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    JAN MAYEN - SEISMOMETER SITES JNE/ULLA, JNW/LIBERG - UPGRADE 2018    

   NEW TELEMETRY SYSTEM

UNIVERSITY OF BERGEN
Department of Earth Science
 Allé gt. 41, N-5007 Bergen, Norway 
             
0.1 DRAFT - for comments - 25 November, 2018 O.M. - -
VER. STATUS CHANGE DATE BY CHECKED APPROVED

TABLE OF CONTENTS

+Contents
  1. 1 INTRODUCTION
  2. 2 UPDATE, 25 NOVEMBER 2018
  3. 3 OVERVIEW - LINK TOPOLOGY
  4. 4 WLAN LINK-- "AS BUILT" DOCUMENTATION AUGUST 2018
    1. 4.1 Identical antenna for Monitorhytta and Ulla/Liberg
    2. 4.2 Best vertical angle of Access Point antenna
    3. 4.3 WLAN Access Point and client - same model used for both
      1. 4.3.1 Power consumption
      2. 4.3.2 PoE = "Power over Ethernet" - which wires are used ...?
      3. 4.3.3 A proper RJ45 tool is required, that cuts and strips outer insulation to specified length
    4. 4.4 Minimum received signal strength required - recommendation
    5. 4.5 Link budget
      1. 4.5.1 Free space loss
    6. 4.6 Switch is required in order to merge data streams from many instruments
    7. 4.7 Extending Ethernet and Power to Liberg sensor vault, approx 1 km from instrument cabin
      1. 4.7.1 DC/DC-converter placed in instrument cabin fed 48 Vdc into one pair
      2. 4.7.2 The other pair used for Ethernet Extenders
  5. 5 WLAN LINK TEST, 16 MAY 2018: 9.77 KM LINK
    1. 5.1 Access point side
    2. 5.2 Client (station) side: Hyperlink Technologies, model HG2418P (panel antenna)
  6. 6 ETHERNET CABLE FOR OUTDOOR USE
  7. 7 ---- OR SHOULD WE HAVE COAX CABLE BETWEEN ANTENNA AND WLAN UNIT ?
  8. 8 ANTENNA CANDIDATES
    1. 8.1 Candidates, for access point (base station)
    2. 8.2 Candidates, for station (client)
  9. 9 EVALUATION / TEST RESULTS
    1. 9.1 Access point configuration and test
    2. 9.2 Client (station) configuration
    3. 9.3 Data traffic simulation: UDP broadcasts (on different ports)
    4. 9.4 Simulate data load 100 kbit/second - Python script
    5. 9.5 Power consumption
  10. 10 APPENDIX
    1. 10.1 LINE-OF-SIGHT (LOS) TO "MONITORHYTTA"
      1. 10.1.1 As seen from JNW/Liberg
      2. 10.1.2 As seen from JNE/Ulla
    2. 10.2 Timers for system reset at regular intervals
      1. 10.2.1 Programmable digital timers furnished with relay
      2. 10.2.2 Wireless (433Mhz) Remote Control Switch
    3. 10.3 Suppliers of antennas and associated hardware, enclosures, etc.
    4. 10.4 WLAn equipment, other manufactureres
    5. 10.5 Access point candidate - not used
    6. 10.6 Data compression

1 INTRODUCTION


We plan to upgrade Jan Mayen seismometer locations JNE/Ulla and JNW/Liberg in 2018. This section provides documentation on telemetry part of upgrade plans.

2 UPDATE, 25 NOVEMBER 2018


BULLETM2-TI and the panel antenna system has worked flawlessly since installation in August.

3 OVERVIEW - LINK TOPOLOGY


Telemetry system seems to be the most power-hungry part of Ulla & Liberg instrumentation. Hopefully, current consumption can be reduced by adjusting TX output power, down to a level that is sufficient - according to telemetry link budget.

