Erick Victor Souza Marques da Silva Thierry Pinheiro Moreira

Transcrição

1 UNIVERSIDADE DA AMAZÔNIA UNAMA Erick Victor Souza Marques da Silva Thierry Pinheiro Moreira PROCEDA Protocolo de Comunicação aplicado ao Encaminhamento de DACTs Belém 2011

2 UNIVERSIDADE DA AMAZÔNIA UNAMA Erick Victor Souza Marques da Silva Thierry Pinheiro Moreira PROCEDA Protocolo de Comunicação aplicado ao Encaminhamento de DACTs Trabalho de Conclusão de curso apresentado para obtenção do grau de bacharel em Ciência da Computação, da Universidade da Amazônia. Orientador: Mauro Margalho. Belém 2011

3 UNIVERSIDADE DA AMAZÔNIA UNAMA Erick Victor Souza Marques da Silva Thierry Pinheiro Moreira PROCEDA Protocolo de Comunicação aplicado ao Encaminhamento de DACTs Trabalho de Conclusão de curso apresentado para obtenção do grau de bacharel em Ciência da Computação, da Universidade da Amazônia. Data da Defesa: / / Conceito: Banca Examinadora Membro 1 Membro 2 Membro 3

4 A minha avó, Antonieta Léa, que partiu deixando muitas saudades. Erick Victor

5 Aos meus pais pelo apoio irrestrito em todos os momentos da minha vida. Thierry Moreira

6 AGRADECIMENTOS Agradeço primeiramente a Deus que tornou tudo isso possível. Agradeço, também, aos meus pais, Guto e Neide, por tudo. Sei que todos seus atos foram em prol de meu crescimento, fazendo me tornar a pessoa que sou. Aos meus avós, Carmen e Raimundo, meus segundos pais, que fizeram sempre tudo por mim e pela Kelly, a quem posso dizer que sou muito feliz por ter como minha irmã. Ao meu orientador, Mauro Margalho, que me deu a oportunidade de fazer parte deste projeto e por toda orientação nos momentos precisos, fazendo com que este trabalho fosse realizado com sucesso ao lado do meu amigo Thierry Moreira. A Raphaela Matos por todos esses anos ao meu lado e por todos os momentos juntos, assim como à sua família, pessoas por quem tenho grande adimiração. Por fim, meus amigos, amigos de longa data, amigos que conheci a pouco tempo e grandes amigos que fiz na Unama, pessoas que vou levar pra sempre comigo. Erick Victor

7 AGRADECIMENTOS Agradeço aos meus pais, Jacques e Rosinete por absolutamente tudo. Cada um de seus atos foi uma oportunidade que eu tive para crescer e me tornar o que sou. Às minhas irmãs, Mireille e Cibelle, pelo apoio e amor incondicional e que felizmente posso dizer ser recíproco. À minha família Iunes. Os meus parentes distantes no sangue, mas muito próximos em afinidade e amor. À minha família Moreira, sempre perto de mim, me dando apoio e amor em todos os períodos da minha vida. Ao meu orientador Mauro Margalho, pelas orientações precisas em todos os momentos solicitados, pela sua dedicação e pela verdadeira vontade de desenvolver este trabalho. E à minha namorada, Larissa, e a sua família, que sempre me deram seu apoio. Thierry Moreira

8 De tudo, ficaram três coisas: a certeza de que estamos começando, a certeza de que é preciso continuar e a certeza de que podemos ser interrompidos antes de terminar. Façamos da interrupção um caminho novo, da queda um passo de dança, do medo uma escada, do sonho uma ponte e da procura um encontro. Fernando Sabino

9 Artigo aprovado Work in Progress: A new proposal of data mule network focused on Amazon riverine population, ExtremeCom a 30 set Manaus (AM),

