'''[wiki:GEC16Agenda/WiMAX-Tutorial/Streamload/07 Previous]'''

== Revise, Repeat ==

After looking at the measurements collected by the 'wxmstat' application, we realize that the signal strength on the nodes is too high. The WiMAX CINR (a measure of signal quality) is 30 dB, which is very high, and so the maximum number of SVC layers (2) is downloaded in all cases. We want a more realistic environment, so we turn down the base station transmit power:


{{{
wget -qO- "http://wimaxrf:5052/wimaxrf/bs/set?bs_tx_power=15"
wget -qO- "http://wimaxrf:5052/wimaxrf/bs/restart"
}}}

He also uses the programmable attenuation on Sandbox 4 to create a situation where signal strength varies over the duration of the experiment. To do this, he adds some properties to the beginning of his experiment:

{{{
#!ruby
defProperty('attUrl', "http://internal2dmz.orbit-lab.org:5054/instr/set?", "Path to use to set attenuation")
}}}

and changes the sequence of events in the experiment to look like this:

{{{
#!ruby
onEvent(:ALL_UP_AND_INSTALLED) do |event|
  l =  [5,6,7,4,3,6,10,11,12,8,7,9,5,3,5,6,7,4,3,6,10,11,12,8,7,9,5,3]
  wait 5
  system("/home/#{ENV['USER']}/getbsconf -i wimaxrf --oml-server tcp:oml:3003 --oml-id console --oml-exp-id #{Experiment.ID}")
  group("server").exec("/usr/bin/python -m SimpleHTTPServer")
  group("client1").startApplications
  l.each do |a|
    system("/usr/bin/wget -qO- \"#{property.attUrl}portA=#{property.client1}\&portB=9\&att=#{a}\"")
    wait 5
  end
  group("client1").stopApplications
  wait 5
  group("client2").startApplications
  l.each do |a|
    system("/usr/bin/wget -qO- \"#{property.attUrl}portA=#{property.client2}\&portB=9\&att=#{a}\"")
    wait 5
  end
  group("client2").stopApplications
  wait 5
  allGroups.stopApplications
  Experiment.done
end

}}}

The effect of this is to change the attenuation between the WiMAX BS and the client in a fixed sequence every five seconds during the experiment.

[[br]]

After running this modified experiment with 

{{{ omf exec wmxtutor-streamload2.rb }}}

He looks at the iRODS plot and is happy with the result.

'''[wiki:GEC16Agenda/WiMAX-Tutorial/Streamload/09 Next]'''