45943119 SCADA Communications Systems Using Radios

SCADA Communications Systems Using Radios

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INTRODUCTION

This presentation is intended to provide a brief overview of the benefits of radio based networks and a genericoverview of the available RF based technologies used in SCADA applications.

Technologies to be covered include:

• licensed narrow band radios• unlicensed low power or spread spectrum units• mobile phone: analogue and digital• trunking based networks: analogue MPT 1327, digital Tetra/APCO25• satellite communications: low earth orbiting, VSAT• dedicated data networks: Mobitex, Motorola RDLAP.

The presentation will touch on the associated costs of these networks, their performance, advantages,disadvantages, spectrum regulations, interference/protection including coverage and propagation considerationsfor each technology.

A small selection of typical network topologies/case studies using radio based technology will be offered whichwill highlight some advanced features such as remote diagnostics, combinations of technology, multiple andprotocol transportation etc.

1.0 INTRODUCTION TO RADIO

The deregulation of the telecommunications industry in many countries together with the growth of the cellularphone market has generated a major interest in alternative data radio communications services.

Wireless distribution is an ideal medium for the transmission of data and has advantages such as ease ofinstallation, low infrastructure and terminal costs when compared to hard-wired services.

Radio communications networks provide the physical medium for the transfer of data and have becomeincreasingly more popular within the SCADA market for the control and acquisition of data from remote locations.Applications for such radio-based networks are quite diverse and range from short-range point to pointapplications where cable solutions are not available, maintainable or practical through to wide area applicationswhere the cost benefits of using radio are easily highlighted.

Although radio cannot replace the bandwidth capabilities of cable or fibre services, (radio providing data rates of1200bps through to 10Mbits for moderate capacity links) the reliability, performance and running costs of radionetworks have matured considerably over the past few years.

In contrast to terrestrial based services, satellite communications also provide a "radio" based alternative forSCADA applications. Many services exist which provide for low speed data through to high capacity links andthese have been used for remote SCADA applications. In more recent times the world has been presented with theprospect of LEOS (Low Earth Orbiting Satellites) which are deployed only a few kilometres above the earth andmay provide a new array of solutions which are readily suited to the SCADA market.

In addition to satellite services, various other technologies are available which provide common carriercommunication media to the user. These services, such as trunking, digital data networks, cellular networks etc.All provide viable radio based media which lend themselves for use in SCADA applications and provide the userwith a fully maintained and supported communications medium which does not require user licensing.


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Various other radio technologies exist which do and do not require licensing. A host of issues exists with each ofthese but one of the most important relating to the use of radio is that spectrum is a limited resource and it cannotbe recreated or expanded.

If one looks at spectrum usage historically there has been a progression from low frequency VHF devices (around170MHz) through to much higher frequency bands (such as 900MHz, 2400MHz and higher). As we continue toexhaust our radio spectrum, manufacturers have been forced to move up into frequency bands where additionalcapacity exists (although there are very few uncontested bands available in the urban areas) and employ morebandwidth efficient technologies.

To ensure that radio is employed in a structured and coordinated manner, the spectrum is usually managed by agoverning body. This body is responsible for allocating licences, band planning and placing restrictions on the useof particular bands for the overall protection of ALL users. This body works in conjunction with world standardsorganisations (e.g. IEEE) to encourage standards implementation and band plans in order to improve bandwidthand spectral efficiency.

1.1 Why use radio?

Over the years radio has become a reliable and cost effective medium for the transmission of data. Man's desire togather data for control and monitoring purposes have been a natural reason for the adoption of radio.

In summary, radio has many advantages over other alternative solutions, which include:

• Radio offers communications to locations that may not be accessible by other means.• Radio provides a more robust alternative than other means such as replacement of mechanical slip rings and

replacement of underground cable on mining sites where they are at risk of being excavated.• Radio offers an equivalent leased line alternative and is usually cheaper in terms of annual operating costs and

hardware.• Radio services can be connected more quickly than hard-wired circuits, requiring in most cases minimal

installation.• Radio offers greater portability and mobility where the user can move terminals around his plant or even

move his whole plant without the need for major rewiring or waiting for external line service connection.• Radio capital cost is equivalent to or cheaper than leased line equipment in hardware capital costs.• The user owns the data transport equipment and pays only for radio licensing or in the case of a common

carrier network an infrastructure access fee.• The user is in control of the communications medium and its availability.


