LTE NB-IoT NPUSCH Function, LTE NB NPUSCH Format-1, NPUSCH Format-2
This page describes LTE NB-IoT NPUSCH function with location and its basics with respect to LTE-NB IoT Standard. It covers NB-IoT NPUSCH formats and mentions difference between NPUSCH format-1 and NPUSCH format-2.
NPUSCH channel is used to transport uplink user data and control information from upper layers. Moreover NPUSCH carry HARQ Ack for NPDSCH. NB-IoT uses only one PRB as maximum device scheduled bandwidth.
|RU||1, 2, 4, 8, 32 ms|
|Repetitions||1, 2, 4, 8, 16, 32, 64, 128|
|Subcarrier spacing||3.75 KHz, 15 KHz|
|Bandwidth||3.75, 15, 45, 90, 180 KHz|
Table-1 mentions useful parameters related to NB-IoT NPUSCH channel.
Difference between NB-IoT NPUSCH Format-1 and Format-2
NPUSCH supports two transmission formats depending on data it carries viz. format-1 and format-2. Let us understand difference between NPUSCH format-1 and NPUSCH format-2.
• This format-1 is used for carrying uplink data and uses same LTE turbo code for error correction.
• It supports UE bandwidth allocation smaller than one PRB where as LTE has min. bandwidth allocation of 1 PRB.
• Maximum transport block (TB) size is 1000 bits.
• It supports multi-tone transmission based on LTE numerology. Here NB-IoT UE is allocated with 3 and 6 tone formats.
• It also supports single tone transmission based on either 3.75 KHz or 15 KHz numerology. LTE uses only 15 KHz.
• It uses π/2 - BPSK or π/4 - QPSK for single tone transmission to reduce PAPR.
• It supports single layer transmission where as LTE supports multiple spatial multiplexing layers.
• It uses same slot structure as legacy PUSCH with 7 OFDM symbols per slot ( as shown in the figure-1) and middle symbol as DMRS used for channel estimation.
• It is used for signaling HARQ Ack for NPDSCH.
• It uses repetition code for error correction.
• NPUSCH format-2 has 7 OFDM symbols per slot as shown in the figure-2.
• It supports 3.75 KHz or 15 KHz numerology.
• It uses middle three symbols as DMRS used for channel estimation.
• It uses single tone transmission.
Reference: 3GPP 36 series
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