IntelliDrive sm at 4.9GHz for Transit ITS Unified Communication Architecture for an ITS Enterprise and Pathway to DSRC

Transcription

1 IntelliDrive sm at 4.9GHz for Transit ITS Unified Communication Architecture for an ITS Enterprise and Pathway to DSRC Bryan Nace, CCNP DKS Associates John Toone, MPA King County Metro IntelliDrive sm is generally associated with the 5.9 GHz Dedicated Short Range Communications ("DSRC") spectrum for wireless connectivity. King County Transit s deployed its ITS Architecture using the 4.9GHz Public Safety band as an extension of the King County enterprise network. Does this hybridization conflict with the US DOT vision? There are many benefits to this architecture, including a path to transition to DSRC.

2 Abstract King County Metro Transit (Metro) serves 1.7 million people located in King County, Washington. Metro operates a fleet of about 1,300 vehicles -- including standard and articulated coaches, electric trolleys, and dual-powered buses. These vehicles serve an annual ridership of 100 million passengers within a 2,134 square mile area, serving the cities of Seattle, Bellevue and the surrounding area. In 2006, Metro desired a regional expansion to its enterprise network to provide an access layer along high use corridors of the transit service area. This access layer would provide ITS enhancements that include roadside traffic signal control, signal prioritization, enhanced GPS location resolution of the existing Automatic Vehicle Location (AVL) system, Real Time Traffic Information System (RTIS) enhancements, Customer Itinerary Planning, and on-street electronic fare collection. The solution is an operational implementation of the IntelliDrive sm vision of the U.S. Department of Transportation (US DOT) that uses the FCC allocated 4.9 GHz Public Safety band for the wireless component. IntelliDrive sm is described within the National ITS Architecture and supported by US DOT. This vision promotes a surface transportation system for travelers to have comprehensive and accurate information on travel options transit travel times, schedules, costs, and real-time locations; driving travel times, routes, and travel costs; parking costs, availability, and space reservation information; and the environmental footprint of each trip. The Metro deployment is the first of its type in the nation to be based upon the IntelliDrive sm concept. IntelliDrive sm, however, is generally associated with the 5.9 GHz Dedicated Short Range Communications (DSRC) spectrum for wireless connectivity. Does this hybridization that mixes Public Safety with DSRC use conflict with the US DOT vision? Does the use of 4.9 GHz spectrum within an ITS deployment negate the goal of Interoperability with Public Safety? How does each, 4.9 GHz and 5.9 GHz, relate to the larger hierarchical Enterprise network? Why did King County choose Public Safety 4.9 GHz wireless? This paper provides a discussion of how DKS Associates, working with King County Metro Transit and Office of Information Resources, designed and deployed an IP enterprise architecture to manage these differences in a way that enhances the goals of both IntelliDrive sm and achieve Interoperability between Public Safety and Transit ITS organizations.

3 Background Why IntelliDrive sm? An IntelliDrive sm system, as envisioned by the US DOT, would form the core of a group of applications that manages information from a variety of roadside sources. Some of these sources are highway dependent, some agency related, some media related, and others are vehicle situation dependent (see Figure 1). To bring this aggregation of information together requires an underlying architecture that supports a regional and interagency enterprise. This enterprise, autonomous from other King County IT functions, supports the core application traffic and timing requirements in addition to the overall network security from unauthorized intrusion. U.S. DOT IntelliDrive sm System Vision (Figure 1) Ref: US Department of Transportation A key feature of this network, named King County Transit ITS Network, is that it seeks to unify communications though a multipurpose medium. The design provides for every communication exchange in the National ITS Architecture: wireless communication for vehicles to other vehicles, the roadside and centers; wired communication from centers to the roadside and from center to center, video, and multimedia. Following the National ITS Architecture model in the

4 development of the Transit ITS Architecture led naturally to the use of the Vehicle-Infrastructure Interface (VII) concept, now evolved and branded as IntelliDrive sm. IntelliDrive SM is a multimodal initiative that aims to enable safe, interoperable networked wireless communications among vehicles, the infrastructure, and passengers' personal communications devices. -IntelliDriveusa.org The IntelliDrive sm concept exactly fits the requirement to provide an open network for Transit ITS communications. The multipurpose wireless network deployed by Metro supports many systems with varying communication needs, not only for vehicles, but also for last-mile communications which can be used to avoid costly sidewalk replacement or road resurfacing. Communication exchanges used in the King County Transit ITS Network architecture are shown in table 1 below. Table 1. King County Transit ITS communication exchanges System Center to: Vehicle to: Roadside to Center Roadside Vehicle Roadside Center Roadside Transit Signal Priority CAD/AVL Real-Time Passenger Information Off-board Fare Payment Transit Security Video Signal Control Infrastructure management Using the IntelliDrive sm model also prepares the architecture for future technologies and systems. Having the structure in place, Metro expects to be able to more easily take advantage of the ongoing growth and development in the ITS industry.