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2.0 INDUSTRY GROUPS AND THEIR REQUIREMENTS

By far the major users of radio based telemetry are:

• Oil & Gas - Production, Transmission (Pipeline) and Distribution• Industrial Plant Control - Process Monitoring• Agriculture & Environment - Weather, Pollution and Soil monitoring• Power Utilities - Supply, distribution & network monitoring• Water Utilities - Supply, distribution & management of fresh, irrigation & waste water• Public Information Displays - Permanent and temporary - signs for public transport, traffic control, special

events

In addition to these groups, many other organisations utilise data radio communications for applications such as:

• Point of Sale (POS) terminals• traffic control systems• alarm monitoring• public messaging• slow scan video• carrier back-up links - last mile solutions.

Each of the applications places different requirements on the radio network in terms of architecture and throughputdemands (Point to Point links for gas pipelines and Point to Multipoint services for wide area monitoring). Tohighlight this issue, a Remote Sign Control application will be less demanding in terms of data throughput andtime delays in comparison to the Gas or Electricity Industry which have potentially life threatening implications.

Although there is no hard and fast rule, the Utility Industries adopt high speed digital radios for their mainSCADA applications allowing a great deal of flexibility in terms of capacity, protocols and expendability. Incontrast to this, some people argue that the human response time to these telemetry events has a resolution of"seconds" and as such lower speed analogue solutions are more than suitable!

There is no doubt that in the fast moving Telecommunications Industry there is a distinct bias to adopting worldstandard communications protocols for the transfer of data. This push is also prevalent in the radio transport layerwhere there is a drive to adopt a platform (TCP/IP or part thereof) that will provide the transparent transport ofvarious protocols over a common radio medium. However to date, there are few vendors who have adopted WorldStandard Protocols.

Higher data throughput has emerged as a strong focus point which has primarily come about due to the growingdemand for information and the trend towards monitoring a large number of remote devices on a single radiochannel.


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3.0 WHAT RADIO CONNECTED ALTERNATIVES ARE AVAILABLE?

Several radio alternatives are available to the end user. These range from dedicated private networks through tocommon carrier services which are available ONLY within the high density - city locations.

In general the SCADA industry has swayed towards the adoption of private networks primarily due to:

• the lower running costs• the importance of being in control of the network• available carrier services not covering ALL areas required• minimal ongoing operating costs• guaranteed and controlled network performance against a common carrier service, which is a shared medium.

The following is a brief overview of some of the radio-based services available. Each of these services has its ownmerits and/or disadvantages and these should be taken into consideration at the design stage as the hardwareselected will lock you into the chosen technology.

This review of available technologies is meant as an indicative overview based on subjective opinion and is NOT acomprehensive product presentation.

Some alternatives are:

3.1 Conventional two-way radios using external modems

In the past, the only radio solutions available were based on standard two-way radios which provided narrow bandwide area system coverage. (Typically 10-30km however links of 50-100km are not uncommon.)

Advantages:

• low capital cost and product available off the shelf• many alternative hardware vendors

Disadvantages:

• slow speed data - typically 1200bps max• new regulatory issues now require Type Approval for radios which are externally modulated by third party

devices (modems)• often requires complex interfacing and regular alignment by experienced technicians• mixing of two equipment suppliers - no overall product / system responsibility• devices not tailored for each other resulting in slow key up times, no guarantee of Bit Error Rate (BER)

performance or data integrity• typically very power inefficient - not ideal for solar applications

Subsequent to the use of two way radios, many RTU vendors now utilise purpose built OEM radio modules whichare engineered with in-built modems and offer additional features such as low power consumption, miniature size,remote diagnostics capabilities etc.

3.2 Dedicated purpose designed and manufactured digital data radio modems.

Several years ago, spectrum management bodies around the world developed bands plans (400/900MHz) fordedicated data radio modem products to cater for emerging technologies and industry demands for higher speedpurpose designed digital data radio products.


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The result was the development of narrow band data radio modem products from many vendors around the worldwhich were capable of 9600bps Point to Point (PTP) and Point to Multipoint (PTMP). The approach to productdesign and "over the air" protocol standards were many and varied with only a few companies adopting worldstandard network layer protocols.

