## 5 Simulation Results
### Dmac  
We consider two different traffic condition, namely saturated and non-saturated. In the saturated scenario, all of the nodes generate packets with an interval time of 1 millisecond (ms) and thus they always have a non-empty transmitting queue. In order to investigate the impact of different packet sizes, we also choose three kinds of packet size: 200, 500, and 1000 bytes. In non-saturated scenario, we connect 50 nodes to one AP and choose a fixed packet size as 1000 bytes. In addition, the packet interval time for nodes is 10 ms and 100 ms, respectively. We also define a variable \(\theta\) as their proportion and, thus, \(\theta\) can be regarded as the network saturated degree. Figure 4 shows the system throughput and channel utilization under saturated and non-saturated scenarios.  
Figure 3: Saturated system throughput versus \(\tau\).  
Figure 4a,b depict the system throughput and channel utilization varying with different network densities in saturated scenario. When compared to legacy DCF and IO-MAC, the DMAC always keep significant improvement, regardless of the packet size, which is due to its data transmission period that builds a collision-free schedule and performs consecutive transmission. Although the IO-MAC algorithm can also degrade collisions, it still exits much idle time, even though all nodes get into reservation status. As it can be observed in the figure, DMAC has at least 6.8% higher system throughput than IO-MAC. Figure 4c,d show the system throughput and channel utilization in non-saturated scenario. The curves show an increase of the throughput as \(\theta\) grows. In contrast, throughput and utilization for DCF both keep decreasing due to an augmented number of collisions as the network saturated degree increases. Especially in approximate saturated condition (when \(\theta\)\(\approx\)1), DCF suffers from an increasing number of collisions. Additionally, nevertheless, DMAC performs longer periods of collision-free operation due to all nodes getting saturated.  
We also investigate the delay by letting all nodes to delivery one Mega size file to the AP. In the saturated scenario, different packet size and network density are considered, similar to the previous simulations. Additionally, in the non-saturated scenario, we connect 50 nodes to one AP and choose a fixed packet size with 1000 bytes too. Subsequently, the maximum, minimum, and average delivery time for all nodes can be obtained under different saturated degree and Figure 5 shows their curves.  
Figure 4: Throughput and utilization in saturated and non-saturated scenarios. (**a**) System Throughput in saturated scenario; (**b**) Channel utilization in saturated scenario; (**c**) System Throughput in non-saturated scenario; and, (**d**) Channel utilization in non-saturated scenario.  
Figure 5a,b show the delivery time in saturated and non-saturated scenarios, respectively. We can see that DMAC can provide almost the same file delivery delay for all nodes and it has the lowest delay under different packet size and network density, which is due to its high channel utilization by eliminating collisions. In the non-saturated scenario, the saturated degree has a strong impact on all algorithms and the delivery time fluctuates greatly for different nodes. This is because the channel is often not efficiently utilized when some nodes compete for it. Nevertheless, DMAC always has the lowest average delivery time than the other two algorithms.