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Need clarification for the sub carrier spacing of 15KHz and 3.75KHz in NB-IoT mode

Paresh Patel

Regarding nRF9160 modem 

Average current consumption, radio resource control (RRC) mode, Cat-NB1 : page no 67 in nRF9160 product specification v2.1

Both sub carrier frequencies(15 kHz and 3.75 kHz) have different average current consumption, These two sub carrier frequencies are user  configurable or it is automatically configure according to the availability of network ? please confirm.

Thanks,

Paresh Patel

  • 0

    Hello Paresh,

    I will ask our experts about that and get back to you.

    Best regards,

    Michal

  • 0

    Hello again,

    Here is the information that I got:

    Subcarrier spacing is determined by the network. Current consumption differs as the uplink transmission time and available data rate depend on subcarrier configuration. Here are a couple of helpful links/references:

    https://cdn.rohde-schwarz.com/pws/dl_downloads/dl_application/application_notes/1ma266/1MA266_0e_NB_IoT.pdf

    3.3.1 Slot Structure

    In the UL, Single Carrier Frequency Division Multiple Access (SC-FDMA) is applied, either with a 3.75 kHz or 15 kHz subcarrier spacing. eNB decides which one to use

    3GPP TS 36.201 V13.3.0 (2017-03)

    4.2.1 Multiple access

    For Narrowband Internet of Things (NB-IoT) operation, a UE operates […] in the uplink using a single sub-carrier with a sub-carrier bandwidth of either 3.75kHz or 15kHz or alternatively 3, 6 or 12 sub-carriers with a sub-carrier bandwidth of 15kHz.

    3GPP TS 36.211 V13.13.0 (2019-12)

    10.1.2.3 Resource unit

    3GPP TS 36.213 V13.16.0 (2020-03)

    16.5.1.1 Resource allocation

    The subcarrier spacing [Delta-f] of NPUSCH transmission is determined by the uplink subcarrier spacing field in the Narrowband Random Access Response Grant according to subclause 16.3.3.

    16.3.3    Narrowband random access response grant

    The higher layers indicate the Nr-bit UL Grant to the physical layer, as defined in 3GPP TS 36.321 [8].
    This is referred to as the Narrowband Random Access Response Grant in the physical layer.

    Best regards,

    Michal

  • 0 in reply to Michal

    Hi Michal,

    Thanks for your detailed answer.

    We have a query:  If eNB decides which one sub carrier (15 KHz or 3.75 KHz) to use in NB-IoT operation, how eNB decides which sub carrier bandwidth can be used? 

    If it is depending on some specific conditions, then could you know us such responsible conditions. 

    Thanks,

    Paresh Patel

  • 0 in reply to Paresh Patel

    The exact details may be dependent on the infrastructure provider, but here is some general information. Capabilities implemented by different network vendors and specific deployments done by various operators may differ.

    Source: Matthieu Kanj, Vincent Savaux, Mathieu Le Guen. A Tutorial on NB-IoT Physical Layer Design. https://hal.science/hal-02952155/document

    Best regards,

    Michal

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