SCADA Uses Radio
`to Bridge the Gap
`
`Bill Greeves
`
`The concept of radio telemetry is
`bringing about cost and efficiency
`benefits in the water supply industry –
`enabling effective monitoring and
`communications from a wide variety of
`points and increasing the capabilities of
`SCADA and DCS.
`Essentially, radio telemetry is a
`means of communication without the
`existence of a physical connection
`between the transmitter and the
`receiver. It can, for example, be used as
`a replacement for a physical link where
`difficult terrain or natural obstacles
`militate against such a link, or where
`the transmitting or receiving end is in
`motion and the attachment of a physical
`link is impossible.
`Radio telemetry is ideal for industries
`such as water supply and treatment,
`where multi-locational sites requiring a
`sophisticated communications network
`are commonplace. Radio’s high
`integrity and the possibility to
`incorporate shutdown systems provide
`an ideal solution, and it is relatively
`cost-effective when compared with
`other physical links.
`Although ideally a radio link should
`be “transparent” – that is to say, act as if
`it were not present and impose no
`constraints on the data speed or content
`– this is rarely possible owing to the
`physical problems encountered and the
`specifications under which these
`systems must work. The main limiting
`factor in the use of radio telemetry is
`distance – and the distance to be
`covered defines the type of radio
`telemetry system applied and the
`frequency used.
`
`The Behaviour of Radio
`Radio waves are electromagnetic waves
`consisting of an electric field and a
`magnetic field at right angles which
`will propagate in a vacuum. All
`electromagnetic waves travel at almost
`
`three million metres per second; their
`frequency and wavelength are inter-
`related and represented by V = F · W ,
`where F = the frequency, W = the
`wavelength and V = the speed of light
`(3 · 108 metres/second). All that
`distinguishes one type of wave from
`another is the frequency. As the
`frequency changes, so do the properties
`and behaviour of the wave and, due to
`the range of frequencies in the
`electromagnetic spectrum, there are
`large differences in this behaviour – it
`can, to a large extent, be defined by the
`way in which electromagnetic radiation
`interacts with solid matter. The
`differences in the way that radiation of
`various frequencies penetrates or
`reflects at the surfaces of different
`materials is an example.
`The two important allocations for
`low-power radio telemetry are at
`173MHz (VHF) and 458MHz (UHF),
`corresponding to the wavelengths of
`
`1.70 and 0.66 metres respectively.
`These unlicensed bands were allocated
`in 1987 following DTI deregulation.
`Radio telemetry using the VHF band, at
`1mW (or 10mW with licence) effective
`radiated power (ERP), is applicable to
`about 1 kilometre and in line-of-sight
`conditions. The UHF band, at up to
`500mW of power ERP, will cover
`distances of about 10-15 kilometres,
`dependent on the terrain.
`The two bands are far enough away
`from each other to exhibit some
`differences in behaviour. In general, the
`lower the frequency, the less the wave
`will attenuate or weaken when
`travelling over ground. This effect is
`even more pronounced when travelling
`through foliage with the lower
`frequency wave attenuating much more
`slowly with distance.
`Reflection and refraction also affect
`the behaviour of radio waves when
`transmitting above 500 metres;
`
`Bristol Babcock’s Spacenet 3000 control and command station with Enterprise workstation and
`products from Bristol Babcock’s Network 3000 process control range
`
`Sensor Review, Vol. 14 No. 2, 1994, pp. 00-00, © MCB University Press, 0260-2288
`
`SR Vol. 14 No. 2, 1994 31
`
`IPR2015-01973
`SIPCO, LLC
`Exhibit 2004
`
`

`
`SCADA Uses Radio
`to Bridge the Gap
`
`Bill Greeves
`
`The concept of radio telemetry is
`bringing about cost and efficiency
`benefits in the water supply industry –
`enabling effective monitoring and
`communications from a wide variety of
`points and increasing the capabilities of
`SCADA and DCS.
