1 Answer

The carrier-to-Interference (C/I) ratio is the ratio, expressed in dB, between a desired carrier (C) and an interfering carrier

(1) received by the same receiver, which is called the "victim" receiver. The desired carrier level and the interfering

carrier level are calculated and measured in dBm.

For convenience, we normally use the C/I ratio to determine whether an interference case is acceptable or not. The carrier

signal level (C) and the interfering signal level (I) can be expressed as follows.

1.2.1 Equation for Determining Desired Carrier Power

C = PTD + GTD + GRD - FSLD - LWGTD - LWGRD

(6)

Where,

C

is the received desired carrier power.

PTD

is the transmit power from the desired station in dBm.

GTD

is the antenna gain of the desired transmit station in dB.

GRD

is the antenna gain of the desired receive station in dB.

FSLD

is the free-space loss of the desired path in dB.

LWGTD

is the loss of the waveguide of the desired transmit station.

LWGRD

is the loss of the waveguide of the desired receive station.

1.2.2 Equation for Determining Interference Carrier Power

I = PTI + GTI + GRD - GCD - FSLI- LWGTI - LWGRD

(7)

Where,

I

is the received interfering carrier power.

PTI

is the transmit power from the interfering station in dBm.

GTI

is the antenna gain of the interfering transmit station in dB.

GRD

is the antenna gain of the desired receive station in dB measured at the angle of arrival of the

interfering signal.

GCD

is the combined angular discrimination of the two antennas at their respective discrimination

angles.

FSLI

is the free space loss of the interfering path in dB.

LWGTI

is the loss of the waveguide of the interfering transmit station.

LWGRD

is the loss of the waveguide of the desired receive station.

The C/I ratio in dB is calculated as the difference between Equations (6) and (7).

http://www.nsma.org/recommendation/wg5-92-08.pdf