Advantages:

• data rates of 9600 bps (and faster) achieved (some Full Duplex)• very fast switching times - support greater number of remote units in multi-point systems• intelligent devices offering multi-protocol support, remote diagnostics facilities, CDMA collision avoidance

schemes etc.• long range communications (30km up to 100+km)• purpose engineered complete radio/modem manufactured product• higher assurance of data integrity• licensed operation offering no external interference• world acceptance of 400/900MHz frequencies for dedicated data products• higher environmental and performance specifications.

Disadvantages:

• more expensive than conventional lower speed two-way radio solutions• very few vendors adopting communication standards• licensing of product required (ongoing costs).

3.3 Unlicensed low power or spread spectrum devices

It is usually a misconception that obtaining licenses for radio equipment is costly and time consuming. Mostreputable radio based companies can assist or undertake licence applications from an experienced perspective.Further to this, in the area of deregulation, licensing can be done by independent registered groups who will issue alicence within days.

There are various unlicensed frequency products available, which range from narrow band low speed through towide band high speed. These products are used for NON critical and close proximity applications as no protectionexists to resolve interference issues.

There are two classes of unlicensed equipment. These being:

• spread spectrum (up to 4 Watts ERIP in certain bands) and• low power (3-100 milliwatts) narrow band radios.

3.3.1 Spread spectrum

Spread Spectrum is a technology that was developed by the US Military some 50 years ago. Although there arevarious forms of spread spectrum devices (frequency hopping, direct sequence), the basic operation is to spreaddata across a wide frequency band and reduce the impact of interference to the transmission rather than utilising aspecific narrow band channel.


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Advantages:

• no need for a licence.• data rates of up to 10Mbps achieved (half duplex).• not operating on a dedicated frequency - offers some immunity to interference• in-built security/robustness such as spreading sequences, addressing schemes, protocol etc.

Disadvantages:

• unlicensed product operating with a mixture of other equipment - no coordination of users / interference• no guarantee of data integrity or operating performance• spectrum management authority considerations to ban directional antennae reducing communications range• short range operation (typically less than 5-201cm)• unregulated resellers who abuse the lack of standards (operate higher output power) and misrepresent the

product, its capabilities and operational distances

3.3.2 Low power narrow band

The narrow band frequencies, which are used for low cost data transmission, cover the 40MHz, 470MHz and900MHz frequency bands.

The most popular and probably the most suitable to SCADA applications is the 472MHz frequency band wherethe RF power output is limited to 100MW.

In comparison to spread spectrum, these 470MHz narrow band unlicensed products offer similar communicationsdistances and cost much lessbut offer only limited bandwidth.

Advantages:

• lower cost product• no licence required• data rates of up to 4800bps achieved (simplex/half duplex).

Disadvantages:

• unlicensed product operating with a mixture of other equipment• no guarantee of data integrity or operating performance• low band (40MHz) versions require large antennae and suffer greatly from external interference and

atmospheric conditions.

3.4 Mobile phone - digital and analogue

Mobile phones are by far the most prevalent means of radio communications available and are being usedextensively for SCADA applications. This is primarily due to the simplicity of connection and relatively lowinfrastructure cost associated with small quantities of remote units. Until recently the analogue phone system wasvery popular however as this is being phased out, people are migrating to the digital service where higher datarates are possible. However due to operating costs, the mobile phone service does not lend itself to large-scalenetworks which require continuous polling or heavy data transfers.


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Advantages:

• extensive area of coverage• moderate data rates available 9600bps• no infrastructure costs• network fully maintained by carrier.

Disadvantages:

• call dropout problems affect larger data downloads• ongoing monthly fees and expensive call costs - not economical for large groups of remotes or regular data

transfer• call establishment delays• performance / bandwidth - dependent on call quality/cell voting• digital has limited coverage in outlying areas where remote SCADA applications are prevalent• digital phone cells extend to a maximum distance of 43km (possibly less for reliable data transmission).

3.5 Trunking based networks: MPT1327/TETRA/APCO25

Trunking based networks have been developed predominantly for mobile voice communications. MPT1327 is aworld standard developed many years ago and has been adopted employing mainly analogue technology. AlthoughMPT1327 has been used for limited SCADA applications, there are few highly regarded networks due to poor datathroughput and long call set-up times.

More recently, new digital platforms have been developed; TETRA (European Standard) and APCO25 (MotorolaUS Standard) each providing their own benefits based on digital platforms. TETRA and APCO25 are more suitedto SCADA applications due to higher data transfer at speeds (around 28kbits) and relatively quick callestablishment times.

