Sensing Assisted Interference Management for ISAC
Introduction
Interference management is a cornerstone of cellular network performance. In dense deployments, inter-cell interference (ICI), cross-link interference (CLI) in dynamic TDD, and intra-cell multi-user interference all limit system capacity. Conventional interference management relies on coordination schemes like ICIC/eICIC, CoMP, and IRC receivers, driven by UE measurement reports and network-side traffic predictions.
Sensing-assisted interference management introduces a new dimension: the network can directly observe the physical environment through sensing, identifying interference sources, reflectors, and blockers. This environmental awareness enables more targeted and proactive interference mitigation strategies.
Sensing-Assisted Interference Management Overview
┌──────────────────────────────────────────────────────────────────────┐
│ │
│ ┌──────────────┐ ┌──────────────────────┐ │
│ │ Sensing │ │ Interference │ │
│ │ Subsystem │ │ Mitigation Engine │ │
│ │ │ │ │ │
│ │ ● Target │ Environment ┌────▶│ ● Spatial nulling │ │
│ │ detection │ awareness │ │ ● RB avoidance │ │
│ │ ● Clutter │───────────────────┘ │ ● Power backoff │ │
│ │ mapping │ │ ● Coordination │ │
│ │ ● Interferer│ │ │ │
│ │ localization │ │ │
│ └──────────────┘ └──────────────────────┘ │
│ │
└──────────────────────────────────────────────────────────────────────┘
Key Concepts
Interferer Localization via Sensing
Sensing can detect and localize sources of interference — including:
Neighboring gNBs: Estimating the angular direction of dominant interfering cells.
Reflectors/scatterers: Identifying objects that create strong reflected interference paths.
Dynamic blockers: Detecting moving objects (vehicles, people) that cause time-varying interference.
Once the interferer direction is known, the serving gNB can place spatial nulls in those directions.
Spatial Interference Nulling Using Sensing
┌──────────────────────────────────────────────────────────────────┐
│ │
│ Interfering gNB │
│ ● │
│ ╱ │
│ ╱ Interference │
│ ╱ path (AoA = 45°) │
│ ╱ │
│ ● Serving gNB ● Served UE │
│ ╲ ╱ │
│ ╲ Beam pattern with null at 45° ╱ │
│ ╲ ╱ │
│ ╲═══════════════════════════▶ ╱ Signal beam │
│ │
│ Sensing detects interferer at 45° → null placed at 45° │
│ │
└──────────────────────────────────────────────────────────────────┘
Cross-Link Interference in Dynamic TDD
In dynamic TDD, when one cell transmits downlink while a neighbor transmits uplink on the same resources, cross-link interference (CLI) occurs. Sensing can help by:
Detecting CLI-affected resources: Sensing identifies time-frequency slots with high clutter/interference.
gNB-to-gNB sensing: Direct sensing between gNBs can characterize the CLI channel, enabling pre-cancellation or avoidance.
Dynamic TDD pattern adaptation: Sensing-derived interference maps inform TDD pattern selection across coordinated cells.
Cross-Link Interference Detection via Sensing
┌──────────────────────────────────────────────────────────────────┐
│ │
│ Cell A (DL) Cell B (UL) │
│ ┌──────┐ ┌──────┐ │
│ │gNB A │ ═══DL signal═══▶ │gNB B │ ◀── UL from UE_B │
│ │ │ ◀──CLI──────────│ │ │
│ └──────┘ (interferes └──────┘ │
│ with DL RX │
│ at UE_A) │
│ │
│ Sensing at gNB A detects CLI from gNB B direction │
│ → Scheduler avoids these RBs or applies IRC │
│ │
└──────────────────────────────────────────────────────────────────┘
Environment-Aware Interference Coordination
Sensing builds an interference environment map that captures:
Static reflectors (buildings, walls) that create persistent interference paths.
Dynamic scatterers (vehicles) that cause time-varying interference.
Blockage zones where interference is naturally attenuated.
This map enables the scheduler to perform location-specific frequency reuse, adapting the interference coordination pattern to the physical environment rather than using static frequency planning.
Benefits
Benefit |
Description |
|---|---|
Proactive interference avoidance |
Sensing detects interference sources before they degrade communication. |
Improved spatial nulling |
Direct interferer localization enables precise null placement. |
Dynamic TDD optimization |
CLI can be predicted and mitigated based on sensing observations. |
Environment-adaptive coordination |
Interference management adapts to the physical surroundings. |
Challenges
Sensing-interference separation: Distinguishing between sensing echoes and interference requires careful signal processing, especially when both occupy the same time-frequency resources.
Multi-cell sensing coordination: Effective interference management may require sensing information exchange between cells, increasing signaling overhead.
Computational cost: Real-time interference environment mapping and spatial null computation add processing requirements at the gNB.
Calibration sensitivity: Spatial nulling accuracy depends on precise antenna array calibration; calibration errors reduce null depth and interference suppression effectiveness.