`Essentially, radio telemetry is a
`means of communication without the
`existence of a physical connection
`between the transmitter and the
`receiver. It can, for example, be used as
`a replacement for a physical link where
`difficult terrain or natural obstacles
`militate against such a link, or where
`the transmitting or receiving end is in
`motion and the attachment of a physical
`link is impossible.
`Radio telemetry is ideal for industries
`such as water supply and treatment,
`where multi-locational sites requiring a
`sophisticated communications network
`are commonplace. Radio’s high
`integrity and the possibility to
`incorporate shutdown systems provide
`an ideal solution, and it is relatively
`cost-effective when compared with
`other physical links.
`Although ideally a radio link should
`be “transparent” – that is to say, act as if
`it were not present and impose no
`constraints on the data speed or content
`– this is rarely possible owing to the
`physical problems encountered and the
`specifications under which these
`systems must work. The main limiting
`factor in the use of radio telemetry is
`distance – and the distance to be
`covered defines the type of radio
`telemetry system applied and the
`frequency used.
`
`The Behaviour of Radio
`Radio waves are electromagnetic waves
`consisting of an electric field and a
`magnetic field at right angles which
`will propagate in a vacuum. All
`electromagnetic waves travel at almost
`
`three million metres per second; their
`frequency and wavelength are inter-
`related and represented by V = F · W ,
`where F = the frequency, W = the
`wavelength and V = the speed of light
`(3 · 108 metres/second). All that
`distinguishes one type of wave from
`another is the frequency. As the
`frequency changes, so do the properties
`and behaviour of the wave and, due to
`the range of frequencies in the
`electromagnetic spectrum, there are
`large differences in this behaviour – it
`can, to a large extent, be defined by the
`way in which electromagnetic radiation
`interacts with solid matter. The
`differences in the way that radiation of
`various frequencies penetrates or
`reflects at the surfaces of different
`materials is an example.
`The two important allocations for
`low-power radio telemetry are at
`173MHz (VHF) and 458MHz (UHF),
`corresponding to the wavelengths of
`
`1.70 and 0.66 metres respectively.
`These unlicensed bands were allocated
`in 1987 following DTI deregulation.
`Radio telemetry using the VHF band, at
`1mW (or 10mW with licence) effective
`radiated power (ERP), is applicable to
`about 1 kilometre and in line-of-sight
`conditions. The UHF band, at up to
`500mW of power ERP, will cover
`distances of about 10-15 kilometres,
`dependent on the terrain.
`The two bands are far enough away
`from each other to exhibit some
`differences in behaviour. In general, the
`lower the frequency, the less the wave
`will attenuate or weaken when
`travelling over ground. This effect is
`even more pronounced when travelling
`through foliage with the lower
`frequency wave attenuating much more
`slowly with distance.
`Reflection and refraction also affect
`the behaviour of radio waves when
`transmitting above 500 metres;
`
`Bristol Babcock’s Spacenet 3000 control and command station with Enterprise workstation and
`products from Bristol Babcock’s Network 3000 process control range
`
`Sensor Review, Vol. 14 No. 2, 1994, pp. 00-00, © MCB University Press, 0260-2288
`
`SR Vol. 14 No. 2, 1994 31
`
`

`
`reflection occurs from solid objects
`such as buildings, and refraction can
`occur over hill tops, for example. It is
`unusual for only one wave to be
`received from a transmitter: usually
`there is a direct wave and a number of
`others arriving slightly later after
`having been reflected (this is known as
`multipath transmission). A pronounced
`form of this effect takes place over
`water, for example, between two hills
`or across a lake. The effect is to produce
`a dead zone where there is phase
`cancellation between the incoming
`signals. If the various waves arriving at
`the antenna are more or less equal in
`amplitude
`then summation or
`subtraction can occur. Moving an
`antenna only a small distance at these
`frequencies can shift it from a null to a
`peak, i.e. from a position where arriving
`waves cancel to one where they add.
`Owing to the shorter wavelength, this
`effect is more pronounced at UHF than
`at VHF, and the nulls and peaks are
`much closer to each other.
`High power radio telemetry at
`distances greater than 20 or so
`kilometres can also be affected by
`atmospheric fading and the effect of
`earth curvature.
