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what's the differece of NB-IoT and EMTC part 3?

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what's the differece of NB-IoT and EMTC part 3?

NB-IoT downlink is consistent with LTE, adopts orthogonal frequency division multiple access (OFDMA) technology, subcarrier spacing is 15 kHz, time slot, subframe and radio frame length are 0.5 ms, 1 ms and 10 ms, respectively, including OFDM symbols per slot. The number and cyclic prefix are the same as LTE.
The carrier bandwidth of the NB-IoT is 180KHz, which is equivalent to the bandwidth of one PRB (Physical Resource Block) of LTE, that is, 12 subcarriers*15KHz/subcarrier=180KHz, which ensures downlink and LTE compatibility. For example, when using LTE carrier in-band deployment, the orthogonality of the downlink NB-IoT PRB with other LTE PRBs can be maintained.
NB-IoT uplink supports multi-tone and single-tone transmission.

Multi-frequency transmission is based on SC-FDMA with sub-carrier spacing of 15 kHz, 0.5 ms time slot, and 1 ms subframe (same as LTE).
The single-frequency transmission sub-carrier spacing can be 15KHz and 3.75KHz, where 15KHz is the same as LTE to maintain the compatibility of the two in the uplink; wherein when the sub-carrier is 3.75KHz, one slot in the frame structure is 2ms long ( Contains 7 symbols), 15KHz is an integral multiple of 3.75KHz, so there is less interference to the LTE system.
eMTC is an evolution function of LTE. The frequency domain structure is consistent with LTE. It is defined in both TDD and FDD LTE 1.4M~20MHz system bandwidth, but the maximum scheduling of eMTC is 6RB regardless of the bandwidth. The 3GPP definition will be The LTE system broadband is divided into a series of 6 RB narrowband (NB), and the eMTC narrowband division is as follows:

The frame structure of eMTC is consistent with LTE.
4.2 physical channel comparison
NB-IoT physical channel
For the downlink, NB-IoT defines three physical channels:
1NPBCH, narrowband physical broadcast channel
2NPDCCH, narrowband physical downlink control channel
3NPDSCH, narrowband physical downlink shared channel
Two physical signals are also defined:
1NRS, narrowband reference signal
2NPSS and NSSS, primary and secondary synchronization signals
Different from LTE, since the NB-IoT frequency bandwidth has at most one PRB, the downlink physical channels adopt a time division multiplexing mode, that is, they appear alternately at different times.

▲ NB-IoT downlink physical channel and signal time division multiplexing
As shown above, the NB-IoT subframe is allocated to different physical channels and signals, and each NB-IoT subframe is a PRB (12 subcarriers) in the frequency domain and 1 ms in the time domain.
The NPBCH channel is different from the PBCH of LTE. The broadcast period is 640 ms, and the transmission is repeated 8 times. As shown in the following figure, the terminal receives several subframe signals for demodulation.

The NPBCH is located in the subframe #0 in each radio frame, and carries the MIB-NB (Narrowband Master Information Block), and the remaining system information, such as SIB1-NB, is carried in the NPDSCH.
The NPDCCH carries scheduling information of the uplink and downlink data channels, including HARQ acknowledgment information of the uplink data channel, paging indication and random access response scheduling information, data information from higher layers, paging messages, system messages, and random access response messages. Wait.
The PDCCH of the LTE is fixed to use the first few symbols of the subframe, and the difference between the NPDCCH and the PDCCH is large, and the used NCCE (Narrowband Control Channel Element) occupies 6 subcarriers in the frequency domain.
In Stand alone and Guard band mode, all OFDM symbols can be used. In In-Band mode, the control symbol position of LTE is staggered. NPDCCH has two types of format:
The aggregation level of NPDCCH format 0 is 1, occupying NCCE0 or NCCE1.
The aggregation level of NPDCCH format 1 is 2, occupying NCCE0 and NCCE1.
The maximum number of repetitions of the NPDCCH can be matched, ranging from {1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048}.
The NPDSCH frequency domain resource occupies 12 subcarriers, and in Standalone and Guard band modes, all OFDM symbols are used. In the In-band mode, the symbols of the LTE control domain need to be staggered. Since the number of control domain symbols is indicated in the SIB1-NB, if the NPDSCH subframe used by the SIB1-NB is fixed, the first three symbols are fixed.
The NPDSCH modulation mode is QPSK, and the MCS is only 0~12. The number of repetitions {1, 2, 4, 8, 16, 32, 64, 128, 192, 256, 384, 512, 768, 1024, 1536, 2048}.
NRS (Narrowband Reference Signal), also known as pilot signal, is mainly used for downlink channel quality measurement estimation for coherent detection and demodulation of terminals. When used for broadcast and downlink dedicated channels, all downlink subframes are transmitted with NRS, with or without data transmission.

The NRS and the information carrying symbols in the subframes carrying the NPBCH, the NPDCCH, and the NPDSCH are time-frequency multiplexed, and the line port uses 8 REs per subframe per day.
NPSS and NSSS are used by NB-IoT terminals to perform cell search, including time, frequency synchronization, and detection of Cell ID. Since the synchronization sequence of LTE occupies 6 PRBs, NB-IoT cannot occupy these 6 PRBs. To avoid conflicts, NB-IoT needs to be redesigned.
The NPSS is located in subframe 5 (#5) every 10 ms radio frame, with a period of 10 ms, using the last 11 OFDM symbols in each subframe (as shown below).

For NB-IoT terminals, performing NPSS detection is a computationally complex process that is contrary to the goal of simplifying its design. Therefore, NPSS is designed to be a short ZC (Zadoff-Chu) sequence.
The NSSS is located in subframe #9 with a period of 20 ms and appears only in even frames, again using the last 11 OFDM symbols in each subframe.

NPSS provides time and frequency synchronization reference signals for NB-IoT terminals. Unlike LTE, NPSS does not carry any cell information, and NSSS carries PCI.
For the uplink, NB-IoT defines two physical channels:
1NPUSCH, narrowband physical uplink shared channel.
2NPRACH, narrowband physical random access channel.
There is also DMRS, uplink demodulation reference signal.

Pub Time : 2018-07-17 11:15:09 >> News list
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