You have a multinational customer that would like you to perform a wireless site survey for a new manufacturing facility in Singapore. They have had a local vendor install a point-to- point wireless bridge link between two buildings 1 km apart. The ground between the buildings is flat but because facilities are in the mountains, dense fog is an issue. There are no line of sight issues between the buildings. The link is experiencing errors and throughput issues. Currently the two radios are set to operate at 2.4 GHz and the transmit power is set to 7 dBm with 7 dBm antennas. What do you need to take into consideration when performing the site survey for this link?
A. Change the radio power to 17 dBm.
B. Change the radio power to 20 dBm and replace with a 16 dBm antenna.
C. Change the radio power to 29 dBm.
D. Change the radio power to 13 dBm.
(0) Antenna is probably 7 dBi or dBd.
dBm does not make sense as a rating for an antenna.
(1) Regulatory domain lookup:
https://www.cisco.com/c/dam/en/us/products/collateral/wireless/aironet-1300-series/prod_technical_reference0900aecd800f9155.xls
Singapore = ETSI for 2.4 GHz
(2) ETSI EIRP Information:
There exists two EIRP power limits for the 2.4 GHz band, one for 802.11b rates with CCK modulation (1, 2, 5.5 and 11 Mbps) and one for 802.11g/n rates with OFDM modulation. The limit is set to 20 dBm (100 mW) for OFDM and 18 dBm (63 mW) for CCK.
https://wlan1nde.wordpress.com/2014/11/26/wlan-maximum-transmission-power-etsi/
(3) EIRP calculation:
https://www.everythingrf.com/rf-calculators/eirp-effective-isotropic-radiated-power
antenna: 7 dBi
power: 7 dBm
EIRP = 14 dBm
Answer: D
antenna: 7 dBi
power: 13 dBm
EIRP = 20 dBm
(4) dBm to mW
20 dBm = 100 mW
Hell of a question!!!
what a question!!!
I’ve found out that Singapore belongs to ETSI regulatory domain. This implies that “The limit is set to 20 dBm (100 mW) for OFDM and 18 dBm (63 mW) for CCK.”
So Max EIRP is 20 dB (13 TxPower + 7 AntennaGain).
D is Correct
Marcos , Thanks for helping us to clarify this questions, I been studying hard for this test, is this material still valid? , I been learning a lot with this discussions , Thanks a lot
Correct
I could not understand we must look at which authority to Singapore belongs to.
Singapore does not have mountain -.-