# 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<sub data-renderer-mark="true">blocking</sub> can be found in section A5.2 of ANNEX 5:.

<div class="rich-media-item mediaSingleView-content-wrap image-align-start css-v4trle" data-layout="align-start" data-media-vc-wrapper="true" data-node-type="mediaSingle" data-renderer-start-pos="208" data-vc="media-single" data-width="672" data-width-type="pixel" id="bkmrk-"><div class="css-1l7v0un"><div class="css-vhfmu2" contenteditable="false" data-media-badges="true" data-testid="media-badges">  
</div><div data-alt="" data-collection="contentId-512138" data-context-id="512138" data-file-mime-type="" data-file-name="file" data-file-size="1" data-height="452" data-id="ebe8e239-416e-4fd6-be51-7c2889800e8c" data-node-type="media" data-renderer-start-pos="209" data-type="file" data-width="1215"><div class="_2rko18qm _vchhusvi _kqswh2mm _ect4ttxp _p12f1osq _c71l1osq _1bsb1qmm _4t3ine4n _1hlmd0i9 _1rquusvi _eg541i5c _mts3kb7n _1ntskb7n _yfmhtlke _5sb1v00u new-file-experience-wrapper" data-media-vc-wrapper="true" data-testid="media-card-view"><div class="_1reo15vq _18m915vq _2rko18qm _1e0c1txw _kqswh2mm _p12f1osq _1bsb1osq _4t3i1osq _c71l1osq media-file-card-view" data-cursor="pointer" data-test-media-name="101.png" data-test-progress="1" data-test-source="remote" data-test-status="complete" data-testid="media-file-card-view"><div class="_kqswstnw _1bsb1osq _4t3i1osq _1e0c1txw _2lx21bp4 _1bah1h6o _4cvr1h6o" data-testid="ImageRendererWrapper">![](blob:https://ecowiki.atlassian.net/ad7cee53-6e83-46a5-ba8f-abc28ac29329#media-blob-url=true&id=ebe8e239-416e-4fd6-be51-7c2889800e8c&collection=contentId-512138&contextId=512138&width=1215&height=452&alt=&clientId=113268fe-fe5b-4bc3-8ff3-07965dbf1d18)</div></div></div></div></div></div>[![image.png](https://wiki.cept.org/uploads/images/gallery/2026-04/scaled-1680-/hvGEXeVhnLlYE5yE-image.png)](https://wiki.cept.org/uploads/images/gallery/2026-04/hvGEXeVhnLlYE5yE-image.png)

<div class="fabric-editor-block-mark fabric-editor-alignment align-center" data-align="center" id="bkmrk-figure-101%3A-definiti">**Figure 101: Definition of the receiver blocking response**</div>

# 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](https://ecowiki.atlassian.net/wiki/spaces/SH/pages/492697 "https://ecowiki.atlassian.net/wiki/spaces/SH/pages/492697")). The resulting receiver attenuation equals the user-defined input values. Then, the iRSS<sub data-renderer-mark="true">blocking</sub> *<u data-renderer-mark="true">at the interferer operating frequency </u>* may be calculated as follows.

(***Note:** <u data-renderer-mark="true">The <span data-highlighted="true" data-vc="highlighted-text"><span class="_kqswh2mm"><span class="_5pioz8co _189e1dm9 _1il9buyh _19lc184f _d0altlke" data-testid="definition-highlighter">ILT</span></span></span> bandwidth is not considered in the iRSS</u><sub data-renderer-mark="true"><u data-renderer-mark="true">blocking</u></sub><u data-renderer-mark="true"> calculation</u>*):

 *(Eq. 22)*

[![image.png](https://wiki.cept.org/uploads/images/gallery/2026-04/scaled-1680-/EDEZPTaIeW2SuR77-image.png)](https://wiki.cept.org/uploads/images/gallery/2026-04/EDEZPTaIeW2SuR77-image.png)

[![image.png](https://wiki.cept.org/uploads/images/gallery/2026-04/scaled-1680-/1riX8DbwQCEM50mx-image.png)](https://wiki.cept.org/uploads/images/gallery/2026-04/1riX8DbwQCEM50mx-image.png)

[![image.png](https://wiki.cept.org/uploads/images/gallery/2026-04/scaled-1680-/ihB6hCvvQNurn7ac-image.png)](https://wiki.cept.org/uploads/images/gallery/2026-04/ihB6hCvvQNurn7ac-image.png)

This can be checked by running a simulation and displaying the iRSS<sub data-renderer-mark="true">blocking</sub> in case of User-defined mode calculated by SEAMCAT. See the figure below.