Operators can provide base station infrastructure that gives wide area coverage, sometimes extending across citiesor states. However, users may be limited by coverage issues because initially infrastructure will be mostly in urbanareas.

Advantages:

• no infrastructure costs• network fully maintained by carrier• possible large network coverage• higher data throughput - digital network

Disadvantages:

• public network no guarantees of grade of service.• terminal equipment expected to be high• infrastructure costs very high for users to establish their own networks.• high ongoing running costs.


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3.6 Satellite communications: VSAT/LEOS

Satellite communications have been around for many years and provide common carrier services, which have beenused for many SCADA applications.

VSAT provides up and down links ranging from 64kbits and upwards and provides "world wide" coverage makingit ideal for remote communications. However, VSAT terminals and hubs are quite expensive with high operatingcosts. Based on these factors, VSAT does not lend itself to SCADA applications unless they employ exceptionreporting or no other cost effective medium is available.

LEOS (Low Earth Orbiting Satellite) that navigate the earth at much lower altitudes and operate on lowerfrequencies are starting to appear. Due to these factors terminals are being developed specifically for SCADAapplications which can include I/0 interfaces and range in price from US$650.00 upwards. LEOS provide the userwith moderate data rates (1200 to 4800bps) but once again operating costs are based on data throughput.

Advantages:

• worldwide coverage• no infrastructure costs• some LEOS terminals employ simple I/O.

Disadvantages:

• expensive operating costs• VSAT terminals quite expensive.

3.7 Dedicated data networks: Mobitex/Motorola RDLAP

With the emergence of the data communications market, two vendors have developed common carrier datanetworks which have been adopted worldwide. Both networks are digital and are designed specifically for thegeneric data communications market and provide 8000bps (Mobitex) and 19200bps (RDLAP) throughput. Itshould be noted that the actual throughput figures are considerably less for both systems due to the protocoloverheads. The networks are based on defined protocol standards (although not necessarily open standards) andprovide seamless transportation of data.

Advantages:

• no infrastructure costs• network fully maintained by carrier• high data throughput - digital network• terminal equipment relatively cheap.

Disadvantages:

• public network, depending on network loading connection times will vary• available only in capital cities• high ongoing running costs• user equipment has to emulate the networks proprietary protocol.


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4.0 WHAT IS REQUIRED IN TERMS OF LICENSING?

The possible radio connected services discussed vary in terms of licensing requirements. Although common carrierservices employ licensed products, the costs associated with this are borne by the carrier. Thus the followingservices do not require licensing by the end user:

• mobile phone services• trunking networks• satellite communications• dedicated data networks and• unlicensed low power products.

Where licensing is required, the relevant spectrum management authority is responsible for planning andregulating the channels that can be used, the purposes for which each can be used and the specification ofthe equipment.

It should be noted that there are several alternative registered frequency assignors who can allocate frequencies.

The ultimate responsibility for compliance with the various Radio Communications Acts and laws rests with theuser and/or service provider i.e. the licence holder.

With all the above in mind, it is imperative that a potential user select reputable equipment from a reputablesupplier who complies not only with the specifications but also with the spirit of the band plan rationale for theiroperation and in the manner it was intended.

It should also be noted that local radio channel assignments and equipment specification are different fromoverseas and NOT all imported products seen in the local market place are suitable or allowable for use locally.

4.1 Protection from other users (interference)

The band planning process employs:

• primary and secondary user and• protected and unprotected concepts.

The primary user has assignment priority in a segment and a secondary user application is one who may have tovacate his assignment ( within a reasonable time frame) should the primary user require more spectrum.

4.1.1 Example protected assignment

The 900MHz point to point channels are allocated by the Spectrum Management Authority with the aid ofcomputer modelling which factors in all radio users including their exact fixed location, equipment and antennatypes.

New allocations are made on the assumption that the present users and the new user will cause each other NOINTERFERENCE of any consequence and everyone can operate with a high grade of service (save equipmentfaults or other natural phenomena).


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4.1.2 Example unprotected assignment

In contrast to primary protected applications other services such as spread spectrum data applications occupy the900MHz and 2400MHz frequency bands.

Within these bands live other equipment such as microwave ovens, medical and industrial electronic equipment.

The primary operation for these segments is the Department of Defence - Radio Navigation while spread spectrumapplications are considered as secondary users.

In addition there is no assignment method or technology employed to ensure users do not interfere with oneanother, and the user must be aware that he operates at his own risk without guarantee of grade of service andwithout causing interference to others.

