## 4 Simulation Assessment of the ARounD Communication Scheme
### Results and Discussion
Following the same rationale, Figure 27 illustrates the packet loss rate as function of the background traffic data rates, while Figure 28 illustrates the packet loss rate as function of the network loads imposed by sensor nodes for the _Scenario 2_. Note that a similar behaviour was observed for this scenario, which shows that the ARounD approach can provide a better performance regarding to packet loss rate, when compared to the Standard Approach. Figure 26: Packet Loss Rate for ARounD Approach vs. Standard Approach for Scenario 1, considering different traffic loads imposed by sensor nodes. Figure 25: Packet Loss Rate for ARounD Approach vs. Standard Approach for Scenario 1, considering different data rates for the background traffic. An important issue is also the assessment of the impact of the source-to-destination traffic over the background traffic, when using the ARounD approach. For this purpose, a set of simulations were performed considering only background data traffic, in order to capture its behaviour without the source-to-destination traffic versus its behaviour considering also the source-to-destination data traffic (for different background data rates - application point of view). Figure 29 illustrates the number of received packets for _Scenario 1_, where it is clear that Standard approach has a negligible impact, but greater than those caused by the ARounD communication scheme. In fact, as the standard approach also uses the cluster-tree path to transfer source-to-destination traffic, the cluster-tree network has more packets contending for the communication path, increasing the packet loss rate. A similar behaviour was also observed for _Scenario 2_ and when varying the traffic load (network load perspective). Figure 28: Packet Loss Rate for ARounD Approach vs. Standard Approach for Scenario 2, considering different traffic loads imposed by sensor nodes. Figure 27: Packet Loss Rate for ARounD Approach vs. Standard Approach for Scenario 2, considering different data rates for the background traffic. It was also assessed the impact of source-to-destination data traffic upon the average end-to-end delay of background data traffic. As it can be seen in Figure 30, the ARounD communication traffic does not interfere with the background traffic. The main reason is that ARounD defines an alternative path to transmit source-to-destination traffic. Conversely, as the standard approach uses the cluster-tree path to transmit its source-to-destination data traffic, the number of packets in the MAC buffers tends to increase, impacting the background traffic end-to-end delay. A similar behaviour was also observed for _Scenario 2_. Finally, a set of experiments using multiples message streams were also assessed. The rationale behind these experiments is to show the capability of the proposed communication scheme to support multiple source-to-destination communication message streams. More specifically, we considered two communication scenarios with different traffic patterns for the source-to-destination traffic: many-to-one (three sources to a unique destination) and many-to-many (three sources and three destinations). Figure 31a illustrates a many-to-one communication scenario, where three sources (nodes 1, 2 and 3) send messages to a unique destination (node 4), while Figure 31b illustrates  
Figure 21:0 Impact of the source-to-destination data traffic (ARounD and Cluster-tree approaches) over the background data traffic delay, considering the Scenario 1. Figure 21:1 Impact of the source-to-destination traffic over the background traffic (Scenario 1). a many-to-many communication scenario, where three sources (nodes 1, 3 and 5) send messages to different destinations (nodes 2, 4 and 6), respectively. Figure 32 illustrates one of the physical topologies for the many-to-one scenario. Figure 32a illustrates the cluster-tree paths, where all communication paths follow the tree routing towards the PAN coordinator, generating more congestion for coordinator nodes.