RETRACTED CHAPTER: Management System for Optimizing Public Transport Networks: GPS Record

As cities continue to grow in size and population, the design of public transport networks becomes complicated, given the wide diversity in the origins and destinations of users [1], as well as the saturation of vehicle infrastructure in large cities despite their attempts to adapt it according to population distribution. This indicates that, in order to reduce users’ travel time, it is necessary to implement alternative road solutions to the use of cars, increasing investment in public transportation [2, 3] by conducting a comprehensive analysis of the state of transportation. This situation has made appear the solutions and development oriented to transportation based on Internet of Things (IoT) which allows, in a first stage, monitoring of public transport systems, in order to optimize the deployment of transport units and thus reduce the time of transfer of users through the cities [4]. These solution proposals are focused on information collected from user resources (data collected through smart phones) to create a common database [5]. The present study proposes the development of an intelligent monitoring and management system for public transportation networks using a hybrid communication architecture based on wireless node networks using IPv6 and cellular networks (LTE, LTE-M).


Introduction
This paper presents the first part of a scalable platform that allows to connect diverse sources of monitoring and information through a hybrid network, formed by different wireless networks [6]. This platform is designed to adapt to the new needs of the city of Medellin in Colombia as it is implemented, offering a way of intercommunication with

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new and existing systems which allows to start the conversion to an intelligent city, by first facing one of the most important problems at this time: Public transportation [7].
Public transport is a determining factor in mobility. This statement offers a perspective of individuals in their socioeconomic and spatial reality (age, gender, social and labor category) broader than the term transport, which is limited to a relation of supply and demand expressed schematically, on the one hand, in the amount of infrastructures and means of transport and, on the other hand, in the number of trips per day, mode, itinerary, time [8][9][10][11].
Public transport and traffic are associated with the economic and technical factors that determine the movement of people, while mobility is focused on individuals and their environment. Although they are different dimensions, it is clear that proper transport planning has a positive impact on mobility. This new conception of public transport materializes in the recent policies, plans and projects in Medellin-at least in discourseunder the concept of comprehensiveness or integration: comprehensive or integrated transportation in which various means of transportation are articulated, according with the territorial ordering in the area of the city-region. Thus, an attempt has been made to overcome the conception of public transport as simply satisfying the conditions of the supply and demand for travel, based on the delimitation of the economically active population, to recognize its importance in transforming the socioeconomic structure and the social space based on the participation of the population [12][13][14][15][16].
The proposal is focused on solving the challenge of knowing the status of public transport, dividing it into three essential parts: the first part deals with the general hardware and software modules required for the proper operation of the system [17], then briefly describes the network architecture that will be used and the technologies and protocols required for the operation of the network. Finally, the third part describes the general architecture of the system and defines the way to communicate the information collected from the bus network to an information system for subsequent deployment to the users' devices.

Development
Based on the characteristics of the different types of transport systems analyzed (Metrobus, Transmilenio, etc.) and the different needs of the users, a modular, scalable and minimally invasive solution is proposed, which uses new generation and low-cost technologies. These characteristics allow the implementation of monitoring and communication devices in a simple way, making use of existing infrastructure. The following is a general description of the elements that make up the system at the hardware and software levels [18].

System Elements
The elements of the system are divided into: Monitoring modules, which include the bus and station modules; Web and mobile application; and Information system [19].

Bus Monitoring (A: Thread, and B: Thread+LTE)
With the purpose of informing the level of saturation in transport lines, modules will be implemented for obtaining the number of users in the unit at all times. In the same way to know the location of the units, a GPS module will be installed to operate in conjunction with a BLE transceiver to detect micro location devices "Beacons" to inform the user about the station in which he is through a web application of the system [20]. As it can be seen in Fig. 1, it is proposed to distribute this monitoring in two types of modules according to the type of transport in which the system will be implemented. For transport systems with marked stations, for example RTP, type B nodes will be used, on the other hand, for transport systems with stations with fixed structures, for example MB, type A or B nodes can be used indistinctly.
The design of the nodes is shaped as follows [21,22]: Figure 2 shows the block diagram of the ascent/descent modules. The monitoring modules will be distributed at each of the unit's ascent and descent points [23], and will be responsible for obtaining the ascent and descent information at each point of the unit, and communicating it to the central bus module to calculate the current number of people within the unit.

Station Modules
As previously mentioned, this system focuses on distributing the devices on the buses, with the aim of ensuring the versatility of the solution, in other words, that any transport system is applicable to the solution with the least possible adjustments. However, it is necessary to place identification modules in the stations for a correct synchronization and deployment of user information. These modules can be completely autonomous and with minimal impact on the current infrastructure. According to the type of transport system in which the solution will be implemented, two types of modules are proposed [24,25]: In the case of routes that only have signposted stations, "Beacons" will be placed at each station. This device will allow to obtain the proximity of the buses to the station based on the signal intensity, that is, whether they are arriving, departing or standing at the station. The device in conjunction with the GPS module will obtain information on the location of the unit, allowing users who have the mobile application on their devices to visualize the station they are in automatically and without consuming their data packet or GPS module, as long as they are compatible with the protocol to be used in the Beacons [26][27][28] (Fig. 3).
-Fixed structure stations These modules only act as repeaters and border nodes of the Thread network deployed between stations and buses. The main feature to highlight about these nodes is their capability to adapt to the communication technology at the Internet level that is available in the place, i.e. you can implement the system communication at the Internet level from a module, LTE, 3G, Wi-Fi or Ethernet, among others [29]. -Web application For the deployment of information to users, a web application will be developed for allowing access to system information from any compatible device, and adapt this web application to run on smartphones with Android and iOS operating systems.

