A Graceful Transition: How Kinetic Mesh Eliminates the Handover for Mass Transit Operators

Modern technology has proven invaluable to helping train systems become safer and more reliable with the use of tools such as cameras, sensors and handheld devices. These technologies can provide valuable insights into passenger behavior; vehicle and equipment health; exact speeds and locations; fuel consumption; traffic; security concerns and more. Having the right communications network is vital to ensuring all of these moving assets can be simultaneously connected and that the data being transmitted and received is up-to-the-second current.

Initially, most operators deployed cellular solutions because they were the path of least resistance, and in terms of collecting small sensor data, they sufficed. In terms of supporting customer-facing applications like surveillance and passenger Wi-Fi, however, they did not.

Since then, network demands have predictably grown. Wi-Fi access is no longer a novelty to be appreciated but an expectation to meet if commuters are to be retained. In parallel, smart transit tools have proliferated, further driving the need for real-time high-speed networks. 4G networks are still only a half-measure answer of convenience and simply cannot be relied upon in the event of an emergency.

To ensure successful mass transit communications, there are four vital attributes a network should have.

The Four Components of a Mass Transit Broadband Network

• A constant high-speed connectivity to the trains. This is easier said than done, as trains are constantly on the move through congested urban environments. Trackside-to-train communications should be constant, robust and able to deal with radio frequency interference and line-of-sight issues. As operators implement train control solutions to safely increase capacity, these networks must also be fully redundant and ultra-secure.
• A high-capacity distribution of connectivity between train cars. Once a steady high-speed “pipe” is established to the train, it can be challenging to make this capacity available to every car in the train consist, as the last car may have access to significantly less bandwidth than a car closer to where the signal originates. Many cabled solutions suffer from the rigors of moving cars in and out every day, while wireless solutions suffer from drastically reduced capacity every time they hop to the next car.
• Cellular and wayside aggregation and load balancing. Transit operators may want to take a phased approach to building a trackside broadband infrastructure, or they may always choose to use cellular for some applications, especially in areas further from their urban center. In this case, the network will need to smartly and seamlessly toggle back and forth between using trackside where it exists and cellular where it does not.
• Onboard Wi-Fi. The most obvious application for this is to enhance passenger experience; riders are beginning to expect access to Wi-Fi wherever they go, and trains are no different. Trains with Wi-Fi can be a good way to recruit and retain riders who want to work or browse the Internet during their train trips. Additionally, a network is needed for smart devices such as fare collectors or to connect staff.

Challenges with a Communications Network: The Handover

When discussing a trackside-to-train network, the biggest two questions to address are how far apart the trackside radios can be separated, and how fast the handover is from one radio to the next as the train passes by them. The answer to the former, as is always the case with wireless, is that it depends. The answer to the latter is much more interesting.

Handover is language of fixed backhaul technology applied to a mobile network application. As a train moves along the track, it loses connectivity from a radio farther behind it and gains connectivity from the radio it is approaching, so the train is constantly making a decision whether to hop off one radio and move to the next, and is always negotiating the connection between radios to determine where the best signal is.

This is roughly analogous to someone talking on a cell phone while driving; as the car and passenger move, the cell phone signal emanating from the phone must jump from tower to tower to maintain full connectivity. If there is too great a distance between towers or signals are too weak, the connection is lost and the call will drop.

In a properly designed trackside network, whether the radios make the new connection before breaking the other or vice versa, the handover usually ranges anywhere between 1 and 50 milliseconds. While this is fast and is usually acceptable, the whole concept of handover only addresses the trackside-to-train component of the overall network, and even then still introduces critical limitations.

One technology that mass transit operators are considering that would ensure constant connectivity without handover is Kinetic Mesh wireless.

Kinetic Mesh and Elimination of the Handover

In a Kinetic Mesh network — a type of wireless network that is truly mobile — a different “make, make, make and never break” approach establishes and maintains connections with every node it sees. This goes further than simply ensuring there is never a break in connectivity as the train moves down the tracks; it also provides full, immediate redundancy and offers the opportunity for aggregate throughput from multiple trackside radios.
It also helps answer the question on how far apart trackside radios should be installed. Because handover technology is always sharing a link over and over and does not maintain multiple connections, its only goal is to spread trackside radios out as far apart as possible. This eliminates two important possibilities.

First, it doesn’t fully leverage fiber, which is often installed on the trackside, whereas Kinetic Mesh maintains multiple connections and, in many cases, aggregates those connections, providing a greater return on the fiber network. Second, spreading radios as far apart as possible requires taller and more expensive infrastructure, which increases the cost of a transit construction project. Kinetic Mesh is more conducive to smaller poles that, even if more are required, can be significantly less expensive, may already exist and are operationally easier to accomplish.

Kinetic mesh wireless nodes require no controllers, pre-planned routing protocols or base station neighbor lists. Each one works autonomously to deliver traffic via the best available path on a packet-by-packet basis. If one path becomes unavailable for any reason – such as interference or power loss — the network routes around it. Every node can make a fully independent decision, and it is not uncommon for a node to have several dozenpeer connections, giving it the ability to use any link at any time.

Using Kinetic Mesh as a communications network for transit means the network is always connected; the train’s network connection does not need to hop down the track from radio to radio and be handed over every time.

Other Benefits of Kinetic Mesh for Mass Transit

Kinetic Mesh has other benefits for mass transit operators as well. It enables simultaneous car-to-car and train-to-trackside continuity, increasing overall network redundancy and ensuring continuous functioning of applications such as onboard CCTV, passenger information systems, digital advertising and automated ticketing. Bandwidth capacity remains high across the entire train while maintaining very low latency.

Kinetic Mesh can also facilitate cellular and wayside aggregation and load balancing; traditional communication control units require add-ons from third parties to handle this balancing act. This helps enable applications such as fuel management; equipment sensor monitoring; speed and location tracking; onboard Wi-Fi for passengers; traffic optimization; and safety and security.

Some challenges for mass transit, like ensuring passenger safety and security, will never — and should never — stop being concerns for operators. Others can be solved with technology. A handover is simply the inherent limitation of a fixed technology, and may eventually be so far in mass transit’s past that it will seem comparable to the omnibuses of the 19th century. With new technologies constantly evolving and becoming accessible, mass transit operators will be well prepared to meet current and future challenges and provide smooth service.

Kevin Fitzgibbons is director of business development for Rajant.