An Implementation of Wireless Sensor Network for Security System using Bluetooth.doc

编号： 毕业设计(论文)外文翻译（原文）学 院： 机电工程学院 专 业： 电气工程及其自动化 学生姓名： 梁峰茂 学 号： 0800120120 指导教师单位： 机电工程学院 姓 名： 王斌 职 称： 讲师 2012 年 5 月 20 日桂林电子科技大学毕业设计（论文）原文用纸 第 31 页 共31页IEEE Transactions on Consumer Electronics, Vol. 50, No. 1, FEBRUARY 2004Contributed PaperManuscript received January 11, 2004 0098 3063/04/$20.00 2004 IEEE236An Implementation of Wireless Sensor Networkfor Security System using BluetoothSoo-Hwan Choi, Byung-Kug Kim, Jinwoo Park, Chul-Hee Kang, Doo-Seop EomAbstractIn recent years, the advances in wireless communication and electronics have accelerated to develop many wireless network solutions to replace existing wired networks. A wireless network solution can support mobility and flexibility of nodes in a network. Especially in sensor networks, it has many advantages to replace cables with wireless logical links. On the other hand, Bluetooth is generally considered as a promising short-range wireless technology because of its inexpensive cost, low power and small size, and thus Bluetooth has been gaining increasing interest from various industries. For the above reasons, we adopt Bluetooth technology for a wireless sensor network which is designed for security systems. Since Bluetooth will continue to be a feature found in many devices, it is worthwhile to investigate its use in wireless sensor networks. In this paper, we describe a Bluetooth wireless sensor network for security systems, which includes the implementation issues about system architecture, power management, selfconfiguration of network, and routing. We think that the methods or algorithms described in this paper can be easily applied to other embedded Bluetooth applications for wireless networks.Index Terms wireless, sensor network, Bluetooth,security systemI. INTRODUCTIONBluetooth uses short-range radio links, intended to replace the cables connecting portable and/or fixed electronic devices 1. It is envisaged that it will allow for the replacement of many propriety cables that connect one device to another with one universal radio link. Its key features are robustness, low complexity, low power and low cost. Designed to operate in noisy frequency environments, the Bluetooth radio uses a fast acknowledgement and frequency hopping scheme to make the link robust. Bluetooth radio modules operate in the unlicensed ISM (Industrial, Scientific and Medical) frequency band at 2.4GHz, and avoid interference from other signals by hopping to a new frequency after transmitting or receiving a packet. Compared with other systems in the same frequency band, the Bluetooth radio hops faster and uses shorter packets. In this paper, we introduce a system implementation of a wireless sensor network for security systems using Bluetooth.On the other hand, a sensor network is composed of a large number of sensor nodes that are densely deployed either inside the phenomenon or very close to it 2. The position of sensor nodes need not be engineered or predetermined. This allows random deployment in inaccessible terrains or disaster relief operation. But in the existing wired security system, because all sensor nodes have to be connected by wires, whenever they are set up, cables must link the sensor nodes to a local security system. If cables link to sensor nodes, it will not only cost a great deal but also be hard to maintain and mend. Moreover it is hard to change a position of a sensor node, and if there is an accident such as a disaster that destroys the wired network, sensor nodes corresponding to that portion are divested of their function. Consequently if sensor nodes are linked to a local security system using short range wireless communication technology, a restriction of a position to set up sensor nodes disappears and it has more advantages to maintain, mend and recover than the existing wired network 3, 4. Representative short range wireless communication technologies are Bluetooth, IEEE802.11 WLAN (Wireless Local Area Networking), HomeRF and IrDA. The reason that Bluetooth, especially, comes to fore is as follows.Bluetooth modules can be adapted at low price according to the law of mass production and used all over the world because of working at 2.4GHz ISM frequency band 5. Moreover Bluetooth has the ability to form personal area networks or Piconets without manual configuration, which means sensor nodes with Bluetooth modules can be established only by being placed. And it also has an inherent power management state to insure a low-power operation. The power of a sensor node operated with a battery can beefficiently saved 6.To overcome the restrictions of wired sensor networks, we propose to use Bluetooth technology for a wireless sensor network for security systems. The proposed network consists of sensor nodes, relay nodes and a control node. All nodes communicate with each other with the Bluetooth module. Sensor and relay nodes detect certain events (e.g. someone enters the security area without permission) and report the events to the control node. Then, the control node reports the information received from the sensor or relay nodes to the local security control system and replies to the corresponding node with an ACK message. If sensor nodes are not able to directly reach the control node, the relay nodes placed between them can relay the message from the sensor node to the control node. All nodes transmit and receive packets via a Bluetooth module that is embedded in them. In this paper, we introduce the implementation issues related to the proposed network, which includes system architecture, power management, self-configuration of network and routing. Since the network configuration of Bluetooth is based on the Piconets where each Piconet has one master and up to 7 slaves. So, the tree topology can be considered as a natural and appropriate