`
`Frequency Modulation
`A plane radio wave carries no
`information – all that it can indicate is
`its presence or otherwise. With low
`power telemetry, frequency modulation
`(FM) is used to impress information
`onto the “carrier” radio wave. The
`frequency of the carrier is varied in
`proportion to the amplitude of the data.
`At the receiver end, the original signal
`is detected or “demodulated”.
`All data transmitted in radio
`telemetry is digital – all analogue inputs
`are converted into a digital form before
`transmission. Therefore the process of
`modulation is used to impress two
`states on the carrier. With FM, the
`modulated carrier will be moved
`(deviated) between two frequencies,
`each corresponding to a logic state.
`
`Transmitting and Receiving
`All radio waves have a specific
`frequency and wavelength, and most
`antenna designs and dimensions for
`UHF and VHF depend entirely on the
`wavelength at which the antenna –
`either omni-directional or directional –
`is to operate. The antenna building
`blocks consist of “elements” which are
`quarter- and half-wave long and are
`dimensioned to be resonant at the
`frequency in use. (A resonant antenna
`
`literally “rings” at the frequency for
`which it has been made.) Where an
`omni-directional antenna is required –
`such as a base station with a number of
`“slave” stations around it – a single
`vertical element could be used or a
`vertical co-linear. The “slave” stations,
`which only need to communicate with
`the base, would use directional
`antennas.
`At resonance, the antenna will
`present a predictable impedance at its
`feed point, an important factor on the
`transfer of energy in either direction.
`This “input impedance” is not
`measurable by normal instruments as it
`only exists at the design frequency of
`the antenna. Any connection made,
`must, therefore, be at the same
`resistance level.
`Where very short ranges are required,
`small plug-in-antennae can be mounted
`directly on the case of transmitters or
`receivers. The connection of
`transmitters or receivers to antennae is
`via a coaxial feeder cable designed to
`its “characteristic impedance”, and
`where such a cable is connected to an
`antenna of the same impedance, there
`will be maximum power on
`transmission and maximum sensitivity
`on reception (for example, a 50 ohms
`antenna and a 50 ohms cable).
`Generally speaking, for the best
`possible results, antennae should be
`mounted as high as possible and with as
`clear a field of view in the direction
`which it is pointed as is practical.
`Raising antenna height can produce an
`improvement in signal strength out of
`all proportion to the amount of increase
`in height. It should also be remembered
`that the beam widths of antennae used
`are quite wide – for example, a metal
`tower well off to one side of a
`transmission path may create a potent
`secondary path signal. The possibility
`of this effect will be increased with
`omni-directional antennae.
`
`Radio Equipment
`Radio equipment for low power radio
`telemetry in the UK has to meet
`specifications developed under DTI
`auspices. Transmission on the two
`prescribed low power bands does not
`require a licence.
`MPT 1328, the specification
`covering
`the VHF band from
`173.200MHz to 173.350MHz, allows
`for five channels of 25kHz or 11
`channels of 12.5kHz. 173.225MHz is
`reserved for alarm purposes and should
`not be used for telemetry. The transmit
`output power is limited to 1mW, but in
`special circumstances this may be
`
`raised to 10mW if a licence is obtained.
`This band enables low power radio
`telemetry up to 1 km line of sight, and is
`generally used in plant monitoring.
`MPT 1329 is the specification
`covering the UHF band from 458.500
`to 458.800MHz affording 11 channels
`at 25kHz or 23 channels at 12.5kHz.
`The maximum transmit power is
`500mW, giving a considerable increase
`in range – up to 10-15km.
`High power radio telemetry is
`achievable under the MPT 1411
`specification, covering the frequency
`range 457.5 to 458.5 and 463.0 to
`464.0MHz, although licences always
`have to be obtained for these
`frequencies and are issued on a site-by-
`site basis with a power limit decided by
`the DTI.
`Radio telemetry applications in
`countries other than the UK are subject
`to the regulations pertaining to each
`individual country.
