Global Healthcare Monitoring System using 6lowpan Networks Dhananjay Singh1, U.S. Tiwary2, Hoon-Jae Lee3 and Wan-Young Chung4 Dept. of Ubiquitous IT, Graduate School of Design & IT, Dongseo University, Busan, Korea 2 Indian Institute of Information Technology, Jhalwa, Allahabad, India 3 Div. of Information Network Eng., School of Internet Engineering, Dongseo University, Busan, Korea 4 Division of Electronics, Computer and Telecommunication Eng., Pukyong National University, Busan, Korea
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Abstract ⎯ Recent, technological advances in healthcare monitoring, sensors and wireless networking able to design a system for global healthcare monitoring applications such as ECG, SpO2, glucose, temperature etc. A 6lowpan (IPv6 low power wireless personal area networks) node with biomedical sensors strategically placed on the patient body area networks that can monitor biomedical data. The 6lowpan node has IP-address so it provides real-time feedback of patient to the service provider or doctor. Patient freely moves in-side the PAN or hospital area and service provider efficiently able to receive biomedical data. This technique we modified AODV protocol for pervasive 6lowpan networks. It used high level computational multi-hop communication method for transmitting biomedical data to the gateway. NS-2.33 simulator result shows the modified AODV protocol has better performance then LOAD and DYMO-low routing protocols for healthcare parameters. We tested real-time our modified protocols and show the performance of packet delivery ratio in time interval between 6lowpan nodes for healthcare parameters. Keywords ⎯ Healthcare, 6lowpan, Routing, Monitoring, PAN.
1. Introduction As the population of the developing countries are aging and required ever more medical attention. The 6lowpan sensor networks are getting more proven in growth opportunities exist in the global monitoring [1]. The global healthcare monitoring system fully based on IP-based wireless sensor networks. The 6lowpan node wirelessly connected to the various sensors such as SpO2, ECG, glucose, temperature etc. are placed on then patient body area network for monitoring health parameters [2]. All patients are attached with a 6lowpan node with its own unique IP-address that’s connected to the gateway via multi-hop mesh routing. The 6lowpan node contains biomedical data as well as current position of the patient in PAN (personal area network) at home or hospital [4]. The 6lowpan node is low-cost, light-weighted, wireless link and fast deployment. Each node consists of a very low power microcontroller, external memory and transceiver unit packed in a small area [5]. Multiple sensor nodes used to detect vital body signs for example electrocardiogram, health rate, blood pressure, oxygen saturation and motion. They are tiny patches placed
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on a patient body strategically for the patient comfortable without limiting the patient’s daily movement [5]. Thus, it brings advantages in term of extended period for monitoring purpose. The packet loss in short time, optimization of sampling rates, packet length, transmission rate during mobility for reliable biomedical data in 6lowpan networks have fatal factor for the patient [4]. The healthcare applications are running IPv6 networks to transport in communication or even higher-level protocols. LOAD and DYMO-low routing protocols have been developed by IETF group. However, both routing protocols works independently of IPv6 stack. Integrating the both routing protocols into 6lowpan stack implemented in this paper [6] . The purpose is to makes use of their functionality and to be transparent to application code. The IP-based network makes reliable, robust overall system due to high bandwidth and small delay. When emergency cases happen, the service provider efficiently connects to the patient even though both are apart far distance. For real time testing, we used 6lowpan nodes and gateway made by PicosNet at Ajou University Korea. In this paper we used dummy biomedical data and tested on IP based ubiquitous sensor nodes.
2. Design Issue The new concept used 6lowpan node and biomedical sensors which placed on the patient body and that’s successfully monitor patient’s biomedical data. The system provides an application for detect activity, events and potentially important medical symptom. The 6lowpan node transmits the biomedical data to service provider. It used multi-hop, mesh routing for packet transmission between nodes. It concludes that IP-based ubiquitous system is more convent than wired line in case of patient monitoring. It uses an event driven model because it support concurrent executions of tasks. It also avoids the difficulties of multithreaded execution. It has a single queue with the task system and operates in split-phase. 2.1 6lowpan Stack We design 6lowpan stack and did modification in adaptation layer in fragment reassembly. The mesh topology is handling
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multi-hop routing protocol and broadcast header HC1 and HC are the compression of the IPv6 and UDP headers. The IPv6 protocol required support of 1280 octets MTU (Maximum Transmission Unit).
The service provider directly ping or connect to the patient with the use of internet provider equipments and receive current status of the patient. This system operates in split-phase solving time consuming to complete to block other parts of the system. This happened because these tasks can come from any parts of the system as the user and kernel space has no separation between them. It does not have dynamic memory allocation.
