# Internet of Bikes: A DTN Protocol with Data Aggregation for Urban Data Collection
## 2 Related Work
### Communication Based on Public Transport Networks  
Communication based on public transport network has been stressed in a number of recent works. [PERSON] et al. [13] presented the first studies of networks based on urban transportation systems. They highlighted the importance of the use of real transportation networks in order to overcome many problems. The authors in [14] investigated the DakNet network. It offers a new solution based on low-cost communication for distant villages in Cambodia and India. In DakNet, public buses transmit the requests from kiosks in villages to a server to be treated and then forward the results to each one of them. In [15], the KioskNet is proposed as an intermediary network between kiosks in remote villages and gateways in which the data are carried by vehicles and buses. The authors also presented an itemized architecture that studies the issues related to the low-cost and reliable connectivity for distant kiosks. To cope with the disconnection of cars in vehicular networks, [PERSON] et al. [16] proposed three vehicle-assisted data delivery (VADD) protocols based on the store, carry and forward approach [17] denoted as L-VADD, D-VADD, and H-VADD. Each car carries the data packet until it encounters another vehicle and then it sends the data to it. From their experimental outcomes, their proposal Hybrid Probe (H-VADD) protocol is the best and performs better than existing solutions regarding to the delivery delay, protocol overhead and delivery rate. [PERSON] et al. [18] proposed MaxProp DTN routing protocol. It addresses the question of scheduling packets to be forwarded to neighbors nodes as well as deleting old packets when the buffer is full. The authors evaluated the proposal using a real network called UMassDieselNet that was deployed on 30 buses to collect data during two months. Their results show that Maxprop DTN routing protocol offers better performances than protocols knowing in advance the meetings schedule between nodes. The BusNet network is presented in [19]. It is a public transport system based sensor network designed to monitor air pollution as well as the road surface condition. It takes the advantage of deploying few mobile sensors mounted on buses instead of a large number of static ones. Thus, it reduces the issues related to the security in addition to the management maintenance.  
Recently, bikes have been used as a city-based transport system for data collection applications. The first mobile sensing system based on bicycles was BikeNet project [20]. Sensors are mounted on cyclists bikes to collect quantitative data related to their journeys. BikeNet operates according two modes for data collection: opportunistic communications with gateways and real-time communications with mobile phones of cyclists to forward the sensed data. In [21], the authors designed the u-framework, a web framework for a ubiquitous sensor network to support application development using the database management system uTupleSpace. In their trial, they considered bikes with embedded sensors to collect data about environmental pollution in Tokyo, Japan.  
In recent years, there are many public bike systems that can collect real-time data. In these schemes, sensors that are mounted on bicycles start collecting data when the bikes leave their bike stations such as schemes in Germany [22] and Netherlands [23]. In the literature, many studies have focused on analyzing the movement of bicycles in public hire systems such as the public cycle hire systems in Lyon [24], Barcelona [25], and London [26].