Final Plan Wlan

7/31/2019 Final Plan Wlan

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Document type:

plan

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The Ika/Ida/Irina and Ana/Vesnadata communications

Book: 1Ver.: 05.12.

Komteh

Document Nr: 13-12PLAN

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Plan for the SCADA WLAN communicationson the Ika, Ida, Irina, Ana, Vesna and Ivana platforms

Zagreb, May 2012.


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Summary

This document encompasses a plan for implementing a WLAN system among the Ana/Vesna/Ivana-Aand Ika/Ida and Irina platforms.

The document contains seven chapters:

Chapter 1 analyze existing situation.

Chapter 2 describe a generic WLAN system architecture applicable to platforms duty.

Chapter 3 treat radio propagation matters.

Chapter 4 explain a WLAN system issue specific to Ana/Vesna/Ivana-A platforms.

Chapter 5 concerns with particulars of WLAN connections between the Ika/Ida/Irina platforms.

Chapter 6 contain a planed installation procedure which could minimize SCADAcommunications break duration.

Chapter 7 contain Bill of expenses.

1. Existing situation

The existing RTUs (Remote Terminal Unit) on the Ika/Ida/Irina and Ana/Vesna/Ivana platformscommunicate via UHF radio modems utilizing the Modbus device emulation at DTE/DCE interface andproprietary over the air protocol.

In principle, communications performances are acceptable, but because of the low data rate,throughput is quite low causing fairly slow SCADA update cycle.

Further, since the present radio-modems operate in non transparent Modbus emulation mode, thesystem is error prone, i.e., suffering a sporadic out of sequence RTU responses, as describedelsewhere

1.

Both deficiencies cause additional workload and annoyance to the control room operators.

Even neglecting mentioned problems, a limited data transfer capacity is huge system inadequacy.Because of it, precluded are any increases in the data traffic volume and/or extra connections, e.g.,additional data ports. Simply, this is not feasible because already sluggish pooling cycle could becomeintolerably slow.

Only sensible way for described data communications inadequacy elimination is switching over to thehigh throughput WLAN type of radio communications.

As from September 2011 the WLAN test system is provisionally installed and commissioned on theAna, Vesna and Ivana-A platforms. Mentioned system was temporary coupled in instead of the UHFradio-modems. So far system operates flawlessly

2despite to some extent improvised and non

redundant installation.

1Final report 01/09:

Odd malfunction within the UHF radio modems communication system2

TR12/11 Technical report:Ana, Vesna and Ivana platforms Modbus communications through the Wireless Local Area Network (WLAN)


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2. Generic architecture of the planed WLAN system

Basically, WLAN (Wireless Local Area Network) system comprises AP (Access Point) equipmentsinstalled on the central platform and WLAN clients installed on the peripheral platforms. These WLANunits are continuously in radio connection thus capable of carrying a MOBUS data if and whennecessary. This allows prompt MODBUS data traffic since the MODBUS master and all MODBUS

slaves are permanently connected via the WLAN AP and WLAN clients, respectively.

As looking from a central platform, peripheral ones positions usually are not on same bearing, thecentral platform antenna system most radiate in right directions. Generally this call for a multi antennasystem because a wide beam width antenna do not have sufficient gain. Consequently the WLANinstallation on central platform could include a two or more high gain directional antennas.

Simplified block schematic of the planed WLAN system applicable to a MODBUS master-slave typecommunications is depicted below.

Picture 1 Generic WLAN system block schematic

Ethernet

CENTRAL PLATFORM

MODBUS

master

MODBUS/TCPconverter

WLAN IDU

PERIPHERAL PLATFORM 2.

EthernetWLAN IDU

MODBUS/TCP

converter

MODBUS slave

(RTU)

PERIPHERAL PLATFORM 1.