![image.png](https://wiki.cept.org/uploads/images/gallery/2026-04/scaled-1680-/RHVsRlUxjOx4Io3W-image.png)

<div class="rich-media-item mediaSingleView-content-wrap image-align-start css-1st0j63" data-layout="align-start" data-media-vc-wrapper="true" data-node-type="mediaSingle" data-renderer-start-pos="650" data-vc="media-single" data-width="210" data-width-type="pixel" id="bkmrk-figure-102%3A-mean-irs"><div class="css-1ft98hw"><div data-alt="" data-collection="contentId-494034" data-context-id="494034" data-file-mime-type="image/png" data-file-name="image2016-8-8 10:59:3.png" data-file-size="16624" data-height="110" data-id="8c5e3e73-10e0-4fff-b54d-9aa6b2c45a1a" data-node-type="media" data-renderer-start-pos="651" data-type="file" data-width="210"><div class="_2rko18qm _vchhusvi _kqswh2mm _ect4ttxp _p12f1osq _c71l1osq _1bsb1qmm _4t3ine4n _1hlmd0i9 _1rquusvi _eg541i5c _mts3kb7n _1ntskb7n _yfmhtlke _5sb1v00u new-file-experience-wrapper" data-media-vc-wrapper="true" data-testid="media-card-view" id="bkmrk-figure-102%3A-mean-irs-1"><div class="_1reo15vq _18m915vq _2rko18qm _1e0c1txw _kqswh2mm _p12f1osq _1bsb1osq _4t3i1osq _c71l1osq media-file-card-view" data-cursor="pointer" data-test-media-name="image2016-8-8 10:59:3.png" data-test-progress="1" data-test-source="remote" data-test-status="complete" data-testid="media-file-card-view"><div class="_kqswstnw _1bsb1osq _4t3i1osq _1e0c1txw _2lx21bp4 _1bah1h6o _4cvr1h6o align-center" data-testid="ImageRendererWrapper">![](blob:https://ecowiki.atlassian.net/fa639a8c-9a0e-48a4-8fd4-3261fba59b66#media-blob-url=true&id=8c5e3e73-10e0-4fff-b54d-9aa6b2c45a1a&collection=contentId-494034&contextId=494034&width=210&height=110&alt=&clientId=113268fe-fe5b-4bc3-8ff3-07965dbf1d18)**Figure 102: Mean iRSS<sub data-renderer-mark="true">blocking</sub> in case of User-defined mode**</div></div></div></div></div></div>

# 4.2.2 Sensitivity mode

In this calculation mode the function *block<sub data-renderer-mark="true">Max Interf Signal </sub>*(*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](https://ecowiki.atlassian.net/wiki/spaces/SH/pages/492697 "https://ecowiki.atlassian.net/wiki/spaces/SH/pages/492697")).

In this case SEAMCAT calculates the receiver attenuation, Attenuation (*Df*), to be applied to the interfering signal by using the following expression:

 [![image.png](https://wiki.cept.org/uploads/images/gallery/2026-04/scaled-1680-/a4rFxolbIjEp2vdB-image.png)](https://wiki.cept.org/uploads/images/gallery/2026-04/a4rFxolbIjEp2vdB-image.png)

<div class="fabric-editor-block-mark fabric-editor-alignment align-right" data-align="end" id="bkmrk-%C2%A0-%28eq.-23%29"><div class="inline-extension-renderer css-e2q2ep"><div class="_kqswh2mm" data-testid="ForgeExtensionContainer"><div class="_19itglyw _vchhusvi _r06hglyw _kqswh2mm" data-testid="hosted-resources-iframe-container"></div></div></div> *(Eq. 23)*</div>where:

