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RADIUS

 

 Product 

Description 

 

 

PDR221

 

 

iom_pdr221_04_r02.doc  

Rev 02 

Page 17 (60)

 

RSSI

0

0,5

1

1,5

2

2,5

3

-130 -120 -110 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10

dBm

V

 

7.6  RSSI – Received Signal Strength Indication 

The RSSI value can be used to determine the quality of a radio link. The RSSI values can be 
retrieved by executing the Radio Link Test in the configuration menus, see 12.8.6. 
 
The PDR 221 measures the RSSI value using an A/D converter. The received signal strength is 
measured in volts and is translated to a dBm value. 
 
The graph below shows a typical RSSI voltage value as a function of the signal level. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Figure 1. RSSI 

Summary of Contents for PDR221

Page 1: ...Packet Data Radio Installation Operation Manual PDR221 RADIUS RADIO NETWORK TECHNOLOGY ...

Page 2: ..._____________ 25 8 6 Radio Link Test ________________________________________________________________ 25 8 7 Split transmitting and receiving frequencies __________________________________________ 26 8 8 Split Tx Uplink Frequency ________________________________________________________ 27 8 9 Repeating Alternative Systems ____________________________________________________ 27 9 Installation______...

Page 3: ...__________________________________________________________________50 12 9 Advanced __________________________________________________________________ 51 12 9 1 Detected Radio Type _________________________________________________________________51 12 9 2 Rx Frequency _______________________________________________________________________51 12 9 3 Tx Frequency ______________________________________...

Page 4: ...2004 12 14 Approved Anders Grahn Template revision 01 001024 Revision Date Updated by Amendment 01 2004 10 14 Arto Valtonen First revision 02 2004 12 14 Arto Valtonen Second revision spelling correction and correction of system example 1 1 1 RADIUS Contact Information RADIUS US Inc 10700 W Venture Drive Unit B Franklin WI 53132 USA Phone 1 414 427 7010 Fax 1 414 427 7015 Email support radius us co...

Page 5: ...a features of the PDR221 Chapter 8 describes how the PDR221 features can should be used Chapter 9 contains installation guidelines including the serial interface Chapter 10 contains information about radio network accesories provided by Radius Chapter 11 gives an introduction to general antenna and radio technique and calculations This chapter is inteded for those who want to learn more about thos...

Page 6: ... The PDR221 is suitable for both polled and unsolicited systems For unsolicited systems there is Collision Avoidance functionality built in to the radio that virtually eliminates in air collisions vastly speeding up the communication throughput It is also possible to carry out Peer To Peer communication The radio communication is completely packet switched but the serial data is not buffered befor...

Page 7: ... benefit afforded by their wireless technology Our products are a result of the close relationship with our customers and partners and reflect the current and future needs of the market Examples of why to go wireless Replacing a cable in situations where installation of a cable is difficult expensive or even impossible Replacing a dial up link to reduce costs Network provider independence Example ...

Page 8: ... Examples of Typical Application Networks 3 1 1 1 Point to Point 3 1 1 2 Point to Multipoint PDR PLC RTU or other devices Control System PDR PLC RTU or other devices Control system PLC RTU or other devices PLC RTU or other devices PLC RTU or other devices PLC RTU or other devices ...

Page 9: ...RADIUS Product Description PDR221 iom_pdr221_04_r02 doc Rev 02 Page 9 60 3 1 1 3 Water Wastewater Network PDR Reservoir PDR Waste water plant Control system Pump house Water treatment plant ...

Page 10: ...RADIUS Product Description PDR221 iom_pdr221_04_r02 doc Rev 02 Page 10 60 3 1 1 4 Electrical Distribution Network Control system Capacitor switch Substation Recloser Metering points Substation ...

Page 11: ...ions Adjacent channel rejection 60dB Serial Interface RS232 Three wire Rx Tx GND Data Rates 600 19200 bps Flow Control DCD CTS flow control signals selectable Protocols Transparent Maximum message length is 5000 bytes characters Power Supply Operating voltage 10 to 16 VDC Nominal Current Consumption Standby Receive 165 mA Transmit 1100 mA Environmental Temperature Operating Range 40 C to 60 C Caps...