EthernetWLAN IDU

MODBUS/TCPconverter

MODBUS slave

(RTU)

2 channel radio ODU

Radio ODU

Radio ODU


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Functional description of the illustrated WLAN system could be as follows:

The MODBUS master regularly turns out requests addressed to the MODBUS slaves. Requests aregenerated according to the MODBUS serial RTU protocol. Because such serial data stream is notsuitable for WLAN operation, requests are feed to the MODBUS/TCP converter where it undergonealteration to the Ethernet protocol. Products are a MODBUS-TCP data packets which are guided to one

port of a WLAN IDU (In Door Unit). The IDU contain a number of devices, e.g., a PSU, Ethernet switch,voltage surge protection, etc., all together securing proper working environment for an actual WLANradio, i.e., an ODU (Out Door Unit). The ODU is connected to the IDU I/O port via Ethernet POE (PowerOver Ethernet) cable. Beside power, this cable carries bidirectional Ethernet traffic to and from theWLAN ODU.

Since, as seen from the central platform, peripheral platforms are not necessary on same azimuth, theAP must radiate/receive in more than one direction. Because of this, here in illustrated two directioncase, the ODU is provided with pair of radio cards. Each is connected to the suitably oriented antennaenabling two antennas operation without use of a RF power splitter.

In operation, actual transmission signal is generated by the one radio card only; the one which is, duringthe system initialization phase, detected as best serving the addressed RTU, i.e., the particular platformdirection.

Normally, signal transmitted by the central platform AP is received by the antenna and the ODU on theaddressed platform as shown on right hand side of the picture 1. Here signal goes in reverse directionthru already described process, i.e., from antenna to a radio card within the ODU, then via IDU to theMODBUS/TCP converter. At this point the MODBUS-TCP packets are converted back to the serialMODBUS format and, in turn, feed to the MODBUS slave in reality a MODBUS RTU.

A response generated by the RTU, if any, is transferred in opposite direction by almost identicalprocess. Only differences are on the peripheral platforms, where exist only single ODU radio card andantenna. This is sufficient because peripheral platforms need radio connection in one orientation only,i.e., with the central platform.

Here must be noted that, for clarity, the illustration and system description above do not includeredundancy. Obviously, in order to achieve greatest possible reliability, a real system should compriseredundancy. Most practical way to acquire it is to duplicate everything consequently forming a WLAN

1+1 system.

3. Radio subsystem consideration

3.1 Radio licence and operating frequencies

The future WLAN system should operate in accordance with a HAKOMs general radio licences.Related licences are OD-16 and OD-87 permitting operation in frequency band around 2400 MHz or 5.5GHz on RF EIRP level of 20 or 30 dBm, respectively.

Coverable distance is nearly the same for both frequency ranges and power levels; nevertheless, 5.5GHz band had slight advantage because of intrinsically lower probability of RFI (Radio FrequencyInterference) from other ISM (Industrial Scientific Medical) device, e.g., Bluetooth, Microwave oven,

etc., and smaller, i.e., more robust, antennas.

3.2 Communications range and link availability

Since planed WLAN require a radio communications over relatively long distances, high gain antennasare mandatory. Regrettably, high gain antennas cold only helps in receiving route as allowed EIRP(Effective Isotropic Radiated Power) is limited by the mentioned radio licences. This means thattransmitter RF output power must be reduced to level which ensures low enough EIRP. Because of this,in order to guarantee sufficient radio communications link availability, RF loss on receiving path shouldbe minimized. This demand split configuration of WLAN equipments. Such configuration permits fittingan ODU radio close to antennas thus allowing use of a very short, almost lossless, antenna feedercable.

The antenna gain should be sufficient to guarantee minimal link availability of 99.5% of time. This is

more than enough considering current 10% MER (Message ErrorRatio), i.e., 90% time availability ofthe existing UHF system.


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3.3 Antenna placement

As mentioned afore, quasi-random positions of platforms necessitate more than one antenna on thecentral platform. Further, redundancy requirement easy could double antennas quantity. Because ofthis, determining antennas placement is not simple as various conditions should be fulfilled. Mostimportant are:

Antenna location must be outside of Ex danger zoneAntenna location should have unobstructed view of the corresponding peripheral platform.

