J. Biomedical Science and Engineering, 2008, 1, 98-103
Published Online August 2008 in SciRes. http://www.srpublishing.org/journal/jbise JBiSE
Development of an intelligent VoWLAN services
for patient care improvement
Po-Yen Lin, Chih-Yen Chiang, Chih-Ning Huang, Woei-Chyn Chu & Chia-Tai Chan
Institute of Biomedical Engineering, National Yang-Ming University, Taipei, Taiwan. Correspondence should be addressed to {brian, phinyen, quire, wchu,
Since the rapid exchange of information and col-
laboration with colleagues are indispensable for
the quality of care. Effective communication be-
tw een care givers has been recognized as a criti-
cal factor on the high quality of patient care.
Communication in medical environment is often
intense and time critical, including laboratory
result, complex consultation and advice, which
require high degree coordination among care
professionals. Nevertheless, there are some de-
ficiencies existed in the actual state of the com-
munication system in hospitals, such as waiting
time for call back and inducing interruptions.
Current technological solutions should allow
developing a novel intelligent communication
system. In this paper, the proposed HPC2S
(Hospital Patient Care Call System) services
based on VoWLAN (VoIP over WLAN) will
achieve the needs of timely and efficient com-
munication among care professionals.
Keywords: Intelligent Communication System,
Voice over IP, Wireless LAN
Due to the complexity of patient care and information
access the requirements of related communication be-
tween patients and care professionals are augmenting. It
has been demonstrated that effective communication
among members of care team is essential in the delivery
of high quality of patient care [1]. Without the waiting
times on hold and the traveling back and forth to a phone,
a significant timesaving directly translates into improved
patient care. Obviously, an in telligen t, cost-effectiv e com-
munication system is important to improve the quality of
service. Some wireless communication systems provide
effective communication, such as Personal Handy-phone
System (PHS). However, it cannot rapidly deploy new
service model, such as one number service, 3-way com-
munication service, etc.
IEEE 802.11 based wireless LANs (WLANs) have
grown remarkably and spread rapidly in diverse settings
[2]. The market for WLANs has demonstrated a tremen-
dous growth in recent years [3]. It is evident that there
was a rapid increasing popularity of 802.11 WLAN hot-
spots deployed in residence buildings, enterprises, and
public areas [4]. There are miscellaneous applications to
WLANs, and Voice over IP (VoIP) is one of the most
popular and promising among them. VoIP over WLAN
(VoWLAN) is an innovative technology in the future of
communication that has been quickly accepted by many
health care administrators and care delivery staffs because
it is cost effective, easily deployed and interference free.
In the purpose of reducing medical errors and provide
better patient care services, communications in hospital
become vital and time critical. VoWLAN fulfills the re-
quirements of delivering critical information to relative
professions. Moreover, it can also improve the efficiency,
accuracy, and speed of care delivery and enhance man-
agement of the health system. The rest of this article is
organized as follows. Section 2 introduces the actual state
and architecture of the communication system in the hos-
pital environment. The proposed hospital patient care call
system and implementation are addressed in Section 3
and Section 4, respectively. Section 5 presents applica-
tions of medical professionals and section 6 concludes the
In Section II, we introduce the actual state and architec-
ture of the communication system in the hospital envi-
2.1. Hospital Communication Approaches
In hospital, the actual state of the communication system
can be divided into two categories according to the com-
munication manners they are intended for. One is the di-
rect communication, like oral communication between
face-to-face conversations. The other is indirect way, in-
cluding the written patien t record, telecommunication and
Internet communication. The face-to-face conversation
has been demonstrated to influence patient outcomes, but
it lacks flexibility and mobility. The written way is short
of interaction among the care professionals. This disables
health professions to handle the situations immediately
and diminishes the health service. Telecommunication
SciRes Copyright © 2008
P. Y. Lin et al. / J. Biomedical Science and Engineering 1 (2008) 98-103 99
SciRes Copyright © 2008 JBiSE
such as Public Switched Telephone Network (PSTN),
pager, Personal Handy-phone System (PHS) is popular in
most hospitals now. The PSTN and pager system bring
the convenience but still cause the waiting times on hold
and the traveling back and forth to a phone [1]. Moreover,
PHS has the problems about the dead spot, junk mail and
requiring recurring monthly. The primary disadvantage is
that PHS system cannot rapidly deploy new service model
to diverse medical situations. It is evident that the oral,
written, and telecommunications cannot fulfill the re-
quirements of delivering critical information to relative
professions. The conversation via Internet, such as VoIP,
VoWLAN can make up the deficiencies of communica-
tion ways as mentioned above. We have further introduc-
tion in the next section.
Nurses are the first-lined caregivers to offer immediate
care to patients. If patients are in critical situations which
requiring further treatments, nurses will then contact doc-
tors on-duty first, then resident doctors, visiting doctors
or relevant others in order. However, it is the generally
routines that nurses cannot carry any communication de-
vices that may result in interference to instruments and
cause disturbances for patients. However, as their job
duty, they have to work between wards and work-stations,
and if anything happens on their way to wards or to units,
they cannot offer assistance in time. Therefore, it is quite
time consuming for the nurses to find out patients’ needs
and react properly according to patients’ conditions.
