Demonstration of ATMS using Wireless Broadband network with NTCIP Tang-Hsien Chang 1 , Hung-Jen Huang 2 , Ming-Ju Tsai3 ITS Lab of Transportation Eng., Dept. of Civil Eng., National Taiwan University, No.1, Sec.4, Roosevelt Rd., Taipei, Taiwan E-mail:
[email protected] This paper presents the project of the demonstration of Advance Transportation Management Systems (ATMS) using wireless broadband network with the National Transportation Communication for ITS Protocol (NTCIP). The project team is combined of academia, industry, and officials in Taiwan. It adopts NTCIP, STMP, TCP/IP, PSDN, the communication protocol V.92 and the standard software for urban traffic control system that published by Ministry of Transportation and Communication (MOTC), Taiwan, ROC. As the aspect of hardware, the research demonstrates how to integrate wireless communication techniques and roadside devices including traffic signal controller, vehicle detector, and CCTV into various compatible modules of traffic control devices. According to the functional demands, an integral device named Traffic Control Information Station (TCIS) is being developed and designed. Wireless LAN is utilized as a network platform to connect every device of ATMS proposed in this project. Such arrangements have advantages of saving time and money for construction, reducing complaints from civilians during the construction period, and providing multiple purposes and practicable solution of ATMS. The results of the research will play an important role and be the milestone of the ATMS deployment in Taiwan in the coming future.
1. Introduction Traffic congestion is a general case in most metropolises all around the world. Hence, how to make traffic management systems perform more effectively and intelligently is an important topic for authorities concerned and so do Taiwan government today. In the past, we used to adopt point-to-point protocol to construct communication network that had to excavate road surface in a wide range to set underground wire channel for specific traffic control device. Usually, the process of construction needs lane closure that might result into traffic congestion and complaints from citizens and travelers. Any new and existing devices such as traffic controllers, vehicle detectors and so on could not share existing wire channel and communicate directly with each other. Therefore, the communication network construction method at present might be a cost consuming and lake of resource and constructing efficiency. Furthermore, almost all types of signal controller in Taiwan are designed into single-chip computers, and they could not be interoperated across different districts because
there are no standards about hardware for manufacturers. It would be a serious obstacle to develop ITS in Taiwan. Therefore, MOTC authorized and funded this project for a demonstration of ATMS part traffic control network using wireless LAN technique to overcome disadvantages mentioned before. The works of the project were develop a Local Traffic Controller and some compatible intersection controllers suit to traffic demand, adopt TTCIP to build wireless traffic signal control network, demonstrate designing simple transportation messages Protocol (STMP) dynamic object and security concern of IEEE 802.11x wireless LAN standard manufactures. The achievements could build a wireless LAN traffic control network does not need to dig surface trouble maker of traffic efficient, noise, complains, and contributing cost waste, time consuming and fundamental network contribute utility efficient.
