Panoramica sui segnali radio in ambito IoT (cellular IoT, LPWAN) Daniela Valente ISCOM

Transcription

1 Panoramica sui segnali radio in ambito IoT (cellular IoT, LPWAN) Daniela Valente ISCOM

2 Outline Overview Cellular IoT LPWA (Low Power Wide Area) Conclusions

3 Machine-type communications Different solutions for different Machine to Machine (M2M) applications (is a form of data communication which involves one or more entities that do not necessarily need human interaction) The 5G is categorized (licensed spectrum) extreme mobile broadband (xmbb) massive machine-type communications (mmtc) ultra-reliable machine-type communications (umtc) mmtc enables 5G services to lots of devices with energy efficiency LPWA (unlicensed spectrum) is a generic term for a group of technologies that enable wide area communications at lower cost points and better power consumption (2013)

4 State-of-the-art of IoT solutions Unlicensed spectrum tecnologies have advantages in terms of battery lifetime, capacity, and cost short-range radio connectivity (e.g., Bluetooth and ZigBee) are not suitable for scenarios that require long range Licensed spectrum tecnologies offer benefits in terms of QoS, latency, reliability, and range cellular technology can provide large coverage, but they consume power

5 Cellular IoT limits to overcome The RACH (random access channel) procedure has been identified by 3GPP as a challenging task for M2M communications due to signaling and traffic load caused by access to the same base station simultaneously Effects on energy consumption and computational effort, which are generally critical for MTD applications Channel access requests by end-devices will not properly scale in the presence of massive access attempts of MTDs sharp degradation of the quality offered to conventional services because of long access delay and high access failure rate of course, M2M services are also affected by these impairments, though the impact may be less significant with respect to conventional services 3GPP (Third Generation Partnership Project) Release 13 (2016)

6 Radio Interfaces/tecnologies initial comparison LoRa (<1 GHz) uses unlicensed spectrum and is an asynchronous protocol (ALOHA-based protocol) LoRaWAN ecosystem is flexible duty cycle regulations NB-IoT (700 MHz, 800 MHz, 900 MHz, 1800 MHz, 2.1 GHz, 2.6 GHz) uses a licensed spectrum and its time slotted synchronous protocol is optimal for QoS (the device consumes additional battery energy) advantage of low latency deployment of NB-IoT is limited to 4G/LTE base stations. Thus, it is not suitable for rural or suburban regions that do not have 4G coverage

7 IoT factors quality of service (QoS) latency battery life coverage range deployment model and cost Cost, battery life, coverage (LoRA) IoT industries Logistics tracking, Asset tracking, Smart agriculture, Healthcare, Range, diversity, latency, QoS (NB-IoT) IoT public Smart metering, Alarms and events, Smart garbage bins,

8 CELLULAR IoT (C-IoT) toward 5G EC-GSM (extended coverage GSM) designed to enhance GSM LTE-eMTC (enhanced MTC) will enhance LTE NB-IoT (narrow band IoT) can be considered a new track, with good co-existence performance Release 8 was the first version of the LTE standard decicated to Machine Type Communications

9 Deployment Models of C-IoT Mobile Network Operator (MNO) perspective fully independent deployment (standalone deployment) by pre-empting some of the resources of existing carriers (in-band deployment) by being deployed on the side of an existing carrier (guard-band deployment) EC-GSM-IoT is considered to be deployed in standalone and in band modes LTE-eMTC is considered to be deployed in band mode NB-IoT encompasses all the three modes

10 C-IoT The coexistence (with existing GSM, UMTS and LTE systems and the hardware used for those technologies) is realized by specifying the time and frequency resources used from the existing standards Physical Resource Block

11 Extended Coverage GSM (EC-GSM) EC-GSM-IoT is an evolution of the existing GSM air interface with a channel bandwidth of 200 khz (for a total system bandwidth of 2.4MHz) changes to enhance requirements in terms of high capacity, long range, and low energy EC-GSM-IoT is part of the GSM system for carrying IoT traffic BS and UE spectrum masks are the same as a normal GSM systems deployed in a standalone mode and/or in-band mode in the 900 and 1800 MHz bands uses the same frequency planning as GSM, e.g either with fixed frequency reuse or with frequency hopping Some of the GSM network s radio resource (time slots) are dynamically allocated to IoT. The number of carriers/slots for EC-GSM-IoT per BS depends on the number of devices and M2M traffic in the service area EC-GSM-IoT is covered by the ETSI EN (BS) and the ETSI EN (UE).

