Co-Frequency Interference Analysis and Dynamic Simulation Validation of Satellite-Direct-to-Device Systems Against Terrestrial IMT Networks in Cross-Border Scenarios

LIU Quan; ZHAO Weisong; XIAO Na; SONG Yanjun; ZHOU Meng; ZHANG Zhili; WANG Jinhai; WANG Lichong

doi:10.11999/JEIT260263

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LIU Quan, ZHAO Weisong, XIAO Na, SONG Yanjun, ZHOU Meng, ZHANG Zhili, WANG Jinhai, WANG Lichong. Co-Frequency Interference Analysis and Dynamic Simulation Validation of Satellite-Direct-to-Device Systems Against Terrestrial IMT Networks in Cross-Border Scenarios[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT260263

Citation:

LIU Quan, ZHAO Weisong, XIAO Na, SONG Yanjun, ZHOU Meng, ZHANG Zhili, WANG Jinhai, WANG Lichong. Co-Frequency Interference Analysis and Dynamic Simulation Validation of Satellite-Direct-to-Device Systems Against Terrestrial IMT Networks in Cross-Border Scenarios[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT260263

Citation:

LIU Quan, ZHAO Weisong, XIAO Na, SONG Yanjun, ZHOU Meng, ZHANG Zhili, WANG Jinhai, WANG Lichong. Co-Frequency Interference Analysis and Dynamic Simulation Validation of Satellite-Direct-to-Device Systems Against Terrestrial IMT Networks in Cross-Border Scenarios[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT260263

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Co-Frequency Interference Analysis and Dynamic Simulation Validation of Satellite-Direct-to-Device Systems Against Terrestrial IMT Networks in Cross-Border Scenarios

doi: 10.11999/JEIT260263 cstr: 32379.14.JEIT260263

1.
The 54th Research Institute of China Electronics Technology Group Corporation, Shijiazhuang 050081, China
2.
China Communication System Company Ltd., Beijing 100070, China

Funds: National Natural Science Foundation of China (62231012), The National Science and Technology Major Project of the Ministry of Industry and Information Technology (MIIT) for Mobile Information Networks (2024ZD1300800)