4 WLAN LINK-- "AS BUILT" DOCUMENTATION AUGUST 2018


4.1 Identical antenna for Monitorhytta and Ulla/Liberg


We have used the same antenna both for WLAN client (stations) and Access Points:

Click to enlarge.

VP270/24


Although not stated in the specification, from the vertical (elevation) radiation pattern below we estimate that antenna has a downtilt of 5.5 degrees. This should be taken into account when mounting the Access Point antenna.

4.2 Best vertical angle of Access Point antenna


There is a downtilt of 5.5º (ref antenna diagrams above). In order to calculate LOS vertical angle for Ulla and Liberg (as seen from Monitorhytta) we need elevation data for these three sites:

  • JMIC / Monitorhytta: 158 meter elevation
  • JNE / Ulla: 57 meter elevation / 7.74 km from Monitorhytta => Delta elevation: 158-57 = 101 meter; LOS vertical angle as seen from Monitorhytta: tan-1(101/7740) = 0.75º downwards.
  • JNW / Liberg: 95 meter elevation / 4.8 km from Monitorhytta => Delta elevation: 158-95 = 63 meter; LOS vertical angle as seen from Monitorhytta: tan-1(63/4800) = 0.75º downwards.

Conclusion: With antenna downtilt of 5.5º, it should point 5.5º-0.75º = 4.75º upwards.

Since antenna height is 235 mm, its lower edge should be offset sin(4.75) * 235 = 19.5 mm in order to get 4.75 degrees uptilt.

4.3 WLAN Access Point and client - same model used for both


This unit can be configured as either Access Point or station (client).

Client stations are Ulla & Liberg. Access point will be placed at Monitorhytta.

CAN ALSO USE:

4.3.1 Power consumption


Client:

  ------------------------------------------------------
   TX power  Supply voltage     Current          Power
  ------------------------------------------------------
     0 dBm     24.0 V        0.14 - 0.15 A      3.6 Watt
    10 dBm     24.0 V        0.14 - 0.15 A      3.6 Watt
    20 dBm     24.0 V        0.14 - 0.15 A      3.6 Watt

4.3.2 PoE = "Power over Ethernet" - which wires are used ...?


T568A pair and T568B pair is due to Ethernet crossover cable - no longer needed. Most Ethernet cables now use T568B.

Source: https://en.wikipedia.org/wiki/Power_over_Ethernet

Click to enlarge.

4.3.3 A proper RJ45 tool is required, that cuts and strips outer insulation to specified length


4.4 Minimum received signal strength required - recommendation


Quoting from page 7 of AirOS User Guide:

''Signal Strength (Available in Station mode only.) Displays the received wireless signal level (client-side). The represented value coincides with the graphical bar. Use the antenna alignment tool to adjust the device antenna to get a better link with the wireless device. The antenna of the wireless client has to be adjusted to get the maximum signal strength. Signal Strength is measured in dBm (decibels referenced to 1 milliwatt). The conversion is defined as follows:

P(dBm) = 10 ∙ log10 ( P(mW) / 1 mW )

where P(dBm) is the power in decibel re. 1 milliwatts

So, 0 dBm would be 1 mW and -72 dBm would be 0.0000006 mW. A signal strength of -70 dBm or better (-50 to -70 dBm) is recommended for stable links.''

Click to enlarge.

WLAN signal strength at JNE/Ulla, as seen during installation 12 August 2018. Click to enlarge.

4.5 Link budget


Assumptions:

  1. Only budget for "worst-case" scenario: Link between Monitorhytta and JNE/Ulla, which are 7.74 km apart. Distance between point on the other leg of the link, between Monitorhytta and Liberg, is
  2. AirMax Bullet M2 Titanium at both sides.
  3. We will use coax cable between antennas and WLAN equipment - on Jan Mayen, it is recommended to protect all instrumentation inside shelters.
 Transmitting, sensor site JNE/Ulla:
    Transmitter output power (common WLAN: +15dBm) ...................................................:   28.0 dBm
    Cable loss: 22 meter coax, RFS 1/2" CELLFLEX p/n LCF12-50J, 11.6 dB loss/100 meter @2400 MHz .....:   -2.6 dB
    Connector loss in dB .............................................................................:   -0.1 dB
    Antenna gain, using VP270/24, by SmartEQ  - data sheet ...........................................:   12.0 dBi

