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A wireless architecture for telemedicine

Martin Krohn, Heiko Kopp and Djamshid Tavangarian

University of Rostock

Institute of Computer Science

Chair of Computer Architecture

Email: [email protected]: [email protected]

Email: [email protected]

Abstract In respect to the demographic change, currentlytaking place in Germany, especially in the federal state ofMecklenburg-Vorpommern, the project AGnES was startedby the University of Greifswald (Faculty of Medicine) and theUniversity of Rostock (Faculty Computer Science and ElectricalEngineering). The project aims to develop an infrastructurehelping to assist physicians. The essential of the project is theCommunity Medicine Nurse (CMN), performing home visits,physical examinations and monitoring of patients. During the

examinations the CMN is in contact with the supervising familydoctor. Therefore, a data connection transmitting telemedical,audio and video data has to be established. Our work handlesan automatical antenna positioning system designed for themobile WiMAX subscriber stations, which are part of thecommunication architecture.

I. INTRODUCTION

In Mecklenburg-Vorpommern, a federal state of Germany

with a low populousness, the population is heavily regressing

since the reunion of Germany. The demographic change of

an increasing average age currently taking place in Ger-

many intensifies this development [1]. In this environment a

home doctor is often responsible for constantly growing areas

of medical care, thus the patients often have to deal with

long distance approaches. Furthermore, a prognosis (figure

1) predicates that until the year 2010 about one third of all

physician will retire. This is partly substantiated by the age

structure in Mecklenburg-Vorpommern. Nowadays, there are

physicians, unable to find a successor [2]. In conclusion a

further expansion of the medical care ranges is very likely.

Fig. 1. Prognosticated Age Structure of Home Doctors in Mecklenburg-Vorpommern; Source: KV M-V 2003; Diagram: Institute of CommunityMedicine, University of Greifswald

The long distance approach to the family doctor is mainly

an issue for older people because of mobility restrictions. They

are dependent on the help of family members or the use of taxi

or patient transport companies. A physical examination within

a home visit of the physician is only acceptable in exceptional

cases, thus otherwise the doctor would spend a large amount

of time on driving to the patients.

The main idea of the AGnES project is that a CommunityMedicine Nurse (CMN) will visiting the patients and support

the home doctor. The CMN is a specifically trained and skilled

nurse performing activities of prophylaxis, counseling, caring

and therapy-supervising. For these activities the nurse can

utilise the telemedicinical equipment designed and developed

in the AGnES project.

Additionally, our approach depicts the requirements for the

WiMAX antenna positioning system as result of the special

data communication infrastructure used when transmitting

telemedical data.

I I . NETWORK ARCHITECTURE

For the data communication between the CMN, the pa-tient and the family doctor, the availability of relative high

bandwidth is the neccessary. It can not be guranteed that

all patients have broadband access to the Internet or a low

bandwidth Internet connection like ISDN or Modem. The use

case implies a mobile operation, which can be implemented

by using wireless network technologies. In respect to the large

supply radius of the physician, the network has to be available

over large distances. Concurrently, the bandwidth needs to be

constantly at a relative high level of at least 3.0 Mbps.

WiMAX-Networks (Worldwide Interoperability for Mi-

crowave Access) [3] were introduced with the adaption of

the IEEE 802.16 standard in 2001 as wireless technology for

Metropolitan Area Networks (MANs). The IEEE 802.16-2004standard [4], adopted in 2004, contains many complements

and unites several proprietary solutions. Devices according to

the standard provide bandwidths of 40 MBit/s and ranges up

to 10 km. The devices are portable but not handy. Currently,

WiMAX is not supported by the CMNs equipment. Thus

the exclusive use of WiMAX for the implementation of the

AGnES-architecture is not feasible. The requirement of mo-

bility leads to a combination of WLAN and WiMAX presented

in figure 2.

1-4244-0871-7/07/$25.00 2007 IEEE

4th WORKSHOP ON POSITIONING, NAVIGATION AND COMMUNICATION 2007 (WPNC07), HANNOVER, GERMANY

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Fig. 2. Architecture of the WiMAX/WLAN network

The WiMAX point-to-multi-point infrastructure supports

connections of several subscriber stations. The WiMAX base

station is installed at a fixed place at the doctors practice. The

mobile nurses visiting the patients uses a WiMAX subscriber

station to establish a connection to the base station. As theWiMAX subscriber station is portable only in a limited way,

a WLAN-802.11g access point spanning a cell is connected

to the subscriber station. The WLAN enabled Tablet PC of

the nurse to connect to the access point and thus allows

connections to the PC in the doctors practice.