Figure1. 6lowpan Stack for Network Simulator
The figure shows three different parts operate at the same time and connected to networks, which consists of client, gateway and server. Client side start with user access, network scheduler, network interface; gateway start with Ubiquitous Sensor Network(USN) management and scheduler, Node component, network interface; Server side start with resource management, resource scheduler, network interface. 2.1.1 Header Format IPv6 Dispatch
IPv6 Header
Payload
Lowpan encapsulate IPv6 datagram HC1 Dispatch
HC1 Header
Now a day’s several 6lowpan nodes are available in market such as Nano-series from Sensinode Finland, Arch rock node from Berkeley U. C. and IP-USN node from PicosNet at Korea etc. The 6lowpan node has modularity, mobility, neighbor discovery, supporting ICMPv6, ping, and experimental re-usability characteristics and the adaptation layer supports LOAD, AODV, DYMO-low routing protocols. For real time test-bet, we used IP-USN node from picosNet at Ajou University Korea. 2.3 . 6lowpan (IP-USN) Node
Payload
Lowpan encapsulate HC1 Compress IPv6 datagram Figure 2. Header format
In Figure, the lowpan encapsulate IPv6 datagram consists of IPv6 dispatch, IPv6 header and payload. For lowpan encapsulate HC1 compress IPv6 datagram of header format, it consists of HC1 dispatch, HC1 header and payload. The only different is it added HC1 compress in IPv6 header format datagram. 2.2 System Design We design a prototype for real-time patient monitoring which is developed for globally healthcare monitoring. In this system, we combined biomedical sensor with 6lowpan nodes fixed on several patients body area network. Patients can move freely in hospital or personal area networks. Each 6lowpan node has own IP-address to use multi-hop, mesh routing for packet transmission between nodes and individually wireless connected to the internet or gateway.
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Figure 3. Global patient monitoring system (Hospital)
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Each 6lowpan node has the Chipcon CC2420, 802.15.4 radio and Atmega128L / MSP430 (with 10k RAM). However, the 6lowpan node has additional integrated healthcare parameter based sensors such as 3-axis accelerometer, SpO2, ECG, temperature etc. The IEEE 802.15.4-2006 is a standard which specifies the physical layer and media access control are using automatically 16bit, and 64 bit address for ping operation on the node. 2.4 Gateway/Router The PicosNet gateway has 32-bit, 200 MHz digital cirrus EP9315 ARM9 RISC processor, 64Mbyte RAM, 64M byte Flash ROM, 100MHz bus systems, VGA, TI CC2420 WPAN interface, Ethernet 10/100bT & RJ45 connector, flash communication and 5V power.
3. Root Discovery Methods The 6lowpan (IPv6 over low power wireless personal area network) radios are characterized by low bit rate, low power, and low cost. It used various protocols for wireless
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connections and indirectly gains its popularity due to its unique advantages [1]. The 6lowpan stack support many features such as handling fragmentation, compression of the packet headers etc. and it contains additional interface that support UDP packets. The most important issue about IP connectivity is low power and secures [4]. When utilization of IP-based interconnects is the most common concern of industrial instrumentation makers. IP-option is utilizing neither TCP/IP nor UDP/IP over Ethernet [4]. For healthcare applications information add in MAC layer of the 6lowpan stack. The IEEE 802.15.4 standard defined reduced-function devices (RFDs) and full-function devices (FFDs) type of motes [4]. The MAC layer beacons, RFDs can only communicate with FFDs in a resulting "master/slave" topology. FFDs can work in multi-hop mesh topologies. To use of this technology we want to establish a global connectivity and control of the patient. In this system have one more good things is that it have mobility so the service provider also get the exact location of patient [2, 5]. The members of the IETF 6lowpan working group have developed a methods for compressing and uncompressing IPv6 [4] headers as they enter and leave IEEE 802.15.4 networks. 3.1 Neighbor Discovery The address of the parent current node (AP) is calculated by AP = [(AC - 1) / MC], where AC is the address of the current node and MC is the maximum number of children. Firstly current node determines ascendant or descendant of the destination node. After that if node receives packet then its forward to neighbor. For the calculation of next hop node have three cases such as if C is the member of SA: next hop node is AA (DC+1, D); if C is the member of SD: the next hop node is AA (DC-1, C); otherwise: next hop node is AA (DC-1, C). Where SA is the set of the ascendant nodes of the destination; SD is the set of the descendant nodes of the destination; DC is the depth of the current node; D is the destination; AA (D, k) is the address of the ascendant node of depth D of the node k; DC is the depth of the current node; C is the current node;
