Tuesday, August 28, 2007

graphing skystream DVB receiver's Eb/No and signal strength

What is Skystream DVD receiver?
What is the OID variable ID for Eb/No and signal strength values of Skystream DVB receiver?
What are the statistical values available from Skystream DVB receiver?
How to retrieve Eb/No value from Skystream DVB satellite receiver box from linux terminal?
How to retrieve signal strength value from Skystream DVB receiver box from linux terminal?
How to retrieve statistical values from non-SNMP variable of Skystream DVB from terminal?
How to create and generate a Eb/No and signal strength MRTG graph of Skystream DVD receiver?

One telecom and satellite device that still works inside my work area is SkyStream DVB receiver. Skystream DVB receivers are box appliances that make use and boot up from a customized modified linux-based kernel. This VSAT equipment is usually inserted and plugged between satellite dish connectivity and core firewalls and/or core routers, that is if you are managing broadband satellite networks.

This document entry is here to cover and monitor statistical values fetched from Skystream media routers. Google spiders, as of this writing, failed to show these OID variables and Skystream MIB variable files for further polling Skystream's Eb/No and signal strength values particularly from EMR-1600, EMR-5000, and EMR-5500 Skystream DVB receiver models.

SkyStream DVB Receiver Statistical Values
Sourced from DVB TOC file.

The Satellite Receiver statistics page shows information gathered from the unicast and multicast streams forwarded to the EMR from the Satellite Receiver. The Satellite Receiver page contains the following information:

* LNB Mode: Shows current mode as None, Single, or Dual.
* L-Band Frequency: Shows the L-Band frequency setting for the tuner.
* 22kHz Switch: Shows if 22kHz Switch is enabled, disabled or set to automatic.
* Symbol Rate: Shows the number of symbols per second being received through the tuner. This parameter can be set in Preferences as either megasymbols or kilosymbols.
* LNB Voltage Control (polarization): Shows if the polarization is set to Vertical Right or Horizontal Left.
* LNB Offset: Displays the frequency offset of the LNB in megahertz.
* Viterbi Rate: Indicates the Forward Error Correction (FEC) ratio of payload bits to the total number of bits. For example, if FEC=3/4, then for every 4 bits, 3 bits are actual data and 1 bit is overhead for error correction.
* Channel Bit Rate: Shown as Mbps— "useful bandwidth" is a calculation using the following formula; symbol rate x 2 x viterbi rate 188/204.
* QSPK Spectral Inversion: Shows as "Normal-Not Inverted" or "Inverted" this is automatically detected from the signal.
* Signal Lock (QPSK Lock): A green bar with the word LOCK will appear when the frequency and symbol rate are locked. If the signal cannot be locked, the bar will be grayed out.

NOTE For some models, BPSK or QBSK can be selected from Maintenance—Preferences, Advanced Preferences.
* Data Lock (FEC Lock): A green bar with the word LOCK will be displayed if Symbol Rate, L-Band Frequency, and FEC are set properly. If data cannot be locked, a red bar is displayed with the words "NO LOCK" in the bar.
* MPE Lock: A green bar with the word LOCK will be displayed if data with an MPE header is being received. If data cannot be locked, a red bar is displayed with the words "NO LOCK" in the bar.
* Signal Strength: Shows a value and percentage for the signal strength being received from the satellite (-25 dBm to -65 dBm).
* Eb/N0: Displays the signal to noise ratio value detected by the Satellite Receiver in decibels.
* QPSK Bit Error Rate: Displays the measured QPSK bit error rate.
* Viterbi Bit Error Rate: Displays the measured error rate from the FEC algorithm.
* Reed Solomon Corrected Errors: Shows the errors that were fixed using the Reed Solomon algorithm. These errors indicate that some data was corrupted and then corrected. Errors are collected over time and will continue to build; a button is included on this page to clear the error counters.
* Reed Solomon Uncorrected Errors: Displays the total number of errors that the Reed Solomon Correction Algorithm detected but was unable to correct.

Skystream website is now part of Tandberg Television.


Retrieve Eb/No and signal strength values from any web-enabled satellite DVB receiver devices and media routers for further long-term graphing, analysis and monitoring.


A simple workaround solution using linux commands via terminal.


Fireup your terminal and issue the command as follow

# elinks -dump 1 -auth=emrYOURusername:emrYOURpassword "http://YOUR-DVB-IP/cgi-bin/statistics?page=sat&session=sat"

As usual, changes needs to be done from the above shown commands:
emrYOURusername = would be admin's username
emrYOURpassword = would be admin's password
YOUR-DVB-IP = dvb's IP address

Resulting sample output:
Satellite Receiver Statistics
Parameter Satellite Receiver 1
LNB Mode None
L-Band Frequency 1000.0000 MHz
22kHz Switch Disabled
Symbol Rate 27.0047 Msymbols/s
LNB Voltage Control (polarization) Vertical - Right
LNB Offset 0.1650 MHz
Viterbi Rate 7/8
Channel Bit Rate 43.5517 Mbps
QPSK Spectral Inversion Normal - Not Inverted
Signal Lock (QPSK Lock) LOCK
Data Lock (FEC Lock) LOCK
Signal Strength 72 %
Eb/N0 15.0277 dB
QPSK Bit Error Rate 0.0000
Viterbi Bit Error Rate 0.0000
Reed-Solomon Corrected Errors 0
Reed-Solomon Uncorrected Errors 7
Auto Refresh (_) Enable (_) Disable
Auto Interval ___ Sec [BUTTON] [BUTTON]

As you can see from above, these resulting output is supposed to be viewed as HTML page from browsing the IP address of the said box.

Using this linux command lynx, we have just dumped out the page into our screen. Basically, the important numerical value that is needed here are Eb/No and signal strength values.

Now, further string manipulation command is required if you wish to get t

he numerical value of Eb/No and signal strength. String manipulation in linux can be done many ways.

Here's one way to do it. From the last issued command, you just need to append linux filtering commands grep. By piping last screen output as an input to grep would be as follows

| grep 'Eb/N0\|Signal Strength'

to make the first linux command to look like

# elinks -dump 1 -auth=emrYOURusername:emrYOURpassword "http://YOUR-DVB-IP/cgi-bin/statistics?page=sat&session=sat" | grep 'Eb/N0\|Signal Strength'

This linux compounded commands would now give us what needed most, a 2 liner output like so:

Signal Strength 72 %
Eb/N0 15.0125 dB

If you wish to feed this values into to MRTG scripts, further string manipulation is required.

Since we already know that the first value is the signal strength and the second value is the Eb/No., we need to remove the first 40 characters of each lines. This would be done using linux command cut like so

cut -c 40-

Then, fetching the first field like so

awk '{print $1}'

Finally we would arrive to a one shot linux command on getting Skystream DVB receiver's Eb/No and signal strength values, like so

# lynx -dump -auth=emradmin:gulaydvb "http://YOUR-DVB-IP/cgi-bin/statistics?page=sat&session=sat" | grep 'Eb/N0\|Signal Strength' | cut -c 40- | awk '{print $1}'

Resulting output:

which can be easily dumped to MRTG for further SNMP polling and graph generation. Using this approach, you can now graph and monitor the other Skystream DVB receivers's statistical values.

Additionally, creating graphs for skystream dvb's intel-based ethernet network cards would be simply done the normal way since ethernet cards for most appliances and boxes supports SNMP. Like shown below:

Now, google spiders can lead you to this page with regards to graphing Eb/No and signal strength from Skystream DVB receiver models.

Hope this helps.


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