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Wireless Sensor Networks is a significant technology that has a considerable attraction in many areas, particularly in health sector. On the other hand wireless mesh networks, which are an extension of LAN, have far better range and also reduce the amount of cabling needed to connect to the backbone network. In this paper a scheme that is Wireless Sensor based Mesh Networks, which is an integration of the above two technologies has been proposed.
This scheme also incorporates agent technology in its functioning. A hierarchical agent based layered architecture of this scheme, meant for health applications, have also been discussed. The functioning and the coordinating roles of the agents - both static and mobile, in such architecture have been fully explained and the implementation of the scheme for healthcare application has also been presented.
Wireless sensor networks (WSN) are a significant technology attracting considerable research attention in recent years. They are being developed for a wide range of civil and military applications, such as object tracking, infrastructure monitoring, habitat sensing, and battlefield surveillance. Recently it has started attracting attention towards the health industry for monitoring the health of the patient. Typically, a WSN consists of hundreds to thousands of tiny sensor nodes that communicate over wireless channels and perform distributed sensing and collaborative data processing.
Wireless mesh networks (WMN) are multihop networks of wireless router platforms. The wireless routers are typically stationary, but the clients can be mobile. A mesh network can provide multihop communication paths between wireless clients - serving as a community network or as a broadband access network for the Internet. WMN are considered cost-effective alternatives to wireless LANs, as there is no necessity to deploy any wired infrastructure to support a mesh network. A number of routing protocols like Dynamic source routing (DSR), Adhoc on Demand distance vector routing (AODV) have been implemented for Adhoc and Wireless LAN Networks.
An attempt has been made in this paper to evaluate the performance of AODV routing in wireless Mesh Network and compared against the legacy 802.11 Adhoc and Wireless LAN in terms of Route overhead, delay, MAC delay and throughput for wireless Internet connectivity application. It is now possible to construct what is called a Wireless Sensor based Mesh Network for various applications. The sensors being low powered and low memory devices can transmit the information to the nearest mesh nodes and these mesh nodes can use multihop routing to transmit the information to the backbone networks like the PDA or the servers. With this as background, architecture, for the health care monitoring application, using sensor based mesh networks employing agents has already been proposed. In the architecture so proposed, we conceived mesh nodes being deployed over each hospital building. But with the increasing number of wards and patients inside each hospital building, the mesh node would get overloaded with information from the body sensors from the patients and also the traffic from the doctor's handheld device. Taking this aspect into consideration we now propose a decentralized hierarchical intelligent agent based architecture. This architecture employs two types of intelligent agents, that is static and mobile agents. The static intelligent agents in this context stay within the ward of the hospital zone and the mobile intelligent agents move out of ward/hospital zone to convey the appropriate message to doctors. The details about this modified hierarchical intelligent agent based architecture scheme and the co-coordinated functionalities of the agents therein, have been explained in this paper. The remainder of this paper is organized as follows. Section II discusses about Wireless Sensor mesh networks. Section III discusses about information routing in wireless sensor mesh networks and on the appropriate scheme that could possibly be used in our architecture. Section IV describes the proposed hierarchical Intelligent Agent based mesh network architecture having application in the healthcare monitoring sector and the details on the co-coordinated functionalities and the routing of the agents in the proposed scheme. Section V shows the implementation of the scheme in health care that is Maternity application through PDA using J2ME and section VI is the concluding section.
II. WIRELESS SENSOR BASED MESH NETWORK
A. Wireless Sensor Networks
A wireless sensor network (WSN), in general, is a wireless network consisting of spatially distributed autonomous sensors to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants, at different locations and health care applications. Each node in a sensor network is typically equipped with a radio transceiver or other wireless communications device, a small micro-controller, and an energy source, usually a battery. A sensor network, normally constitutes a wireless Adhoc network, and supports a multi-hop routing algorithm. The base stations are one or more distinguished components of the Wireless Sensor Network (WSN) with much more computational, energy and communication resources. They act as a gateway between sensor nodes and the end user.