10 Work in Progress: A new proposal of data mule network focused on Amazon riverine population Mauro Margalho Coutinho University of Amazônia Av. Alcindo Cacela, 287 CEP: Belém PA margalho@unama.br Thierry Moreira, Erick Silva University of Amazônia Av. Alcindo Cacela, 287 CEP: Belém PA thierrypin, erickvsouza@gmail.com Alon Efrat, Thienne Johnson University of Arizona Gould-Simpson Building Tucson AZ alon, thienne@cs.arizona.edu ABSTRACT This paper presents a new proposal to provide electronic health care for riverine communities through Vehicular Ad Hoc Networks (VANETs), using boats as data mules. The focus of this project is based in specific scenarios without telecommunications infrastructure, like Marajó Archipelago, located in north of Brazil, at Amazon Forest. Categories and Subject Descriptors C.2.1 [Computer-Communication Networks]: Network Architecture and Design - Wireless communication, Store and forward networks. General Terms Algorithms, Measurement, Experimentation Keywords VANETs, Ad-Hoc, Data Mule, CoDPON, Digital Divide 1. INTRODUCTION Unfortunately, in many countries, there are still many communities not connected to the Internet due to the lack of telecommunications infrastructure. This scenario is still prevalent in the Amazon region, mainly in the riverine communities. Solutions based on satellite communications are extremely expensive and, if adopted, would constitute a social incoherence, as the monthly costs of a satellite link in these regions are enough to maintain a small school in these communities. Due to the low population density, Telecommunication Companies (TelCos) are not interested in investing in these areas. In fact, any solution for this problem should have a low cost. One way to solve the problem is to use boats as data mules [3, 6]. Boats are the main means of transportation in these areas. Through a data collection ExtremeCom 11, September 26-30, 2011, Manaus, Brazil. Figure 1: Regional boats carrying information to Peer Base Stations. system and a collaborative network, it is possible to enable applications that do not have strict requirements of delay and can admit disconnections [1, 9, 7, 4, 2]. The prototype is under construction on the Laboratory for Research on Alternative Technologies Related to the Amazon (PETALA), from University of Amazônia in partnership with the University of Arizona. 2. CODPON NETWORKS CoDPON networks (Continuous Displacement Plan Oriented Network) are based on air traffic control system. The flight plan in a CoDPON network is called displacement plan (DP) and the control towers are called Peer Base Station (PBS). The model is similar to logistics traffic of the boats in Amazon. Each remote community has, at least, one Peer Base Station that is a fixed point, previously mapped, where boats make scheduled stops. Peer Base Stations are located on the sea shore, frequently in harbors (Figure 1). In a CoDPON network there are basically three types of nodes: boats, Peers Base Stations and Hot Spots. Boats act as mules, carrying the data spread along the path. The boats used on a CoDPON network are mostly maintained by municipalities. They operate with pre-defined routes, days and times of departures and arrivals. Moreover, these boats are used daily by locals as the main transportation vehicle since the river is the best link between these commu-

