Guidelines for designing wireless communications for rural telemedicine in developing countries

The majority of ambulatory primary health-care centres (PHCCs) in rural and marginal suburban areas in Latin America, as in most developing countries, suffer from poor infrastructure, lack of suitable communications services, inadequate roads, non-existent or highly unreliable electrification, significant budgetary limitations and isolation from the rest of the health-care system. Such conditions represent serious obstacles to disease prevention, diagnosis, secondary care referral and even proper emergency treatment. The installation of suitable communications infrastructure, in the form of computer networks, is a practical answer to this problem. ¹ Such networks can provide telemedicine services to remotely located PHCCs by connecting them to a central health institution, where a wide range of general and specialty diagnostic and therapeutic services are likely to be available. ² Several of these networks are already being implemented in Latin America. ³ We provide here some methodological guidelines we have found useful for implementing wireless telemedicine communications networks.

Data gathering

The first step is to obtain comprehensive information for two purposes: to reveal existing conditions, and to establish the basic needs to be satisfied by the network. The information to be collected from each PHCC consists of the following:

General population demographic data;

Geography of the deployment area, including terrain elevation data and environmental features;

Inventory of the physical infrastructure and the technical equipment and services available;

Quantity, qualifications and availability of health-care personnel;

Typical demand (average numbers and types of cases currently handled).

Direct inspection of each PHCC and subsequent field interviews of the personnel are essential for this purpose. Official government sources and public data repositories are also useful in compiling the information.

Requirements

The second step is to define the requirements for the system by establishing what telemedicine applications are required, based on the information collected. The basic network requirements are:

IP-based connectivity for all computers at the PHCCs within the area to be served, between them and those at the network's central medical facility, and to the external Internet.

Support for as many telemedicine services as feasible, such as: email, web browsing, File Transfer Protocol (FTP) for biomedical signal and still image transmission, Voice over Internet Protocol (VoIP), video traffic for teleconsultation and videoconferencing.

A communications technology which is low-cost, robust, readily available, and easy to operate and maintain.

Technology selection

The choice of technology should be focused on optimizing the quality/cost relation. A wireless WAN is usually the best option, because of the isolation of rural PHCCs and their lack of access to wired communication infrastructures. ⁴ Networks based on the IEEE 802.11 standard (commonly known as WiFi) are ideal, because of their ubiquity, affordability and ease of installation, operation and reconfiguration. ⁵ Although WiFi technology was originally intended for LAN use with a range usually limited to tens of metres, the range can be increased to tens of kilometres when complemented by bidirectional amplifiers and directional antennae. ⁶ Our own experience confirms that, with proper design, well-placed external antennae and strategically placed repeaters, WiFi networks can meet the needs of PHCCs in many rural areas. Other groups have also already demonstrated success in this regard. The reports include experiences in India, ⁷ the UC Berkeley, ⁸ Colombia, ⁹ Perú ¹⁰ and Venezuela. ¹¹

Physical infrastructure

Physical infrastructure design requires a technical survey at each PHCC site. ¹² This includes extensive radio frequency studies to assess noise and interference. ¹³ Such studies may be conveniently accomplished by the use of ordinary laptop computers equipped with spectrum analyzer software. Non-proprietary simulation software may be used to predict propagation behaviour and patterns. ¹⁴ Determining antenna height and placement can be done by line-of-sight checking at each link. ⁴ Irregular Terrain Modelling software ¹⁵ is freely available for this purpose.

Performance simulation

Extensive simulation analysis of the expected network traffic should be conducted prior to network implementation and deployment to ensure that the network will support the chosen telemedicine services. ¹⁶ This very important step can be achieved using readily available network performance simulation software. ¹⁷ Different simulation scenarios must be assembled by combining the different applications that the network is supposed to support (e.g. email, HTML, FTP, VoIP, videoconferencing). Simulations can then be run to verify the compliance of the scenarios in terms of the network characteristics, including Quality of Service. ¹⁶

The minimum network requirements can be established using typical values derived from experience. ¹² We suggest at least the four scenarios described in Table 1. In the majority of cases it is sufficient to assume that the network has a single applications server located at the central node, which also handles the connection to the external Internet.

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Table 1

Typical simulation scenarios

Scenario	Web browsing	Email	FTP	VoIP	Video conferencing	Comments
1	✓	✓				Web browsing and email are two basic applications which do not impose large network requirements, and are widely used in services such as remote consultation, administrative information distribution or remote education.
2	✓	✓	✓			FTP manages data transfer but needs high bandwidth for reasonable transfer times of medical files. It is widely used in telemedicine services when large volume data transfer is needed, such as for remote diagnostics, remote monitoring or administrative data retrieval.
3	✓	✓	✓	✓		VoIP needs realtime execution and imposes substantial requirements on the network. However, implementing VoIP provides a telephony service to primary health-care centres, which is important, especially in case of emergencies.
4	✓	✓	✓	✓	✓	Videoconferencing is a realtime application which imposes even higher requirements on the network than VoIP. The service can be very useful in emergencies, and for teleconsultation, telediagnosis and tele-education.

Conclusions

We have proposed a practical method for designing wireless networks to support basic telemedicine services in rural, or isolated, PHCCs in developing countries. The typical limitations at these sites are a lack of infrastructure, and few material and financial resources. The key advantage of using our method is that the technical procedures involved do not require the use of complicated or expensive equipment and software. Rather, the work can be done using freely-available software that can be run on a portable computer.