2. Project Contents Wireless broadband transmission technology has made great progression rapidly in recent years.
1
From the standard of IEEE 802.11b, its bandwidth has reached to 11MBps, and such as 2.4Ghz, 5.8Ghz ISM Band, and IR communication technology, their medium coverage can be more than 10 kilometers. Hence, we plan to replace traditional wired network with wireless network for the purpose of decreasing construction cost and increasing system adjustability. We had analyzed and sorted all kinds of communication technologies applied universally today (see Table 1 and Table 2). Transmission Medium Wired Communication Technology
Twisted Pair Coaxial Cable Fiber Cable POTS B-ISBN HFC
Table 1: Wired Communication Mediums and Technologies Short Distance Wireless Communication
Long Distance Wireless Communication
Bluetooth IrMC IEEE802.11 Home RF
Cellular Phone Network
NTCIP, STMP, the communication protocol V.92 and the standardized software for urban traffic control system published by MOTC (see Fig.1), besides this ATMS also including TCP/IP PSDN. Therefore, to localize and practice the concept and advantage of NTCIP, we have a localized protocol named TTCIP or NTCIP-like. Taiwan also created itself Management Information Base (MIB) in several TTCIP or NTCIP-like related projects authorized by MOTC before. As the aspect of hardware, the research would like to integrate some roadside devices like traffic controller, vehicle detector, and CCTV to various controller modules. By the way of wireless broadband transmission technology, we could establish a wireless network platform reserved for the use of traffic control for this demonstration. The major work contents and purposes are: 2.1. Developing an intelligent TCIS that contains a local signal controller
AMPS GSM CDMA PHS GPRS TDMA 3G
Radio network Mobile Data CDPD DataTAC Satellite Cellular Phone System Table 2: Wireless Communication Mediums and Technologies
The carrying out of National Transportation Communication Protocol (NTCIP) in the United States makes all units about ITS development under the standardized network architecture, and meets the requirement of 3I (Interchangeability, Interoperability, and Interconnectivity). The advantages of adopting NTCIP mainly include avoiding early obsolescence, providing more choices of devices manufacturers, and so on. We would conform to the concept of the development of intelligent city, thus the research of this project combines the academia, the industry, and the officials in Taiwan, and adopts
Fig 1: The standardized software running picture An excellent ATMS needs to use applicable control equipments. This plan intends to expand the functions of a traffic signal controller to become an intelligent TCIS. The special design of module-like make our newly designed TCIS will have the ability to process wireless transmission, data collection, signal control, and reserve the capability to add more functions in the future. What is more, all functions of traffic management above can be adjusted to be in accordance with the time and the place. It could make the management select appropriate equipments more easily and flexibly. The
possible module-like types of the TCIS are shown by the four illustrations below: (Fig.1~5)
Signal Controller C3
Com. Module
COM
GPRS
Signal Controller C3
…
LAN
Ethernet, deliver compressed files captured by CCTV backward to traffic control center via WLAN and collect traffic parameters provide TCIS to make control decision online. It could support to serve several intersections as a local traffic signal controller.
hub
CPUMain Board
C2 Type The C2 type controller shown as Fig.3 module involved devices signal controller and CCTV could enforce timing plans by TCIS or traffic control center and provide traffic monitor function. Image data would be sent by WLAN, however the signal controller would communicate with TCIS or traffic control center via GPRS else.
CMS
Vehicle Detector
sensor C
WLAN
BNC Cable
TCIS (C1 Type)
CCTV …
Image Processor
C
CCTV
Fig 2: C1 Type TCIS
GPRS
Signal Controller
WLAN
CCTV
BNC Cable
C
C2 Type
Fig 3: C2 Type TCIS
GPRS
Signal Controller
GPRS
Vehicle Detector
sensor
C3 Type
Fig 4: C3 Type TCIS
GPRS
Signal Controller C4 Type
Fig 5: C4 Type TCIS C1 Type The C1 type of TCIS (see Fig.2) has all the complete functions including the devices vehicle detectors, the image processor, and the wireless module. It could connect with several signal controllers through a Hub by
C3 Type The C3 type controller shown as Fig.4 module involved devices signal controller and vehicle detectors could enforce timing plans by TCIS or traffic control center, and might support to actual or dynamic traffic signal control logics. Both of signal controller and vehicle detector communicate with each other and traffic control center via GPRS else. C4 Type C4 type is the simplest form of the TCIS that could be treated as traditional signal controller (see Fig.5). It could enforce timing plan by order of TCIS or traffic control center or time of day (TOD) timing plan. The complete and detailed modules that a TCIS we design should include: CPU module Power module I/O module Communication module Roadside induction control module And the IPC (Industrial PC) specification should conform to the standard of the industrialization. Besides, there should not be any rotated mechanism inside the TCIS lest influence the normal operation of the system because of breakdown of machinery. 2.2 Establish wireless control network for ATMS
