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Article
Understanding LTE Cat M1 (eMTC)
by
Samir Amberkar
(published on 8-Feb-2021)
Abstract:
In 3GPP Release 13, LTE was enhanced to satisfy requirements same as that for GSM/GPRS based IoT devices.
3GPP called it eMTC, its industry name is Cat M1.
The article explain enhancements - mainly PHY/MAC/RRC - done to support these requirements.
The article is most useful for UE/Modem and eNB developers.
Reader is expected to have basic knowledge of LTE RAN procedures and physical/logical channels.
Refer [6] , [7] , or [11] for quick brush up of these topics.
There are multitude of devices that are already connected or could be connected wirelessly soon.
These come under the gamut of "IoT devices":
Industrial equipment’s/devices/sensors (M2M),
devices from fields like Surveillance, Power transmission, Traffic control, Railways,
Ambient screens (used for various purposes like advertisements, public announcements etc.),
Medical/Healthcare monitoring devices, Consumer appliances (aka Smart appliances) like refrigerator and so on.
LTE being ubiquitous, it was an obvious forward step to provide LTE access for these devices to connect to IP network or Internet in general.
In the article, the word MTC device is used interchangeably with IoT device.
Prior to Rel 12/13, 3GPP supported M2M/IoT devices via GSM/GPRS access.
Studies were triggered to check feasibility of having MTC devices on LTE access.
Requirements were same or similar to that for GSM/GPRS based IoT devices -
low cost, limited mobility, low power consumption, low data speeds (kpbs till mbps),
and same carrier (in band operation i.e. operating along with normal LTE UEs).
Studies suggested specification enhancements on below points or areas [1] :
- Coverage improvement (indoor and deep indoor)
- Reduced bandwidth
- Half Duplex FDD operation
- Transport Block Size reduction
- Separate UE category
- Reduction in power consumption (both connected and idle modes)
Below are some of the important eMTC enhancements done in 3GPP Release 13 [2]
under the title of "Further LTE Physical Layer Enhancements for MTC".
- Category 0 UE, with CE Mode A and CE Mode B
- Reduced bandwidth of 1.4 MHz
- Support for Half Duplex FDD operation
- Maximum Transport Block Size of 1000 bits
- Separate SIBs and their scheduling for Category 0 UEs
- EPDCCH based cross-subframe scheduling
- Repetition techniques for PHY channels (UL, DL, Common, and Dedicated)
Release 13 also cover other MTC enhancements - NB-IoT and EC-GSM-IoT.
Refer 3GPP page [3] for the details.
Comparision of eMTC with above enhancements can be found here.
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