4.2 Licensing and associated costs

There are various forms of licensing depending on the specific band plan for which the equipment is licensed.These licence fees are currently under review and indications are that the fees will increase slightly. However thefollowing provide a typical indication:

For Point to Point applications the user must apply for a specific licence for each link which will require the use ofdirectional antennae. A one time application fee is payable with an ongoing licence fee paid annually.

For Point to Multi Point operation when a master radio ( at a high location) services a number of remote slaveradio data terminals, a one time application fee is payable with an ongoing licence fee paid annually regardless ofhow many remote sites are employed.

For unprotected secondary applications such as spread spectrum data equipment operation in the 915 to 928Mhzband no formal licensing is required. However a registration fee may be payable.

4.2 How far will radio go?

This is by far the most often asked question about radio communications. It cannot be answered in black or whiteterms.

The main factors determining the distance radio signals will travel are frequency selection and surrounding terrainobstructions. Other factors to be taken into account are detailed on the following typical path analysis calculation.

Some typical examples of propagation distances:

• UHF conventional and dedicated data radio modems offer communication distances of around 25km to100+ km with appropriate site locations and heights. These devices are designed with high receive sensitivityand employ excellent data recovery techniques.

• Unlicensed low band products (40MHz) offer limited distances. In CBD areas typical distances of aroundl km will be achieved due to the high noise floor that exists at these frequencies. In rural areas with clear lineof sight distances of up to 10 km can be achieved depending on the ever-changing environmental conditions.

• Unlicensed Spread Spectrum devices with Yagi antennae (likely to be disallowed) offer distances of up to10 km. This is primarily due to the legislated limit to EIRP in these bands.

• Mobile phone coverage is basically "country wide" although the digital service suffers in the rural areas ascells work only within a 43 km radius.

• Satellite coverage can be "local" or "global". This will depend on the network and the amount of satellitesemployed.


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• Trunking networks interconnect users via a series of linked base stations. Some MPT1327 systems providestatewide and even interstate coverage.

• Mobitex and RDLAP data networks offer coverage within major capital cities ONLY.

The above communications distances are meant as a guide and are typical indications only.

5.0 TYPICAL RADIO CONFIGURATIONS

The applications for digital radio products are numerous. Radio can be deployed quickly for permanent ortemporary connection of point to point or multi-point applications.

The ways in which private radio based networks can be employed vary dramatically and are influenced by thetopographic terrain which sometimes requires the implementation of repeaters. Well-engineered networks providerobust reliable solutions, which lend themselves to expansion once the initial infrastructure is in place.Some typical network configurations include:

Typical Point to Point Link

Typical Point to Multipoint Link


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The Point to Multipoint network employs a centralised Master Station supporting many remote units. The systemalso incorporates a store and forward radio, which are used where direct coverage to remote sites is not possiblefrom the base station.

In terms of frequencies, Point to Multipoint systems employ two frequency pairs (i.e. a different frequency fortransmit and receive). However simplex channels (common transmit and receive frequencies) are also used inparticular for networks which offer peer to peer communications.

Although intelligent digital data radios can provide network functionality allowing the transportation of multipleprotocols over a common communications network, it should be noted that RTUs provide the overlyingcommunications functionality such as:

• addressing• collision avoidance (C/DSMA)• master / slave relationship• store and forward• poll / response mechanisms• error checking / error recovery (retries)• unsolicited report by exception.

There have been trends towards the implementation of networks based on backbone Point to Point links with "sub-systems" branching out to Point to Multipoint systems. A sketch depicting this follows:


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The benefits of this configuration are that:

• There is a dedicated full duplex backbone which can multiplex multiple data streams.• The Point to Multipoint hubs can be a mix of devices (low cost analogue/higher speed digital).

There is a multitude of ways in which private radio networks can be implemented and the above is only a smallrepresentation.

6.0 RF PROPAGATION MODELLING

In order to determine the suitability of radio, RF path propagation studies are required. A highly reliable path isconsidered as a "clear line of sight" providing a fade margin of greater than 30 dB. The key to this is to get heighton at least one end of the link

Apart from physical field testing, path propagation studies can be done using dedicated software, which requiresentry of key parameters such as antenna heights, antenna gains, cable losses, terrain data etc. Terrain data can bemanually defined from reading topographical terrain maps or alternatively imported directly from digitised terraindata obtained from mapping organisations. (Typical accuracy of better than 10 metres with a grid spacing of betterthan 9 seconds.)

