# Internet of Bikes: A DTN Protocol with Data Aggregation for Urban Data Collection
## 8 Performance Improvement of IoB-DTN Based on Data Aggregation Mechanism
### Performance Comparison of Six Variants of IoB  
Here, we compare six variants of IoB-DTN protocol: the multi-hop IoB without data aggregation, IoB with one hop, IoB-Long range, IoB based on spatial aggregation, IoB based on temporal aggregation and IoB based on spatiotemporal aggregation. IoB with one hop behaves similar to the multi-hop IoB without aggregation except only bike-to-bike station communication is applied. The difference between IoB with one hop and IoB-LR is the communication range value. For the first variant, we keep the same communication range (\(\sim\)350) as the multi-hop IoB without aggregation, whereas we consider, as discussed before, a radio propagation that provides \(\sim\)1 km as communication range for IoB-LR.  
From the results obtained above, spatial aggregation with 20 m as aggregation area, temporal aggregation with 2 s as aggregation period and spatiotemporal with 20 m and 2 s as aggregation parameters offer the best outcomes in all simulated scenarios. Thus, we give a comparison of these variants with these aggregation values.  
Figure 39 shows the average delivery rate of the six variants of IoB-DTN protocol. The first observation we make is that the three variants of IoB based on data aggregation mechanism provide better delivery rate. Indeed, combining data packets into a single packet increases the probability to reach destinations. The fact that the delivery rate is higher by using a large buffer size indicates that more data packets are stored in buffers and forwarded later to base stations. This shows that the aggregation mechanism used provides robustness. More precisely, IoB based on temporal aggregation offers better result than other variants and it achieves 100% when the buffer size is large. It is also interesting to note that spatial aggregation gives better performance in terms of forwarding rate than spatiotemporal aggregation when the buffer size is small and inversely when increasing the buffer size.  
As for the throughput, as shown in Figure 40, the three variants of IoB based on data aggregation provide best performance.  
The average delivery delays are presented in Figure 41. Clearly, we notice that the three variants have the highest delays. The fact that data packets are combined generates a significant delay, which is an expected result. This may have as an explanation that data packets could be aggregated into packets in the buffers of the nodes having a lower probability to quickly meet base stations. More specifically, IoB based on spatial aggregation gives the worst delays.  
Figure 42 shows the average protocol cost of the six variants of IoB-DTN protocol. It is important to mention that applying data aggregation mechanism on IoB protocol reduces the communication cost in the network compared to other variants. More precisely, IoB with spatial aggregation offers the lower protocol cost.  
Figure 39: Average delivery rate comparison.  
As for the number of aggregated packets into a single packet, which is illustrated in Figure 43, we compare the three variants of IoB based on data aggregation with the parameters mentioned at the beginning of this part. We remark that IoB with spatiotemporal aggregation is better than the other  
Figure 41: Average delivery delay comparison.  
Figure 42: Average protocol cost comparison.  
Figure 40: Average throughput comparison.  
variants. It is also worth noting that IoB with temporal aggregation provides fewer packets aggregated per packet than IoB with spatial aggregation.