11 nities. Each boat has its displacement plan stored locally. The computers, located inside the boat, carry a kit called KDE (Kit of Data Exchange) fixed on boat roof. Peer Base Stations are fixed points, previously mapped, where nodes make scheduled stops. Peer base stations are located on the river shore. When a boat anchors in a Peer Base Station, displacement plans are compared. Applications data are loaded or unloaded accordingly to following destinations or stopovers. In a CoDPON network, there is one peer base station called MATRIX. All others nodes host a table with hydrographic distance to the MATRIX peer base station. The third type of node is called Hot Spot. This special node exists only on areas that have connection with the Internet. It is a gateway between CoDPON networks and the Internet. If a boat crosses with a CoDPON Hotspot, a copy of all data on board is forwarded. CoDPON Hotspots can be found in special ships such as those maintained by the military, which always keep Internet connection [5]. Applications data are divided into logical units called DACT (Data Application in Transit). Each DACT represents a minimum unit of data transfer between nodes and has a self-meaning that, therefore, can be separated from others without losing consistency. The prototype system is able to send video (interview, body/face images, etc) and audio recording (for example, recording difficult-to-hear heart beat, lung, and body sounds using an electronic stethoscope) to Belém (capital of the State of Pará), where a doctor working for the SUS (Unified HealthCare System) can analyze the files, send prescription and also reserve a bed in a local hospital, sending back instructions for patients hospitalization and treatment [8]. A displacement plan is applied to all boats. It contains basic information about the entire route of the boat, including starting point, destination, stopovers and estimated time to journey and anchoring. Journey time is the time required for a boat along its entire route. Anchor time usually is the time to passengers embarkation or disembarkation. The communication is based on Vehicular Ad Hoc Networks (VANETs). All the communication protocol is written in C++ for Linux systems, using sockets and multithreading. General configurations, DACTs stored, displacement plans and language bundles are stored, read and written in files. 3. EVALUATION OF THE PROTOTYPE Based on the evaluations we chose to use DACTs size of 1500 bytes once it represents the best benefit. In a first test, made in a network environment similar to what the boats will have, done after the construction of the prototype and presented in the graph of figures 2, each DACT carried a multimedia file of 884 Kbytes (data from the electronic stethoscope for example). In this experiment, three tests were run, transmitting 100, 500 and 1000 files. The average time to transfer 100 multimedia DACTs was 1.96 seconds. 4. CONCLUSIONS Data mules are proving to be an inexpensive way to establish network communication in poor areas (and that are hard to reach with conventional network infrastructure). The solution is not dependent on telecom providers and has a large number of potential uses. The work described in this paper has general purposes: , multimedia, plain data and other things can be transmitted. However it just describes a Figure 2: Performance Evaluation of Multimedia File Transfer in a CoDPON Network. way of sending the data. Front-end applications still need to be made. There are dozens of applications that would suit the needs of the archipelago of Marajó (or other locations); some are already in development. 5. REFERENCES [1] V. Cerf, S. Burleigh, A. Hooke, L. Torgerson, R. Durst, K. Scott, K. Fall, and H. Weiss. Delay-tolerant networking architecture [2] F. Dong, Y. Hu, M. Tong, and X. Ran. Supporting emergency service by retasking delay-tolerant network architecture. Mobile Ad-hoc and Sensor Networks, International Conference on, 0: , [3] C.-J. Jiang, C. Chen, J.-W. Chang, R.-H. Jan, and T. C. Chiang. Construct small worlds in wireless networks using data mules. Sensor Networks, Ubiquitous, and Trustworthy Computing, International Conference on, 0:28 35, [4] K. Lan and Z. Wu. On the feasibility of using public transport as data mules for traffic monitoring. In WWW 06, page Intelligent Vehicles Symposium, 2008 IEEE, June. [5] M. Margalho. Uso de redes codpon em aplicações de governo eletrônico. In WCGE, pages Sociedade Brasileira de Computação, July [6] S. Naidu, S. Chintada, M. Sen, and S. Raghavan. Challenges in deploying a delay tolerant network. In Proceedings of the third ACM workshop on Challenged networks, CHANTS 08, pages 65 72, New York, NY, USA, ACM. [7] T. S. Parikh and E. D. Lazowska. Designing an architecture for delivering mobile information services to the rural developing world. In WWW 06, pages , [8] N. Qadri, M. Altaf, M. Fleury, M. Ghanbari, and H. Sammak. Robust video streaming over an urban vanet. In Proceedings of the 2009 IEEE International Conference on Wireless and Mobile Computing, Networking and Communications, WIMOB 09, pages , Washington, DC, USA, IEEE Computer Society. [9] J. Scholl, L. Lambrinos, and A. Lindgren. Rural telemedicine networks using store-and-forward voice-over-ip. In MIE, volume 150 of Studies in Health Technology and Informatics, pages IOS Press, 2009.

