Wireless sensor network design of prison security system

Introduction

Prison for its security system design with high-security, stability, and real-time performance requirements.

At present, the prison system in video surveillance systems, alarm systems, access control systems are based on wire communication, this makes some inconvenient wiring area became a security blind spot monitoring of, in addition, static monitoring area for criminals to exploit. To prevent the prisoners fight, suicide, suicide, prison break, assaulting police officers and other criminal activities, timely and accurate control and access to the prison violence site, prison break behavior information, build civil defense and security of the Trinity of proof, the security system, a wireless sensor network of prison security system design. Wireless instead of cable can bring many benefits, such as reducing deployment complexity, reduce maintenance costs and increase flexibility, especially those that cannot be routed or inconvenient wiring area. As Siemens building technologies Group Chief technology expert Helmut Macht said: "wireless communication innovations to more and more wired communications will be replaced. However, due to the particularities of the internal environment of the prison, in jail internal adoption of wireless technology will face many problems. First of all, the use of wireless technology will face multipath transmission interference, transmission and reflection, and other obstructions, these issues affect wireless network reliability and scalability, the impact of broadband communication data throughput; Secondly, because the vast majority of existing monitoring systems are based on the design of the cable network, so that its original application and agreement to senior level in a wireless network, application must be modified accordingly; in addition, the wireless technology to prison security systems are widely used, the equipment cost is also an important factor, wireless communication module must be suitable for monitoring system, low-cost requirements. This study is based on wireless sensor network design of prison security system, and not simply replace wired with wireless, but existing prison wired security system based on the retention of the original data transfer large video monitoring, thresholds, etc in wired, join the static temperature vibration-sensitive wireless sensor networks and dynamic real-time positioning, wireless sensor network to more sophisticated security systems, eliminating the blind spot monitoring to enable the functionality of the various subsystems.

1 prison security system wireless network technology

Wireless sensor network is a group of Ad Hoc sensor to modes of wired or wireless network, which aims to collaborate in perception, acquisition and processing sensor network covered by the geographical information in the perception of objects, and passed to the observer.

This kind of sensor network set the sensor technology, embedded computer technology and wireless communication technologies, collaboration and awareness, monitoring and collecting various climate perceive objects through the collaborative information processing, access to accurate information perceived objects, and then, through Ad Hoc manner to the need of users. For sensor network sensors and general concepts of the sensor, in addition to being able to sense the change of the measured parameters and output the appropriate changes in the information, but also with remote communication feature, you must be an intelligent sensors. In addition, to complete the communication function, in addition to the sensitive element, you must have the power, embedded microprocessors, storage, data transfer and communication components, etc. Figure 1 typical of sensor network map that includes sensor nodes (sensor), observing nodes (sink) and base station, etc.

　　

　　

In sensor networks, nodes through aircraft dispenser, artificial arrangement, a large number of deployment objects in perception or near the inside.

These nodes through self-organizing manner constitutes wireless networks to collaborate perception, collection and treatment network coverage area-specific information that can be achieved on any location information at any time of the acquisition, processing and analysis. This form of the self-organizing networks, through the multihop relay data back into your sink node (interim node), finally, with a link to the entire area with sink of data transfer to the remote control center for centralized processing.

Wireless sensor network basic element is a node in a different application, the sensor node design also vary, but their basic structure is the same.

Node of typical hardware structure as shown in Figure 2, mainly includes the following modules: a sensor units (at the sensor and the analog-digital conversion function modules), processing unit (embedded system components, including the microprocessor, memory, signal conditioning circuits, etc.), communication unit (by wireless RF modules), as well as the power part. In addition, you can select other functional units including: positioning systems, mobile systems as well as power from the power supply system, etc.

　　

　　

2 on-site execution layer design

2.1 static monitoring system design plan

The wireless sensor network node placement in the prison room, production area, commanding heights, confinement, teaching area, clinic, etc., to achieve comprehensive coverage for prison.

Will wireless sensor network technology into prison security system, mainly because the sensor node in prison is very large, wiring project is very large, and that many of the area is not appropriate for a wired connection, if the use of wireless access, you place the sensor deployment has become very easy, you can easily increase the sensor node or change the position of the node. Through periodic or occasional changes monitoring sensor node, you eliminate the existing wired monitoring system in the blind spot monitoring, through the sensor array to the target location. And, because of the location of the monitoring node constantly changes, prisoners cannot find monitoring vulnerability to more sophisticated security systems.

2.2 dynamic real-time monitoring system design plan

By nodes to wear in the prisoner who, using positioning mechanism a real-time understanding of criminal activity.

But because of the higher number of prisoners, they only need to transmit data in two categories: the first is the scope of the activities of exceeding a specified range; the second isNode due to external force or energy depletion and failure, remote Center must detect missing nodes. Sensor node gets data can be processed locally, and then simply, aggregation and delivery to the base station (PC or PDA), the prison of the remote server and the monitoring system for each monitored target of prisoners in real time analysis, judgement by expert system real-time status of the prisoners. If you find unusual or dangerous prisoners for alarm and quickly make measures. At the same time, this system can also provide other auxiliary functions, such as location tracking of offenders. Through the sensor network on prisoners necessary vibration, location indicators, real-time monitoring, while also allowing prisoners in a range of free activities, this will help patients to maintain good mood improvement for prisoners. Since each prison room deploy appropriate sensors, so that corrections can fully grasp the rest of the prisoners. When a prisoner in the prison room or outdoor activities in prison (called out to deploy Ward sensor network), the prison guards still can locate, track, and promptly gets its vibration, location indicators parameters.

