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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 Internet Engineering Task Force A. Ratilainen 3 Internet-Draft Ericsson 4 Intended status: Informational July 8, 2016 5 Expires: January 9, 2017 7 NB-IoT characteristics 8 draft-ratilainen-lpwan-nb-iot-00 10 Abstract 12 Low Power Wide Area Networks (LPWAN) are wireless technologies 13 covering different Internet of Things (IoT) applications. The common 14 characteristics for LPWANs are large coverage, low bandwidth, small 15 data sizes and long battery life operation. One of these 16 technologies include Narrowband Internet of Things (NB-IoT) developed 17 and standardized by 3GPP. This document is an informational overview 18 to NB-IoT and gives the principal characteristics and restrictions of 19 this technology in order to help with the IETF work for providing 20 IPv6 connectivity to NB-IoT along with other LPWANs. 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on January 9, 2017. 39 Copyright Notice 41 Copyright (c) 2016 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 2. Overview of the NB-IoT technology . . . . . . . . . . . . . . 3 58 3. System architecture . . . . . . . . . . . . . . . . . . . . . 4 59 4. NB-IoT worst case performance . . . . . . . . . . . . . . . . 7 60 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 61 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 62 7. Informative References . . . . . . . . . . . . . . . . . . . 8 63 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9 65 1. Introduction 67 The purpose of this document is to provide background information and 68 typical link characteristics about NarrowBand Internet of Things (NB- 69 IoT) to be considered in IETF's 6LPWA work. 71 NB-IoT is a Low Power Wide Area (LPWA) technology being standardized 72 by the 3GPP. NB-IoT has been developed with the following objectives 73 in mind: 75 o Improved indoor coverage 77 o Support of massive number of low throughput devices 79 o Low delay sensitivity 81 o Ultra-low device cost 83 o Low device power consumption 85 o Optimized network architecture 87 The standardization of NB-IoT was finalized with 3GPP Release-13 in 88 June 2016, but further enhancements for NB-IoT are worked on in the 89 following releases, for example in the form of multicast support. 90 For more information of what has been specified for NB-IoT, 3GPP 91 specification 36.300 [TGPP36300] provides an overview and overall 92 description of the E-UTRAN radio interface protocol architecture, 93 while specifications 36.321 [TGPP36321], 36.322 [TGPP36322], 36.323 94 [TGPP36323] and 36.331 [TGPP36331] give more detailed description of 95 MAC, RLC, PDCP and RRC protocol layers respectively. The new 96 versions of the specifications including NB-IoT are not yet available 97 due to novelty of the feature, but should be shortly available in the 98 3GPP website. 100 2. Overview of the NB-IoT technology 102 Machine type communication (MTC) refers to the emerging type of 103 wireless communications where machine-like devices talk to each other 104 through mobile networks or locally. Its requirements range from 105 Massive MTC type of data with low cost, low energy consumption, small 106 data volumes and massive numbers to critical MTC type of high 107 reliability, very low latency and very high availability. 109 NB-IoT has been designed to satisfy a plethora of use cases and 110 combination of these requirements, but especially NB-IoT targets the 111 low-end Massive MTC scenario with following requirements: Less than 112 5$ module cost, extended coverage of 164 dB maximum coupling loss, 113 battery life of over 10 years, ~55000 devices per cell and uplink 114 reporting latency of less than 10 seconds. 116 NB-IoT supports Half Duplex FDD operation mode with 60 kbps peak rate 117 in uplink and 30 kbps peak rate in downlink. Highest modulation 118 scheme is QPSK in both uplink and downlink. As the name suggests, 119 NB-IoT uses narrowbands with the bandwidth of 180 kHz in both, 120 downlink and uplink. The multiple access scheme used in the downlink 121 is OFDMA with 15 kHz sub-carrier spacing. On uplink multi-tone SC- 122 FDMA is used with 15 kHz tone spacing or as a special case of SC-FDMA 123 single tone with either 15kHz or 3.75 kHz tone spacing may be used. 124 These schemes have been selected to reduce the User Equipment (UE) 125 complexity. 