NB-IoT Deployment Options

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Deployment Options

The channel bandwidth of NB-IoT is 180 kHz which is equal to one LTE Physical Resource Block (PRB). 

Three deployment options are available:

Standalone (reusing unused 200 kHz GSM carriers)
Guard-band (exploiting the guard band between two adjacent LTE carriers)
In-band (where one LTE PRB is reserved for NB-IoT within an LTE carrier bigger than 1.4 MHz.)

In order that they can coexist together, NB-IoT numerology is inherited from LTE. In both uplink and downlink, the channel divided into 12 subcarriers (of 15 kHz each). The time domain is divided into time slots, each lasting 0.5ms and consisting of 7 OFDM/SC-FDMA symbols. 

The smallest time-frequency resource, namely Resource Element (RE), is composed of one subcarrier and one symbol. Time slots are grouped as follows: two time slots form one subframe (1ms), 10 subframes form one frame (10ms). 

Frames are identified by a system frame number, reset every 1024 frames. This structure, repeated 1024 times forms the hyper frame lasting 3 hours. To further improve the coverage, a second numerology with 48 subcarriers of 3.75 kHz each is introduced. 

This numerology is used for transmission of the preamble in RA procedure and optionally for UL transmissions. In this numerology, the time slot lasts 2ms and, for the sake of compatibility, one frame is composed of 5 time slots.

LTE In-band Deployment

In this scenario, operators deploy NB-IoT using existing LTE in-band resource blocks (RBs).

Standalone Deployment

In this scenario, operators deploy NB-IoT using existing idle spectrum resources. These resources can be the operator spectrum fragments with non-standard bandwidths or spared from other radio access technologies (RATs) by re-farming.

LTE Guardband Deployment

Guardband deployment is a deployment scenario in which operators deploy NB-IoT in guard bands within existing LTE spectrum resources.


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