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LTE-BL/CE (LTE-M1) - PDSCH Subframe Assignment


In LTE-M1, PDSCH can be transmitted repeatedly to increase cell coverage. Because only 1.4 Mhz (6RB) can be used and MPDCCH  takes up user data area of the subframe (similar to EPDCCH), MPDCCH and PDSCH is not transmitted in the same subframe. So subframe allocation of PDSCH becomes pretty complicated comparing to legacy LTE case. This process is defined in 36.213-7.1.11 PDSCH subframe assignment for BL/CE UE using MPDCCH and can be illustrated as follows :



The three tables defining N values are defined as follows.


< 36.213-Table 7.1.11-1: PDSCH repetition levels (DCI Format 6-1A) >


< 36.213-36.213-Table 7.1.11-2: PDSCH repetition levels (DCI Format 6-1B) >


< 36.213-36.213-Table 7.1.11-3: PDSCH repetition levels (DCI Format 6-2) >


The importantant thing to be noticed is that there are big difference between CEmodeA and CEmodeB in terms of max Number Repetition.  In General, CE Mode B perform much more repetition. The max number of repetition is configured by higher layer signaling (RRC Connection Setup or RRC Connection Reconfiguration via following IEs(information elements)as follows.


PDSCH-ConfigCommon-v1310 ::=    SEQUENCE {

    pdsch-maxNumRepetitionCEmodeA-r13   ENUMERATED { r16, r32 }     

    pdsch-maxNumRepetitionCEmodeB-r13   ENUMERATED { r192,r256,r384,r512,r768,r1024,r1536,r2048}   






[1] 3GPP TS 36.213 V13.2.0 (2016-06) Physical layer procedures