4.2 iRSSblocking

Intro
For this exercise, the blocking response from the receiver has a positive sign as shown in Figure 101. Detailed information on the calculation of the iRSS blocking  can be found in section A5.2 of ANNEX 5:. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Figure 101: Definition of the receiver blocking response 
  

4.2.1 User-defined mode
In this case, the Blocking is provided in dB and represents the attenuation of the receiver at a given frequency offset (see A8.7 ). The resulting receiver attenuation equals the user-defined input values. Then, the iRSS blocking at the interferer operating frequency  may be calculated as follows. 
 ( Note: The ILT bandwidth is not considered in the iRSS blocking  calculation ): 
                                                                           (Eq. 22) 
 
 
 
   
 This can be checked by running a simulation and displaying the iRSS blocking in case of User-defined mode calculated by SEAMCAT. See the figure below. 
 
 
 
 
 
 
 Figure 102: Mean iRSS blocking in case of User-defined mode 
 
 
 
 
 
  

4.2.2 Sensitivity mode
In this calculation mode the function block Max Interf Signal ( Df ) that you entered represents the absolute power level (in dBm) of maximum interfering signal (maximum acceptable interfering power), which might be tolerated by the receiver at a given frequency separation (see  A8.7 ). 
 In this case SEAMCAT calculates the receiver attenuation, Attenuation ( Df ), to be applied to the interfering signal by using the following expression: 
                     
 
 
 
 
 
 
   (Eq. 23) 
   
 where: 
 
 
 D f = ( f ILT - f VLR ) is the frequency separation; 
 
 
 sens VLR is the sensitivity of the VLR (dBm) as defined in the simulation scenario. 
 
 
   
 To achieve a realistic value, you may define the sensitivity ( sens VLR ) as (see the figure below): 
 Sensitivity = Noise Floor + C/(N+I)

 
 Sensitivity = -110 dBm + 16 = -94 dBm 
 
   
  Figure 103: Setting up the sensitivity in SEAMCAT 
 Then the attenuation may be evaluated: 
 Attenuation (Df ) = 40 + 94 + 16 - 0 = 150 dB

 
 iRSS blocking = Interfering Signal Level (f it )= -54.5 - 150 = -204.5 dBm

 
   
 This can be checked by running a simulation and displaying the iRSS blocking in case of Sensitivity mode calculated by SEAMCAT see Figure 104. 
 
 
 
 
 
 
 Figure 104: Mean iRSS blocking in case of Sensitivity mode 
 
 
 
 
 
  

4.2.3 Protection ratio
This mode is identical to the “sensitivity” mode since the only difference is that the Blocking value (relative to the noise floor) is provided in dB. The software processes the information using exactly the same method to obtain the value of the receiver attenuation (see  A8.7 ). 
 The function block Protection Ratio ( Df ) that you entered represents the protection ratio, i.e. the ratio of maximum acceptable level of interfering signal to the wanted signal level, at a given frequency separation. 
 In this case SEAMCAT calculates the receiver attenuation a VLR ( Df ) to be applied to the interfering signal by using the following expression (see Figure 105): 
 (Eq. 24)    
 
 
 
   
   

 
                     

                       
 
 
 
 
 
 
 Figure 105: Mean iRSS blocking in case of Protection-ratio mode