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Design and implementation of RFID based air-cargo monitoring system
Advanced Engineering Informatics 25 (2011) 41–52
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Design and implementation of RFID based air-cargo monitoring system Yoon Seok Chang a,*, Min Gyu Son a,1, Chang Heun Oh b,2 a Ubiquitous Technology Application Research Center, School of Air Transport, Transportation and Logistics, Korea Aerospace University, 100 Hanggongdae-gil, Goyang-City 412-791, Republic of Korea b EXIS Software Engineering, #1801, Building 2, DMC Iaan Sang-am, 1653 Sangam-dong, Mapo-gu, Republic of Korea
a r t i c l e
i n f o
Article history: Received 15 November 2009 Received in revised form 1 April 2010 Accepted 7 May 2010 Available online 25 June 2010
a b s t r a c t This paper deals with the design and implementation of radio-frequency identification (RFID) based cargo monitoring system which supports tracking and tracing in air-cargo operation. In order to apply a proper RFID technology, firstly we studied RF operational environment and tested different RFID frequencies. After finding a right technology (i.e. frequency), we designed and implemented tracking and tracing system applying EPC networks. We believe that our research will bring a guideline for developing RFID based tracking system for cargo operation. Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction To survive in today’s highly competitive business world, the speed of operation/delivery and high level of customer service, visibility across enterprises boundaries as well as across countries are considered as key factors. Due to such reason, the importance of air transport is becoming more and more emphasized. However, due to higher cost than other transportation methods, various technologies have been investigated to maximize its process efficiency. Among them, RFID system is getting more attention because of its distinctive capabilities compared to the traditional barcode system: Uniqueness: enable unique product identification, distinguish every single product by its ID. Timeless: reduce/eliminate time for every step of checking ID like scanning, typing etc. Accuracy: eliminate error of ID checking, possible to establish correct information database, especially for inventory handling like location and volume of the inventory. Completeness: ensure availability of relevant product information. Major airports have been considering the adoption of RFID technology for baggage handling process since 1999. Tests have been done at numerous airports/airlines in the world including Las Vegas, Jacksonville, Seattle, Los Angeles, San Francisco, Heathrow,
* Corresponding author. Tel.: +82 2 300 0150; fax: +82 2 300 0151. E-mail addresses: [email protected] (Y.S. Chang), [email protected] (M.G. Son), [email protected] (C.H. Oh). 1 Tel.: +82 2 300 0150; fax: +82 2 300 0151. 2 Tel.:+82 2 6393 0815; fax: +82 2 6393 0814. 1474-0346/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.aei.2010.05.004
Boston, New York, Gimpo-Seoul, Paris, Amsterdam, Rome and etc. In the US tests, it was turned out that RFID tags were far more accurate than bar code system when applied to baggage handling operation. Even though higher cost has prevented airports/airlines companies from adopting RFID systems, US government’s requirement (after September 11) of screening all bags for explosives has somehow changed the situation [1]. There are studies about track and trace practices in the aerospace industry which identified opportunities for improvement through the use of automatic identification (auto-id) technologies [2–4]. According to those studies, the lack of effective and efficient identification methods is one of the main reasons for poor performance. Boeing and Airbus started to working together to promote the adoption of industry standard solutions for RFID on commercial airplane parts [5]. The two manufacturers believe that RFID could provide major benefits for the entire industry. They believe that they will get more accurate information about their demand for parts. They expect the reduction of parts inventory and of repairing time for planes. Suppliers also expect the reduction of inventory, improved efficiency in their manufacturing operations and want to use RFID to verify the parts delivered to Boeing and Airbus are genuine. Airbus began RFID-tagging for its ground equipment and tools four years ago and Airbus 380 will be equipped with 10,000 radio-frequency identification chips. The aircraft will have passive RFID chips on removable parts such as passenger seats, life vests, and brakes which will aid in maintenance of those parts [6]. Standards are being developed for the wide adoption of RFID in aviation industry. The Air Transport Association (ATA) recently added an RFID standard to its SPEC2000, a comprehensive set of e-business specifications, products and services for the aviation parts industry [7]. Ngai et al. [8] reviewed 85 RFID papers and classified those papers into four areas: technological issues,
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applications areas, policy and security issues, and other issues. According to their paper, there were relatively many RFID papers on retails and libraries areas in application related articles. Chao et al. [9] also reviewed RFID researches to analyze RFID innovation, adoption by organizations, and market diffusion. According to their analysis, supply chain management (SCM), health industry, and privacy issues emerge as the major trends in RFID. Contactless, read/writable data, no line of sight, variety of read ranges, wide data-capacity range, multiple tags read and accuracy are some of the benefits using RFID other than bar code. But still there are issues to solve in the area of performance, environmental factors’ impact, tags read limitation, hardware interference, standardization and cost etc. [10]. Each year, larger cargo airlines such as Lufthansa and Air France lose 5–6% of their Unit Load Device (ULD) inventory – amounting to hundreds of millions of dollars in loss – due to breakdowns in their ULD tracking-facilities [11]. There are some articles which address the issues of poor ULD tracking and explain the value of RFID for air-cargo tracking [12–14]. Disadvantages of current practices are: need of human intervention to read and record ULD information; data errors caused by human errors; reconciliation of an ULD that goes out of a system at one airport; and lack of centralized data. Chang et al. [14] explained potential benefits of RFID for ULD management (Table 1). Due to the potential benefits of RFID and growing demand, there have been a few RFID trials in air-cargo management. Thailand’s main airport had implemented passive UHF RFID (i.e. ISO 18000-6B protocol) in the Cargo Free Zone (CFZ). In their pilot, rigid reusable plastic RFID tags are manually affixed to shipment containers and pallets of goods that require storage and must be inspected [15]. Tags are affixed to trucks in order to monitor ‘enter and exit’. The pilot was focused on the tracking of goods in CFZ area and did not consider the tracking of ULD itself which is one of the important assets in cargo operation. Air Canada had done a pilot RFID test with the following steps: tagging, loading, shipping, receiving, and unloading. They tested the loading process from varying antenna angles for read range and read rate. The reading of RFID tags in both the shipping and receiving processes provided 100% read rates. Again, in this pilot, the ULDs were not RFID tagged for proof-of-concept [16]. Hsu et al. [17] explored the customs clearance process of import cargos in international air-cargo terminals, and reconstructed the network of the customs clearance process based on the application of radio-frequency identification (RFID). In their research, the performances of RFID are evaluated in terms of reductions in shippers’ inventory cost and operators’ labor cost. There had been other academic level research on RFID application in aviation industry [18].
Even though there are a few RFID applications in air-cargo business, as Skorna and Richter [11] pointed out, aside from some local solutions and smaller pilot projects for testing purposes, no major applications yet exist in this arena. There has been a government driven RFID research project called ‘‘Ubiquitous Technology based Air-cargo Management” in Korea [19]. The aim of this project is to utilize automatic identification technologies (such as RFID, Sensor Network, barcode etc.) to elevate the efficiency and enhance air-cargo processing capabilities. The project is from 2007 to 2012 with total budget of about three million dollars. Fig. 1 shows various systems and research contents to be developed in this project. The initial goal is to improve the cargo handling process and adapt ubiquitous technology that enables visibility within the air-cargo terminal, and ultimately support the quick and accurate work process. In the figure, the dotted lines present the areas which are in development. Currently we focus on the ULD level cargo tracking as well as asset management since ULD is very expensive and important assets of air-cargo. In order to provide a globally scalable sharing data network, we adopted EPC network architectures [20] with automated business process management and also ISO standard air protocols [21,22]. In this paper, we split our discussion into four sections. In Section 2, we firstly describe characteristics of air-cargo operations and ULD in brief. Operational environment for RFID is discussed in Section 3. In Section 4, design and implementation of RFID based cargo tracking and tracing system is presented followed by conclusion. 2. Air-cargo operations and Unit Load Device (ULD) 2.1. Air-cargo operations Generally air-cargo operations consist of import area and export area [23]. The import area is dedicated to inbound freights while the export area is dedicated to outbound freights. The flow of goods through the terminal is either from the airside to the landside, from the landside to the airside, or from the airside to the airside via the terminal (for transfer). In this paper, we only focus on the export process. Air-cargo process consists of the following steps (Fig. 2): Booking: a forwarder or a shipper makes a reservation for space and weight of the aircraft. Booking is done by phone or internet. Cargo Unloading (or Receiving): the forwarder sends their cargo to the air-cargo terminal before the departure date of aircraft. Weight check: the cargo staffs weigh a cargo. Measured weight is compared with the weight previously written on master airway bill (MAWB).
