4.75G

LTE-Advanced Pro

LTE-Advanced Pro (4.75G)

Rel-13 (2016)Rel-14 (2017)

LTE-Advanced Pro - 4.75G / Pre-5G

LTE-Advanced Pro (also called 4.5G Pro or Pre-5G) bridges LTE-A and 5G NR. Standardized in Rel-13 (2016) and Rel-14 (2017), it introduces IoT optimizations, unlicensed spectrum, and V2X.

Key Features

Major innovations in LTE-Advanced Pro:

  • LAA/eLAA - LTE in unlicensed 5 GHz spectrum
  • NB-IoT - Narrowband IoT for sensors
  • LTE-M (eMTC) - Enhanced Machine Type Communication
  • V2X - Vehicle-to-Everything communication
  • Massive MIMO - FD-MIMO up to 64 ports
  • 256QAM - Higher order modulation
  • 32 CC CA - Extreme carrier aggregation

๐Ÿ“‹ Specifications: TR 36.900 (LTE-A Pro Overview)

LAA

License Assisted Access (LAA) - using unlicensed 5 GHz spectrum alongside licensed LTE. See the detailed glossary entry for evolution to eLAA.

LAA vs eLAA vs MulteFire

Feature LAA (Rel-13) eLAA (Rel-14) MulteFire
Licensed anchor Required Required Not required
Downlink Yes Yes Yes
Uplink No Yes Yes
Spectrum 5 GHz 5 GHz 5 GHz

LBT (Listen Before Talk)

Coexistence with WiFi requires LBT:

Category Max TXOP Use Case
Cat 1 No LBT Immediate TX
Cat 2 LBT no backoff Short burst
Cat 3 LBT + fixed CW Medium
Cat 4 LBT + variable CW Data (default)

LBT Process:

  1. Sense channel for CCA period (minimum 25 ฮผs)
  2. If busy, defer and retry
  3. If clear, transmit (max MCOT: 8-10 ms)

5 GHz Bands

Band Frequency Channels Region
UNII-1 5150-5250 MHz 4 Global (indoor)
UNII-2A 5250-5350 MHz 4 Global (DFS req.)
UNII-2C 5470-5725 MHz 11 EU/US (DFS req.)
UNII-3 5725-5850 MHz 5 US (outdoor OK)

๐Ÿ“‹ Specifications: TS 36.300 ยง22 (LAA), TR 36.889 (LAA Study)

NB-IoT

Narrowband IoT (NB-IoT) - ultra-low-power wide-area IoT technology. See the detailed glossary entry for evolution across releases.

Deployment Modes

Mode Description Bandwidth
In-band Within LTE carrier 1 PRB (180 kHz)
Guard-band In LTE guard band 180 kHz
Standalone Dedicated spectrum 200 kHz

Key Characteristics

Parameter Value
Bandwidth 180 kHz (single PRB)
Peak DL 26 kbps (single tone)
Peak UL 66 kbps (multi-tone)
Coverage MCL 164 dB (+20 dB vs GPRS)
Battery 10+ years
Cost <$5 module

Physical Channels

Channel Direction Purpose
NPBCH DL Broadcast (MIB-NB)
NPDCCH DL Control
NPDSCH DL Shared data
NPUSCH UL Shared data
NPRACH UL Random access

Power Saving Features

  • PSM: Power Saving Mode (up to 413 days TAU)
  • eDRX: Extended DRX (up to 3 hours)
  • Coverage enhancement: Up to 2048 repetitions

Rel-14 Enhancements (NB-IoT v2)

  • Multicast (DL group messaging)
  • Positioning (OTDOA)
  • New UE categories (Cat NB2)
  • Mobility improvements

๐Ÿ“‹ Specifications: TS 36.211 ยง10 (NB-IoT), TS 36.331 (RRC)

LTE-M

LTE-M (eMTC - enhanced Machine Type Communication) - IoT optimized LTE. See the detailed glossary entry for comparison with NB-IoT and evolution.

Comparison: LTE-M vs NB-IoT

Feature LTE-M (Cat M1) NB-IoT (Cat NB1)
Bandwidth 1.4 MHz 180 kHz
Peak DL 1 Mbps 26 kbps
Peak UL 1 Mbps 66 kbps
Latency ~10 ms ~1.6-10 s
Mobility Full handover Cell reselection
VoLTE Yes No
Coverage MCL 156 dB MCL 164 dB

Use Cases

Technology Best For
LTE-M Wearables, trackers, VoLTE, medium throughput
NB-IoT Sensors, meters, static devices, extreme battery

LTE-M Features

  • VoLTE support (HD voice capable)
  • Full mobility (handover between cells)
  • Half-duplex FDD (cost reduction)
  • Coverage enhancement (repetitions)
  • PSM + eDRX (power saving)

Rel-14 Enhancements (Cat M2)

Feature Cat M1 Cat M2
Peak DL 1 Mbps 4 Mbps
Peak UL 1 Mbps 7 Mbps
HARQ 2 10
VoLTE Yes Yes

๐Ÿ“‹ Specifications: TS 36.306 (UE Categories), TR 36.888 (MTC Study)

V2X

Vehicle-to-Everything (V2X) communication for automotive safety and efficiency. See the detailed glossary entry for evolution to NR V2X.

