A NOVEL LOW COST TELEM EDICINE SYSTEM USING
WIRELESS MESH NETWORK
E. Supriyanto' , H. Satria 2 , l.H. Mulyadi2 and E.H. Putra!
1 Faculty of Biomed ical Engineerin g and Health Science
2 Faculty of Electrical Engineering
Univers iti Teknologi Malaysia
AB ST RACT
Teiemedrcme pronuses a n improveme nt o f he alt h CMe
ser vice qualrty in ru m I, urban. d ense and mob ile are as . In
orde r 10 implem ent the tclc mcd icinc in these areas, a lo w
cost rclcmcd icmc system w ith acceptable quality for
med ica l data transfe r is required. Th is parer disc usses
simula tion and implementation results o f a low cost
rclc mcdicinc sys tem incl uding wireles s med ical interface
and com munication infrastructu re. A simul ation has been
do ne to investiga te the netwo rk quality o f service. Th e
infrastructure has bee n a lso imp lemen ted usi ng low cost
5.KG Hz transceiver for backhauls and low cost 2.4 GH z
tra nsce iver fo r cl ien ts. Te st resu lt sho ws that the low cost
rcle mcdici nc sys tem IS able to do rce t time
communica tion be tween patie nt and medical staff with
medic al da ta rate up to 2 M bps . It s ho ws tha t the low cos t
tclemcdicine sys te m usi ng wi re le ss mes h ne two rk can be
impleme nted in remot e ar ea with acce ptab le med ica l data
transfer qu al ity.
1. INTRODUCTION
Tclcmedicme is an em erging techno logy wh ich
cornbimng
te leco m municatio n
and
information
techno logy fo r medic a l practice. It gives a new wa y to
deli ver health care services w he n the d ista nce be tween
do ctor an d pa tie nt is sig n ifica ntly a way. Tclemcdic ine
can deli ver hea lth care services to the pa tie nt even in
re mote area,
Pavlopoulos ct a l. (19 9K) has present ed a n e xample o f
telcrncdic mc adva ntage
with im plem en tati o n on
ambulatory pa tien t ca re at rem ote area . A nother
application ha s bee n done by Sudhamony er al. (200K) for
cancer ca re in rural are a. Il igh techno logy tcle medicme
app licat ion in surgery has a lready bee n de veloped by
Xiaohui er at. (200 7).
C urrent ly. the telc med ic ine uses ava ilable wired a nd
wirel ess infras truc ture s. Tclemcdicine infra st ruc ture s
-
with Wired netwo rk have been pro pose d by Al-Ta er
(200 5 ) usmg Integrated Servi ce Dig ital Network (ISD N).
Asy nchron o us Tr ans fer Modes (A T M ) by Ca bral & Kim
(1 996). Vel)' S mall Apertu re Tcrrmnat (VSAT) by
Pandian ct al. C~ 007) and Asy mme tric Digital Subscriber
Line (A DS L) by Ling ct al. (20 05) . Tclc mcd ie ine has also
been imp leme nted lt1 wireless net wor k using Wire less
LAN (W LA N) proposed by Kugean er al. (2002).
Worl dwide lntcro pc rabihty fo r M icrowave Acces s
t W IMA Xj by Chorbcv cr at. (2 00R). Co de Division
M ultiple Access (CD/lil A ) IX-EV DO by Yoo ct al
(200 5 ). G enera l Pack e t Radio Sw itc h (GPRS) by Gi bso n
cr al. (2 003) and 2G G roupe Specia l Mob ile (GSM ) by
Pavlop onlo s cr at. ( 199!!).
Each infrastructu re has its OW I1 obstacle. 111
particularl y when they arc im plement ed in a remote area.