As the bus design that is adopted universally by IT industry today, it enables the roadside devices and TMIC (Traffic Management Information Center) to be totally under the same network by connecting with advanced TCIS mentioned before. As interface demand was standardized and the demonstration of wireless communication platform was accomplished successfully, control network for ATMS construction would cost down and decrease the impact of traffic during constructing process in evidence. The interface also could apply to NTCIP, STMP, TCP/IP, and which would convey the image files of real traffic flow with highly compressed format. The function includes provide not only GPRS and 3G RF but a suit of IP base PSDN. Data flow transition between signal controllers, vehicle detectors, TCIS and traffic control center would be planed to launch via GPRS RF. Highly compressed format images would deliver via wireless LAN network. 2.3 Security Concerns While 802.11x adopted in ATMS of this project has experienced a rapid growth in the wireless local area network LAN environment, a number of security concerns have been raised for wireless networks in general and so does this project. The 802.11x wireless LAN standard defines authentication and encryption services based on the Wired Equivalent Privacy (WEP) algorithm. The WEP algorithm defines the use of a 40-bit secret key for authentication and encryption. Many 802.11x implementations also allow 104-bit secret keys. However, the standard does not define a key management protocol, and presumes that the secret, shared keys are delivered to the 802.11x wireless station (STA) via a secure channel independent of 802.11. The lack of a WEP key management protocol is a principal limitation to providing 802.11x security, especially in a wireless infrastructure network with a large number of stations. When manually configured shared keys are used, the keys tend to remain in place for long periods of time, enabling hackers more time to use various attack to obtain the keys and decrypt the traffic. The lack of authentication and encryption services also effects operation in a wireless, ad
hoc network where users may wish to engage in peer-to-peer collaborative communication. As a result, the enhanced importance of authentication and encryption in a wireless environment build for ATMS proves the need for access control and security mechanisms that include a key management protocol specified in 802.11x standard. Thus we would use C# high-level computer language to code for access control and security mechanisms of ATMS that include a key management protocol in the project. 2.4 Dynamic Objects Concerns Dynamic Object was defined a set of managed objects have correlation by NTCIP. For example, if someone wants to adjust the clock of some managed object, it needs object name, clock, and the value of time these three related objects could be combined to a dynamic object. The purpose of dynamic object is to minimize the expenses of bandwidth, especially to some objects or orders that manager use very often and repeatedly. Such advantage might overcome transmission error happened on information traffic congestion. NTCIP documents about STMP defined dynamics basic structure and shown as Fig6. Basically, dynamic object use a table to involve all objects in itself and it was formed as table 4 and the columns are listed below: dynObjNumber: Number of dynamic object. dynObjIndex: Sub notation of dynamic object. dynObjVariable: Variables of dynamic object. dynObjOwner: Owner of dynamic object. dynObjStatus: Status of dynamic object. p ro to c o l
d y n O b jM g m t
d y n O b jD e f
d y n O b jD a ta
T a b le
Fig.6: Structure of dynamic object
This project would concern to take the advantage of dynamic objects to decrease the overhead of several objects included in the same order that manager use very often and repeatedly to decrease network flow loading and create some useful dynamic object according to project demand as a demonstration. It would involve C2C, C2F and F2F dynamics objects that could be classified as table 3. Dynamic Object Member
Elements BUS Structure
ARM 32bita Bus System, Multiple
8086 16bits Independent Bus Interface Enforcement Unit CISC Framework and 6byte command Queue.
Process Cycle
Reduce Command Implement Cycle Time
Capture and Enforce Cycle Stack.
Command /Frequency Max. Frequency Memory
1：2
1：4
80486 32bits 5 Stages Pipe RISC Framework, Embedded 8Kcasche and Float Calculation Unit. 5 Command Could be Delivered Via Pipe in the same Time. 1：1
50MHz
10MHz
100MHz
4MB-8MB
1MB
4G(4096MB)
Receiving
No. CENTER TCIS CCTV VD Dispatching CENTER 1 3 4 6 TCIS 8 2 5 7 CCTV 9 11 VD 10 12 -
Table 3: Dynamic Object Member Class
Table 5: Comparison of 80486, ARM and 8086 2.5 CPU and OS of controller concerns Item
Main board of TCIS design elements include INTEL-80486 embedded CPU collocate Linux embedded OS. It could vary traffic signal phase, communication transmission, data processing, control logic inference, etc traffic management basic and advance functions. Moreover, such traffic control unit could be helpful for developing ATMS. For INTEL-80486 involved distinct performance main board, inner processor temp mechanism and 32-bit IPC BUS that could access 4GB substance address which is high process speed that frequency reach 100MHz possess high integrated elasticity. The embedded 8k flash RAM and one float process chip could speed up calculation speed 10 times more than ongoing CPU module and have a better fit to communication interface demand and operation system of ATMS. Linux Real Time OS (RTOS) is comparative Time-Sharing OS (TSOS) such as the Windows we touch regularly is a kind of TSOS. RTOS could response outer requests in real time, complete task in time and console every task process smoothly and consistently. In proportion to TSOS, RTOS has advantages Multi-Service, independent, real time, mutuality and reliability to satisfy speedy traffic information flow, processing and real time response for ATMS. Several CPU and OS was classified as table 5 and table 6:
Copyright Fee Purchase Cost Technique Support
Network Feature Software Transplant Application Software Developing Cycle Real Time Performance Stable
Reserved Embedded RTOS (OS-9、 SUPERTASK) Every Product should be charged. Several one hundred thousands.