Page 12: ... 2 Install the PDR221 in to the RTU cabinet Install the PDR221 cabinet See chapter 9 3 Connect the antenna cable ground wire RS232 cable and power supply to the PDR221 See chapter 9 4 Configure the PDR221 by using a hand held terminal or a PC Standard Windows terminal software 56700 N 8 1 The unit can also be pre configured before installation Normally the below listed parameters are the only ones...

Page 13: ...rminals computers protocol converters and multiplexers Fade Margin The greatest tolerable reduction in average received signal strength that will be anticipated under most conditions This measurement provides an allowance for reduced signal strength due to multi path slight antenna movement or changing atmospheric losses A fade margin of 10 to 20 dB is usually sufficient in most systems Flow Contr...

Page 14: ...in station or computer but can gain access through communication channels RSSI Received Signal Strength Indication a parameter returned from a transceiver that gives a measure of the RF signal strength between the mobile station and base transceiver station either as a uplink or downlink measurement SCADA Supervisory Control and Data Acquisition is a system used in industry to monitor and control ...

Page 15: ...t on to the serial port or re transmits via the radio if the message should be repeated 7 2 FEC Forward Error Correction On transmission FEC bits are added to the transmitted data before being converted to a 4 level signal When receiving the FEC information and an FEC algorithm is used to correct any transmission errors A large proportion of transmission errors can be corrected using the FEC 7 3 C...

Page 16: ...o note that a very sensitive radio cannot compensate for a poor antenna installation The sensitivity can be used in propagation studies for radio network planning 7 4 1 PDR221 Receiver Sensitivity Model Frequency Range MHz Channel Bandwidth kHz Radio Data Speed bps Sensitivity BER 1x10 6 PDR221 A VHF 132 150 12 5 4800 9600 111 dBm 109 dBm PDR221 B VHF 132 150 25 9600 19200 114 dBm 107 dBm PDR221 C...

Page 17: ...value can be used to determine the quality of a radio link The RSSI values can be retrieved by executing the Radio Link Test in the configuration menus see 12 8 6 The PDR 221 measures the RSSI value using an A D converter The received signal strength is measured in volts and is translated to a dBm value The graph below shows a typical RSSI voltage value as a function of the signal level Figure 1 R...

Page 18: ...each Model Frequency Range MHz Channel Bandwidth kHz Radio Data Speed bps Article Number PDR221 132 150 12 5 4800 9600 305154 9 PDR221 132 150 25 9600 19200 305155 8 PDR221 150 174 12 5 4800 9600 305156 7 PDR221 150 174 25 9600 19200 305157 6 PDR221 403 422 12 5 4800 9600 305164 7 PDR221 403 422 25 9600 19200 305165 6 PDR221 435 450 12 5 4800 9600 305158 5 PDR221 435 450 25 9600 19200 305159 4 PDR...

Page 19: ...e master In the system which contains slave and repeater slaves and slaves via repeater the direct slaves must wait to answer until the repeater has transmitted the telegram This is to avoid collisions In a slave with repeater delay a time delay is automatically set which will delay the response transmission to the Master until the repeater has repeated the message The purpose of the delay time is...

Page 20: ...ould be configured as slave via repeater and the repeaters as slave and repeater Figure 5 System with Repeater Station When all slaves in a system communicate directly to the master without a repeater in the system as in figure 6 then all slaves should be configured as a slave Figure 6 System without Repeater Station Master Slave with repeater delay Slave and repeater Slave with repeater delay Sla...

Page 21: ...o peer communication When a unit is transmitting all units receive the message and then transmit the message on their serial interface When using as a peer to peer radio system it is not possible to use repeaters All units shall be configured as peer to peer Figure 7 System with Peer to peer functionality P2P P2P P2P P2P ...