127 NB-IoT can be deployed in three ways. In-band deployment means that 128 the narrowband is multiplexed within normal LTE carrier. In Guard- 129 band deployment the narrowband uses the unused resource blocks 130 between two adjacent LTE carriers. Also standalone deployment is 131 supported, where the narrowband can be located alone in dedicated 132 spectrum, which makes it possible for example to refarm the GSM 133 carrier at 850/900 MHz for NB-IoT. All three deployment modes are 134 meant to be used in licensed bands. The maximum transmission power 135 is either 20 or 23 dBm for uplink transmissions, while for downlink 136 transmission the eNodeB may use higher transmission power, up to 46 137 dBm depending on the deployment. 139 For signaling optimization, two options are introduced in addition to 140 legacy RRC connection setup, mandatory Data-over-NAS (Control Plane 141 optimization, solution 2 in [TGPP23720]) and optional RRC Suspend/ 142 Resume (User Plane optimization, solution 18 in [TGPP23720]). In the 143 control plane optimization the data is sent over Non Access Stratum, 144 directly from Mobility Management Entity (MME) in core network to the 145 UE without interaction from base station. This means there are no 146 Access Stratum security or header compression, as the Access Stratum 147 is bypassed, and only limited RRC procedures. 149 The RRC Suspend/Resume procedures reduce the signaling overhead 150 required for UE state transition from Idle to Connected mode in order 151 to have a user plane transaction with the network and back to Idle 152 state by reducing the signaling messages required compared to legacy 153 operation 155 With extended DRX the RRC Connected mode DRX cycle is up to 10.24 156 seconds and in RRC Idle the DRX cycle can be up to 3 hours. 158 To recap, the following is a list of the most important 159 characteristics of NB-IoT: 161 o Narrowband operation (180 kHz bandwidth) in licensed bands, either 162 in in-band, guard band or standalone operation mode 164 o Support for 1 Data Radio Bearer (DRB) is mandatory, 2 additional 165 DRBs are optional 167 o Maximum peak rate is 60 kbps in UL and 30 kbps in DL 169 o No channel access restrictions (up to 100% duty cycle) 171 o The maximum size of PDCP SDU and PDCP control PDU is 1600 octets 172 in NB-IoT 174 o Data over non-access stratum is supported 176 o With eDRX, DRX cycle is up to 10.24 seconds in connected mode and 177 up to 3 hours in idle mode 179 3. System architecture 181 NB-IoT network architecture is based on the network architecture of 182 legacy LTE, which is illustrated in Figure 1. It consists of core 183 network, called Evolved Packet Core (EPC), Evolved UMTS Terrestrial 184 Radio Access Network (E-UTRAN) and the User Equipment (UE). Next we 185 take a look at the key components of EPC. 187 +--+ 188 |UE| \ +------+ +------+ 189 +--+ \ | MME |------| HSS | 190 \ / +------+ +------+ 191 +--+ \+-----+ / | 192 |UE| ----| eNB |- | 193 +--+ /+-----+ \ | 194 / \ +--------+ 195 / \| | +------+ Service PDN 196 +--+ / | S-GW |----| P-GW |---- e.g. Internet 197 |UE| | | +------+ 198 +--+ +--------+ 200 Figure 1: 3GPP network architecture 202 Mobility Management Entity (MME) is responsible for handling the 203 mobility of the UE. MME tasks include tracking and paging UEs, 204 session management, choosing the Serving gateway for the UE during 205 initial attachment and authenticating the user. At MME, the Non 206 Access Stratum (NAS) signaling from the UE is terminated. 208 Serving Gateway (S-GW) routes and forwards the user data packets 209 through the access network and acts as a mobility anchor for UEs 210 during handover between base stations known as eNodeBs and also 211 during handovers between other 3GPP technologies. 213 Packet Data Node Gateway (P-GW) works as an interface between 3GPP 214 network and external networks. 