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Checking references for intended status: Informational ---------------------------------------------------------------------------- No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 LPWAN Working Group JC. Zuniga 3 Internet-Draft B. Ponsard 4 Intended status: Informational SIGFOX 5 Expires: September 14, 2017 March 13, 2017 7 SIGFOX System Description 8 draft-zuniga-lpwan-sigfox-system-description-02 10 Abstract 12 This document presents an overview of the network architecture and 13 system characteristics of a typical SIGFOX Low Power Wide Area 14 Network (LPWAN), which is in line with the terminology and 15 specifications being defined by the ETSI ERM TG28 LTN group. It is 16 intended to be used as background information by the IETF LPWAN group 17 when defining system requirements of different LPWAN technologies 18 that are suitable to support common IP services. 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at http://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on September 14, 2017. 37 Copyright Notice 39 Copyright (c) 2017 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (http://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 55 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 56 3. System Architecture . . . . . . . . . . . . . . . . . . . . . 3 57 4. Radio Spectrum . . . . . . . . . . . . . . . . . . . . . . . 5 58 5. Radio Protocol . . . . . . . . . . . . . . . . . . . . . . . 5 59 5.1. Uplink . . . . . . . . . . . . . . . . . . . . . . . . . 5 60 5.1.1. Uplink Physical Layer . . . . . . . . . . . . . . . . 5 61 5.1.2. Uplink MAC Layer . . . . . . . . . . . . . . . . . . 6 62 5.2. Downlink . . . . . . . . . . . . . . . . . . . . . . . . 6 63 5.2.1. Downlink Physical Layer . . . . . . . . . . . . . . . 6 64 5.2.2. Downlink MAC Layer . . . . . . . . . . . . . . . . . 7 65 5.3. Synchronization between Uplink and Downlink . . . . . . . 7 66 6. ETSI LTN . . . . . . . . . . . . . . . . . . . . . . . . . . 8 67 7. Network Deployment . . . . . . . . . . . . . . . . . . . . . 8 68 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 69 9. Security Considerations . . . . . . . . . . . . . . . . . . . 9 70 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 71 11. Informative References . . . . . . . . . . . . . . . . . . . 9 72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 74 1. Introduction 76 This document presents an overview of the network architecture and 77 system characteristics of a typical SIGFOX LPWAN, which is in line 78 with the terminology and specifications being defined by the ETSI ERM 79 TG28 Low Throughput Networks (LTN) group [etsi_ltn]. It is intended 80 to be used as background information by the IETF LPWAN group when 81 defining system requirements of different LPWANs that are suitable to 82 support common IP services. 84 LPWAN technologies are a subset of IoT systems which specifically 85 enable long range data transport (e.g. distances up to 50 km in open 86 field), are capable to communicate with underground equipment, and 87 require minimal power consumption. Low throughput transmissions 88 combined with advanced signal processing techniques provide highly 89 effective protection against interference. 91 Because of these characteristics, LPWAN systems are particularly well 92 adapted for low throughput IoT traffic. SIGFOX LPWAN autonomous 93 battery-operated devices send only a few bytes per day, week or month 94 in an asynchronous manner and without the needed for central 95 coordination, which allows them to remain on a single battery for up 96 to 10-15 years. 98 2. Terminology 100 The following terms used in this document are in accordance to the 101 ones defined by ETSI ERM TG28 Low Throughput Networks (LTN) 102 [etsi_ltn]: 104 Base Station (BS) - A Base Station is a radio hub of an LTN 105 system. 107 Device Application (DA) - An application running on the End Point 108 or device. 110 End Point (EP) - An End Point is a leaf node (aka device) of an 111 LTN system that communicates application data between the local 112 device application and the network application. 114 Low Throughput Networks (LTN) - Terminology used in ETSI to define 115 Low Power Wide Area (LPWA) networks. 117 Network Application (NA) - An application running in the network 118 at the opposite extreme of the device. 120 Registration Authority (RA) - The Registration Authority is a 121 central entity that contains all allocated and authorized End 122 Point IDs. 124 Service Center (SC) - Each LTN system has a single service centre. 