A Wearable Computing Environment For The Security Of A Large-Scale Factory Jiung-yao Huang1 and Chung-Hsien Tsai2 1 2
National Taipei University, Dept. of CSIE, E-mail:
[email protected] National Central University, Dept. of CSIE, E-mail:
[email protected]
Abstract. This paper studies the issue of using the wearable computer as a remote sensing device of a large-scale factory. The infrastructure of ubiquitous security environment to realize the remote sensing capability for the security guard is presented in this paper. This paper also scheme out a wearable computing scenario for the security guard under such a ubiquitous security environment. That is, through the help of the wearable computer, the security guard can remotely sensing the security status of each building when he is patrolling a large-scale factory. To achieve a seamless remote sensing environment, we use the wireless AP (Access Point) as the relay between static sensor networks installed inside each building and the mobile sensing device worn on the security guard. The AP enable the wearable computer to seamless receive security status of each building and upload the wearer status to the security control center at the same time. Furthermore, this research adopts the technology of embedded Linux to design a middleware for the wearable computer. The proposed architecture of the wearable computer is scalable, flexible and modular for the mobile computing system. Finally, this paper elaborates a seamless connection approach for the wearable computer within a ubiquitous security environment. Keywords: Wearable computer, Mobile Computing, Remote sensing, Ubiquitous security environment
1
Introduction
Pervasive Computing has already become the computing trend of the next century and, hence, the research of wearable computer has attracted significant attention. The famous propaganda slogan of Nokia Company - Connecting People (science and technology come from the human nature all the time) proclaim the interaction among the scientific and technological products and the people. Due to the immature development of the scientific and technological products in the past, there are passive operational relations between the computer and people. With the progress of relevant technology in the semiconductor, the development trend of computer becomes smaller, cheaper and more quickly, even more intelligent[1]. Steve Mann[2] considered the mobile computing as:” it belongs to the personal space, controlled by the users, and operated interdynamic continuation at the same time (constancy)”. In other words, it
is “always on and always accessible". The computer that supports this characteristic is called "wearable computer".
2
Related Works
The major technologies to achieve a ubiquitous security environment are the sensor network, the seamless communication, and the wearable computing. This section will briefly outline previous researches on these issues. Recent researches on Seamless network[3][4] proposed a “fast handoff” and a “smooth handoff” model to accommodate mobility across heterogeneous networks that uses standard protocol (i.e. IP). These researches attempt to seamlessly and automatically handoff the user information from one access point to another. They also minimize handoff-related delays and packet loss, so that the network session can be persistence among different access points. An important application of the seamless communication technology is the sensor network environment. Ardizzone et al.[5] successfully deployed large amount of powerful wireless sensor networks and use the standard IEEE 802.11 (Wi-Fi) radio channel to monitor transient events in physical environments. Ryan et al. [6] uses high level control to cooperate several small UAVs(unmanned aerial vehicles) with sensors to form a mobile sensor network for remote sensing. Their research goal is to execute tasks such as obtaining sensory measurement, border patrol, search and rescue, surveillance, communications relaying, and mapping of hostile territory over a large area. Akyildiz and Kasimoglu [7] proposed a Wireless Sensor and Actor Networks (WSANs) to achieve seamless communication among distributed static sensor networks. WSANs is a group of sensors and actors linked by wireless medium to perform distributed sensing and actuation tasks. In such a network, sensors gather information about the physical world, while actors take decisions and then perform appropriate actions upon the environment, which allows a user to effectively sense and act at a distance. The wearable computing is the last ingredient of a ubiquitous security environment. As pointed out in[8], a wearable computer should possess the following features: "Portable while operational", "Hands-free use", Sensors, "Proactive", and “Always on, always running". Among these features, “Portable while operational” is the essential distinction between the wearable computer and the legacy computer, such as desktop computer and the laptop. The wearable computer can be used while the wearer is on the move. Hands-free requirement is emphasize on avoid holding any input device while operation. However, some wearable computing applications may use special input devices that tie on user’s hand, such as chording-keyboards, dials, and joysticks. For example, Australian Institute of Marine Science (AIMS) designed a so called WetPC[9] underwater computer for research divers to perform underwater activities. To facilitate the diver to manipulate the WetPC, a five buttons KordPad is specially designed for it. The wearable computer may equip with sensors to perceive surrounding information for the user. For example, DeVaul et al.[10] designed MIThril 2003 wearable computing research platform which equipped wide range of body sensors, such as pulse oximetry, respiration, blood pressure, EEG, blood sugar, humidity, and CO2 sensors etc., to monitor wearer’s physiological status for
biomedical or social network research applications. In 1998, IBM Japan announced a wristwatch computer, called Linux Watch[11], which looks like an ordinary watch but runs Linux, features X11 graphics, and offers Bluetooth wireless connectivity. Linux Watch also embodies accelerometer and vibrator sensors to detect wearer’s motion. Bauer et al. present a collaborative wearable system, called NETMAN [12], with remote sensing capability for network maintenance. Their work has proven that remote sensing capability can significantly improve communication and cooperation of highly mobile computer technicians. The work presented in this paper is similar to NETMAN[13]. However, we go a step further by adapting the concept of WSANs[7] to design the ubiquitous security environment for a large-scale factory. This research use wireless access points to play the role of sensor nodes and the wearable computer is model as the actor of such environment. In the following sections, the feasibility of using the wearable computing technique for the security of a large-scale factory is discussed first. The architecture of the digital security guard system is then presented. Finally, the seamless communication technique to build a Remote Sensing security environment is elaborated last.