216 Home Subscriber Server (HSS) contains user-related and subscription- 217 related information. It is a database, which performs mobility 218 management, session establishment support, user authentication and 219 access authorization. 221 E-UTRAN consists of components of a single type, eNodeB. eNodeB is a 222 base station, which controls the UEs in one or several cells. 224 The illustration of 3GPP radio protocol architecture can be seen from 225 Figure 2. 227 +---------+ +---------+ 228 | NAS |----|-----------------------------|----| NAS | 229 +---------+ | +---------+---------+ | +---------+ 230 | RRC |----|----| RRC | S1-AP |----|----| S1-AP | 231 +---------+ | +---------+---------+ | +---------+ 232 | PDCP |----|----| PDCP | SCTP |----|----| SCTP | 233 +---------+ | +---------+---------+ | +---------+ 234 | RLC |----|----| RLC | IP |----|----| IP | 235 +---------+ | +---------+---------+ | +---------+ 236 | MAC |----|----| MAC | L2 |----|----| L2 | 237 +---------+ | +---------+---------+ | +---------+ 238 | PHY |----|----| PHY | PHY |----|----| PHY | 239 +---------+ +---------+---------+ +---------+ 240 LTE-Uu S1-MME 241 UE eNodeB MME 243 Figure 2: 3GPP radio protocol architecture 245 The radio protocol architecture of NB-IoT (and LTE) is separated into 246 control plane and user plane. Control plane consists of protocols 247 which control the radio access bearers and the connection between the 248 UE and the network. The highest layer of control plane is called 249 Non-Access Stratum (NAS), which conveys the radio signaling between 250 the UE and the EPC, passing transparently through radio network. It 251 is responsible for authentication, security control, mobility 252 management and bearer management. 254 Access Stratum (AS) is the functional layer below NAS, and in control 255 plane it consists of Radio Resource Control protocol (RRC) 256 [TGPP36331], which handles connection establishment and release 257 functions, broadcast of system information, radio bearer 258 establishment, reconfiguration and release. RRC configures the user 259 and control planes according to the network status. There exists two 260 RRC states, RRC_Idle or RRC_Connected, and RRC entity controls the 261 switching between these states. In RRC_Idle, the network knows that 262 the UE is present in the network and the UE can be reached in case of 263 incoming call. In this state the UE monitors paging, performs cell 264 measurements and cell selection and acquires system information. 265 Also the UE can receive broadcast and multicast data, but it is not 266 expected to transmit or receive singlecast data. In RRC_Connected 267 the UE has a connection to the eNodeB, the network knows the UE 268 location on cell level and the UE may receive and transmit singlecast 269 data. RRC_Connected mode is established, when the UE is expected to 270 be active in the network, to transmit or receive data. Connection is 271 released, switching to RRC_Idle, when there is no traffic to save the 272 UE battery and radio resources. However, a new feature was 273 introduced for NB-IoT, as mentioned earlier, which allows data to be 274 transmitted from the MME directly to the UE, while the UE is in 275 RRC_Idle transparently to the eNodeB. 277 Packet Data Convergence Protocol's (PDCP) [TGPP36323] main services 278 in control plane are transfer of control plane data, ciphering and 279 integrity protection. 281 Radio Link Control protocol (RLC) [TGPP36322] performs transfer of 282 upper layer PDUs and optionally error correction with Automatic 283 Repeat reQuest (ARQ), concatenation, segmentation and reassembly of 284 RLC SDUs, in-sequence delivery of upper layer PDUs, duplicate 285 detection, RLC SDU discard, RLC-re-establishment and protocol error 286 detection and recovery. 288 Medium Access Control protocol (MAC) [TGPP36321] provides mapping 289 between logical channels and transport channels, multiplexing of MAC 290 SDUs, scheduling information reporting, error correction with HARQ, 291 priority handling and transport format selection. 