4G/LTE - BL/CE

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 (SIB2)as follows.

PDSCH-ConfigCommon-v1310 ::=    SEQUENCE {

    pdsch-maxNumRepetitionCEmodeA-r13   ENUMERATED { r16, r32 }     

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

}

Example >

sib2

    radioResourceConfigCommon

        bcch-Config

        pcch-Config

        prach-Config

        pdsch-ConfigCommon

        pusch-ConfigCommon

        pucch-ConfigCommon

        soundingRS-UL-ConfigCommon: release (0)

        uplinkPowerControlCommon

        ul-CyclicPrefixLength: len1 (0)

        bcch-Config-v1310

            modificationPeriodCoeff-v1310: n64 (0)

        pcch-Config-v1310

            paging-narrowBands-r13: 1

            mpdcch-NumRepetition-Paging-r13: r1 (0)

            nB-v1310: one64thT (0)

        freqHoppingParameters-r13

        pdsch-ConfigCommon-v1310

            pdsch-maxNumRepetitionCEmodeA-r13: r16 (0)

            pdsch-maxNumRepetitionCEmodeB-r13: r192 (0)

        pusch-ConfigCommon-v1310

            pusch-maxNumRepetitionCEmodeA-r13: r8 (0)

            pusch-maxNumRepetitionCEmodeB-r13: r192 (0)

            pusch-HoppingOffset-v1310: 1

        prach-ConfigCommon-v1310

        pucch-ConfigCommon-v1310

            n1PUCCH-AN-InfoList-r13: 1 item

                Item 0

                    N1PUCCH-AN-InfoList-r13 item: 57

            pucch-NumRepetitionCE-Msg4-Level0-r13: n1 (0)

            pucch-NumRepetitionCE-Msg4-Level1-r13: n1 (0)

    ue-TimersAndConstants

    freqInfo

        additionalSpectrumEmission: 1

    timeAlignmentTimerCommon: infinity (7)

Reference

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

[2]