## 5 Discussion  
The following four comparison schemes are considered in the simulation:  
* Scheme of this paper;
* C-Decision [22];
* SOLEN [9];
* GNN-RL [23];
* Random action. Firstly, the influence of feedback number on V2V link is considered. As shown in Figure 5, when the number of feedback is 3, the average total interference received by the high-priority link in this scheme is the smallest, obviously reflecting the advantage of priority, and the average total interference received by the ordinary link is also slightly lower than that received by C-Decision. Priority discrimination is implemented on the premise that the average performance (that is, the overall performance) does not degrade, or priority discrimination ensures fairness. Then, with the increase of the feedback number, the average total interference of each V2V link basically remains unchanged and is larger than the total interference of the feedback number 3. In summary, the number of feedback is set as 3 in the simulation. Table 2 lists the performance comparison of the four schemes when the number of feedback is 3 and there is no input noise and feedback noise. Input noise refers to the Gaussian white noise received by each V2V during local observation, and feedback noise refers to the noise generated when DNN's output is fed back to DQN's input. Because the last four schemes consider the links equally, they do not distinguish the priority links, so we treat the average rate as the priority link rate. For the scheme in this paper, the average total interference received by the high-priority link is significantly smaller than that received by the common link, that is, the priority link has a better information transmission environment, reflecting the advantage of priority. The average total interference received by the ordinary link is slightly lower than that of C-Decision, SOLEN scheme and GNN-RL scheme and better than that of random scheme. In addition, the average rate of the V2V link in this scheme is improved by about 2.12% compared with C-Decision, which is higher than the SOLEN scheme and obviously better than the GNN-RL scheme and random action scheme. Similarly, the average rate of the V2I link in this scheme increases by about  
Figure 5: Impact of feedback number on V2V links. 7.51% compared with C-Decision, slightly higher than the SOLEN scheme and higher than the GNN-RL scheme and random action scheme. In summary, the scheme presented in this paper obviously shows the advantage of priority and is superior to C-Decision, GNN-RL and random spectrum allocation schemes in performance. While the proposed scheme is only slightly better than the SOLEN scheme, the proposed scheme does not need to obtain the CSI of all links in the base station. The scheme in this paper has no such limitation. It indicates that the scheme in this paper is more suitable for the Internet of vehicles environment with urgent business needs in real life. Finally, we study the influence of input noise and feedback noise on priority-enabled schemes. As can be seen from Figure 6, with the increase of input noise, the average interference received by high-priority V2V links in this scheme rises gradually and tends to be stable when the input noise is greater than 10 dB, while the average total interference received by non-priority links basically remains unchanged. This indicates that the scheme with priority enabled when the input noise is low can obviously show the advantage of priority, and the advantage of priority link gradually decreases with the increase of input noise.