Fo r exam ple. As ynch ro nous Tran sfe r Mode (ATM) and
M ulti Pro to co l Label Sw itch ing ( M PLS) had some
mobil ity a nd sca labili ty hrnitatrun, even bot h networks
pro vide h ig h Q uality o f Se rvice (Q oS) and have stability
o n deliv er ing data [Na nda ct al., 2007) . Thc frag.ility o f
3G U t\1TS ne two rk tor tele rncdtcinc has bee n explored
by Y. E. T an et <I I. (20 06), whe re the im ple men tation
costs arc high and do es nOI prov id e enough Q oS
Com pa rison o f ava ila ble net wo rk infrusnuc nrrcs and
tech no log ies fo r rclcmcdicin e sys tem are su mma rized in
Table I. It can be shown that based o n cost. data rate a nd
mobility. the optimal solution fo r tetcmcdicinc system is
Wireless Mesh Netwo rk ( WM N).
In orde r to inves tigate the qua lity and the possibil ity
o f U:-'JIlg W MN as a rclcmedicinc in fra struct ure, a
sim ulatio n of d ata co mm unicat ion in WMN using NS2
ne twork simula tor has been done. Bes ides , the
infrastructure and the med ical dat a interface have been
als o develop ed and tested. Th is is req uired to create a low
cost tclcmedicin c sys tem that has an acc eptable q uality o f
service.
382 -
Ta ble I Com parison of available network infrastrnctures/teclmologies fo r te lerncdicine system
bit rate
investment cost*
operat ional cost
user device
mobility
infrastructure!
tcchnology
(Mb ps)
~c:.:::
o~
s t:--:---:-:-__
2.550,OOU
H
M
VH
No
Fiber Opt ics
155
VH
H
VH
No
ATM
8
H
M
M
No
ADSL
0.J28
H
M
M
No
ISDN
4.09
VH
M
VH
No
VSAT
0.115
H
L
L
Yes
GPRS
0.256
H
L
L
Yes
EDGE
0.5 12
H
M
M
Yes
3G UMTS
3.6
VH
M
M
Yes
HSDPA
54
L
VL
L
Yc s
WMN
Yes
54
M
VI.
L
WiMAX
Note:
" investment cost =
cos t o f investment
numbe r of user node thai can be servi ced
VH = very high. H=h igh. M=mediull1. L=low. VL=-vcry low
2. MEDICAL QUALITY OF DATA AND SERVICE
An application example of telemedicine system can
be seen in Fig. I . It involved patients and doctors that are
equipped with medical data assistant (MDA). Thc MDA
acquires thc medical data using Medical Data lnrcrfacc
(MDI). MDI retrieves med ical data from various medical
dev ices. Typical medical dev ices arc electrocardiography
machine (ECG). Doppler instrument, blood pressur e
mo nito r, ultrasound machine and stethoscope. T he MDA
are connected through wireless router and tran sceiver for
data transmitting between patient and doctor. Two -way
communication between patient and doctors is supported
by camera and microphone. All of patient medical data
are continuously recorded inside the server for diagnosuc
purposes.
......
C OfMmu n
tt(ll1
11I1r1l trllC.lure
For this application. the muurnum data rate for
accep table (good) quality and excellent quality arc listed
in Tab le 2.
Ta ble 2 Desired ou tput data rate
devices
ood
ECG
Dopplcr Instrument
Blood Pressure Monitor
Ultrasound Machine
Camera
Stethoscope
Micro hone
Total
data rate
excellent
J 2 kbps
160 kbps
I kbps
400 kbps
2.000 kbps
160 kbps
160 kb s
2,893 kb s
T he nu nunum data rate for acceptable service in
tclerncdicinc system is 323 kbps, whereas for excellence
quality minimum data rate 2.893 kbps is required,
Up to now. there is no specific rule defining OoS
provisions of telerncd icine application. In addition,
parameter ized OoS is a clear OoS bound which arc stated
in terms of quantitative values such as throughputs. end
delay, j itter and packet loss. T hese OoS bounds arc
explained in Table 3.