In [5], authors proposed a medical vehicular to reduc-
ing medical errors. It provides efficiency and accuracy
Unit Dose Delivery Service (UDDS) with RFID technol-
ogy. This system provides mobility to care giving. How-
ever, it lacks effective communication modules and can-
not meet the requirements of delivering critical informa-
tion to relative professions.
2.2. Communication System Architecture
From above discussion, VoIP/VoWLAN services are
sufficient enough to meet various settings. Wireless is a
pervasive technology and has been widely used in most
hospitals. Voice and data converged on the hospital net-
work have become a prevalent communication trend to
provide the optimal patient care service. Figure 1 is the
hospital communication architecture including PSTN
system and novel IP telephony. An IP Private Branch
Exchange (IP PBX) is used to combine Internet and
PSTN for voice transmitting.
Voice Over IP (VoIP) is the delivery of voice traffic
over the Internet. VoIP involves sending voice informa-
tion in digital packets rather than by using the traditional
PSTN [6]. The packets are transmitted using Real Time
Protocol (RTP) over User Datagram Protocol (UDP) over
Internet Protocol (IP). RTP is commonly used in Internet
telephony applications. RTP combines the data transport
with a Real Time Control Protocol (RTCP) to monitor
data delivery.
Standards like Session Initiated Protocol (SIP) and
H.323 are maturing to support convergence services in
next-generation networks. H.323 was designed for mul-
timedia communication over IP networks, including audio,
video conferencing. SIP was design to be a part of the
overall Internet Engineering Task Force (IETF) multime-
dia data and control architecture. However, many con-
sider SIP a powerful alternative to H.323 because of its
flexible deployment, easier maintainability, and simple
format for commands, etc. As a result, a VoIP communi-
cation system based on SIP can develop diverse services
correspond to different requirements.
There are two major roles in SIP, a client and a server.
The Ward client sends a request to the server and then
server passes the message onto Laboratory Medicine cli-
ent. Via the connection setup, two clients can communi-
cate with each other as shown in Figure 2.
Figure 1. The hospital communication architecture includes PSTN and IP telephony system.
100 P. Y. Lin et al. / J. Biomedical Science and Engineering 1 (2008) 98-103
SciRes Copyright © 2008 JBiSE
Figure 2. Signaling of a SIP call service.
According to the hospital communication requirements,
we propose an intelligent and cost-effective communica-
tion system, called hospital patient care call system
(HPC2S), to improve the quality of patient care. The
main features of the proposed system are the one-number
service and call forwarding.
One-number service means that a client can have mul-
tiple registrations with several terminals or devices. The
client has a single number. When the number is called,
the calls to the client may be sent to all registered desti-
nations, such as office SIP phone, PC-based soft phone,
and WiFi phone. Any of these destinations picks up the
phone, server will automatically cancel others signaling.
Call forwarding service has two categories: condi-
tional call forwarding and directive call forwarding. In
conditional call forwarding mode, the server will tran sfer
the INVITE signaling to another predefined destination
if the signaling fails to contact anyo ne in a time interval.
Apart from conditional one, directive call forwarding
does not send INVITE signaling to the destination but
rather forward to another predefined destination.
To illustrate the effective communication of HPC2S,
a scenario and the signaling of SIP service are shown in
Figure 3 and Figure 4, respectively. Laboratory medi-
cine needs to notify the doctor when the sample of the
patient is abnormal. First they dial the mobile SIP hard
phone (#333) of one doctor. According to one number
service of the SIP server, proxy server will send signal-
ing to both mobile SIP hard phone and the other SIP
phone (#333) in the callee’s office. Yet the callee had set
the office phone the “Conditional Call Forwarding” to
the phone of the ward (#222) earlier. SIP server will
forward the INVITE signaling to the predefined destina-
tion automatically. It is one of the smart communication
services of HPC2S, including one number service and
call forwarding. Callers can have much more easier way
to contact with callees, consequently save their time to
check where callee would be and extension number.
In this section, we introduce the design and implementa-
tion of HPC2S. HPC2S is developed based on SIP pro-
tocol. The detailed descriptions of the system architec-
ture and implementation prototype are presented in the
following subsection.
4.1. Session Initiation Protocol (SIP)
SIP is an application-layer protocol that can establish,
modify and terminate interactive multimedia sessions,
such as videoconference, Internet telephony. It is de-
signed to address the functions of signaling and session
management within IP networks. Signaling allows ses-
sion information to be carried across internet. Session
management provides the ability to control the features
Figure 3. Calling flow chart of the One-number and Conditional Call Forwarding service.
P. Y. Lin et al. / J. Biomedical Science and Engineering 1 (2008) 98-103 101
SciRes Copyright © 2008 JBiSE
Figure 4. Signaling of a SIP One-number and Conditional Call Forwarding service.
of an end-to-end session. More accurately, SIP is a re-
quest-response protocol, dealing with requests fromcli-
ents and responses from servers. Participants are iden
tified by SIP Uniform Resource Indicators (URIs). SIP
server determines the end system to be used for the ses-
sion, the communication media and media parameters,
and the called party's desire to engage in the communica-
tion. Once these are assured, SIP server establishes ses-
sion parameters of the communication, and handles ses-
sion transfer and termination [7].