 Propagation:
    Free space loss (calculate here), 7.74 km ........................................................: -118.0 dB

 Receiving, Access Point location JMIC/Monitorhytta:
    Antenna gain, using VP270/24, by SmartEQ  - data sheet ...........................................:   12.0 dBi
    Cable loss  (Normally -3 to -10 db)  / receiver attached directly to antenna .....................:    0.0 dB
    Connector loss ...................................................................................:   -0.1 dB
    Receiver sensitivity (11b/g; 24 Mbps) ............................................................:  -83.0 dBm

                                                                                   Remaining margin ..:   14.2 dB

Link should work properly if sites are in clear line of sight. Check for Fresnel zone and diffraction limitations.

Remarks (must be verified - here is the source):

  1. To achieve a very reliable link, a margin of at least 10 dB is needed. This accommodates for local fading (= variations of signal strength caused by reflections). A 4 to 6 dB margin is needed if the link reliability is moderate.
  2. Check if Fresnel and/or diffraction limitations apply. Add extra losses to the margin that is needed.
  3. Polarization errors: add 3 dB loss to the required margin when helical antennas to horizontal or vertical antennas are used. Add 30 dB loss in the case of polarity mismatch between antennas. (Hor/vert antenna or left/right rotating antennas).
  4. If you are going to use a high gain antenna (> 5dBi), (for ranges > 1km), you MUST REDUCE the output power in order to stay within the legal power limit. This must be done without affecting the receivers' sensitivity, so it can ONLY be done inside the WLAN equipment, so BEFORE to the RF send/receive switch. You'll have to find WLAN equipment that is able to reduce its power internally.
  5. Note that receiver sensitivity varies much more over equipment manufacturers than output power. Sensitivity can vary over 10 dB(!). Since output power is limited by legal limits, you MUST find yourself the most sensitive receiver that's available. It's NOT a highest transmitter's power that does the job for legal limit links, it's the best receiver's sensitivity!

  • Selection of coax cable: RFS [Radio Frequency Systems] 1/2" CELLFLEX modell LCF12-50J, that according to data sheet (also local copy) has 11.6 dB loss/100 meter @2400 MHz, which should amount to 2.6 dB loss with 22 meter cable length.
  • Normal antenna gain (8 dB biquad; 15 db helix; 24 dB parabolic)
  • Cable loss is normally -3 to -10 db.

4.5.1 Free space loss


Free space loss at 2.45 GHz

It is the power loss of wave travelling in free space (without obstacles).

(Friis formula)

    Lp(dB)= 92,45 + 20log10 F+20 LOG10d 
    Lp= Path loss
    F= frequency in GHz
    dB= decibels
    d= Distance in kilometres
    Example:  A distance of 6 kilometre provides a free space loss of –116 dB.

Source

Results:

  Link Monitorhytta - JNE/Ulla ....:  Distance 7.74 km, loss @ 2450 MHz:  117.98 dB
  Link Monitorhytta - JNW/Liberg ..:  Distance 4.80 km, loss @ 2450 MHz:  113.83 dB
  Test link Bergen, 16 May, 2018 ..:  Distance 9.77 km, loss @ 2450 MHz:  120.0  dB

4.6 Switch is required in order to merge data streams from many instruments


We used this DIN rail, DC-driven switch at both remote stations:

Click to enlarge.
  • Model: EDS-205 - Network Switch
  • Manufacturer: Moxa
  • Supplier: ELFA Distrelec, part number: 125-73-421
  • Link to data sheet
  • Number of RJ-45 ports: 5
  • Supply voltage: 12 - 48 Vdc
  • Input current, EDS-205: 0.11 A @ 24 V => 2.6 Watt
  • Operating Temperature: -10 to 60°C

4.7 Extending Ethernet and Power to Liberg sensor vault, approx 1 km from instrument cabin


Click to enlarge.

