Description
Extended Coverage System Information (EC SI) refers to mechanisms defined in 3GPP to improve the reliability of System Information (SI) acquisition for User Equipment (UE), particularly those operating in extended coverage conditions as required for Machine-Type Communication (MTC) and Narrowband-IoT (NB-IoT). System Information provides the UE with essential parameters needed to access and operate within a cell, including cell access parameters, neighboring cell information, and common channel configurations. Under normal conditions, SIBs are broadcast periodically on the Broadcast Channel (BCH) and Downlink Shared Channel (DL-SCH). However, for UEs in very poor signal conditions (e.g., deep indoors, basements, or at the edge of coverage), these standard transmissions may not be decodable.
EC SI works by applying coverage enhancement techniques to the transmission of specific SIBs. These techniques primarily involve time-domain repetition, where the same SIB is transmitted multiple times over consecutive subframes. The UE can then combine these repeated transmissions using soft combining at the physical layer to improve the effective Signal-to-Noise Ratio (SNR) and successfully decode the information. Additionally, for technologies like NB-IoT, more robust modulation and coding schemes (e.g., lower order modulation like BPSK) may be used for these extended coverage SIBs. The network indicates the use of EC SI through master information blocks (MIBs) or scheduling information, telling the UE which SIBs are transmitted with extended coverage and their repetition patterns.
The architecture involves modifications at the eNodeB (for LTE) or gNB (for NR) to schedule and transmit these repeated SIB blocks. The UE side requires corresponding capability to monitor for these repetitions and perform the necessary combining. The specific SIBs that can be transmitted with extended coverage are defined per technology; for example, in LTE-M, SIB1-BR (for bandwidth reduced UEs) and other critical SIBs support EC. In NB-IoT, the MIB-NB and SIB1-NB are fundamental and use repetition. The role of EC SI is critical for enabling reliable initial cell selection, camping, and reselection for IoT devices that must operate for years on a battery and often in locations with very weak signals, ensuring they can always read the necessary parameters to attach to the network.
Purpose & Motivation
EC SI was created to address a fundamental challenge in deploying large-scale IoT networks: providing reliable service to devices in extremely poor radio conditions. Traditional cellular system information broadcasting was designed for handheld devices typically used by humans in relatively good coverage areas. For IoT applications like smart meters (installed in basements), agricultural sensors (in remote fields), or tracking devices (inside containers), the path loss can be 20dB or more worse than typical cases. Without enhancement, these devices would fail to read the system information, preventing them from even accessing the network.
The motivation stemmed from the 3GPP work on Cellular IoT (CIoT) in Releases 13 and beyond, which defined LTE-M and NB-IoT. A key requirement for these technologies was to support coverage enhancement of up to 15-20 dB compared to legacy LTE. While data channel enhancements (like repetition for physical data channels) were defined, it was equally important to enhance the control channels and system information broadcasting. Without enhanced SI, a device could theoretically have an enhanced data channel but be unable to read the instructions on how to use it. EC SI solves this by ensuring the very first messages a device needs to read—the system information—are also robustly transmitted.
This solves the problem of asymmetric link budgets where the downlink (network to device) becomes the limiting factor for coverage. It ensures that the network's accessibility is not the weak link in an otherwise robust IoT connection. By guaranteeing reliable delivery of SI, EC SI enables predictable device behavior, reduces connection failures, and supports the ultra-reliable low-latency communication (URLLC) principles for critical IoT, all while maintaining the power efficiency required for massive IoT deployments.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (26 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-7, normative work from Rel-15.
In Release 15, the Extended Coverage (EC) function introduced energy efficiency enhancements specifically for EC-GSM-IoT devices in idle mode and included corrections to procedures like EC-PICH and multiplexing for EC-GSM-IoT. It also defined mechanisms for deferred system information acquisition and addressed system information handling and provisioning. Furthermore, the release enabled the exposure of network energy consumption information to customers, independent of NG-RAN deployment scenarios.
