Radio Resource Management (RRM)

The mechanism of dynamically adjusting the transmission power of a base station or user equipment to manage interference and conserve energy. The primary goal is to maintain the target Signal-to-Interference-plus-Noise Ratio (SINR) while minimizing the overall power footprint.

• Open-loop control: Estimates path loss based on downlink measurements without feedback.
• Closed-loop control: Uses explicit feedback commands from the receiver to fine-tune power in real-time.
• Fractional Power Control (FPC) : A standardized LTE/5G method that partially compensates for path loss to balance cell-edge performance and inter-cell interference.

The process of dynamically selecting the Modulation and Coding Scheme (MCS) based on real-time channel conditions. By evaluating the Channel Quality Indicator (CQI) reported by the User Equipment, the scheduler maximizes spectral efficiency.

• Adaptive Modulation: Switches between QPSK, 16QAM, 64QAM, and 256QAM based on SINR.
• Code Rate Adjustment: Varies the amount of forward error correction redundancy to protect against bit errors.
• Outer Loop Link Adaptation (OLLA) : Corrects CQI estimation errors by adjusting the SINR offset based on Hybrid Automatic Repeat Request (HARQ) statistics.

An algorithm that determines which users are allocated Physical Resource Blocks (PRBs) in each Transmission Time Interval (TTI). The scheduler must balance competing objectives of throughput, fairness, and latency.

• Maximum Throughput (MT) : Allocates resources to the user with the best instantaneous channel conditions, maximizing cell capacity at the cost of fairness.
• Proportional Fair (PF) : Balances throughput maximization with fairness by scheduling users based on the ratio of instantaneous rate to average historical throughput.
• Delay-Sensitive Scheduling: Prioritizes packets with imminent latency deadlines, critical for Ultra-Reliable Low-Latency Communication (URLLC) slices.

A suite of techniques designed to mitigate the destructive effect of overlapping signals in dense cellular deployments, particularly at cell edges.

• Inter-Cell Interference Coordination (ICIC) : Coordinates resource block allocation between neighboring cells in the frequency domain to avoid collisions.
• Enhanced ICIC (eICIC) : Introduces Almost Blank Subframes (ABS) in the time domain, allowing victim cells to schedule users during protected intervals.
• Coordinated Multi-Point (CoMP) : Enables multiple transmission/reception points to dynamically coordinate to either jointly process signals or avoid interference through coordinated scheduling.

The process of distributing traffic load unevenly across network cells to prevent congestion and improve overall resource utilization. This is achieved by adjusting handover parameters or cell selection offsets.

• Mobility Load Balancing (MLB) : Automatically shifts cell boundaries by tuning handover hysteresis and time-to-trigger parameters to offload congested cells.
• Cell Range Expansion (CRE) : Adds a positive bias to the Reference Signal Received Power (RSRP) of small cells to attract more users from the macro layer.
• Predictive Load Balancing: Uses time-series forecasting to proactively shift traffic before congestion occurs, preventing Quality of Service degradation.

The use of predictive algorithms to determine the optimal timing and target cell for transferring an ongoing user connection. The objective is to minimize Radio Link Failures (RLF) and ping-pong effects.

• A3 Event: The standard measurement report triggered when a neighbor cell's RSRP exceeds the serving cell's RSRP by a defined offset.
• Time-to-Trigger (TTT) : A configurable window that validates the handover condition before execution to prevent unnecessary handovers due to fleeting signal peaks.
• Mobility Robustness Optimization (MRO) : A Self-Organizing Network (SON) function that auto-tunes handover parameters by analyzing historical RLF and handover failure logs.