Implementation and Operational Issues

Since radio waves bounce off metal and are obsorbed by water, RFID tags may not be embedded within metal objects or items with high water content.  This can be overcome by using lower frequency tags, which have better penetration capabilities.  However, low frequency tags also require a more clear signal path between the tag and the reader, but not as close as bar codes.

Readers are often designed to support time division multiplexing to prevent the signal from one reader interfering with the signal from another reader known as tag collision. Designing RFID systems to capture signals from individual tags in a serial fashion prevents reader collision.

Being that active tags are larger and more costly, economics dictate that they be a good choice for applications such as tracking high-value goods and related services.  On the other hand, passive tags are cheap and small in comparison, allowing them to be placed on virtually any item or object.

Until RFID tags become much cheaper, it will be impractical to identify millions of items.