Fig.1. Wireless Sensor Network
It may be mentioned that low-power wireless communication technologies like Zigbee (IEEE 802.15.4), low-power Bluetooth, etc. have enabled the development of small, body-wearable, wireless sensors network for patient monitoring. In one such architecture, the Sensors can be configured to form a Wireless Body Sensor Network (WBSN) and enable monitoring of multiple physiological parameters (such as ECG, Blood Pressure, etc.) of multiple patients at a central location. Each body-wearable sensor, known as a Bio-Front End device (BFE), is composed of a sensor for physiological signal sensing, the related front-end electronics hardware, a low-power microcontroller for data acquisition and a wireless transceiver for data transfer to the receiver. There can be multiple BFE devices connected to a patient for monitoring multiple parameters. Normally an aggregator (AGG) device worn by the patient performs the function of receiving the wirelessly transmitted data from multiple BFE devices connected to a patient and transmits the aggregated data to a backend PC or server. The AGG device can be a device like a Portable Digital Assistant (PDA) or a scaled down version of that without a Liquid Crystal Display (LCD). The AGG and the BFE devices form a localized WBAN, with each BFE device having a unique device ID. The network system including WBAN is normally comprised of energy constrained nodes.
B. Wireless Mesh Networks
Wireless Mesh networks integrate two network architectures - Adhoc and Wireless LAN. The wireless infrastructure access points provide the connectivity to the wired backbone. Each node in the network is both a service provider and service consumer. The difference between Mesh Network and conventional infrastructure wireless LANs is the fact that mesh networks result in a multihop technology, which requires decentralized coordination. Wireless Mesh Networks are composed of three distinct network elements.
• Network Gateway: One or more gateway can be deployed to allow access to different IP sub network especially wired infrastructure.
• Access Points: The access points from wireless backbone providing connectivity in places otherwise difficult through traditional wired infrastructure. The wireless communication between the access points can use different technologies such as IEEE 802.11 a/b/g or IEEE 802.16 and different hardware (directional or omni directional antenna).
• Mobile Nodes: Any device embedding wireless capabilities like Sensor nodes, PDAs, laptops can access the network gateway through direct or multihop communication using access point as relays.
Fig.2. Wireless Mesh Network
C. Wireless Sensor Mesh Networks
We have seen that Mesh Networks which is 802.11S - an extension of Wireless LAN can cover the entire city and use multi hop routing in communication with very minimal amount cabling used at the backbone. The nodes in mesh networks can be mobile which can be a PDA, PC or laptop and even wireless sensor networks. The mobile nodes which in our case wireless sensor networks can transmit the sensed information to the nearest access point i.e. mesh node and which use multihop routing to transmit the information to the wired network or even mobile devices like PDA or laptop. An integration of these two technologies is Wireless Sensor based Mesh Network.
III. PATIENT MONITORING USING WIRELESS BODY SENSOR MESH NETWORKS
A. Conventional System
In the existing system, as shown on Fig.3 the patient's status is looked up and taken care by some person who has to sit near the patient itself. It is difficult to keep each person for each patient. Hence there is a need of automatic monitoring technique for patients.
Fig.3. Conventional System
B. Proposed System
In the proposed system, the patient's temperature, heart beat and pressure is monitored automatically. The bio-medical kit is connected with the patient. From the kit the information is passed to the centralized server through LAN. The centralized server monitors all the wards that are present in the hospital. From the centralized system, the information is passed to the MESH network through ZigBee technology. The SMS is sent to specified doctors through GSM connection from the MESH network. With the help of the information got through SMS, the doctors can be able to attend the patient very quickly. Since the monitoring is done automatically there is no need for any person to look after the patient. The mechanism is well described in the Fig.4 and the corresponding data flow diagram is given in Fig.5.
Fig.4. Proposed System
Here we here have proposed two Agents: One static Agent and the other the mobile Agent. The static agent is responsible for the following tasks: acquisition of data from the required body sensor node, filtering of inaccurate and unwanted data, aggregation and processing of useful data, and transmission of the desired results.
The mobile agent would deliver the health data so received from Sensors to the mobile phone. With the help of GSM Modem the information from sensors about the health status of the patient is sent to the mobile phone of the doctor through the mobile agent. Based on the received information, the doctor would attend to the patient immediately.
If Key is
Passes Information to Mesh Network
Fig.3. Data Flow
This paper pertains to Wireless Sensor based Mesh Networks and a middle ware - mobile agent and how it can be implemented on such a system for healthcare monitoring. Also in this paper we have proposed a decentralized hierarchical architecture employing Agents for health care monitoring through informing the concerned doctor. The next step in this research is to develop interactive agents using Embedded C that would follow the policies and rules
for intimating the doctor depending on patient's health condition. We would also be concentrating in future on the management of the sensor based mesh networks in terms of agent co-ordination, framework of policies to be followed by the agents and validation of the system concepts.