Factors that affect RF propagation include:

• earth curvature over long distances• local obstructions / clutter• terrain heights - line of sight• free space loss• atmospheric conditions• multipath.

Earth curvature is an important factor when calculating path losses (particularly with long paths) and is includedwithin the calculations as a K constant value usually between 0.66 and 1.33 depending on differing atmosphericconditions i.e. air density gets lower as latitude increases which causes RF signals to travel more slowly near theground which in turn causes the signal to curve downward.

The distance from the centre of the RF path to the reflection point is called the Fresnel height. To avoid a reflectedpath signal arriving at the receive antenna (180degrees out of phase) cancelling the main signal, a conservativepath selection would use a Fresnel path clearance distance of 0.6 times the first Fresnel zone.

Master Radio Tower RTU Radio Tower

Fresnel Height

Fresnel Zone

Reflected Path

Fig. 2


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Obstruction losses must be taken into account and although there are specific formulas for calculating clutter lossetc. they are quite complicated and beyond the scope of this discussion paper.

Availability of radio paths is very important and the issue of fading is usually the topic that is most important inradio system design. Fading is when the link attenuation increases from the normal quiescent level, reducing thesignal strength received at the radios and causing breaks in transmission. The first consideration is fading causedby changes in atmospheric conditions (signal being deflected). This can be prevalent on long paths using narrowbeamwidth high gain antennae. The second type is called multipath and is caused by multiple signals arriving atthe received antenna out of phase and thus cancelling each other. Reflections occur when there are discontinuitiesin the distribution of heat or water in the atmosphere. This happens as the sun is rising or setting. During thesetimes, the sun heats air higher up so it is hotter than the air at ground level. This also happens when air masses ofdifferent temperature override each other. Inversions are notorious for causing deep fading and lost links.

In order to increase the path availability, we can add diversity. This is based on the hypothesis that simultaneousfading on two transmission paths is unlikely. Diversity can be accomplished by several means. The various formsof diversity are frequency, space, time, polarization and algorithm. By having redundancy in any one of these, wecan increase the availability of the signal.

Diversity systems are not employed unless 100% availability is highly critical.

Taking all the above into account, path plots can be undertaken and the accompanying radio path profiles aretypical examples of a computer derived path plot. These plots show the terrain profile shaded, with the "k=1.33"earth bulge profile and a direct optical line of sight ray line between the two antennae, and a curved line below theray line representing the 60% of first Fresnel zone boundary. If the earth profile remains clear of the 60% firstFresnel zone, this path is considered "CLEAR", as shown below:


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If the earth profile touches or goes past the ray line the path is considered "OBSTRUCTED".

The ray line path length can also start to influence the signal as shown below:

Following is a typical report page from a path profile where most of the entries are self-explanatory. The last twoentries sum up the link performance. The fade margin gives the number of dB that the link can degrade until thereceived signal reaches the minimum desired signal level. The Raleigh Service Probability gives the percentage oftime that the link will be available.


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ers465-4.pl3 DAIMARU ERS465

Elevation (m) 19.71 54.42Latitude 037 48 45 S 037 45 03 S

Longitude 144 57 39 E 145 04 06 EAzimuth 54.13 234.07

Antenna Type 6 dBd Omni 0 dBd OmniAntenna Height (m) 170.00 5.00Antenna Gain (dBi) 8.15 2.15Antenna Gain (dBd) 6.00 0.00

TX Line Type LDF4-50 RG213/UTX Line Length (m) 20.00 7.00

TX Line Unit Loss (dB/100 m) 4.96 16.40TX Line Loss (dB) 0.99 1.15

Connector Loss (dB) 0.00 0.00

Frequency (MHz) 450.00Path Length (km) 11.69

Free Space Loss (dB) 106.89Diffraction Loss (dB) 25.25

Net Path Loss (dB) 123.98 123.98

TX Power (watts) 5.00 1.00TX Power (dBW) 6.99 0.00

Effective Radiated Power (watts) 15.85 0.77Effective Radiated Power (dBW) 12.00 -1.15

RX Sensitivity Level (uv) 1.26 1.26RX Sensitivity Level (dBW) -135.00 -135.00

RX Signal (uv) 4.47 10.00RX Signal (dBW) -123.98 -116.99

RX Field Strength (uv/m) 28.72 130.54Fade Margin (dB) 11.02 18.01

Raleigh Service Probability (%) 92.401 98.432

Typical Page Report

7.0 CASE STUDIES

Confirming the suitability of Radio for SCADA applications, the following are a few case studies of actualsystems operational in the field.