12 F:\TCC\ .txt quarta-feira, 14 de dezembro de :10 Date: Tue, 6 Sep :22: From: ExtremeCom 2011 <extremecom2011@easychair.org> To: Mauro Coutinho <mauro@margalho.pro.br> Subject: Your ExtremeCom 2011 submission Dear Mauro, This is to confirm that your submission Work in Progress:A new proposal of data mule network focused on Amazon riverine population has been accepted as a short paper to the ExtremeCom 2011 conference. We look forward to seeing you at the conference in Manaus in September. Best regards, /Anders Lindgren and Pan Hui, General chairs, ExtremeCom

13

14

15 Artigo aprovado 2011 A New Proposal of Data Mule Network Focused on Amazon Riverine Population, Revista Traços ISSN , v.13, n.28, Dezembro de 2011.

16 A NEW PROPOSAL OF DATA MULE NETWORK FOCUSED ON AMAZON RIVERINE POPULATION Mauro Margalho Coutinho, Thierry Moreira, Erick Silva Universidade da Amazônia Av. Alcindo Cacela, 287 CEP: Belém PA Resumo Este artigo apresenta uma nova proposta para prover serviços eletrônicos de saúde para comunidades ribeirinhas através de uma rede Ad-Hoc veicular (VANET), usando barcos como mulas de dados. Este projeto foca em um cenário específico, onde não há infraestrutura de telecomunicações, como o arquipélago do Marajó, localizado no norte do Brasil, na floresta amazônica. Esta localidade é caracterizada por ter altos níveis de exclusão digital e o principal meio de transporte serem barcos. Existem aproximadamente ilhas espalhadas por mais de quilômetros quadrados, com 12 cidades e centenas de pequenas comunidades. A maioria das vilas não possuem médicos, apenas enfermeiras ou técnicos de saúde. Os rios da Amazônia possuem topologia complexa e estão cercados por densa vegetação, isto torna os serviços de saúde desafios ainda mais complexos. Além disso, o clima da região é muito instável, com chuvas frequentes e altas temperaturas. Palavras-Chave VANETs. Ad-Hoc. Data Mule. CoDPON. Exclusão Digital. Abstract This paper presents a new proposal to provide electronic health care for riverine communities through Vehicular Ad Hoc Networks (VANETs), using boats as data mules. The focus of this project is based in specific scenarios without telecommunications infrastructure, like Marajó Archipelago, located in north of Brazil, at Amazon Forest. This place is characterized by having high levels of digital divide and the main mean of transportation are boats. There are approximately 2,500 islands scattered over more than 42,000 kilometers square with 12 cities and hundreds of small communities. Also there are no doctors in most villages, only nurses or healthcare assistants. The rivers of Amazonia have a complex topology and are surrounded by dense vegetation which makes the challenge of providing healthcare services to the villages even more complex. Also the climate at the region is very unstable with frequent rain and high temperatures. Keywords VANETs. Ad-Hoc. Data Mule. CoDPON. Digital Divide. 1. Introduction

17 Unfortunately in many countries there are still lots of communities not connected to the Internet due to the lack of telecommunications infrastructure. This scenario is still very prevalent in the Amazon region, mainly in the riverine communities. Solutions based on satellite communications are extremely expensive and, if adopted, it would constitute a social incoherence, as the monthly value of a satellite link in these regions would maintain a small school in these communities. Due to the low population density, Telecommunication Companies (TelCos) are not interested in investing in these areas. Actually, every solution for this problem should have a low cost. One way to solve the problem is to use boats as data mules [12][13]. Boats are the main means of transportation in these areas. Through a data collection system and a collaborative network it is possible to enable applications that do not have strict requirements of delay and can admit disconnections. This is the basic principle of operation of Delay Tolerant Networks DTN [1]. However, DTN networks require a change in the TCP/IP stack with the addition of a new layer called bundle. This would entail an additional cost that would make the proposal financially unviable in this scenario. In this paper, we propose and test the performance of an alternative type of DTN called CoDPON (Continuous Displacement Plan Oriented Network) where no changes in the TCP/IP stack is required, allowing the cost of project implementation to be reduced significantly. Some previously conclusions based on a simulation technique were presented in [2]. However, the focus of this paper is based on the evaluation of the prototype constructed on the Laboratory for Research on Alternative Technologies Related to the Amazon (PETALA), from University of Amazônia in partnership with the University of Arizona. 2. Related Work The design and deployment of data mule networks in developing nations has been a research subject for some years because of its advantages (in financial terms) for many countries. As connectivity and power infrastructure required to support such continuous access may be too costly to justify deployment in many developing regions, many applications could be designed around asynchronous communication