Microwave reflection from potential reflectors, including a sea surface, have to be avoided or inradio path calculation accounted for.

Preferred are antenna locations accessible from within the platform railing.

4. WLAN specific for the Ivana-A, Ana and Vesna platforms group

4.1 The Ivana-A part of WLAN

The Ivana-A part of a planned WLAN system is depicted below.

Picture 2 The Ivana-A part of the WLAN system

Functional description of the WLAN system central part, illustrated on the picture 2, could be as follows:

The SCADA software regularly generates requests addressed to the MODBUS slaves situated on theAna and Vesna platforms. Actually, requests are originated according to the MODBUS/TCP protocol byA and B SCADA servers. Generated Ethernet data packets are guided to the respective ports of thedual WLAN IDU A+B. This IDU is fully 1+1 configured equipment containing pair of PSUs, twoEthernet switches, pair of voltage surge protection units, etc. Each ODU is connected to the own part ofIDU by Ethernet POE cables. These cables carry Ethernet traffic and power to the radios, i.e., the Aand B outdoor unit.

IVANA-A PLATFORM

MODBUS-TCP

Direction Ana2 channal ODU 'B'

Direction Vesna

SCADA server 'B'

MODBUS-TCP

DUAL WLAN IDU 'A+B'

Direction Ana2 channal ODU 'A'

Direction Vesna

SCADA server 'A'


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As mentioned previously, peripheral platforms are on different azimuths which require two antennasoperation on the Ivana-A platform. In order to enable splitter-less double antenna operation, each ODUis provided with pair of radio cards. Obviously, individual card is connected to the suitably orientedantenna.

Whole configuration act as fully redundant WLAN AP system enabling Ethernet communications

between peripheral platforms RTUs and the SCADA servers via A and B subsystem concurrently.Within both ODUs, actual transmission signal is generated by the one radio card only; the one which is,during the system initialization phase, recognized as best serving the addressed RTU, i.e., theparticular platform direction.

4.2 The Ana (Vesna) part of WLAN system

The Ana (Vesna) part of a planned WLAN system could be seen on the picture 3.

Picture 3 The Ana (Vesna) part of the WLAN system

Functional description of peripheral part of the WLAN system illustrated on the picture 3 could be asfollows:

Signal transmitted by the central platform is received by, at least one, ODU on the addressed platform.Here signal goes in reverse direction through already described process, i.e., from antenna to a radiocard within the ODU, then via IDU to the MODBUS/TCP converter. At this point the MODBUS-TCPpackets are converted to the serial MODBUS format and, in turn, feed to the MODBUS slave in reality

the MODBUS RTU.

Since system is redundant, actual path of the receiving signal is inconsequential, as long as at least oneis successful. In other words, a duplicate data are ignored.

A response generated by the RTU, if any, is transferred in opposite direction by process almostidentical to described in 3.2. Ignoring redundancy, differences here are existence of only one antenna

ANA (VESNA) PLATFORM.

MODBUS/TCPconverter 'A'

Direction Ivana-A

Ethernet

WLAN IDU 'A'

MODBUS slave

RTU 'A'

Radio ODU 'A'

Direction Ivana-A

Ethernet

WLAN IDU 'B'

MODBUS slaveRTU 'B'

Radio ODU 'B'

MODBUS/TCPconverter 'B'


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and radio card. This is sufficient because both peripheral platforms need radio connection in oneazimuth only, i.e., to/from the Ivana-A platform.

4.3 Antennas for the Ana Ivana-A and Vesna Ivana-A link

4.3.1 The platforms bearing and distances

Regarding the Ivana-A platform as central, bearing and distance to other platforms are as follows:

Ivana-A antenna azimuth Platform Antenna azimuth Distance Latitude N ( ) Longitude E ( )

198.37 Ana 18.35 7.32 km 44 40 56.52 013 15 53.45169.65 Vesna 349.66 6.55 km 44 41 13.51 013 18 47.80

4.3.2 Antenna installation

The Ana, Vesna and Ivana-A links have to be more permanent version of the present test system. Tothis end, on the peripheral Ana and Vesna platforms, the existing UHF antennas and antenna feedercoax should be replaced with new WLAN antennas and Ethernet cables. This will enable utilization ofthe existing support structure and cable trays for new WLAN antennas.