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The mobile application would allow transport users to visualize the status of the lines including: arrival time of the next bus at a specific stop, level of saturation of the bus (number of people/specified capacity), different transport routes registered in the system that stop at the same stop, as well as to automatically detect the stop it is at by detecting the "Beacon" installed in the stop [30].

Information System
The information collected from the transport systems shall be communicated through the LTE modules with the information system. This is the one in charge of processing and storing all the information of the network so that it can be displayed in an easy and understandable way by means of graphics and indicators of the different variables of the system [31].
The information system will be hosted in a private cloud platform and managed through the use of REST services. These will interconnect the different nodes of the system, as well as the mobile clients and web applications [32].

Network Architecture
For the communication of the different monitoring points, a hybrid network architecture is proposed, consisting of a network of wireless nodes that provides a first communication infrastructure between the transport units and a set of LTE links that allow all the nodes

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to communicate to an information system in the cloud which distributes the information to the users of the transport network (Fig. 4). It is necessary to place monitoring nodes at different points of the transportation unit. These points will communicate wirelessly via a Bluetooth Mesh network [2]. The information will be concentrated in the main node of the vehicle which will communicate the monitored variables with the nearby nodes using the Thread network and, in case the vehicle has a LTE modem, the information will also be sent by this means to the information system (Fig. 5). In order to interconnect the different transportation units with the fixed structure stations and later communicate with the information system, Thread-based nodes will be deployed in the stations, which will allow direct communication between stations and transport units, optimizing the distribution of the variables monitored at each point in an independent way, thus helping to feed the automatic learning algorithms that will be implemented in the node network (Fig. 6), in the same way that in the transport units some specific stations will be selected (based on their geographical location) to include in their node an LTE modem for allowing the communication of the nodes with the information system [33][34][35].

Fig. 6. Distribution of nodes in transportation stations
In the case of stations that do not have the necessary features to operate a communication node, such as those consisting only of a sign on a road, "Beacons" micro location devices will be placed to allow transport units to know and report the location of the unit through the station identifier (Fig. 7) and, in the case of users with compatible mobile devices, to obtain information on the next transport units through the mobile application developed [36][37][38][39].
Finally, the users of the system (passengers, operators and managers of the transport network) will view the information collected from the system through a web application on any device compatible with an internet connection.

System Architecture
For the communication at a logical level of all the components of the system, a modular software architecture is proposed to allow the monitoring and notification to the modules by using REST services for the first case and PUSH notifications for the second one. This architecture is greatly simplified in the communication with the Thread nodes because this protocol allows redirecting the information frames directly thanks to the implementation of IPv6 within the node communication [8].
The nodes distributed in the buses communicate the information collected through the Bluetooth Mesh network deployed inside the bus, later this is communicated through the Thread network until reaching a border node from which it will communicate to the Web server using Web services [40,41].

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Once on the server, this information will be processed and stored in the information system database, and then, based on the source of the information, the nodes and users will be notified at the relevant stations through the notification channels. PUSH, which will prevent the Web application and the network nodes from constantly "pulsing" [42].

Implementation
Up to this moment, the analysis and design of the monitoring modules inside the bus has been carried out. These modules manage the users' account inside the transport units. Two prototypes were developed in this way, the first one using the nRF24L01+ transceiver with the objective of communicating the different nodes installed inside a unit. Due to the modularity of the system, the characteristics of the wireless sensor network can be modified, so the second prototype was chosen to use a set of different sensors and transceivers. In this second case, an infrared cut sensor was added in conjunction with the infrared distance sensors and an XBee S2C as a communication module between nodes (Fig. 8). Finally, an adaptable module was designed to which any of the two transceivers can be connected, as well as the different sensors analyzed. This last design was made in EAGLE and seeks to be compact and compatible with any of the transceivers tested, using ZigBee through XBee using the XB1 module or through BLE through nRF24L01+ using the JP3 connector (Fig. 9).
Likewise, the research process included the development of cards based on nRF52840 for the deployment of bus and station nodes. These modules are in charge of generating the multiprotocol Thread network with BLE for the communication of the different transport units.

Conclusions
The proposed system differs from other similar implementations in the communication architecture of transport vehicles which allows the node to know the status of other nodes besides its own.
The main advantages of the proposal are • Easily scalable architecture.
• Wireless nodes that allow high flexibility in the installation within the transport units.
• Communication of the transport units without internet connection • Possibility of using different types of transport units and different routes within the same system.
As future work, the communication network between buses and stations based on the Thread protocol will be developed, the LTE-M communication modules will be developed, and the information system will be developed with the necessary communication technologies to verify the correct operation of the system, some nodes will also be deployed in designated vehicles which will be monitored on a defined road within the city, in order to carry out operational tests in a real environment and verify the functionality of the system.
In a next stage, it is considered to visualize the possibility of integrating the payment of the transport service through the platform, as well as acting as an identification credential for access to the transport route. This can be developed through the implementation of NFC or through some dynamic two-dimensional code (QR, PDF417, etc.).
Finally, we consider that it is important to develop solutions focused on IoT, including Smart Cities that allow the integration of the diverse existing infrastructure to the new trends in information systems, so that the different services offered by cities can be optimized, reducing, in the case of public transport, transfer times and improving the efficiency of fuel consumption, gradually improving the quality of life of the inhabitants.