Page 22: ...llow When lit the PDR receives data from another radio unit in the system H TX LED Red When lit the PDR transmits data via radio I RS232 Tx LED Red When lit the PDR transmits serial data to connected device J RS232 Rx LED Green When lit the PDR receives serial data from connected device K RS 232 connection For connection of the serial cable 9 pole D sub plug L Configuration Mode Yellow Lit when th...

Page 23: ...hat two or more radios listens to the channel consider it free and start transmitting simultaneously Configuring a random back off delay time called Collision Avoidance Delay solves this issue If the Collision Avoidance Delay function is activated the radio will wait a random time after receiving a serial message from connected device before transmitting a radio message The radio listens to the ra...

Page 24: ... the RTU Example 1 Collision Avoidance Min 1 s Collision Avoidance Max 3 s The radio will always wait 1 second plus a 0 to 2 seconds random time 3 1 2 sec The CA Delay time will be Min 1 second and Max 3 seconds This method can be used if one or more RTU s have priority The highest priority RTU s should be set to CA Delay Min 0 see example 2 and the lower priority ones to a higher value Example 2 ...

Page 25: ...he UHF radios can be factory tuned between 0 01 to 2 0W 10dBm and 33dBm The remote Tx power change is performed via the configuration menus See chapter 12 9 10 The Tx power setting can be read from any radio on the network by executing the Radio Link Test See chapter 12 8 6 8 5 Multiple RTU addressing to one radio The routing technique used in a PDR network allows the user to tie several RTU s to ...

Page 26: ...ially useful if the user wishes to site a master station on a site where other communications equipment may cause or suffer interference The separate Tx and RX frequencies also allow the use of any existing aerial combining distribution systems Note If separate Rx Tx frequencies are used no repeaters can be used between the master and the slave s The frequencies are usually programmed during produ...

Page 27: ...mote radios the onward transmissions need only be simplex 8 9 Repeating Alternative Systems Normally a PDR221 unit discards radio messages containing a non valid System ID However it is possible to configure up to four alternative system ids This allows two or more parallel systems to use one another s radio units as repeaters Note It is not recommended to use this feature in a polled network sinc...

Page 28: ...d that this ground connector is internally connected to the negative pole of the power supply Note It is of vital importance that the negative pole of the power supply the earth terminal and the antenna are connected to the same earth potential The negative pole of the power supply and the radio housing are internally connected 9 2 Power Supply The power supply unit in a radio system must be chose...

Page 29: ...pdr221_04_r02 doc Rev 02 Page 29 60 _ _ 9 3 Battery Power Supply If a re chargeable battery is to be used the connection shall be made as follows Note The Battery Input shall only be used for non rechargeable batteries Battery Power Supply ...

Page 30: ... 8 Out CTS Clear To Send The CTS signal is active high when the PDR is ready to receive data It is deactivated low from when a message is completely received on the serial port until the message is completely transmitted on the radio It is also deactivated low from when a message is detected on the radio until it is completely transmitted on the serial interface Note It is not necessary to use the...

Page 31: ...E DB9F PDR DCE DB9M DCD 1 RD 2 TD 3 DTR 4 DSR 6 RTS 7 CTS 8 RI 9 GND 5 1 DCD 2 RD 3 TD 4 DTR 6 DSR 7 RTS 8 CTS 9 RI 5 GND DTE DB9F PDR DCE DB9M DCD 1 RD 2 TD 3 DTR 4 DSR 6 RTS 7 CTS 8 RI 9 GND 5 1 DCD 2 RD 3 TD 4 DTR 6 DSR 7 RTS 8 CTS 9 RI 5 GND DTE DB9F PDR DCE DB9M DCD 8 RD 3 TD 2 DTR 20 DSR 6 RTS 4 CTS 5 RI 22 GND 7 1 DCD 2 RD 3 TD 4 DTR 6 DSR 7 RTS 8 CTS 9 RI 5 GND DTE DB25F PDR DCE DB9M DCD 8...