18 and intermittent connectivity, as this form of infrastructure can be created at a significantly reduced cost. Some applications that can benefit for such approach could be [3] electronic form filling, commodity price updates, weather forecasts, offline search engine queries, and traditional applications such as and voic . They also cite the use of intermittent communications for medical applications. They say that although it may be difficult for that kind of transmission to have an impact on certain health issues like malnutrition, it can directly impact some areas including disease control, telemedicine, improving doctors efficiency, offering low-cost diagnostics, improving data collection, and providing patient management tools. DTN-based Telemedicine solutions that support other data, such as data backups of Electronic Medical Records, may also provide benefits to rural healthcare systems and should be worth investigating [4]. Smartphones can be a useful device for data intermittent transmissions as they are light and not as expensive as a computer (they can be used inside an area without infrastructure, because most models can transmit over WiFi networks). Parikh et al [5] developed a system for DTN using mobile devices, supporting minimal navigation, direct linkage to paper practices and offline multi-media interaction. Users navigate within and between applications by capturing barcodes using the mobile phone s built-in camera, or by entering numeric strings. The application provides an API for accessing the mobile phone s user interface, networking and multimedia input and output capabilities. Applications are downloaded on demand from an online source, either via the web or a multimedia message (MMS). One problem with this system is the use of a non-trivial interface that requires some practice or manual to work with the barcodes and string codes. In some developing countries, that interaction could be very difficult for the users. LAN and Wu [6] proposed the use of public transportation system as a data mule network. They assume that all buses, bus stops and traffic lights are equipped with a wireless device. Each bus is equipped with a wireless device which allows it to communicate with buses within its radio range and form a self-organized ad-hoc network cluster and a small number of mobile gateways are deployed on a few selected buses. They evaluated their system using simulations and they used realistic mobility patterns of city buses from a metropolitan city. They concluded that a Dedicated Short Range Communications [7] with a range of 1 km is a reasonable

19 candidate for their scenarios of 400sq km and being serviced by 4813 buses in 57 routes. By optimally choosing the candidate buses as the gateways, at least 80% of the buses can be covered with the deployment of 20% of the overall buses to serve as mobile gateway. Sundararaj and Vellaiyan [8] also studied the use of scheduled bus service to towns as data mules. They infer a bus is a superior data mule in technical terms as it has a decent power source from its alternator and battery. Their simulation study was composed of buses collecting data from lakes, with lakes adjoining the road chosen as they will be within the 30 meter radio range of the IEEE wi-fi which forms the radio link between the sensor nodes and data mules. One of the lakes was a special candidate that is located interior and away from the road. Special data mules were 4 collared cows from a cattle herd that regularly graze the fallow lands between the road and lake. For this system, sensor nodes sample a water parameter every 3 hours. Scholl et al [4] proposed to build store-and-forward VoIP networks based on DTN. The idea is to package all messages from an entire session into a single bundle; this can be sent over the DTN using application specific bundling gateways on both sides of the DTN. Transmitting VoIP data onto the DTN network thus requires the creation of a VoIP/DTN tunnel that can bundle packets, transmit them to the DTN network, and unbundle these packets at their destination. A VoIP communication would be very useful for remote areas communication, where there is no telephone system or other option for communication. VoIP also could allow remote medical interviews or doctor-nurse communication. 3. CoDPON Networks CoDPON networks are based on air traffic control system. In those systems, flight plans are documents prepared before the departures and usually include basic information such as points of departure and arrival, estimated time and route, alternate airports in case of bad weather, etc. CoDPON networks has the same principle, but applied to boats. The flight plan in a CoDPON network is called displacement plan (DP) and the control towers are called Peer Base Station (PBS).

