Efficient Classification Scheme of Tendency of Highway Emergency

Transcription

1 Efficient Classification Scheme of Tendency of Highway Emergency Telephone System 1 Xu Jia, 2 Yuxin Liu, 3 Liwei Zhu 1,2,3 Research Institute of Highway, Ministry of Transport, Beijing, China 1,2,3 Key Laboratory of Road Safety Technology, Ministry of Transport, Beijing, China {x.jia, yx.liu, lw.zhu}@rioh.cn Abstract Highway emergency telephone system (HETS) exists at regular intervals along the sides of many highways and rapid transit lines in China, where drivers or passengers can use them to contact with a control center in case of accidents or other emergency situations. This paper proposes an efficient classification scheme and classification framework of the emergency telephone system. According to the transmission mode, the system is divided into three types: cable type, optical fiber type and wireless type, and subsequently the advantages and drawbacks of various types are compared. Finally the key issues and the future trend of development are presented. Keywords: emergency telephone system, electric cable, optical fiber, wireless, highway 1. Introduction In the twentieth century European countries first adopt HETS based on fixed communications technology equipment. Its purpose is to provide emergency rescue and dealing with special events, and the communication tools during the engineering maintenance. On the wayside of HETS terminal equipment were set 1~2 km according to a pair of field. Special sections of the highway need to increase the equipment density appropriately. When the drivers need help, they can give an alarm through the emergency system [2]. Final the staffs of the monitor center adjust the processing. HETS is one important facilities of the highway; especially the user transfer information in special circumstances and solve the problems in time. Emergency telephone is a phone specifically provided for making calls to emergency services and is most often found in a place of special danger or where it is likely that there will only be a need to make emergency calls. Emergency telephones are commonly found alongside major roads throughout the world [8-11]. In UK, orange SOS call boxes are spaced at 1 mile intervals on all motorways as well as some major "A" roads, with roadside markers indicating the nearer phone. Emergency telephones were installed at 0.25 miles intervals on all limited-access highways throughout Southern California in the United States as far back as the 1970s. On Italian motorways, emergency phones, generally colored in yellow, are found spaced at 2 kilometers intervals. The development of national HETS can be classified in the following five stages: 1) the Tianjin Tanggu port road installed "highway phone box" in Tianjin, mainly provide the maintenance personnel management service, which can be considered as the prototype of HETS in our country road; 2) With the Shanghai-Jiading, Shenyang-Dalian, JingJinTang, the capital airport highway and Guangzhou-Foshan highway open and operation in the 90s` decades, HETS was introduced from abroad, such as Alcatel, Siemens and other products from Spain, France, Singapore, etc. At the same time our country speeds up the research and development process of HETS. The typical product is the cable type HETS; 3) the technical performance and the stability of national produce HETS reached and more than imported products, and widely used in the national highway. This period cable type HETS is still mainly used; 4) At the beginning of the 21st century, our country developed the optical fiber type HETS and wireless HETS by innovation and replaced the original system gradually; 5) Traditional HETS only provides the voice business. With the technology developed, the system provides transmitting voice, data business and image business. Multi-function HETS has come out. Nowadays the fifth stage system is developed in stable. These telephones are almost always marked by a placard or sign indicating a unique serial number or identifier which allows the authorities to know exactly where the caller is, even if the caller does not International Journal of Advancements in Computing Technology(IJACT) Volume 5, Number 7,April 2013 doi: /ijact.vol5.issue

