Interference Issue between 3550-

3700 MHz to DOMSAT Earth Station

(C-band 3700-4200 MHz)

Eric Wong

Kawong_1999@yahoo.com

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

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

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

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

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 ∗ 10�� �� ��

�

• 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

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.

Separation Distance Based on Various

Earth Station Antenna Elevation Degree

No antenna pattern loss and 3GPP minimum requirement

Separation Distance Based on Various Earth Station Antenna

Elevation Degree with BTS Antenna Pattern Loss

Antenna has pattern loss depending on azimuth and elevation

Appendix

Equivalent System Noise Temperature

• ���� = �� + ��

• Antenna Noise Temperature = ��

• �� = Sky Noise + Antenna losses

– Sky Noise is background microwave radiation

• Receiver Noise = ��

• �� is related to Noise Figure

• �� = (Fn-1)To; ��=290k

• �� is the receiver noise factor

• �� = 10(

��

��)

• NF = Noise Figure in dB

NF = 0.7 dB

�� =1.1748976

�� =50.72029

�� = 15+!

"+

$%!

&'

D = antenna diameter in meter (3)

EL = Dish elevation in degree (5)

�� = 61

���� = �� + �� = 111.72029(

BPF1 BPF

LNAFeed

MixerAnt

����