RFID technology overview

Ubiquitous, as defined by Merriam-Webster Dictionary, means “existing or being everywhere at the same time”. Based on this, ubiquitous computing is the computing environment that is everywhere; it is in the environment surrounding us and becomes part of our life, and as the technology is almost transparent to us, it does not become a distraction. As RFID provides a way of making “things communicate with other things” (understanding things as machines, products, etc.), people can just live their lives and let the technology work by itself.

• Freqeuncy issue

The 3 main frequencies used for RFID purposes are: HF(13.56 MHz), UHF(860 MHz – 930 MHz), and Ultra UHF( 2.45 GHz). The first one fits in the category of High Frequency (HF) and the other two in the Ultra High Frequency category (UHF). Generally speaking, by using a higher frequency you can improve a tag reader's ability to read many co-located tags because of the higher data transfer rate, reducing the chance of collision. [07/want04] It is also possible to read tags at bigger distances (up to 100 meters with active RFIDs) while increasing the frequency.

HF is cheaper than UHF technology and HF can be recommended for most of the applications, especially when a large number of tags/readers are required. If the application is going to be used within the hospital, HF can be recommended for cost reasons as well. For drug tracking UHF can be recommened , because the need of interoperability with other health centers and the FDA.
If a further range of operation is needed or tag size is not important, probably 900MHz frequency can be recommended. If more functions are needed, 2.45GHz frequency can be recommended because it is easier to integrate with sensors and has more functions, but cannot be used inside operation rooms or near people with pacemakers.
When mobility is a must, portable readers should be used. These machines have their own operating system and usually have the ability to send data to a central computer through a wireless connection. Otherwise, fixed readers should be used (portable readers cost 2-5 times of a fixed one).
HF has a lot of advantages in size and antenna design, but has a very short operation range. On the contrary, 900MHz offers a very long range and a great tolerance to interference (medium to water/metal) but a bigger tag size and more complex antenna design. The 2.45GHz also has very small size tag, but it is not so tolerant to interference as 900MHz and has a shorter range, although the antenna design is a little bit easier. Both HF and 900MHz should be able to work with metal/water and avoid most of interference, and their bigger differences are in size and range.

• Data Standardization issue

Several standards / proposals might be used within these frequencies, including ISO 14443, ISO 15693, ISO 18000 and EPCglobal, which has its origin in the MIT Auto-ID Labs.

Even though the Japanese ubiquitous ID protocol implementation has gathered strong allies like Microsoft and Hitachi, and is trying to became an RFID standard, EPCglobal’s UHF Class 1 Gen 2 is in a much more advanced stage and has already become a part of ISO 18000-6. This standard defines the use of the 860 MHz – 930 MHz spectrum.
The EPCglobal standard defines the EPC code within its Architecture Framework. Other important standards are the ONS (to locate authoritative metadata and services) and the EPCIS (provides a service interface to access information from the central DB or repository).
The EPC is defined by EPCglobal as a code to identify the manufacturer, the type and unique id of a given product. It uses 96 bits, where 38 are for identifying its serial number (see table below). That means it can have 2^38 (270+ billion) unique serial numbers for each product and company. EPCglobal Tag Data Standards Version 1.3 defines all these details.

• RFID tag with Material issue

There are certain limitations when using RFID tags on liquids and metals. According to research, UHF use would be more appropriate than HF for the pharmaceutical industry in order to avoid these limitations. Several kinds of antennas can be used in order to satisfy a specific need. In one of Impinj's technical documents, some of their models are described, including one that is specially interesting for the pharmaceutical world; the PaperClip Antenna, that can be used everywhere, even in water. [10/impinj06]But as this is a (relatively) new technology, new problems arise.

• Privacy and Security Issue

Privacy and security issues are covered in many ways, ranging from manual deactivation of the RFID tag to sophisticated public key protocols or hash functions, that require the tag to have processing capacities. Encryption technology is developed so far for privacy concern, this technology provided authentication, privacy, integrity and non- repudiation: [ohkubo05, anshel06]
-Smart tags
-PKI capable tags
-Anonymous-ID scheme
-Tag with lightweight circuits: i.e. hash function
- Algebraic Eraser