2 know, by having the caller read the short identifier from the placard over the telephone. Some phones are equipped with the equivalent of caller ID and the agent receiving the call can identify the location even if the caller cannot. The speed and size of national highway construction grow rapid and enter the ranks of the developed countries [3-7]. How to improve the management level of highway operation, establish and perfect the basic highway facilities, reinforce the traffic management and legal consciousness, improve the highway safety relief rules, improve the service consciousness and service level become more and more important. Constructing the highway of the good society image is a significant task. In highway operation, reducing traffic accidents, casualties and property losses is priority of the traffic management department and a long-term strategic task. HETS as the basic highway facilities and rescue system is necessary. Various HETS can be seen in figure 1: Figure 1. Classification of Emergency Telephone System Nowadays, most national highway set up the emergency telephone. When the drivers need for help in a traffic accident emergency rescue, the emergency system can avoid causing great losses [1]. With the widely application of the emergency telephone, a good performance and lower price highway emergency telephone is in demand of highway development. HETS can be divided into three kinds by Transmission mode: the first kind is the full length of the signal transmission cable; the second is the full length of the signal transmission optical fiber; the third is to use wireless public network of signal transmission. The three transmission ways have different features, and the specific differences in subsequent chapters are expounded. 2. Proposed classification scheme 2.1. System description The system is designed for emergency rescue when the driver meet trouble in the highway and has the following main functions [19]: accept the SOS call application, judge the call position automatically, make the telephone operator contact with the caller by the full-duplex call, proceed the call records statistically, record the phone calls and self-check error functions. HETS consists of three parts: the control center equipments, roadside extensions and transmission medium. Transmission medium can select cable, optical fiber and other mediums. The system adopted the bus, ring or star structure and the coverage is not less than 50km. Control center equipments include the mater control equipments, printers and lightning protection wiring module. The master control equipments contain the master computer, duty telephone and recording unit at least but not limited to these equipments. The system should be able to receive the roadside extension call correctly and identify the position of the call extension, show the information through the bells and vibration, call each roadside extension in time, establish and dismantle operator and call the voice pathways between extension, automatic recording for any calls with the date and time information, with the recording playback function can retrieval the call record with certain feature, when receive multiple calls, the system should be able to accept each call and carries on the line up treatment, when the system in test mode receiving normal calls should not be affected, process the call with record and statistic automatically, with automatic and manual start system measurement and abnormal alarm function, detect the system records and output classify statistics functions [18]. When emergency telephone extension call the control center unit, master computer send a call text to the computer monitoring, when emergency telephone extension and control machine at the 940

3 end of the call, master computer send an end text to the computer monitoring machine, when emergency telephone extension is abnormal, master computer monitoring machine send an alarm text, when emergency telephone extension are back to normal sending normal text to the master computer monitor computer. The expectation value of the packet error rate (PER) is denoted packet error probability pp, which for a data packet length of N bits can be expressed as: N pp 1 1 pe (1) Assuming the bit errors ratio (BER) is independent. For small bit error probabilities, this is approximately: pp pn (2) e The transmission signal was checked during the 15km transmission, the BER of the signal should no more than The functions of the roadside extensions includes: send the SOS signal with the position information during the emergency situation, receive the signal from the control center and establish or remove the call according to the signal, the hold conversation adopt the hand free function communicated with the control center through the loudspeaker and the microphone, receive the detection signal of the control center and finish the detection process. Nonlinear distortion is a term used to describe the phenomenon of a non-linear relationship between the input and output signals. The power supply can make use of the dry battery or the storage battery. When the dry battery design scheme was adopted, it should be in normal work at least two years. When the latter scheme was adopted, the storage battery should be charging by the remote electric power or the solar power. Using the storage battery as the power supply the roadside extensions should continuous work at least 40 days whenever the equipment await the opportune moment. Mean time between failures (MTBF) is the predicted elapsed time between inherent failures of a system during operation. start of downtime start of uptime MTBF (3) number of failures Transmission medium can select cable, optical fiber and other mediums. When adopt the cable scheme, it is better to select the HYAT cable, the diameter of the cable is usually 0.7mm or 0.9mm. The electrical properties, mechanical properties and physical properties should correspond with GB/T and GB/T criterion. The system should choose single mode fiber, and its performance should be consistent with the ITU-T suggest G.652 rules System classification The development of national HETS is nearly thirty years. Many types of emergency telephones were adopted. Various HETS have their advantages and drawbacks respectively. According to the transmission type we divide HETS in cable type, optical fiber type, wireless type and others. The detail is shown in figure 2: Next different HETS are introduced in sequence. Cable type HETS set emergency call console generally placed in monitoring branch or tunnel station, at the same time set the emergency telephone along both sides of highway or tunnel. HETS is composed of telephone console, remote power amplifier equipment, remote control module, transmission cable, the loudspeaker and emergency telephone extension of roadside etc. Cable type emergency call use local cable as transmission medium. The internal structure of cable is shown in figure 3. The security layers contain the PE outer layer and PE-AL-PP layer. It is widely used in domestic. It has many advantages such as low project cost, easy implementation, mature technology, etc. The emergency telephones along both sides have high reliability, corrosion resistance, prevent noise performance requirements. Users can contact the monitoring center as soon as pick up the emergency telephone. And the monitoring center warning system is launched automatically, it can show geographical location of the user and deal with the procedure of events. Traditional landline telephone system usually uses the cable transmission pattern. 941

