Click here for ObjectSpace: Business- to- Business Integration Company
home account info subscribe login search My ITKnowledge FAQ/help site map contact us


 
Brief Full
 Advanced
      Search
 Search Tips
To access the contents, click the chapter and section titles.

Wireless Networking Handbook
(Publisher: Macmillan Computer Publishing)
Author(s): Jim Geier
ISBN: 156205631x
Publication Date: 09/01/96

Bookmark It

Search this book:
 
Previous Table of Contents Next


APPENDIX D
Wireless Networking in Healthcare


NOTE:  

The authors of this section are Saleem Desai, M.D., and Balasubramanian Ramachandran from Medical Communication Systems (MCS), Inc. MCS is a medical informatics company based in Boston, MA, and specializes in the application of emerging technology to enhance and expedite healthcare delivery.


Medicine, like many scientific activities, cannot be practiced effectively without accurate and timely information, such as information about patients and their problems, appropriate care giving procedures, and their benefits and limitations. Today, the vast bulk of the information cannot be found online, but in one hard copy form or another, such as paper based patient records derived from provider (patient encounters, film-based X-rays, and scans from diagnostic procedures). All are critical components of what, in aggregate, is called the patient record. Computerizing the patient record and enabling wireless retrieval is an excellent way to reduce administrative costs and deliver better healthcare facilities.

Wireless technology in the form of cordless, cellular telephony and paging has enhanced the way of life of the common end user. The benefits, however, are not limited to private users. Using wireless technology in the medical setting can greatly improve the productivity of healthcare providers and the accuracy of diagnoses by permitting the retrieval of patient related data by physicians in remote locations.

The wireless application to healthcare grew out of a combination of existing market needs. As highly mobile professionals, physicians require immense amounts of data to make critical, life-saving decisions in a timely fashion. Recent trends in healthcare, such as cost-containment, susceptibility to malpractice suits, and the need to access large amounts of information, have forced physicians to spend more time conducting administrative work, rather than actual patient care. These trends increase the necessity of a wireless network to facilitate the transmission and access of the computerized patient records from one medical facility to another within a particular geographic area. A wireless handheld device carried by medical personnel will enable him or her to retrieve and relay patient-related data in an expeditious manner. This appendix primarily focuses on the design and implementation issues surrounding wireless personal communication systems in the healthcare environment, including related network architecture issues, traffic, time, and radio resource management.

Benefits of a Wireless Network in Healthcare

Hospital facilities require a great deal of mobility due to the medical personnel constantly being in motion. In such a setting, a wireless local area network (LAN) can provide many benefits for healthcare. By providing wireless portable terminals to doctors, nurses, and hospital administration staff, for example, patient data can be accessed from practically anywhere within the hospital building, and a complete record of prescriptions and medicines can be tracked to the patient’s bedside. Such a system can increase the efficiency of medical personnel, thereby reducing healthcare costs. Pertinent medical information is available in real time from multiple sources. Interconnecting the medical facilities enables the transfer of medical and patient images from X-ray scans, consumer health information, and decision analyses.

Central Computerized Patient Record (CCPR)

Within a hospital, the information obtained from multiple sources can be compiled, analyzed, and stored in the central repository—Central Computerized Patient Record (CCPR). This repository is made available in real time by wireless means to medical personnel. The CCPR communications layer also connects wireless clients that communicate directly with each other. This layer enables medical experts in different fields to deliver quality healthcare by exchanging multimedia information in real time.

Patient case information is generally stored in different databases depending on information content. Medical facilities have numerous modules including radiology, pharmacy, billing, and laboratory that represent different segments of the medical process. These modules have separate databases to store the relevant information, but in the past there was no interaction between these databases to provide a complete picture to the physician.

CCPR provides a central Database Management System (DBMS) that integrates these various modules with a client server methodology. The CCPR design enables any additional module to be plugged in easily by implementing a standard API.

CCPR can be further subdivided into the following subsystems :

  Graphical user interface (GUI) with CCPR clients.
  CCPR server that extracts information from the repository and interacts with other servers.
  Database servers for all modules.

The GUI is simple, user-friendly, and portable across PC platforms and handheld devices. In a healthcare environment, the integration is highly advantageous because the CCPR client establishes a client process that communicates with the servers of other modules. The CCPR client, for example, interacts with the Radiology server module to extract chest X-rays on a given case. The GUI would then display this multimedia information to the medical personnel in an appropriate manner determined by the data type.

