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LTE-BL/CE (LTE-M1)

 

BL stands for Bandwidth reduced Low complexity and CE stands for Coverage Enhancement. In release 13, you would see many statements about BL UE/CE UE, but I took me quite a while to find out what they stands for :) (I found it in 36.300).

In many Whitepaper or articles, you might have seen the term like MTC, LTE-M1. But in formal 3GPP Technical Specification, you would noticed that these terminology (e.g, MTC, LTE-M1) is not clearly defined. In 3GPP TS, the term BL/CE is usually used to indicate the implementation of LTE-M1.

 

Followings are some of the major characteristics of LTE-M1.

  • LTE-M1 operate only in 1.4 Mhz (6 RB) bandwidth.
  • LTE-M1 would mainly operate with legacy LTE using wider system bandwidth (e.g, 10 Mhz, 20Mhz system bandwidth)
  • LTE-M1 divide the legacy LTE system bandwidth into multiple sections of 1.4 Mhz and use any one of those sections (theoretically, LTE-M1 can use different 1.4Mhz section within the system bandwidth at every subframe)
  • LTE-M1 does not use PCFICH, PHICH, PDCCH which is required to be spreaded across the whole system bandwidth of legacy LTE.
  • LTE-M1 use specially designed control channel called MPDCCH.
  • In LTE-M1, MPDCCH and the corresponding PDSCH (i.e, the PDSCH scheduled by the MPDCCH) is not in the same subframe. This is called 'Cross-subframe scheduling'.
  • LTE-M1 use specially designed DCI formats (6-0A,6-0B,6-1A,6-1B,6-2)
  • LTE-M1 can transmit MPDCCH, PDSCH, PUSCH in repeating fashion. (This is to make these channels decodable even when the signal quality/power is very poor as in the harsh condition like basement. As a result, this kind of repeating transmission would make the effect of increasing cell radius and signal penetration)

 

Followings are list of the detailed topics. I am assuming that readers already have knowledge on how legacy LTE works and I will describe these topics with focus on the differences from the legacy LTE.