Table 1 Expected advantages of RFID for ULD management. Area
Problems
Expected advantages of using RFID
ULD process
Need to check process manually several times. Hard to detect mis-loading. Manual input of data by labor at every process.
Movement management
Movement management according to an paper document ‘work order’. Input data after movement and impossible to track and trace of ULD in realtime. Incorrect ULD number checking by labor. Problems of security and safety. Prone to human error. Impossible to manage inventory in real-time. Inventory condition check by labor, 2–3 times a month. Record history of washing/repairing of ULD on paper document.
Information checking from RFID automatically. Automatic input of correct information. Paperless work process. Paperless work process. Real-time track and trace. Real-time management of ULD number. Improve security problems. Decrease human error.
Asset management
Real-time inventory control. Real-time ULD condition control. Computerized ULD history management.
system
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Fig. 1. Contents of ubiquitous technology based air-cargo management.
Fig. 2. General export processes.
Dimension check: the cargo staffs check dimension if necessary. They report a problem if there is any difference between measured data and previously written on MAWB. Security check: X-ray or other methods are taken to check security. Documentation: the forwarder submits documents concerned with export cargo. Storage: cargo is stored on storage area (the areas are divided by destinations). ULD build-up: each cargo is built up by plan. As a result, each cargo is placed on the ULD. Store ULD at ETV: If necessary, ULD is stored in Elevator Transfer Vehicle (ETV) rack. Move ULD to airside: ULD is moved to airside for loading at aircraft.
Loading ULD at aircraft: ULD is loaded to aircraft. The cargo staffs check ULD locking and packing condition. Departure: aircraft takes off by its schedule. In order to identify detail activities of each organization involved in cargo handling and data collection point, we performed detail processes study. Detail processes study can be referenced from [19]. Fig. 3 shows example of storage process. 2.2. Unit Load Device (ULD) and air-cargo Unit Load Devices (ULDs) play a vital part in ensuring that as air-cargo volumes increase; they are moved safely, quickly and cost-effectively [24]. ULD is the correct terminology used by the air transport industry for containers and loading units that are
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Fig. 3. Example of process study: storage process.
used for the carriage of cargo by air. It allows large quantities of cargo to be bundled into large units. Pallets and nettings as well as rigid containers are commonly used for freight transport by air. Each ULD is required to have a marking that identify its type code, maximum gross weight and actual tare weight. Each ULD is manifested separately so that its contents can be tracked. Currently, technical specifications for unit load devices are set by the International Air Transport Association (IATA). These relate to the dimensions, material and other characteristics of the ULD as well as issues relating to their manufacture, registration, handling and maintenance [25]. Because there are many different types of aircraft that carry cargo, as well as different possible configurations within the same aircraft type, most ULDs are specific to a particular use. Fig. 4 shows examples of commonly used ULD.
At the export area, shipments are received either loose (i.e. item level cargo, box) or as ULD shipments. ULD shipments are transferred from the feeding area to the airside area either directly or through the export storage area. ULD handling system such as ETV is generally used for storage operations. Shipments tendered loose are sent to the cart or to the ULD build-up area either directly or after being stored from any other storage areas. Generally it takes 4–24 h (emergency cargo: 1.5 h) from entering of ULDs into the terminal to loading them to a flight. All the baggage in the truck dock should be loaded 4 h before the departure time; in case of animal and perishable, cargo should be entered terminal before 2.5 h; and dangerous cargo should be stored 24 h in terminal.
Fig. 4. Example ULD types: LD3 container (left) and PMC pallet (right).
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Point D (import zone): transit zone is the place that transit cargo is managed. Cargo is classified to its destination. Point E(airside zone): airside zone is the place that ULD is loaded to aircraft.
3. Air-cargo terminal environment for RFID 3.1. Radio environment test in air-cargo terminal Air-cargo terminal may be one of the toughest environments for applying an RFID system because of various electromagnetic noise sources and its operational environment (e.g. metal container, metal pallet etc.). There were two objectives of the test. Firstly, to find out the intensity of radio waves which are closest to the frequency being used by RFID system. Secondly, to analyze how those frequencies potentially affect on the adoption of RFID system. To measure operational environment of air-cargo for RFID we used the following equipments (Table 2). In this analysis, we intentionally skipped the test of high frequencies (e.g. 125–134 kHz, 13.56 MHz) based on the user requirements. The height of antenna was set as 1.5 m (;4.92 ft) from the floor [26]. The test was measured toward four directions: north, south, east and west using LP antenna and Horn antenna. LP antenna covers from 200 MHz to 1 GHz and Horn antenna covers from 800 MHz to 18 GHz. In each direction, measuring was done two times according to the angle of antenna considering the directivity of radio wave (i.e. at each point, the tests were done 16 times by changing the angle of antennas and the direction of the LP and Horn antenna). Five spots were chosen and details are as follows (see Fig. 5). Point A(truck dock): truck dock is the place that cargo is unloaded from truck. Point B(export zone): export zone is the place that export cargo is managed. Cargo is stored and built up. Point C (transit zone): import zone is the place that import cargo is managed. Cargo is stored and divided into individual cargo. Table 2 Equipment types and specification for measuring RFID operation environment. Device types
Specification
Spectrum analyzer Log-periodic (LP) antenna Horn antenna
9 kHz – 3 GHz 200 MHz – 1 GHz 800 MHz – 18 GHz
Table 3 is the result with LP antenna at truck dock point. According to our test, 800 MHz noise was measured which was generated by cellular phone. Discontinuous noises at 242.36, 394.24 and 446.20 MHz were also found. At each direction, a spectrum analyzer was used to identify the intensity of noise around 433 and 900 MHz by changing the angle of the antenna. According to the results with Horn antenna (which was not present in this paper) at truck dock, 1.6 GHz noise was measured which was generated by PCS phone and 2.14 GHz noise was appeared which was generated by wireless LAN used by the office building close to the truck dock cargo. The results of radio environment test showed that there were some discontinuous noises which might affect RFID performance some degree in most of places in the cargo. Especially, we found noise from 800 MHz (Noise from cellular phone), 1.6 GHz (Noise from PCS phone), 446.20 MHz (Noise from Walkie Talkie) and also quite strong noise around 2.45 GHz (Noise from wireless device and other device) at transit point. By understanding the radio environment we could predict the potential impact of radio environment and make careful decision for implementation technology. 3.2. Operational environment of air-cargo As Tzeng et al. [27] and Porter et al.[28] addressed real world environment for RFID is quite different from laboratory environment. There are several tag requirements according to US military specification such as low temperature, high temperature, mechanical shock, humidity, drop test and etc. [29]. In our study, we found that there were some areas that we had to consider practical operational condition additionally. For example, ULDs are going to cleaning station with 90 °C for 3 min and also tag need harsh condition for unexpected shock by forklift and other force. Compared to container type ULD, pallet type ULD is hard to mount RFID tag and hard to trace information because quite frequently RFID tag is covered by packaging materials. Fig. 6 shows recommended
Fig. 5. Test area at cargo terminal.