The SIP architecture can be grouped into two catego-
ries: clients and servers. SIP servers include proxy server,
redirect server, registrar server. SIP clients include soft-
phones, such as phone capabilities installed in personal
computer, and IP phone. In addition, the SIP servers can
interact with other application servers, such as location
servers, to provide a wide range of value added services.
4.2. HPC2S Components
According to SIP protocol, the design of HPC2S is
shown in Figure 5. One is the administration functions
that include authentication, register, and configure for
access control. The other is SIP proxy server. SIP users
are identified by unique SIP addresses. Client needs to
register at the SIP server first using their assigned SIP
addresses. The authenticated clients also can update their
information stored in SQL database with UseDir JAVA
class. Other SQL database related JAVA classes, such as
IdImport, RegisteredList, SessionList, and etc, provide
useful functionalities for the web-based user interface.
IdImport provides the registration for client and Regis-
teredList can show who have been registered. Ses-
sionList class is used to identify which sessions are pro-
ceeded. SIP server has diverse JAVA classes to commu-
nicate with SQL database. ProxyServer, SIP, and SIP-
PacketMessage resolve the SIP packets to create a ses-
sion, such as INVITE request packet. In a session, Ses-
sionMessageProcessor class decomposes the session
message to initialize InviteRequest, RingingTimeout, and
TalkingTimeout according to received messages. Obvi-
ously, the HPC2S provides the administration setting and
establishes and terminates VoIP calls.
4.3. SIP Call Establishment
When a user initiates a call, a SIP req uest is sent to a SIP
proxy server. The request includes the address of the
caller and the address of the intended callee. Figure 6
shows the SIP point-to-point calls establishment process
started with an INVITE message. The following are the
procedure descriptions.
Procedure Call-establishment
Caller sends INVITE request to SIP server, which
extracts SIP Packet Message
Server sends INVITE request to callee.
Session message processor enables both ringing
timer and talking timer, then ACK message and
ringing signal are sent back to caller. Session
message processor also needs to deal with all
session packets.
Callee sends OK to session message processor.
Caller receives OK message.
ACK message is sent from caller.
ACK message received from callee.
Session is set up and they can access voice or
media data transmission.
Since a given client can h ave multiple registrations at
a SIP proxy server. If a user has multiple active registra-
tions, then calls to the user will be sent to all registered
destinations based on the call-establishment procedure.
This capability can enable the one number service. SIP
proxy server can also change the Request-URI of an
INVITE to the suitable contact addresses. If SIP proxy
server does not receive the OK(INVITE) message, it will
automatically transfer the call to the presetting address. It
is evident that the call forwarding function is achieved.
102 P. Y. Lin et al. / J. Biomedical Science and Engineering 1 (2008) 98-103
SciRes Copyright © 2008 JBiSE
Figure 5. The function components of HPC2S.
Figure 6. Process of SIP call establishment.
HPC2S both combines one number service and call for-
warding to support convenient communications for the
medical environments.
The most powerful advantage of HPC2S is the flexibility
to adapt to various hospital situations and even for di-
verse users. All the service developments not only meet
the special needs of hospital users but also improve the
quality of patient care. Here are some applications car-
ried by HPC2S as shown below:
A. Physicians
z To increase efficiency in service delivering,
physicians can immediately and directly con-
verse with other health professions about lab
results, further treatments, and patient up-
z Physicians can locate related health profes-
sions as well as relevant nurses from the
medical vehicular, and this can shorten the
response time in finding the specific person.
B. Patients
z By using HPC2S, patients can reduce wait-
P. Y. Lin et al. / J. Biomedical Science and Engineering 1 (2008) 98-103 103
SciRes Copyright © 2008 JBiSE
ing time for caregivers and enhance the rela-
tionship between physicians and nurses.
z HPC2S bundled in medical vehicular can
provide more delicate services with fewer
pharmacological and other medical errors.
C. Nurses
z Nurses can offer high-quality patient care
with medical vehicular and eliminate possi-
ble medical errors.
z HPC2S allows nurses to locate physicians
conveniently, and can dramatically reduce
required walking and holding time on the
D. Staffs
z Staffs can have a conversation with the phy-
sicians and nurses at the same time when pa-
tients’ examination results reveal abnormal.
z The hospital resources can be arranged more
effectively via the HPC2S by staffs, such as
utilizing operating rooms via better schedul-
ing procedures.
In this article, we proposed a SIP-based hospital patient
care call system. HPC2S provides a timely and effective
communication among the care professionals to improve
the quality of patient care. The medical vehicular with
HPC2S have become more reliable and robust for deliv-
ering critical information. Nurses have direct conversa-
tions with other health professions by the intelligent
medical vehicular. Nurses can also provide complete
patient care without interferences. Since the network
location awareness may have many potential applications.
Therefore, how to enable network location awareness
with HPC2S would be one of our future works.
This work is supported in part by the National Science Council under
Grant No. NSC 96-2627-B-010-01 2.
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