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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