12 Extended Coverage GSM (EC-GSM) Low battery consumption (UE) (~10 years - 5W/h on average) Power Saving Mode (PSM) and edrx (Extended Discontinuous Reception, up to 52 min.) are also supported on EC-GSM devices, to increase energy efficiency. In addition, EC-GSM supports a relaxed idle mode behavior, where no cell measurements are performed while in a Power Saving State the coverage of GSM is extended with two classes of devices: 33 dbm power class (MCL=164 db) and 23 dbm power class (MCL=154 db) throughput rate varies from 350 bps to 70 kbps (depending on the coverage class) in DL (mod GMSK) and up to 240 kbps in UL (mod 8PSK) 50,000 devices can be supported per cell higher protection of the information compared to GSM/EDGE a new packet control channel format has been designed to limit the amount of required control signalling

13 LTE-enhanced MTC 6 contiguous resource blocks anywhere in a LTE channel for M2M applications each resource block is 180 khz, 6x180 =1080 khz Since LTE-MTC/eMTC is part of LTE system, the BS and UE spectrum masks are the same as a normal LTE system LTE-MTC/eMTC can use all resource blocks available in the LTE channel Total occupied bandwidth LTE resource block 6 LTE-(e)MTC RB

14 LTE-eMTC (Cat. M1) Low battery consumption (UE) (~10 years - 5W/h on average) PSM (Power Save Mode) and edrx (Extended Discontinuous Reception) Connected Mode (C-eDRX): sleeping period (device cannot be reached) is 5.12s and 10.24s Idle Mode (I-eDRX): sleeping period is a up to 44min cost reduction of user devices compared to GPRS/GSM more extened range than GSM (MCL>155.7 db) data-rate up to 1Mbps according to cell dimension implementation in any LTE band possibility to implement both FDD / TDD and half duplex (HD) techniques useful signal bandwidth is 1.08 MHz (1.4 MHz with guard band) transmission power of 20 dbm

15 NB-IoT Narrowband Internt of Things From LTE with added simplifications reduced bandwidth requirements (using 180 khz of bandwidth, in comparison to MHz used by LTE) a modified random access scheme - resulting in a fast development time enhanced coverage and reduced power consumption in exchange for relaxed latency, a lower data rate, and lower spectrum efficiency a modified acquisition process (different cell search process to LTE) designed for infrequent and short messages between the UE and the network in NB-IoT all traffic is assumed to be delay tolerant it is assumed that the UE can exchange the messages while being served from one cell (a handover procedure is not needed) only cell reselection in the idle state is supported, which is even restricted to be within the NB-IoT technology

16 NB-IoT Channel bandwidth is 200 khz and the transmission bandwidth 180 khz (leaving 10 khz guard bands on each side from channel edges), equivalent to one LTE resource block NB-IoT uses in both downlink and uplink a fixed total carrier bandwidth of 180 khz so that it can utilise LTE resource blocks within a normal LTE carrier or unused blocks in the guard-band of an LTE carrier but it is not integrated dynamically into an LTE system. In the downlink (OFDMA) 12 sub-carriers with a sub-carrier spacing of 15 khz are used for all modes of operation (standalone, in-band, guard-band) In the uplink (SC-FDMA), multi-tone and single-tone transmissions are supported. Single tone transmission supports two configurations (sub-carrier spacing of 3.75 khz with 2 ms slot duration or 15 khz with 0.5 ms slot duration) Multi-tone transmission (with 3, 6 or 12 tones) uses 15 khz sub-carrier spacing, 0.5 ms slot and 1 ms frame duration as LTE NB-IoT UE only needs to support half duplex operations.