choice for the networks using Bluetooth. Thus the proposed system adopts the tree topology for selfconfiguration and routing. The tree topology has many advantages in that it is easy to find a multi-hop route to the control unit or a specific node, to maintain network, and to control medium access.This paper is organized as follows. In Section 2, a general description of Bluetooth is given. In Section 3, the overall system architecture is described. The developed systems description and its performance evaluation are in Section 4. Finally, we conclude this paper in Section 5.II. THE OVERVIEW OF THE BLUETOOTH SYSTEMA hardware architecture overview of Bluetooth is outlined in Figure 1. It consists of an analog part the Bluetooth radio, and a digital part the Bluetooth Host Controller.Fig. 1. Bluetooth hardware architecture overviewThe Bluetooth radio consists of a transceiver and an antenna, and operates in the ISM band of 2.4GHz. Information is modulated using GFSK (Gaussian Frequency Shift Keying) at a rate of 1M symbols/second and transmitted in one of 79 1MHz channels. Signals are frequency hopped over the 79 channels at a rate of 1600 hops per second.The Host Controller consists of three parts; the Link Controller (LC), a CPU core, and an external interface part. Thelink controller consists of hardware and software parts that perform the Bluetooth Baseband processing and physical layer protocols such as ARQ (Automatic Repeat request) and FEC (Forward Error Correction). The CPU core executes the Link Manager (LM) software. It allows the Bluetooth module to handle inquiries and filters Page requests without involving the host device. The external interfaces provide the communication channel between the host and the Host Controller, including RS232 and USB (Universal Serial Bus) interfaces.Fig. 2. (a) Piconets with a single slave operation, (b) a multi-slave operation(c) and a scatternet operation.The Bluetooth system provides a point-to-point connection (only two Bluetooth units involved), or a point-to-multipoint connection, see Figure 2. In the point-to-multipoint connection, the channel is shared among several Bluetooth units. Two or more units sharing the same channel form a piconet. One Bluetooth unit acts as the master of the piconet, whereas the other unit(s) acts as slave(s). Up to 7 slaves can be active in the piconet. Multiple piconets with overlapping coverage areas form a scatternet. Each piconet can only have a single master. However, slaves can participate in different piconets on a timedivision multiplex basis. Each piconet has its own hopping channel.Two link types have been defined between a master andslave(s): Synchronous Connection-Oriented (SCO) link Asynchronous Connection-Less (ACL) linkThe SCO link is a point-to-point link between a master and a single slave in the Piconet. The ACL link is a point-tomultipoint link between the master and all the slaves participating on the Piconet. The communication between two Bluetooth devices is via packets. Bluetooth packets are comprised of three major portions, the access code, the header, and the payload, as shown in Fig. 3. The access code is used in synchronization and to identify packet channels. If the header field follows, the access code is 72 bits long, otherwise it is 68 bits long. The header identifies the sender of the packet and the type of packet being sent. The encoded header field occupies 54 bits. The payload of the packet contains user information and occupies one, three, or five time slots. Each time slot is 625s long.Fig. 3. Bluetooth packet formatThe Host Controller Interface (HCI) driver on the host side provides a uniform interface method of accessing the Bluetooth hardware capabilities. The HCI firmware on the Host controller side implements the HCI commands for the Bluetooth hardware by accessing link manager commands, hardware status registers, control registers, and event registers. Figure 4 provides an overview of the Host Controller interface concept.Fig 4. The Host Controller interface software layersIII. THE PROPOSED SYSTEM ARCHITECTUREIn this section, we give a full explanation about the proposed system. To help understand the system operation, we first introduce an overall working flow of the system and then explain the initialization procedure for network configuration and routing. Finally, we introduce the operation of each node in the system in more detail.A. System OverviewThe purpose of the proposed system is for detecting an invasion in a building that needs security service, and it consists of lots of sensor and relay nodes and a control node. Figure 5 illustrates the communication environment of the system. Sensor nodes are placed in each room in the building and logically connected to the control node, which is located at a certain place in the building and can be reached via relay nodes. Sensor node Relay node Control nodeFig. 5. Communication environmentThe control node is connected to the local security control system that is implemented using a PC. An operator in the building can monitor the whole system in real time through the local security control system. Namely, it is possible for him to check the state of a certain room and the operating status of a specific sensor or relay node in the system at any time whenever he wants. Meanwhile, the local security control system is connected to a central security control system via the Internet. In this paper, we do not deal with this issue.Sensor and relay nodes detect certain events and report it to the control node. Then the control node reports the event received from the sensor or relay node to the local security control system and replies to the corresponding node with an ACK packet. The node which had sent an event packet must receive an ACK packet from the control node to verify that the event packet was delivered to the control node. If