Supplementary modules, such as a medical knowledge base, can be incorporated into the system. The medical knowledge base module provides an access path for medical facts or information. This information can be used by medical experts for prognosis, diagnosis, and management. In effect, the CCPR provides a timely update of patient records and an access path for medical facts and information.

Architecture of a Hospital-based Wireless PCs

Mobility and service portability problems must be addressed when using an integrated network. Medical personnel, for example, must be able to extract all necessary patient information through a single directory number. Terminal mobility problems are accommodated by using a portable terminal with wireless access to a fixed base station. Personal mobility can be accommodated through wireless access by using a compact identity card equipped with a wired or wireless access.

Terminal Mobility (TM) and Handover

Terminal Mobility (TM) offers subscribers the ability to roam from one radio coverage area to another. The network, then, must keep track of the movements of the mobile terminal at all times. Another key issue in any wireless system is the ability to continue an existing call as the user moves from one radio coverage to another; this is known as system handover. In a healthcare environment, efficient handover must be performed because the physician is extremely mobile and the continuation of the call from one radio coverage to another is critical. Some wireless systems prioritize handovers over originating calls, but in a hospital environment, both tasks are equally important.

If the user is walking, then the handover is relatively slow. If the user is moving in a vehicle, however, handover has to be faster. In deciding when to perform a handoff, it is important to ensure that the drop in the signal level is not due to momentary fading and the terminal is actually moving away from the base station. To achieve this, a certain threshold level of the signal is fixed depending on the traffic behavior. The base station then monitors the signal level for a certain period of time before a handover is initiated. This period is known as the dwell time and varies depending on the call statistics. This running measurement of signal strength (RSSI) should be optimized so that unnecessary hand-offs are avoided while ensuring that the required hand-offs are completed before a call is terminated due to a low signal level.

In effect, performing handover is a time critical issue. The continuity of the call is ensured by handover when the radio resource changes within the cell (intra-cell handover) or between cells (inter-cell handover). The handover process involves three successive phases: namely measurement, initiation, and handover control. The handover control process depends strictly on the particular radio access method chosen and channel allocation schemes.

Personal Mobility

Personal mobility (PM) relates to a user carrying a personal subscription identity (personal telecommunication number) rather than a terminal. When a caller dials the number, it is the network’s responsibility to route that call to the terminal of the subscriber’s choice. This could be done through either a manual entry or automatic registration by using a personal identity module.

Using this personal subscription identity, the user can access services from any terminal, whether it is in a fixed or mobile communication network. This is an extremely important and useful requirement in a hospital. The medical personnel are constantly moving between the emergency rooms, diagnostic centers, and other places of work. They also have to spend a considerable amount of time attending to administrative and patient related matters. Because of these considerations, ready access of data from any terminal of their choice is highly advantageous. To achieve this kind of personal and terminal mobility, a database structure and definition of the parameters are required to distinguish between personal mobility and terminal mobility. To enable the free combination of user and mobile terminal related data, maintaining two separate databases is essential. Authentication of the mobile terminals and the users have to be done separately in such a case.

Radio Resource Management

The frequency spectrum is a limited natural resource and efficient utilization of the scarce spectrum available in any wireless system is a challenging design task. Therefore, frequency management is an important issue. The same frequency can be reused repeatedly in different geographical locations. Various locations using the same frequency are called cochannel cells.

The minimum separation required between two nearby cochannel cells is based on specifying a tolerable cochannel interference that is determined by the required carrier-to-interference C/I ratio. As the cochannel separation distance increases, the interference correspondingly decreases. At the same time, however, there is also a decrease in the capacity. Thus, there is a trade-off between the re-use factor and the tolerable interference.

Channel Allocation Schemes

Channel assignment strategies can be classified essentially as fixed channel allocation (FCA) and the dynamic channel allocation (DCA). In a fixed assignment scheme, the number of channels allocated to a particular cell is fixed, making management easier. An inherent disadvantage of the FCA scheme, however, is that once all the channels in a cell have been allocated, any other call attempt at that site is blocked. The dynamic channel allocation method relies on a call-by-call optimization where all the channels are managed by the mobile switching center (MSC). For each call attempt, channels are assigned to the user on a service-on-demand basis by the network. Here, the blocking probability of a call is less than the fixed channel scheme, but the management load of the network increases correspondingly. Other hybrid schemes exist where part of the total number of channels available is allocated to each cell and the remaining channels are in control of the Mobile Switching Center (MSC). The MSC allocates them on demand to the user. Also, there is a trade-off involved between the management load on the network and the specific channel allocation scheme. In a healthcare environment, maintaining the continuity of data is extremely important.

