Network Convergence for Underground Mines - Varis Mine ...

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Network Convergence for Underground Mines

Author
s


Mr.
Matthew
R.
Ward, P.Eng., Varis



Ms. Anita Masuskapoe, Varis


Abstract

This paper
aims

to describe
the
reasons and methods

to extend
enterprise networks

into

underground

mines
.
Currently
mines use
a nu
mber of communication networks for telephones, PLCs,
two
-
way
VHF
radio and
computer
networking. Each system can have different
wiring,
protocols, converters and interfaces all which
require
expansion and maintenance
. The convergence of voice, video and dat
a using Ethernet and TCP/IP has
the very real benefit of one “wire” for
underground

networks.
Now

that

the majority of underground equipm
ent
can
communicate using

TCP/IP,
network
convergence can offer reduced network expansion and maintenance
costs.


Cost
savings are
good
, but the truly exciting aspect of
network
convergence

using Ethernet

is the low
-
cost, high
speed wireless networking
now available
.
These

wireless
network
s

offer an opportunity to facilitate mining
automation
even on a small

budget
.

How wo
uld mine
operators

change they way they operate if they
could
gather vehicle location and data in real time
?
What about

controlling equipment remotely
? The list
of
applications
is long and includes traffic control, dispatching, real
-
time ore blending, tele
-
operation
, automated
production reporting, vehicle health monitoring, elimination of paper forms and immediate network access for
surveyors and geologists.


An ideal
converged
network

for underground mining

would be
robust,
inexpensive, e
asy to expand,
en
able fast
and secure connections
while keeping v
oice communication performance equivalent
or better than

what

is
now
provided by VHF radio
.


Network Convergence


Ethernet


What could explain the fact that modern computers rely on a communication
network

developed in 1972?
Robert Metcalf
e

of Xerox was
looking for a way to share

printers, not define the way the world would
communicate for the next fifty years. The reason Ethernet is

alive and well today is that

it

has become

a non
-
proprietary
standard with
readily available specifications, namely IEEE 802
.3
.


TCP/IP
(
Transmission Control Pr
otocol/Internet Protocol)
is
a suite of

communications standard
s running over
Ethernet

and
this combination
is the basis for the Internet.

Any computer connecting to the I
nternet is using
TCP/IP, regardless if the co
nnection is dial
-
up, DSL, cable, power line
or wireless.
Ethernet

and TCP/IP are

already
used at mines
for

corporate networks.
Some mines have introduced
derivatives such as Modbus/TCP
and EtherNet
/IP

into their

PLC networks to take advan
tage of the low cost of Ethernet

network cards,
switches,
routers and cabling.
Anyone that paid $3000 to a PLC vendor for a network ca
rd knows why a $15

non
-
proprietary

alternative is attractive
.


In addition to data communicatio
n, Ethernet and TCP/IP can be used to carry digitized voice and video

signals
.
Digital voice communication using TCP/IP is referred to as VoIP (Voice over Internet Protocol), and digital
video using TCP/IP is referred to as IP video.

IP video equipment is
significantly less expensive
to deploy
than
dedicated coaxial or fiber networks and opens
up new monitoring possibilities for operators.

This is what is
meant by
convergence


a single network, Ethernet,

which carries voice, video and data.


Wireless Ethe
rnet


In 199
9

a new

standard
,

IEEE 802.11

was
created

to add wir
eless
capability to Ethernet networks
.
R
eferred

to
as

Wi
-
Fi
hotspots

or WL
AN, these networks

consist of
one or more wireless
Acce
ss Points (AP) hardwired to a
Ethernet
network
. WLAN
client

dev
ices include computers, P
DA’s, bar code scanners,
telephones
,
and cameras.



WLAN

networks are optimized for high speed/short range communications.
The
data rate

(bandwidth)

that can
be attained depends on the version of 802.11
, the antennas on each device
, the

distance bet
ween AP and the
client

and how many other wireless clients are requesting bandwidth.


Table
1

-

WLAN Standards, Frequencies and
Data Rate

(Goldhammer, 2004)

Standard

Frequency

Maximum
Data Rate

Useable
Data Rate

(3

m range)

802.11a

5.8 GHz

54 Mbps

23

Mbps

802.11b

2.4 GHz

11 Mbps

6 Mbps

802.11g

2.4 GHz

54 Mbps

23

Mbps


Radio propagation tests through 150 meters of underground drifts shows the
2.4 GHz
802.11b/g signal would
have 30 dB less signal loss than the
5.8

GHz
802.11a signal (
Emslie, 1975).
A
bove 1 GHz

increasing
frequencies
incur greater loss around corners
, which
eliminates

802.11a
from further consideration
in
underground applications.


The wireless data rate
varies inversely with

the distance between th
e AP and the client devices.

Maximum data
rates are attainable only within a small radius from the AP. As the client device moves further from the AP the
data rate drops until the wireless connection is lost and data communication stops.