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Table 3 Example spectrum result for truck dock (200 MHz-1 GHz). Point
Antenna type
Direction
Antenna angle
LP LP LP LP LP LP LP LP
East East West West South South North North
Vertical Horizon Vertical Horizon Vertical Horizon Vertical Horizon
Result Noise around 433 MHz
1 2 3 4 5 6 7 8
Truck Truck Truck Truck Truck Truck Truck Truck
dock dock dock dock dock dock dock dock
antenna antenna antenna antenna antenna antenna antenna antenna
73.07 dbm 72.39 dbm 74.59 dbm 72.60 dbm 73.65 dbm 73.31 dbm 73.49 dbm 73.68 dbm
Noise around 900 MHz 63.96 dbm 64.96 dbm 63.10 dbm 64.90 dbm 65.22 dbm 64.54 dbm 64.85 dbm 65.05 dbm
Fig. 6. Tag location for air pallet and tag install location.
Fig. 7. 433 MHz tag developed for this project.
tag installation location for pallet [30] and the detail shape of stud hall (left figure) and example requirement for tag installation to protect its package (right figure). Fig. 7 shows 433 MHz tag developed in our project. To prevent unexpected shock by forklift, we used acrylonitrile–butadiene–styrene (ABS) and designed the tag package to be inserted in the hall with researchable battery. Table 4 shows detail specification of RFID tag developed. In order to choose proper RFID technology for our pilot implementation, we have performed a benchmarking test in the cargo with different hardware which uses different frequencies. Table 5 shows brief description of test parameters and equipment. In this test, 900 MHz system was based on the ISO 18000-6C protocol; 2.45 GHz system was based on ISO 18000-4 protocol (mode 2: with battery); and 433 MHz system was based on ISO 18000-7 protocol. Directivity was tested for 0° and 30° while tug car speed test was for 11 km/h which was suggested by airlines. According to our test, at truck dock, a target object was identified 100% from 1 m and over 93% of reading reliability was achieved from 2 and 3 m with 900 MHz system. At storage area, a target object was identified 100% from 1 m and over 90% of
Table 4 Specification of RFID tag developed. Environmental
Temperature Humidity
Operating: 20 °C – +60 °C storage: 20 °C – +60 °C 70% at 50 °C
UHF transmit/receiver
Frequency Range Air protocol Modulation Data rate Data coding Antenna Detail
433.92 MHz Up to 20 m ISO 18000-7 air protocol FSK, deviation ±50kHz 27.7 Kbps Manchester Chip antenna Wakeup and response is 433 MHz only
Digital (option)
User memory Tag ID User ID
Maximum 8 Kbytes 4 Bytes (RO) 16 Bytes (R/W)
Power
Battery TX/RX Sleep Battery life
3.6 Volt lithium, rechargeable 22 mA 5–8 lA 6 months (3 events/day)
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Fig. 8. Example of control layer (left) and presentation layer (right) developed.
reading reliability was achieved from 2 m (but 0% from 3 m) with 900 MHz system. The reason why we only tested 900 MHz system for truck dock area and for storage area is that all cargo is carried by skid or by box in those areas (currently for skid and box level 900 MHz is widely used). At workstation, there exist both skid/box and ULD (container or pallet) which might need different technologies. Especially ULD is made of metal which might impact on the reading reliability. At workstation, ULD was identified over 93% from 1 m but only 80% of reading reliability was achieved from 2 m with 900 MHz system (but 0% from 3 m). But with 433 MHz, 100% reading reliability was achieved. With 2.45 GHz system, 93% of reading reliability was achieved. At airside gate, only 433 MHz system achieved 100% while 900 MHz system and 2.45 GHz system achieved around 90%. It is considered that such difference came from the robustness of the system against operational environment and metal environment.
4. Design and implementation of RFID based cargo monitoring system 4.1. Design of RFID based cargo monitoring system RFID based monitoring systems consists of physical layer, control layer and presentation layer. Physical layer includes automatic identification data capturing (e.g. RFID, barcode etc.) and middleware which filters and transfer real-time data. In order to meet the global standard, we adopt EPC ALE specification [31]. Control layer supports to transform the raw level real-time data into information. In this layer, we embraced the concept of business process modeling (BPM) and EPCIS [20] in order to automate various business processes for users and to share the real-time data globally. Presentation layer provides information to the users. Examples are Dashboard, 3D cargo track and trace, real-time cargo information and asset management. Fig. 8 shows examples of control layer (BPM) and presentation layer (Dashboard) developed in this project. Details of RFID based cargo monitoring system will be addressed in the followings subsections.
Table 5 Test parameters and equipment. Test location
Target object
Equipment
Parameter
Truck dock
Item level (box), skid
900 MHz
Storage
Item level (box), skid, forklift
900 MHz
Work station
Item level (box), ULD, forklift
Airside gate
ULD, tug car
900 MHz, 433 MHz, 2.45 GHz 900 MHz, 433 MHz, 2.45 GHz
Reading distance directivity of antenna, reading reliability Reading distance, directivity of antenna, speed of tug car, reading reliability Reading distance, directivity of antenna, reading reliability Speed of tug car, reading reliability
Automatic Identification and Data Capture (RFID, barcode) based data. Manual input data by human resource. Synchronized data: data which was synchronized with relevant data in the application system (synchronization is preprocessed). In Table 7, descriptions of each data are as follows: Business location identification data: a process location where an event is occurred. Location identification data: a physical location (spatial) where a cargo is located when an event is occurred. ULD identification data: a unique identification data for a ULD which is operated in the given event. SKID identification data: a unique identification data for a SKID cargo which is operated in the given event. MAWB identification data: a master airway bill identification data required to synchronize document information and physical cargo information. Time data: a timestamp history for each event. Table 8 shows data model developed for our cargo monitoring system which is based on the EPC network [20].
4.2. Event and design of EPC based data model 4.3. Implementation of RFID based cargo monitoring system In order to monitor each process with RFID system, firstly we define ‘‘event” for a specific process. In our research, data for event is mostly collected by RFID in real-time mode (Table 6). In monitoring a cargo, we classified data considering data collection mode (Table 7). Details are as follows:
Trappey et al. [32] introduced an agent-based collaborative mold production (ACMP) system which supports the collaborative and autonomous mold manufacturing out sourcing processes. ACMP provided autonomous features to handle three major tasks
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Table 6 Process, event and data. Process
Event
Data (nominal data for defining event)
Arrival (receiving and check)
Arrival
Storage
Storage
Build-up
Build-up
ETV-in (loading)
ETV-in (loading)
Airside
ETV-out
Table 7 Classification of required data type. AIDC data (RFID)
Business location identification data Location identification data
ULD identification data SKID identification data MAWB identification data Time data
Business location identification data. MAWB identification data. SKID identification data. Time data. Business location identification data. Location (specific storage number in storage area) identification data. MAWB identification data. SKID identification data. Time data. Business location identification data. Location (specific workstation number in workstation area) identification data. ULD identification data. MAWB identification data. SKID identification data. Time data. Business location identification data. Location (specific rack location in ETV area) identification data. ULD identification data. MAWB identification data. SKID identification data. Time data. Business location identification data. ULD identification data. MAWB identification data. SKID identification data. Time data.
Table 8 EPC network based data model for cargo monitoring.
Required data
Input data
Synchronized data
Event
Nominal data
EPC data model
Arrival
Business location identification data MAWB identification data
ReadPointID
SKID identification data Time data
Child EPCs Event time/ record time
Business location identification data SKID identification data Location identification data Time data
ReadPointID
Business location identification data ULD identification data SKID identification data Location identification data Time data
ReadPointID
Business location identification data ULD identification data Location identification data Time data
ReadPointID
Business location identification data ULD identification data Time data
ReadPointID
Rack location when loading a cargo in the ETV
MAWB No.