17 LTE-NB-IoT (Cat. NB1) two power transmission classes: class 3 (23 dbm - max output power) class 5 (20 dbm - max output power) covering 52k devices per channel per cell device lifetime of over ten years, on a battery capacity of 5W/h like LTE, uses discontinuous reception (DRX) to further increasing energy saving LTE-based IoT solutions (including NB-IoT) will have a SIM-like approach

18 NB-IoT For non-ip data, traffic will be transferred to the newly defined node, service capability exposure function (SCEF), which can deliver machine type data over the control plane and provide an abstract interface for the services CIoT = cellular internet of things EPS = evolved packet system MME = Mobility Management Entity SGW = Serving Gateway PGW = Packet Data Network Gateway SCEF = Service Capability Exposure Function The principle of control and shared channels also applies for NB-IoT, defining the Narrowband Physical Downlink Control Channel (NPDCCH) and the Narrowband Physical Downlink Shared Channel (NPDSCH)

19 LTE-NB-IoT (Cat. NB1) in-band deployed within an LTE wideband system - 1 or more of the LTE Physical Resource Blocks (180kHz). The transmit power at the base station is shared between wideband LTE and NB-IoT, and both technologies can be supported using the same base station hardware, without compromising the performance of either the number of carriers for NB-IoT per BS depends on the number of devices and M2M traffic in the service area According to 3GPP technical specifications TS , the NB-IoT PRB power dynamic range (or NB-IoT power boosting) is the difference between the power of NB-IoT carrier and the average power over all carriers (both LTE PRBs and NB-IoT PRB)

20 LTE-NB-IoT (Cat. NB1) guard-band in the guard band of an LTE channel. Sharing the same power amplifier as LTE channel, and so shares transmission power NB-IoT RB band edge is placed at least 200 khz away from the LTE channel edge. The use of guard band NB- IoT within CEPT is foreseen only for LTE channel bandwidths of 10 MHz or higher does not refer to any potential guard band between bands of operation (for example the frequency separation MHz between NB-IoT in MHz and broadcasting services below 694 MHz), but to the spectrum on the side of an LTE channel, where the emission masks rolls out in order to meet the out of block requirement for guard-band operation with several NB-IoT carriers, the NB-IoT carrier that can be power boosted should be placed adjacent to the LTE signal edge as close as possible (i.e., away from edge of the LTE transmission channel)

21 LTE-NB-IoT (Cat. NB1) standalone deployed in a standalone 200 khz of spectrum. All transmission power at the base station is used for NB-IoT, increasing coverage. Typical usage of this mode would be as replacement of GSM carriers frequency separation of 200 khz between NB-IoT carrier and channel edge of adjacent services/systems for a standalone NB-IoT carrier, the spacing between the NB-IoT centre frequency and the centre frequency of an adjacent GSM or UMTS carrier should be at least 0.3 MHz and 2.8 MHz respectively as a result, frequency re-planning in the deployment area is required in order to allow a tighter frequency reuse

22 Parametri emtc NB-IoT EC-GSM-IoT Downlink peak-rate Fino a 1 Mbps Fino a 20 kbps 350 bps 70 kbps (GMSK) Uplink peak-rate Fino a 1 Mbps Fino a 60 kbps Fino a 250 kbps (8PSK) n. antenne Banda ricevitore (UE) Potenza trasmettitore (UE) HD FDD/TDD HD FDD HD FDD 20 dbm 20 dbm 20 dbm MCL > db 164 db 154 db (23 dbm) Modalità per Power saving In-band LTE In-band LTE Banda di Guardia LTE Stand-alone Complessità 20% <15% ND N. apparati per cella In-band GSM Disponibilità 2017/1H /1H18 Entro il 2017

23 LPWA (Low Power Wide Area) LPWA (Low Power Wide Area) technologies instead of mesh-based protocol would require less repeaters less control plane communication simpler routing protocols Focus on energy efficiency scalability coverage These technologies typically operate in the unlicensed sub-1ghz Industrial, Scientific and Medical (ISM) band frequencies used by LPWA protocols can penetrate buildings better than higher frequency protocols such as Wi-Fi, enabling a much simpler deployment of sensors throughout even large office blocks

24 LoRa (Long Range) LoRa (Long Range) is a physical layer technology developed by Semtech spread spectrum modulation, better resilience against interference a form of Chirp Spread Spectrum (CSS) with integrated Forward Error Correction (FEC) the use of higher spread factors (chips used per symbol) leads to a higher energy usage per packet trades data rate for sensitivity within a fixed channel bandwidth LoRa communicates over the license free sub-1ghz ISM bands In Europe, 433MHz and 868MHz are available, with 868MHz being most commonly used

25 LoRa LoRa physical layer technology is proprietary but the upper layers of the network stack are open for development The most well supported upper layer protocol for LoRa is LoRaWAN, which is open and managed by the LoRa Alliance, a non-profit The LoRa Alliance is a non-profit organization formally launched in 2015, among its members there are world-class companies such as Cisco, IBM, Semtech