3
The Mobile Surveillance Environment
The security of a large-scale factory is an important task to ensure the safety of the employees and goods. With the increasing complexity of the security scenario in the recent years, the security industry has moved towards professionalism nowadays. A large-scale factory always has blind spots of security no matter how many surveillant cameras are installed inside the factory. The security guard always is the ultimate defense of security. Due to various uncertain conditions on the incident or crime scene, the security guard may himself trap into a dangerous situation when he arrive the scene. When that happens, his professional skill and reaction capability maybe are the only solution for his own safety. If the security guard can acquire a live coverage of the scene before his arrival, he then can has enough time to properly protect himself from any possible injury. As illustrated in Figure 2, the traditional security system only allows the Security-Service Center to collect security messages from the installed sensors on the scene. When an event occur, the guarder in the Security Service center is then responsible for report received messages to the security guard who is rushing to the scene. This architecture may cause serious information delay which, in turn, may consequently put the security guard into a hazard scenario due to the insufficient information.
Fig. 1. Information flow of the traditional security system
To solve this problem, this paper proposes a mobile digital surveillance system to provide a pervasive security environment. The proposed architecture integrates installed intelligent security sensors, wireless and wired networks inside the factory, the wearable computer for the security guard, and the Security-Service Center to reduce limitations of the traditional security system. As depicted in Figure 3, with the help of the wireless communication capability, the security guard can acquire live sensors data before he arrive the event scene.
Fig. 2. Information flow of the mobile surveillance system
The proposed system enables the security guard to continuously receive live messages of various sensors from his wearable computer while he is patrolling the factory. Since the security guard always receive live coverage of factory’s status, the security guard can have proper response immediately when an event occurred. Furthermore, since the factory is covered with wireless access points, the wearable computer can send the status of the security guard back to the Security-service center in real-time through these wireless/wired networks. By this way, the information delay between
the Security-Service Center and the security guard is significantly reduced. In the traditional system, the Security-Service Center and the security guard often have misleading cognition on the event scene due to vocal misinterpretation and insufficient live information. The proposed architecture present in the following sections can solve this problem by providing a pervasive security environment.
4
Digital Security System Architecture
This paper presents architecture of information live exchange between the security guard and the Security-Service Center so that the security guard can response to any event in the factory promptly and safely. It enables the security guard and the Security-Service Center always online while the security guard is patrolling. Meanwhile, the Security-Service Center can aware the location of the security guard at all time. The proposed digital security guard system for a large-scale factor is as illustrated in Figure. 4.
Fig. 3. Scenario of the pervasive security environment
The digital security system mainly composed of three parts: Building-Safety Unit (BSU), Security Personnel Unit (SPU) and Security-Service Center (SSC). Among them, SPU is a wearable computer which equips active communication devices to interact with SSC and BSU in real-time. The SPU constantly transmit the location and status information of the security guard to SSC. The BSU of each building will continuously collect data from various sensors installed inside the building. Meanwhile, BSU will periodically detect if a SPU is entering the coverage of wireless signal of its access point installed outside the building. As the security guard wearing a SPU approaching a building, his SPU will actively communicate with BSU of that building to obtain detailed security information of that
building. At the same time, SPU will also convey the status information of security guard to the SSC through BSU of that building. Hence, BSU of a building play two roles in this scenario. It will transmit the collected security sensors messages of that building to SSC in the background at all time. When it detect a SPU is within the range of its wireless communication, it not only download the security sensors information to SPU but also upload the status information from SPU. The uploaded data is then forward to SSC through wired network between BSU and SSC. That is, BSU act as a relay station between SPU and SSC. Hence, the information flow among SPU, BSU, and SSC can be depicted in Figure 5.
Fig. 4. The message flow of the pervasive security environment
As the research of the pervasive computing has grown vigorously in the recent years, the required sensor techniques and context awareness methodology has already studied[13][14] extensively. Hence, the reset of the paper only focus on the mobile computing of the outdoor environment and present a seamless communication algorithm to provide a pervasive security environment in a large-scale factory.
5
Seamless communication network
As illustrated in Figure 4, when the security guard wearing a SPU enters the signal coverage of the Access Point of a building, a message channel will be automatically established among SPU, the Access Point, and BSU. The proposed pervasive security networking environment is based on WLAN (i.e. 802.11a/b/g) [15]. In addition, based upon IEEE 802.11b specification, we define the linking distance between SPU and the Access Point is within 50 meters of signal limitation. In order to realize the Remote Sensing capability for SPU and SSC, a seamless communication environment is the essential requirement. To achieve this need, both SPU and BSU are designed as multi-thread systems. Furthermore, SPU contains two connection threads, which are Linking Thread and Data Thread, as depicted in Figure
6 and Figure 7. The algorithms for the Linking thread and Data Thread are outlined as follows.