Storage
in outsourcing: vendor selection, task selection, and real-time outsourcing task progress tracking. In their development, RFID technology was adopted to provide a real-time tracking capability for remote collaboration, control and monitoring among outsourcing partners. They demonstrated a methodology to transform the physical process flow into information flow by taking the advantage of RFID technology. In our development, the RFID based cargo monitoring solution embraces FLEX and JAVA with Spring and Hibernate Framework. Fig. 9 show brief logical architectures of monitoring solution. As in Fig. 9, RFID system consists of reader, antenna and tag. Once reader identifies tags, reader sends a tag data to RFID middleware. For RFID code, we used SGLN for location, SGTIN for BOX, SSCC for ULD [33]. RFID middleware filters the data and send it to capturing application after converting it to ECreports data type. Capturing application reconstruct EPCIS data from the ECreports data, send the data to BPM and EPCIS according to the predefined capturing rule. After receiving EPCIS data, BPM helps cargo monitoring solution to perform next process. EPCIS stores EPCIS data and timestamp. Monitoring solution displays cargo information. Fig. 10 shows a Java Messaging Service (JMS) application, to send RFID ALE event to BPM and during the pilot, we transferred events
Buildup
ETV-in
ETVout
Parent ID
Comments
Input data (MAWB No.)
Parent ID Child EPCs Event time/ record time
Parent ID Child EPCs Child EPCs Event time/ record time
Parent ID Child EPCs
Input data (ETV rack No.)
Event time/ record time
Parent ID Event time/ record time
in real-time without failure. In the figure, the event triggered when assets are not placed as planned. Fig. 11 shows a physical architecture of cargo monitoring system installed at Incheon Airport during our pilot. In the figure
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Fig. 9. Logical architecture of cargo monitoring solution.
‘‘433” stands for 433 MHz reader, ‘‘Blackfish” stands for RFID tag printer installed, other numbers are IP addresses. Details are as follows (also see Table 9): Desktop, UMPC (Ultra Mobile PC). 900 MHz RFID stationary reader, antenna and mobile reader; tag printer. 433 MHz RFID reader and antenna. Tag: 900 MHz tag and 433 MHz tag. RFID code: SGLN, SGTIN, and SSCC. Table 9 shows types of hardware installed in each process. Fig. 12 shows implementation workflow. After receiving customer order, booking list is generated for each air flight. Each skid information has mapped with air flight number in the database. After weighing and security check, an operator reads RFID tag attached at cargo and ‘‘end” information of inspection process is stored in the monitoring system. At storage area, SGLN code is used for location identification. Once tag attached at cargo is identified, the system recognizes that the cargo is in the same area as SGLN code. At workstation area, build-up plan is generated considering ULD, SKID information and build-up list. In this area, 433 MHz system and 900 MHz system are used together. 433 MHz system reads ULD information while 900 MHz system reads SKID information during build-up process. After build-up, completed ULD is loaded to Transfer Vehicle (TV), transferred to ETV by TV. At ETV entrance, RFID system in front of ETV gate identified ULD tag, and then the system makes decision for the ULD location in the ETV rack. At airside gate, RFID system at gate identifies when some ULD is moving out and sends the information to the monitoring system. Fig. 13 shows database diagram for cargo monitoring solution. For implementation, Oracle 10 g database was used in this application.
Air-cargo monitoring solution application (i.e. presentation layer application) consists of real-time cargo information (e.g. booking list application, inspection application, build planning application, build list application etc.), dash board application, asset management application and 3D cargo track and trace application. Fig. 14 shows screen shots of build planning application and 3D cargo track and trace application. 5. Conclusion In this paper, we introduced a RFID system based cargo monitoring system. We have presented a result of RF environment study for a cargo and an EPC network based cargo monitoring system we developed. From our RF environment study, it is considered that careful study on operational environment should be preceded before individual implementation. Even though the development is still ongoing, during our pilot, one of our partners (airline companies in Korea) found potential benefits of RFID based cargo monitoring solution as follows: Increasing visibility in cargo: capability to find location of a specific cargo. Capability to expedite late cargo, visualization effect of cargo, real-time update of cargo information. In the past, it was impossible to find the location of missing ULD. After applying RFID, by using the last-known location of a missing ULD together with process routing, the airlines have reduced the search time drastically. Cost saving related to operation of air-cargo process: elimination of manual data entry and manual error. By applying RFID, the airlines expect to remove manual input processes. Cost saving related to asset management: physical ULD counting, ULD write-off reduction, reduction in ULD carrying cost from exact identification of ULD quantity, ULD lifecycle management.
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Fig. 10. Example JMS logic for to send ALE to BPM.
Fig. 11. Physical architecture of cargo monitoring system.
Y.S. Chang et al. / Advanced Engineering Informatics 25 (2011) 41–52 Table 9 Hardware used for implementation. Process
Tracking level
Frequency
Type
Inspection Storage Workstation
SKID SKID SKID ULD ULD ULD
900 MHz 900 MHz 900MHz 433 MHz 433 MHz 433 MHz
Stationary and mobile Mobile Stationary
ETV entrance Airside gate
Stationary Stationary
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With the specific installation method developed during this project, the companies expect to improve their capability on asset management. As pointed previously, there are a few researches in air-cargo business, most of them had focused on the simple track and trace of goods, the reading accuracy test, but did not address the radio environment of air-cargo terminal and did not show pictures of global data sharing networks. In this paper, we explained RFID
Fig. 12. Implementation workflow considering system architecture and cargo process.
Fig. 13. Data base diagram for pilot implementation.
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Fig. 14. Build-up planning and 3D ULD monitoring.
based air-cargo monitoring system with real world pilot implementation. We believe that our research will bring a guideline for RFID adoption in the air-cargo operation which requires harsh and robust operating environments. Acknowledgements The authors thank to the anonymous reviewers for valuable comments. This research was supported by a Grant (36-2007-CAirport) from Development for the Intelligent Airport System Program funded by Ministry of Land, Transport and Maritime Affairs of Korean government. References [1] J. Collins, Delta Plans US-wide RFID System, RFID Journal. Available from:. [7] M. Roberti, ATA Approves RFID Data Structures for SPEC 2000. Available from: . [8] E.W.T. Ngai, K.K.L. Moon, F.J. Riggins, C.Y. Yi, RFID research: an academic literature review (1995–2005) and future research directions, International Journal of Production Economics 112 (2008) 510–520. [9] C. Chao, J. Yang, W. Jen, Determining technology trends and forecasts of RFID by a historical review and bibliometric analysis from 1991 to 2005, Technovation 27 (2007) 268–279. [10] S. Lahiri, RFID Source Book, Prentice Hall PTR, New Jersey, 2005. [11] A.C.H. Skorna, A. Richter, RFID and Air Cargo. Available from: . [13] P.N. Pandit, RFID for Air Cargo. Available from:
[14] Y.S. Chang, U.Y. Park, C.A. Kwon, J.J. Lee, S.W. Lee, V. Kumar, Developing test methods for RFID equipments for air cargo terminal operations, CD ROM, in: Proceedings of the International Conference on Logistics and Supply Chain Management, Hong Kong, January 4–7, 2006. [15] B. Bacheldor, Thai Airport Tests RFID to Track Cargo Streamline Customs, RFID Journal. Available from:. [16] Franwell, Case Study: Air Canada Cargo RFID Technology Pilot, White Paper. Available from: . [17] C. Hsu, H. Shih, W. Wang, Applying RFID to reduce delay in import cargo customs clearance process, Computers and Industrial Engineering 57 (2) (2009) 506–519. [18] S.B. Yoon, Y.S. Chang, J.Y. Kim, K.Y. Chung, H.S. Lee, Y.S. Hwang, C.H. Oh, V. Kumar, Real time inventory management system in aviation industry, CD ROM, in: Proceedings of the International Conference on Logistics and Supply Chain Management, Hong Kong, January 4–7, 2006. [19] Korea Aerospace University, Ubiquitous Technology-based Air Cargo Management System Development, Construction and Transportation R&D Report, R&D/ 36-2007-C-Airport, 2009. [20] EPC Global Inc., The EPCglobal Architecture Framework, Final Version 1.2, September 2007. [21] ISO, 2006, ISO/IEC 18000-6:2004/Amd 1:2006. Available from: . [22] ISO, 2004, ISO/IEC 18000-7:2004. Available from: . [23] A.L. Nsakanda, M. Turcotte, M. Diaby, Air cargo operations evaluation and analysis through simulation, in: R.G. Ingalls, M.D. Rossetti, J.S. Smith, B.A. Peters (Eds.), Proceedings of the 2004 Winter Simulation Conference, December 5–8, 2004, pp. 1790–1798. [24] IATA, IATA ULD Technical Manual 19th Edition, Montreal, Canada (ISBN 929195-273-72004). [25] IATA. Available from: . [26] ISO/IEC, ISO/IEC TR 18046, Information Technology – Automatic Identification and Data Capture Techniques – Radio Frequency Identification Device Performance Test Methods, 2005. [27] C.T. Tzeng, Y.C. Chiang, C.M. Chiang, C.M. Lai, Combination of radio frequency identification (RFID) and field verification tests of interior decorating materials, Automation in Construction 18 (2008) 16–23. [28] J.D. Porter, R.E. Billo, M.H. Mickle, A standard test protocol for evaluation of radio frequency identification systems for supply chain applications, Journal of Manufacturing System 23 (1) (2004) 46–55. [29] US DoD, Mil-STD-810F: Department of Defense Test Method Standard for Environmental Engineering Considerations and Laboratory Tests, US Department of Defense (DoD) (01.01.2000). [30] IATA, IATA Recommended Practice 1640, 2004. [31] EPC Global Inc., The Application Level Events (ALE) Specification, Version 1.0, 2005. [32] A.J.C. Trappey, T.H. Lu, L.D. Fu, Development of an intelligent agent system for collaborative mold production with RFID technology, Robotics and ComputerIntegrated Manufacturing 25 (2009) 42–56. [33] EPC Global Inc., EPCglobal Tag Data Standards Version 1.4, June 11, 2008.