Page 32: ... GND 5 1 DCD 2 RD 3 TD 4 DTR 6 DSR 7 RTS 8 CTS 9 RI 5 GND DCE DB9M PDR DCE DB9M DCD 1 RD 2 TD 3 DTR 4 DSR 6 RTS 7 CTS 8 RI 9 GND 5 1 DCD 2 RD 3 TD 4 DTR 6 DSR 7 RTS 8 CTS 9 RI 5 GND DCE DB9M PDR DCE DB9M DCD 8 RD 3 TD 2 DTR 20 DSR 6 RTS 4 CTS 5 RI 22 GND 7 1 DCD 2 RD 3 TD 4 DTR 6 DSR 7 RTS 8 CTS 9 RI 5 GND DCE DB25M PDR DCE DB9M DCD 8 RD 3 TD 2 DTR 20 DSR 6 RTS 4 CTS 5 RI 22 GND 7 1 DCD 2 RD 3 TD ...

Page 33: ... can appear between two characters in the asynchronously transmitted telegram to the radio Figure 11 Communication without handshaking 9 4 3 1 RTS If handshaking is used in the communication between the control system and the PDR the RTS signal s trailing edge is used to determine if the telegram from the control system is finished and that the radio can start transmitting This is done according t...

Page 34: ...low is an example Figure 5 PDR 121 mounted in cabinet Object Name Description A PDR221 Data radio B Connection block For connection of mains Phase neutral or earth C Power supply Converts mains to 12VDC D Coaxial connector N jack For connection of the antenna cable E Cable gland duct For leading cables through the cabinet The cabinet can be equipped with heater and or UPS D C B A E ...

Page 35: ... use with RADIUS radios and have been selected by people with many years of radio network experience Contact Radius for detailed technical information and pricing Accessory examples Antennas o Directional o Omni directional o Gain Antenna Cables Cabinets o Indoor o Outdoor stainless Cabinet Heaters o For operation down to 40 degrees Celsius Backup Batteries Power Supplies o Suitable for RF device ...

Page 36: ...ed to an isotropic radiator An isotropic radiator is an antenna transmitting signals equally in all directions including up and down vertically An antenna of this type has 0dBi gain An isotropic antenna is only a theoretical model that has no real design The higher the decibel number is the higher the gain will be of the antenna For instance a 6dBi gain antenna will receive a signal at a higher le...

Page 37: ...enna should not be confused with an isotropic radiator While an isotropic radiator will radiate in all 3 dimensional directions an omni directional antenna may not radiate vertically up or down 11 1 2 1 Directional Antenna Below is an example of a 14 dBi gain directional antenna The field strength diagrams show the direction of maximum radiation of the antenna The E plane represents the electric f...

Page 38: ...creasing the receiver sensitivity by 3dBm is equal to doubling the output power The receiver sensitivity is except from the radio design itself depending on the antenna and the antenna installation Using a high gain antenna is in many cases much more effective than increasing the transmitter power For example using a 6dBm gain antenna instead of a 0dBm gain on a 2W radio transmitter is equivalent ...

Page 39: ...rgin In very noisy environments the level of the noise floor can be higher than the receiver sensitivity For example greater than 110 dBm in the above example In this case it does not help to increase the receiver sensitivity or using a higher gain receiving antenna The only solution if the source of the noise can not be eliminated is then to increase the power of the transmission so that signal s...

Page 40: ...ation loss This value tells how much the signal strength is decreased due to the distance between the transmitter and the receiver For this we use the Egli model The Egli model is a simplified model that assumes gently rolling terrain with average hill heights of approximately 50 feet 15 meters Land Mobile Radio Systems Edward N Singer PTR Prentice Hall 1994 p 196 Because of this assumption no ter...

Page 41: ...ceiver dBm using dBm instead of dBm Ptx Transmitter RF output power dBm Gtx TX Antenna Gain dB A Over Air Attenuation dB see above Grx Receiver RX Antenna Gain dB Cl Cable Connector Loss dB Note To simplify we use an average Cable Connector loss value including both the Tx and Rx site of 4dB This is in some cases a high value but still assumes a correct antenna cable installation Example 2 Increas...