3. WIRELESS
MESH
NETWORK
TELEMEDICINE SYSTEM
FOR
Hardware configura tion for low cos t telemedicinc
communication infrastructure is shown in Fig. 2. This
infrastructure is divided into three areas of
implementation: client and indoor network, backhau l
outdoor netwo rk and medical central service.
Fig. I An application example of low cost
telcmedicine sys tem
383 -
Table J OoS fo r low cost tclc mcdic ine sys tem
dcflninon
packet arr ival rate
the tunc taken by a packet to reach its destination
lime of ar rival de viatio n between packe ts
pe rce ntage of non-rece ived data oackcts
_ _--cParameler
throu ghput
del ay
jitter
packe t loss
CLIENT & INDOOR
OUTDOOR NETWO RK
- rJ.,'? V ~ w "V ._.
._. IV
._. IV -·~-~
"ve
._.
v
"v
-,~.
~
Q]
max 5%
CEN TRAL SE RVICE
~
()
C)
C;)
requncmeur
min 323 kbps
max 100 rns
max 50 ms
";::>
(j
(IA.... . ." . I
M'
APPlICATION
. ~.
~
OA'AD.\af
K~'
~
Q]
,~ .
Fig. 2 Hard ware co nfig uration for low cost tclcrncdic mc co mmu nication infras tructure
In indoor netw o rk, a wireless router is con nected to
medi cal dev ices through MOl a nd co nnected to outd oor
network via switch. Outdoor netwo rk is ma in structure of
wireless mes h netw or k. T his co nfiguration enables a
communicat ion between client and ce ntral service or
medical doc to r via Doctor-Med ica l Data Assistan t ( 0 MDA). T his enable s a lso mobile co mmunica tion bet wee n
patient and medical doctor.
C hara cteristic of WMN ou tdoor backhau l arc
desc ribed in Tabl e 4 The operational frequenc y of 5.750
GH z has bee n used to o vercome dist ance a nd obstacles
between backhaul co nnectio ns. Parameters for the W~lN
indoor rout e r are de scribed in Table 5. T he o peratio nal
freque ncy of WM N indoor route r is 2.470 G Hz.
Table 4 WMN ou tdoo r bac khaul cha rac teristic
va lue
Parameter
a ntenna
T ype
di rection al an tenna
10 dBi
ga in tra nsm itter
10 d Bi
ga in rece iver
- 100 d Bm
rece iver sensitivi ty
20 km
_
line of sig ht ra nge , -, -_ _ -""-'''''
7
network interface
I W
input powe r (max)
cha nnel freq uen cy
5.750 GH z.
data rate
54 M b p ~
-
Ta ble 5 WMN indoor ro uter characte nsnc
Parame ter
value
anten na
Ty pe
om ni dire ction al
ga in tran smitter
1 dR i
ga in receiver
1 dBi
-104 d Rill
rcceiv er se nsiliv i'l:
network inte rface
input pow er (ma x)
IO mW
11 Mbps
data fate
channel frequency
2.470 GHz
NS2 versi o n 2.33 network simulato r has been used to
simulate the OoS pa rameter incl udin g delay, thro ugh put.
j itter a nd pac ket loss. Three pro tocols have bee n
imple mented in the simulation. The si mula tion method
and results are reported by Supnyanto et al. (2001l). Fig.
3 s hows throug hput as functio n of hop number.
Simul ation result shows variatio ns o f throughput for eac h
rou ting pro toco l. T he biggcr hop number, the sma ller
through put. II is due to del ay and wai ting lime in rou ting
mec han ism. DS[) V routi ng protoco l inferred its
throughput better tha n the othe r pro tocols. Si mulat ion
resul t s hows that the network able to tra nsfer the medical
data up to 2 Mbps, eve n still more than 200 kbps for 6
hops. This result shown the a bility of network to fulfill
the qood qua lity medical data transfe r rcqurremcr u.