293 Physical layer [TGPP36201] provides data transport services to higher 294 layers. These include error detection and indication to higher 295 layers, FEC encoding, HARQ soft-combining. Rate matching and mapping 296 of the transport channels onto physical channels, power weighting and 297 modulation of physical channels, frequency and time synchronization 298 and radio characteristics measurements. 300 User plane is responsible for transferring the user data through the 301 Access Stratum. It interfaces with IP and consists of PDCP, which in 302 user plane performs header compression using Robust Header 303 Compression (RoHC), transfer of user plane data between eNodeB and 304 UE, ciphering and integrity protection. Lower layers in user plane 305 are similarly RLC, MAC and physical layer performing tasks mentioned 306 above. 308 4. NB-IoT worst case performance 310 Here we consider the worst case scenario for NB-IoT. This scenario 311 refers to the case with high coupling loss and the UE being the least 312 capable. The link characteristics are listed assuming such 313 conditions. 315 o 180 kHz bandwidth 317 o Uplink transmission 319 * 1 Data Radio Bearer (DRB) 321 * Single-tone transmission, 3.75 kHz spacing 323 o 164 dB maximum coupling loss (see Table 1 325 +--------------------------------------------------------+----------+ 326 | Numerology | 3.75 kHz | 327 +--------------------------------------------------------+----------+ 328 | (1) Transmit power (dBm) | 23.0 | 329 | (2) Thermal noise density (dBm/Hz) | -174 | 330 | (3) Receiver noise figure (dB) | 3 | 331 | (4) Occupied channel bandwidth (Hz) | 3750 | 332 | (5) Effective noise power = (2) + (3) + 10*log ((4)) | -135.3 | 333 | (dBm) | | 334 | (6) Required SINR (dB) | -5.7 | 335 | (7) Receiver sensitivity = (5) + (6) (dBm) | -141.0 | 336 | (8) Max coupling loss = (1) - (7) (dB) | 164.0 | 337 +--------------------------------------------------------+----------+ 339 Table 1: NB-IoT Link Budget 341 Under such conditions, NB-IoT may achieve data rate of roughly 200 342 bps. 344 For downlink with 164 dB coupling loss, NB-IoT may achieve higher 345 data rates, depending on the deployment mode. Stand-alone operation 346 may achieve the highest data rates, up to few kbps, while in-band and 347 guard-band operations may reach several hundreds of bps. NB-IoT may 348 even operate with higher maximum coupling loss than 170 dB with very 349 low bit rates. 351 5. IANA Considerations 353 This memo includes no request to IANA. 355 6. Security Considerations 357 3GPP access security is specified in [TGPP33203]. 359 7. Informative References 361 [TGPP23720] 362 3GPP, "TR 23.720 v13.0.0 - Study on architecture 363 enhancements for Cellular Internet of Things", 2016. 365 [TGPP33203] 366 3GPP, "TS 33.203 v13.1.0 - 3G security; Access security 367 for IP-based services", 2016. 369 [TGPP36201] 370 3GPP, "TS 36.201 v13.2.0 - Evolved Universal Terrestrial 371 Radio Access (E-UTRA); LTE physical layer; General 372 description", 2016. 374 [TGPP36300] 375 3GPP, "TS 36.300 v13.4.0 (Available soon) - Evolved 376 Universal Terrestrial Radio Access (E-UTRA) and Evolved 377 Universal Terrestrial Radio Access Network (E-UTRAN); 378 Overall description; Stage 2", 2016. 380 [TGPP36321] 381 3GPP, "TS 36.321 v13.2.0 (Available soon) - Evolved 382 Universal Terrestrial Radio Access (E-UTRA); Medium Access 383 Control (MAC) protocol specification", 2016. 385 [TGPP36322] 386 3GPP, "TS 36.322 v13.2.0 (Available soon) - Evolved 387 Universal Terrestrial Radio Access (E-UTRA); Radio Link 388 Control (RLC) protocol specification", 2016. 390 [TGPP36323] 391 3GPP, "TS 36.323 v13.2.0 (Available soon) - Evolved 392 Universal Terrestrial Radio Access (E-UTRA); Packet Data 393 Convergence Protocol (PDCP) specification (Not yet 394 available)", 2016. 396 [TGPP36331] 397 3GPP, "TS 36.331 v13.2.0 (Available soon) - Evolved 398 Universal Terrestrial Radio Access (E-UTRA); Radio 399 Resource Control (RRC); Protocol specification", 2016. 401 Author's Address 403 Antti Ratilainen 404 Ericsson 405 Hirsalantie 11 406 Jorvas 02420 407 Finland 409 Email: antti.ratilainen@ericsson.com