125 The SC performs the following functions: 127 * EPs and BSs management 129 * EP authentication 131 * Application data packets forwarding 133 * Cooperative reception support 135 3. System Architecture 137 Figure 1 depicts the different elements of the system architecture: 139 +--+ 140 |EP| * +------+ 141 +--+ * | RA | 142 * +------+ 143 +--+ * | 144 |EP| * * * * | 145 +--+ * +----+ | 146 * | BS | \ +--------+ 147 +--+ * +----+ \ | | 148 DA -----|EP| * * * | SC |----- NA 149 +--+ * / | | 150 * +----+ / +--------+ 151 +--+ * | BS |/ 152 |EP| * * * * +----+ 153 +--+ * 154 * 155 +--+ * 156 |EP| * * 157 +--+ 159 Figure 1: ETSI LTN architecture 161 The architecture consists of a single core network, which allows 162 global connectivity with minimal impact on the end device and radio 163 access network. The core network elements are the Service Center 164 (SC) and the Registration Authority (RA). The SC is in charge of the 165 data connectivity between the Base Station (BS) and the Internet, as 166 well as the control and management of the BSs and End Points. The RA 167 is in charge of the End Point network access authorization. 169 The radio access network is comprised of several BSs connected 170 directly to the SC. Each BS performs complex L1/L2 functions, 171 leaving some L2 and L3 functionalities to the SC. 173 The devices or End Points (EPs) are the objects that communicate 174 application data between local device applications (DAs) and network 175 applications (NAs). 177 EPs (or devices) can be static or nomadic, as they associate with the 178 SC and they do not attach to a specific BS. Hence, they can 179 communicate with the SC through one or many BSs. 181 Due to constraints in the complexity of the EP, it is assumed that 182 EPs host only one or very few device applications, which communicate 183 to one single network application at a time. 185 4. Radio Spectrum 187 The radio interface is compliant with the following regulations: 189 Spectrum allocation in the USA [fcc_ref], 191 Spectrum allocation in Europe [etsi_ref], 193 Spectrum allocation in Japan [arib_ref]. 195 At present, the SIGFOX LTN radio interface is also compliant with the 196 local regulations of the following countries: Australia, Brazil, 197 Canada, Kenya, Lebanon, Mauritius, Mexico, New Zealand, Oman, Peru, 198 Singapore, South Africa, South Korea, and Thailand. 200 5. Radio Protocol 202 The radio interface is based on Ultra Narrow Band (UNB) 203 communications, which allow an increased transmission range by 204 spending a limited amount of energy at the device. Moreover, UNB 205 allows a large number of devices to coexist in a given cell without 206 significantly increasing the spectrum interference. 208 Both uplink and downlink communications are possible with the UNB 209 solution. Due to spectrum optimizations, different uplink and 210 downlink frames and time synchronization methods are needed. 212 5.1. Uplink 214 5.1.1. Uplink Physical Layer 216 The main radio characteristics of the UNB uplink transmission are: 218 o Occupied bandwidth: 100 Hz in Europe, 600 Hz in the USA 220 o Uplink baud rate: 100 baud in Europe, 600 baud in the USA 222 o Modulation scheme: DBPSK 224 o Uplink transmission power: compliant with local regulation 226 o Link budget: 155 dB (or better) 228 o Central frequency accuracy: not relevant, provided there is no 229 significant frequency drift within an uplink packet 231 In Europe, the UNB uplink frequency band is limited to 868,00 to 232 868,60 MHz, with a maximum output power of 25 mW and a maximum mean 233 transmission time of 1%. 235 5.1.2. Uplink MAC Layer 237 The format of the uplink frame is the following: 239 +--------+--------+--------+------------------+-------------+-----+ 240 |Preamble| Frame | Dev ID | Payload |Msg Auth Code| FCS | 241 | | Sync | | | | | 242 +--------+--------+--------+------------------+-------------+-----+ 244 Figure 2: Uplink Frame Format 246 The uplink frame is composed of the following fields: 248 o Preamble: 19 bits 250 o Frame sync and header: 29 bits 252 o Device ID: 32 bits 254 o Payload: 0-96 bits 256 o Authentication: 16-40 bits 258 o Frame check sequence: 16 bits (CRC) 260 5.2. Downlink 262 5.2.1. Downlink Physical Layer 264 The main radio characteristics of the UNB downlink transmission are: 266 o Occupied bandwidth: 1.5 kHz 268 o Downlink baud rate: 600 baud 270 o Modulation scheme: GFSK 272 o Downlink transmission power: 500 mW in Europe, 4W in the USA 274 o Link budget: 153 dB (or better) 275 o Central frequency accuracy: Centre frequency of downlink 276 transmission are set by the network according to the corresponding 277 uplink transmission. 279 In Europe, the UNB downlink frequency band is limited to 869,40 to 280 869,65 MHz, with a maximum output power of 500 mW with 10% duty 281 cycle. 