GB2598173A

GB2598173A - System and apparatus for monitoring underground railway tunnel

Info

Publication number: GB2598173A
Application number: GB2102173.8A
Authority: GB
Inventors: Wing Chan Ho; Chan Sum; Hang Tsang Yick; Chuen Mak Kwong
Original assignee: MTR Corp Ltd
Current assignee: MTR Corp Ltd
Priority date: 2020-02-18
Filing date: 2021-02-16
Publication date: 2022-02-23
Also published as: GB202102173D0

Abstract

A monitoring system comprises a sensor 10 in an underground railway tunnel 5, a leaky feeder cable 30 extending along part of the tunnel and a gateway 40. The sensor wirelessly transmits sensor data via a low power wide area network (LPWAN) radio frequency signal 20. The cable conveys the signal to the gateway, which transmits a message 50 based on the sensor data to a remote server. A point of interface (35,Fig.7) may connect the leaky feeder cable, gateway and a trunked radio system 80 (e.g. for police, fire service, emergency service or railway staff). The sensor may sense door status, temperature, humidity, vibration, wind speed, moisture, water level, voltage or a pump, fire panel or circuit breaker status, e.g. detecting an intruder or passenger. Alternatively, a leaky feeder cable extends between two locations along an underground railway tunnel wall, ceiling or floor and multiple sensors transmit data via LPWAN RF signals through the cable to one or both locations.

Description

SYSTEM AND APPARATUS FOR MONITORING UNDERGROUND RAILWAY TUNNEL FIELD

The present disclosure relates to a system and apparatus for monitoring an underground railway tunnel

BACKGROUND

In an underground railway system, when a man on track is reported, e.g. due to an intruder or passengers left behind in the case of detrainment, train operation is suspended on a whole section of track (e.g. between two stations) while a full check of the track is carried out. This can cause long delays, which are especially serious in peak hours of an underground railway system when there are trains scheduled every few minutes. However, in order to ensure safety it is necessary to ensure that no person is left on the track before service is restarted.

SUMMARY

A first aspect of the present disclosure provides a system for monitoring an underground railway tunnel comprising at least one sensor located in the underground railway tunnel and configured to wirelessly transmit sensor data via a low power wide area network (LPWAN) radio frequency signal; at least one gateway configured to receive the radio frequency signal from the at least one sensor and wirelessly transmit a message based on the sensor data to a remote server; and a leaky feeder cable for conveying the LPWAN radio frequency signal from the at least one sensor to the at least one gateway, the leaky feeder cable extending along at least a part of the underground railway tunnel.

A second aspect of the present disclosure provides an underground railway tunnel comprising a tunnel wall, a leaky feeder cable extending along a tunnel wall, ceiling or floor from a first location to a second location, a plurality of sensors located in the tunnel and configured to transmit sensor data via LPWAN radio frequency signals through the leaky cable to at least one of the first location and the second location.

A third aspect of the present disclosure provides an apparatus comprising a point of interface for connection to a leaky feeder cable which is to receive a LPWAN radio frequency signal comprising sensor data; an internet of things (loT) gateway comprising a first port to connect with the point of interface, a processor to generate a message based on the sensor data included in the LPWAN radio frequency signal and a second port which is to transmit the message based on the sensor data to a remote server In some examples, the at least one leaky feeder cable may be used by a trunked radio system for conveying railway staff or emergency services radio communications as well as for conveying LPWAN radio frequency signals from the at least one sensor to the at least one gateway. The leaky feeder cable may for example connect with a point of interface having a first interface for connection with the leaky feeder cable, a second interface for connection with the at least one gateway and a third interface for connection with the trunked radio system.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the present disclosure will be explained below with reference to the accompanying drawings, in which:-Fig. 1A shows an example of a system for monitoring an underground railway tunnel according

to the present disclosure;

Fig. 1B shows another example of a system for monitoring an underground railway tunnel according to the present disclosure; Fig. 2 shows an example of a leaky feeder cable which may be used in examples of the present

disclosure;

Fig. 3 shows another example of a system for monitoring an underground railway tunnel according to the present disclosure; Fig. 4 shows an example method of monitoring an underground railway tunnel according to the present disclosure; Fig. 5 shows another example of a system for monitoring an underground railway tunnel according

to the present disclosure;

Fig. 6 shows another example of a system for monitoring an underground railway tunnel according to the present disclosure; Fig. 7 shows an example of a point of interface connected to a leaky feeder cable and a gateway

according to the present disclosure;

Fig. 8 shows another example of a system for monitoring an underground railway tunnel according to the present disclosure; Fig. 9 shows an example display for monitoring an underground railway tunnel according to the present disclosure; Fig. 10 shows an example of an apparatus including a gateway according to the present

disclosure; and

Fig. 11 shows an example of a server for monitoring an underground railway tunnel according to the present disclosure.

