Why RACH failure increase with temperature

In LTE network we observed RACH failure increase with Day-Night temperature difference (Ducting effect).
Is there any correlation with this & how its corelated ?

2 reasons may be the cause for this degradation

  1. Increased interference from NBR sites
  2. Rach access attempts from out of the configured cell radius

Try increasing cell radius or prach config index

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Usually the higher you go, the lower the temperature. But especially near the coastal areas, pressure areas in the air cause tempareture inversion (a layer of air with higher temperature then the one below it). This works as if like a reflective surface for the radio frequencies which increases the range of propagation.
Hence, getting high RACH failures during this time is usually caused by cells overshooting, RACH index (distance of the RACH attempt) being higher than the normal hours, and other distant cells interfering with your base station (especially in case of TDD) causing uplink decoding failures.

You may check by using available counters like TA Index on 4G/5G, Propagation delay on 3G and TA on 2G to confirm if the distances during this time are larger than normal hours.
I hope it helps.