JNW/Liberg sensor vault. Instrument cabin can be seen as white spot on ridge, approx 1 km distance from vault. Click to enlarge.

We used the old 2-pair cable between instrument cabin site and sensor vault - separated by a distance of almost 1 km - to bring both power and Ethernet to sensor vault. The cable is very sturdy and appears to be in good condition.

4.7.1 DC/DC-converter placed in instrument cabin fed 48 Vdc into one pair


Click to enlarge.
  • Manufacturer: Phoenix Contact
  • Model: MINI POWER 33.6W Isolated DC-DC Converter DIN Rail Mount, Vin 10 → 32 V dc, Vout 48V dc
  • Link to Data sheet
  • Supplier: RS Components
  • Supplier part number: 708-0441

4.7.2 The other pair used for Ethernet Extenders


Click to enlarge.

Model: BB-EIR2-EXTEND from B&B SmartWorx, Inc.

5 WLAN LINK TEST, 16 MAY 2018: 9.77 KM LINK


Access Point (AP) side:

  • Height ASL: 93 meter
  • AP:
    • IP = 192.168.1.100
    • Admin account name: ubnt (default)
    • Password: ---
  • Linux laptop:
    • IP = 192.168.1.99
    • SSHd: Account name =...; Password = ...

Client (station) side:

  • Coordinates:
    • 60.41290º N, 5.21623º Ø
    • 92 M ASL
  • IP = 192.168.1.xxx
  • Admin account name: ubnt (default)

5.1 Access point side


At Access Point site, we used Demarctech, model DT-AN-24-OV-8 --- datasheet of 2.4 GHz whip antenna (procured ca 2006; manufacturer ceased operation since then).

Click to enlarge.

WLAN test. Access Point installed on roof of Science Building. Click to enlarge.

5.2 Client (station) side: Hyperlink Technologies, model HG2418P (panel antenna)


ELECTRICAL SPECIFICATIONS:

6 ETHERNET CABLE FOR OUTDOOR USE


Ubiquiti TOUGHCable Pro CAT 5e 304.8m Black

  • Datasheet
  • 24 AWG
  • Solid Bare Copper
  • Conductor Diameter: 0.500 ± 0.005 mm
  • Jacket Material: PE
  • Jacket Thickness: AVG: 0.50 mm, MIN: 0.46 mm
  • Jacket Outer Diameter: 6.0 ± 0.30 mm

7 ---- OR SHOULD WE HAVE COAX CABLE BETWEEN ANTENNA AND WLAN UNIT ?


As of 3 May 2018, we changed plans slightly: We intend to use the same model for access point (AP) and station (client). This is possible since both Rocket M2 2.4 GHz and AirMax Bullet M2 Titanium can be configured as AP or client. This decision made since we doubt that Rocket M2 will survive the very harsh weather conditions on Jan Mayen island; it is furnished with two RP-SMA connectors that fits nicely with AM-2G-16-90 sector antenna. However, in the specifications is is stated that "Operating Humidity: 5 to 95% Non-condensing" --- and moisture condensation will surely occur on Jan Mayen.

The same argument goes for AirMax Bullet M2, where datasheet states: "Operating Humidity: 5 to 95% Condensing", where there must be a printing error, so it should read "Non-condensing" (b/c "5 to 95% Condensing" does not make sense).

This leads to the conclusion that coax cable must be used between antenna and WLAN unit, and the latter must be located either in enclosure or instrument cabin.

Coax cable should be low-loss type and suitable for harsh weather conditions. We propose:

RFS [Radio Frequency Systems] 1/2" CELLFLEX modell LCF12-50J, that according to data sheet (also local copy) has 11.6 dB loss/100 meter @2400 MHz, which should amount to 2.3 dB loss with 20 meter cable length.