5 US DOT IntelliDrive sm Taxonomy Types in the ITS Network The US DOT has established taxonomy of data types and time criticality that describe an IntelliDrive sm System. These taxonomies are based upon familiar source-destination concepts that one would see with TCP/IP Internet traffic types. There are two levels of data as shown in figure 2 (US DOT IntelliDrive sm Taxonomy of Data Types). Level 1 is mobility based applications, for example enhanced GPS location data, toll tags, and e-payments. These activities involve an exchange of information from a vehicle to some roadside/system application. Level 2 transactions are more safety related and take place between vehicles (V2V Vehicle to Vehicle) or between vehicles and intersections (V2I Vehicle to intersection). While not currently available in the US, there are provisions within IntelliDrive sm for vehicle manufacturer proprietary transactional data. Referring to the taxonomy types in figure 2, the King County deployment meets all the requirements of Level(s) 1A, 1B, 2A,2B data. It will also support, should technology become available in automotive industry, Level 2C data. Support for Level 2C transactions will likely require a 5.9GHz DSRC wireless link. 4.9 GHz and 5.9 GHz Band Communication FCC Interoperability The 5.9 GHz spectrum, DSRC, originated from Congressional Intermodal Surface Transportation Efficiency Act (ISTEA) legislation for a National ITS Plan and Architecture. One of the FCC stated goals in the allocation was a desire on the part of the FCC to facilitate nationwide compatibility and interoperability of [ITS Applications]. 1 The 4.9 GHz, (Public Safety) band allocation was post 9-11 as an effort to promote network reliability and interoperability during times of crisis by the DHS/FCC. The FCC order, WT 00-32, transferred the spectrum to Public Safety use. Paragraph 2 of the order references the need to 1 Federal Communications Commission Notice of proposed Rule Making, FCC , Washington, D.C.

6 provide a regulatory framework to enhance support between traditional and non-tradition entities both sharing common public safety roles. 2 Both Pubic Safety and DSRC allocations provide for a similar band plan for projected usage that is approved by the FCC. The 4.9 GHz Public Safety is 50 MHz of spectrum with 18 channels that can be aggregated to produce 5, 10, and 20 MHz usage channel. The 5.9 GHz is a broader 75 MHz allocation with 11 channels that can also be aggregated into 5, 10, and 20 MHz usage channels. The US DOT envisioned the wireless component of IntelliDrive sm (DSRC) to provide a medium that would provide fast network acquisition, low latency and high reliability, priority for safety applications, interoperability, and security for vehicle to roadside or vehicle to vehicle communication. Traditional Wi-Fi could not meet these goals at the time of the allocation. Since 2002, when the 4.9 GHz spectrum was allocated, there have been two major improvements to wireless communications that have enabled the deployment of a network like the King County ITS Network. One is the i standard ratified in This provides for advanced encryptions, AES-CCMP, for security. The second is the emergence through IETF of the Control and Provisioning of Wireless Access Points (CAPWAP) protocol. This proposed standard addresses the management and centralized control of wireless termination points, e.g. access points. 3 With the improvements in i security and the evolution of CAPWAP Protocol, regional, centrally managed, wireless deployments providing IP mobility and enterprise level security became possible. Especially important, with respect to interoperability, is the standardization of these protocols. These improvements, along with 802.1X authentication standards, are available in the commercial 4.9 GHz Public Safety solutions but not yet in 5.9 GHz DSRC. Why 4.9GHz? While the FCC did not mandate an actual protocol for 4.9 GHz, the FCC did specify the spectral mask for power to be consistent with standards for low power masks (DSRC-A) used by Wi-Fi Access Points. Several equipment vendors, such as Cisco, Motorola, and Ubiquiti, leveraged their existing expertise into the new band using ODFM modulation along with the power mask. Thus at design time in , wireless systems utilizing the a standard with the 4.9 GHz bandwidth existed in quantities large enough to compete for 2 Federal Communications Commission, Memorandum Opinion and Order and Report and Order, FCC 03-99, Washington, D.C. 3 P. Calhoun et. al, CAPWAP Protocol Specification Draft, RFC , Internet Engineering Task Force

