Survivable Systems Concept of 

Operations 

David Snyder

Office of Mine Safety and Health 

Research 

May 12, 2011
Overview

• Primary Communications Systems• Secondary Communications Systems• Interoperability Goals and Challenges• Concept of Operations – ideas for discus

– Small Mine Example– Large Mine Example

• Single Channel Client Interoperability Exa• Infrastructure Interoperability Example• Interoperability Observations• Blocking Mitigation and Network Modeling
Hard-wired Systems – Pre- 

Limited Communications Access
Coverage of Critical Areas 

Wireless Systems

Wirehas tsafetthe m
Primary Communica

• Primary communications systems are tho

– Operate in the conventional radio band– Use small antennas that allow the min

wearable devices with long battery life

– Have sufficient throughput for ge

operations

• Leaky feeder and node based systems a

primary systems

– Either approach requires vulnerable in

the mine
Survivability....The Challenge

What happens if 2000 feet of all entries are lost?
Survivability..The Goal 

Alternate Communication Paths
Alternate Communications 

• Ideally the alternate communications path 

and highly reliable

• Independent failure mechanisms

– No shared components between the p

alternate path that would fail from a co

• Minimum number of active components (

electricity) yields the highest reliability

• Secondary Systems offer great potential 

communications path, particularly near th

– A borehole directly to the miner would 

alternate communications path
Alternate Communications 

Paths for Leaky Feeder 
Alternate Communications Paths 

for Node based systems
Alternate Communications Paths for 

Node based systems (Mesh)
Survivability....Secondary 

Systems 

What if the event happened here?
Secondary Syste

• Secondary Systems are those that have few 

components and a high potential to survive 

• Medium Frequency Systems and TTE Syste

systems may provide survivable alternative 

• A secondary system is one which:

– Operates in non-conventional frequency – Uses a large antenna that is best suited f

or portable applications

– Does not have sufficient throughpu

operations 
TTE (ELF – LF) MF “Parasitic 

Propagation”

Primary WirelesSystems UHF/V
Medium Frequency Commun

Commercially AvailabDistances up to 2 mile
Through the Earth (TTE) Communications
Permissible Syste

Results

• Feasibility of TTE communications demonstrated• Underground to surface range of 680-ft for voice a

@ intrinsically-safe levels

• Directional finding with beacon• Prototype hardware
Interoperabilit

• “Interoperability” refers to our vision 

of survivable mine communications low bandwidth secondary communichannel would be used as a backup primary communications system.

• Key goal - Miner would be able 

communicate using the same wdevice as used for day to day o
Interoperability G

• To keep things as simple as possib

miner, while ensuring system robus

– Need to avoid unintended 

consequences of integrating 

• Assumption is that the miner’s best 

for accessing the secondary system day communication device

–Only valid if there is simplicity 

from the miner device
Interoperability Cha

• Interopera

multi-chanis more co

• How do w

emergency this second

Hybrid Systems will need to be developed to address the “mediation” challenge.

Normal Operations

Emergency Messages
UHF Medium 

Frequency

Conductor

UHF to MF Interoperab
UHF to TTE Interoperab
UHF to MF to TTE Interope

Medium Frequency

UHF
Implementation Co

• The ability to define an appropriate 

solution is highly dependent on an understanding of how these systembe used.

– We call the scenarios describing the u

system as the Concept of operations o
Small Mine Emergency Co

UHF UHF

Medium Frequency
Small Mine Emergenc

UHF

UHF

TT
Small Mine Consider

• The small mine scenario brings 

likely interoperability desired fecombinations

– End to End Testing 

• From the client device to the Mine O

Center (MOC)

– Fail Safe mechanism so secondary sy

used directly

– MF to UHF and TTE to UHF– UHF to IP or Multichannel Voice on th


Panels 

Sub-mains or Panel entries
Panels 

Sub-mains or Panel entries

Temporary & Moving



Big Mine Considera

• Big Mine protected primary system 

= multichannel high bandwidth back

– End to End test is more complex

• Big Mine Conops brings up addition

considerations

– UHF to TTE to TTE to High bandwidth surviva– UHF to TTE to TTE to MF to High bandwidth

• Fail safe mechanism so that second

can be used directly
Multi- Users Voice and Text Devices Trac

Othe

APs or LF

APs or LF

APs or LF

Air Interface

Network Controller or Head End

Mine Operation Center

Primary System Normal Traffic Flow – Non

5 Kbps/user 

100Kbps
Multi- Users Voice and Text Devices AM

APs or LF

APs or LF

APs or LF

Air Interface

Network Controller or Head End

Mine Operation Center

5 Kbps

Single Channel Client Interoperabil
Multi- Users Voice and Text Devices AM

APs or LF

APs or LF

APs or LF

Network Controller or Head End

Mine Operation Center

5 Kbps 5 Kbps

Single Channel Client Interoperabil
Multi- Users Voice and Text Devices AM

APs or LF

APs or LF

APs or LF

Network Controller or Head End

Mine Operation Center

5 Kbps 5 Kbps

Single Channel Client Device Interopera

Blcahe
Single Channel Cl

Interoperability Is

• Unless only one device is active, ba

limitations will result in unresolved b

• Connected device has to be within 

of the secondary system

• Users on the Secondary System ha

communications with people in the the mine

• The advantage is that communicati

dependant on any aspect of the priminfrastructure
Multi- Users Voice and Text Devices AM