then the packet will stop forwarding. Originator address is the link-layer address of the originator while the final address is the link-layer address of the final destination. On-demand multi-hop routing using routing table and EUI-64 interface identifier in a 6lowpan networks. Hierarchical routing (HiLow) in 6lowpan can dynamically assign16-bit short address in MAC layer for reducing over-head of maintain routing table. In a PAN network, 6lowpan node (parent) broadcast PAN-ID (16- bit short address) to its neighbor node (child) for association. Each node maintains his neighbor table for communication between nodes. 3.3 AODV (Ad-hoc On-demand Distance Vector) The modified AODV routing protocol is created for only active nodes and it does not maintains all routes to other nodes. The use of sequence number at each destination is to maintain freshness of routing information. It reduced periodic broadcast and the paths generated are loop-free. Its use only symmetric links if a link is not symmetric it is not up and it works both on wired media and wireless media. The algorithm broadcast root discovery packets, only when necessary. It distinguishes between local connectivity management and general topology maintainers. It disseminates information about changes in local connectivity to neighboring mobile nodes that may need information. 3.3.1 Modified AODV Header Format The modified AODV protocol has route request table for route discovering. Its have various route request information until a route is discovered. 1. Route request ID has a sequence no. for identification of particular RREQ due to conjunction of originator. 2. Originator and reverse root address has 16 bit short or EUI-64 link layer address 3. Forward and Reverse route cost is an accumulated link cost along the forward route from the originator to the current node through which a RREQ is forwarded. 4. Valid time of the expiration or deletion of a route in milliseconds.
3.2 Mesh Addressing & Header Format In mesh header, first bit is ‘0’ and a second bit is ‘1’. The third (V) and fourth (F) bit, where V is original address, and F is final address then ‘1’ is (neighbor) short 16-bit addresses and ‘0’ is EUI-64. Figure 5. Route request (RREQ) message Figure 4. Mesh addressing type
The 802.15.4 broadcast addresses are defined as 16-bit short addresses in mesh layer because “V” and “F” bits is the mixture of 16 or 64-bit addresses. The 4-bits Hops Left field should be decrement packet every time before sending this packet to its next hop so the Hops Left is decremented to zero
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Figure 6. Route Reply (RREP) message
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4
Figure 7. Route Error (RERR) message
The figure (5, 6 and 7) shows the modified header format of AODV protocol. 3.4 DYMO-low (Dynamic MANET On-Demand)
Simulation Work & Results
We assumed 10 6lowpan nodes their some of cluster head and one is PAN coordinator or gateway. Each node connected to cluster head and has its own IP-address. The energy gateway is very much because it is connected to the fixed power supply. We used table 1 parameters for Network Simulator (NS) 2.33. The simulation time is 120s for a transmission range of every node is 14m. The frame error and packet rate is controlled and directly related to the delivery rate. Table 1. Simulation Parameters
It is a Proactive routing protocols, which is constantly update the route information is not suitable for use. This is because devices used in USNs are low power and limited processing capabilities. Besides that, some devices are move around, added or removed, causing frequent changes in the network topology and require more devices that are capable. Thus, reactive protocols AODV method, which is allowing nodes to find a route only when needed, is introduced. DYMO is introduced based on modification on AODV. DYMO provides simple and yet efficient to implement routing protocols. DYMO is based on UDP packets over IP and it work with IPv6 stack. With IPv6 stack is implemented in routing protocols, the IPv6 stack will give much heavier memory and processing requirement. DYMO-low routing protocol operate directly on the link layer, instead of using IP-layer. Thus, routing is performed on hardware address. A small routing table is used in DYMO-low implementation to store known routes. DYMO-low main interface consists of a nextHop command. This command is used for the purpose of return to the next hop to the destination on the route. In order to obtain the necessary hardware address for routing, latter will need to perform address resolution. Thus, it makes integration into 6lowpan stack even more difficult.
Parameter Transmission Range Simulation Size Topology size No. of 6lowpan nodes No. of PAN co-coordinator Traffic Type Packet Type Packet Size Power Loss Max. speed
Values 14m 120 s 50*50m 10 1 cbr 15 packets/s 36 byte 0.28J 2m/s
The traffic type is constant bit rate. The Repeat Request (RREQ) packet size is 36 bytes, which is the same size because these are control packets. Their frequency of transmission is depending on the traffic of the network. We compare the performance of route discovery node in limited time interval with the help of routing protocols AODV, LOAD, DYMO-low. We can see in figure 8 the performance of the LOAD and modified AODV protocols. LOAD protocol packet delivery ratio is less then modified AODV 0.4 to 1second time interval.
