Managing Traffic Lights When Fiber Optic Cable is Not Available
By Chris Wyard, Redline Communications
Traditionally, municipalities have used fiber optic cable to connect GRIDSMART back to the central monitoring location. Fiber cable is an ideal transmission media because it provides high-speed, high-bandwidth connections that support GRIDSMART’s real-time traffic monitoring and management capabilities. More importantly, fiber cable is reliable since it is not susceptible to electrical interference and grounding problems, as are copper wires.
But there is a problem. Fiber optic cable is not accessible at every intersection, whether in large cities or small towns. Furthermore, installing new fiber cable, either underground or overhead on poles, can be very costly for the municipality.
Wireless systems are a viable alternative when fiber optic cable is not available. When considering a wireless media for an intelligent traffic system (ITS) application, it is important to note that not all wireless systems are the same.
Two types of wireless systems are available for ITS applications: Wi-Fi and wireless broadband systems Wi-Fi has been traditionally used because it is widely available and relatively inexpensive with access points supplied by established manufacturers. Using Wi-Fi in ITS applications has operational limitations, however:
- Short range operation, usually only a several hundred meter operating radius
- Low processing power that is not ideal for small packet application such as GRIDSMART metrics
- Connectionless, meaning that it must ‘Listen before Transmitting’ thus introducing latency or delay in noisy RF environments
- Downlink-centric whereas traffic from GRIDSMART is uplink-centric
- Not designed for video surveillance
- If a Multiple In-Multiple Out (MIMO) radio, it usually operates only as MIMO-B that needs high signal-to-noise ratio to double the data speed
By contrast, Redline’s RDL-3000 XP Virtual Fiber™ wireless broadband system fits well with the GRIDSMART performance requirements. Key features include:
- Long range, measured in kilometers versus meters
- High processing power capable of handling more than 280,000 packets per second (pps), ideal for moving GRIDSMART metrics
- Smart MIMO operation that automatically switches between MIMO-A and MIMO-B based on RF conditions and transmission paths. MIMO-A allows line-of-sight (LOS) links to operate in less than perfect path profiles
- Connection-oriented, meaning it transmits regardless of the RF environment with no contention due to RF interference
- Can be configured for uplink-centric operation to fully support GRIDSMART applications
- Purpose-built for video surveillance with a built-in video buffer that can cache data streams so video flows smoothly without pixilation or video artifacts
- Available in a range of unlicensed frequency bands
- Very reliable
Virtual Fiber already is supporting GRIDSMART deployments. The City of Albany, New York uses Redline Virtual Fiber where fiber is not available. The City is very happy with the system performance. Bill Trudeau, the City’s Coordinator of Traffic Engineering says, “RDL-3000 is working as good as our fiber. We really can’t tell the difference from the GRIDSMART on fiber compared to the GRIDSMART on Redline’s Virtual Fiber platform.”
Steven Atkins, principal at Northeast Signal who installed the Albany ITS, found that the RDL-3000 XP radio’s features and management tools were very important for the successful roll-out Fiber-like connectivity the City enjoys over the radio network, is due to the high packet processing power of the RDL-3000 XP that allows small packet traffic to be sent very efficiently over the radio network to the City’s traffic control center.
City of Albany and Northeast Signal, impressed with RDL-3000 XP performance compared to previous wireless selections, are standardizing on Redline RDL-3000 XP for future ITS projects that require fixed wireless access.
Chris Wyard is Product Marketing Manager at Redline Communications, a leading designer and manufacturer of wireless broadband systems for commercial, industrial and government/military applications. Learn more about Redline’s Virtual Fiber wireless solutions at www.rdlcom.com