- D*f* = (*f<sub data-renderer-mark="true">ILT </sub>- f<sub data-renderer-mark="true"><span data-highlighted="true" data-vc="highlighted-text"><span class="_kqswh2mm"><span class="_5pioz8co _189e1dm9 _1il9buyh _19lc184f _d0altlke" data-testid="definition-highlighter">VLR</span></span></span></sub>*) is the frequency separation;
- *sens<sub data-renderer-mark="true"><span data-highlighted="true" data-vc="highlighted-text">VLR</span></sub>* is the sensitivity of the <span data-highlighted="true" data-vc="highlighted-text">VLR</span> (dBm) as defined in the simulation scenario.

To achieve a realistic value, you may define the sensitivity (*sens<sub data-renderer-mark="true"><span data-highlighted="true" data-vc="highlighted-text">VLR</span></sub>*) as (see the figure below):

*Sensitivity = Noise Floor + C/(N+I)*

*Sensitivity = -110 dBm + 16 = -94 dBm*

![image.png](https://wiki.cept.org/uploads/images/gallery/2026-04/scaled-1680-/eD68FTJhVdkIBVmc-image.png)

 **Figure 103: Setting up the sensitivity in SEAMCAT**

Then the attenuation may be evaluated:

*Attenuation (Df ) = 40 + 94 + 16 - 0 = 150 dB*

*iRSS<sub data-renderer-mark="true">blocking</sub> = Interfering Signal Level (f it )= -54.5 - 150 = -204.5 dBm*

This can be checked by running a simulation and displaying the iRSS<sub data-renderer-mark="true">blocking</sub> in case of Sensitivity mode calculated by SEAMCAT see Figure 104.

![image.png](https://wiki.cept.org/uploads/images/gallery/2026-04/scaled-1680-/ec17LjJel6juKyYK-image.png)

<div class="rich-media-item mediaSingleView-content-wrap image-center css-5q9nr0" data-layout="center" data-media-vc-wrapper="true" data-node-type="mediaSingle" data-renderer-start-pos="1250" data-vc="media-single" data-width="207" data-width-type="pixel" id="bkmrk-figure-104%3A-mean-irs"><div class="css-1u1meee"><div data-alt="" data-collection="contentId-494077" data-context-id="494077" data-file-mime-type="" data-file-name="file" data-file-size="1" data-height="115" data-id="645b8750-7027-458b-accf-ea7c788231fa" data-node-type="media" data-renderer-start-pos="1251" data-type="file" data-width="207"><div class="_2rko18qm _vchhusvi _kqswh2mm _ect4ttxp _p12f1osq _c71l1osq _1bsb1qmm _4t3ine4n _1hlmd0i9 _1rquusvi _eg541i5c _mts3kb7n _1ntskb7n _yfmhtlke _5sb1v00u new-file-experience-wrapper" data-media-vc-wrapper="true" data-testid="media-card-view" id="bkmrk-figure-104%3A-mean-irs-1"><div class="_1reo15vq _18m915vq _2rko18qm _1e0c1txw _kqswh2mm _p12f1osq _1bsb1osq _4t3i1osq _c71l1osq media-file-card-view" data-cursor="pointer" data-test-media-name="image2016-8-8 10:59:53.png" data-test-progress="1" data-test-source="remote" data-test-status="complete" data-testid="media-file-card-view"><div class="_kqswstnw _1bsb1osq _4t3i1osq _1e0c1txw _2lx21bp4 _1bah1h6o _4cvr1h6o" data-testid="ImageRendererWrapper">![](blob:https://ecowiki.atlassian.net/0f141d5e-2c94-49df-8f71-3b6b86b53306#media-blob-url=true&id=645b8750-7027-458b-accf-ea7c788231fa&collection=contentId-494077&contextId=494077&width=207&height=115&alt=&clientId=113268fe-fe5b-4bc3-8ff3-07965dbf1d18)**Figure 104: Mean iRSS<sub data-renderer-mark="true">blocking</sub> in case of Sensitivity mode**</div></div></div></div></div></div>

# 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](https://ecowiki.atlassian.net/wiki/spaces/SH/pages/492697 "https://ecowiki.atlassian.net/wiki/spaces/SH/pages/492697")).

