SIGFOX System Description
draft-zuniga-lpwan-sigfox-system-description-00
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Juan-Carlos Zúñiga , Benoît PONSARD | ||
| Last updated | 2016-07-05 | ||
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draft-zuniga-lpwan-sigfox-system-description-00
Network Working Group JC. Zuniga
Internet-Draft B. Ponsard
Intended status: Informational SIGFOX
Expires: January 6, 2017 July 5, 2016
SIGFOX System Description
draft-zuniga-lpwan-sigfox-system-description-00
Abstract
This document presents an overview of the network architecture and
system characteristics of a typical SIGFOX Low Power Wide Area
Network (LPWAN), which is in line with the terminology and
specifications being defined by the ETSI ERM TG28 LTN group. It is
intended to be used as background information by the IETF LPWAN group
when defining system requirements of different LPWAN technologies
that are suitable to support common IP services.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on January 6, 2017.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. System Architecture . . . . . . . . . . . . . . . . . . . . . 3
4. Radio Spectrum . . . . . . . . . . . . . . . . . . . . . . . 5
5. Radio Protocol . . . . . . . . . . . . . . . . . . . . . . . 5
5.1. Uplink . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.1.1. Uplink Physical Layer . . . . . . . . . . . . . . . . 5
5.1.2. Uplink MAC Layer . . . . . . . . . . . . . . . . . . 6
5.2. Downlink . . . . . . . . . . . . . . . . . . . . . . . . 6
5.2.1. Downlink Physical Layer . . . . . . . . . . . . . . . 6
5.2.2. Downlink MAC Layer . . . . . . . . . . . . . . . . . 7
5.3. Synchronization between Uplink and Downlink . . . . . . . 7
6. ETSI LTN . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7. Network Deployment . . . . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
9. Security Considerations . . . . . . . . . . . . . . . . . . . 9
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
11. Informative References . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
This document presents an overview of the network architecture and
system characteristics of a typical SIGFOX LPWAN, which is in line
with the terminology and specifications being defined by the ETSI ERM
TG28 Low Throughput Networks (LTN) group [etsi_ltn]. It is intended
to be used as background information by the IETF LPWAN group when
defining system requirements of different LPWANs that are suitable to
support common IP services.
LPWAN technologies are a subset of IoT systems which specifically
enable long range data transport (e.g. distances up to 50 km in open
field), are capable to communicate with underground equipment, and
require minimal power consumption. Low throughput transmissions
combined with advanced signal processing techniques provide highly
effective protection against interference.
Because of these characteristics, LPWAN systems are particularly well
adapted for low throughput IoT traffic. SIGFOX LPWAN autonomous
battery-operated devices send only a few bytes per day, week or
month, allowing them to remain on a single battery for up to 10-15
years.
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2. Terminology
The following terms used in this document are in accordance to the
ones defined by ETSI ERM TG28 Low Throughput Networks (LTN)
[etsi_ltn]:
Base Station (BS) - A Base Station is a radio hub of an LTN
system.
Device Application (DA) - An application running on the End Point
or device.
End Point (EP) - An End Point is a leaf node (aka device) of an
LTN system that communicates application data between the local
device application and the network application.
Low Throughput Networks (LTN) - Terminology used in ETSI to define
Low Power Wide Area (LPWA) networks.
Network Application (NA) - An application running in the network
at the opposite extreme of the device.
Registration Authority (RA) - The Registration Authority is a
central entity that contains all allocated and authorized End
Point IDs.
Service Center (SC) - Each LTN system has a single service centre.
The SC performs the following functions:
* EPs and BSs management
* EP authentication
* Application data packets forwarding
* Cooperative reception support
3. System Architecture
Figure 1 depicts the different elements of the system architecture:
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+--+
|EP| * +------+
+--+ * | RA |
* +------+
+--+ * |
|EP| * * * * |
+--+ * +----+ |
* | BS | \ +--------+
+--+ * +----+ \ | |
DA -----|EP| * * * | SC |----- NA
+--+ * / | |
* +----+ / +--------+
+--+ * | BS |/
|EP| * * * * +----+
+--+ *
*
+--+ *
|EP| * *
+--+
Figure 1: ETSI LTN architecture
The architecture consists of a single core network, which allows
global connectivity with minimal impact on the end device and radio
access network. The core network elements are the Service Center
(SC) and the Registration Authority (RA). The SC is in charge of the
data connectivity between the Base Station (BS) and the Internet, as
well as the control and management of the BSs and End Points. The RA
is in charge of the End Point network access authorization.
