WiFi on Trains: Architectures, Advantages, and Technologies

This article explores different WiFi network designs used to deliver internet service onboard trains. It highlights the advantages of WiFi on trains, detailing how WiFi rail architectures function for moving trains, covered metro stations, and rail tunnels. The article also mentions providers or vendors of Wi-Fi on rail products and solutions.

Introduction

WiFi has become ubiquitous globally, enabling us to connect our smart devices to the internet wirelessly. It operates using electromagnetic radio waves at frequencies like 2.4 GHz, 5 GHz, and 6 GHz, depending on the WLAN chip support. Various WLAN standards have been developed to enhance data rates and coverage.

WLAN adheres to IEEE standards such as 802.11b, 11a, 11g, 11n, 11ac, 11ax, and 802.11be. WiFi networks are typically used for high data rates within a limited coverage area, primarily supporting devices inside buildings, offices, railway stations, airports, and trains. Initially, WLAN standards were designed for lower mobility devices. However, IEEE 802.11ax supports higher mobility, enabling internet access in vehicles using WiFi hotspots.

Cellular technologies, which follow 3GPP or ETSI standards, are mainly designed for outdoor use with high-speed moving vehicles. Cellular standards include 2G (GSM), 3G (UMTS or CDMA), 4G (WiMAX, LTE), and 5G NR (New Radio).

WiFi service is provided by installing an 802.11 Access Point (AP), also known as a WiFi Router. Cellular service is provided by installing cell towers with a backbone infrastructure for PSTN/PSDN interfacing. Satellite networks offer connectivity in remote areas where cellular towers are unavailable or impractical, providing wider Earth coverage due to their high altitude. Specific cellular standards have been developed for railways, including GSM-R and LTE-R.

The following table compares the main features of WiFi and cellular standards (GSM-R, LTE-R, and 5G NR).

Table-1 Comparison of WiFi and Cellular technologies

Different bands are used in satellite communication networks, including L band (1-2 GHz), C band (3700-4200 MHz downlink, 5925-6425 MHz uplink), Extended-C band, Ku band (11.7-12.7 GHz downlink, 14-14.7 GHz uplink), and Ka band (18.8-19.3 GHz downlink, 28.6-29.10 GHz uplink). Satellite transponder bandwidths are commonly 36 MHz and 72 MHz, used for multiple voice/data calls by ground station users based on various multiple access techniques.

WiFi Network Architecture at Home

A typical home WiFi system includes a WiFi router connected to an Internet Service Provider (ISP) on one side and WiFi Clients (stations) on the other. A cable modem or a suitable modem is usually required to interface with the WiFi router, depending on the technologies used by the ISP. Over the years, ISPs have used various technologies to provide internet service, including dial-up, ADSL/SDSL, cable internet, ISDN, Ethernet, fiber optic, satellite, WiFi, and cellular broadband.

Figure-1 WiFi network architecture at Home

A WiFi router allows multiple WiFi-compliant smart devices to share a single internet connection, enabling multiple users to use high-speed internet comfortably and affordably. WiFi routers also come with Ethernet ports, allowing desktop computers or laptops with 10/100/1000 Mbps LAN devices to be easily connected using Ethernet cables.

WiFi hotspots are installed using WiFi routers at shopping malls, railway stations, airports, and businesses to provide internet service to customers or passengers. These WiFi routers are connected to an ISP.

Wifi Network for Moving Train | How it Works

Internet access requires connectivity with an ISP through wired or wireless technologies. Wired technologies are not feasible for trains moving at higher or lower speeds. Therefore, cellular or satellite technologies are essential for providing internet connectivity to train passengers using electromagnetic waves.

Figure-2 WiFi architecture for on board trains

Each train compartment is equipped with one or multiple WiFi routers or APs. These APs are connected to a multi-port gigabit switch using Ethernet cables. A multimedia server is connected to the gigabit switch to configure and monitor all APs and the gateway. The WAN gateway provides connectivity between APs inside the train and the outside network (cellular or satellite). Gateways use specially designed rail antennas on the roof of the train. Multiple WAN gateways are installed in the trains based on user requirements.

MOXA Inc. offers solutions for onboard WiFi broadband access and seamless train-to-ground communications, as shown in the following table.

Table-2 MOXA Products

Fluidmesh Networks offers solutions for commercial rail and passenger rail systems, with products for intra-train solutions and train-to-ground communications. The company was acquired by Cisco in July 2020.

Table-3 WiFi Solutions for Train by Fluidmesh Networks

WiFi/Cellular Architecture for Covered Metro Stations and Rail Tunnels

Providing internet connectivity on trains within underground or covered metro stations, or in tunnels, poses a challenge. Several approaches can be used in these scenarios. Initially, repeater-based solutions were used in tunnels, where a series of repeaters are positioned between APs mounted on both ends of the rail tunnel. These WLAN APs are connected to a cellular tower available on the track side.

Figure-3 WiFi/Cellular architecture for covered metro stations and rail tunnels

Another approach under development uses the latest 5G NR cellular system. In this system, 5G NR RRUs and BBUs are connected using Optical Fiber Cables (OFCs) and Optical-to-RF and RF-to-Optical converters, as shown. Multiple WLAN APs are also installed inside the rail tunnels or Capsules in hyperloop technology, connected together using OFC.

Advantages of WiFi on Board Trains

Following are the generic benefits or advantages of WiFi on board trains:

• The WiFi service allows passengers to stay connected with friends and relatives during their journey.
• Business professionals can continue their work while traveling on trains.
• The service is often free, allowing passengers to pass the time by watching movies and listening to their favorite songs.
• Train accidents or minor faults can be easily reported from remote, hilly locations to controlling stations located miles away.
• The technology provides real-time train control.
• It facilitates safety related applications like CCTV streaming, door clearance, mission-critical voice communication, and passenger information systems.

Installing complete solutions on all trains can be very expensive. The benefits and drawbacks largely depend on the specific technologies used for providing internet service on the train. Readers can evaluate these based on different train-bound technologies, such as Ethernet, WiFi, cellular, and satellite.