384 -
to the patient and MDlzb. Tab le 6 shows MOlz
characteristics. M Dl zb bas the same operational
frequency as MOlz, but the modulation is slightly
different. Table 7 shows MDlzb characteri lies.
I,
~ - --.
Tab le 6 MD1zcharacteristic
Va lue
parame tcr
Antenna
type
ornni antenna
ga in transmitter
I dBi
gain receiver
I dBi
receiver sensitivity
-92 dBm
indoor cove rage range
30 m
100 m
line of sight ranee
Zi bee module
2.4 11 UHz
channel frequency
bandwidth
1.359 MHz
data rate
115200 bp
•
1 \
Fig. 3 Throughput com parison of each routing protoco l in
EPT system .
4. W IRELESS MEDICAL INTERFACE
In order to enable the connec tion belween common
medical devices and network infrastructure. a wireless
medical interface has been deve loped. The wireless
medical interface is implemented using Zigbec and
Bluctooth techno logy .
Two kinds of wireless medical interface has been
developed; MOlz and MDlzb. MOlz is a dev ice which
acquires data from medical device and transmits it out
through Zigbce network. while MDlzb coordinates the
Z igbcc network as well as com mun icates wi th Medical
Data Assistant through Bluetooth network.
Med ical data is acquired by M Dlz and then added
with a frame as shown in Fig. 4. The data is then
transmitte d to MOlzb through Z igbee nerwork. MOlz IS
ab le to send data up to 115200 bps. The bandw idth is
more than enough for vital sign darn. The network has a
PAN ID to differ with the other Zigbee networks.
~1
•
ZlgBee Comm
•j
Bluel oot h Co mm
" In,
l l1'l tJ. lu l. d ECC o. lo'l r..
~''' -
Table 7 MDlzb charac teristic
Value
paramete r
nienna
omni ante nna
type
ga in transmitter
I dBi
ga in receive r
I dB i
average power
-89 dBm
line of si ilu ran c
100 m
B lu etooth module
2.41 1 GHz
channel frequency
bandw idth
1.359 GHz
data rate
723300 bps
Fig. 5 shows block diagram of MOlz. Analog signa l
from medical sensor is conditioned, digitized and
processed by a processor. T he data from processor is
converted to Zigbcc and then transm itted out. The data is
arranged in a frame as shown in Fig. 6. II consists of
device 10 , status, length of frame. data and checksum.
The Zigbee module is bidirect ional. M 0 17 can rece ive the
command through Zigbce module.
\ 1 ,I> .t1
L tr l lMrr;lrt "'oItN IM P 0 YIl:_
~
..
I
/
~ I ,[) I, I J
t
11 ' I
-------,
.,
I~ ,
\ 'I\,h ll.1JIlJ
nul ';'I ){:
Fig. 5 ivID lz Block Diagram
I,"
III
T
"'1 It1
1&., ,-lh
t",u
l, r
I .t..
.. .
~
an
Fig. 6 Data Frame of MOlz
Fig. 4 Wireless medica l interface configu ration
The MD lz was design ed for short range
commu nication. betwee n the embedded dev ice attached
-
MDlzb coordinates thc Zigbcc network. It decides
which medical device will comm unicate to in that time
and give them priority based 0 11 their status,
Fig. 7 shows block diagram of MOlzb. II consists of
Zigbce module, two processors. D-Ialch, SRAI'v I, and
Bluetooth modu le. Data from MDlz is received by Zigbcc
module and processed by processor I. Delay may ignore
the data. To overcome this matter. a 256kb SRAM is
added as a data buffer. The data is then sent to processor
385 -
2 to add a frame as shown in Fig. 8 before transmitted out
by Bluetooth module. Bluetooth data is acquired by
mobile data assistant. The Bluetooth module is
bidirectional. MDlzb can receive the command through
Bluetooth module.