8 ANTENNA CANDIDATES


8.1 Candidates, for access point (base station)


Antenna for base station (Monitorhytta):

Plan is to use a single antenna covering both Ulla and Liberg. The LOS (Line-of-Sight) azimuth angle between Ulla and Liberg, as seen from Monitorhytta, is 61º (ref map above). This antenna selected:

  • Mfr: Ubiquiti
  • Model: AM-2G-16-90
  • Supplier: Dustin.no
  • Freq range: 2.3 - 2.7 GHz
  • Gain: 16.0 - 17.0 dBi
  • Azimuth bandwidth [-6 dB]: 90º; from radiation diagram: At 60º, attenuation is 3 dB
  • Elevation bandwidth seems to be 9º, and there is a downtilt of 4º (ref antenna diagrams below). In order to calculate LOS vertical angle for Ulla and Liberg (as seen from Monitorhytta) we need elevation data for these three sites:
    • JMIC / Monitorhytta ..: 158 meter elevation
    • JNE / Ulla .................: 57 meter elevation / 7.74 km from Monitorhytta => Delta elevation: 158-57 = 101 meter; LOS vertical angle as seen from Monitorhytta: tan-1(101/7740) = 0.75º
    • JNW / Liberg ............: 95 meter elevation / 4.8 km from Monitorhytta => Delta elevation: 158-95 = 63 meter; LOS vertical angle as seen from Monitorhytta: tan-1 (63/4800) = 0.75º
    • Conclusion: With antenna downtilt of 4º, it should point 4º-0.75º = 3.25º upwards.
    • Wind survivability: 125 mph = 56 m/s (hurricane starts at 33 m/s)
    • Link to Installation manual (PDF)

Antenna for "clients" at Ulla & Liberg: Not determined yet. Keeping advise from Icelandic Meteorological Office in mind: In order to prevent telemetry disruption due to icing, the metallic antenna elements should be covered in plastic dome.

Click to enlarge.

8.2 Candidates, for station (client)


Models:

Manufacturers: of both omni and directional antennas, suitable for outdoor use in harsh climate:

Suppliers::

9 EVALUATION / TEST RESULTS


9.1 Access point configuration and test


ACCESS POINT CONFIGURATION
No. Configuration item Screenshot
1 SYSTEM -- Firmware version:

(a) Uploaded and installed latest version as of 24 April, 2018: XM ver. 6.1.6

(b) DO NOT reduce Ethernet speed to 10 MBit/s (in the hope of reducing power consumption) - uploads will then take forever. And after pressing "install" button, upgrade process does not work.

Click to enlarge.
2 MAIN > THROUGHPUT; without wlan traffic: Click to enlarge.
3 MAIN > THROUGHPUT; TEST 1; first 100 kBit/s injected from one client: Click to enlarge.
4 MAIN > THROUGHPUT; TEST 2; 100 kBit/s injected from additional client - so AP must handle 200 kBit/s from two stations - and retransmit this traffic to both AP's: Click to enlarge.
5 MAIN > STATIONS: Click to enlarge.
6 MAIN > INTERFACES: Click to enlarge.
7 WIRELESS: Click to enlarge.
8 NETWORK: Click to enlarge.
9 ADVANCED: Click to enlarge.
10 SERVICES: Click to enlarge.
1 SYSTEM: Click to enlarge.

9.2 Client (station) configuration


9.3 Data traffic simulation: UDP broadcasts (on different ports)


Software for UDP broadcasts that simulates system load.

As a system stress test, each station should generate 100 kBit/s data traffic of UDP broadcast telegrams. In practise, each station would transfer less then 35 kBit/second.