Figure
1

-

802.11g
Data Rate

vs. Distance, PC Magazine, November 2004



Each wireless client connected to the same Access Point must
share
its bandwidth
.
There
is
documented
degradation in speed for all clients when one c
lient is far away from the AP (
Duda, 2003)
.
When this

happens
the AP lowers its bit rate in order to
work with the

weak signal of
the
distant
client.

The unintended
consequence of this is that the data rate for all other clients slows to the speed of the d
istant client
.


As powerful as these new WLANs are, there are problems as described above. They can be avoided by limiting
the number of clients in each hotspot, and
avoiding distant communication where possible.


Wireless Data Applications


WLAN high spe
ed data can be used in any number of applications

underground
.
Vehicles can be fitted with
WLAN
modems
and controllers to report load weighing and vehicle health

(Dasys, 2003)
.

Tele
-
operation
becomes

a practical op
tion with real data rates over 5

Mbps
enab
ling

high quality IP video streaming. Wireless
enabled hand held computers or PDAs can be used to eliminate paper forms

within WLAN hotspots. Surveyors
and geologists would be able to access the corp
orate network from hotspots located at the working face
.


Not all areas of the mine require high speed data access. Probable hotspot locations are garages, lunchrooms,
refuge stations and production areas. WLAN hotspots could be easily moved to follow the mining activity.

Production monitoring could be accomplis
hed with APs at the draw and dump points.


Adding resource tracking capabilities would enable dispatching, traffic control and real time ore blending.
Varis’ Smart Tag readers plug directly into the Ethernet network and can detect up to 50 tags traveling a
t 50
km/hr.


The mining industry has been talking about these applications for years, but Ethernet WLAN will make their
implementation much easier.


IP Video


Conventional video transmission uses dedicated fiber optic or coaxial cable.
Leaky feeder

can als
o be used to
transmit up to 8 channels of video. In the case of
a

dedicated network the expense is in the installation and
maintenance of the cabling. With
leaky feeder

the expense is the modulator and where required, PTZ (Pan, Tilt,
Zoom)

controls
.
IP vid
eo eliminates the cabling, modulator and PTZ control costs. PoE (Power over Ethernet)
can also be used to power IP cameras, which enables cameras to be located up to 100 meters from the nearest
AC source.

Sony PTZ IP video cameras cost approximately $1600,

which is less than half of the conventional
method’s cost.


IP video quality is dependent on lighting,
encoding/compression

scheme and the
image update rate
.
MPEG
-
4
encoding provides a high quality image
while using

less than 1 Mbps bandwidth. As the imag
e size and update
rate are reduced the required

bandwidth drops significantly so that several dozen low and medium quality
images can be transmitted.


Extending Ethernet
Underground


Several
methods can be used to extend
Ethernet networks
, however
this pap
er will
only
consider three

as they
are the best suited for implementation in
underground mines and tunnels:



Twisted pair cabling



Fiber optic cabling



Cable modem


Inexpensive t
wisted pair cabling can support
Ethernet
up to 100 Mbps (Cat 5
) or 1000 Mbps (
Ca
t 6)

h
owever
the maximum length of the cable is limited to 100 meters. To extend Ethernet over twisted pair
beyond
this
distance

requires an Ethernet switch to be installed
and powered
every 100 meters
which increases the system
cost,
complexity

and
IT
sup
port requirements.

Voice communication is attained with
overlapping WLAN
hotspots and
wired or wireless VoIP phones.


Figure 2


Ethernet over Twisted Pair Cabling

on Mine Level Plan


Fiber
has almost unlimited bandwidth/speed

and
is immune to noise.
Mult
i mode fiber can run 2000 meters
between Ethernet switches and single mode fiber can run 5000 meters.
Fib
er optic cabling can be armored

and
c
omposite fiber/copper cables can provide AC/DC
power to network devices
. Fiber optic
Ethernet switches and
routers

are commercially available

from several vendors
.
D
rawbacks with fiber include cost and that its fragile
nature
requires trained installers.
Voice communication is attained with overlapping WLAN hotspots and wired
or wireless VoIP phones.


Figure 3



Ether
net over
Fiber Optic Cabling

on Mine Level Plan




Cable modems
carry
TCP/IP

over
cable TV

networks to deliver high speed
networking,
Internet access

and
VoIP services
.
DOCSIS 2.0
, t
he
current
standard for cable modems
provides
54

Mbps downstream and
41

M
bps
upstream.
M
ines
with an

existing
Varis Smart Com
leaky feeder

network can be configured to carry
Ethernet
by
adding the CMTS (Cable Modem Termination Service) controller, cable modems and frequency translators. The
frequency translators are required as

leaky feeder

networks have a different bandsplit than cable TV networks.
Cable modem and frequency translators are

installed wherever a high speed wireless network is required.

Voice
communication is attained

using two
-
way VHF radios and optionally,

wired

or wireless VoIP phones.


Figure 4



Overview of Ethernet over
Leaky Feeder




Figure 5



Ethernet over
Leaky Feeder

System




To
decide which method

of extending Ethernet
is best we
also
need to consider
the quality
of the

vo
ice
communication

that each method provides.