Received Date: 2026-03-09
Accepted Date: 2026-06-24
Rev Recd Date: 2026-06-17

Available Online: 2026-07-02

Abstract

Abstract

Objective Satellite-Direct-to-Device (SD2D) systems that reuse terrestrial IMT spectrum may generate harmful downlink interference to incumbent IMT networks in neighboring administrations, particularly in cross-border deployments where SD2D downlinks overlap the receive bands of both IMT user equipment (UE) and IMT Base Stations (BSs). A practical coexistence methodology is therefore required to (i) translate IMT receiver protection criteria into explicit Power Flux Density (PFD) and Equivalent Power Flux Density (EPFD) constraints and (ii) validate these constraints using a dynamic simulation framework so that they can be converted into enforceable geographic coordination measures, such as minimum isolation distances. This study focuses on the dominant interference path, namely SD2D downlink interference to IMT receivers, and establishes a traceable workflow from deterministic protection limits to dynamic simulation validation and the corresponding minimum isolation distances. Methods A cross-border scenario is modeled in which Country A deploys an SD2D system and Country B operates a terrestrial IMT network. Two representative downlink frequencies, 1995 MHz and 2 190 MHz, are evaluated for two representative Starlink configurations, Starlink-1 and Starlink-2. The IMT network is modeled using ITU-R- and 3GPP-compliant parameters, with an I/N protection threshold of –6 dB and a target percentile κ (baseline κ=99.5%) for both IMT UEs and BSs. Satellite transmit antennas follow the ITU-R S.1528 reference pattern, IMT BS receive antennas follow the ITU-R F.1336 sector pattern, and IMT UEs are modeled with omnidirectional antennas. A back-lobe blockage model is incorporated into both satellite and BS antenna patterns to account for rear-side shielding. Signal propagation follows the ITU-R P.619 model, using free-space path loss as the conservative baseline, while an optional clutter-loss term is incorporated through a clutter-occurrence probability. Deterministic protection limits are derived by calculating the maximum permissible aggregate PFD for IMT UE protection and the maximum permissible aggregate EPFD for IMT BS protection. A dynamic simulation framework then validates these limits and searches for the required minimum isolation distances (Fig. 4). Co-channel beam isolation angles are optimized using the C/I Complementary Cumulative Distribution Function (CCDF), and a segmented search algorithm determines the minimum UE- and BS-side isolation distances together with the corresponding κ-percentile PFD/EPFD statistics. Results and Discussions The deterministic analysis yields a maximum permissible aggregate PFD of –102.72 dBW/m²/MHz at 2 190 MHz for IMT UEs and a maximum permissible aggregate EPFD of –129.53 dBW/m²/MHz at 1995 MHz for IMT BSs (Fig. 3). For Starlink-1, the C/I design criterion yields a minimum co-channel beam isolation angle pair of (12°, 12°) (Fig. 5). Dynamic simulation shows that, under the representative baseline configuration with an I/N threshold of –6 dB and κ=99.5%, the minimum isolation distances are 195 km for UE protection and 290 km for BS protection (Fig. 6, Fig. 7, and Table 4). The resulting coordination isolation distance is therefore 290 km, and the simulated κ-percentile PFD and EPFD agree with the deterministic protection limits, with a residual margin below 0.5 dB. For Starlink-2, the optimized co-channel beam isolation angles increase to (15°, 15°), and the corresponding minimum isolation distances increase to 272 km for UEs and 420 km for BSs under the same baseline configuration (Table 5). These baseline distances should be interpreted as representative values for the specified simulation configuration rather than unique, strictly converged results. Stability verification shows that, under different sampling intervals, simulation durations, and random seeds, the UE- and BS-side minimum isolation distances remain within 195～210 km and 290～300 km, respectively, for Starlink-1, and within 266～290 km and 370～420 km, respectively, for Starlink-2 (Table 7). Sensitivity analysis for Starlink-1 further indicates that the required minimum isolation distance is governed by the upper tail of the aggregate I/N distribution (Table 6). Increasing κ from 99.5% to 100% increases the UE- and BS-side minimum isolation distances from 195/290 km to 304/560 km. Clutter attenuation substantially reduces the UE-side minimum isolation distance, decreasing it to 173 km when the clutter-occurrence probability is 0.5, while producing little change in BS protection. Polarization reuse increases the UE- and BS-side minimum isolation distances to 222 km and 360 km, respectively, whereas increasing the number of co-channel beams to 16 increases the BS-side minimum isolation distance to 330 km. The minimum service elevation angle and the link establishment strategy are identified as the dominant operational factors. Changing the minimum service elevation angle from 10° to 35° changes the required UE- and BS-side minimum isolation distances from 340/460 km to 101/150 km, whereas replacing the Sat-MaxElevation strategy with the UE-MaxElevation strategy reduces them to 80/180 km. Conclusions The proposed workflow converts IMT receiver protection criteria into deterministic protection limits expressed as PFD and EPFD constraints and validates them using a dynamic simulation framework. Under an I/N threshold of –6 dB and κ=99.5%, the baseline and stability analyses jointly indicate representative UE- and BS-side minimum isolation-distance ranges of 195～210 km and 290～300 km for Starlink-1 and 266～290 km and 370～420 km for Starlink-2, rather than unique, strictly converged values. Sensitivity analysis further shows that κ only changes the statistical criterion used to extract tail events from the sample set, whereas clutter attenuation primarily benefits IMT UEs. In contrast, the minimum service elevation angle, polarization reuse, the number of co-channel beams, and the link establishment strategy reshape the worst-case interference geometry and can produce substantial, and sometimes non-monotonic, changes in the required minimum isolation distances. The proposed framework establishes a traceable link between IMT receiver protection criteria and enforceable border coordination measures.
- Satellite-Direct-to-Device (SD2D),
- IMT,
- Co-frequency interference,
- Cross-border coordination,
- Isolation distance

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References(27)

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