4 Figure 2. Classification of Emergency Telephone System Figure 3. The Internal Structure of Cable Cable type HETS is commonly the independent subsystem of highway private network, and later without pay to the public network communications combined operation. Originally this transmission way has been widely used in domestic highway. But with time elapsing cable type HETS also gradually revealed some drawbacks: 1) Due to the analog circuit design, components influence by the environment set-point drift, causing the fuzzy, large noise, low voice call quality, difficult maintenance and high repair price; 2) Extension telephone has high failure rate and the later maintenance cost is high. Due to its own structure, a few extension telephone of roadside fault will cause a large section of telephone can`t be used normally; 3) Initial large investment, large quantity, not easy to maintain, need to lay cable for the system, and take up pipe resources; 4) The cable aging serious when the environment is damp. The insulation resistance will decrease when the cable in water for 1~2 years later, at the same time the call quality is affected. With the rapid development of optical communication technology, recent years optical fiber type call system in highway for help and rescue communication emergency fill the blank of highway emergency telephone [23]. At present, optical fiber type HETS is mainly divided into two types: forwarding type self-healing ring structure and passive optical network structure. General use double fiber transmission, through the use of WDM technology can transmit in the same optical fiber contained both receiving light and sending light [12]. Some products also increase a core optical fiber in order to transmit triggered signals or control signals, etc. Forwarding type self-healing ring structure HETS is composed of emergency telephone extension of roadside, console of management branch and optical fiber transmission equipment. The whole system can be made of 1~8 two-way self-healing ring structure, every single fiber two-way self-healing ring need to connect 32 emergency telephone extension, the whole system can accept most 256 emergency telephone call at the same time. The system is controlled by computer and use the software to realize the man-machine dialogue. The console of management branch control the real-time various states of emergency telephone. Phone calls of voice to be automatic record, print reports, can set multi-level management mode, and realize the whole province, the centralized management, and can provide many asynchronous data of highway channels for other information transmission. 942

5 Efficient Classification Scheme of Tendency of Highway Emergency Telephone System Figure 4. The Scheme of Optical Fiber Transmission The scheme of optical fiber transmission is shown in figure 4. Many hosts and auxiliaries connect with one control center. The repeater is used to reinforce the signal for long distance transmission. HETS of passive optical network structure is composed of emergency telephone extension [14-17] of roadside, management center master console and optical fiber transmission equipment, etc. The system adopted the optical passive technology, making each extension in standby mode during the no communication state, in order to reduce the power consumption of the extension. Due to the use of optical passive optical technology, the system needs double optical transceiver and optical fiber to ensure the transmission reliability, each machine extension as a branch node of optical transmission link, so the failure of one extension will not lead to communication interrupt of other extensions. The optical type emergence telephone system in highway is shown in figure 5: Figure 5. Highway Optical Emergence Telephone System Compared with the conventional HETS, optical fiber type HETS has the following features: 1) Small attenuation, long transmission distance, high system reliability; 2) Wide frequency band, low wastage, anti-jamming, high quality voice, no noise accumulation; 3) Strong ability of anti-jamming and lightning. The system uses optical fiber as a transmission medium, not by the electromagnetic interference and has the very strong lightning protection performance, especially for the mountainous area and the lightning multiple areas; 4) Simple construction and small investment. The system makes use of optical fiber as the transmission channel, and the channel can be used as communication optical transmission. The main construction can be finished at one time and need not additional cable, reducing the cable fees and the workload of construction; 5) Adopting the solar energy and battery to supply power, self-healing ring structure can provide one month electrical energy for work during the rainy days; 6) High integration and can be integrated well with the highway monitor system providing many asynchronous data channels. The system adopts full-duplex transmission, each extension machine of roadside can provide additional 1~2 RS422 interface. Other information such as low rate monitoring data can transmit through this system. 943

