# A Reconfigurable Mesh-Ring Topology for Bluetooth Sensor Networks
## 4 Performance Results
The scatternt case achieves the highest PSP than the other two cases. As a result, the RMR achieves superior performance on the PSP than the conventional Ring and the cluster-based Mesh topologies. Figure 7: The determined bridge node with highest throughput of peak search method for piconet case. To reflect the scatternet capacity of RMR, a packet throughput is used to examine the overall network capacity. The average packet throughput in each device is defined as the ratio of the total number of successfully routed packets over the total simulation time in seconds. The simulation  
Figure 8: The determined mesh link with highest throughput of peak search method for three configuration cases. Figure 9: The packet successful probability (PSP) performance of the Reconfigurable Mesh-Ring (RMR) algorithm. results of the packet throughput for the three configuration cases of RMR, the conventional Ring and Mesh schemes are as shown in Figure 10. The piconet case achieves approximate throughput performance, compared to the conventional cluster-based Mesh scheme. In RMR, the scatternet case achieves the highest throughput performance since the even distributed mesh links among masters effectively improves the connected configuration than the other two cases. On the other hand, the packet throughput of conventional Ring is promptly saturated, as the packet generation rate increases above 4 since the traditional ring topology increases the hop length and thus reduces the throughput performance in the ring subnet. According to the simulation results, the proposed RMR with scatternet case improves by almost 70% throughput performance, as compared to the conventional ring scheme. In order to estimate the multi-hop routing performance, an average packet delay metric was used to measure the end-to-end delay of a scatternet. The packet delay of each routing packet is defined as the average packet transmission time from the first transmitted bit at the source node to the last received bit at the destination node. Figure 11 shows the average packet delay performances of the three cases of RMR, the conventional Ring and the cluster-based Mesh schemes. The packet delay increases as the packet generation rate increases since more packets have to be processed at network. The RMR scatternet case generates the smallest average delay, as it generates the even mesh connectivity than all the simulated cases. Another observation from the results is that the packet delay of the conventional Ring quickly increases versus the other three cases, as the packet generation rate increases above 4, because the traditional ring topology greatly increases the routing path length. A packet drop probability (PDP) metric is used to evaluate the impact of traffic congestion in a scatternet. When the FIFO buffer overflows in each node, the damaged routing packets, including both the currently received and newly generated routing packets, were dropped. The PDP is defined as the ratio of the total number of dropped packets over the total generated packets for all nodes. Figure 12 shows the PDP of the three cases of RMR, the conventional Ring and the cluster-based mesh schemes. Here, the RMR scatternet case achieves the lowest PDP than all other cases, since the scatternet case  
Figure 10: The network throughput performance of the RMR algorithm. achieves better mesh connectivity than the other ones. From the simulation results, it is clear that all masters begin to drop packets when the FIFO buffers overflow. Moreover, the packet generation rates are greater than 3 for the piconet case and the cluster-based mesh, 4 for the conventional ring and the scatternet case, and 5 for the hybrid case. From Figure 10, the throughput performance saturates even the packet generation rate, which increases when the packets start to be dropped in Figure 12. As a result, the tail drop mechanism can effectively manage the FIFO buffer and maintain throughput performance for network congestion conditions. Figure 6:0 The average packet delay performance of the RMR algorithm.