CHAPTER 1
INTRODUCTION

The area of contactless identification systems is growing rapidly into a multibillion dollar market. It covers a broad range of applications including supply chain management, manufacturing, and distribution services. Examples of these applications include consumer packaged goods, postal items, drugs, books, airbag management, animal tracking, pharmaceuticals, waste disposal, clothes, defense, smart tickets, people tracking such as prisoners, hospital patients, patients in care homes, and leisure visitors as shown in Figure 1.1. Tough trading conditions due to the global competition strive industries to attain more process efficiencies. Therefore, effective goods tracking systems are required to assist the implementation of the modern management system.

Figure 1.1 Application areas of identification systems.

In general terms, any application that involves object identification, tracking, navigation, or surveillance would benefit from an identification system. Several hundred billion tags per year are required by this wide area of applications [1].

In this market, every application has its own technical and financial specifications. Main applications, those that need a huge number of tags, require high data encoding capacity and survive only with a very cheap tag solution. For others, secure identification and antitheft tagging is more important. In some cases, the tag size is a key factor and for some others proper identification of highly reflective items such as liquid containers or metal objects is of more importance. Reading range would be another imperative factor for many applications.

Irrespective of all priorities, there are two main factors that significantly matter in all applications: the data encoding capacity and the system cost. For applications with millions of items for tagging, high data capacity of the identification system is a must. For applications with a limited number of objects, high data encoding capacity would be also beneficial to secure the identification process or provide higher reading reliability by sacrificing some of the available bits. The cost reduction is the main initiative for the usage of identification systems in industry; hence, the cost of the identification system and its tagging price must be low and competitive enough to initiate the request for the system. Otherwise, there would be no demand for such systems.

The cost of identification systems, like any other broadcasting service, has two parts: the reader and the tag. The reader cost is normally a fixed cost irrespective of the number of tags. However, the price of the tag attached to every individual item is the most costly part of the whole system. Specifically when the number of items is in the order of millions, the tag price plays a major role in the system's total cost. For such applications, a tag price of only $1 would increase the total cost of the system to a level that restricts the usage of identification systems. Therefore, the tag price should be kept as small as possible to offer a reasonably low identification system cost.

1.1 BARCODES AS IDENTIFICATION TECHNOLOGY

Barcode is an optical-based, machine-readable technique for identification purposes. It has been established in various industries for many decades with proven applicability. Barcode provides an extremely low-cost solution for identification of items to which it attaches. Originally, barcode are comprised of many parallel printed dark lines. The tag's data are systematically represented by varying the widths and spacing of those parallel lines. This type of barcode, dominant in many applications, is normally referred to as linear or one-dimensional (1D) barcode. Data encoding capacity of the barcode tag is restricted by the diffraction of light through the edges of the lines, the reader sensitivity, and the reading distance, as shown in Figure 1.2. Diffraction restricts the minimum detectable line width as well as the minimum distance between two adjacent lines. This means that for increasing the data encoding capacity of the barcode, the only way is to increase the length of the tag. As the data encoding capacity of barcodes is proportional to the tag's size, it may result in an unreasonable tag size for many applications. This issue is considered as the main limitation of the barcode systems. The 1D barcodes have evolved into rectangles, circles, dots, hexagons and other two-dimensional (2D) geometric patterns to enhance the data encoding capacity. This has resulted in new machine-readable optical labels known as quick response (QR) code. QR codes use four standardized encoding modes to efficiently store data. The maximum storage capacity of QR codes can be up to 7000 characters, which is better than that of barcodes [2]. However, barcodes and QR have many operational limitations. They are very labor intensive as every tag needs to be read/scanned individually. Moreover, being an optical-based system, a clear line-of-sight (LoS), known as optical LoS, is also necessary for proper reading. This means that the tag shall be always printed and exposed on the products and the scanner requires clear optical LoS to read the barcodes or QR codes. Barcodes inside clear polyethylene bags cannot be read due to the light reflection of the bags. Any damage or dirt on the barcode results in improper reading. The reading distance between the optical scanner and the tag is also limited when considering the light dispersion/attenuation in free space and diffraction effect on the tag surface. Normal reading distance in optical systems is limited to few centimeters. Moreover, barcode is not a secure means of communication as tags can be easily reproduced by a cheap inkjet printer. The reading errors of barcodes depend on applications and many industries lose billions of dollars as compensations and damages each year. For example, optical barcode-based luggage handling has approximately 20% reading errors and airlines are paying more than $2 billion/year as compensations to passengers.

Figure 1.2 Data encoding limitation of a 1D barcode tag due to diffraction effect.

To address positive aspects of barcodes, no doubt a very cheap tag solution and proven applicability in identification systems are the most important factors. Its few cents tagging solution is very attractive for many applications, specifically for industries with millions of products. Being accepted globally for almost half a century also provides it a unique superior opportunity that makes it very difficult for other technologies to compete. The globally accepted international barcode quality specification standards, ISO/IEC-15416 (linear) and ISO/IEC 15415 (2-D) [3], and no privacy issues involved with the barcodes usage are highly regarded by many users.

Moreover, barcode systems provide a fairly good reading accuracy that is almost comparable with what other new techniques are offering [3]. Another good aspect of the barcode is that the accuracy of the reading process is almost independent of the items on which tags are placed.

1.2 RFID SYSTEMS

The usage of light waves as communication mean in the barcode systems causes many technical and operational limitations as discussed before. As an alternative approach, the use of EM waves for identification and tracking of objects was first proposed by Watson-Watt in 1935 [4] and coined as the radio frequency identification (RFID) system. In an RFID system, the reader sends an electromagnetic (EM)-wave interrogating signal toward the tag. This signal is then processed by the tag's microchip unit and backscatters the signal toward the reader. This backscattered signal carries the tag identification information and is received and processed by the reader to retrieve the data.

Figure 1.3 shows the generic configuration of the RFID system. As the EM wave is not obstructed by barriers, the system does not need a LoS link between the reader and tag. This provides a number of opportunities for an RFID system. For example, the tag may hide inside the item and not necessarily be exposed on the object as the barcode system does. Moreover, many reader antennas are omnidirectional; hence, they can detect tags irrespective of their position with respect to the reader. Multiple tag reading is also feasible in an RFID system, bulk detection scenario. The RFID reading distance may be much greater than that of barcodes as the EM waves are much less attenuated in free space than light waves. The more attractive part of an RFID system is its higher data encoding capacity, which is not comparable to the barcode, as the data are encoded by a microchip. Moreover, many security codes can be easily manipulated inside the microchip to provide more secure communication.

Figure 1.3 RFID general system structure.

1.3 BARCODES VERSUS RFID

Optical-based identification systems, barcodes and QR codes, and RFID systems all have their own advantages and limitations. This means that each system would be suitable for different purposes and under different circumstances. Although the majority of users still consider barcode systems as the most cost-effective way to handle the circulation and inventory management of equipment, the indication of changing market occurred in 2003, when Walmart adopted and mandated RFID tagging for all its suppliers. Walmart's motto of mandating RFID is to obtain seamless information from the manufacturing point to the ends of sales when the goods are sold and the boxes are crashed. There are numerous discussions and...