LTE-Advanced
LTE-Advanced
Overview
LTE-Advanced (LTE-A) is the Release 10 evolution of LTE, the first 3GPP release to formally meet the ITU's IMT-Advanced requirements for a true "4G" system. It preserves backward compatibility with Release 8/9 LTE while adding carrier aggregation, higher-order MIMO, relay nodes, and coordinated multi-point transmission to substantially raise peak and cell-edge throughput.
A Release 8 UE can operate on an LTE-Advanced carrier without seeing the enhancements, while an LTE-A capable UE can exploit aggregated carriers and advanced antenna schemes for significantly higher data rates.
Key Features
- Carrier Aggregation (CA) — combining up to 5 component carriers (Rel-10) for up to 100 MHz aggregated bandwidth
- Enhanced MIMO — up to 8x8 downlink and 4x4 uplink spatial multiplexing
- Relay nodes — layer-3 relays extending eNodeB coverage via a wireless backhaul (Un interface)
- Coordinated Multi-Point (CoMP) — joint transmission/reception across cells to improve cell-edge performance
- Heterogeneous networks (HetNet) support with enhanced Inter-Cell Interference Coordination (eICIC)
Network Architecture
LTE-Advanced reuses the flat E-UTRAN/EPC architecture from Release 8, adding new logical elements for relaying and small-cell coordination without changing the core network model.
| Component | Full Name | Function |
|---|---|---|
| Donor eNodeB (DeNB) | Donor eNodeB | Provides wireless backhaul (Un interface) to relay nodes |
| Relay Node (RN) | Relay Node | Extends coverage; appears as a normal eNodeB to UEs on the access side |
| MME / S-GW / P-GW | EPC core elements | Unchanged from Release 8 EPC — see the LTE technology page |
Physical Layer
| Parameter | Rel-8 LTE | LTE-Advanced (Rel-10+) |
|---|---|---|
| Max bandwidth (single carrier) | 20 MHz | 20 MHz per component carrier |
| Max aggregated bandwidth | n/a | Up to 100 MHz (5 x 20 MHz CCs, Rel-10) |
| Downlink MIMO | Up to 4x4 | Up to 8x8 |
| Uplink MIMO | 1x2 (SIMO typical) | Up to 4x4 SU-MIMO |
| Modulation | Up to 64-QAM | Up to 256-QAM downlink (from Rel-12) |
Frequency Bands
LTE-Advanced uses the same band plan as LTE (see the LTE technology page), with carrier aggregation defined via specific CA band combinations (e.g. CA_1A-3A, CA_3A-7A) standardized incrementally each release as operators deploy multi-band spectrum.
| CA Combination | Bands | Typical Aggregated BW |
|---|---|---|
| CA_1-3 | B1 + B3 | Up to 40 MHz |
| CA_3-7 | B3 + B7 | Up to 40 MHz |
| CA_3-7-20 | B3 + B7 + B20 | Up to 55 MHz (3CC) |
📋 Specifications:TS 36.101
UE Categories
| Category | DL Peak Rate | UL Peak Rate | Aggregated CCs |
|---|---|---|---|
| Cat 6 | 301.5 Mbps | 51 Mbps | 2 |
| Cat 9 | 452.2 Mbps | 51 Mbps | 3 |
| Cat 11 | 600.8 Mbps | 51 Mbps | 3–4 |
| Cat 16 | 979 Mbps | 150 Mbps | 4+ |
Services
- High-throughput mobile broadband exploiting aggregated spectrum
- VoLTE, inherited unchanged from the underlying LTE/IMS service layer
- Improved cell-edge and indoor coverage via relay nodes and CoMP
- eMBMS broadcast services, extended with higher-capacity carriers
Security
| Layer | Algorithm Family | Purpose |
|---|---|---|
| NAS / AS ciphering | 128-EEA1/2/3 (unchanged from LTE) | Confidentiality protection |
| NAS / AS integrity | 128-EIA1/2/3 | Integrity protection |
| Relay backhaul (Un) | AS security reused, PDCP-layer protection | Secures the wireless donor–relay backhaul link |
Key Procedures
Secondary Cell (SCell) Addition for CA
- UE reports channel measurements on candidate carriers to the serving (PCell) eNodeB
- eNodeB configures one or more SCells via RRC Reconfiguration (CA configuration)
- eNodeB activates the SCell via a MAC Control Element when data demand requires it
- UE begins scheduling on both PCell and active SCell(s), aggregating throughput
Relay Node Attach
- RN performs an initial attach to the Donor eNodeB as a Release 10 UE to obtain backhaul connectivity
- RN retrieves its RN-specific configuration from the network (OAM)
- RN establishes the Un interface and starts operating as an eNodeB toward access-side UEs
Power Saving
| Mechanism | Description |
|---|---|
| SCell DRX alignment | Secondary cells follow the PCell DRX cycle to avoid extra UE wake-ups |
| SCell deactivation timer | Inactive SCells are deactivated automatically to save UE power |
Interworking
| Aspect | LTE (Rel-8) | LTE-Advanced (Rel-10+) |
|---|---|---|
| Backward compatibility | n/a | Rel-8 UEs can camp on an LTE-A carrier using only the PCell |
| Core network impact | EPC baseline | None — CA/CoMP/relay are RAN-only enhancements |
Extensions for Later Releases
- Rel-11: CoMP standardization, enhanced PDCCH (EPDCCH) for HetNet interference mitigation.
- Rel-12: Dual connectivity (small-cell/macro), 256-QAM downlink, D2D/ProSe.
- Rel-13: Evolves into LTE-Advanced Pro with up to 32 aggregated carriers, NB-IoT, LAA.
Comparison with Previous Generations
| Aspect | LTE (Rel-8/9) | LTE-Advanced (Rel-10+) |
|---|---|---|
| Peak DL throughput | ~300 Mbps (2x2, 20 MHz) | ~1 Gbps class (CA + 8x8 MIMO) |
| IMT-Advanced compliant | No | Yes |
| Coverage extension | Macro cells only | Relay nodes + HetNet/eICIC |