS technique can easily schedule this process without affecting the reliability of the communication links. It controls the whole process based on the persisting time, where the starting of a new process is assigned with a zero time [8]. The vehicle's size is a considerable factor that must be taken into consideration to maximize the benefits of the full-duplex scenario. Figure 1: V2V benchmark for N moving vehicles based on LTE structure. Accordingly, the antennas can be easily accommodated in large vehicles' bodies to fit the self-interference proposition compared to large-scale-propagated transmitted signals. Therefore, the used self-interference cancellation process implies the use of a full-duplexing utilization scenario. This scenario enhances the link reliability by efficient spectrum utilization and reducing the implementation complexity. Therefore, it is a possible candidate for use in narrowband communications [21]. The antenna's deployment is clearly depicted in Figure 2. This deployment enhances the link reliability based on the spatial multiplexing MIMO technique. In this proposition, the uncorrelated receiving links have been attained by making use of the resultant phase differences between vehicles. In this deployment shown in Figure 2, another proposition should be considered; the channel must be modeled to fit the short-range communications. This proposition is made due to the dynamic vehicle's positions. Accordingly, n-dimensional random Gaussian variables are used as four rows describing the receiving antennas and one column as one transmitting antenna. This channel is modeled based on the mmWaves model and considered as a uniform linear array as expressed mathematically in [23] as:  
\[\mathbb{C}(f)=\sum_{l=1}^{4}g_{l}\times r_{ULA}\times\left((t_{ULA})^{*}\right) ^{T}\times e^{-\frac{2\pi\tau_{l}}{\gamma_{l}}} \tag{1}\]  
In this expression, each specific path has a complex gain denoted by \(g\), the angles of arrivals and departures have been defined by \(r_{ULA}\) and \(t_{ULA}\), respectively. A transposed conjugated mathematical process is defined as \(\left((. )^{*}\right)^{T}\), the delay and the period of each path are given by \(\tau\) and \(T\), respectively.