3GPP/GSMA technologies for LPWAN in the Licensed Spectrum
3GPP/GSMA technologies for LPWAN
in the the Licensed Spectrum
NB-IoT, LTE-M & EC-GSM
Avijit Ghosh, Aricent
The LPWAN Playing Field
1. Traffic pattern that is not downlink
dominated (and may even be uplink
2. Traffic in very short bursts (may be as
short as a single message or a pair of
3. Terminals that don’t move much
(nomadic) or don’t move at all (static)
4. Terminals that talk to very few peers –
may be just to a single ‘server’
1. Eliminating unnecessary
signalling: C/P & U/P
2. Support of High Latency
models: (e-)DRX & PSM
1. Low system bandwidth
2. Half-duplex communication
Low Device Cost
= Circuit Simplicity
Long Battery Life
= Low Power
= Long Range
or Coverage in Difficult
Evolution of IoT Connectivity in 3GPP/GSMA
5 MHz200 kHz 1.4 MHz 5/10/15/20 MHz
GSM LTE Cat-1+
GSM is the original wide-area M2M
wireless connectivity technology. EC-GSM
enhances it to keep it competitive.
UMTS did not see any significant push
towards a low-power variant.
LTE-M (Cat-M1) is a concession to the
low-power/low-throughput device within
NB-IoT (Cat-NB1), a new RAN technology,
is the official LPWAN contestant from the
Band 5/26 8 2 3 1 66 12/17 13 28 18+19 20 Other LTE Bands
U/L (MHz) 814-849 880-915 1850-1910 1710-1785 1920-1980 1710-1780 699-716 777-787 703-748 815-845 832-862
FDD & TDD
D/L (MHz) 859-894 925-960 1930-1990 1805-1880 2110-2170 2110-2180 729-746 746-756 758-803 860-890 791-821
EC-GSM Y Y Y Y
NB-IoT Y Y Y Y Y Y Y Y Y Y Y
LTE-M Y Y Y Y Y Y Y Y Y Y Y Y
All three 3GPP/GSMA radio technologies are designed to be used in the Licensed Spectrum only
(the ‘fair sharing’ etiquettes required for the Unlicensed Spectrum aren’t addressed)
None of them can be used for a Licensed Spectrum allocation of less than 200 kHz
(and the allocation must come from one of the bands listed in the table above)
This makes them unattractive for private/operator-less networks
Conclusion: The Right Compromise?
1. Device Complexity: Much simpler than ‘full’ LTE – but much more complex when compared to LPWAN competitors on the license-exempt
spectrum. Lots of options, too.
2. Simplified Radio Procedures: (In NB-IoT) No measurements, CQI reports & handovers, taking advantage of the fact that transactions are
3. Multiple Traffic Types:
A. SMS Traffic, where traffic is addressed by E.164 number (a.k.a. phone number.) UE does not need to know its own address.
B. Non-IP Traffic (not yet available for EC-GSM) which…
I. Can be application-specific data with source/destination identified implicitly by subscription context (IMSI) taking
advantage of the fact that an IoT device usually talks to only one endpoint.
II. Alternatively, can be something like 6LoWPAN where the addressing is left to the payload layer.
C. IP Traffic (with RoHC header compression support) where traffic is identified by IP (v4/v6) addresses. The address of the UE is
assigned by the core network.
4. Still using SIM & IMSI: With a 15-digit IMSI, each operator (MCC+MNC) has a 1 billion IMSI pool even when the MNC is 3-digit. The SIM
may be ‘embedded’ … or not.
5. Global Reach: Due to the roaming capabilities that come with the membership of the 3GPP/GSMA extended family.
PSM & (e-)DRX: High Latency Communication
(Paging, Measurements, etc.)
Signalling Reduction: C/P & U/P Optimization
Connection Setup Complete (+ Data Message) Initial Message (+ Data Message)
Connection Resume Request (+ resume-id)
Connection Resume Complete
Data (GTP-U)Data (DRB: PDCP/RLC/MAC)
Connection Release (+ resume-id)
Connection Setup Complete (+ Srv. Req.)
Data (GTP-U)Data (DRB: PDCP/RLC/MAC)
Initial Message (+ Srv. Req.)
Security Mode Command Initial Context Setup Request
Connection Reconfiguration Complete Initial Context Setup Response
Security Mode Complete
Repetition: Coverage Enhancement
The noise component is zero mean, so a sum over ‘M’ samples will approach zero.
The signal component is the same for all repetitions. A sum over ‘M’ samples will
simply be M times the signal … provided doesn’t change.
If the device doesn’t move a lot, it can be expected that will not change too much.