`
`Low Power Radio Telemetry
`in Process Control
`Applications
`Radio telemetry interfaces with process
`control systems such as supervisory
`control and data acquisition (SCADA)
`and distributed control systems (DCS),
`and can greatly increase their power
`and efficiency. Its benefits over physical
`links include higher integrity and
`incorruptibility (a radio link cannot be
`dug up or drilled through, for example),
`ease of set-up and operation and greater
`cost-effectiveness.
`Each location within a radio
`telemetry system will be given its own
`“identity” and be identified by a unique
`number. In process control terms, the
`simplest radio telemetry system is a
`“one-way” system, where a group of
`outstations are equipped with radio
`transmitters. At random intervals, each
`will transmit its data to a master station
`equipped only with a receiver. Each
`data package consists of the information
`to be transmitted plus the identity of the
`outstation. The possibility of
`transmission clash, i.e. where two or
`more outstations transmit at the same
`time, can be avoided by making the
`intervals between each transmitter’s
`transmissions different. In practical
`terms, no more than about eight
`outstations should be included in a one-
`way system.
`More commonplace are two-way
`systems, where individual outstations
`are “polled” in turn by the master
`station. The master station will issue a
`request which contains the identity of
`the station to be interrogated and only
`
`32 Sensor Review
`
`

`
`Shearway
`
`Hills
`
`Drellingore
`
`H
`
`Cherry gardens
`
`Saltwood
`
`Paddlesworth
`
`Farthing C
`
`H
`
`Chalkshole
`
`H
`
`Lye Oak
`
`Ottinge
`
`Worlds W
`
`Key:
`
`Master station
`
`Pseudo-master staion
`
`Bidirectional path
`
`Uni-directional path
`
`H
`
`Rakes N
`
`Rakes S
`
`Tapp S
`
`Denton
`
`Tapp N
`
`Figure 1. Communications Strategy: Schematic for Folkestone and Dover Water Services Radio Telemetry Installation
`
`that one will respond. With this type of
`system, the flow of data can be two-
`way and thus the master station can be
`used to control events at the outstations.
`It can also be arranged that one
`outstation can communicate with
`another via the master.
`RS232 cable links can also be
`replaced with a radio link operating in
`half duplex mode (i.e. only transmitting
`or receiving at any one time). The
`RS232 cables can be replaced with two
`radio modules, one at each end, with no
`software configuration necessary on the
`main
`system. These modules
`communicate with each other and, as all
`necessary communication protocols are
`managed by the microprocessors in the
`units, the operation is transparent to the
`host system.
`Large scale and sophisticated
`SCADA systems – such as those in the
`water services
`industry – can
`incorporate
`complete
`regional
`telemetry schemes, controlling a
`number of sites over distances of many
`kilometres. A central control station
`could be linked by land lines to
`“intelligent clusters”, each comprising
`a “gateway” station linked by radio to a
`number of outstations. All information
`can be viewed at the central control
`station which communicates with the
`“gateway” station, which in turn
`communicates with the outstations in a
`distributed monitoring system. An
`alarm at, for example, a reservoir
`outstation, will alert the “gateway”
`station which in turn will alert the
`
`central control. In such a system, radio
`telemetry is the main form of
`communication.
`A major benefit of radio telemetry is the
`ability to provide a “shutdown” facility.
`A “dual redundant” radio system will
`comprise two radio links; if one fails,
`the system will automatically switch
`over to the other radio link.
`Bristol Babcock Ltd, part of the FKI
`group of companies, is a market leader
`in the provision of radio telemetry
`systems within the water industry and
`has its own in-house radio telemetry
`expertise. The company was chosen to
`supply a radio telemetry system for
`Folkestone and Dover Water Services
`after a pilot area of 6km2 – comprising
`a master station and 22 wells – was
`tested, resulting in an estimated cost
`ratio of 3:1 in favour of radio telemetry
`against cabling and fibre optics.
`Folkestone and Dover Water Services
`then ran the system for two years to
`verify cost savings, expectation and
`monitor system reliability; and decided
`
`to introduce low power radio telemetry
`systems throughout its central area for
`data collection and control links.
