In recent years, the widespread use of mobile devices for information and communication has changed passengers’ expectations about rail travel. In addition to expecting a comfortable journey, passengers are increasingly demanding Internet access and the ability to work onboard a train to make efficient use of their travel time. Beyond simple Internet access, railway operators have also begun to recognize that they can leverage onboard Wi-Fi networks to support a variety of operational and passenger infotainment applications. A digitally connected fleet enables real-time system status reporting and better information flow. These services increase operational efficiency, reduce costs, improve service quality, and improve customer satisfaction.

Five Keys to Successful High-Density Wi-Fi Deployment

Here are the top five factors to consider when choosing a Wi-Fi solution for high-density Wi-Fi deployments in industrial applications—beyond supporting the same standard features as a general-purpose access point (AP).

1. Reliability

An AP plays a central role in connecting passengers to the onboard Wi-Fi network on a train. Although many enterprise solutions already provide such connectivity, only a few can meet the requirements of rolling-stock operations. Access points that are suitable for use on trains must include the following characteristics:

.Wide operating temperature range
.Anti-vibration and anti-shock connector design
.Dual isolation protection (RF and power)
.Versatile power input

2. High Throughput

It is difficult to predict how much bandwidth each passenger needs to enjoy seamless network connectivity while travelling. Estimates are usually based on studies that consider user behavior and the bandwidth used by various onboard applications. In an average home or office, a data transfer speed of 50 to 100 Mbps is adequate to enable simultaneous Internet access for multiple devices. However, taking into account that passengers could have multiple devices and considering various factors that constrain AP throughput, one study has concluded that passengers are often left with only 2 to 3 Mbps bandwidth for their applications.

070_01_onboard_connection.jpg3. High-Density Connectivity

If a conventional wireless network is deployed in a high-density user environment, it is not hard to predict the result—poor user experience. This is more evident at live events and on trains where hundreds of users are trying to simultaneously access a Wi-Fi network. To provide a good user experience, one study recommends deploying one AP for every 60 users. For example, a train carriage that can seat 100 passengers will require at least two APs, with both 2.4 GHz and 5 GHz channels, each serving as many passengers as possible in different bands. If not enough APs are deployed, some passengers may experience poor connection quality.

4. Client-Load Balancing

When too many client devices try to connect to an AP, the bandwidth available for each client device decreases, eventually resulting in poor connectivity. With client-load balancing, railway operators can limit the number of client devices that can connect to an AP. When this limit is reached, the AP can deny any new connection requests, forcing client devices to connect to other APs, thereby sharing the available radio channels evenly among client devices in the area. Additionally, client-load balancing allows APs to prevent client devices from connecting to a congested channel, encouraging an even distribution of available bandwidth for all client devices.

5. Wireless Client Isolation

Railway operators must implement client isolation in a public Wi-Fi network to prevent client devices from communicating with one another; they should be allowed to only access the Internet. This serves two purposes: it increases network security and limits broadcast traffic. Every device that connects to onboard APs belongs to the same network, which includes onboard systems such as broadcast or other control systems. However, unlike a home network where one can freely access resources on different devices, passengers and train operators do not need to access each other’s devices. In fact, they do not want to share resources and information with others, especially on a public wireless network where the risk of a hacking attack is high.

070_02_onboard_connection.jpgImproving Onboard Wi-Fi for Passenger Satisfaction

Let us consider a typical use case of onboard Wi-Fi for train passengers to understand what it takes to provide a good user experience.

System Requirements

.Stable Wi-Fi connectivity
.Enough bandwidth for high-speed Internet access
.Built-in network intelligence that adapts to daily inter-car and inter-consist changes with ease
.Easy, flexible, and reliable routing across various locations and IP service carriers
.Operational reliability for device durability and network connectivity
.Compact size that fits the space-limited environments on trains

Moxa's Solution

Most passenger Wi-Fi systems are developed on a case-by-case basis and tailored to specific train-car conditions and requirements. It is essential to partner with companies that have extensive experience in satisfying custom application requirements by tailoring specific products and engineering services. The following diagram illustrates a passenger Wi-Fi solution that boosts network performance by providing multiple redundant WAN connections, a full-Gigabit backbone, and broadband Wi-Fi access. A variety of technologies are available to achieve network reliability, availability, and easy operation and maintenance while reducing deployment complexity.

070_03_onboard_connection.jpgThe design of a high-density Wi-Fi network is a complex process. By considering a number of important factors, such as network reliability, data rate, mixed mode client ratios, load balancing, and network security, railway operators can choose an effective Wi-Fi solution that meets the requirements of rolling-stock applications and ensures that their passengers have uninterrupted connections for enjoyable journeys. For additional details on how to implement passenger Wi-Fi, download our White Paper or visit our microsite.

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