DETAILED DESCRIPTION

Various examples of the disclosure are discussed below. While specific implementations are discussed, it should be understood that this is done for illustrative purposes and variations with other components and configurations may be used without departing from the scope of the disclosure as defined by appended claims. In this disclosure the term "a number of a particular item should be interpreted as meaning one or more of said items.

The present disclosure proposes deploying a number of sensors in an underground railway tunnel.

The sensors are configured to wirelessly transmit sensor data via a low power wide area network (LPWAN) radio frequency (RE) signal. The LPWAN radio frequency signal is to be received by a gateway, which may transmit a message based on the sensor data to a remote server, which may be a physical or virtual server or a server provided by a cloud computing service.

LPWAN is a type of wireless telecommunication wide area network that is designed to allow long range, low bit rate communications by battery powered objects such as sensors. Examples of LPWAN protocols include LoRa, Sigfox and NB-lot. LPWAN differs from conventional telecommunication networks and from wifi (e.g. 802.11 protocols), in that LPWAN uses simplified, low overhead protocols which reduce hardware costs, processing demands and power consumption. LPWAN differs from radio frequency identification (RFID), in that LPWAN is able to transmit a larger variety and/or larger volumes of data and conduct two way communications, whereas RFID is generally for transmitting an identifier only or very limited data in one direction from the RFID tag to the reader.

A gateway is a device linking two different networks and in this case links a tunnel network to an external network, such as an Ethernet network or a telecommunications network which may reach the remote server. In this context the term tunnel network refers to the communication link whereby the plurality of wireless sensors are able to forward messages to the gateway via the leaky feeder cable.

In this way the tunnel environment can be monitored by the sensors and communicated to a railway operator or automated control system. There are many Internet of Things (loT) type sensors on the market and loT gateways for transmitting their signals to a server and use of such sensors could provide real time information about the tunnel, improve safety and facilitate remote monitoring of the underground railway.

However, underground railway tunnels are difficult environments for radio frequency signals, as there can be many reflections due to the relatively narrow nature of the tunnel (e.g. 3-5m wide), Further, compared to other types of tunnel, underground railway tunnels are relatively long. While an underground railway tunnel may be as short as 400m, 700m or more is common and some tunnels are as long as 1000m or 1400m between stations. Therefore transmitting a radio frequency signal over air all the way down the tunnel may consume a significant amount of energy and/or result in unreliable signal transmission.

Accordingly, the present disclosure proposes utilising a leaky feeder cable for conveying the first radio frequency signal from the sensor to a gateway. A leaky feeder cable is a cable which emits and receives radio waves as well as conveying radio waves along the cable. A leaky feeder cable may comprise an inner conductor, an insulating layer surrounding the inner conductor and an outer conductor surrounding the insulating layer, wherein there are gaps or slots in the outer conductor to allow the radio signal to leak into or out of the cable along the length of the cable. Leaky feeder cables are sometimes referred to as radiating cables.

The use of a leaky feeder cable may save energy and improve transmission compared to relying on transmission by air The leaky feeder cable may also extend the distance between gateways as the LPWAN RF signal can travel further This may make it possible to use battery powered sensors, as while the transmission may be frequent the energy required is reduced. Battery powered sensors are more flexible to deploy as they do not require power cabling to a mains source. Further, unlike for example Ethernet cables, a leaky feeder cable is able receive a radio frequency signal without having a direct physical connection to the source of the radio frequency signal.