On the Ivana-A platform situation is little more complicated because antenna placement is stipulated byneed for minimizing sea surface reflection influence on received signal quality. Since antenna height onperipheral platform is already fixed, antenna height on central platform should be set to specific valuewhich will minimize a signal loss caused by reflection from sea surface.

Using the microwave link planning program3

the reflection loss could be calculated. Diagram on picture4 represent the Ana link relative signal strength as function of tide level.

Picture 4 The Ana link reflection loss curve

Clearly, the minimum losses coincide with horizontal part of the loss tide level curve, which happenson antenna height of 31.4 m ASL. Clearly, installing an antenna at this height should eliminate reflectionloss throughout all possible tide level, e.g., from 1 to + 1 meter.

Similar reasoning applies also for the Ivana-A Vesna link. A reflection loss tide level curve for thislink is shown below (Picture 5).

3http://www.pathloss.com/p4/index.html

RelativeReceiveSignal(dB)

Tide (m)5.0-5.0 -4 -3 -2 -1 0 1 2 3 4

-16

-14

-12

-10

-8

-6

-4

-2

0

2

4

H1=31.3 m, H2=23.0 m, K=1.33, F=2400.0 MHz, V


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Picture 5 The Vesna link reflection loss curve

Analogously with aforesaid consideration, the Ivana-A antenna for the Vesna link ought to be installed

on height of 28 m ASL exactly.

Naturally, antennas must be placed on south side of the Ivana-A platform thus ensuring unobstructedview of the peripheral platforms.

5. WLAN specific for the Ika, Ida and Irina platforms group

5.1 The Ika-A part of WLAN

Referencing picture on the next page, functional description of Ika-A part of the WLAN system could beas follows:

The SCADA software running on pair of the personal computers situated on the Ika-A platform,

regularly generates requests to the MODBUS communications PLCs. This PLCs, also installed on theIKA-A platform, act as MODBUS masters for all communications with MODBUS slaves located on allplatforms.

Requests are originated by the A and B SCADA PCs respecting the serial MODBUS RTU protocol.Because such serial format is not suitable for WLAN operation, the requests are forward to theMODBUS/TCP converters for change to the Ethernet protocol and v.v. Conversion products are aMODBUS-TCP data packets which are guided to the corresponding ports of the both dual WLAN IDUs.Each of the dual IDU is connected to the respective ODUs via Ethernet POE cables. These cables carryEthernet traffic and power to the all ODUs, i.e., to the main A, as well as to redundant B radios.

Since, as seen from the Ika-A platform, peripheral platforms are on different azimuth requiring multiantenna operation, all ODUs is provided with two or three radio cards. Each card is connected to thesuitably oriented antenna enabling multi direction radiation without power splitter loss.

The whole configuration operates resembling fully redundant WLAN AP. This enable concurrent A andB WLAN communications between the SCADA PC and a slave RTUs.

Within all of ODUs, actual transmission signal is generated by the one radio card only; the one which is,during the system initialization phase, detected as best serving the addressed RTU, i.e., the particularplatform direction.

RelativeReceiveSignal(dB)

Ivana-A Antenna height (m)35.023.0 24 25 26 27 28 29 30 31 32 33 34

-4

-3

-2

-1

0

1

2

3

4

5

H2=23.0 m, K=1.33, F=2400.0 MHz, H


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Picture 6 The Ika-A part of the WLAN system

IKA-A PLATFORM

MODBUS-TCPMODBUS-TCP

1th Dual WLAN IDU 'A+B'

Direction Ika-B

Direction Ida-A

Direction Ika-B

Direction Ida-A

2 channal ODU 'B'

2 channal ODU 'A'

Direction Irina

Direction Ida-B

Direction Ida-C

3 channal ODU 'A'

MODBUS/TCPconverter A

MODBUS/TCPconverter B

MODBUS Communicationscontroller PLC

MODBUS-Serial data

SCADA PC 'A' SCADA PC 'B'

2th Dual WLAN IDU 'A+B'

Direction Irina

Direction Ida-B

Direction Ida-C

3 channal ODU 'B'


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5.2 The peripheral parts of the Ika/Ida/Irina WLAN system

Peripheral part of the planed WLAN system could be seen on the picture 7.