Contents lists available at ScienceDirect
Advanced Engineering Informatics journal homepage: www.elsevier.com/locate/aei
Design and implementation of RFID based air-cargo monitoring system Yoon Seok Chang a,*, Min Gyu Son a,1, Chang Heun Oh b,2 a Ubiquitous Technology Application Research Center, School of Air Transport, Transportation and Logistics, Korea Aerospace University, 100 Hanggongdae-gil, Goyang-City 412-791, Republic of Korea b EXIS Software Engineering, #1801, Building 2, DMC Iaan Sang-am, 1653 Sangam-dong, Mapo-gu, Republic of Korea
a r t i c l e
i n f o
Article history: Received 15 November 2009 Received in revised form 1 April 2010 Accepted 7 May 2010 Available online 25 June 2010
a b s t r a c t This paper deals with the design and implementation of radio-frequency identification (RFID) based cargo monitoring system which supports tracking and tracing in air-cargo operation. In order to apply a proper RFID technology, firstly we studied RF operational environment and tested different RFID frequencies. After finding a right technology (i.e. frequency), we designed and implemented tracking and tracing system applying EPC networks. We believe that our research will bring a guideline for developing RFID based tracking system for cargo operation. Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction To survive in today’s highly competitive business world, the speed of operation/delivery and high level of customer service, visibility across enterprises boundaries as well as across countries are considered as key factors. Due to such reason, the importance of air transport is becoming more and more emphasized. However, due to higher cost than other transportation methods, various technologies have been investigated to maximize its process efficiency. Among them, RFID system is getting more attention because of its distinctive capabilities compared to the traditional barcode system: Uniqueness: enable unique product identification, distinguish every single product by its ID. Timeless: reduce/eliminate time for every step of checking ID like scanning, typing etc. Accuracy: eliminate error of ID checking, possible to establish correct information database, especially for inventory handling like location and volume of the inventory. Completeness: ensure availability of relevant product information. Major airports have been considering the adoption of RFID technology for baggage handling process since 1999. Tests have been done at numerous airports/airlines in the world including Las Vegas, Jacksonville, Seattle, Los Angeles, San Francisco, Heathrow,
* Corresponding author. Tel.: +82 2 300 0150; fax: +82 2 300 0151. E-mail addresses: [email protected] (Y.S. Chang), [email protected] (M.G. Son), [email protected] (C.H. Oh). 1 Tel.: +82 2 300 0150; fax: +82 2 300 0151. 2 Tel.:+82 2 6393 0815; fax: +82 2 6393 0814. 1474-0346/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.aei.2010.05.004
Boston, New York, Gimpo-Seoul, Paris, Amsterdam, Rome and etc. In the US tests, it was turned out that RFID tags were far more accurate than bar code system when applied to baggage handling operation. Even though higher cost has prevented airports/airlines companies from adopting RFID systems, US government’s requirement (after September 11) of screening all bags for explosives has somehow changed the situation [1]. There are studies about track and trace practices in the aerospace industry which identified opportunities for improvement through the use of automatic identification (auto-id) technologies [2–4]. According to those studies, the lack of effective and efficient identification methods is one of the main reasons for poor performance. Boeing and Airbus started to working together to promote the adoption of industry standard solutions for RFID on commercial airplane parts [5]. The two manufacturers believe that RFID could provide major benefits for the entire industry. They believe that they will get more accurate information about their demand for parts. They expect the reduction of parts inventory and of repairing time for planes. Suppliers also expect the reduction of inventory, improved efficiency in their manufacturing operations and want to use RFID to verify the parts delivered to Boeing and Airbus are genuine. Airbus began RFID-tagging for its ground equipment and tools four years ago and Airbus 380 will be equipped with 10,000 radio-frequency identification chips. The aircraft will have passive RFID chips on removable parts such as passenger seats, life vests, and brakes which will aid in maintenance of those parts [6]. Standards are being developed for the wide adoption of RFID in aviation industry. The Air Transport Association (ATA) recently added an RFID standard to its SPEC2000, a comprehensive set of e-business specifications, products and services for the aviation parts industry [7]. Ngai et al. [8] reviewed 85 RFID papers and classified those papers into four areas: technological issues,
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applications areas, policy and security issues, and other issues. According to their paper, there were relatively many RFID papers on retails and libraries areas in application related articles. Chao et al. [9] also reviewed RFID researches to analyze RFID innovation, adoption by organizations, and market diffusion. According to their analysis, supply chain management (SCM), health industry, and privacy issues emerge as the major trends in RFID. Contactless, read/writable data, no line of sight, variety of read ranges, wide data-capacity range, multiple tags read and accuracy are some of the benefits using RFID other than bar code. But still there are issues to solve in the area of performance, environmental factors’ impact, tags read limitation, hardware interference, standardization and cost etc. [10]. Each year, larger cargo airlines such as Lufthansa and Air France lose 5–6% of their Unit Load Device (ULD) inventory – amounting to hundreds of millions of dollars in loss – due to breakdowns in their ULD tracking-facilities [11]. There are some articles which address the issues of poor ULD tracking and explain the value of RFID for air-cargo tracking [12–14]. Disadvantages of current practices are: need of human intervention to read and record ULD information; data errors caused by human errors; reconciliation of an ULD that goes out of a system at one airport; and lack of centralized data. Chang et al. [14] explained potential benefits of RFID for ULD management (Table 1). Due to the potential benefits of RFID and growing demand, there have been a few RFID trials in air-cargo management. Thailand’s main airport had implemented passive UHF RFID (i.e. ISO 18000-6B protocol) in the Cargo Free Zone (CFZ). In their pilot, rigid reusable plastic RFID tags are manually affixed to shipment containers and pallets of goods that require storage and must be inspected [15]. Tags are affixed to trucks in order to monitor ‘enter and exit’. The pilot was focused on the tracking of goods in CFZ area and did not consider the tracking of ULD itself which is one of the important assets in cargo operation. Air Canada had done a pilot RFID test with the following steps: tagging, loading, shipping, receiving, and unloading. They tested the loading process from varying antenna angles for read range and read rate. The reading of RFID tags in both the shipping and receiving processes provided 100% read rates. Again, in this pilot, the ULDs were not RFID tagged for proof-of-concept [16]. Hsu et al. [17] explored the customs clearance process of import cargos in international air-cargo terminals, and reconstructed the network of the customs clearance process based on the application of radio-frequency identification (RFID). In their research, the performances of RFID are evaluated in terms of reductions in shippers’ inventory cost and operators’ labor cost. There had been other academic level research on RFID application in aviation industry [18].