Fig. 5. Linking thread
1.
(1)
(2)
(3)
Linking Thread: Its functions include detect a potential link, establish a link, and perform handover protocol between SPU and the Access Point, as discussed follows. Link detection phase: This phase will determine which network domain it can carry out the linking? By detecting and examining the signal strength of a access point, SPU can confirm if it is within a signal coverage of a wireless network. When a linking signal is detected, the linking protocol is then executed. If the signal strength is lower than a predefined strength, it will give up that link. Otherwise, SPU will check whether the received signals come from existing linked access point or not? If not, further check the received signal is stronger than existing one? Follow this procedure, SPU can detect if the security guard is walking away the building of an existing link and moving close to a wireless signal of another building. If SPU detects and approaches another access point, it then begins to establish a new connection link. Link connection phase: When SPU enters the coverage of an access point, this access point will identify its SSID authentication first. If SPU is an authorized user, this access point will begin to set up a communication channel with SPU. Handover phase: The foundation of a pervasive security environment is a persistent connection between WLAN and the wearable computer. To achieve this fundamental requirement, we adopt the handover/handoff adaptive technology from CDMA to realize signal handshaking. The handover/handoff mechanism is the key of whether SPU can obtain event alarms in real time. The communication channel switching procedure is divided into two cases: roaming and handover/handoff. Among them, roaming procedure has already defined by IAPP (Inter Access Point Protocol) between a client and the access point. This mechanism allows a
client to keep new and old connections simultaneously while switching between two access points. It also maintains the best linking status before switching to ensure not influence client’s transmission quality. That is, client can freely move in a large-scale factory within coverage of different access points. While SPU lost connection to an old access point and establish new connection with another access point, the soft handover or hard handover mechanism is required to accomplish the task. The hard handover approach belongs to BreakBefore-Make and its connection feature is easier to be cut off. On the other hand, the soft handover protocol switch communication links under the same frequency, so it can set up a new connection before cut off previous one. Hence, soft handover approach consumes less power but is difficultly to cut off. However, Lin[16] has shown that the performance of the soft handover is better than the hard handover. Rajiv et al.[17] gave the following suggestions to pinpoint delay and improve handover performance: i. Speed up RA (Router Advertisement). ii. Increase client-base Caching of RA. iii. Use soft handover. Our research adopts soft handover technique to guarantee a persistent communication for SPU to send/receive messages while patrolling among buildings. 2. Data Thread: It is responsible for data exchange between SPU and BSU as shown in Figure. 7. The BSU server has a polling mechanism which provides a robust link with SPU to upload and download status data and security messages, respectively. The procedure of the Data Thread can be classified into three phases, which are polling mechanism, Download data, and Upload data.
Fig. 6. Data thread
(1)
(2)
Polling mechanism: The BSU provides a polling procedure to monitors and communicates its access point. When a SPU is detected and connected, it then tries to assist SPU to login the server. Download Data:
After SPU login BSU server, server downloads three types of data to SPU. The first one is the detailed security messages of the building. The second type is other buildings’ brief security information. Finally, the last one is the control command from SSC. By this way, the security guard can obtain the security status of all buildings within a factory while keep contact with SSC at the same time. In addition, the study of this research combine the specification of IEEE 802.11 MAC (Medium Access Control) PCF (Point Coordination Function) with polling mechanism to provide Real-time Multimedia Downlink[18] capability. The effectiveness of this approach had already proved by Wu [19]. In addition, Guo[20] proposed Connection Manager (CM) and Virtual Connectivity Mechanism to offer Quality of Service (QOS) for End-to-End Operations, connection maintenance, and Subscription/Notification service. The research by F. Cali et al.[21] pointed out that the available bandwidth is B0 -λ L where B0 is total bandwidth and L is a mean frame size. (3) Upload Data: SPU upload the status data of the security guard to BSU, which then forward received data to SSC. This phase enable SSC to fully aware the status of the security guard. In summary, SPU is a mobile computing device on such pervasive security environment. The seamless communication network enable SPU to actively “talk” to BSUs of each building for its security information while the security guard is patrolling the factory. From this perspective, SPU becomes a seamless communication device in this pervasive environment.
6
CONCULSION
The research goal of this paper is to design a pervasive security environment of a large-scale factory. In addition, this paper solves the seamless communication problem of such a pervasive security environment. The proposed system structure integrates the advantage of WLAN, wired network, and the polling mechanism, to achieve a Pervasive, Proactive, Mobility, and Wearable security environment. This research creates a human-centric wearable computing environment to assist user to deal with information that are related to the environment. The presented architecture can significantly improve working efficiency as well as safety of the security guard. Finally, the paper provides a complete solution to integrate the wearable computer into a large-scale factory to achieve the goal of “any time” and “anywhere” complete secure environment.
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