Interference issue between 3550 3700 m hz to domsat earth-station
1. Interference Issue between 3550-
3700 MHz to DOMSAT Earth Station
(C-band 3700-4200 MHz)
Eric Wong
Kawong_1999@yahoo.com
2. Possible Interference
CBS (TDD/FDD LTE WiFi) DOMSAT earth station receive
3700 42003650
Interference
20 MHz
Channel
LTE: 1.4 – 20 MHz Channel
WiFi: 20-80 MHz Channel
3. Problem Statement
• There are over 5,000 C-Band earth station licensed in the US.
• The out of band emission from transmitter operating in 3650-3700 MHz
will become in-band interference to 3700-4200 MHz (C-Band earth station
received frequency)
– Mostly for channel that are immediately adjacent to each others
– Mobile device will not be a concern due to the low transmit power
(40mw/MHz or 1w/25 MHz)
• Allowing signal to be transmitter in 3650-3700 MHz will be problematic for
incumbent C-Band earth station (assuming the distance is close between
each other)
• Interference signal can degrade signal quality or block service completely
• Many of the Earth Station today do not have the ability to integrate a filter
to increase the Adjacent Channel Selectivity
• In order to spectrum share, coordination is required.
• Exclusion zone will be required to protect the earth station from harmful
interference
4. 3GPP OOBE
• OOBE (out of band emission) is the unwanted
signal outside of the channel bandwidth resulting
from non-linearity in the transmitter (LTE, WiFi)
• 3GPP OOBE is define by ACLR
– ACLR = Adjacent Channel Leakage Ratio
– ACLR is the ratio of the filtered mean power centered
on the assigned channel frequency to the filtered
mean power centered on an adjacent channel
frequency
• Base Station ACLR = 45 dB
• Portable Device ACLR = 30 dB
5. Mitigation Methods
• Mitigation methods to ensure earth station are
protected from harmful interference cause by adjacent
channel (LTE, WiFi):
– Installing filters at the LTE, WiFi transmitter to reduce the
out of band emission
• That mean improve the ACLR of LTE, WiFi transmitter
– Installing filters at the earth station receivers to improve
adjacent channel selectivity
• Improve adjacent channel rejection
– Increase the separation distance between earth station
and LTE, WiFi transmitter
– Increase the guard band size between the two adjacent
chanel
6. Earth Station Receiver Interference to
Noise Specification
• According to ITU-R SF.1006, Co-channel Interference to Noise
(I/N) = - 10dB
• This means the Interference has to be 10 dB below the Earth
Station receiver system noise
• Earth Station system noise =
– kTB
• K = Boltzmann constant ~ 1.38 ∗ 10ିଶଷ ௨௦
• T = Temperature in Kevin ~ 111.72029 (see appendix)
• B = Bandwidth ~ 1 MHz
• kTB ~ -118 dBm ~ -148 dBW
• In order to meet the I/N of -10 dB, the Interference has to 10
dB below the system noise
– I= N- 10 dB
– -148 dBw – 10 dB = -158 dBW
7. Separation Distance Requirement
• Base on FCC 12-148 NPRM and Order, BTS are
limited to 25 watts per 25 MHz EIRP and the peak
EIRP power density shall not exceed 1 watt in any
1 MHz slice of spectrum
• Lets assume the 10 MHz LTE TDD system
• The peak EIRP will be 10 watts ~ 10 dBW
• The OOBE will be 10 dBW – 45 dBc = -35 dBW
• In order to meet the -158 dBW co-channel I/N
ratio requirement, pathloss of 123 dB ~ 9.3 km is
needed.
8. Separation Distance Based on Various
Earth Station Antenna Elevation Degree
No antenna pattern loss and 3GPP minimum requirement
9. Separation Distance Based on Various Earth Station Antenna
Elevation Degree with BTS Antenna Pattern Loss
Antenna has pattern loss depending on azimuth and elevation