Even though there are a few RFID applications in air-cargo business, as Skorna and Richter [11] pointed out, aside from some local solutions and smaller pilot projects for testing purposes, no major applications yet exist in this arena. There has been a government driven RFID research project called ‘‘Ubiquitous Technology based Air-cargo Management” in Korea [19]. The aim of this project is to utilize automatic identification technologies (such as RFID, Sensor Network, barcode etc.) to elevate the efficiency and enhance air-cargo processing capabilities. The project is from 2007 to 2012 with total budget of about three million dollars. Fig. 1 shows various systems and research contents to be developed in this project. The initial goal is to improve the cargo handling process and adapt ubiquitous technology that enables visibility within the air-cargo terminal, and ultimately support the quick and accurate work process. In the figure, the dotted lines present the areas which are in development. Currently we focus on the ULD level cargo tracking as well as asset management since ULD is very expensive and important assets of air-cargo. In order to provide a globally scalable sharing data network, we adopted EPC network architectures [20] with automated business process management and also ISO standard air protocols [21,22]. In this paper, we split our discussion into four sections. In Section 2, we firstly describe characteristics of air-cargo operations and ULD in brief. Operational environment for RFID is discussed in Section 3. In Section 4, design and implementation of RFID based cargo tracking and tracing system is presented followed by conclusion. 2. Air-cargo operations and Unit Load Device (ULD) 2.1. Air-cargo operations Generally air-cargo operations consist of import area and export area [23]. The import area is dedicated to inbound freights while the export area is dedicated to outbound freights. The flow of goods through the terminal is either from the airside to the landside, from the landside to the airside, or from the airside to the airside via the terminal (for transfer). In this paper, we only focus on the export process. Air-cargo process consists of the following steps (Fig. 2): Booking: a forwarder or a shipper makes a reservation for space and weight of the aircraft. Booking is done by phone or internet. Cargo Unloading (or Receiving): the forwarder sends their cargo to the air-cargo terminal before the departure date of aircraft. Weight check: the cargo staffs weigh a cargo. Measured weight is compared with the weight previously written on master airway bill (MAWB).
Table 1 Expected advantages of RFID for ULD management. Area
Problems
Expected advantages of using RFID
ULD process
Need to check process manually several times. Hard to detect mis-loading. Manual input of data by labor at every process.
Movement management
Movement management according to an paper document ‘work order’. Input data after movement and impossible to track and trace of ULD in realtime. Incorrect ULD number checking by labor. Problems of security and safety. Prone to human error. Impossible to manage inventory in real-time. Inventory condition check by labor, 2–3 times a month. Record history of washing/repairing of ULD on paper document.
Information checking from RFID automatically. Automatic input of correct information. Paperless work process. Paperless work process. Real-time track and trace. Real-time management of ULD number. Improve security problems. Decrease human error.
Asset management
Real-time inventory control. Real-time ULD condition control. Computerized ULD history management.
system
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Fig. 1. Contents of ubiquitous technology based air-cargo management.
Fig. 2. General export processes.
Dimension check: the cargo staffs check dimension if necessary. They report a problem if there is any difference between measured data and previously written on MAWB. Security check: X-ray or other methods are taken to check security. Documentation: the forwarder submits documents concerned with export cargo. Storage: cargo is stored on storage area (the areas are divided by destinations). ULD build-up: each cargo is built up by plan. As a result, each cargo is placed on the ULD. Store ULD at ETV: If necessary, ULD is stored in Elevator Transfer Vehicle (ETV) rack. Move ULD to airside: ULD is moved to airside for loading at aircraft.
Loading ULD at aircraft: ULD is loaded to aircraft. The cargo staffs check ULD locking and packing condition. Departure: aircraft takes off by its schedule. In order to identify detail activities of each organization involved in cargo handling and data collection point, we performed detail processes study. Detail processes study can be referenced from [19]. Fig. 3 shows example of storage process. 2.2. Unit Load Device (ULD) and air-cargo Unit Load Devices (ULDs) play a vital part in ensuring that as air-cargo volumes increase; they are moved safely, quickly and cost-effectively [24]. ULD is the correct terminology used by the air transport industry for containers and loading units that are
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Fig. 3. Example of process study: storage process.
used for the carriage of cargo by air. It allows large quantities of cargo to be bundled into large units. Pallets and nettings as well as rigid containers are commonly used for freight transport by air. Each ULD is required to have a marking that identify its type code, maximum gross weight and actual tare weight. Each ULD is manifested separately so that its contents can be tracked. Currently, technical specifications for unit load devices are set by the International Air Transport Association (IATA). These relate to the dimensions, material and other characteristics of the ULD as well as issues relating to their manufacture, registration, handling and maintenance [25]. Because there are many different types of aircraft that carry cargo, as well as different possible configurations within the same aircraft type, most ULDs are specific to a particular use. Fig. 4 shows examples of commonly used ULD.
At the export area, shipments are received either loose (i.e. item level cargo, box) or as ULD shipments. ULD shipments are transferred from the feeding area to the airside area either directly or through the export storage area. ULD handling system such as ETV is generally used for storage operations. Shipments tendered loose are sent to the cart or to the ULD build-up area either directly or after being stored from any other storage areas. Generally it takes 4–24 h (emergency cargo: 1.5 h) from entering of ULDs into the terminal to loading them to a flight. All the baggage in the truck dock should be loaded 4 h before the departure time; in case of animal and perishable, cargo should be entered terminal before 2.5 h; and dangerous cargo should be stored 24 h in terminal.
Fig. 4. Example ULD types: LD3 container (left) and PMC pallet (right).
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Point D (import zone): transit zone is the place that transit cargo is managed. Cargo is classified to its destination. Point E(airside zone): airside zone is the place that ULD is loaded to aircraft.
3. Air-cargo terminal environment for RFID 3.1. Radio environment test in air-cargo terminal Air-cargo terminal may be one of the toughest environments for applying an RFID system because of various electromagnetic noise sources and its operational environment (e.g. metal container, metal pallet etc.). There were two objectives of the test. Firstly, to find out the intensity of radio waves which are closest to the frequency being used by RFID system. Secondly, to analyze how those frequencies potentially affect on the adoption of RFID system. To measure operational environment of air-cargo for RFID we used the following equipments (Table 2). In this analysis, we intentionally skipped the test of high frequencies (e.g. 125–134 kHz, 13.56 MHz) based on the user requirements. The height of antenna was set as 1.5 m (;4.92 ft) from the floor [26]. The test was measured toward four directions: north, south, east and west using LP antenna and Horn antenna. LP antenna covers from 200 MHz to 1 GHz and Horn antenna covers from 800 MHz to 18 GHz. In each direction, measuring was done two times according to the angle of antenna considering the directivity of radio wave (i.e. at each point, the tests were done 16 times by changing the angle of antennas and the direction of the LP and Horn antenna). Five spots were chosen and details are as follows (see Fig. 5). Point A(truck dock): truck dock is the place that cargo is unloaded from truck. Point B(export zone): export zone is the place that export cargo is managed. Cargo is stored and built up. Point C (transit zone): import zone is the place that import cargo is managed. Cargo is stored and divided into individual cargo. Table 2 Equipment types and specification for measuring RFID operation environment. Device types
Specification
Spectrum analyzer Log-periodic (LP) antenna Horn antenna
9 kHz – 3 GHz 200 MHz – 1 GHz 800 MHz – 18 GHz
Table 3 is the result with LP antenna at truck dock point. According to our test, 800 MHz noise was measured which was generated by cellular phone. Discontinuous noises at 242.36, 394.24 and 446.20 MHz were also found. At each direction, a spectrum analyzer was used to identify the intensity of noise around 433 and 900 MHz by changing the angle of the antenna. According to the results with Horn antenna (which was not present in this paper) at truck dock, 1.6 GHz noise was measured which was generated by PCS phone and 2.14 GHz noise was appeared which was generated by wireless LAN used by the office building close to the truck dock cargo. The results of radio environment test showed that there were some discontinuous noises which might affect RFID performance some degree in most of places in the cargo. Especially, we found noise from 800 MHz (Noise from cellular phone), 1.6 GHz (Noise from PCS phone), 446.20 MHz (Noise from Walkie Talkie) and also quite strong noise around 2.45 GHz (Noise from wireless device and other device) at transit point. By understanding the radio environment we could predict the potential impact of radio environment and make careful decision for implementation technology. 3.2. Operational environment of air-cargo As Tzeng et al. [27] and Porter et al.[28] addressed real world environment for RFID is quite different from laboratory environment. There are several tag requirements according to US military specification such as low temperature, high temperature, mechanical shock, humidity, drop test and etc. [29]. In our study, we found that there were some areas that we had to consider practical operational condition additionally. For example, ULDs are going to cleaning station with 90 °C for 3 min and also tag need harsh condition for unexpected shock by forklift and other force. Compared to container type ULD, pallet type ULD is hard to mount RFID tag and hard to trace information because quite frequently RFID tag is covered by packaging materials. Fig. 6 shows recommended
Fig. 5. Test area at cargo terminal.