`The telemetry equipment had to
`interface with existing Square D PLCs
`and used Spacenet 232 radios –
`designed to replace RS232 cable links
`but which can, with a special interface,
`also replace RS422 links. The system
`used UHF radio links conforming to
`MPT 1329. The PLCs on the Folkestone
`and Dover Water central area relay data
`to and from the master station located at
`Shearway, provide local control at each
`outstation and act as data collection
`points for onward transmission.
`Twenty-three stations are covered and
`the telemetry links have a required
`range of 12km in all directions. The
`area is split into zones, each of which
`has a pseudo master station to control
`the zone. Configured in this manner, the
`network can perform data exchange at
`five levels from the furthest station to
`the master.
`
`Spacenet 3000
`
`Spacenet 3000
`
`I/O
`
`I/O
`
`Figure 2. Point to Point Network using Spacenet 3000
`
`SR Vol. 14 No. 2, 1994 33
`
`

`
`The transmitted data provides
`information on reservoir levels, flows,
`pressures, treatment parameters and
`general plant status. Control activity is
`concerned principally with pumping
`plant, with level controls from
`reservoirs being incorporated in the
`near future.
`
`Versatility of Radio Telemetry
`The development of radio telemetry in
`process control applications has been
`closely linked to the water supply and
`treatment industries, but the technology
`is applicable to a number of areas.
`Burgeoning environmental regulations
`on the chemicals industry, for example,
`highlight the use of radio telemetry in
`the monitoring of effluent output at a
`number of distant locations. The power
`generation industry is finding radio
`telemetry increasingly effective,
`particularly
`in
`hydroelectric
`installations.
`Overseas, Bristol Babcock has been
`contracted to install a radio telemetry
`system for the Vietsovpetro Project, a
`joint Russian and Vietnamese venture
`comprising seven oil platforms in the
`“White Tiger” field, 120 miles off the
`Vietnamese coast. The system transmits
`voice and data communication between
`the master platform and its six satellite
`platforms, and transmits over two
`different frequencies (UHF and VHF
`bands) to overcome the problem of
`signal fading owing to the varying level
`of the sea. The aerials are also mounted
`at different heights for space diversity,
`and both data frequencies operate
`concurrently to overcome any start-up
`delay owing to one frequency fading.
`As control systems become more
`complex and sophisticated, the role of
`radio telemetry is set to grow. Its cost-
`effectiveness – especially in the UK
`where a low power radio telemetry
`network needs no licence to set up –
`together with its benefits of high
`operational integrity and installation
`expertise, mean that the technology can
`help to expand and improve com-
`munications in an increasing number of
`industries.
`Further information from Helen
`Hyams, Bristol Babcock Ltd, Vale
`Industrial Estate, Stourport Road,
`Kidderminster, Worcs, DY11 7QP. Tel:
`0562 820001; Fax: 0562 515722.
`
`Bill Greeves is a Senior Sales Engineer
`with the RF Department of Bristol Babcock
`Ltd. Bristol Babcock Ltd, is a subsidiary of
`FKI plc, UK.
`
`34 Sensor Review
`
`Spacenet 3000
`
`I/O
`
`Spacenet 3000
`
`I/O
`
`Spacenet 3000
`
`I/O
`
`Figure 3. Point to Point with Multiple Slave Nodes
`
`Spacenet 3000
`
`I/O
`
`Spacenet 3000
`
`I/O
`
`Spacenet 3000
`
`I/O
`
`Spacenet 3000
`
`/O
`
`Highway
`
`DPC 3300
`
`I/O
`
`Figure 4. Single or Multiple Slave Nodes with a Bristol Babcock Network 3000 Master
`
`Spacenet 3000
`
`I/O
`
`Spacenet 3000
`
`I/O
`
`Spacenet 3000
`
`"MODBUS" protocol
`
`Highway
`
`PLC
`
`I/O
`
`I/O
`Figure 5. Single or Multiple Slave Nodes with a Third Party PLC or DCS Controller