Embedded Linux
Limit to only supply by developer
Open source code and support by free software developers all around the world. Free and outstanding function.
Purchase cost several one hundred thousands in additional. Hard, because it is a closed system. Long, because reusable code is limited.
Fine Fine
free free
Easy opened source code and various application software supported. Short, new products spread instantly, because a lot of code could be transplant. It could be compensated by RT_Linux modules. Better than list left, but it should be improved for high performance systems.
Table 6: Comparison of embedded Linux and some other OS. 2.6 Demonstrate the project and publicize our achievement. The standard traffic control software is provided and maintained by MOTC according to custom-made for specify user included the project. In this project we would associate
MOTC to expand function, especially wireless communication and dynamic objects promoted by NTCIP and Taiwan Transportation Communication protocol TTCIP.
center to center, center to field or field to field could transit via wireless network except image data that need larger bandwidth solution such as 3G or wireless LAN techniques.
We experiment on the wireless ATMS functions to confirm the practicability at laboratory during 2004. In 2005, we plan to select several intersections in a chosen city to construct and test the system in the field. Furthermore, we would hold several exhibitions for spreading our experience and achievement of this project to other districts and institutions concerned in Taiwan. Our work flow chart for this project is shown in Fig.8 below:
All the purposes of this project fit in with the direction of Taiwan ITS development aspire to better traffic environment, devices possess 3I advantage, purchasing and updating more easily, elasticity and open. The successful results of the demonstration project might speed up traffic control network contribute, maximize utility of information fundamental contribution, and minimize impact of traffic and complaint by citizens or travelers.
Test Transmission
MOTC
Software for urban traffic control
Standardization
Executive Body
Authorization
Feedback
TCIS
Wireless ATMS
Development/ Upgrade To hold exhibitions
Wireless Module
Hospital
Selection of demostratio n place
Fig 8: Work flow chart
3. Conclusion
TSC
TCIS
Other SubSysems
ESS
TMIC
The Police
VD
Incident Detection System
Display System
CMS
Workstation Sever
As will as this system would be coming to maturity in the future. Adopting the experiences and achievements developed in this project directly would simplify the steps of analyses or tests and also speed up operation when other cities intend to build up similar system from now on. In addition, the application of wireless broadband transmission technology will be hence more popular and other ITS subsystems might advance more easily. Furthermore, as all module-like devices could be produced commercially, it would make device cost down and exit our own ATMS technique broad word wide. The prospect this project works for is that to establish intelligent cities around Taiwan may be reached more probably. Fig.9 is the suggested structure for a city realizing ATMS. To a control center of a city, information traffic included
Internet
EMS Image System
CCTV
Fig 9: ATMS Structure
References [1] National Transportation Communications for ITS Protocol (NTCIP) Guide, NTCIP Joint Standards Committee, Draft Version 2, 1997. [2] Understanding the NTCIP Class Profiles from an End User’s Perspective, Albert J. Bonificio and Joseph R. Herr, 1998. [3] Tang-Hsien Chang (National Taiwan University), ITS Complrehensive Planning for Taipei City, MOTC, Taiwan ROC, 2001.
dynObjNumber dynObjIndex dynObjVariable dynObjOwner dynObjStatus 1 1 1.3.6.1.4.1.1206.4.2.6.3.4.3 NTCIP Guide Example 1(Valid) Table4: Table of dynamic object format
