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Spirent TestCenter: TX MCS Values with 2SS are NOT achieving MCS11 in 80 MHz - CBW with Upstream traffic

Symptoms

When we are testing upstream traffic with 80 MHz - Channel BandWidth and 2 SS we are observing that Tx MCS values are never coming up with MCS11 (1024-QAM 5/6)
On other other hand if we are testing the same thing with 4SS then we are seeing MCS 11 consistently.
  • 2SS

 
​
  • 4 SS

 
Environment
 
  • WiFi
  • MCS Type
  • 2 SS
  • 4 SS

 
Explanation/Resolution
 
  • CR created:
    • CR:0145223
    • JIRA ID: CIPCD-162362 
    • Subject: TX MCS Values with 2SS are NOT achieving MCS11 in 80 MHz - CBW with Upstream traffic
    • Priority: 0-Asap
    • Date Time created: 7/14/2020
    • Target Release: PENDING


Workaround:
  • Fill the payload fill type as "PRBS" 
  • Use other constant patterns other than 0s in the traffic field
    • Then after that we have seen we are getting MCS11 in 2SS also.
Root Cause
 
  • Known issue.

Product : WiFi,Spirent TestCenter,WiFi