Many underground railways already have leaky feeder cables installed for use by a trunked transmission radio system. A trunked transmission radio system is a radio system which uses a digital control channel to automatically assign frequency channels to groups of users. The trunked radio system may be used for communications by emergency services, such as police or fire, or by staff of the railway system. Using existing leaky feeder cables for conveying the sensor RE signals, avoids laying a new set of dedicated cables for the sensor system, which would be expensive and might require tunnel closure for an extended period while the cables were installed.

In some examples the LPWAN radio frequency signal transmitted by the at least one sensor occupies a frequency band within the range 900 MHz to 930 MHz. This frequency band has been found to reliably transmit signals in the challenging underground railway tunnel environment and in tests has successfully transmitted over existing leaky feeder cables installed for use by a trunked transmission radio system, without interfering with the trunked transmission radio system.

Fig. 1A shows an example of a system 1 for monitoring an underground railway tunnel according to the present disclosure. The system comprises at least one sensor 10 located in the underground railway tunnel 5, a gateway 40 and a leaky feeder cable 30 extending along at least a part of the tunnel.

The at least one sensor 10 is configured to wirelessly transmit sensor data via a LPWAN radio frequency (SF) signal 20. The LPWAN SF signal 20 is picked up by the leaky feeder cable 30 and conveyed by the leaky feeder cable to the gateway 40. The gateway 40 is configured to receive the LPWAN RF signal 20 from the sensor 10 and transmit a message based on the sensor data to a remote server.

The gateway 40 may be configured to transmit the message based on the sensor data to a remote server via a wired or wireless interface of the gateway. For example the message may be transmitted to the remote server over any one or a combination of the following: a local area network (LAN), metropolitan area network (MAN), fiber optic cable, a wide area network (WAN), a wireless local area network (WLAN), an Intranet, the Internet, a virtual private network (VPN), an access point name (APN) channel over a public network, a wired or wireless telecommunication network etc. In Fig. 1A the gateway is depicted as transmitting the message over a wireless link via a second RE signal 50.

Fig. 1B is similar to Fig. lA and like reference numerals denote like parts. Fig. 1B differs from Fig. 1A in that the gateway is configured to forward the message including the sensor data over a wired link, such as an Ethernet cable, rather than wirelessly transmitting the message in a second SF signal. Thus the gateway 40 of Fig. 1B links the at least one sensor in the tunnel to a wired network 55, while the gateway 40 of Fig. 1B links the at least one sensor in the tunnel network to a wireless network.

An example of a leaky feeder cable 200 is shown in Fig. 2. The leaky feeder cable 200 may comprise an inner conductor 210, an insulating layer 220 surrounding the inner conductor and an outer conductor 250 surrounding the insulating layer. In this respect it is similar to a co-axial cable. However, there are gaps or slots 235 in the outer conductor 230 which enable radio frequency signals to leak into and out of the leaky feeder cable. The gaps or slots 235 in the outer conductor 230 may be regularly spaced along the length of the leaky feeder cable. The outer conductor 230 may be surrounded by a protective sheaf 240. The protective sheaf may be relatively permeable to electromagnetic fields so to allow SF signals to leak into and out of the leaky feeder cable.

The inner and outer conductor may be formed of any suitable conducting material, for example copper, copper plated steel, a silver plated metal or another conductive metal. The insulating layer may be formed of an electrically insulating dielectric, such as but not limited to polyethylene or Teflon. The sheaf may be formed of a plastic.

Fig 3 is similar to Figs. 1A and 13, but in addition shows a remote server 70 which the gateway 40 communicates with over a network 60. The network 60 may for example be any one or a combination of the following: a local area network (LAN), metropolitan area network (MAN), wide area network (WAN), a wireless local area network (WLAN), an Intranet, the Internet, a virtual private network (VPN), an access point name (APN) channel over a public network, a wired or wireless telecommunication network etc. The remote server 70 is configured for receiving a message based on the sensor data from the at least one gateway. The remote server 70 may be a physical server, a virtual server or a server provided by a cloud computing service. The remote server may be configured to at least one of: display a status of the sensor(s), generate an alert in response to the sensor data of a sensor meeting an alert condition or send a control message to the at least one sensor via the at least one gateway.

In one example, the sensors are door status sensors and the remote server is configured to display a status of doors in the underground railway tunnel and generate an alert in response to a door being open. For example, there may be emergency exit doors at a side of tunnel between stations and a door sensor may detect when these doors are opened.