Propagation in a Hospital-based Wireless PCS

The effective design of a radio network requires accurate description of the channel. One of the most important and difficult issues in wireless communications has been modeling the radio channel. In routine healthcare applications, communication is essentially indoors and involves short distances; therefore, factors such as detailed layout structure, building type, and materials used have to be considered. These factors significantly affect radio propagation and corrections must be made in the existing propagation models for indoor radio communications.

These models are also used to determine the optimum location for the installation of antennas and to analyze the interference between different systems. Hospital construction can highly distort radio wave propagation because multiple reflections of radio waves occur due to the interiors of the building. The received signal will therefore be affected by multi-path as it equals the sum of the attenuated, time delayed, and phase offset versions of the original transmitted signals. With current higher data rates of transmission, intersymbol interference (ISI) of the signal will take place. Prudent planning is necessary for proper signal coverage.

Engineering Solutions for Propagation Issues

As the distance of the receiver from the transmission facility increases, the received signal strength decreases. In a highly cluttered environment like a hospital, there is no direct line-of-sight (LOS) component of the signal between the transmitter and receiver. Therefore, the signals received are highly attenuated. This attenuation causes large scale path loss, and, due to the various reflected components of the transmitted signal, short-term fading over small distances also occurs. Extensive models for the geographical layout of the hospital, contours of equal path loss in the structure of the hospital, shadowing, and diffraction can be used to determine the construction of the medical facility.

Wireless Security in Healthcare

Assuring the privacy of an individual’s healthcare data is a key issue in healthcare systems. Even though patient record data can lead to important information for healthcare providers and their patients, there is also a potential for personal harm if disclosed inappropriately. As the data is transferred across wide areas, the integrity of the data must be maintained and the originators and requesters of the data must be confirmed.

Unique identification of patient information is possible through retinal eye scan images, fingerprint readers, DNA blood typing, or personal identification numbers in digitized form. Security of information is important in any communication system and, in healthcare, patient related data needs to be secure and must be available to the concerned medical personnel only. Data encryption and cryptography are methods proposed towards achieving security of information. There are various data encryption standards available that can be used effectively for security in healthcare.

Wireless System Security Design Issues

The role of a wireless system in hospitals is to enable access to patient-related data by the highly mobile physician. Handheld data communicators with the graphical user interface (GUI) software systems will access the centralized computerized patient record (CCPR). The CCPR is, in turn, linked to various hospital departments and other medical facilities. A wireless network accessed through a multimedia handheld terminal (HMT) must have systems reliability and security.

Wireless systems must have system reliability so that accuracy and dependability of data collection, processing, and maintenance are secured through appropriate system design. This includes the use of physical security measures that are directed toward the protection of the environment and equipment. Although currently wired clinical systems are designed to assure 100 percent backup in most environments, the effectiveness of data security in wireless systems has not been fully evaluated. Some of the key security issues in wireless systems are addressed in the following list:

System security: System security is imperative in the wireless healthcare environment. Protection is necessary to prevent unauthorized access.
Data Security: The protection of data from accidental or intentional disclosure to unauthorized persons and from unauthorized alteration. Techniques for security include software and hardware features and data encryption with frequency hop.
Data Integrity: The soundness or completeness of the data that is being used. Data integrity may be maintained by implementing security measures and procedural control, by assigning responsibility, or by establishing audit trails.
Usage Integrity: Implement protection measures against unauthorized access to programs and data, including measures against unintentional or deliberate misuse of patient related data.

Summary

Enabling wireless access to patient related data in the fast-paced healthcare setting by handheld multimedia terminals can enhance the performance and flexibility of the user or physician.

Furthermore, the quality of healthcare delivered improves greatly because data is readily available for diagnosis and interpretation. In addition, cost containment may justify the deployment of such a system. Engineering issues, such as propagation effects, time management, and security, must be considered for effective performance of wireless networks. Environmental safety is another key factor that must be addressed; health risks associated with radio frequency (RF) radiation and pulsed microwave radiation must be considered.


Previous Table of Contents Next


Products |  Contact Us |  About Us |  Privacy  |  Ad Info  |  Home

Use of this site is subject to certain Terms & Conditions, Copyright © 1996-2000 EarthWeb Inc.
All rights reserved. Reproduction whole or in part in any form or medium without express written permission of EarthWeb is prohibited. Read EarthWeb's privacy statement.