V2X Components

Type Description Use Case
V2V Vehicle-to-Vehicle Collision avoidance
V2I Vehicle-to-Infrastructure Traffic signals, tolls
V2P Vehicle-to-Pedestrian Safety alerts
V2N Vehicle-to-Network Cloud services

LTE V2X (C-V2X) - Rel-14

Two communication modes:

Mode Interface Use Case
Device-to-Device PC5 (sidelink) V2V, V2I direct
Device-to-Network Uu (cellular) V2N cloud
Feature Value
Latency <20 ms
Range >400 m (NLOS)
Reliability >90% (NLOS)
Spectrum ITS band (5.9 GHz)

Resource Allocation Modes

Mode Description Scenario
Mode 3 Network scheduled In coverage
Mode 4 Autonomous Out of coverage

Safety Messages

Message Purpose Rate
BSM/CAM Basic Safety 10 Hz
DENM Hazard warning Event-triggered

๐Ÿ“‹ Specifications: TS 23.285 (V2X Architecture), TS 36.300 ยง23 (V2X)

Massive MIMO / FD-MIMO

Full Dimension MIMO - exploiting both horizontal and vertical dimensions.

Evolution

Release Max Ports Antennas Capability
Rel-8 4 4 Basic MIMO
Rel-10 8 8 Enhanced MIMO
Rel-13 16 16-64 FD-MIMO
Rel-14 32 64-128 eFD-MIMO

FD-MIMO Benefits

  • 3D Beamforming: Vertical + horizontal beam steering
  • Higher MU-MIMO: More simultaneous users
  • Better coverage: Focused beams
  • Higher capacity: Spatial multiplexing

Antenna Array

Typical configuration: 8ร—8 cross-polarized = 64 antenna elements

[x x x x x x x x]
[x x x x x x x x]
[x x x x x x x x]
[x x x x x x x x]   โ†’ 64 elements
[x x x x x x x x]      32 ports (dual-pol)
[x x x x x x x x]
[x x x x x x x x]
[x x x x x x x x]

๐Ÿ“‹ Specifications: TS 36.211 (Physical Channels), TR 36.897 (FD-MIMO Study)

256QAM

Higher order modulation for increased spectral efficiency.

Modulation Comparison

Modulation Bits/Symbol Efficiency SINR Required
QPSK 2 2 bps/Hz Low
16QAM 4 4 bps/Hz Medium
64QAM 6 6 bps/Hz High
256QAM 8 8 bps/Hz Very High

Introduction

Direction Release Gain
Downlink Rel-12 +33% peak rate
Uplink Rel-14 +33% peak rate

Requirements

  • High SINR (>25 dB typically)
  • Low interference
  • Good channel estimation
  • Best for: Cell center, small cells, stationary UEs

๐Ÿ“‹ Specifications: TS 36.211, TS 36.212

LTE-WiFi Aggregation

Combining LTE and WiFi at the RAN level.

LWA vs LWIP

Feature LWA (Rel-13) LWIP (Rel-13)
Integration level RAN RAN
WiFi termination At eNB/WT At WT
Security LTE PDCP IPsec tunnel
Deployment Tight coupling Loose coupling

LWA Architecture

                 โ”Œโ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”
                 โ”‚  EPC   โ”‚
                 โ””โ”€โ”€โ”€โ”ฌโ”€โ”€โ”€โ”€โ”˜
                     โ”‚ S1
                โ”Œโ”€โ”€โ”€โ”€โ”ดโ”€โ”€โ”€โ”€โ”
                โ”‚  eNB    โ”‚
                โ””โ”€โ”€โ”€โ”€โ”ฌโ”€โ”€โ”€โ”€โ”˜
            Xw      โ”‚      Uu
         โ”Œโ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”ผโ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”
    โ”Œโ”€โ”€โ”€โ”€โ”ดโ”€โ”€โ”€โ”€โ”          โ”Œโ”€โ”€โ”€โ”€โ”€โ”ดโ”€โ”€โ”€โ”€โ”€โ”
    โ”‚   WT    โ”‚          โ”‚    UE     โ”‚
    โ”‚ (WiFi)  โ”‚โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”‚           โ”‚
    โ””โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”˜   WiFi   โ””โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”˜

Benefits

  • Increased throughput: Aggregate both
  • Better indoor: WiFi for indoor offload
  • Seamless mobility: Network controlled steering

๐Ÿ“‹ Specifications: TS 36.300 ยง24 (LWA), TR 36.875 (LWA Study)

UE Categories

Rel-13 Categories

Category Max DL Max UL Features
Cat 15 750 Mbps 226 Mbps 4CC CA, 256QAM
Cat 16 1 Gbps 150 Mbps 5CC CA, 4ร—4 MIMO
Cat M1 1 Mbps 1 Mbps eMTC/LTE-M
Cat NB1 26 kbps 66 kbps NB-IoT

Rel-14 Categories

Category Max DL Max UL Features
Cat 17 1.5 Gbps 226 Mbps 32CC LAA
Cat 18 1.2 Gbps 211 Mbps 6CC CA
Cat 19 1.6 Gbps 75 Mbps 8CC CA
Cat 20 2 Gbps 316 Mbps 8CC, 256QAM UL
Cat M2 4 Mbps 7 Mbps Enhanced eMTC
Cat NB2 127 kbps 159 kbps Enhanced NB-IoT

๐Ÿ“‹ Specifications: TS 36.306 (UE Radio Access Capabilities)

Timeline

  • 2015 - Rel-13 work started
  • 2016 - Rel-13 frozen (LAA, NB-IoT, LTE-M)
  • 2016 - First NB-IoT deployments
  • 2017 - Rel-14 frozen (V2X, eLAA)
  • 2017 - LTE-M commercial launches
  • 2018 - V2X trials and deployments