Dear All,
We are running the LTE base station software on TI board, utilizing the BCP coprocessor and other coprocessor for resource consuming operations. Does anyone have an idea regarding the NB-IoT support of the BCP coprocessor? I have some concerns due to the differences between LTE and NB-IoT. Could you please clarify the following issues for us?
First of all BCP takes the input radio standard in the global header. It seems to me that the LTE and NB-IoT are compatible since the radio standard determines the following:
- Tailbiting activation of convolutional encoder (used both in LTE PBCH and NB-IoT DL)
- Convolutional coder input/output format (LTE and NB-IoT use the same encoder)
- Modulation (NB-IoT modulation types is a subset of LTE modulation types)
Second issue is the scrambling sequences for CRC and the TB. Since these sequences are given in the related headers, this part shall be fine too.
- CRC header: CRC header length = 4, MOD_ ID = CRC, lte_ order = 1, dtx_ format = 0, num_ scramble_ sys = 0x 0000 (no scrambler), blk_ len = 14688 (bits), CRC = crc24a
- encoder header: encoder header length = 3, MOD_ ID = encoder, turbo_conv_ sel = turbo code, scrambler crc_ select = 1 (generate CRC), block_size_ 1 = 4928 (bits), num_code_blks_ 1 = 3 (CBs), intvpar0 = <LTE interleaver parameter 0>, intvpar1 = <LTE interleaver parameter 1>
Final and the most important issue is the soft combining support of BCP coprocessor. The standard defines NB-IoT Uplink to support both HARQ with two redundancy versions, and repetitions. This would require providing N1 repetitions (1 to 2048) with the same redundancy version, and then provide another N2 repetitions, probably higher than the first transmission, (1 to 2048) with another redundancy version. I am not sure if the BCP has ever been used like this in an LTE or WiMAX scenario.
