Bench Talk

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Many municipalities are now using Wi-Fi^® and the internet in public transportation infrastructures to address the growing need to connect vehicles and passengers during transportation. Current connected vehicle technology requires that communications flow through a network of wireless radios that are installed within the vehicles and at fixed nodes along transportation routes. This network enables several different communication modes:

• Vehicle-to-vehicle (V2V): This connection can involve the transmission and reception of data such as location and speed among vehicles or the facilitation of secure communications. This information can be useful to aid in navigation, tracking, or collision avoidance.
   
• Vehicle-to-infrastructure (V2I): This interface involves the capture of vehicle-generated data (e.g., fuel consumption, speed, and position) and provides information throughout the network of vehicles to improve and coordinate travel schedules, enhance vehicle safety, aid in navigation or traffic avoidance, or communicate environment-related conditions (e.g., weather and road closures).  
   
• Machine-to-machine (M2M): This connection includes secure point-of-sale (POS) fare, toll and parking payments, or Wi-Fi access to phones, tablets, or computers that passengers may use to send and receive information, emails, text messages, news, and entertainment from the internet during their commutes.

Several challenges must be overcome to create a secure, reliable, and high-performing transit system Wi-Fi network. Such challenges include:

• Limited bandwidth: Public transportation vehicles by design carry numerous passengers, some of which may have multiple devices that require Wi-Fi connectivity. Systems with limited bandwidth may not have adequate capacity to service these large data demands, leading to slow response times and frustrated passengers.
   
• “Dirty power”: Systems that are not specifically designed for use on vehicles may experience Wi-Fi service interruptions due to variations in power, voltage, frequency, and surges that may disable the systems and lead to significant down times until the systems can receive service.
   
• Poor connectivity or limited range: Because transit system Wi-Fi networks must communicate through antennas via radio, the availability or strength of a signal is affected by the ability of the vehicle to communicate with the router. Numerous problems can limit Wi-Fi availability, including the number and strength of the transceivers and environmental factors, such as the presence of electromagnetic interference, which may cause drop-outs, dead zones, or weak signals.
   
• Ruggedization: Systems that are not designed for operation on moving vehicles may be subject to adverse environmental conditions that can lead to hardware failure. Some of these environments may include thermal loads, such as temperature extremes and cycling, and mechanical loads, such as exposure to shock and vibration.  
   
• Software: Centralized software is necessary to communicate with and control the performance of potentially numerous stationary and mobile nodes in the field. This software must be capable of communicating with several vehicles simultaneously and in real time.

The Digi International TransPort® WR64 Dual Cellular LTE-Advanced Router (Figure 1) features true enterprise-class routing, security, a firewall, and an integrated virtual private network (VPN), making it an ideal choice for challenging transportation and mobile environments.

Figure 1: The Digi International WR64 TransPort Router is available in a compact enclosure, suitable for rugged transportation and mobile environments. (Source: Digi International) 

Key features and capabilities of the Digi International TransPort® WR64 Dual Cellular LTE-Advanced Router include:

• Bandwidth: Bandwidth limitation issues are addressed using triple carrier aggregation on each cellular interface, which combined can deliver up to 1.2Gbps to passengers. Onboard systems retain priority and any remaining bandwidth is made available to internet traffic.
   
• Power: The system is designed with reliable powering circuitry that supports 9 to 36VDC input along with ignition sensing for direct integration into a vehicle’s power source. 
   
• Connectivity: As shown in the example application in Figure 2, the system segments private versus public data communications, enabling the secure management of internet access for passengers and without an impact on onboard bus systems.

Figure 2: The Digi Transport WR64 Router incorporates segmented private versus public data communications to facilitate the implementation of several different mobile transport applications. (Source: Digi International) 

• Ruggedization: The system uses an aluminum enclosure and is qualified to meet military and transportation standards for temperature, humidity, vibration, shock, and dust environments. Flexible mounting options permit installation of the router to minimize environmental loading.
   
• Software: The Digi Remote Manager (Figure 3) can manage and control devices from a central platform in real time. This software enables system administrators to visually monitor, update, and maintain numerous performance parameters throughout the network in a secure and reliable manner.

Figure 3: The Digi Remote Manager software provides a central platform to monitor system performance throughout the transportation system’s mobile Wi-Fi network. (Source: Digi International) 

The growing use of Wi-Fi and the internet in public transportation vehicles poses several unique challenges for the system hardware of these vehicles. The Digi International WR64 TransPort^® Router addresses these challenges and is now available from Mouser Electronics, a worldwide, leading, authorized distributor of semiconductors and electronic components for over 700 industry-leading manufacturers.