CHAPTER 4
LTE-M Coverage Enhancement Mode A & B
The LTE-M specification has defined two Coverage Enhancement Modes: Mode A & Mode B.
The main difference is that Coverage Enhancement Mode A supports only moderate coverage enhancements whereas Mode B supports very deep coverage. Coverage Enhancement Mode A is a mandatory feature for CAT-M1 whereas Coverage Enhancement Mode B is an optional feature. This paper analyses the coverage performance for Mode B.
Fact
To support the different levels of coverage, Mode A and B support different maximum numbers of repetitions.
To support the different levels of coverage, Mode A and B support different maximum number of repetitions.
Table 5 (below) shows those maximums [4, 5]:
Another difference is that there are some functions/features which are only supported in Mode A such as connected mode mobility, 8 hybrid automatic repeat request (HARQ) processes, and several transmission modes (TMs). The Coverage Enhancement Mode only applies when the UE is in the Radio Resource Control (RRC) connected state. Mainly based on UEs’ periodically reported signal quality, the eNB decides which coverage enhancement mode the UE should be in. In general, the eNB keeps the UE in Coverage Enhancement Mode A unless the UE is in very poor coverage.
Quiz
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Coverage Techniques
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