7 procurement dollars. At that time similar levels of technology using DSRC were not yet available. Deploying a 4.9GHz network also provides for interoperability partnerships with the public safety sector. This helps make the case for allowing public transit access to the public safety band, which is additionally helped by transit s role as a second responder supporting police during social unrest and evacuations. The King County Transit ITS Network architecture provides network access for transit and county law enforcement. In an emergency, the network can be used for access to the Internet, WAN and high-speed communication among field locations. This interoperability opens the opportunity for transit and public safety to cooperate and build physical infrastructure that supports both activities. Using the OSI Reference Model Architecture to Describe Communications As a framework for discussion of this type of enterprise, a hierarchical view of the supporting network(s) and interconnections is helpful. A common tool for this view is the Open System Interconnection (OSI) Reference Model. An examination of the deployed King County system in the context of the OSI Reference model will allow focus on how the wireless frequency choice fits into the larger enterprise. The OSI Reference model has its origin from the International Organization for Standardization (ISO) dating back to initial activities in It has seven (7) modular and hierarchical layers (or groups) that describe how communication between two end users should take place. Associated with each layer are standardized protocols developed by ISO and other standard organizations such as Institute of Electrical and Electronic Engineers (IEEE), American National Standards Institute (ANSI), and the International Telecommunications Union (ITU). The three lower layers of the model describe protocols pertaining to the media through which the communication is passing and the upper four describe the nature of the host-to-host communication. The OSI Reference Model and the familiar TCP/IP Abstraction Model (RFC 1122) will help focus the discussion of differences between 4.9 GHz and 5.9 GHz wireless communication.

8 A basic view of this OSI Reference Model, the TCP/IP Abstraction Model, and common protocols as they relate to wireless access is shown in Fig 3. Using this tool as a reference model, one can see that frequency of the wireless medium only affects the physical layer of communication. Clearly both a DSRC IntelliDrive sm System and Public Safety System must share an adherence to protocol standards at all layers above the physical medium for the enterprise. With the modular component design of some vendors, a change from one frequency band to another only involves an exchange of radios and the supporting firmware. Understanding the requirements for the architecture and the state of technology at design time, King County Transit Metro recognized a strong business case for deploying 4.9 GHz wireless. While their long range plan is to use DSRC, the 4.9GHz systems are functionally similar to 5.9GHz systems. A future change to, or inclusion of, the DSRC band would involve additional cost, but much less than a complete redevelopment and deployment. Pathway to a 5.9 GHz DSRC Solution The King County 4.9 GHz deployment utilizes a Cisco mobility wireless solution with modular wireless interface card client architecture and a similar approach for the wireless access point. Key to the notion of interoperability, this modular architecture concept allows for a clear pathway to implementation of a full DSRC solution. In the case of the King County mobile client, the Wireless Mobile Interface Card (WMIC) is a Cisco 3202 device. This card utilizes a framework of IEEE a protocol with ODFM modulation but is frequency adjusted to the 4.9 GHz Public Service band and channel plan. A similar module, the 3205 (5.0 GHz UNII) version of the WMIC card, is used for 5.0 GHz a clients, and another modular WMIC, the 3201 model is used for 2.4GHz b/g clients. This modular approach to wireless clients (and Access Points) is used not only by Cisco but by several vendors. As the discussion of the OSI reference model in the previous section shows, the frequency specific RF components needed to modulate/demodulate data frames onto a carrier frequency describe the physical layer of the architecture. All layers above would utilize the same standard IP based protocols. This is especially true with 802.1X extensions and i WPA2 encryptions. One can see the efficiency of design to mix and match wireless clients (or AP radios) with the vendor hardware to support the enterprise wireless requirements. Thus a pathway to a full featured, enterprise ready, DSRC solution at 5.9 GHz might also start with the model 3205 WMIC (IEEE a) and incorporate component changes to utilize a 75 MHz bandwidth 5.9 GHz spectrum instead of 300 MHz one for 5.0 GHz UNII. Given the knowledge of dynamic channel width for the 5, 10, and 20 MHz channel width already incorporated in the 3202 model WMIC for 4.9 GHz, the pathway to DSRC channel widths is defined. Using these known and proven technologies of the modular interface design, an efficient development path is available not only to Cisco but to other wireless vendors. Further, the emergence of the CAPWAP protocol allows for the standardization of the interoperability feature that is so important to both Public Safety and DSRC bands usage. It also provides a

