In partnership with Mobile Health and
The New Zealand Telehealth Forum


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Understanding the Basics



In its simplest form a network is a collection of linked computers. Networks can be of any size, from two computers at home, to a small business such as a medical centre, to a large DHB with thousands of computers. Networks can be private where only approved users can access the network or public where there is generally free access to the network. The internet is an example of a very large public network.

The Internet - Upload and Download

During a video call the two endpoints exchange video, audio and other information. This has to be first uploaded by one participant then downloaded by the other. This is happening simultaneously in both directions with little delay.

Many internet connections are asynchronous, meaning upload and download speeds are different. For example, an ADSL connection may have a download (receive) speed of 8Mb/s but an upload (send) speed of only 0.7Mb/s. This uneven distribution is a challenge for video as generally participants are unable to upload/send at sufficient speed for video. The upload speed will always be the limiting factor.

It is important to remember the public internet is ‘contestable’ so performance which can be good at certain times may be poor at other times.

Types of internet connection:

  • Dial up – Not acceptable for video
  • ADSL & ADSL2 – Generally poor quality video
  • ADSL 2 – Generally OK quality for non-clinical situations. Quality will be variable and unreliable.
  • VDSL – Generally excellent quality, 720 pixel resolution HD video
  • Fibre – Excellent quality, up to 1080 pixels, HD video, with smooth motion

Wireless or Wired Connection?

wiredWiFi access is extremely convenient but a wired connection is recommended for telehealth whenever possible. This is especially important in clinical applications. In the graphic below, this download was achieved on a wired VDSL connection – the green section shows that the connection speed is very consistent.

wirelessA WiFi connection will produce a more variable connection speed with a decreased connection speed the further you are from the WiFi access point. In the graphic below, this download was achieved on the same computer and network but using a WIFI connection. Not only is the connection speed a lot lower, but, as can be seen with the peaks and troughs, the connection is also extremely variable.

Testing connection speed

It is important to thoroughly test any connection; this should be done at different times of day and over several days. Completing a speed test is simple using a website such as