Jump Starting ITS Deployment in Los Angeles

County using Wireless Communications

Lessons Learned

Project Scope

Provide a wireless communications networks that would allow 1 second polling access to 51 traffic signals & 4 cameras.

Original scope to provide two radio networks – one for Video one for Traffic signal communications

Support a minimum of 4 intersections and a maximum of 8 intersections per T1 communications interface

Interface to existing Type 170E or 170 ATC controllers in 332 controller cabinets

Proposed Approach

One wireless communications network that would support all of the communications requirements

Minimize the use of T1 circuits Provide a common interface at each traffic box

to allow a variety of equipment to be connected.

The Design

Use wireless Ethernet radios to support controller communications.

Provide a serial to Ethernet converter at each controller to allow the controller data to be shipped over the Ethernet network

Use Ethernet routers as terminations at each end of the T1’s to allow a direct interface into the existing County Data communications infrastructure

Provide an Ethernet to serial converter at the KITS server to provide a transparent interface

The Hardware

T1 Communications:– Cisco Router

Wireless communications:– Proxim Radios

RS232 Interface:– Single port Ethernet terminal server installed inside the 170 controller to transport serial

protocol over Ethernet to KITS system (Hardware approach required no space within the enclosure).

Camera Access:– Ethernet switch installed inside the 170 controller to provide local access to the wireless

network and provide an interface for communications access to other devices within the cabinet

Radio Power:– Power over Ethernet card installed inside 170 controller

Interface to KITS– Wireless communications server installed to convert from Ethernet to RS232

Constraints

T1 utilization:– Minimize cost of the T1 installation. (Originally the T1 was to be

installed at an intersection, changed design to allow T1 to be installed at Hawthorne City Hall)

Space:– Minimize the space used inside the existing enclosure (provided

interface cards that could be installed inside the existing 170 controllers thus eliminating the requirement for any space within the enclosure).

Operational requirements:– Support the ability to poll to a minimum of 4 controllers per

second per KITS serial communications port.

The solution

Current status

38 controllers on line with KITS over the wireless communications network

1 camera on line

Base Radio installation

Base radio installation inside enclosure

Power Supplies

Interface card and radio power supply

Lessons learned

Original design:– One wireless system could support both Video and Control

communications. This appears true

– Assumed that one radio could support both north – south and east – west communications.

Found that we needed two radios.– The process of bring a controller on line to KITS requires

manpower in the field and at the KITS server. First site required a coordination using cell phones to validate proper operation.

Change in procedures is being implemented to allow the use of broadband and wireless network to allow complete implementation via field personnel in the field

Lessons learned - Continued

Radio operation:– Once installed, the radio system needed to be adjusted to

allow for optimal operation. Anticipated that this could be done remotely, based upon the configuration requires a second trip to each site.

Need to add loops to the radio network to allow remote optimization.

– Directional antennas are adversely affected by the movement of the cross arm.

Install the directional antennas on the vertical signal pole.

Lessons Learned - Continued

Installation effort– Determine the effort needed to install communications at an intersection.

Typical site can be installed and made operational in under 1 day – (2 man days) Installing the base radios first allows the installation crews flexibility in determining

where the subscriber radios are installed. This minimizes the installation time and allows adjustment for local conditions at each site

– Minimize the space required for installation of communications equipment. For sites that have one radio all equipment needed to support the radio is installed

inside of the existing controller For sites with multiple radios, power supplies mounted on the top of the enclosure

– Minimize the total number of persons involved in the process It appears that the complete installation, startup and turnover process can be done

by field crews.

Lessons learned – Continued

KITS interface Timing Original design was to support 5 controllers per serial port (Maximum poll time per

controller must be less than 200 ms to meet the requirement.)– Original design passed KITS poll message to controller directly. Overall response time

around 200 ms. Changed designed to use CACHE improve response time to under 100 ms.

Original design used an Ethernet terminal server to interface to KITS system. Ethernet terminal server added 40 ms to the overall response time.

– Changing the terminal server to be incorporated into the wireless server. Found the following transport and processing times:

T1 per packet, 5 ms Radio per packet, 30 ms Controller processing time per packet, 20 ms Ethernet terminal server per packet processing time 40 ms Total average message transport time (from the time the first character is sent from the KITS

system to the last character received by KITS for a typical poll message) 170 ms. After replacement of the terminal server response time 90 ms

Moving forward

Estimate project to be completed within the next 60 days Test the network to determine maximum number of controllers

that could be supported by 1 T1 (it appears that 1 T1 will support 50 controllers).

Test the system to determine the maximum number of controllers that can KITS can support on one serial communications line

Evaluate network operation to verify that that the overall up time of 99% could be achieved and what would be required to meet that goal

Install additional communications equipment to allow the wireless networked to be looped (this will increase reliability and allow for remote radio configuration)

Recommendations

Interconnect various medias to validate that they can work concurrently and together, and are compatible

– Consider an approach whereby the various medias (wireless, copper and fiber) could be used to support transmission of controller, maintenance and video information..

– Consider reuse of existing inter-signal communications wiring as Ethernet transport media (will result in a significant reduction in time and cost of system expansion)

– Consider a standard transport communications protocol (Ethernet) and use terminal servers to provide the serial conversion at each individual device – allows for using standard communications equipment to transport all information from each intersection

Recommendations - Continued

Evaluate the uses of wireless backhaul communications equipment to eliminate the need for T1 circuits (there is equipment currently available that supports communications up to 25 miles at speeds up to 64Mbps) Would reduce operations cost will allowing for the expansion of video transport.

Expand the system to support maintenance functionality:– Battery monitoring– Conflict system monitoring– Burnt out light detection

Evaluate the possibility of installing radios on cross arms that can communicate to the controller enclosure without wires (Will significantly reduce the installation cost / time and would allow the ability to install temporary installations)

Recommendations - Continued

Evaluate the possibility of using wireless network to support virtual intersection to intersection communications (Ethernet network is inherently a peer to peer network)

Evaluate the possibility of implementing unsolicited report by exception for state data and counters (this will significantly reduce the overall bandwidth requirements of the system and provide faster response time)