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Ensuring Reliable Operations of Multiple RAIN RFID Systems in Hospitals
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I recently gave a presentation at the RAIN Alliance and AIM EngageAgain event about coexistence of multiple RAIN RFID systems in hospitals. I felt that the topic is important since the use of RAIN RFID is booming in the healthcare industry – including hospitals. Hospitals are unique and challenging environments as there may be several RAIN RFID systems operating in parallel. Each system has its own tags and readers, but they are not isolated from each other.

The coexistence of these systems should be taken into account from the beginning to ensure reliable system operations. The good news is that RAIN RFID technology includes several tools and methods to help with the challenge.

RAIN RFID in hospitals

There are plenty of documented RAIN RFID use cases for hospitals. These can be grouped into several categories:

  • Medicine supply chain tracking and inventory management
  • Medicine administration tracking
  • Patient tracking
  • Asset tracking
  • Tracking staff members and activities
  • Document tracking
  • Managing consumables inventory

These applications use several different types of RAIN RFID readers and plenty of RFID tags:

  • Handheld readers
  • Ceiling mount readers
  • Gate readers
  • Other fixed readers
  • Labels on medication
  • Labels on consumables
  • Embedded tags on consumables and workwear
  • Hard tags on assets
  • Labels on documents
  • Staff ID cards
  • Patient wristbands

There are also tags from other systems such as tags embedded in patients’ clothes.

Why designing for the coexistence of RAIN RFID systems matters?

When RAIN RFID tags are read or counted, the reader sees all tags in the reading zone by default, even if there are obstacles, such as walls, in between. If the systems are not properly designed, it is easy to read unintended labels.

Example - An application for ensuring that the right patient gets the right medication at the right time: If coexistence is not considered, the system may be overwhelmed with all the tags in the environment: ID cards, tags on consumables, documents, assets etc. The application fails as a result of unexpectedly high number of tags.

Methods for enabling coexistence

There are several methods and tools available for enabling coexistence. Some of them can be used together, but not all of them are useful for every application and environment. The decision on which method or tool to use should be made on case-by-case basis.

  • Frequency hopping with its interesting history is a functionality of RAIN RFID readers enabling multiple readers to operate at the same time. These reader features are on by default, just let the readers operate as they are intended.
  • Reader zoning is a method where a material blocking RF signals is used to isolate reading areas from each other. This cannot be used always, but is worth considering. Read more about Reader Zoning from another blog article.
  • Power adjustment and antenna positioning can be used to adjust the readers’ reading areas. Smaller power enables reading from a closer range, and pointing antennas to different direction changes the reading area. These reader settings and antenna positions should always be optimized with fixed readers
  • Tag selection and tag quality specification should match the applications’ requirements. A short-range tag cannot be read from far, and a tag with a too long read range may create stray readings. Non-specified or low quality tags lead to inconsistent performance, which creates both missed reads and stray readings.
  • RSSI filtering is a method where the reader is set to ignore tags with response signal that does not match the set criteria. The Response Signal Strength is only an indication of the distance between the tag and the reader, but nevertheless a useful method in some applications.
  • Code filtering and using Select is, in my opinion, the most important method and should always be used.

Code filtering and Select

RFID Tag Data Standards follow a structure where the beginning of the code defines which standard is being used, and the following parts define, in more and more detail, information about the tagged item.

For example, the EPC Tag Data Standard and ISO 15961 + ISO15962 Tag Data Standard have about 20 application areas included. The code structure allows filtering tags with codes at multiple levels, such as reading only document tags, reading only patient wristbands, or searching only for a specific tag, such as a staff ID card.

The filtering is done with the Select command in the inventory sequence.

An example - Inventory of medical packages:

  • The reader is set to use the select command as a part of the inventory cycle.
  • The select is set to consider only items with SGTIN codes, and ignore everything else. SGTIN is an EPC Tag Data Standard Code which points to Trade Items - items that are sold and purchased. This would also show other trade items, consumables for example. Usually this is not an issue, since the application is designed to handle a large number of codes, and items not in inventory are just shown unknown items and can be ignored at a software level.
  • Further filtering could be implemented by selecting only items manufactured by specific companies.

An example - Locating a person:

  • The reader is set to use the select command as a part of the inventory cycle.
  • The select is set to consider only GSRNP codes with a specific serial number, and ignore everything else. GSRNP is an EPC Tag Data Standard Code which points to Service providers, and serial number filters this down to an individual.

Filtering relevant tags with select command is a powerful method and should always be used. Use of filtering is based on using standard coding in all applications.

More information

Watch the full presentation recording:
Watch the Recording

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