By Garrett Seeley, MS, CBET
Garrett Seeley, MS, CBET, Biomedical Equipment Support Specialist, VISN 17: VA North Texas Health Care System, Dallas Veterans Affairs Medical Center
After covering the basis of layer 2 switching hardware, it is important to cover the other layer two connection: wireless communication devices, or Wi-Fi. Most people use Wi-Fi daily without even considering the setup or hardware required to make this technology work. However, as repairers of medical devices, biomedical technicians need to keep in mind the requirements to make wireless medical devices work in a hospital.
Wireless connections function like a hub, but still have a MAC address. It is intended in function to replace a hardwired network switch. It can provide access to both a LAN and Internet traffic. Nearly every device that can work on a hardwired switch can be adapted to work on a wireless network. Technicians can accomplish this by adding an access point to a network and a wireless NIC card to a device. Access points transmit a radio signal, which is picked up by a wireless NIC card on a device. Because a wireless communication can be picked up by anyone with an antenna, Wi-Fi uses passwords to make sure that the communication is only understood by authorized devices.
Since communication happens openly and anyone with an antenna can hear this transmission and security is needed in most wireless transmissions. Since security is dependent on the hardware capability, lets first talk about wireless hardware. Some hardware may be compatible with older devices, but not all wireless devices are to be considered compatible with each other. For this example, consider the most popular hardware in use: the N type Wi-Fi. Older types include A, B, and G.
An N type wireless access point is generally capable of reverse compatibility to the older hardware. This is opposed to the newest communication type, which is the AX standard, also called Wi-Fi 6. It is only reverse compatible to the AC and N standards (Wi-Fi 5 and 4, respectively), but not further. This becomes very important when connecting older medical equipment to newer networks. Always make sure the type of device is compatible with the intended access points. Additionally, the hardware sets the speed of a communication. The speed of Wi-Fi access is set by the highest type of communication both the access point and the wireless device can use. Any Wi-Fi will only function at the highest speed the oldest hardware will operate at.
Modern AX Wi-Fi is capable of speeds at or better than modern hardwired systems whereas N communications are slower. An A or B communication is comparable to early HUB connected networks and their speed is barely functional for modern video communications. Consequently, these are only used as a last resort. Given this, it’s easy to assume that it would be best for everyone to use the most modern hardware all the time. However, that is not cost effective for most users. Medical devices often use older technology, and it is expensive to upgrade all access points when a standard is updated, which occurs about every 5 years. Consequently, we see older hardware used in the medical setting. Very few devices are made with AC or AX networks in mind due to compatibility. Additionally, this affects not only the device speed, but network security as well.
A Wi-Fi password is used to secure the transmission. The techniques using that password have changed over the years with the hardware updates. The earlier WEP encryptions were used in A and B transmissions and resembled a MAC address. WEP was both lengthy and difficult to set up. When G transmissions were introduced, designers incorporated a password in the Wi-Fi Protected Access (WPA) encryption. It was much simpler to use and became more popular. Its popularity and widespread use made it a target for attacks. To fix this issue, the WPA version 2 standard was quickly implemented for G, N and AC networks. It featured a stronger encryption and proved to be more durable to attacks than WPA. Recently, encryption has been upgraded to the WPA version 3 standard. This is the most secure encryption used with AC and AX networks. However, the hardware must be able to support the speed and encryption. Due to this, the implementation of WPA3 has been slow.
Additional settings for wireless are as follows: The SSID, and the Channel. The name of a network that is visible when connecting to a wireless networking is called the SSID. This SSID does not have to be visible; it can be hidden. Sometimes a hidden network will not show up on certain operating systems as it is assumed the technicians wanted the network to remain private. Devices can still connect to hidden networks, but users must type the name of the network to connect to it. In this way, a hidden SSID acts as a second password. A wireless network can use several access points with the same SSID name to provide for a larger Wi-Fi network. This is what a hospital does to provide the same network on the multiple floors. All the access points use the same eSSID, acting as multiple access points for the same Wi-Fi network. Most biomedical technicians will just have to be aware of these settings and know that a device can still join a hidden network if the correct name is manually entered.
Additional advanced settings for wireless include a channel setting, which are the individual frequencies for broadcast. Channels allow for multiple access points to operate in the same area without interfering with each other. This is due to the frequencies used in the Wi-Fi channels. B, G and N uses a 2.4 GHz range, and the A, N, AC and AX uses the 5GHz range. The 5 GHz Wi-Fi range has more channels with less overlap, making it the preferred standard for new access points. Newer Wi-Fi uses a much wider set of channels, N and older Wi-Fi uses an older standard with much fewer options for separating channels. This led to more interference in public areas such as hospitals or apartment buildings. N could flex to a newer 5GHz channel setting allowing it to operate more access points in the same area of use. Other advancements also made AC and AX able to coordinate channel usage between access points, allowing for even more Wi-Fi networks to operate in the same area. AC and AX also used the 5GHz range. A site scan will show the number of transmitters in an area. This is an app that is available for most phones. Keep in mind that frequency detections will be limited by the phone hardware.
This may seem to be a bit overwhelming but remember when networking with Wi-Fi, always lookup the hardware capabilities and check the compatibility to intended access points. For example, remember a certain pump with an ABGN card? That was the Wi-Fi that the NIC was compatible with. An ABGN card is a 2.4 GHz, N compatible card that will handle up to WPA2 encryption. In this case, the wireless network needs to use hardware compatible with these networks. This example really solidifies why understanding these settings are of importance to a biomedical technician. It will just happen to come up more and more as medical devices become wireless.
Garrett Seeley, MS, CBET, Biomedical Equipment Support Specialist, VISN 17: VA North Texas Health Care System, Dallas Veterans Affairs Medical Center.