The WiMAX antenna of the subscriber station always has

to be optimally aligned with the antenna of the base station.

For the daily use of the system its usage must be easy and

straight forward. Thus, it is unacceptable to adjust the antenna

manually. As a solution, a automatical positioning system will

be described in the next section.

III. THE POSITIONING SYSTEM

The adjustable antenna is mounted on the car of the nurse.

With GPS and compass information, a PDA calculates the

target direction for the WiMAX subscriber antenna. The

following section describes the system design in detail.

a) PDA: The central element of the positioning system

is the PDA (figure 3). It collects all necessary information

regarding the geographical position, the point of compass,

and the WiMAX signal quality. The PDA is connected to the

subscriber station via a connection to the WLAN access point

receiving information about the WiMAX signal quality. Fur-

thermore, the PDA uses a bluetooth connection for accessing

the GPS module. The connection to the compass system isestablished via a serial interface.

The PDA software collects the positioning data from both

the compass and the GPS module. The geographical position

of the doctors practise is stored in the PDA memory during

the initial setup. Based on this data the target direction of the

antenna is calculated. For the first attempt of adjustment the

optimum target direction for the antenna will be calculated

by taking the linear distance as a basis. With information

concerning the accuracy of all measured data a small sector

Fig. 3. Positioning system

where the optimum lies in is calculated. The software will

scan the sector for the best connection quality. If the signal

quality lays over a configurable threshold, the positioning is

completed after 2 seconds.

If the signal strength is not sufficient to establish a connec-tion of the demanded quality the scanning sector is set to full

360. This ensures that possible wave reflections are utilised.

To ensure that the scanning is done in an adequate amount

of time, we implemented an algorithm using successive ap-

proximation. At first the full circle is divided into 8 sectors

of each 45. The position with the best signal is used as the

start point for the algorithm. The first 45 sector where the

start point lays within will be subdivided in smaller sectors.

The adjustable values for the sector sizes were chosen on the

basis of the properties of our antenna. If there is no sufficient

signal strength available at the current position of the car, the

algorithm terminates with a negative result after 256 seconds

of scanning.The PDA software provides a Graphical User Interface

(GUI) for configuration tasks and information about the

WiMAX connection quality. If the signal quality is still under

a usable level the nurse will be advised to move the car to

another position.

b) Microcontroller module: The mircocontroller (C) is

used as an abstraction layer from the motor control protocol.

The serial interface supports the submission of angular dimen-

sions. The C responds with a positive acknowledge when

the motor has been adjusted. Due to the use of the C we are

able to connect various motors with different interfaces. Servo

motors, stepping motors and DiSEqC [5] motors are supported.

The module can be equipped with different drivers.

IV. CONCLUSION

The networking architecture consisting of WLAN devices

for the use in the close-up range in the patients homes together

with the long distance WiMAX technology are suitable for the

AGnES project. During a field test the whole system will be

tested and evaluated by the medical staff. With the help of

the positioning system the usability of the data transmission

architecture is greatly increased.


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REFERENCES

[1] Raumordnungsbericht 2005, Bundesamt fur Bauwesen und Raumord-nung (BBR), 2005, http://www.bbr.bund.de/.

[2] Sozialministerium und Kassenarztliche Vereinigung prasentieren Master-plan zur Sicherung der arztlichen Versorgung, Gemeinsame press releaseof the ministry of social Mecklenburg-Vorpommern and the associationof panel doctors Mecklenburg-Vorpommern, August 2005.

[3] IEEE 802.16a Standard and WiMAX Igniting Broadband WirelessAccess, Worldwide Interoperability for Microwave Access Forum, WhitePaper.

[4] 802.16-2004 Standard for Local an metropolitan area networks Part16: Air Interface for Fixed Broadband Wireless Access Systems, IEEEStandard.

[5] Diseqc specification, Eutelsat, Internet prese nce,http://www.eutelsat.com/satellites/4 5 5.html.


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