The drawings are in the presentation slides that go with this paper.

7.1 Gas pipeline application

Radio technologies employed:

• dedicated data radio modems• microwave links.

The following network was employed to provide statewide coverage (Victoria) to Melbourne's major GasTransmission Group. The system utilises Telstra's backbone microwave distribution network and DR900 BaseStations spurring off to form a large array of Point to Multipoint networks to monitor CRITICAL backbonepipeline infrastructure.

The complete microwave distribution network and base sites are all fully duplicated with automatic hot standbyand or re-routing capabilities. The network provides an overall data capacity of 64kbps with a true 9600bpsthroughput to each remote site.


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The network currently employs multiple protocol transmissions and is fully monitored and controlled by Telstra's24 hour a day National Operations Control Centre Staff.

7.2 Offshore oil / petroleum application


• dedicated data radio modems• dedicated conventional radio• SATCOM-M Communications.

The following network is unique in that it was one of the world's first unmanned offshore oil "platform buoy"applications. The unmanned buoy is approximately sixty (60) metres high and is half submersed under sea level. Itis fully powered by diesel generators and controlled from the mainland via a diversity based dedicated link andSATCOM communication network.

The primary communications link is based on dedicated full duplex digital radio running at 9600bps. These linksare fully redundant automatic changeover units, which communicate to an island and then via a second set of linksback to the mainland. Being such a critical application, a second set of fully redundant 9600bps links are onstandby with a further fail safe communications path being satisfied via SATCOM terminals.

These SATCOM terminals are also used directly to monitor other critical parameters such as corrosion sensors etc.by suppliers of the equipment who are based in other countries around the world.

7.3 Power distribution applicationRadio technologies employed:

• 900MHz frequency PTMP system using AD2000 RTUs and base station repeater.

Indian rural distribution feeders of 33kV power reticulation are over subscribed with demand for electricity. Therural feeders are a mixture of agricultural (mainly irrigation) and domestic users in the same local area. With agrowing demand for electricity, the local utility is faced with having to constantly shut off power to all users incertain areas to facilitate peak demand control. The solution to increase electricity supply requires long terminvestment in generating plant, something not easily, cheaply or quickly implemented. The scheduling of poweravailability was seen as a method of regulating power use between all consumers to ensure continuity of supply.No other communications media would suit the control and monitoring of pole mounted 33kV circuit breakers andtransformers to allow such a scheduled system to be implemented easily and cheaply. A dedicated radio basedRTU was used to monitor local transducers for measurement of 3 phase current, volts and phase angle as well astransformer temperature and oil level. Local tripping of circuit breakers on faults was also enabled in the RTU. Toregularly supply consumers with a secure and regular electricity supply, a monthly schedule (which is seasonallyadjusted to meet the local agricultural requirements for irrigation) is downloaded from the main sub-station controlmaster site. The RTU stores this schedule and can act independently of the operation of the radio system ifrequired. Local events a stored in data-log memory for later retrieval by hand held devices.

7.4 Waste Water application


• 450/460MHz frequency PTMP system using AD2000 RTU and base station repeater.

A City Council has implemented a Wide Area Data Distribution Network covering a coastal region in theAustralian island state of Tasmania for monitoring and control of their wastewater distribution and managementsystem. The system currently supports in excess of 50 remote sites and communicates with the AD2000.


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The system incorporates a base station repeater and several supplementary store and forward sites operating in aPoint to Multi-point configuration supporting a polling regime. The RTUs perform all local control via the in-builtLadder Diagram programming. The system interfaces directly to an HMI SCADA graphical monitoring system.

7.5 Water Supply application


• 450/460MHz frequency PTMP system using AD2000 RTU and base station repeater.

A City water authority has implemented a local area data distribution detwork covering a suburban area of Perth,Western Australia for monitoring and control of their underground borefield water supply, distribution andmanagement system. The system currently supports in excess of 20 remote sites and communicates with theAD2000.

The system incorporates a base station repeater operating in a Point to Multi-point configuration supporting apolling regime. The RTUs perform all radio data transfer and interface to existing PLCs via RS232 using the CCMprotocol. The system interfaces directly to an HMI SCADA graphical monitoring system.