20 The model is similar to logistics traffic of the boats in Amazon. It assumes that each boat has its own displacement plan with route, sources departure, destination arrival, stopovers and estimated time to journey and anchoring. Each remote community has, at least, one Peer Base Station that is a fixed point, previously mapped, where boats make scheduled stops. Peer Base Stations are located on the sea shore, frequently in harbors. 3.1 Nodes In a CoDPON network there are basically three types of nodes: boats, Peers Base Stations and Hot Spots. Boats act as mules, carrying the data spread along the path. The boats used on a CoDPON network are mostly maintained by municipalities. They operate with pre-defined routes, days and times of departures and arrivals. Moreover, these boats are used daily by locals as the main transportation vehicle since the river is the best link between these communities. Each boat has its displacement plan stored locally. All boats have a basic personal computer housed in an airtight box and use solid state disk to ensure more robust and persistent storage. This is necessary because the climate in the region is quite unstable. The computers, located inside the boat, carries a kit called KDE (Kit Data Exchange) containing a wireless network card (standard IEEE ) connected to an omnidirectional antenna fixed on boat roof (Fig 1) Figure 1. KDE (Kit Data Exchange) Peer Base Stations are fixed points, previously mapped, where nodes make scheduled stops. Peer base stations are located on the river shore. When a boat anchors in a peer base station, displacement plans are compared. Applications data are loaded or unloaded accordingly to following destinations or stopovers. In a CoDPON network there is one peer base station called MATRIX. All others nodes host a table with hydrographic distance to the MATRIX peer base station. GPS is not

21 used for proximity calculation because linear distances are not always equivalent to the hydrographic distances. The third type of node is called Hot Spot. This special node exists only on areas that have connection with the Internet. It is a gateway between CoDPON networks and the Internet. If a boat crosses with a CoDPON Hotspot, a copy of all data on board is forwarded. CoDPON Hotspots can be found in special ships such as those maintained by the military who always keep Internet connection. 3.2 DACT Applications data are divided into logical units called DACT (Data Application in Transit). Each DACT represents a minimum unit of data transfer between nodes and has a self-meaning that, therefore, can be separated from others without losing consistency. This is important since the boats are always moving and not all DACTs may be passed in the same time (Fig 2). A tracking system based on satellite information could is used to manage the location of all boats, providing information to routing algorithms like velocity and position of the boats [10]. The use of an autonomous system of data transfer is important once it minimizes inconsistencies caused by manual intervention. However, physical devices units as flash drives could be used as a backup alternative. The prototype system is able to send video (interview, body/face images, etc) and audio recording (for example, recording difficult-to-hear heart beat, lung, and body sounds using an electronic stethoscope) to Belém (capital of the State of Pará), where a doctor working for the SUS (Unified HealthCare System) can analyze the images, send prescription and also reserve a bed in a local hospital, sending back instructions for patients hospitalization and treatment.[11]

22 Figure 2. Regional boats carrying information to Peer Base Stations As the system is flexible, the equipment can be easily transferred from one region to another when real-time technologies are available in the region. This allows the system to be reassigned and reused elsewhere. The social impact of this project has a large scale once it will benefit hundreds of thousands of native people. This type of network could be used also to provide support to peripheral applications like reserving beds in hospitals and s exchanges. Moreover, it is possible to use multicast configuration for training nurses of specific regions to epidemic emergencies (i.e. dengue hemorrhagic fever, yellow fever, etc) [9]. 3.3 Displacement Plan A displacement plan is applied to all boats. It contains basic information about the entire route of the boat, including starting point, destination, stopovers and estimated time to journey and anchoring. Journey time is the time required for a boat along its entire route. Anchor time usually is the time to passengers embarkation or disembarkation. Each boat has his own displacement plan which has a table containing the hydrographic distances between peer base stations and peer base station MATRIX. It will be consulted whenever boats cross with other boats to verify the feasibility of transferring data between them. The table 1 shows an example of a displacement plan.