Page 42: ... margin is 19 dB which is an acceptable level The radio link should be possible Example 2 How high should the master antenna be mounted Distance 12 5 miles 20km Antenna height 1 X Antenna height 2 64 feet 20 meters Radio Tx Power 33 dBm 2W Radio Rx Sensitivity 110 dBm Frequency 142 000 MHz Antenna Gain 1 3dBd Antenna Gain 2 6dBd Cable Connector losses 4 dB total Fade Margin 20dB Calculating highes...

Page 43: ...hat can interfere with the radio signal line of sight The first calculation to be made is the FSL Free Space Loss The FSL value tells how much the signal strength is decreased due to the distance between the transmitter and the receiver FSL Free Space Loss FSL dB 20 LOG λ 4π R Where R Distance between Rx and Tx Antenna Line of sight in meters λ C f 300 f Conclusion using Ex2 If the transmission po...

Page 44: ...l Cable Connector loss including both theTx and Rx site of 4dB This is a high value for most installations but still assumes a correct antenna cable installation Example 5 Receiver sensitivity needed Using Ex2 above and assuming 3dB antennas at each site FM Srx Ptx Gtx FSL Grx Cl Srx Ptx Gtx FSL Grx Cl FM Srx 33dBm 3dBd 111 7dB 3dBd 4dB 20dB 96 7 dBm Example 6 Total antenna gain needed Using Examp...

Page 45: ...ProgInt cable to the PDR Rbus jack 4 Start the terminal program on the PC 5 Select an available PC COM port 6 Configure the communication settings to 57600 8 N 1 7 Press C capital to enter the PDR221 configuration menus Note After configuration Exit Configuration must be chosen or else the PDR221 will remain in the configuration mode and will not operate in the normal mode If the PDR is powered up...

Page 46: ...l 1 Bitrate 9200 bps 2 Parity None 3 Inter Character Timeout 100 ms 4 Use RTS OFF 5 Pre DCD 0 ms 6 Post DCD 0 ms Radio 1 Collision Avoidance Delay OFF 2 Collision Avoidance Delay Min 0 ms 3 Collision Avoidance Delay Max 0 ms 4 Bit Error Rate Test 5 Communication Test 6 Radio Link Test 7 Receiver Test 8 Transmitter Test Advanced 1 Detected Radio Type UHF Low 435 451 MHz 2 Rx Frequency 440000000 Hz ...

Page 47: ... Character Timeout 100 ms Use RTS 0 ms Pre DCD 0 ms Collision Avoidance Delay OFF Collision Avoidance Delay Min 0 ms Collision Avoidance Delay Max 0 ms Rx Frequency 440 000000 MHz Tx Frequency 440 000000 MHz Split Tx Uplink OFF Split Tx Uplink Frequency 0 000008 MHz Radio Link Speed 9600 bps Tx Power Level 33 dBm 2 00 W Non Intrusive diagnostics OFF Press any key to continue ...

Page 48: ...e message Therefore all units in the same radio system shall have the same System Id The System ID range is 01 to 99 Entering 00 will clear the System ID See also chapter 12 6 3 Repeat Alternative Systems 12 6 2 Radio ID The Radio ID is used to identify each radio in the network All radios in the network shall have different Radio ID s The Radio ID range is 01 is 99 Thus one PDR radio network can ...

Page 49: ...Even or Odd 12 7 2 1 Inter Character Timeout Selection of the space in time allowed between characters in a serial telegram which is accepted by the PDR221 This can be specified between 0 999 ms When in the OFF mode the PDR 221 will allow eternal time between characters in an incoming telegram See chapter 9 4 3 12 7 2 2 Use RTS Enabling Disabling of the RTS EOM End of Message detection functionali...