- Energy efficiency enhancements for EC-GSM-IoT MS in idle mode TS 43.064CR0117
- Deferred System Information Acquisition for PEO TS 43.064CR0120
- Slicing assistance information TS 38.300CR0024
- System Information Handling in TS38.300 TS 38.300CR0071
- Corrections to System Information TS 38.300CR0074
- Correction to the system information in Handover Request message TS 38.300CR0086
+ 5 more changes
In Release 16, the EC (Extended Coverage) function was enhanced to enable the acquisition and exposure of network Energy Consumption (EC) information to vertical customers as a new service criterion. This introduced the capability for the 5G system to gather EC data from network functions serving a customer, independent of NG-RAN deployment scenarios like dual-connectivity or Distributed Unit (DU) configurations, and expose it via value-added services such as "Green Energy Moni." This allows customers, including those in Non-Public Networks (NPN) with RAN sharing, to access energy efficiency information relevant to their specific services.
In Release 17, the new EC (Extended Coverage) function introduced NR coverage enhancements for scenarios like massive IoT, specifically to maintain communication for dense groups of UEs moving into extreme low coverage areas. This allows IoT devices to communicate with varying latency, where increased energy consumption for serving devices in poor coverage is monitored and aggregated by the network. The enhancements address energy consumption increases for communication in sparse coverage, linking extended coverage capabilities directly to energy-aware service delivery.
In Release 18, the new EC (Extended Coverage) function introduced the capability for the 5G system to acquire and expose network energy consumption information to vertical customers. This allows customers subscribed to value-added services like "Green Energy Moni" to access energy consumption data for the network functions serving them, independent of NG-RAN deployment scenarios such as dual-connectivity or distributed unit configurations. The enhancement addresses a previous gap by enabling energy efficiency information exposure, including in RAN sharing cases for Non-Public Networks.
- Introduction of Further NR coverage enhancements to 38.300 TS 38.300CR0733
- Transfer PDU Set Information during data forwarding for Xn handover TS 38.300CR0828
- Correction on UE assistance information for XR TS 38.300CR0964
- Clarification of the chapter title to match the description of the UE History Information TS 38.300CR0969
- Stage 2 correction on DL LBT failure information TS 38.300CR0971
- Correction of NTN OAM Assistance information TS 38.300CR1001
In Release 19, the "EC" (Extended Coverage) function was enhanced by introducing the capability to acquire and expose network energy consumption information to vertical customers as a value-added service. This allows customers, such as those using dual-connectivity or specific DU deployments, to access their associated network function energy data via a web application, independent of the NG-RAN deployment scenario. Furthermore, the release expanded this energy information exposure to cover use cases within Non-Public Networks (NPN) operating under RAN sharing arrangements.
Explore further
Broader topics and technologies where EC plays a role.
Defining Specifications
3GPP specifications that define or reference EC, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TR 22.882 vj30 | Study on Energy Efficiency as a Service Criteria | Rel-19 |
| TS 22.883 vk00 | Energy Efficiency as Service Criteria Phase 2 | Rel-20 |
| TR 22.967 vj00 | eCall Emergency Data Transmission | Rel-19 |
| TS 23.700 vk00 | XR Services Application Enablement Layer | Rel-20 |
| TS 24.229 vj50 | IMS call control protocol based on SIP and SDP | Rel-19 |
| TS 26.115 vj00 | 3GPP TS 26115: Echo Control Requirements | Rel-19 |
| TS 26.253 vj00 | IVAS Codec Algorithmic Description | Rel-19 |
| TR 26.967 vj00 | eCall via CTM Suitability Analysis | Rel-19 |
| TS 28.310 vj20 | Energy Efficiency Management for 5G Networks | Rel-19 |
| TS 32.303 v900 | Notification IRP CORBA Solution Set | Rel-9 |
| TS 32.306 vj00 | Configuration Management Notification IRP Solution Set | Rel-19 |
| TS 32.856 vf00 | Energy Efficiency Assessment for RAN OAM | Rel-15 |
| TS 37.890 vj10 | Feasibility Study on 6 GHz for LTE/NR | Rel-19 |
| TS 38.300 vj00 | NG-RAN Overall Description | Rel-19 |
| TR 38.852 vh50 | 1900MHz NR band for European Rail Mobile Radio | Rel-17 |
| TR 38.853 vh50 | 900MHz NR Band for European Rail Mobile Radio | Rel-17 |
| TS 43.064 vj00 | GPRS Radio Interface Lower-Layer Functions | Rel-19 |
| TS 44.060 vj00 | GERAN RLC/MAC Protocol Specification | Rel-19 |
| TS 45.004 vj00 | GSM/EDGE Modulation Specification | Rel-19 |