The radio access network is comprised of several BSs connected
directly to the SC. Each BS performs complex L1/L2 functions,
leaving some L2 and L3 functionalities to the SC.
The devices or End Points (EPs) are the objects that communicate
application data between local device applications (DAs) and network
applications (NAs).
EPs (or devices) can be static or nomadic, as they associate with the
SC and they do not attach to a specific BS. Hence, they can
communicate with the SC through one or many BSs.
Due to constraints in the complexity of the EP, it is assumed that
EPs host only one or very few device applications, which communicate
to one single network application at a time.
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4. Radio Spectrum
The radio interface is compliant with the following regulations:
Spectrum allocation in the USA [fcc_ref],
Spectrum allocation in Europe [etsi_ref],
Spectrum allocation in Japan [arib_ref].
At present, the SIGFOX LTN radio interface is also compliant with the
local regulations of the following countries: Australia, Brazil,
Canada, Kenya, Lebanon, Mauritius, Mexico, New Zealand, Oman, Peru,
Singapore, South Africa, South Korea, and Thailand.
5. Radio Protocol
The radio interface is based on Ultra Narrow Band (UNB)
communications, which allow an increased transmission range by
spending a limited amount of energy at the device. Moreover, UNB
allows a large number of devices to coexist in a given cell without
significantly increasing the spectrum interference.
Both uplink and downlink communications are possible with the UNB
solution. Due to spectrum optimizations, different uplink and
downlink frames and time synchronization methods are needed.
5.1. Uplink
5.1.1. Uplink Physical Layer
The main radio characteristics of the UNB uplink transmission are:
o Channelization mask: 100 Hz (600 Hz in the USA)
o Uplink baud rate: 100 baud (600 baud in the USA)
o Modulation scheme: DBPSK
o Uplink transmission power: compliant with local regulation
o Link budget: 155 dB (or better)
o Central frequency accuracy: not relevant, provided there is no
significant frequency drift within an uplink packet
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In Europe, the UNB uplink frequency band is limited to 868,00 to
868,60 MHz, with a maximum output power of 25 mW and a maximum mean
transmission time of 1%.
5.1.2. Uplink MAC Layer
The format of the uplink frame is the following:
+--------+--------+--------+------------------+-------------+-----+
|Preamble| Frame | Dev ID | Payload |Msg Auth Code| FCS |
| | Sync | | | | |
+--------+--------+--------+------------------+-------------+-----+
Figure 2: Uplink Frame Format
The uplink frame is composed of the following fields:
o Preamble: 19 bits
o Frame sync and header: 29 bits
o Device ID: 32 bits
o Payload: 0-96 bits
o Authentication: 16-40 bits
o Frame check sequence: 16 bits (CRC)
5.2. Downlink
5.2.1. Downlink Physical Layer
The main radio characteristics of the UNB downlink transmission are:
o Channelization mask: 1.5 kHz
o Downlink baud rate: 600 baud
o Modulation scheme: GFSK
o Downlink transmission power: 500 mW (4W in the USA)
o Link budget: 153 dB (or better)
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o Central frequency accuracy: Centre frequency of downlink
transmission are set by the network according to the corresponding
uplink transmission.
In Europe, the UNB downlink frequency band is limited to 869,40 to
869,65 MHz, with a maximum output power of 500 mW with 10% duty
cycle.
5.2.2. Downlink MAC Layer
The format of the downlink frame is the following:
+------------+-----+---------+------------------+-------------+-----+
| Preamble |Frame| ECC | Payload |Msg Auth Code| FCS |
| |Sync | | | | |
+------------+-----+---------+------------------+-------------+-----+
Figure 3: Downlink Frame Format
The downlink frame is composed of the following fields:
o Preamble: 91 bits
o Frame sync and header: 13 bits
o Error Correcting Code (ECC): 32 bits
o Payload: 0-64 bits
o Authentication: 16 bits
o Frame check sequence: 8 bits (CRC)
5.3. Synchronization between Uplink and Downlink
The radio interface is optimized for uplink transmissions, which are
asynchronous. Downlink communications are achieved by querying the
network for existing data from the device.