Page 50: ... used if collision avoidance delay is set to ON Time can be set between 0 9 9 s 12 8 3 Collision Avoidance Delay Max Maximum waiting time before transmission of unsolicited messages only used if collision avoidance delay is set to ON Time can be set between 0 9 9 s 12 8 4 Bit Error Rate Test The Bit Error Rate Test is used to test the transmission data quality between two radio units in the networ...

Page 51: ...ve radio units adjacent to the master radio site to gain a split uplink network If enabled the radio will transmit on one frequency to the master uplink and on another when repeating messages from the master downlink to other units the network 12 9 5 Split Tx Uplink Frequency If split Tx frequency is enabled this frequency is used when transmitting to the radio id indicated by split Tx uplink id 1...

Page 52: ...jacent direct slave radios will have split Tx uplink enabled and the master id and Rx frequency set as split Tx uplink id and split Tx uplink frequency All other slave radios will have both the Rx and Tx frequency set to the masters Tx frequency 12 9 10 Remote Tx Power Level Change This feature is used to change Tx power level on a remote unit in the network 12 9 11 Radio VCO Lock Test The configu...

Page 53: ... saved to file for documentation Current Configuration Function Master System Id 01 Radio Id 02 Serial 19200 8N1 Inter Character Timeout 100 ms Use RTS No Pre DCD 0 ms Post DCD 0ms Collision Avoidance Delay OFF Collision Avoidance Delay Min 0 ms Collision Avoidance Delay Max 0 ms Rx Frequency 142 012500 MHz Tx Frequency 142 012500 MHz Split Tx Uplink OFF Split Tx Uplink Frequency 0 000008 MHz Radi...

Page 54: ...rate should be below 10 100 bit errors Please contact Radius support to evaluate any test results A command is transmitted from the particular radio unit to the receiving radio unit which replies by transmitting back a random sequence bit stream A correctly received character is displayed on the screen as a U and an incorrectly received character is displayed as a period The function should be use...

Page 55: ...UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU UUUUUUUUUUUUUUU UUUU UUUUUUU UUUUUUUUUUUUUUUUUUUU UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU UUUUUUUUUUUUUUUUU UUUUUUUU UUUUUUUUU UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU UUUUUUUUUUUUUUUUUUUU UUUUUU UUUUUUU UUUUUUUUUUUUUUU Radio ID 02 Number of corrupted bytes At attenuation level 0 0000 errors At attenuation level 1 0000 errors At attenuation level 2 0020 errors At ...

Page 56: ...he network Five attempts are carried out per test If acknowledge is received from the opposite radio Passed is presented on the screen If no acknowledge is received Failed is presented See the menu example below Communication Test Radio Id 03 Attempt 1 Passed Attempt 2 Passed Attempt 3 Passed Attempt 4 Passed Attempt 5 Failed Press any key to continue Id 01 3 2 1 4 PC Hand Termial Id 02 Id 03 ...

Page 57: ...n the radio network Radio Link Test Radio Id 01 Path 03 02 01 02 03 RSSI dBm 80 81 78 80 TxPwr dBm 33 33 33 33 Press any key to continue The example above shows a Radio Link Test carried out from radio 03 to radio 01 The arrows indicate the direction of the radio message The transmitter power at Radio 03 is 33dBm 2W and the RSSI level at Radio 02 is 80dBm The transmitter power at Radio 02 is 33 dB...

Page 58: ...n the shield and braid Is the SWR Standing Wave Ratio correct Communication Can the PDR perform a Communication Test or a Radio Link Test How is the result from the Bit Error Rate Test Has the PDR been moved from its original place External circumstance e g has new houses or the like been built That the radio units are correctly programmed as in chapter 5 Serial communication Does the RS 232 TX or...

Page 59: ...RADIUS Product Description PDR221 iom_pdr221_04_r02 doc Rev 02 Page 59 60 AppendixA PDR 221 Layout Drawing ...

Page 60: ...RADIUS Product Description PDR221 iom_pdr221_04_r02 doc Rev 02 Page 60 60 Reference Document Description 1 ANTENNAS Antenna equipment installation description 2 MAINTMAN Maintenance Manual 3 4 ...

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