Building Smart RFID Networks

By Hersh Bhargava

Nature of RFID Data
RFID data has some similarities with other streaming data, such as stock trades, but it is still very different.

High volume: RFID interrogators read any tag within their read range, generating a huge amount of RFID events.

General Topology of an RFID Network

Non-contextual: An RFID tag is read as it enters the vicinity of an RFID interrogator, and an RFID event is generated and routed over the network. At the lowest level, the event is just a tag ID, a reader ID and the time last seen. The broadcasting of each RFID event to all parties creates too much noise, however, and not every application needs a particular event. The result is more traffic on the network, and applications get bulkier and slower because they have to process every event.

Spurious reads: Because of the wireless nature of RFID technology, RFID tags are read any time they come within the read range of an interrogator. A poorly tuned reader may pick up tags that are far away. If the receiving and shipping portals are close and a tag passes through the receiving portal, a spurious EPC read may occur at the shipping portal as well. Spurious reads can also happen due to human error. A forklift carrying RFID-tagged inventory may take a wrong path, for instance, resulting in spurious reads. From an application standpoint, such reads need to be discarded by putting business rules or appropriate checks and balances in place.

Non-transactional reads: If a forklift carrying tagged material passes through a reader's vicinity three times, three different events are generated for the same tag, even though only one is relevant to the application. This might happen if an operator were to overlook something and back up the forklift to correct the mistake. Two of the three resultant reads would be spurious and would need to be discarded, either by the network or by the applications consuming the data. The later choice would increase traffic on the RFID network. Applications need logic to sieve out such spurious events, making them bulky.

Short life: RFID data becomes obsolete quickly as a tag moves to the next stage in a business process. If the finished product is shipped out of a factory, the complete history of that tag may be moved to an archival database, or even discarded (as opposed to keeping it in the active database and increasing the cost).