Interference Models
CIR based Interference¶
Per TR 38.821 section 6.1.3.1 the Carrier-to-noise-and-interference ratio (CNIR) of transmission link between satellite and UE can be derived by carrier-to-noise ratio (CNR) and carrier-to-interference ratio (CIR) as follows
\[\begin{equation} CNIR \;[\text{dB}]=-10\log_{10}\left(10^{-0.1\, CNR\;[\text{dB}]}+10^{-0.1\, CIR\;[\text{dB}]}\right) \end{equation}\]
Link Budget Calculations: Example 4 LEO 600 and LEO 1200¶
Case 1:
Assuming a CIR of 5 dB, and using the CNR obtained from the earlier section we get
\[\begin{equation} CNR \;[\text{dB}]= -10\log_{10}\!\left(10^{-0.1\times \left(-1.6\right)}+10^{-0.1\times 5}\right)= -2.46 \text{ dB} \end{equation}\]
Case 2:
Assuming a CIR of 5 dB, and using the CNR obtained from the earlier section we get
\[\begin{equation} CNIR \;[\text{dB}]=-10\log_{10}\left(10^{-0.1\, CNR\;[\text{dB}]}+10^{-0.1\, CIR\;[\text{dB}]}\right) \end{equation}\]
\[\begin{equation} = -10\log_{10}\!\left(10^{-0.1\times \left(-4.62\right)}+10^{-0.1\times 5}\right)= -5.07 \text{ dB} \end{equation}\]
| Simulation Parameters | LEO 600 km | LEO 1200 km |
|---|---|---|
| CNR | 4.36 | \(-\)4.66 |
| CIR | 5 | 5 |
| CNIR | 1.66 | \(-\)5.11 |
Interference power calculations for CIR based Interference
\[\begin{equation} \text{Interference}\;[\text{mW}]=\text{Noise}\;[\text{mW}] \times \left(\frac{CNR\;[\text{mW}] }{CNIR\;[\text{mW}]}-1\right) \end{equation}\]
\[\begin{equation} \text{Interference}\;[\text{dB}]=10\times \log_{10}\!\left(\text{Interference}\;[\text{mW}]\right) \end{equation}\]
Case 1:
Assuming a CNR of 4.36 dB, and using the CNIR of 1.66 dB obtained from the earlier section we get
\[\begin{equation} \text{Interference}\;[\text{mW}]=10^{0.1 \times (-99.05)} \times \left(\frac{10^{0.1 \times 4.36} }{10^{0.1 \times 1.66}}-1\right) \end{equation}\]
\[\begin{equation} \text{Interference}\;[\text{mW}]=1.073 \times 10^{-10} \end{equation}\]
\[\begin{equation} \text{Interference}\;[\text{dB}]=10\times \log_{10}\!\left(1.073 \times 10^{-10} \right)= -99.69 \text{ dB} \end{equation}\]
Case 2:
Assuming a CNR of \(-\)4.62 dB, and using the CNIR of \(-\)5.07 dB obtained from the earlier section we get
\[\begin{equation} \text{Interference}\;[\text{mW}]=10^{0.1 \times (-99.05)} \times \left(\frac{10^{0.1 \times (-4.66)} }{10^{0.1 \times (-5.11)}}-1\right) \end{equation}\]
\[\begin{equation} \text{Interference}\;[\text{mW}]=1.3439 \times 10^{-11} \end{equation}\]
\[\begin{equation} \text{Interference}\;[\text{dB}]=10\times \log_{10}\!\left(1.3439 \times 10^{-11} \right)= -108.71 \text{ dB} \end{equation}\]
Exact geometric interference: In NTN systems, geometric interference arises when multiple beams sharing the same channel ID overlap, leading to co-channel interference at user terminals. The level of interference is influenced by the number of beams and the configured frequency reuse factor. In FR1, interference occurs from all available beams, whereas in FR3, it is limited to beams using the same channel ID.