Distortion may come from several sources such as bad Ethernet cables (poor shield, damaged, or low quality), path degradations such as multipath, or Fresnel zone encroachment.
Interference can come from other transmitters on the tower, as well as from sources inside an indoor shelter. High power transmitters inside a shelter can cause interference when near the PoE device or when located very close to the cabling.
There are maximum acceptable MSE values for each modulation which are useful in determining the quality of the link. The MSE value reported is only relevant to one tx-rx path, so the MSE of each tx-rx path must be evaluated to verify the link is operating as expected. The lower the number the better, so a -35dB is better than a -30dB.
Other possible causes for unacceptable MSE
These include
- XPIC parameters are incorrect
- Insufficient isolation between polarisations on an XPIC link
- Insufficient performance to support high QAM modulation
- Inbalance between paths on an XPIC dual polarity link
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