3.5 LOAD (6lowpan Ad-hoc On- demand Distance Vector) It’s a reactive routing protocol that is based on AODV, which is similar to DYMO-low. It was designed to run on IEEE802.15.4 networks, with the purpose of reduce unnecessary of complex implementations and resources usage. Similar to DYMO-low, LOAD uses link layer to keep track of the state if connections between the nodes. It reduces the recourses usage because it does not need to send periodic messages. Besides that, similar to DYMO-low, the implementation of LOAD uses the getNextHopcommand. The purpose of this command is to find the next node to the given destination on the route. This command also returns the node if and only if the command is available in the routing table. One important point, which is contrast with the DYMO-low implementation, is route discovery mechanism is not started automatically if the command is not available in the accumulated routing table. Thus, this making the component slightly more complicated, however, it is similar to other routing protocols.
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Figure 8. Packet delivery ration between AODV and LOAD
Figure 9 we can see the performance of modified AODV and DYMO-low protocols. DYMO-low protocol packet delivery ratio is less then modified AODV in 0.4 to 1 second time interval.
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Figure 10. 6lowpan packet delivery ratio on gateway
Figure 9. Packet delivery ratio AODV and DYMO-low
Figure 8 and 9 we can see modified AODV protocol more constant performance compares of LOAD and DYMO-low in time interval 0.4 to 1 seconds but it’s at the time interval of 1.0 to 1.2. However, for LOAD and DYMO-low protocol, packet delivery reduces at time interval 0.6 to 0.8.
Figure 9. PDR comparatively of AODV, LOAD, DYMO-low
In conclude both LOAD and DYMO-low protocols gives slightly same performance in compare to modified AODV. However, modified AODV protocol is more reliable compare to LOAD and DYMO-low due to constantly high delivery rate at the time interval 0.4 to 1.0 seconds. DYMO-low gives the highest packet delivery of 0.8 and LOAD gives 0.83 but modified AODV goes to highest at 1.0. For our global health information system we need more reliable data so the modified AODV protocol is more reliable and secure data delivery ratio in compare to others. 4.1 Real-Time Test-bet We use three IP-USN nodes and one gateway. In figure 10 shows the test-bet of three nodes. In this paper we used dummy biomedical data for testing of modified routing protocol performance between 6lowpan nodes. We can see IP-addresses of each patient and it shows the performance of data transmission on gateway. The IP-address shows identity of the patient and sequence-ID shows packet transmission on node. We can see the performance of the modified protocol on the gateway sheet.
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5. Conclusion & Future Work In this paper we presented the global healthcare monitoring technique and recovered wearable biomedical signal due to the various condition motion artifacts. In this system service provider can easily monitor his patient form anywhere with the help of service provider equipments. For this technique we modified AODV protocol to make more secure and reliable biomedical signal. We proposed routing technique for neighbor discovery mechanism. We show the comparison of various 6lowpan routing protocol for healthcare monitoring and provide our modified AODV protocol performance is better then other two protocols for our applications. In this paper we shows real-time test bet. We used dummy biomedical data for testing of modified routing protocol performance between 6lowpan nodes. For future work we going to test real time health monitoring application such as ECG, PPG, Temperature etc. and then analysis of biomedical signal and try to make more secure of protocol. REFERENCES [1] Jin, Ho, Kim, Choong Seon Hong and Taeshik Shon. “A Lightweight NEMO Protocol to Support 6LoWPAN” ETRI Journal, Voume 30, Number 5 October 2008 pages 685-695. [2] Chris Ottpo, Aleksandar Milenkovic, Corey Sanders Emil Jovanov “System Architecture of a Wireless Body Area Sensor Network for Ubiquitous Health Monitoring” Journal of Mobile Multimedia, Vol. 1, No.4 2006 pages 307-326. [3] Aymab Sleman , Reinhard Moeller “ Integration of Wireless Sensor Network Services in to other Home and Industrial networks” IEEE, October 6, 2008. [4] N. Kushal Nagar, G. Montenegro, C. Schumacher, “Transmission of IPv6 Packets over IEEE 802.15.4 Networks” RFC 4944, September 2007, pp-1-30. [5] Gilman Tolle, “A 6LoWPAN application environment,” ACM SenSys’07, Sydney, Australia, 2007 pp. 375-376. [6] C. Gomez, P. Salvatella, O. Alonso, J. Paradells “Adapting AODV for IEEE 802.15.15.4 Mesh Sensor Network: Theorerical Discussion and Performance Evaluation in Real Environment” IEEE WoWMOM’ 2006.
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