9.4 Simulate data load 100 kbit/second - Python script


Here is a tiny Python script that sends UDP Broadcast telegrams at an adjustable rate. The rate is determined by the amount of delay in time.sleep() instruction at the bottom - the actual rate can be seen in WLAN web interface graph. Adjust delay to obtain approx 100 kBit/second data rate - more then twice what is expected.

send-udp-telegrams-port-2000.py

import socket
import time

# Constants
GPS_UDP_PORT = 2000


# Open GPS NMEA UDP socket
gps_target_adr = ('<broadcast>', GPS_UDP_PORT)
gps_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
gps_socket.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)


while True:
    now = time.localtime()
    current_date = time.strftime("%d%m%y", now)
    current_time = time.strftime("%H%M%S", now)

    nmea_GPGGA = "$GPGGA," + current_time + ",6059.9999,N,00559.9999,E,1,5,1.5,30.8,50.4,,,*FF\n"
    nmea_GPVTG = "$GPVTG,359,T,355,M,012.5,N,0001.5,K,A\n"
    nmea_GPRMC = "$GPRMC," + current_time + ",A,6059.9999,N,00559.9999,E,0001.5,359.9," + current_date + ",,,*FF\n"

    gps_socket.sendto(nmea_GPRMC, gps_target_adr,)
    print nmea_GPRMC,
    gps_socket.sendto(nmea_GPGGA, gps_target_adr,)
    print nmea_GPGGA,
    gps_socket.sendto(nmea_GPVTG, gps_target_adr,)
    print nmea_GPVTG,

    time.sleep(0.01)

Here is a script to display UDP Broadcast telegrams on another machine:

#! /usr/bin/python
# This programs dumps UDP telegrams to stdout
# Just specify port number

from socket import *
PORT = 2000
s = socket( AF_INET, SOCK_DGRAM )	# Get UDP socket
s.bind(('', PORT))			# BIND to address and port
while True:
    t,adr = s.recvfrom(1000)		# A blocking read ...
    print adr, t

9.5 Power consumption


Client:

  ------------------------------------------------------
   TX power  Supply voltage     Current          Power
  ------------------------------------------------------
     0 dBm     24.0 V        0.14 - 0.15 A      3.6 Watt
    10 dBm     24.0 V        0.14 - 0.15 A      3.6 Watt
    20 dBm     24.0 V        0.14 - 0.15 A      3.6 Watt

10 APPENDIX


10.1 LINE-OF-SIGHT (LOS) TO "MONITORHYTTA"


10.1.1 As seen from JNW/Liberg


Click to enlarge. Click to enlarge.
Click to enlarge. Click to enlarge.
Click to enlarge.

"Monitorhytta" seen from Liberg. Distance = 4.8 km.

Is the tower safe? Consult company that maintains antenna structures on Jan Mayen: ST Dahl AS, Drøbak.

10.1.2 As seen from JNE/Ulla


Click to enlarge.

There is LOS (line-of-Sight) from JNE/Ulla to JMIC/"Monitorhytta" - but remote cabin cannot be seen in this photo, see below. Click to enlarge.

Click to enlarge.

August 2016, photo taken from JNE/Ulla antenna tower, confirming there is Line-of-sight to JMIC/"Monitorhytta". Click to enlarge. Credit: Odd T, Jan Mayen base.

10.2 Timers for system reset at regular intervals


Most electronic system of a certain complexity will most likely eventually enter an unresponsive state, and power cycling will be required to resume normal operation. There are different methods to solve this problem:

  1. A separate communication channel where power cycling commands can be transmitted (like SMS activated relays),
  2. Programmable digital timers furnished with relay,
  3. A watchdog system whereby hold-off instructions are sent through the normal communication system; their absence will trigger power cycling event.

10.2.1 Programmable digital timers furnished with relay


Digital, programmable timer. Source: UNAVCO

10.2.2 Wireless (433Mhz) Remote Control Switch


10.3 Suppliers of antennas and associated hardware, enclosures, etc.


10.4 WLAn equipment, other manufactureres


10.5 Access point candidate - not used


Base station (to be located at Monitorhytta):

10.6 Data compression


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