Stationary

Voice Communication


POTS
(Plain Old Telephone Service)
telephones
require a separate fiber and/or copper network. Over time these
networks become maintenance intensive due to
cable damage and
corros
ion
.
Telephone wiring rep
air is
eliminated with VoIP,

as proven by the 90+% maintenance cost decrease at Kidd Creek Mine (Nortel, 2003).


VoIP systems can call sister sites that also have VoIP without incurring toll charges. It is quite possible to
reduce

the number of incoming lines leased from telephone service providers (Nortel, 2003) as the inter
-
site
calls are no longer routed over leased lines. VoIP requires a sizable amount of technology investment but there
is a potential to realize a reasonable pa
yback.


All three methods of Ethernet network extension will support desktop VoIP telephones. T
he network must be
designed and maintained properly for VoIP to function properly
.

VoIP is a digital system which has specific
network requirements for voice pri
oritization, bandwidth, packet loss, latency, jitter and end
-
to
-
end delay. These
requirements must be addressed when designing the Ethernet network and the network must be monitored and
maintained to ensure acceptable VoIP performance.


Mobile Voice Commun
ication


Mobile v
oice
communication
is
a very

important service in underground mining.
Mobile v
oice networks
are
used

for

dispatch, traffic control, emergency response, worker safety verification and general production
communication.
The quality,
coverage
and
ease of use
of
mobile
voice
services
are

important consideration
s

in
determining how to extend Ethernet underground.


F
iber optic and twisted
pair
networks
provide mobile voice service using
multiple

WLAN
Access Points and
wireless VoIP handsets.
Each
Access Point installation requires trained technicians to determine its location,
antenna configuration, range and speed. In order to roam between Access Points without dropping calls there
needs to be
overlapping

WLAN coverage between Access Points.

There

is a maximum number of voice calls
that any AP can support and will vary with several factors

with the most critical being

distance between AP and
handset.
V
oice applica
tions need traffic consistency as
voice packets need to arrive relatively quickly toge
ther in
order to prevent jitter and drop
-
offs
.
Wireless VoIP will improve o
nce the IEEE 802.11e Quality of Service
standard is ratified and implemented

so that

wireless voice data will have priority over asynchronous functions
like file transfer. Handset m
aker Spectralink SVP protocol

currently

performs this function in the absence of the
802.11e standard however only for 11 Mbps 802.11b Access Points
.

There are currently no wireless VoIP
handset manu
facturers delivering industrial
-
grade
equipment.


In cont
rast
leaky feeder

is an analog radio system specifically designed for mining and tunneling communication
and is used at over 300
sites

worldwide. It
is a
radiating cable network

that provides continuous
mobile
voice

coverage regardless of mine
size,
drift
size, wall

and support

adsorption properties and
mobile
obstacles such as
trucks.

Leaky

feeder

can be installed by miners and its
maintenance is facilitated by effecti
ve local and remote
diagnostics.
Either

conventional
or

trunked VHF radi
os can be used an
d
industrial
-
grade
portable and
vehicular
(mobile)

radios are available from several vendors.

Accessories to facilitate radio use in industrial environments
include

cases, speaker microphones, headsets and throat microphones.



Both VoIP and VHF radio can
be equipped with PTT (push to talk)

to effectively coordinate tasks. VoIP phones
and VHF trunking radio

with keypads

provide private conversations between parties. VoIP phones have some
features that radios do not including voice mail and SMS messaging.


C
onclusion


The widespread adoption of Ethernet and TCP/IP is a powerful driver in “one wire” convergence.
This one wire
can be a new fiber optic or twisted pair cable or an existing leaky feeder network, or a combination of all three.
Underground mine oper
ators need to understand the cost saving and productivity benefits that can be attained
with an underground converged network that supports high speed wireless networking. Hotspots can be
strategically located to gather vehicle data and provide wireless ne
tworking at the face. Location systems
coupled with vehicle data can be used to improve processes and reporting.


The decision on how to provide mobile voice communications is critical to safety and productivity.
Wireless
VoIP systems are still in their in
fancy and require
expert installation and
tight control of the network traffic to
provide equivalent voice capabilities
to

VHF radios and leaky feeder.

The durability of wireless VoIP handsets
is a question mark and there is a lack of handset accessories t
o suit the underground environment.




References


EMSLIE, A.G., 1975. Theory of the Propagation of UHF Radio Waves in Coal Mine Tunnels, IEEE
Transactions on Antennas and Propagation, Vol. AP
-
23, No. 2, March 1975.


DASYS, A., 2003
,
Implementing an Iredes

based payload monitoring system
, CIM 2003


GOLDHAMMER, S., 2004. Wireless System Design.


Nortel Networks, 2003. Success Story Falconbridge Limited,
htt
p://www.nortel.com/corporate/success/ss_stories/voip/collateral/nn105342_101003.pdf


WACLAWSKY
,
John,

2004.

Cisco Systems


DUDA
,

Andrzej
,

2003
. IEEE , 2003