# Beam-Hopping-Based Resource Allocation in Integrated Satellite-Terrestrial Networks
## 6 Simulation Results
### Simulation Results for MWSC  
To evaluate the performance of the proposed resource allocation schemes for MWSC, the following schemes are used as the baselines in the simulations:  
* The resource allocation scheme aiming at maximizing the total capacity of the satellite system (MTCS) [23]. The satellite allocates the time slots according to the requested capacity of the satellite terminals, and the terrestrial BSs outside the dynamical protection zones can perform transmission. The terrestrial BSs can determine whether they are located in the dynamical protection zones by receiving the resource allocation results broadcasted by the satellite or by the spectrum sensing results. * The random resource allocation (RRA) scheme. The satellite randomly selects \(N_{b}\) from \(N_{sat}\) satellite terminals to provide services in each time slot [21], and the terrestrial BSs outside the dynamical protection zones can perform transmission. * The dedicated resource allocation (DRA) scheme. Dedicated frequency bands are allocated to the satellite system and the terrestrial systems, respectively. The bandwidth of the dedicated frequency band is equal to half of the full transmission bandwidth. The MTCS scheme is adopted in the satellite system, and the terrestrial BSs can perform transmission continuously. Figure 2 depicts the spectrum efficiency of the ISTN as a function of the average total requested capacity of the satellite system in gigabits per second (Gbps). The average total requested capacity of the satellite system is the sum of the average requested capacity of each satellite terminal, and the average minimum required capacity of each terrestrial system is 650 megabits per second (Mbps). The proposed optimal algorithm and greedy algorithm outperform the other schemes since they consider the capacity requirements of both the satellite and terrestrial systems. The performance of the greedy algorithm is almost the same as that of the optimal algorithm when the average requested capacity is relatively low, and it is a bit lower than that of the optimal algorithm with the increase of the requested capacity. The MTCS scheme cannot achieve the optimum spectrum efficiency in ISTN since the capacity requirements of the terrestrial systems are not considered. The RRA scheme is unable to flexibly schedule the resources according to the capacity requirements, so its performance is relatively low. When the satellite and terrestrial systems use the dedicated frequency band with half of the bandwidth, the spectrum efficiency of the ISTN degrades significantly, which verifies the effectiveness of the spectrum sharing scheme in improving the spectrum efficiency. Figure 2: Spectrum efficiency of ISTN with varying requested capacity of satellite system. To further demonstrate the characteristics of different schemes, Figure 3 and Figure 4 show the total transmission capacity of the satellite system and the average transmission capacity of each terrestrial system, respectively. As shown in Figure 3, when the requested capacity of the satellite system is low, the satellite system capacity increases linearly since all the capacity requirements can be met. However, because of the limited transmission resources of the satellite system, the satellite system capacity tends to saturate as the requested capacity increases, and the performance gap among different schemes becomes larger. The satellite system capacity of the MTCS scheme is higher than that of the other schemes, but the transmission capacity of the terrestrial systems cannot be guaranteed. The satellite system capacity of the proposed optimal algorithm is close to that of the MTCS scheme, while the average terrestrial system capacity is obviously improved. Owing to the introduction of the resource guarantee factor \(Q\), the greedy algorithm can achieve higher terrestrial system capacity than the optimal algorithm.