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Table 3 Example spectrum result for truck dock (200 MHz-1 GHz). Point
Antenna type
Direction
Antenna angle
LP LP LP LP LP LP LP LP
East East West West South South North North
Vertical Horizon Vertical Horizon Vertical Horizon Vertical Horizon
Result Noise around 433 MHz
1 2 3 4 5 6 7 8
Truck Truck Truck Truck Truck Truck Truck Truck
dock dock dock dock dock dock dock dock
antenna antenna antenna antenna antenna antenna antenna antenna
73.07 dbm 72.39 dbm 74.59 dbm 72.60 dbm 73.65 dbm 73.31 dbm 73.49 dbm 73.68 dbm
Noise around 900 MHz 63.96 dbm 64.96 dbm 63.10 dbm 64.90 dbm 65.22 dbm 64.54 dbm 64.85 dbm 65.05 dbm
Fig. 6. Tag location for air pallet and tag install location.
Fig. 7. 433 MHz tag developed for this project.
tag installation location for pallet [30] and the detail shape of stud hall (left figure) and example requirement for tag installation to protect its package (right figure). Fig. 7 shows 433 MHz tag developed in our project. To prevent unexpected shock by forklift, we used acrylonitrile–butadiene–styrene (ABS) and designed the tag package to be inserted in the hall with researchable battery. Table 4 shows detail specification of RFID tag developed. In order to choose proper RFID technology for our pilot implementation, we have performed a benchmarking test in the cargo with different hardware which uses different frequencies. Table 5 shows brief description of test parameters and equipment. In this test, 900 MHz system was based on the ISO 18000-6C protocol; 2.45 GHz system was based on ISO 18000-4 protocol (mode 2: with battery); and 433 MHz system was based on ISO 18000-7 protocol. Directivity was tested for 0° and 30° while tug car speed test was for 11 km/h which was suggested by airlines. According to our test, at truck dock, a target object was identified 100% from 1 m and over 93% of reading reliability was achieved from 2 and 3 m with 900 MHz system. At storage area, a target object was identified 100% from 1 m and over 90% of
Table 4 Specification of RFID tag developed. Environmental
Temperature Humidity
Operating: 20 °C – +60 °C storage: 20 °C – +60 °C 70% at 50 °C
UHF transmit/receiver
Frequency Range Air protocol Modulation Data rate Data coding Antenna Detail
433.92 MHz Up to 20 m ISO 18000-7 air protocol FSK, deviation ±50kHz 27.7 Kbps Manchester Chip antenna Wakeup and response is 433 MHz only
Digital (option)
User memory Tag ID User ID
Maximum 8 Kbytes 4 Bytes (RO) 16 Bytes (R/W)
Power
Battery TX/RX Sleep Battery life
3.6 Volt lithium, rechargeable 22 mA 5–8 lA 6 months (3 events/day)
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Fig. 8. Example of control layer (left) and presentation layer (right) developed.
reading reliability was achieved from 2 m (but 0% from 3 m) with 900 MHz system. The reason why we only tested 900 MHz system for truck dock area and for storage area is that all cargo is carried by skid or by box in those areas (currently for skid and box level 900 MHz is widely used). At workstation, there exist both skid/box and ULD (container or pallet) which might need different technologies. Especially ULD is made of metal which might impact on the reading reliability. At workstation, ULD was identified over 93% from 1 m but only 80% of reading reliability was achieved from 2 m with 900 MHz system (but 0% from 3 m). But with 433 MHz, 100% reading reliability was achieved. With 2.45 GHz system, 93% of reading reliability was achieved. At airside gate, only 433 MHz system achieved 100% while 900 MHz system and 2.45 GHz system achieved around 90%. It is considered that such difference came from the robustness of the system against operational environment and metal environment.
4. Design and implementation of RFID based cargo monitoring system 4.1. Design of RFID based cargo monitoring system RFID based monitoring systems consists of physical layer, control layer and presentation layer. Physical layer includes automatic identification data capturing (e.g. RFID, barcode etc.) and middleware which filters and transfer real-time data. In order to meet the global standard, we adopt EPC ALE specification [31]. Control layer supports to transform the raw level real-time data into information. In this layer, we embraced the concept of business process modeling (BPM) and EPCIS [20] in order to automate various business processes for users and to share the real-time data globally. Presentation layer provides information to the users. Examples are Dashboard, 3D cargo track and trace, real-time cargo information and asset management. Fig. 8 shows examples of control layer (BPM) and presentation layer (Dashboard) developed in this project. Details of RFID based cargo monitoring system will be addressed in the followings subsections.
Table 5 Test parameters and equipment. Test location
Target object
Equipment
Parameter
Truck dock
Item level (box), skid
900 MHz
Storage
Item level (box), skid, forklift
900 MHz
Work station
Item level (box), ULD, forklift
Airside gate
ULD, tug car
900 MHz, 433 MHz, 2.45 GHz 900 MHz, 433 MHz, 2.45 GHz
Reading distance directivity of antenna, reading reliability Reading distance, directivity of antenna, speed of tug car, reading reliability Reading distance, directivity of antenna, reading reliability Speed of tug car, reading reliability
Automatic Identification and Data Capture (RFID, barcode) based data. Manual input data by human resource. Synchronized data: data which was synchronized with relevant data in the application system (synchronization is preprocessed). In Table 7, descriptions of each data are as follows: Business location identification data: a process location where an event is occurred. Location identification data: a physical location (spatial) where a cargo is located when an event is occurred. ULD identification data: a unique identification data for a ULD which is operated in the given event. SKID identification data: a unique identification data for a SKID cargo which is operated in the given event. MAWB identification data: a master airway bill identification data required to synchronize document information and physical cargo information. Time data: a timestamp history for each event. Table 8 shows data model developed for our cargo monitoring system which is based on the EPC network [20].
