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Idea behind this article is to capture top level view of the enhancements, more from RAN or Access Stratum point of view.
Though deep details are omitted, abundant number of specification section references are provided.
Release versions of the specifications referred is Release 13.
Below are some of the terms used for eMTC UE.
Category 0 UE,
Low Complexity UE (CL UE),
Bandwidth Reduced UE (BR UE),
Bandwidth Reduced Low complexity UE (BL UE),
Coverage Enhanced UE (CE UE), or
BL/CE UE
We shall continue to use the word "eMTC UE" for this category of UE for rest of the article.
Refer 36.300:23.7 [4] for top level description of Category 0 UE.
"BR" abbreviation is also used in RRC specification to indicate its applicability to eMTC,
e.g. SIB1-BR.
Irrespective of the bandwidth of the cell, eMTC UE always operate with 1.4 MHz bandwidth i.e. 6 PRBs.
6 PRBs is called one Narrowband (NB).
Cell bandwidth is divided in Narrowbands, so 5 MHz bandwidth cell will have 4 NBs.
Though UE is RF capable to do reception/transmission on all narrowbands, only one narrowband at a time (subframe).
Operation being HD-FDD, there is no simultaneous DL reception and UL transmission, and
there is a guard period between DL and UL (part of subframe or full subframe gap) - 36.211:4.1/6.2.5 [8] .
HD-FDD reduces RF complexity and helps reduce power consumption.
For bandwidths 10, 15, and 20, narrowbands overlapping with MIB are not chosen for DL transmission.
Narrowbands for all bandwidths are tabulated on next page.
Refer 36.211:6.2.7 [8] for information on Narrowbands.
eMTC UE perform synchronisation (PSS/SSS/MIB acquisition) procedure, just like normal LTE UE.
Non-zero value of "schedulingInfoSIB1-BR" parameter in MIB indicate that the cell support eMTC UEs.
"schedulingInfoSIB1-BR" value is passed to PHY - where it maps to SIB1 PDSCH repetitions.
Each SIB is never more than 1000 bits and occupy 6 PRBs.
1000 bit limit apply to all transport blocks.
In addition to information available in corresponding in LTE SIBs (e.g. SIB periodicity in SIB1, RACH configuration in SIB2),
eMTC SIBs contain eMTC specific information (e.g. SIB narrowbands in SIB1, MSG2/RAR narrowband in SIB2).
Refer 36.331 [5] for further information on MIB and various eMTC SIBs.
Needless to say, cells - not supporting eMTC - are barred for eMTC UEs.
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