Problem 2.
3:
In a mobile communication network, the minimum required signal to noise ratio is 12 dB. The
background noise at the frequency of operation is -115 dBm. If the transmit power is 10W,
transmitter antenna gain is 3dBi, the receiver antenna gain is 2dBi, the frequency of operation is
800 MHz. and the base station and mobile antenna heights are 100m and 1.4m respectively.
Determine the maximum in building penetration loss that is acceptable for a base station with a
coverage of 5km if the following path loss models are used:
1) Free space path loss model
2) Two-ray path loss model
Solution:
Transmit Power Pt = 10W
Convert to dBm:
10logPt = 10log(10W / 1 mW) = 40 dBm.
Frequency, f = 800 MHz
Distance : d =5 km = 5000 meters
Transmitter antenna Gain , Gt = 3 dBi
Receiver antenna Gain , Gr= 2 dBi
Convert antenna gains to dBm :
Transmitter Antenna Gain Gr = 5.15dBm
Receiver Antenna Gain Gr = 4.15dBm
1) Free Space Path loss model.
Pr = Pt * Gt * Gr * (λ / 4* ∏ * d)2
Received power at distance one meter i.e. d = 1,
Po = Pt * Gt * Gr * ( λ / 4* ∏ )2
10logPo = 10logPt + 10logGt + 10logGr + 20log( λ / 4* ∏ )
= 40 + 5.15 + 4.15 + 20 * log (0.375/(4 * 3.14)) (because λ= c/f = 0.375)
= 40 + 5.15 + 4.15 + 20 * log (0.02985)
= 40 + 5.15 + 4.15 + 20 *(-1.5250)
= 49.30 – 30.50
= 18.80 dBm
Now,
Pr = Po / d2
10logPr = 10logPo - 20log( d )
= 18.80 - 20 log(5000)
= 18.80 – 73.98
= -55.18 dBm
Therefore,
Path Loss :
L = 10logPt - 10logPr
= 40 – (-55.18)
= 95.18 dBm……………….Ans of Path Loss
2) Two Ray Path loss model.
Pr = Pt * Gt * Gr * ((hb2 * hm2)/d4)
Received power at distance one meter i.e. d = 1,
10logPr = 10logPt + 10logGt + 10logGr + 20log(hb) + 20log(hm) – 40 log(d)
= 40 + 5.15 + 4.15 + 20*log (100) + 20*log (1.4) - 40*log (5000)
= 40 + 5.15 + 4.15 + 40 + 2.922 – 147.959
= -55.737 dBm
Therefore,
Total Path Loss :
L = 10logPt - 10logPr
= 40 – (-55.737)
= 95.737 dBm……………….Ans of Path Loss