9 central control capability for a wireless LAN that would be needed to manage large scale regional deployments. The Benefits of a Unified Communication Architecture for IntelliDrive sm There are many systems available to transit today that use technology to improve the efficiency of operating and managing a large metropolitan transit system. These Intelligent Transportation Systems (ITS) provide vehicle location, traffic signal prioritization, traveler information, fare payment options, security video and more. All these systems require data communications. This is best provided by enterprise architecture using a Unified Communications approach. With an ITS network architecture using this approach in place, an agency s ITS program is scalable and extensible. This leads to lower costs and potential for greater benefits as well as providing for interoperability between vendors and other agencies. King County Metro Transit ITS Network utilizes inputs from onboard Vehicle Logic Unit (VLU) in the form of enhanced location and route status and their ORCA tm onboard fare system to provide updates to traffic signals, traffic signal prioritization, and roadside passenger information signs. The system is scaled to currently support 1700 buses, 5 rapid ride corridors, 250 roadside Tech Pylons, 250 Roadside ITS cabinets, 5 transit bases, and King County Traffic Control Center. A view of the functional elements is shown in Figure 4 (King County ITS Architecture Design Goals). The 4.9 GHz Public Safety wireless is currently the physical medium for access to the ITS applications. At a future point in time where DSRC wireless elements compliant with the emerging P DSRC standard, i, and the IETF CAPWAP protocol, both 5.9 GHz and 4.9 GHz licensed frequencies could be used for full DSRC and Public Safety support.

10 Scalability Scalability helps control the cost of expanding an ITS program. Unified communication architectures, verified in a pilot deployment, provide a template for each subsequent deployment. Site specific engineering is still needed, but some of the normal project engineering costs are eliminated through standardization of the design. These standards are physical, such as cabinet types, fiber optic cable specification, and key equipment. They are also logical, such as equipment configuration, routing structure, and an IP address plan. Adhering to the architecture reduces or eliminates the need for some high labor cost activities such as technology assessment, network design, electrical and mechanical engineering, scheduling, and procurement. Significant labor costs can be saved in operation and maintenance of the systems by using common management tools. There can also be economy of scale where back-office equipment is a one-time purchase and equipment can be discounted through large orders or the use of blanket contracts. A standardized architecture also allows for agency partners to fund and install compatible ITS deployments that can be easily incorporated into the overall program. To achieve scalability, the architecture should be designed to accommodate many parallel deployments with the ability to add additional back-office capacity as necessary. The King County Transit ITS Network will be supporting ten corridor projects, deployed over the next 3-5 years, with scalability up to fifty-seven corridors. A forward-looking design such as this allows for expansion of the overall ITS program through the life cycle of the technologies without redesigning the core architecture. The King County ITS Network applications are hosted in King County facilities. This enterprise core is connected to each Rapid Ride corridor via a transport network using Washington DOT (WSDOT), Seattle DOT (SDOT), or direct connections with individual cities, such as Federal Way, Bellevue, etc. These transport networks provide a distribution layer from the enterprise core to the corridors. To maintain routing to the enterprise core a dynamic routing protocol, Cisco Enhanced Interior Gateway Routing Protocol (EIGRP), manages the autonomous IntelliDrive sm System. Figure 6 shows the distribution to the current planned five corridors.

11 While the initial ITS Network supports five corridors, King County and DKS Associates have provided a scalable design that can be used to expand the footprint consistent with the IntelliDrive sm ITS Architecture goals. While currently deployed with IPv4 addressing, the system is ready for any future IPv6 applications. Provisions for VLAN subnetting, Quality of Service (QOS), Class of Service (COS), and access control between subnets are incorporated and used for IP traffic control. With the exisiting equipment the number of mobile clients can be increased to over 14,000 without any additional infrastructure controller hardware. Figure 6 shows the high level design for scalabilty of the deployment. Extensibility Extensibility helps control the cost of adding new systems and features. Unified communication architecture provides capacity and standards for new systems. This helps reduce labor costs associated with writing specifications, evaluating technologies, and design work. It also reduces risk by providing a proven platform with defined requirements for testing and acceptance. There are also the same savings as with scalability in eliminating duplicate back-office equipment and consolidating operation and maintenance tasks. To achieve extensibility, the architecture should be designed to accommodate many parallel systems utilizing communications standards. The King County Transit ITS architecture supports six existing systems and functions: signal priority, passenger information signs, off-board fare payment, infrastructure management (wireless, switches, UPS, etc.), signal control, and emergency operations. The architecture will support up to four additional systems, including security video. Network standards for wired and wireless communication are particularly important, but other standards such as TCIP and NTCIP do even more to provide for adding new elements to the ITS program. These new capabilities create benefits at a cost less than deploying each system with its own communication infrastructure.