A device willing to receive downlink messages opens a fixed window
for reception after sending an uplink transmission. The delay and
duration of this window have fixed values. The LTN network transmits
the downlink message for a given device during the reception window.
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The LTN network selects the BS for transmitting the corresponding
downlink message.
Uplink and downlink transmissions are unbalanced due to the
regulatory constraints on the ISM bands. Under the strictest
regulations, the system can allow a maximum of 140 uplink messages
and 4 downlink messages per device. These restrictions can be
slightly relaxed depending on system conditions and the specific
regulatory domain of operation.
6. ETSI LTN
The ETSI TC EMC and Radio Spectrum Matters (ERM) group has multiple
work items dealing with LTN. The objective is to define use cases,
system architecture and radio protocols for LTN (or LPWAN), using
shared spectrum bands, allowing to offer very low cost subscriptions
per device.
According to ETSI, LTN is particularly well suited for low throughput
machine to machine communication where data volume is limited and low
latency is not a strong requirement. Some foreseen applications
include remote measurement for agriculture and environment, smart
metering for utilities, smart cities applications such as air
pollution monitoring or public lighting, etc.
LTN could also cooperate with cellular networks to address use cases
where redundancy, complementary or alternative connectivity is
needed. Low power, very low throughput, very long battery life,
simple, effective and robust radio communication principles are the
key features of ETSI LTN systems.
7. Network Deployment
As of today, the SIGFOX LPWAN/LTN has been fully deployed in 6
countries, with ongoing deployments on 14 other countries, which in
total will reach 316M people.
The vast majority of the current applications are sensor-based,
requiring solely uplink communications, followed by actuator-based
applications, which make use of bidirectional (i.e. uplink and
downlink) communications.
Similar to other LPWAN/LTN technologies, the sectors that currently
benefit from the low-cost, low-maintenance and long battery life are
agricultural and environment, public sector (smart cities, education,
security, etc.), industry, utilities, retail, home and lifestyle,
health and automotive.
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8. IANA Considerations
N/A.
9. Security Considerations
The radio protocol provides mechanisms to authenticate and ensure
integrity of the message. This is achieved by using a unique device
ID and a message authentication code, which allow ensuring that the
message has been generated and sent by the device with the ID claimed
in the message.
Security keys are independent for each device. These keys are
associated with the device ID and they are pre-provisioned.
Application data can be encrypted by the application provider.
10. Acknowledgments
The authors would like to thank Olivier Peyrusse for the useful
inputs and discussions about ETSI LTN.
11. Informative References
[arib_ref]
"ARIB STD-T108 (Version 1.0): 920MHz-Band Telemeter,
Telecontrol and data transmission radio equipment.",
February 2012.
[etsi_ltn]
"ETSI Technical Committee on EMC and Radio Spectrum
Matters (ERM) TG28 Low Throughput Networks (LTN)",
February 2015.
[etsi_ref]
"ETSI EN 300-220 (Parts 1 and 2): Electromagnetic
compatibility and Radio spectrum Matters (ERM); Short
Range Devices (SRD); Radio equipment to be used in the 25
MHz to 1 000 MHz frequency range with power levels ranging
up to 500 mW", May 2016.
[fcc_ref] "FCC CFR 47 Part 15.247 Telecommunication Radio Frequency
Devices - Operation within the bands 902-928 MHz,
2400-2483.5 MHz, and 5725-5850 MHz.", June 2016.
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Authors' Addresses
Juan Carlos Zuniga
SIGFOX
425 rue Jean Rostand
Labege 31670
France
Email: JuanCarlos.Zuniga@sigfox.com
URI: http://www.sigfox.com/
Benoit Ponsard
SIGFOX
425 rue Jean Rostand
Labege 31670
France
Email: Benoit.Ponsard@sigfox.com
URI: http://www.sigfox.com/
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