3
c
CI
;;.
di stance (m)
Fig. 10 MDlzb Bluetooth signal strength
Fig. I I shows the signal strength of communication
between P-MOA and WLAN router using WiFi
communication. Th is result shows that the cover of 10
meters still give high Signal to Noise Rauo (SNR) from
wire less router sensitivity.
Fig. 7 MDlzb block diagram
•• '
..., I I~
,
h~lf'
~I'
Hl
I
1* '.
1I1,.r
' 1.... l.
I tam
l Ull
1 n.1
Ihlo
Fig. 8 Data frame of MDlzb
(I
~ -s
~ · 10
0 . - I-
5. TEST ING AND ANALYS IS
T he testing has been done
10
'"
~
~
II
,
2
4
6
8
6
~5
:;:. , .0
-3':>
dist ance (01)
Fig. I I Wireless router WiFi signal trengrh
The network performance test result is shown in
Tab le 8. The measuremen t is done for backhauls I km
distance. The result show the noise rate varies from irs
receiver sensitivity. The average signal for each
backhaul in open space area with clear weather are in
range of -26 and -28 dBm. This gives the SNR values of
72 dB for low SNR and 82 dB for high SNR.
I)
&j
4
c
~ -:!O
investigate the network
performance and the rcliability of system including
wireless medical interface.
Fig. 9 shows the test result for MDlz signal strength.
iVI Dlz signal strength is the M Dlz power to receive the
data between receiver at medical interface and transmitter
at medical equipment commun ication using Zigbee
communication. It should be higher rather than its
receiver sensitivity (Signal Strength 2: R.'\ sensi tivity)
from the specification of ;'vIDlz, Test res ult shows that for
the distance up to 10 meters, the MOlz Signal strength
gives the result higher than its receiver sensitivity at -92
dBm.
-
2
11
.n
Fig. 9 iVI Oil signal strength
,
The measurement has also been done for the data
transmission between wireless medical interface and p,
MDA client. Fig. 10 shows the signal strength of
communication between medical inter faces through the
P-tvlDA client using Bluetooth communication.
Table 8 Network performance testing of each
backhaul at I km
noise noise
signal
band
Location antenna
high
low strength
(MHz)
(dBm) (dBm) (dBm)
I
5180
-26
Location
-9
-106
J
2
5180
-1 07
-28
-98
-26
Location
J
5180
-98
- 108
2
4
5180
-28
-97
- 108
Location
5
5180
-26
-98
- 106
3
5180
-98
-26
6
-106
The testing has been done to transfer the medical data
up to 2 Mbps. Test result shows the network is still able
to fulfill the minimum requirement stated in Table J with
excellent signal strength.
386 -
Table'l) COfU1CC'tlon char acte ristic per hop betwee n
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,
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CO NC LUSION
A novel low cost telemcdicine system us ing WMN
ha s been su~sfu lly developed and tes ted The svstcm
consists of wi~lC\s medica ! interface and commumca non
infrastructure.
T he ..... rrclcss medical interface using Zigbec and
B l uetocth technctogy has been im pleme nted 10 enable the
connection some mcdscal de vices to com munica tion
infrastructure. The communicano n in fras truc tu re has
been impleme nted us ing low COM 5.R G Hz transce ive r for
back hauls and to w (·0:.1 2.4 G llz tra nsce iver for clie nts.
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ct
tc lcrncdic inc system based
38i -
al.
Oil
in Bi
c:di 31
Ins I
nd Dr -In
I\luhammad lIaikal a tria
rec iv d rh B.E. (200_)
Unive . ita Indonesia and
(2
from niversi al DUI
E n, rern any . H I
rom
1. c.
burg
PhD
stud m in Faculty of Ele rI 31
Engm ring. Univ ers i I Tc:kn I
\ala, ia ,
Ind r a lIa rd ian ;\'lulyad i
rec iv d the B.E. (200·1) rom
lnstitut T .knologi Bandung. He IS a
Master student in Facultj of
Electri a\ Enginee ring. Un ivcr iti
T kn lou. Ma la ia.
388 -