12 Budget, Benefits and Costs Each system in an ITS program has an expected benefit and an associated cost. Unified communication architecture reduces these costs through scalability and extensibility. It also helps control costs by making the costs predictable, thereby reducing the risk budget overruns. An additional advantage is created as the benefits and costs of ITS deployments become increasingly cost effective. Less analysis is needed in the decision-making process to the point where ITS can transition from a project element to an agency program and become part of the core transit infrastructure. This is similar, for example, to the difference between a transit center and a shelter program. The decision to install a shelter is based on simple criteria and is an expected feature of the transit system. In the same way, the decision to install ITS can be made using simple criteria and funded through a permanent capital program. In the scenario of a capital program, the savings of using a unified communication architecture can be seen not only as deploying ITS for less, but also getting more benefit from the capital dollars. Summary IntelliDrive sm at 4.9GHz works for Transit ITS. King County Transit has deployed a working unified network supporting multiple Intelligent Transportation Systems with all the benefits of the IntelliDrive sm concept. The Transit ITS network features scalability and extensibility, integrates with the agency s enterprise network, and offers interoperability with public safety. The wireless 4.9GHz equipment is available in the marketplace now. The deployed and operational architecture for this equipment meets the IntelliDrive sm concept goals. DKS Associates has incorporated within the King County ITS Network design the capability for migration to 5.9 GHz DSRC when the market for this equipment matures. Because this network is based on IP and Transit ITS standards, it will also support a wide range of interoperable unified communications extensions such as voice, video, and multi-media apps. It demonstrates the best principles of both the US DOT IntelliDrive sm and the DHS/FCC Public Safety goals. Finally, by providing a unified communications network, improvements in the effectiveness and efficiency of public transportation and public safety can be achieved.

13 About the Authors Bryan Nace lives in Granbury, Texas. He is the National Network Communications Director for DKS Associates attached to the Seattle Office. He has participated in many ITS deployments since 1992 including the first deployed GPS based AVL in Denver RTD 1992, J1708 based Vehicle Area Network deployment, Houston METRO 1995, and Bus Radio/AVL and APC in Atlanta Bryan has presented at several trade conferences including ITS America Convention, GPS International Conference, American Public Transportation Association Convention, Transit Standards Consortium Symposium. As a consultant, Bryan worked with Navini Networks in 2004 and 2005 as an RF Test Engineer to help develop their Beam Forming Technology, currently part of n technology by Cisco System. He is a Cisco Certified Network Professional in Routing and Switching and Cisco Certified Internetworking Expert in wireless (written exam). John Toone is a Seattle native, working for King County Metro Transit since He received his Master of Public Administration from the University of Washington in 1997, specializing in the statistical analysis of transportation. John has presented at several ITS conferences and was a member of the TCIP standards development committee. John authored the article "Reality Bytes" for the July/August 2009 edition of ITS International. Glossary of Terms There exists a National ITS Architecture framework to guide Intelligent Transportation System deployments IntelliDrive sm is described within the National ITS Architecture and supported by US DOT Unified Communications is an evolving communications technology architecture which automates and unifies all forms of human and device communications in context, and with a common experience. IntelliDrive sm requires Unified Communications Interoperability is a functional goal of Unified Communications as it relates to both voice and data communications. The KC Rapid Ride Project has deployed an IntelliDrive sm system. The autonomous network of the KC IntelliDrive sm System is named the King County ITS Network. The KC ITS Network has an Enterprise Core, and Distribution layer and provides wireless Access layer to vehicle and roadside applications. The wireless LAN access layer of the KC ITS Network uses Public Safety 4.9 GHz frequency, a and CAPWAP protocols.