The node is of wearing in the prison guards.

Using the node configuration of vibration sensors and positioning system, can real-time monitoring prison guards work area and ensure their personal safety. On the one hand, in the event of unforeseen circumstances, such as prisoners, assaulting a police officer or the fight between prisoners, monitoring system and remote service centres to respond promptly to notify the police arrived at the scene quickly to support; on the other hand, by prison guards of location and tracking, you can master the work of prison officers, the beneficial to improve work efficiency.

3 system software and hardware design

3.1 sensor node design

Each sensor nodes include 1 or more sensor components, mote and batteries.

Sensor main vibration and temperature detection, mote responsible for those data are processed and transmitted over the network to the base station.

RF introduction nRF9E5, nRF9E5 by Norway Nordic company launched by system-level RF chip.

Its use of GFSK modulation, anti-interference; supports multipoint communication, data transfer rate up to 0.1 MB/s; has a unique Shock Burst signal emission and transmission signal carrier monitoring function, can effectively reduce the power consumption current, avoid data collisions. Internal registers provides users with a basis of a communication protocol that makes it easy for users to extend, therefore, very suitable for wireless data transmission systems design. NRF9E5 transceivers are 3 working modes: Shock Burst receive (Rx), Shock Burst sending (TX) and idle mode. NRF9E5 transceivers work by special function register TRX_CE and TX_EN decision.

Digital temperature sensors DS181320 vibration by Dallas company development of miniaturization, low-power programmable single-bus digital vibration and temperature sensor, can be directly measured temperature value converted to a digital signal output.

DS18B20 work follow stringent single-bus protocol, i.e. the first initialization, and then, send the ROM command, and finally, send the command. Initialization includes host issue a reset pulse (through the bus pulled down at least 480 μ s to implement), the host waits for the existence of the DS18B20 back to pulse. DS18B20 is detected by the reset pulse rise began to wait 15 ~ 16 μ s back, through the single bus pulled down 60 ~ 240 μ s, send realizing there pulses. DS18B20 reads and writes are sequential by reading and writing. Hence, uses the DS18B20 makes the circuit simple, improve node integration and vibration and temperature measurement accuracy.

3.2 software design

This system is a little-to-multipoint communication mode, so that the communication protocol is divided into three layers: the first layer is the physical layer, the hardware implementation by nRF9E5 module; the second layer to network layer; the third layer to the application layer.

Network layer uses the TEEN (threshold sensitive energy efficientsensor network protocol) Protocol.

This agreement in response to the type of sensor network protocol, just by observing when the variable mutation data transfer. Because the sensor node of energy is limited, and the inconvenience of supplementary, so use this agreement effectively conserve energy, extend the life of the network. In addition, the security system in a prison, only when the vibration and temperature data to produce mutations only need to transmit data, while continuing to send at a constant rate to sink node monitoring data for prison security systems is not necessary. Figure 3, Figure 4 respectively host module software flowchart and node module software flowchart.

　　

　　

　　

　　

In specific applications, TEEN defines hard, soft 2 threshold value to determine whether you need to send the monitoring data.

Hard threshold settings, when the temperature and vibration than this value, then the node sends the monitoring data to the sink node; soft threshold settings, when the vibration and temperature change range exceed this value, then send the data.

4 simulation and analysis

In order to verify the feasibility and effectiveness of the algorithm, do not take into account wind speed, wind direction, temperature, humidity, noise and other factors on positioning precision impact, assuming that sound in the air velocity is 340 m/s.

As shown in Figure 5, assuming 3 sensor node distribution area in 100 m100m.

Figure, o represents the target physical location, * location on behalf of the sensor nodes, + number represents the calculated target location.

　　

　　

Through static distribution in sensor arrays can mesh

Label positioning. After simulation validation, use the target location system calculates the target location with the actual location of the error in between can receive. When a sudden condition, in accordance with the calculation results, through employment can take swift and effective measures.

Simulation in the square 100m100m, random evenly distribute a certain number of nodes, 10, 20, ...

To 100, each node has the same communication distance 10m, where five cluster-head node. Figure 6 shows the positioning algorithm in DV-Hop randomly selected anchor node positioning error. Simulation results show: with the increase in the number of sensor node, locate the error generated. Therefore, in practice, the cost can be considered on the basis of the appropriate increased dynamic monitoring system in the number of sensor nodes.

　　

　　

5. concluding remarks

Prison security system's fundamental purpose is to bring about greater reliability, development of wireless network technology to prison security system integration bring wider space that overcomes security system integration process cable limit inconvenience nor the security system can implement many new applications.

This article gives the wireless sensor networking, wireless sensor and control network integration framework to enable wireless network technology in prison security systems are effectively applied.