Energy Saving xApp

July 30, 2026 · View on GitHub

Overview

The Energy Saving (ES) xApp is an O-RAN-compliant near-RT RIC application that automates cell switch-on/off decisions based on real-time radio resource utilization. It closes the loop between the simulated network and the RIC — observing KPM reports, making decisions, and sending RC control messages back to the gNB — entirely autonomously.

Attribute	Value
O-RAN Standard	O-RAN Use Cases Detailed Specification 15.0
Use Case	21 — Carrier and Cell Switch On/Off
Sub-use Case	4.21.3.1
Service Models Used	KPM v3.00 (reporting), RC v1.03 (control)
Scenario File	`scratch/Energy_saving_with_cell_utilization_scenario.cc`
xApp Binary	`xapp_es_with_cell_util`
FlexRIC Branch	`oie-ric-taap-xapps`

How It Works

┌─────────────────────────────────────────────────────────────────┐
│                         near-RT RIC                             │
│                                                                 │
│   KPM Indication ──► ES xApp ──► Decision ──► RC Control       │
│   (PRB utilization)              (ON / OFF)   (Cell switch)     │
└───────────▲─────────────────────────────────────────┬──────────┘
            │ E2 Interface                             │ E2 Interface
            │                                          ▼
┌───────────────────────────────────────────────────────────────┐
│                     ns-3 Simulation                           │
│                                                               │
│   gNB 1 ── gNB 2 ── gNB 3 ── gNB 4   (mmWave + LTE eNB)    │
│                   UEs                                         │
└───────────────────────────────────────────────────────────────┘

Step-by-step operation:

The ES xApp subscribes to KPM indication reports from each simulated gNB.
Each report carries the per-cell PRB utilization over the indication period.
The xApp evaluates per-cell utilization against thresholds:
- Utilization below the low threshold → cell is a candidate to switch off (deep sleep).
- A sleeping cell's neighbours show high utilization → cell is a candidate to switch back on.
The decision is sent as an RC Control message (Control Service Style 3, Action ID 1 — Handover Control) to the target gNB.
The gNB applies the cell state change and continues reporting.

The sequence diagram below illustrates the full operation:

ES xApp Operation Sequence

Demo Video

🎬 Watch the Energy Saving xApp Demonstration

Prerequisites

Before running this xApp, make sure the following are in place:

FlexRIC built from the oie-ric-taap-xapps branch (see README §9.3).
ns-O-RAN-flexric built (see README §9.4).
RIC-TaaP Studio deployed (see README §9.5).

Running with RIC-TaaP Studio (Recommended)

Energy Saving Dashboard in RIC-TaaP Studio

Step 1 — Start the near-RT RIC

cd /path/to/flexric/build/examples/ric/
./nearRT-RIC

Step 2 — Open RIC-TaaP Studio

Open your browser at http://127.0.0.1:8000.

Step 3 — Connect to FlexRIC

Click Connect to FlexRIC on the homepage to establish the RIC link.

Step 4 — Select and configure the scenario

Click Show Form.
From the scenario list, select Energy_saving_with_cell_utilization_scenario.cc.
Enable the scenario flags to use the preset configuration.
Click Start. Cells and UEs will appear on the grid within a few seconds.

Step 5 — Launch the ES xApp

cd /path/to/flexric/build/examples/xApp/c/orange/
./xapp_es_with_cell_util

Alternatively, trigger the xApp directly from the GUI:

# Copy the trigger scripts (one-time setup)
cp "/path/to/mmwave-LENA-oran/GUI/FlexRIC xApp GUI trigger/"* /path/to/flexric/
cd /path/to/flexric/
python3 xApp_trigger.py

Step 6 — Observe results

Navigate to the Energy Saving Dashboard tab in RIC-TaaP Studio to monitor:

Metric	Description
UE DL Throughput	Per-UE downlink throughput (Mbps)
Cell Energy State	Active / Deep-sleep status per cell
PRB Utilization	Percentage of PRBs in use per cell
Energy Consumption	Power consumption before and after xApp execution
QoS Impact	Effect of cell switch-off on user QoS

Step 7 — Stop the simulation

Click Stop in the Show Form window.

Running from Terminal

Open three separate terminals:

# Terminal 1 — near-RT RIC
cd /path/to/flexric/build/examples/ric/
./nearRT-RIC

# Terminal 2 — ns-3 simulation
cd /path/to/mmwave-LENA-oran
./ns3 run scratch/Energy_saving_with_cell_utilization_scenario.cc

# Terminal 3 — ES xApp
cd /path/to/flexric/build/examples/xApp/c/orange/
./xapp_es_with_cell_util

Key Run Flags

Flag	Type	Default	Description
`--e2TermIp`	string	`127.0.0.1`	IP address of the near-RT RIC
`--KPM_E2functionID`	double	`2`	RAN function ID for KPM service model
`--RC_E2functionID`	double	`3`	RAN function ID for RC service model
`--indicationPeriodicity`	double	`0.1`	KPM reporting interval (seconds)
`--simTime`	double	`1000`	Total simulation duration (seconds)
`--N_MmWaveEnbNodes`	uint8	`4`	Number of mmWave gNBs
`--N_Ues`	uint32	`3`	Number of UEs
`--IntersideDistanceCells`	double	`600`	Inter-site distance between cells (metres)