Fig. 9 shows an example display for monitoring the tunnel generated by the remote server The display 1300 shows a first tunnel 1305, a second tunnel 1306 and sensors 1310, 1312, 1320, 1322 located in the first and second underground railway tunnels. The display may indicate an alert at a sensor, e.g. by flashing the sensor, as shown for sensor 1320 in Fig. 13.

Fig. 4 shows a method 400 of monitoring an underground railway tunnel according to the present disclosure. The method may be employed by any of the systems described in this disclosure.

At block 410 a sensor senses an environment of the sensor and generates sensor data based on the sensed environment.

For example the sensor may sense the status of a door, pump (e.g.a sump pump), fire panel or circuit breaker, temperature, humidity, vibration, wind speed or another parameter of the environment and generate sensor data accordingly.

At block 420 the sensor wirelessly transmits the sensor data using a LPWAN radio frequency signal. For example, the sensor may transmit the sensor data wirelessly using a protocol such as but not limited to LoRa, Signet and NB-lot. In some examples, the LPWAN radio frequency signal transmitted by the sensor occupies a frequency band within the range 900 MHz to 930 MHz.

At block 430 the LPWAN radio frequency signal from the sensor feeds into a leaky feeder cable and is conveyed by the leaky feeder cable toward a gateway.

At block 440 the gateway receives the LPWAN radio frequency signal including the sensor data and sends a message based on the sensor data to a remote server. Maybe wired or wireless transmission In some examples the gateway transmits the message based on the sensor data wirelessly using a second RF signal, while in other examples the gateway transmits the message based on the sensor data over a wired connection.

Fig. 5 shows an example system including a plurality of sensors 10A, 10B, 10C at different locations in the tunnel 5 as well as the leaky feeder cable 30 and gateway 40 for forwarding messages based on the sensor data to a remote server. The sensors may be mounted to a wall, ceiling or floor of the tunnel or to an object such as a door located in the tunnel. Each of the sensors 10A, 10B, 100 generates sensor data based on the environment of the sensor and transmits the sensor data using a respective LPWAN RF signal 20A, 20B, 200. The gateway 40 may be configured to consolidate sensor data from a plurality of sensors prior to transmitting the sensor data to the remote server.

There may be many different types of sensor in the tunnel. A non-exhaustive list of sensor types includes: a door status sensor, a temperature sensor, humidity sensor, vibration sensor, moisture sensor, water level sensor, voltage sensor, wind speed sensor, pump status sensor, fire panel status sensor, or a circuit breaker on/off status sensor. The sensor data from each sensor includes a sensor ID identifying the sensor and a sensor value indicative of the environment sensed by the sensor (e.g. the door status, temperature, humidity, vibration, moisture, water level, voltage, wind speed, pump status, fire panel status, circuit breaker status etc). In some examples each tunnel may have a hundred or more sensors. For example a tunnel may have 350 sensor or more. In one example 300-1000 sensors are located in the tunnel and configured to transmit LPWAN RF signals including sensor data which feed into the leaky feeder cable for transmission to the gateway.

The leaky feeder cable 30 may be at least 200m long. In some examples the leaky feeder cable is at least 400m or at least 700m long. In one example the leaky feeder cable is 400-1400m long.

The gateway 40 may have a wired connection to the leaky feeder cable 30. This applies to Figs. 1A, 2A and 3-5 described above, as well as the further examples described with reference to other figures below. This may help to ensure good reception of the LPWAN RF signal by the gateway, especially where the length of the leaky feeder cable is relatively long. The wired connection may be a direction connection, e.g. via a physical port of the gateway, or an indirect wired connection by one or more intermediate devices.

In other examples, the gateway 40 may wirelessly receive the LPWAN RF signal from the leaky feeder cable, without a wired connection between the gateway and the leaky feeder cable. However, that approach may lead to a weaker signal. If a wireless approach is used, then an antenna and/or a booster amplifier may be connected to the leaky feeder cable to enhance the signal transmitted from an end of the leaky feeder cable to the gateway.

