【Internet of Things Communication Technology】—— LTE-M (eMTC)

Overview

eMTC (enhanced Machine-Type Communication), also known as LTE-M (Long Term Evolution-Machine-to-Machine), is essentially LTE technology for communication between machines. LTE-M is a Low Power Wide Area (LPWA) wireless interface technology that supports connecting IoT and M2M devices with moderate data rate requirements. Compared to standard cellular communication technologies like 2G, 3G, or higher-level LTE, this technology enables longer battery life and broader in-building coverage.

History

The Emergence of LTE Technology

LTE technology was formulated by the 3GPP (The 3rd Generation Partnership Project) as the long-term evolution of the UMTS (Universal Mobile Telecommunications System) technical standards. It was officially approved and launched at the 3GPP Toronto meeting in December 2004. It is developed by the same organization responsible for NB-IoT.

The technical goals of LTE can be summarized as:

• Capacity Enhancement: Achieve downlink peak data rates of 100 Mbit/s and uplink peak data rates of 50 Mbit/s within a 20MHz bandwidth. Spectrum efficiency should be 2-4 times that of the values planned in 3GPP R6.
• Coverage Enhancement: Improve "cell-edge bit rate," achieve optimal capacity within a 5km area, experience slight degradation within a 30km area, and support a coverage radius of up to 100km.
• Improved Mobility: Optimal performance at 0–15 km/h, high performance at 15–120 km/h, support for 120–350 km/h, and even support for 500 km/h in certain frequency bands.
• Quality Optimization: Reduce RAN user plane latency to less than 10ms and control plane latency to less than 100ms.
• Diversified Service Content: Provide high-performance broadcast services (MBMS), improve support for real-time services, and enable VoIP performance comparable to UTRAN circuit-switched performance.
• Reduced Operational Costs: Adopt a flat architecture to lower CAPEX and OPEX, and reduce the cost of evolving from the R6 UTRA air interface and network architecture.

Definition of LTE Cat

"Cat" stands for Category. LTE Cat is short for LTE UE-Category. Breaking it down: LTE refers to the 4G LTE network, UE refers to User Equipment, and Category translates to level. In simpler terms, it refers to the level of 4G LTE network transmission rates that user equipment can support, or it can be considered a technical standard for 4G network speed.

Note:

• The maximum data rates shown apply to a 20 MHz channel bandwidth. Categories 6 and above include data rates using carrier aggregation to combine multiple 20 MHz channels. If less bandwidth is used, the maximum data rate will be lower.
• These are L1 transport data rates and do not include overhead from different protocol layers. Actual data rates will vary depending on cell bandwidth, cell load, network configuration, the performance of the UE used, propagation conditions, etc.
• The 3.0 Gbit/s / 1.5 Gbit/s data rate specified for Category 8 is close to the peak aggregated data rate for a base station sector. A more practical maximum data rate for a single user is 1.2 Gbit/s (downlink) and 600 Mbit/s (uplink). One vendor has demonstrated a downlink speed of 1.4 Gbit/s using 100 MHz of aggregated spectrum.

Evolution of LTE-M

LTE-M (eMTC) was initially introduced in the 3GPP Release 13 standard as LTE Cat M1, which also defined Narrowband IoT (NB‑IoT or LTE Cat NB1, both LPWA technologies in licensed spectrum). 3GPP Release 14 standardized LTE Cat M2. LTE Cat M1 transmits data with a bandwidth of 1.4 MHz, while LTE Cat M2 increases this to 5 MHz. The standard brings improvements in several areas:

• Data Transfer Rates: LTE Cat M1 can support uplink and downlink speeds of 375 kb/s in half-duplex mode, making it ideal for many IoT applications with low to moderate data rate requirements. LTE Cat M2 will increase data throughput to a peak download rate of 2.4 Mb/s and a peak upload rate of 2.6 Mb/s, broadening LTE-M's appeal even for applications with relatively high data rates like video surveillance.
• Mobility: Compared to NB‑IoT, LTE-M is ideal for mobile use cases because it handles handovers between base stations just like high-speed LTE. For example, if a vehicle travels from point A to point B, crossing multiple different network cells, an LTE-M device will behave like a cellular phone and never lose connection. In contrast, an NB‑IoT device must re-establish a new connection at some point after arriving at a new cell. Now, compared to the mobility features already supported in Release 13 LTE-M, Release 14 LTE-M offers several advantages, including low power consumption and full mobility (intra-frequency and inter-frequency) suitable for mobile applications.

Technical Characteristics

Compared to NB-IoT technology, LTE-M has several advantages:

1. Higher Data Rates: Can support peak rates of up to 1 Mb/s uplink and downlink, ensuring coverage and low power consumption, suitable for low-speed video and voice applications.
2. Stronger Mobility: NB‑IoT has poor mobility and does not support handover, making it suitable for generally stationary fields like water meters, electricity meters, streetlights, etc. LTE-M, however, can be used for vehicles or wearable devices like smartwatches.
3. Positioning Capability: TDD (Time Division Duplex) based LTE-M can utilize base stations for PRS (positioning reference signal) measurements, enabling positioning without GPS signals.
4. Voice Support: Supports VoLTE, making it suitable for IoT applications related to emergency calls.
5. Supports LTE Network Reuse: Can be directly upgraded and deployed based on existing LTE networks, sharing antennas with existing LTE base stations to reduce costs.

Compared to NB-IoT technology, LTE-M is at a disadvantage in terms of coverage and cost. Therefore, NB-IoT is preferred when extensive coverage is required. For scenarios where cost is less critical, mobility is needed, and slightly larger amounts of data need to be transmitted, LTE-M is used.

Main Application Areas

• Automotive and Transportation: LTE-M supports full handover between network cells on moving vehicles, making it suitable for mobile use cases with moderate data rate requirements, including vehicle tracking, asset tracking, connected vehicles, fleet management, and usage-based insurance.
• Smart Metering: LTE-M is also ideal for monitoring meters and utility applications involving regular, small amounts of data transmission. Network coverage is a key challenge in deploying smart meters. As meters are often located inside buildings or basements, LTE-M's broader coverage provides better performance in harsh environments.
• Smart Buildings: With enhanced indoor coverage, LTE-M can easily provide basic building management functions, including HVAC, lighting, and access control. Because it supports VoLTE voice functionality, LTE-M is also ideal for critical applications like security systems and alarm panels.
• Connected Healthcare Devices: Due to its broader in-building coverage, voice support, and mobility, LTE-M is an ideal wireless interface choice for connected healthcare device applications such as outpatient monitoring and indwelling solutions.
• Smart Cities: In smart cities, LTE-M can meet various needs, efficiently controlling street lighting within milliseconds, determining when trash bins need emptying, identifying available parking spaces, monitoring environmental conditions, and investigating road conditions.

LTE-M Suppliers

• Telit
• u-blox
• Laird
• AT&T
• Cavli Wireless
• Cheerzing
• H3C
• Fibocom
• Huawei HiSilicon
• KDDI
• LinkLabs
• Longsung
• Meig
• Mobiletek
• Multitech
• MuRata
• Neoway
• NimbeLink
• Nordic Semiconductor
• pycom
• Quectel
• SERCOMM