Diversity & Fading in Microwave Links

[Mohamed.Saeed]

• Diversity is a Way to improve the microwave Link performance

• There’s multiple types of diversity , common types are :

  1. Space diversity
  2. Frequency diversity

• Theory of diversity is to receive the signal at the Rx side in 2 frequency channels or through 2 different antennas

• Diversity aims to improve the performance because the 2 signals received could have different BER or signal strength and different performance

• We use diversity to solve the fading issues

• We have mainly 2 types of Fading :

  1. Multipath fading
  2. Rain fading

• Multipath fading is focused with low frequency channels like 3-15 GHz

• Rain fading is effective in high frequency range 15-80 GHz

• From 13-18 GHz microwave Links expect both fading types

• We can increase the fade margin by using these 2 factors :

  1. Using vertical polarization
  2. Use lower modulation

• Drawback from using lower modulation :

  1. decreasing the system capacity/ throughput

• Drawbacks from using diversity :

  1. increasing the system cost since we have to use 2 antennas , or 2 different channels

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