IEEE Consumer Electronics Magazine - November/December 2020 - 50

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Figure 1. Some IoT use cases achieved by LTE IoT
enhancements.

downlink (DL) data rate. From the mobility point
of view, there are many IoT use cases with fixed
(stationary) or limited mobility. On the other
hand, many other IoT devices are mobile and
move between cells (see Figure 1). For instance, a
wearable medical device experiences the same
mobility as the person who wears it. Many IoT
applications take advantage of the extended cellular network coverage, particularly in remote
areas with limited signal coverage.
In order to use the existing cellular technologies to connect massive IoT nodes to the Internet with their diverse requirements, many
changes must come to legacy technologies to
accommodate new requirements. For instance,
the existing cellular technology needs to optimize the signaling of small data transmission in
order to increase the cell/network capacity to
serve very large number of devices. Furthermore, the existing legacy cellular technology
may need to use repetitive transmissions to
increase the coverage. On the other hand, the
core network may be optimized for IoT traffic to
use resources more efficiently. There must be
significant attention in bringing the complexity
of IoT devices down by decreasing the computation and power consumption such as using lower
order modulations and introducing deep sleep
modes for the IoT device.
In this article, we provide an overview of
3GPP Release 13 and the enhancements made in
Releases 14 and 15 in order to expand the LTE

IoT technology which paves the way towards fulfilling the 5G requirements specified in 3GPP
Release 15 (i.e., 5G Phase 1). The architecture of
5G consists of the core and the next generation
radio access network which itself has two parts
including New Radio (NR), and an enhanced version of LTE Release 15 which connects to the
core.1 LTE IoT addresses the massive IoT with
in-band 5G NR deployment in Release 16 (5G
Phase 2) with three main enhancements including 1) nonorthogonal access to increase the density and efficiency of the network, 2) grant-free
UL to enable mission critical communication,
and 3) multihop mesh to support low-power
devices with challenging placements.2
Furthermore, we provide a discussion on
applicability of the cellular IoT technologies for
some application scenarios including a wearable
IoT sensor, mobile robot, high speed train,
and remote firmware upgrade for car owners.
Throughout these use cases, we explain how to
determine the right technology to address the
requirements for each scenario.

LTE IOT EVOLUTION

Two cellular technologies (LTE-M and NBIoT) are standardized in 3GPP Release 13 to optimize the LTE cellular network for providing services to IoT devices. Further enhancements to
meet the requirements of massive IoT are foreseen by a rich roadmap of LTE IoT technology
inventions in 3GPP Releases 14 and 15. Hereunder, we explain LTE IoT evolution in terms of different parameters without going to detailed
signaling to aim at a more general audience interested in this topic.

Spectrum and Duplexing
In general, LTE supports scalable carrier
bandwidths from 1.4 to 20 MHz. LTE-IoT uses
part of the existing bandwidth for IoT data transfer. Initially in Release 13, the device bandwidth
for LTE-M is limited to 1.4 MHz, while NB-IoT further reduces the device bandwidth to 200 kHz.
While the NB-IoT bandwidth did not change
in the later releases, the LTE-M bandwidth is
improved to support maximum data channel
bandwidths of 5 or 20 MHz for mode A and mode
B in DL, respectively. LTE-M supports two

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IEEE Consumer Electronics Magazine - November/December 2020

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