The tunnel may extend between two end points, such as two underground railway stations at which passengers may board or alight from a train. In some examples, the gateway 40 may be positioned near an end of the tunnel 5. For example the gateway may be located outside of the tunnel, for example in a station, or within the tunnel at point near, e.g. within a few meters of, the end of the tunnel. As the gateway 40 is positioned near an end of the tunnel, rather than deep within the tunnel, it may more easily connect to a network from which the remote server can be reached. For example, the gateway 40 may be within the service area of a wireless telecommunication network or easily connected to a wired network without laying large amounts of connecting cables.

The leaky feeder cable 30 may extend along a tunnel wall, ceiling or floor along at least part of the tunnel from a first location to a second location. The first location may for example be near a first end of the tunnel and the second location may for example be near the second end of the tunnel. A plurality of sensors may be located in the tunnel and configured to transmit sensor data via radio frequency signals through the leaky cable to at least one of the first location and the second location Fig. 6 shows an example in which the system includes a first gateway 40A and a second gateway 40B. For example, the first gateway may be located at a first location near a first end of the tunnel and the second gateway may be located at a second location near a second end of the tunnel. The leaky feeder cable 30 is arranged to convey the sensor data via the LPWAN radio frequency signal to both the first gateway 40A and the second gateway 40B.

The use of two gateways, e.g. one at each end of the tunnel, provides a degree of redundancy as if one of the gateways fails then the other gateway may still be operational and able to receive LPWAN RF signals from the sensor(s). The sensors may be used to detect people in the tunnel, indicators of people being present such as door status and other critical and time sensitive information. As trains travel regularly at high speed between stations, missing sensor data for even a short period of time may have serious consequences. The use of two gateways helps to prevent this from happening.

The sensor(s) may be configured to transmit a heartbeat signal to the gateway or gateways. A heartbeat signal is a signal which indicates that the sensor is alive' and still active. The heart beat signal may be generated by the sensor and sent to the gateway at regular intervals, or gateway may send heartbeat signals at regular intervals to the sensor(s) and await a response from the sensor If the gateway does not receive a heartbeat signal as expected this may indicate that the sensor has failed or a battery of the sensor has run out.

In some examples the heartbeat signal may have a regular interval of between 80 seconds and 160 seconds. In other examples the heartbeat signal may have a regular interval of between 110 seconds and 130 seconds. Longer heartbeat signals, e.g. hourly, would be too infrequent in the context of a sensor in an underground railway tunnel, as trains may pass between stations within a few minutes and so undetected failure of a sensor for even a short time may cause serious safety issues. However, having very frequent heartbeat signals may run down a battery of the sensor, or may overload the bandwidth of the leaky feeder cable or the gateway if there are a large number of sensors.

In some examples, the heartbeat signals are a simple indication that the sensor is still alive, while in other examples the heartbeat signals may include further information about the sensor The heartbeat signals may be separate from the signals including the sensor data, so that sensor data may be sent whenever a change in status is detected, rather than waiting for the next heartbeat signal, in order that the remote server has a real time or close to real time sensor status.

Fig. 7 shows an example of a point of interface 35 between the leaky feeder cable 30 and the at least one gateway 40. A point of interface is a physical interface between two different carriers, in this case the leaky cable 30 in the tunnel and an external network. The point of interface 35 may be a device with a plurality of physical interfaces. The point of interface 35 includes at least a first interface 35A for connecting with the leaky feeder cable 30, a second interface 35B for connecting with the gateway 40 and a third interface 35C for connecting with another radio system 80 which is separate from the gateway. The heartbeat signals may occupy a same frequency bandwidth as the LPWAN RF signals which communicate the sensor data.

The another radio system 80 may for example be a radio system for conveying police radio, fire service radio, emergency services radio or railway staff radio. The another radio system 80 may for example be a trunked radio system. For example, the another radio system 80 may for instance be a trunked radio system which is configured to transmit another radio frequency signal through the tunnel via the leaky feeder cable. The another radio frequency signal may for example be a signal conveying emergency service or railway staff communications. In some examples the another radio frequency signal may occupy a different band of frequencies to the LPWAN radio frequency signals from the sensor(s). In one example the another radio frequency signals occupy one or more frequency bands around 400 to 430 MHz or 800 to 830 MHz.