7.6 State-wide automatic building fire alarm monitoring application


• Several isolated 450/460MHz frequency PTMP systems using AD2000 RTU and base station repeater.

The AD2000 units have been applied as a unique solution for a fire and security monitoring applications. TheNorthern Territory Fire and Rescue Service has installed a wide area network of fire monitoring systems forbuildings in Darwin, Jabiru, Nhulunbuy, Katherine, Tennant Creek, Yulara and Alice Springs.

The NTFAST system is a distributed alarm acquisition, monitoring and reporting system. It consists of a collectionof radio telemetry devices based on the AD2000 RTU modules connected to local Fire Indicator Panels (FIP's)transmitting FIP status to a Master Base Station, telemetry device. The Master Base Station is connected to a PCbased NTFAST Alarm Server. The function of the NTFAST Alarm Server is to scan the information collectedfrom the local RTUs and to report the relevant alarm information.

If an FIP is in alarm then the alarm is raised and the NTFRS members in that Emergency Response Area (ERA) isnotified. Other FIP status information such as FIP standby, isolate and test signals is reported to the responsiblebodies. The NTFAST system is distributed throughout the Northern Territory in a hierarchical structure. Eachlocal centre operates independent of other centres throughout the Northern Territory. As the system is connected tothe NT Police, Fire and Emergency Services (PFES) WAN; the local NTFAST Alarm Servers are monitored bythe communications centre NTFAST global client workstation in the Peter McAulay Centre located at Berrimah,Darwin. During the course of monitoring and reporting events the NTFAST Alarm Server interfaces with variousdatabases, mobile data terminals, PA systems, radio system and printers. The system is a real time mission criticalapplication developed specifically for the Northern Territory Fire and Rescue Service and serves to ensureprotected buildings are monitored on a 24 hour a day basis. It provides significant enhancement to firefightersafety through detailed knowledge on each site monitored and provides ease of reporting through Mobile dataTerminal usage into the Fire Service reporting system - AIRS. Clients, building owners and Fire AlarmContractors also receive an enhanced level of service through the systems advanced reporting abilities thus leadingto reduced levels of false alarms and fire alarm system faults. Significant running costs have been saved andincreased reliability with the removal of the need to pay leased landline costs for monitoring remote devices. Insome of the remote locations these services were either not available or of poor condition.


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7.7 Mining application


• 450/460MHz frequency PTMP system using AD2000 RTU and 900MHz high speed data radio modembackbone repeater network.

Every mine, regardless of the ore being extracted, requires a good water supply as part of the treatment process.Convenient and accessible underground water table locations are often located several kilometres from the actualmine site where the ore deposit is mined and processed. Traditional labour intensive methods for manual operationto start and stop underground water pumps are not economic or sufficiently reliable for the 24 hour processoperations that most mine sites run. Some convenient method of monitoring and controlling the remote electricalequipment is required. With little or no telecommunications infra-structure such as telephone services beingavailable and with distances in the 10-20km range making laying cables or fibre optic uneconomic radio offers areliable and convenient way of enabling this monitoring.

Several remote underground water bores are used to extract water into a feeder pipeline then into a dam storagearea at the mine site. At each bore the flow rate is monitored via a 4-20mA current loop from a flow meter andtransducer. The digital status of the pump running, fault, remote selection and ready status is monitored directly bythe RTU digital IO interface. The control of the pump from start initiation, whether from the plant control systemor locally via manual operator action, is controlled by the logic internal to the AD2000 RTU. This allows local lowflow monitoring and tripping to be programmed to suit the local conditions with variable low flow timer delays.Flow totalisation is also possible via pulse inputs or accumulation of analogue flow rates.

All the status and control points are then fed into a plant control PLC (in this case an GE Fanuc 90-30 PLCs)which are then made available to the plant operator interface.

8.0 SUMMARY

This paper has hopefully presented a brief overview of radio-based technologies and their suitability to SCADAnetworks.

There are literally thousands of proven radio based installations in operation throughout the country. Thispresentation obviously does not allow enough time to fully explore all the systems currently in place or theircapabilities and benefits.

It has hopefully highlighted the many benefits of radio based SCADA networks and shown potential users whatvarying solutions are available.

The selection of any radio-based solution is dependent on the network and will ultimately dictate the flexibility,performance and running costs. It is thus very important to scope out the requirements and potential futureexpansions before locking oneself into any particular communications medium.

45943119 SCADA Communications Systems Using Radios

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