AP transmit power 20dBm, antenna gain 4dBi, cable and device loss 1dB, terminal receiving antenna gain 2dBi, space propagation loss 80dB, terminal receiving level RSSI= ().

Question

Options

• A-57
• B-56
• C-55
• D-54

• A
  4% (1)
• B
  72% (18)
• C
  8% (2)
• D
  16% (4)

Explanation

Option B (-56 dBm) is correct when applying the full link budget formula: RSSI = TX Power + TX Antenna Gain − TX Cable/Device Loss + RX Antenna Gain − RX Cable/Device Loss − Path Loss. The key insight is that the 1 dB cable/device loss applies at both the transmitting and receiving ends (1 dB + 1 dB = 2 dB total loss), giving: 20 + 4 − 1 + 2 − 1 − 80 = −56 dBm.

Option C (−55) is the most common trap - it results from applying the 1 dB cable loss only once (one side only), yielding 20 + 4 − 1 + 2 − 80 = −55. Options A (−57) and D (−54) reflect arithmetic errors, such as doubling the antenna gains or misapplying signs on the path loss term.

Memory tip: Think of cable/device loss like a toll on a highway - you pay it leaving (TX side) and arriving (RX side). When a question says "cable and device loss" without specifying one end, assume it's a shared system loss applied symmetrically to both sides.

No community discussion yet for this question.