The sensor data sent to the gateway by the sensors may be encrypted. The gateway may be configured to transmit the sensor data to the remote server over an encrypted channel. In one example the encrypted channel is a Private Access Point Name (Private APN) channel. The gateway may send control signals or other messages back to the sensor via radio frequency signals over the leaky feeder cable. Such control signals and any other messages sent to the sensor may be encrypted. The control signals, other messages and any heartbeat signals may operate over the frequency used by the LPWAN radio signals.

Fig. 8 shows an example in which the leaky feeder cable 30 extends along at least a part of a first side of the tunnel and a second leaky cable 30A extends in the same direction along at least a part of a second side of the tunnel. In this way the first leaky cable 30 is to receive LPWAN radio frequency signals from sensors 10A, 10B, 100 on the first side of the tunnel and the second leaky cable 30A is to receive LPWAN radio frequency signals from sensors 10D, 10E, 1OF on the second side of the tunnel.

Fig 10 is a schematic diagram of an apparatus including an internet of things (loT) gateway 40 and a point of interface 35.

A point of interface is a physical interface between two different carriers. The point of interface 35 is for connection to a leaky feeder cable 30 which is to receive a LPWAN radio frequency signal comprising sensor data.

An loT gateway is a gateway which is capable of receiving messages from a plurality of sensors over a first network and forwarding the messages over another network. In this context the term network includes the communication link whereby the plurality of wireless sensors are able to forward messages to the gateway via a leaky feeder cable.

The loT gateway 40 includes a first port 41, a second port 42 and a processor 43. The first port 41 is to connect with the point of interface 35. Thus the first port 41 may receive RE LPWAN signals 20 from and/or send RF LPWAN signals to one or more sensors via the point of interface 35 The processor 43 is configured to generate a message based on sensor data included in the LPWAN radio frequency signal 20 received at the first port 41 and forward the message to a remote server via the second port 42. In the example of Fig. 10 the second port 42 is a wireless communication interface which is to wirelessly transmit the message based on the sensor data over a second radio frequency signal 50 to a remote server In other examples the second interface 42 may be a wired interface, such as a local area network (LAN), metropolitan area network (MAN), Ethernet or fibre optic interface etc In some examples, the point of interface 35 may include a first interface connected to the leaky feeder cable, a second interface connected to the gateway hardware and a third interface for connection to a trunked radio system, e.g. as shown in Figs. 7 and 8.

Fig. 11 shows an example of a server 70 for monitoring an underground railway tunnel according to the present disclosure. The server may for example be a remote server as described in any of the above examples. The server 70 includes a communication interface for receiving a message from a gateway which is based on sensor data received by the gateway. The communication interface 72 may be a wired interface or a wireless interface. In one example the interface is a LAN or WAN interface for communicating over a LAN or WAN network. In other examples the communication interface 72 may be connected to a wireless router, such as a 3G, 4G or LTE router or a WLAN router, for receiving wireless communications.

The server 70 further comprises a processor 74 and a non-transitory storage medium storing machine readable instructions which are executable by the processor. The instructions may include instructions 76A to receive sensor data which has been sent by a gateway that receives sensor data from the sensors. The instructions may include instructions 76B to display the sensor data, e.g. as shown in the example of Fig. 9 or otherwise, and/or to generate an alert based on the sensor data. For example if the sensor data meets an alert condition indicating possible intruders or detrained passengers in the tunnel, abnormal environmental conditions or abnormal status of a device being monitored by a sensor, then an alert may be generated. The alert may for example be an audio alert, textual alert or a visual alert on a display.

It is to be understood that any feature described in relation to any one example may be used alone, or in combination with other features described, and may also be used in combination with any features of any other of the examples, or any combination of any other of the examples.