26 LoRaWAN (LoRa Wide Area Network) secure, mobile, GPS-free bidirectional communication payloads ranging from 19 to 250 bytes (overhead per packet is 12 bytes) LoRa range depends on the link budget bandwidth, coding scheme, transmission power, carrier frequency, and spread factor On a LoRa device the bandwidth can be set from 7.8 khz up to 500 khz, though only 125 khz, 250 khz, and 500 khz are typically used According to research experiments LoRa can achieve a range of up to 5km in urban environments up to 30km range in Line-of-Sight measurements and a range of up to 8km in rural environments The spread factor is the ratio between symbol rate and chip rate. Six different spread factors are available (between 7 and 12) Increasing the spread factor makes the signal more robust to noise, but decreases the data rate

27 LoRaWAN User device can communicate with the gateway using a simple ALOHA based protocol The performance of a LoRaWAN network is limited by the strict access limitations imposed by the regional regulations the limitations of the simple ALOHA-based medium access control, which is not suited for dense and busy networks nodes (user devices), are not necessarily associated with a specific gateway data transmitted by a node is received by multiple gateways which then send packets to the network server through any backhaul network (mobile, ethernet, satellite, WiFi, etc.) Intelligence and complexity of the network are concentrated in the network server: manages packages, eliminates redundant ones checks connections security checks transmission integrity transmits response messages through the best gateway, etc

28 LoRaWAN If a node is moving, no handover procedure from gateway to gateway is required Nodes of a LoRaWAN network are asynchronous and communicate when they have data to transmit, either after a specific event or at predefined times. This modality is typical of Aloha protocols the system does not need to be synchronized with the network. LoRa devices are divided into three classes A, B and C

29 LoRaWAN devices Bidirectional transmission About security, LoRa devices have two levels of security: network level guarantees the authenticity of the transmitting nodes application level ensures that mobile operators does not have access to data transmitted by users LoRaWAN defines 3 types of devices: Class A, which supports basic device-initiated communication (greater energy saving) after each uplink communication there are two short time windows in which signals can be received from the gateway Class B, which extends Class A to add the ability for the network to ping devices (the device is given receive windows at scheduled times) have additional time windows for receiving messages from the gateway Class C, which is similar to Class A but in continuous receive mode when not transmitting they have the highest number of slots for receiving messages from the gateway. (Practically they are always on and this causes a high energy consumption)

30 LoRa Caratteristiche operative Banda di frequenza Canali 10 Larghezza di banda di un canale Modulazione Potenza in trasmissione (uplink/downlink) Data-rate MCL Area di copertura Nodi gestibili Numero di messaggi al giorno Durata batteria da 2000 mah Efficienza energetica Coesistenza Immunita Sicurezza Mobilità/localizzazione Prestazioni di LoRa MHz (in Europa) 125/500 KHz Spread spectrum chirp +20 dbm (max) 290 bps 50 Kbps 154 db 2-5 Km (area urbana) 15 Km (area rurale) milioni Illimitati 105 mesi elevata Si elevata Si Si

31 Riferimenti ECC Report 266, The suitability of the current ECC regulatory framework for the usage of Wideband and Narrowband M2M in the frequency bands 700 MHz, 800 MHz, 900 MHz, 1800 MHz, 2.1 GHz and 2.6 GHz, June 2017 R. S. Sinha, Y. Wei, S.-H. Hwang, A survey on LPWA technology: LoRa and NB-IoT, ICT Express. 3, 2017 J. Finnegan, S. Brown, A Comparative Survey of LPWA Networking, Feb Narrowband Internet of Things, Whitepaper Rohde & Schwarz

32 Riferimenti ETSI EN V2.1.1 ( ), White Space Devices (WSD); Wireless Access Systems operating in the 470 MHz to 790 MHz TV broadcast band; Harmonised Standard covering the essential requirements ETSI TS V ( ), LTE; Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment (UE) radio transmission and reception (3GPP TS version Release 14) ETSI TS V ( ), LTE; Evolved Universal Terrestrial Radio Access (E-UTRA); Base Station (BS) radio transmission and reception (3GPP TS version Release 14) ETSI TS V ( ), LTE; Evolved Universal Terrestrial Radio Access (E-UTRA); Base Station (BS) conformance testing (3GPP TS version Release 14) ETSI TS V ( ), LTE; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation (3GPP TS version Release 14)