6 Wireless type HETS is developed by wireless mobile network. The reliability and speech quality is excellent compared with the cable type system and the optical fiber type system [13]. As the development of mobile communication network and the improved quality of service, it becomes a development trend using public wireless communication network to construct wireless HETS. Wireless systems use radio frequencies in the VHF or UHF business band radio spectrum. Many HETS can be programmed to be compatible with virtually any brand of VHF or UHF business band portable or fixed base radio. The network mode of wireless type HETS can be divided into GSM public network mode and custom wireless network mode. 3. Experimental results In the wireless type emergence call system based on the GSM public network, each pair roadside emergency telephones in call pavilion installed a set of the main communication controller and solar battery power supply system. General control device of the call processing center installed a set of communication controller and wireless HETS host, in order to communicate the call processing center through the wireless telephone extension after the SIM card registration of the roadside emergency telephone extension. All of these formed a complete set of HETS. The scheme of wireless transmission is shown in figure 6. Figure 6. The Scheme of Wireless Transmission Special wireless type HETS of ultra short wave radio generally uses full-duplex working way. Its working band is generally divided into 150 MHz, 450 MHz, 800 MHz, 900 MHz. The working band needs to be approved by the committee of national radio before the construction. At present, this type of HETS barely appeared in the highway application. If the required distance is greater than the range of the wireless call box, an external antenna can extend the range. In the range, radio repeaters can extend this range even more. The best advantage of wireless HETS is without laying transmission cable, convenient construction, simple maintenance and reducing the initial construction period. Due to wireless emergency telephone extension with no long wires lead thunder, the possibility of lightning damage is small and the maintenance is simple, not affected by the transmission cable faults. At the same time each extension has a unique address, so each extension is independent, not affected by others. The extension density of each host control zone can be increased gradually according to actual situation, suitable for staging investment and gradually improvement. Compared with cable transmission system, the speech quality of the wireless type HETS is influenced by the coverage of radio and weather conditions, and vulnerable to interference. Adopting the GSM public network, HETS is not independent system, which service quality is restricted by the public 944

7 network, and later need to pay communication fee for the public network. At the same time wireless emergency telephone had a fatal flaw: communication quality will be discounted greatly in the wireless signals blind remote mountainous areas. There exist several key questions in HETS: 1) System control software: An advanced HETS must have the corresponding control software support. The system control software includes the host management program of control center, which controls the automatic recording of multimedia voice signal, information storage and information output, management of extension communication. In addition the software requirements contain the solar battery management of the extension, etc; 2) Use the different frequency duplex working way of transmitter and receiver to solve the full-duplex call problems between the host and extension; 3) The case structure: emergency telephone extensions are set out-field, so they need to adapt different weather conditions [22]. As design and manufacture the case, rainproof, dustproof, high temperature prevention and low temperature prevention and other factors must be considered. In addition transmitter and receiver are taken security protection in order to prevent man-made destruction. 4) Component: all key integrated circuits use the foreign temperature standard [24]. The products must meet the -40 C~+60 C temperature standard in order to ensure the system work stable. Emergency telephones will be replaced by mobile phones in good wireless coverage area. Opening the emergency services is a developing trend through wireless expanded network service in the highway. Cancel the emergency alarm facilities does not mean reducing the level of social service. However, it means reinforcing the emergency alarm facilities and making more economy, convenient, promptly and humanized. Emergency telephones are necessaries in the tunnel and wireless network coverage poor areas, which are still one significant rescue method in highway. Using the mobile phone instead of the emergency telephone in the new constructed highway, the relevant mileage pile number sign and direction sign must be set properly. Finally the managers make relevant department coordinate of the work. Adopting the mature technology and equipment, in order to develop and expand the rescue service constantly, improving highway multiple service level. As mobile phones popularizing step by step, the mobile phone brings a lot of convenience when the accident happened in the highway. But mobile phone cannot instead of the emergency telephone, the main reasons are shown as follows: 1) Both mobile phone and emergency telephone can give an alarm, both can provide rescue services for highway emergency, but each one has its advantage along with the shortage; 2) An emergency telephone is a special communication rescue tool, which is not restricted by any condition. Finally the emergency telephone is waiting for rescue every moment. 3) An emergency telephone as a special communication rescue tool has the strict process of emergency alarm rescue. 4. Conclusion Emergency telephone is a phone specifically provided for making calls to emergency services and is most often found in a place of special danger or where it is likely that there will only be a need to make emergency calls. Summarizing the experience scientifically and objectively in order to gradually improve the expressway monitoring system and emergency call center system. The application of national highway emergency rescue system is developed and innovated gradually, which becomes an important part of the intelligent transportation system. It will provide a safe, reliable, economic, efficient, harmonious traffic environment for the society. 945

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