sensor nodes are not able to directly reach the control node, the relay nodes placed between them relay the message from the sensor node to the control node. That is, if a sensor node is not able to inquire the control node (i.e., the control node is located outside the range of a sensor node), relay nodes placed between them form a route from the sensor node to the control node. All nodes transmit and receive packets via Bluetooth modules embedded in them.When a phenomenon is detected by a sensor or relay node, such an event is translated to a predefined value corresponding to that event, and then it is transmitted in the form of an event packet to the control node via the radio link. In this paper, we assume that sensor and relay nodes have onoff switches to emulate certain events, e.g., the motion detectors in those nodes detect a movement, for convenience.Since sensor and relay nodes must be operated without any external power supply for a long time, it is important to reduce power consumption. They have a power management mode to insure their power supplied by battery can be efficiently saved. The control node does not have a power management mode because its power can be supplied through the outer power line.The application programs for the nodes directly drive their Bluetooth module through the HCI interface without the help of the upper layer protocols such as L2CAP and RFCOMM. Instead, the basic functions of the eliminated upper layer protocols are implemented in the application program. By doing this, we can significantly reduce the total program code size and the program can be operated in a single process. We can thus extremely use the limited processing power and memory of the ARM CPU core in the Bluetooth Host Controller. It is because if there are multiple processes operated in CPU then the resources such as CPU processing power and memory are more required for the context switching.B. Network ConfigurationIt is common that sensor and relay nodes are not able to directly communicate with the control node. Thus network configuration is required for routing packets over the multihop route and maintenance of nodes, but which is performed not by a manual setting but by a self-configuration. As previously explained in Section 1, the tree topology as shown in Fig. 7 is used for network configuration in the proposed system. The tree topology has many advantages in that it is easy to find a multi-hop route to the control node or a specific node, to maintain network structure, and to control medium access and transmission timing.On the other hand, each Bluetooth device is allocated a unique 48-bit Bluetooth device address (BD_ADDR). This address is derived from the IEEE802 standard. With this address, Bluetooth transceivers can communicate with each other in only one hop range. In addition to the BD_ADDR, we define a logical address such as IP address for finding multihop routes easily in networks with tree topology.For network configuration, each node first acquires the local information such as its addresses, which is required for set up, and then finds its neighbors through the inquiry procedure defined in the Bluetooth specification. Finally it communicates with its neighbors to exchange the information which is necessary for network configuration. The flow for the network configuration as shown in Fig. 6 is performed by each node in a distributed manner. The procedure for the network configuration is summarized as follows1) Read memory in order to acquire address and other information which are required for set up when the power is turned on.2) Perform an inquiry procedure to find adjacent nodes and save respondent nodes information which is necessary for connection in an address table (e.g., BD_ADDR, clock information, etc.). The inquiry procedure can be continued until finding N adjacent nodes or for a fixed period.3) Page the inquired nodes one by one for connection and exchange a packet including logical address and other information necessary for network configuration.4) Compare its own logical address with the received logical address to determine the logical relationship between them, which includes parent, child node or none, and then save the result at the address table.5) Sensor and relay nodes enter a power management mode and the control node enters a standby mode to wait for an event or paging.Fig. 6. Network configuration flowAfter the network configuration, an inquiry procedure is periodically performed, considering that some nodes disappear or newly appear in operating time. If there is no inquiry response from a node which had already been inquired before, it is considered that the node moved out from the range of theinquiring node or malfunctions. Thus the inquiring node performs a series of three inquiries and if there is no response, finally removes the information of the node from its memory. If a node which had not been inquired before is newly inquired, the inquiring node makes a new record and pages the new node to exchange a packet which has logical address and other necessary information. The period for inquiring is normally set to 5 minutes. However, since each relay or sensor node must be connected to its parent node to operate normally, if its parent node is not inquired, such nodes periodically inquire every 40 seconds until their parent nodes are inquired.In the case of a sensor node, once it finds a parent node, it doesnt inquire until it loses its parent node. But, it does not matter because sensor nodes do not relay the packets from the other nodes. It also means that sensor nodes do not perform the inquiry procedure periodically. The sensor node needs to perform power management, so it doesnt inquire its parent node until its parent node disappears. If the sensor node inquires periodically, it consumes more power.After all nodes go through th