4.2. Event and design of EPC based data model 4.3. Implementation of RFID based cargo monitoring system In order to monitor each process with RFID system, firstly we define ‘‘event” for a specific process. In our research, data for event is mostly collected by RFID in real-time mode (Table 6). In monitoring a cargo, we classified data considering data collection mode (Table 7). Details are as follows:
Trappey et al. [32] introduced an agent-based collaborative mold production (ACMP) system which supports the collaborative and autonomous mold manufacturing out sourcing processes. ACMP provided autonomous features to handle three major tasks
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Table 6 Process, event and data. Process
Event
Data (nominal data for defining event)
Arrival (receiving and check)
Arrival
Storage
Storage
Build-up
Build-up
ETV-in (loading)
ETV-in (loading)
Airside
ETV-out
Table 7 Classification of required data type. AIDC data (RFID)
Business location identification data Location identification data
ULD identification data SKID identification data MAWB identification data Time data
Business location identification data. MAWB identification data. SKID identification data. Time data. Business location identification data. Location (specific storage number in storage area) identification data. MAWB identification data. SKID identification data. Time data. Business location identification data. Location (specific workstation number in workstation area) identification data. ULD identification data. MAWB identification data. SKID identification data. Time data. Business location identification data. Location (specific rack location in ETV area) identification data. ULD identification data. MAWB identification data. SKID identification data. Time data. Business location identification data. ULD identification data. MAWB identification data. SKID identification data. Time data.
Table 8 EPC network based data model for cargo monitoring.
Required data
Input data
Synchronized data
Event
Nominal data
EPC data model
Arrival
Business location identification data MAWB identification data
ReadPointID
SKID identification data Time data
Child EPCs Event time/ record time
Business location identification data SKID identification data Location identification data Time data
ReadPointID
Business location identification data ULD identification data SKID identification data Location identification data Time data
ReadPointID
Business location identification data ULD identification data Location identification data Time data
ReadPointID
Business location identification data ULD identification data Time data
ReadPointID
Rack location when loading a cargo in the ETV
MAWB No.
Storage
in outsourcing: vendor selection, task selection, and real-time outsourcing task progress tracking. In their development, RFID technology was adopted to provide a real-time tracking capability for remote collaboration, control and monitoring among outsourcing partners. They demonstrated a methodology to transform the physical process flow into information flow by taking the advantage of RFID technology. In our development, the RFID based cargo monitoring solution embraces FLEX and JAVA with Spring and Hibernate Framework. Fig. 9 show brief logical architectures of monitoring solution. As in Fig. 9, RFID system consists of reader, antenna and tag. Once reader identifies tags, reader sends a tag data to RFID middleware. For RFID code, we used SGLN for location, SGTIN for BOX, SSCC for ULD [33]. RFID middleware filters the data and send it to capturing application after converting it to ECreports data type. Capturing application reconstruct EPCIS data from the ECreports data, send the data to BPM and EPCIS according to the predefined capturing rule. After receiving EPCIS data, BPM helps cargo monitoring solution to perform next process. EPCIS stores EPCIS data and timestamp. Monitoring solution displays cargo information. Fig. 10 shows a Java Messaging Service (JMS) application, to send RFID ALE event to BPM and during the pilot, we transferred events
Buildup
ETV-in
ETVout
Parent ID
Comments
Input data (MAWB No.)
Parent ID Child EPCs Event time/ record time
Parent ID Child EPCs Child EPCs Event time/ record time
Parent ID Child EPCs
Input data (ETV rack No.)
Event time/ record time
Parent ID Event time/ record time
in real-time without failure. In the figure, the event triggered when assets are not placed as planned. Fig. 11 shows a physical architecture of cargo monitoring system installed at Incheon Airport during our pilot. In the figure
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Fig. 9. Logical architecture of cargo monitoring solution.
‘‘433” stands for 433 MHz reader, ‘‘Blackfish” stands for RFID tag printer installed, other numbers are IP addresses. Details are as follows (also see Table 9): Desktop, UMPC (Ultra Mobile PC). 900 MHz RFID stationary reader, antenna and mobile reader; tag printer. 433 MHz RFID reader and antenna. Tag: 900 MHz tag and 433 MHz tag. RFID code: SGLN, SGTIN, and SSCC. Table 9 shows types of hardware installed in each process. Fig. 12 shows implementation workflow. After receiving customer order, booking list is generated for each air flight. Each skid information has mapped with air flight number in the database. After weighing and security check, an operator reads RFID tag attached at cargo and ‘‘end” information of inspection process is stored in the monitoring system. At storage area, SGLN code is used for location identification. Once tag attached at cargo is identified, the system recognizes that the cargo is in the same area as SGLN code. At workstation area, build-up plan is generated considering ULD, SKID information and build-up list. In this area, 433 MHz system and 900 MHz system are used together. 433 MHz system reads ULD information while 900 MHz system reads SKID information during build-up process. After build-up, completed ULD is loaded to Transfer Vehicle (TV), transferred to ETV by TV. At ETV entrance, RFID system in front of ETV gate identified ULD tag, and then the system makes decision for the ULD location in the ETV rack. At airside gate, RFID system at gate identifies when some ULD is moving out and sends the information to the monitoring system. Fig. 13 shows database diagram for cargo monitoring solution. For implementation, Oracle 10 g database was used in this application.
Air-cargo monitoring solution application (i.e. presentation layer application) consists of real-time cargo information (e.g. booking list application, inspection application, build planning application, build list application etc.), dash board application, asset management application and 3D cargo track and trace application. Fig. 14 shows screen shots of build planning application and 3D cargo track and trace application. 5. Conclusion In this paper, we introduced a RFID system based cargo monitoring system. We have presented a result of RF environment study for a cargo and an EPC network based cargo monitoring system we developed. From our RF environment study, it is considered that careful study on operational environment should be preceded before individual implementation. Even though the development is still ongoing, during our pilot, one of our partners (airline companies in Korea) found potential benefits of RFID based cargo monitoring solution as follows: Increasing visibility in cargo: capability to find location of a specific cargo. Capability to expedite late cargo, visualization effect of cargo, real-time update of cargo information. In the past, it was impossible to find the location of missing ULD. After applying RFID, by using the last-known location of a missing ULD together with process routing, the airlines have reduced the search time drastically. Cost saving related to operation of air-cargo process: elimination of manual data entry and manual error. By applying RFID, the airlines expect to remove manual input processes. Cost saving related to asset management: physical ULD counting, ULD write-off reduction, reduction in ULD carrying cost from exact identification of ULD quantity, ULD lifecycle management.
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Fig. 10. Example JMS logic for to send ALE to BPM.
Fig. 11. Physical architecture of cargo monitoring system.
Y.S. Chang et al. / Advanced Engineering Informatics 25 (2011) 41–52 Table 9 Hardware used for implementation. Process
Tracking level
Frequency
Type
Inspection Storage Workstation
SKID SKID SKID ULD ULD ULD
900 MHz 900 MHz 900MHz 433 MHz 433 MHz 433 MHz
Stationary and mobile Mobile Stationary
ETV entrance Airside gate
Stationary Stationary
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With the specific installation method developed during this project, the companies expect to improve their capability on asset management. As pointed previously, there are a few researches in air-cargo business, most of them had focused on the simple track and trace of goods, the reading accuracy test, but did not address the radio environment of air-cargo terminal and did not show pictures of global data sharing networks. In this paper, we explained RFID
Fig. 12. Implementation workflow considering system architecture and cargo process.
Fig. 13. Data base diagram for pilot implementation.
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Fig. 14. Build-up planning and 3D ULD monitoring.
based air-cargo monitoring system with real world pilot implementation. We believe that our research will bring a guideline for RFID adoption in the air-cargo operation which requires harsh and robust operating environments. Acknowledgements The authors thank to the anonymous reviewers for valuable comments. This research was supported by a Grant (36-2007-CAirport) from Development for the Intelligent Airport System Program funded by Ministry of Land, Transport and Maritime Affairs of Korean government. References [1] J. Collins, Delta Plans US-wide RFID System, RFID Journal. Available from:
[14] Y.S. Chang, U.Y. Park, C.A. Kwon, J.J. Lee, S.W. Lee, V. Kumar, Developing test methods for RFID equipments for air cargo terminal operations, CD ROM, in: Proceedings of the International Conference on Logistics and Supply Chain Management, Hong Kong, January 4–7, 2006. [15] B. Bacheldor, Thai Airport Tests RFID to Track Cargo Streamline Customs, RFID Journal. Available from: