# Collecting Sensed Data with Opportunistic Networks: The Case of Contact Information Overhead
## 5 Evaluation
### Evaluation Methodology
#### 5.1.1 Simulation Set-Up  
The ONE simulator ([PERSON] et al., 2017) is used to carry out simulations. We assume mobile users in a city using smartphones or similar handheld devices equipped with GPS and a Bluetooth interface operating at 2 Mbps with a transmission range of 10 m. The free buffer space of the nodes for routing-related tasks is limited to 10 MB, as users may not be willing to shed all their storage space to carry data on behalf of the technology. In order to observe a realistic node mobility and portray variations of human movement patterns that correspond to users of different occupations and backgrounds, the Working Day Movement (WDM) model ([PERSON] et al., 2017) is used.  
As shown in Figure 4, the simulation area roughly covers a 21 KM \(\times\) 11 KM terrain, and consists of 32 districts. Since WDM models daily movement routines in working days, a total simulation duration of 5 days is chosen, which is distributed as follows: 1 day for warm-up (to ensure complete encounter and location history generation); 3 days for message generation and routing; and 1 day for cool-down. To simulate an OppNet for collecting data from sensors to their respective gateways in a city, static nodes are placed in popular locations to represent 64 sources and 32 destinations, respectively. Specifically, the source nodes were located in node homes (to represent residential areas) and along roads (for environmental sensors), while the destination nodes were located in other popular locations (to represent offices and shopping malls). Each source generates 1 message to a randomly selected destination every hour (to avoid bias), making a total of 4608 messages at the end of 3 days. Message TTL is set to 24 h, since focus is on messages to be delivered during a period of 1 day. The size of messages is uniformly distributed between 10 KB and 15 KB, considering the type of delay-tolerant applications mentioned in Section 1.1.  
Energy consumption for Bluetooth is according to the configuration settings in the module proposed by [PERSON] et al. (2017). All nodes are assigned an initial battery capacity of 4800 Joules, while the energy expended in receiving or sending messages is set to 0.08 mW/s. We are interested in onlyenergy consumed due to forwarding decisions made by each forwarding algorithm under comparison. Therefore, only energy consumed from receiving and sending messages is considered and other means through which nodes consume energy is ignored. On that basis, scan energy (i.e., energy consumed from device discovery), scan response energy (i.e., energy consumed from device discovery response), and base energy (i.e., energy consumed in idle state) is set to 0. The initial energy is high enough so nodes do not run out of energy during the simulation (Note that energy consumption in the simulation is mainly for performance comparison, and is not intended to represent realistic energy values). The parameters used for the simulation setup are shown in Table 5. 10 trials with different random seeds are simulated for each result in order to present the average and the 95% confidence interval.