Picture 7 The peripheral part of the Ika/Ida/Irina WLAN system

Functional description of peripheral part of the WLAN system illustrated on the picture 7 is identical todescription already given in chapter 4.2.

5.3 Antennas for the Ika-A Ika/Ida/Irina links

5.3.1 The platforms bearing and distances

Regarding the Ika-A platform as central, bearing and distance to other platforms are as follows:

Ika-A antenna azimuth Platform Antenna azimuth Distance Latitude N ( ) Longitude E ( )

345.52 Ida-A 165.49 14.94 km 44 29 38.02 013 26 40.72

317.22 Ika-B 137.18 6.24 km 44 24 17.57 013 26 18.34

354.49 Ida-B 174.49 9.26 km 44 26 48.04 013 28 49.61

5.31 Ida-C 185.32 10.87 km 44 27 39.91 013 30 15.31

332.21 Irina 152.13 20.52 km 44 31 37.88 013 22 32.77

5.3.2 Antenna installation

On the peripheral Ika/Ida/Irina platforms, the existing UHF antennas must be removed and replacedwith new WLAN antennas. This way existing support structure will be utilized for the WLAN antennas

and Ethernet cable.On the Ika-A platform situation is little more complicated because antenna placement is stipulated byneed of minimizing sea surface reflection influence on received signal quality. Since antenna height onperipheral platform is already fixed, antenna height on central platform should be set to specific valuewhich will minimize a signal loss caused by reflection from sea surface.

Direction Ika-A

Ethernet

WLAN IDU 'B'

MODBUS slave

RTU 'B'

Radio ODU 'B'

MODBUS/TCPconverter 'B'

IKA/IDA/IRINA PLATFORM

MODBUS/TCPconverter 'A'

Direction Ika-A

Ethernet

WLAN IDU 'A'

MODBUS slave

RTU 'A'

Radio ODU 'A'


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Optimum antenna height is determined using the microwave link planning program4. A typical reflection

loss tide level curve could be seen on picture 4 or 5.

Using mentioned program and considering actual peripheral platforms antenna height, matching heightof the corresponding Ika-A antennas was calculated:

Peripheralplatform

Antennaheight (m ASL)

Matching height onthe Ika-A (m ASL)

Note

Ika-B 19.400 23.25 Existing antenna support structure useable

Ida-A 19.400 20.00 Existing antenna support structure useable

Ida-B 19.400 23.00 Existing antenna support structure useable

Ida-C 19.400 27.00 Installed on helideck fire fighting platform railing

Irina 23.000 23.00 Existing antenna support structure useable

Naturally, antennas must be placed on NW side of the Ika-A platform thus ensuring unobstructed viewof the peripheral platforms. Incidentally, the existing antenna support structure is situated on NW cornerof the platform.

6. Installation procedure consideration

The WLAN setting up activity must never jeopardize data communications between a central andperipheral platforms. Because of this requirement, during WLAN equipments installation, old UHFsystems have to remain in operation as long as possible. This implies carrying out installation work intwo step. Firstly, all of WLAN system elements should be installed and powered up, but withoutconnections to the rest of MODBUS structure. Following all necessary adjustment, e.g., presetting IPaddresses, MODBUS/TCP converter configuration, antennas direction adjustments etc., WLAN systemshould be utterly checked including by use of a PC based MODBUS master/slave emulators. Switchover to new system should be no earlier than successful MODBUS emulators test ran.

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