Communications system used in underground mining and tunnel environments
A
leaky feeder
is a
communications
system used in
underground mining
and other tunnel environments.
[1]
Manufacturers and cabling professionals use the term "
radiating cable
"
[2]
[3]
[
better source needed
]
[4]
as this implies that the cable is designed to radiate: something that coaxial cable is not generally supposed to do.
Principle
[
edit
]
A
leaky feeder
communication system consists of a
cable
run along tunnels which emits and receives
radio waves
, functioning as an extended
antenna
. The cable is "leaky" in that it has gaps or slots in its outer conductor to allow the radio signal to leak into or out of the cable along its entire length. Because of this leakage of signal, line amplifiers are required to be inserted at regular intervals, typically every 350 to 500 metres, to boost the signal back up to acceptable levels. The signal is usually picked up by portable transceivers carried by personnel. Transmissions from the transceivers are picked up by the feeder and carried to other parts of the tunnel, allowing
two-way radio
communication throughout the tunnel system.
The system has a limited range and because of the frequency it uses (typically
VHF
or
UHF
), transmissions cannot pass through solid rock, which limits the system to a
line-of-sight
application. It does, however, allow two-way mobile communication.
Due to the signal loss along the feeder, a leaky feeder is usually used for frequencies under 1 GHz. Above that frequency the losses require too many repeaters, thus making other options more effective. Antennae (omni, panel or bi-directional) or even
distributed antenna systems
are more often used for higher frequency bands.
Applications
[
edit
]
Mining
[
edit
]
Leaky feeders are used in the mining industry as a method of wireless communication between miners. The system is used as a primary communication system which has a transceiver small enough to be comfortably worn on a miner throughout an entire shift.
[5]
Underground railways
[
edit
]
The leaky feeder system is used for underground mobile communication in
mass transit
railways
. In the
Delhi Metro
,
rail transport systems of Hong Kong
, and the
Copenhagen Metro
(Danish:
CityRingen
), leaky feeders were incorporated in the specification of the capital project and installed during construction.
[
citation needed
]
[
clarification needed
]
This gives emergency services seamless mobile communication from the underground to the surface.
London Underground
uses a leaky feeder system for its internal communication network
Connect
.
[6]
However, the communication used by the emergency services,
Airwave
, was not compatible and did not work below ground. The fact that this situation continued to exist after the 1987
King's Cross fire
was criticised in the reports from the
7 July 2005 London bombings
, where it hampered rescue efforts.
[7]
In March 2020, two additional leaky feeder cables were brought online in the Jubilee line tunnels between Canning Town and Westminster. One of these cables provided commercial 4G coverage for passengers, both in the tunnels and on station platforms,
[8]
whilst the second cable provided coverage for the Home Office's
Emergency Services Network
(ESN),
[9]
which is currently being rolled out to replace the ageing Airwave network.
[10]
This trial section is the first to be brought online as part of a project to provide both commercial 4G coverage and ESN coverage across the entire Tube network.
Tyne and Wear Metro was the first railway in the UK to use leaky feeder cables for public mobile phone connectivity, in its city-centre underground tunnels. Initially this was a 2G signal, but then mobile operator EE upgraded this to 4G for their customers. As of 2023, operator Nexus are planning a comprehensive upgrade to mobile data coverage, including in the tunnels.
[11]
An alternative to using leaky feeder in underground railways is to use
Distributed Antenna System
(DAS). A DAS system was deployed in some
New York City Subway
stations by
Transit Wireless
to provide
Wi?Fi
and mobile phone and data coverage for customers.
[12]
In-flight wireless networks
[
edit
]
Leaky feeder antenna system can also be used to allow use of on-board cellular phones and
Wi?Fi
on passenger aircraft.
[13]
[14]
The weight and space requirements of leaky feeder systems are usually lower than comparable antenna systems, thus saving space and fuel. The even field strengths produced by runs of leaky feeders spanning the entire fuselage improve coverage while requiring less transmitting power.
Industrial buildings
[
edit
]
Leaky feeders are used in hotels, warehouses and other industrial buildings where it is difficult to get Wi?Fi coverage using normal
access points
. Some installations have 50?75 meters of leaky wire connected to the antenna output of each access point.
[15]
RFID
[
edit
]
A leaky feeder modified with metallic strips can be used as a
radio-frequency identification
(RFID) antenna.
[16]
[17]
See also
[
edit
]
References
[
edit
]
- ^
"Improvements coming soon to mine communications"
.
Kentucky New Era
.
Associated Press
. 19 February 2007
. Retrieved
6 March
2012
.
- ^
"Times Microwave Radiating Cable Catalogue"
(PDF)
.
Times Microwave
. Retrieved
12 March
2017
.
- ^
"Radiating Cable"
.
CommScope
. Retrieved
13 September
2014
.
- ^
"Radiating cable revealed"
.
Radio Frequency Systems
. Archived from
the original
on 30 August 2017
. Retrieved
13 September
2014
.
- ^
"Basic Tutorial on Wireless Communication and Electronic Tracking: Technology Overview"
. Centers for Disease Control and Prevention
. Retrieved
8 March
2014
.
- ^
"Victoria line heads Metronet renewal"
.
Railway Gazette International
. 1 August 2003
. Retrieved
6 March
2012
.
- ^
"Communications blamed in London bomb response"
. PC Advisor. 23 February 2012
. Retrieved
6 March
2012
.
- ^
"4G on Jubilee line tunnel section from March 2020"
.
Transport for London
(Press release)
. Retrieved
2021-03-12
.
- ^
Kobie, Nicole (2020-02-05).
"Inside the messy mission to bring 4G to the London Underground"
.
Wired UK
.
ISSN
1357-0978
. Retrieved
2021-03-12
.
- ^
"Emergency Services Network: overview"
.
GOV.UK
. Retrieved
2021-03-12
.
- ^
https://www.nexus.org.uk/news/item/nexus-announces-plan-improve-digital-connectivity-tyne-and-wear-metro
- ^
Nally, Jonathan (30 September 2013).
"Tunnel vision: getting New York talking"
.
CriticcalComms
. Archived from
the original
on 1 October 2013
. Retrieved
8 March
2014
.
- ^
ETSI White Paper No. 4 GSM operation onboard aircraft
(PDF)
, January 2007
- ^
W. L. Gore & Associates
(15 October 2013),
"Leaky Feeder Antennas for Airborne Wi-Fi"
,
Microwave Journal
- ^
"Leaky Feeder Communication and Installation Guide for Business"
.
Wall to Wall Communications
. 11 February 2019
. Retrieved
12 March
2019
.
- ^
Putaala, Jussi; Myllymaki, Sami; Kokkonen, Mikko; Jantunen, Heli (July 2021).
"Resonator-enhanced radiating cable for UHF RFID readers"
(PDF)
.
Microwave and Optical Technology Letters
.
63
(7): 1842?1847.
doi
:
10.1002/mop.32844
.
S2CID
233392835
.
- ^
Kokkonen, Mikko; Myllymaki, Sami; Putaala, Jussi; Jantunen, Heli (2022).
"A Resonator Enhanced UHF RFID Antenna Cable for Inventory and Warehouse Applications"
.
IEEE Journal of Radio Frequency Identification
.
6
(1): 128?133.
Bibcode
:
2022IJRFI...6..128K
.
doi
:
10.1109/jrfid.2021.3135047
.
S2CID
245218056
.
External links
[
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]