283 5.2.2. Downlink MAC Layer 285 The format of the downlink frame is the following: 287 +------------+-----+---------+------------------+-------------+-----+ 288 | Preamble |Frame| ECC | Payload |Msg Auth Code| FCS | 289 | |Sync | | | | | 290 +------------+-----+---------+------------------+-------------+-----+ 292 Figure 3: Downlink Frame Format 294 The downlink frame is composed of the following fields: 296 o Preamble: 91 bits 298 o Frame sync and header: 13 bits 300 o Error Correcting Code (ECC): 32 bits 302 o Payload: 0-64 bits 304 o Authentication: 16 bits 306 o Frame check sequence: 8 bits (CRC) 308 5.3. Synchronization between Uplink and Downlink 310 The radio interface is optimized for uplink transmissions, which are 311 asynchronous. Downlink communications are achieved by querying the 312 network for existing data from the device. 314 A device willing to receive downlink messages opens a fixed window 315 for reception after sending an uplink transmission. The delay and 316 duration of this window have fixed values. The LTN network transmits 317 the downlink message for a given device during the reception window. 319 The LTN network selects the BS for transmitting the corresponding 320 downlink message. 322 Uplink and downlink transmissions are unbalanced due to the 323 regulatory constraints on the ISM bands. Under the strictest 324 regulations, the system can allow a maximum of 140 uplink messages 325 and 4 downlink messages per device. These restrictions can be 326 slightly relaxed depending on system conditions and the specific 327 regulatory domain of operation. 329 6. ETSI LTN 331 The ETSI TC EMC and Radio Spectrum Matters (ERM) group has multiple 332 work items dealing with LTN. The objective is to define use cases, 333 system architecture and radio protocols for LTN (or LPWAN), using 334 shared spectrum bands, allowing to offer very low cost subscriptions 335 per device. 337 According to ETSI TG28, LTN is particularly well suited for low 338 throughput machine to machine communication where data volume is 339 limited and low latency is not a strong requirement. Some foreseen 340 applications include remote measurement for agriculture and 341 environment, smart metering for utilities, smart cities applications 342 such as air pollution monitoring or public lighting, etc. 344 LTN could also cooperate with cellular networks to address use cases 345 where redundancy, complementary or alternative connectivity is 346 needed. Low power, very low throughput, very long battery life, 347 simple, effective and robust radio communication principles are the 348 key features of ETSI LTN systems. 350 7. Network Deployment 352 As of March 2017, SIGFOX's network has been fully deployed in 6 353 countries, with ongoing deployments on 26 other countries. The one- 354 contract one-network model allows devices to connect in any country, 355 without any notion of roaming. 357 The vast majority of the current applications are sensor-based, 358 requiring solely uplink communications, followed by actuator-based 359 applications, which make use of bidirectional (i.e. uplink and 360 downlink) communications. 362 Similar to other LPWAN/LTN technologies, the sectors that currently 363 benefit from the low-cost, low-maintenance and long battery life are 364 agricultural and environment, public sector (smart cities, education, 365 security, etc.), industry, utilities, retail, home and lifestyle, 366 health and automotive. 368 8. IANA Considerations 370 N/A. 372 9. Security Considerations 374 The radio protocol provides mechanisms to authenticate and ensure 375 integrity of the message. This is achieved by using a unique device 376 ID and a message authentication code, which allow ensuring that the 377 message has been generated and sent by the device with the ID claimed 378 in the message. 380 Security keys are independent for each device. These keys are 381 associated with the device ID and they are pre-provisioned. 382 Application data can be encrypted by the application provider. 384 10. Acknowledgments 386 The authors would like to thank Olivier Peyrusse for the useful 387 inputs and discussions about ETSI LTN. 389 11. Informative References 391 [arib_ref] 392 "ARIB STD-T108 (Version 1.0): 920MHz-Band Telemeter, 393 Telecontrol and data transmission radio equipment.", 394 February 2012. 396 [etsi_ltn] 397 "ETSI Technical Committee on EMC and Radio Spectrum 398 Matters (ERM) TG28 Low Throughput Networks (LTN)", 399 February 2015. 401 [etsi_ref] 402 "ETSI EN 300-220 (Parts 1 and 2): Electromagnetic 403 compatibility and Radio spectrum Matters (ERM); Short 404 Range Devices (SRD); Radio equipment to be used in the 25 405 MHz to 1 000 MHz frequency range with power levels ranging 406 up to 500 mW", May 2016. 408 [fcc_ref] "FCC CFR 47 Part 15.247 Telecommunication Radio Frequency 409 Devices - Operation within the bands 902-928 MHz, 410 2400-2483.5 MHz, and 5725-5850 MHz.", June 2016. 412 Authors' Addresses 414 Juan Carlos Zuniga 415 SIGFOX 416 425 rue Jean Rostand 417 Labege 31670 418 France 420 Email: JuanCarlos.Zuniga@sigfox.com 421 URI: http://www.sigfox.com/ 423 Benoit Ponsard 424 SIGFOX 425 425 rue Jean Rostand 426 Labege 31670 427 France 429 Email: Benoit.Ponsard@sigfox.com 430 URI: http://www.sigfox.com/