APs or LF

APs or LF

APs or LF

Air Interface

Network Controller or Head End

Mine Operation Center

Infrastructure Interopera

5 Kbps/user 
Multi- Users Voice and Text Devices AM

APs or LF

APs or LF

APs or LF

Air Interface

Network Controller or Head End

Mine Operation Center

Infrastructure Interopera

5 Kbps/user 

Blocahe
Infrastructure Interope

Example Issues / Adva

• Potential for blocking is considerably grea

the client only example

– Emergency channel is available to a la

users

• Users within the mine could potentially st

communicate with surface (Assuming no 

with each other if primary communicationis lost 

• By implementing the interoperability betw

secondary system and the infrastructure, longer needs direct UHF communications relay.
Interoperability Obse

• Ideally, the secondary system should be 

communicate either directly with a client dthe network infrastructure.

• In either case, bandwidth restrictions in the comm

the MOC could lead to blocking which causes:

– Lost Messages– Inability to communicate to the surface– Lost data from sensors

• Clearly, the blocking implications are not desirable

– Mitigate the effect of blocking to the extent pos– Decide what to do with the traffic that can not 

surface due to blocking
Blocking Mitigat

Techniques

• There are several techniques that could b

employed to mitigate the blocking challenthe utility of the secondary communicatio

– Multiple Access Protocols– Queuing – Traffic Reduction & Traffic Concentration– Traffic Control

• Message Prioritization• Message acknowledgement and control of re-s

– Recording of traffic for later transmission

• Practicality and optimal placement of these “Netw

features are a function of the protocols and system 
Network Managem

Gateway Conce

• Conceptually, a potential solution is to have a “Ne

Management Gateway” between the secondary sprimary system that:

– Has an interface to the primary infrastructure– An air interface for client devices– An interface to the secondary system– Contains all of the blocking mitigation techniqu

software, and intelligence 
Network Managem

Gateway

Air Interface

Gateway

Prim. Inf. Interface

Secondary Comms. Interface

SeSys

QueuingPrioritizationCompressionAck/NackRecordingEtc. 
Network Managem

Gateway

Air Interface

Gateway

Prim. Inf. Interface

Secondary Comms. Interface

Sec

Queuing SysPrioritizationCompressionAck/NackRecordingEtc.

StandPhysInterf
Design Considera

• The design of an effective interoperable s

maximum survivability in a real mine is a many things.

– Location of secondary communications path in – Capabilities of the Network Elements and Clie– Availability of AP or other traffic concentration – Bandwidth of Primary and Secondary commu– Network topology as defined by the layout in t– Failure Scenarios as defined by the assumed 

• Fortunately, there are network models tha

attempt to model the effectiveness of netw
Network Modeli

• NIOSH is very interested in network modeling to t

effectiveness of systems before and after mine di

– There are two types of modeling NIOSH is inte

• Propagation modeling (Physical cha• Network simulation (OPNET/NIST)

• Propagation models can be developed somewhat 

independent of any particular system)

• Network simulation is highly dependent of specific 

system

– Required information rests with the Equipmen
NIOSH/NIST IA

• NIOSH has entered into an Inter-Agency 

(IAA) with NIST to assist in the Network M

– The first task was to model the performance o

Frequency Network (OPNET)

• Future work will be shaped by your 

– Is there value to you as an electr

manufacturer in network modelin

– Is there a need to agree to a stan

interface somewhere in the netw

– Is this just a waste of time?
Things to think abou

• How would you, as an equipment manufa

an interoperable system working, given thmaking high-bandwidth systems interopebandwidth systems?

• What would be required or desirable in an 

system as described, and what are the tehurdles?

• From an equipment manufacturer’s persp

the appropriate level of involvement of goagencies in realizing such a system, partagencies (i.e., NIOSH) or in the area of stdevelopment (i.e., NIST)?
Summary

• The NIOSH role with C/T to this point has b

enabling technologies and conduct researc

• The challenges associated with interoperab

and secondary systems are significant.

– Many potential approaches exist– It is not clear that there is a “R&D Gap” i

enabling technologies

– There does appear to be a gap in the ab

system performance (blocking, survivab

• We welcome your input as to where N

should be spending our limited resouimportant area!
Disclaimer

The findings and conclusions in this pare those of the authors and do not nrepresent the views of NIOSH. Mentiocompany names or products does noendorsement by the Centers for Diseaand Prevention
Contact Informat

Presented by: David SnyderContact info: 412/386-5304

fwx4@cdc.gov

The Office of Mine Safety and Health Reseaof the National Institute for Occupational Sa(NIOSH) www.cdc.gov/niosh/miningNIOSH is a division of the Centers for DiseaPrevention within the Department of Health Services www.hhs.gov