The function *block<sub data-renderer-mark="true">Protection Ratio</sub>*(*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<sub data-renderer-mark="true">VLR</sub>*(*Df*) to be applied to the interfering signal by using the following expression (see Figure 105):

*(Eq. 24)*

[![image.png](https://wiki.cept.org/uploads/images/gallery/2026-04/scaled-1680-/GZW81QnpOQGHceTW-image.png)](https://wiki.cept.org/uploads/images/gallery/2026-04/GZW81QnpOQGHceTW-image.png)

[![image.png](https://wiki.cept.org/uploads/images/gallery/2026-04/scaled-1680-/7bMtDiIykGnBdjjZ-image.png)](https://wiki.cept.org/uploads/images/gallery/2026-04/7bMtDiIykGnBdjjZ-image.png)

[![image.png](https://wiki.cept.org/uploads/images/gallery/2026-04/scaled-1680-/xR43Rds7Q0tzHqSr-image.png)](https://wiki.cept.org/uploads/images/gallery/2026-04/xR43Rds7Q0tzHqSr-image.png)

[![image.png](https://wiki.cept.org/uploads/images/gallery/2026-04/scaled-1680-/n8ZFCYfy45LY4C7J-image.png)](https://wiki.cept.org/uploads/images/gallery/2026-04/n8ZFCYfy45LY4C7J-image.png)

<div class="rich-media-item mediaSingleView-content-wrap image-align-start css-1u5mjaf" data-layout="align-start" data-media-vc-wrapper="true" data-node-type="mediaSingle" data-renderer-start-pos="782" data-vc="media-single" data-width="236" data-width-type="pixel" id="bkmrk-figure-105%3A-mean-irs"><div class="css-uxysyr"><div data-alt="" data-collection="contentId-494086" data-context-id="494086" data-file-mime-type="image/png" data-file-name="image2016-8-8 11:0:36.png" data-file-size="21146" data-height="132" data-id="aabbda9a-ddef-4fb8-a579-902ac5eb2f21" data-node-type="media" data-renderer-start-pos="783" data-type="file" data-width="236"><div class="_2rko18qm _vchhusvi _kqswh2mm _ect4ttxp _p12f1osq _c71l1osq _1bsb1qmm _4t3ine4n _1hlmd0i9 _1rquusvi _eg541i5c _mts3kb7n _1ntskb7n _yfmhtlke _5sb1v00u new-file-experience-wrapper" data-media-vc-wrapper="true" data-testid="media-card-view" id="bkmrk-figure-105%3A-mean-irs-1"><div class="_1reo15vq _18m915vq _2rko18qm _1e0c1txw _kqswh2mm _p12f1osq _1bsb1osq _4t3i1osq _c71l1osq media-file-card-view" data-cursor="pointer" data-test-media-name="image2016-8-8 11:0:36.png" data-test-progress="1" data-test-source="remote" data-test-status="complete" data-testid="media-file-card-view"><div class="_kqswstnw _1bsb1osq _4t3i1osq _1e0c1txw _2lx21bp4 _1bah1h6o _4cvr1h6o align-center" data-testid="ImageRendererWrapper">![](blob:https://ecowiki.atlassian.net/d6adea82-baea-410b-8dff-220d62a225fa#media-blob-url=true&id=aabbda9a-ddef-4fb8-a579-902ac5eb2f21&collection=contentId-494086&contextId=494086&width=236&height=132&alt=&clientId=113268fe-fe5b-4bc3-8ff3-07965dbf1d18)**Figure 105: Mean iRSS<sub data-renderer-mark="true">blocking</sub> in case of Protection-ratio mode**</div></div></div></div></div></div>