23 Table 1. Displacement Plan Source PBS_A Destinatio n PBS_D Departure from Arrival in Anchor time Journey time PBS_A PBS_B 20 min 2 hours PBS_B PBS_C 35 min 1 hours PBS_C PBS_D 20 min 1 hours 3.4 Communication Protocol The communication is based on Vehicular Ad Hoc Networks (VANETs). Each node is configured according to specific parameters. All the communication protocol is written in C++ for Linux systems, using sockets and multithreading. It consists of a program, running both server and client sides. General configurations, DACTs stored, displacement plans and language bundles are stored, read and written in files. It was used a three way handshake protocol to establish data exchange as show in Fig 3. Figure. 3. CoDPON Communication Protocol First the server node sends its fixed IP address on broadcast, second the client node sends its displacement plan to the server and finally, the server forwards data to the client, using a destiny in common with the displacement plan. In fact, all the boats run both server and client programs, once any boat registered in the system could act as a mule.

24 4. Evaluation of the Prototype The first item to be analyzed, after the construction of the prototype, was the best size for the DACT data container, which is transported within the TCP protocol. Once the size can vary up to 1500 bytes, performance tests were made considering sending of 1000 DACTs with sizes of 142, 500, 1000 and 1500 bytes respectively. The result can be presented in the graph of figures 4 and 5. Figure. 4. Performance Evaluation of DACT s Size Figure 5. Performance Evaluation of DACT with 1500 Bytes Based on these results we chose to use DACTs size of 1500 bytes once it represents the best benefit.

25 A second test using DACTs with 1500 bytes was performed to measure the transmission time. In this second experiment, presented in the graph of figures 6, were sent 5,000, 10,000 and 15,000 DACTs between CoDPON nodes. The results indicate the feasibility of transfer. The 15,000 DATCs were sent on an average of 0.8 seconds. Figure 6. Performance Evaluation of DACTs s Transfer In a third test, presented in the graph of figures 7, it was considered that each DACT carries a multimedia file of 884 Kbytes (data from the electronic stethoscope for example). In this experiment were transmitted respectively 100, 500 and 1000 files. The average time to transfer 100 multimedia DACTs was 1.96 seconds.

26 Figure 7. Performance Evaluation of Multimedia File Transfer in a CoDPON Network 5. Conclusions The tests objectified to equalize the size of the DACT and the protocol itself to have the best cost-benefit ratio, to optimize the number of DACTs boats can pass while crossing and how much information a single one can carry (the more information, less DACTs must be passed and bigger their size, making them harder to pass). Data mules are proving to be an inexpensive way to establish network communication in areas that are poor (and are hard to reach with conventional network infrastructure). The solution is not dependent on telecom providers and has a large number of potential uses. The work described in this paper has general purposes: , multimedia, plain data and other things can be transmitted. However it just describes a way of sending the data. Front-end applications still need to be made. There are dozens of applications that would suit the needs of the archipelago of Marajó (or other localities); some are already in development. The deployment of the system is very cheap. All the tests were made using home equipment, a simple Linux as operating system (with or without graphical interface) with no additional software installed. No special hardware or any different protocol implementation is required. References [1] V. Cerf, S. Burleigh, A. Hooke, L. Torgerson, R. Durst, K. Scott, K. Fall, and H. Weiss, Delay-Tolerant Networking Architecture, Request for Comments: 4838, Category: Informational, [2] M. Margalho, Uso de Redes CoDPON em Aplicações de Governo Eletrônico, WCGE, XXIX Congresso da Sociedade Brasileira de Computação. Bento Gonçalves, RS, Julho [3] E. Brewer et al. The Case for Technology in Developing Regions. Computer, June 2005 (vol. 38 no. 6), pp [4] J. SCHOLL, L. LAMBRINOS, and A. LINDGREN, Rural Telemedicine Networks Using Store-and-Forward Voice-over-IP, Medical Informatics in a United and Healthy Europe K.-P. Adlassnig et al. (Eds.), 2009.