# An Adaptive Scheduling Mechanism Optimized for V2N Communications over Future Cellular Networks
## 2 Scheduling Algorithms
### Proposed Schedulers for 5G and Beyond including V2X Communications  
Scheduling for future 5G and beyond systems is a well-investigated topic. An overview of the state-of-the-art methods for the various scheduling schemes can be found in [11]. The indicated survey paper reviews the development of scheduling algorithms through the literature and classifies them into four primary categories, based on (i) the various QoS metrics used, (ii) the machine-learning approach adopted, (iii) the performance goals, and (iv) the suitability to achieve 5G performance requirements for different UCs requirements. The paper analyzes the suitability of each scheduling algorithm for different 5G families of UCs eMBB, Ultra Reliable Low Latency Communications-URLLC, and massive Machine Type Communications-mMTC). Notably, all scheduling mechanisms analyzed in this paper for URLLC (related to V2X communications for safety) are QoS unaware except for two of them. The authors of [12] have designed such an algorithm, but it is targeted at LTE networks and requires many parameters that may increase the computation time. Thus, it is challenging to implement. Similarly, the solution in [13] demonstrates high computation times and requires constant training, which is resource-consuming. The paper's authors provide an analytical model and simulations for a limited number of users (i.e., 10) using generic traffic patterns (i.e., CBR and VBR). In [14], a network slice-aware RAN radio resource allocation mechanism for the dynamic multiplexing of enhanced mobile broadband (eMBB) and URLLC users is proposed. The proposed scheme allocates RBs based on the signal-to-noise ratio (SNR) multiplied by a normalized queue state parameter, targeting to avoid buffer data accumulation. However, the analysis is performed from a slice-level granularity, missing to consider specific UE traffic flows. The authors of [15] note the lack of research efforts that address resource allocation under different requirements from multiple V2X applications. The authors in [15] present another resource allocation algorithm for 5G-V2X communications that selects the appropriate 5G numerology based on the V2X application requirements and the channel conditions. V2X applications are categorized as safety and non-safety-related applications. Resources are allocated prioritizing the safety applications first. The performance of the scheme is analyzed through simulations and provides interesting results. However, these results come from considering 50 vehicles running a V2V (and not V2N) safety application, which is essentially the exchange of Cooperative Awareness Messages (CAMs). Among them, a subset of 20 vehicles run one type of non-safety application, namely a videoconference stream. Although the strategy of promoting safety against non-safety applications during the allocation of resources shares similar principles to SOVANET, the use of non realistic data traffic patterns for autonomous driving applications needs to be considered to objectively evaluate the provided results. In [16], a new scheduling algorithm is introduced, based on a Block Resource Allocation policy in a Non-Orthogonal Multiple Access (NOMA) way, so that a well-defined set of users is selected to use the same RB. To identify such sets, the scheme considers metrics related to the distance and the equity between users. The objective is to maximize the system throughput equity among the number of served users and to minimize the packet error rates. A multi-user scheduling algorithm is proposed in [17] for ultra-massive MIMO systems in 6G V2X scenarios. The problem tackled is to provide stable and reliable wireless link quality and improve the channel gain in vehicles moving at high speeds. The authors suggest using a multi-user scheduling algorithm based on block diagonalization precoding. This paper focuses mainly on bit error rate performance and spectrum efficiency and does not distinguish between different V2X services.