Claims

CLAIMS1. A system for monitoring an underground railway tunnel comprising: at least one sensor located in the underground railway tunnel and configured to wirelessly transmit sensor data via a low power wide area network (LPWAN) radio frequency signal; at least one gateway configured to receive the LPWAN radio frequency signal from the at least one sensor and transmit a message based on the sensor data to a remote server; and a leaky feeder cable for conveying the first radio frequency signal from the at least one sensor to the at least one gateway, the leaky feeder cable extending along at least a part of the underground railway tunnel.
2. The system of claim 1 wherein the LPWAN radio frequency signal occupies a frequency band within the range 900 MHz to 930 MHz.
3. The system of claim 1 or 2 wherein the at least one gateway is configured to wirelessly transmit the message based on the sensor data to the remote server via a second radio frequency signal.
4. The system of any one of the above claims wherein the at least one gateway has a wired connection to the leaky feeder cable.
5. The system of any of the above claims wherein the leaky feeder cable is at least 200 meters long.
6 The system of any of the above claims wherein the sensor data includes a sensor ID and a sensor value.
7. The system of any one of the above claims wherein the gateway is configured to wirelessly transmit the message via a second radio frequency signal.
8. The system of any one of the above claims wherein the at least one gateway includes a first gateway and a second gateway, the leaky feeder cable being arranged to convey the sensor data via the LPWAN radio frequency signal to both the first gateway and the second gateway.
9. The system of claim 8 wherein the first gateway is located near a first end of the tunnel and the second gateway is located near a second end of the tunnel.
10. The system of any of the above claims wherein the sensor is configured to transmit a heartbeat signal to the at least one gateway.
11. The system of claim 10 wherein the heartbeat signal has an interval of between 80 seconds and 160 seconds.
12. The system of claim 10 wherein the heartbeat signal has an interval of between 110 seconds and 130 seconds.
13. The system of any one of the above claims wherein a point of interface between the leaky feeder cable and the at least one gateway includes at least a first interface for connecting with leaky feeder cable, a second interface for connecting with the gateway and a third interface for connecting with another radio system which is separate from the gateway.
14. The system of claim 13 wherein the another radio system is a trunked radio system for conveying police radio, fire service radio, emergency services radio or railway staff radio.
15. The system of any one of the above claims comprising a trunked radio system which is configured to transmit a third radio frequency signal through the tunnel via the leaky feeder cable.
16. The system of any one of the above claims wherein the at least one gateway is configured to transmit the message based on the sensor data to the remote server over an encrypted channel.
17. The system of any one of the above claims comprising a plurality of sensors at different locations in the tunnel.
18. The system of claim 17 wherein the gateway is configured to consolidate sensor data from the plurality of sensors prior to transmitting the sensor data to the remote server.
19. The system of any one of the above claims wherein the sensor is one of: a door status sensor, a temperature sensor, humidity sensor, vibration sensor, wind speed sensor, moisture sensor, water level sensor, voltage sensor, pump status sensor, fire panel status sensor, or a circuit breaker on/off status sensor
20. The system of any one of the above claims wherein the leaky feeder cable extends along at least a part of a first side of the tunnel and a second leaky feeder cable extends in the same direction along at least a part of a second side of the tunnel, whereby the first leaky feeder cable is to receive LPWAN radio frequency signals from sensors on the first side of the tunnel and the second leaky feeder cable is to receive LPWAN radio frequency signals from sensors on the second side of the tunnel.
21. The system of any one of the above claims further comprising a remote server for receiving the message based on the sensor data from the at least one gateway, the remote server configured to at least one of: display a status of the at least one sensor, generate an alert in response to the sensor data meeting an alert condition or send a control message to the at least one sensor via the at least one gateway.
22. An underground railway tunnel comprising a tunnel wall, a leaky feeder cable extending along a tunnel wall, ceiling or floor from a first location to a second location, a plurality of sensors located in the tunnel and configured to transmit sensor data via low power wide area network (LPWAN) radio frequency signals through the leaky cable to at least one of the first location and the second location.
23. The underground railway tunnel of claim 22 comprising a first gateway at the first location and a second gateway at the second location.
24. An apparatus comprising: a point of interface for connection to a leaky feeder cable which is to receive a low power wide area network (LPWAN) radio frequency signal comprising sensor data; an internet of things (loT) gateway comprising a first port to connect with the point of interface, a processor to generate a message based on the sensor data included in the LPWAN radio frequency signal and a second port which is to transmit a message based on the sensor data to a remote server
25. The apparatus claim 24 wherein the gateway is configured to receive a LPWAN radio frequency signal which uses a protocol selected from the group comprising LoRa, Sigfox and NB-lot.
26. The apparatus of claim 24 or 25 wherein the point of interface includes a first interface connected to the leaky feeder cable, a second interface connected to the loT gateway and a third interface for connection to a trunked radio system.