Long Range Wireless IoT Technologies: Low Power Wide Area Network (LPWAN) vs Cellular ______ Anne-Lena Kampen Trondheim 18 th of May 2017
Outline • Introduction • Long Range Wireless IoT Technologies; characteristics • Cellular approaches • Proprietary approaches • Standards • Comparing cellular versus LPWAN • Research challenges • Conclusion 2
Introduction • Internet of Things – Internet: Worldwide network – Things: Machines, parts of machines, smart meters, sensors.. – Worldwide network of interconnected objects • IoT is not a single market • There are may different usage with different tradeoff in terms of: – Delay – Range – Throughput – Reliability 3
IoT is made up of a loose collection of different, purpose-built networks L. Atzori, A. Iera, and G. Morabito, "The internet of things: A survey," Computer networks, vol. 54, no. 15, pp. 2787-2805, 2010. 4
Introduction Long Range Wireless IoT • Low Power Wide Area Networks ( LPWAN) is part of the solution for IoT. • LPWAN is not a single technology but a collection aimed at different markets • Cellular adapts to IoT market with different tradeoff • The share of LPWAN connections (all M2M) will grow [1] – 58 million in 2016 – 1 billion by 2021 [1] “Global Mobile Data Traffic Forecast Update, 2016 – 2021 White Paper”, Cisco Visual Networking Index, Cisco mars 2017, Available, http://www.cisco.com/c/en/us/solutions/collateral/service-provider/visual-networking-index-vni/mobile-white-paper-c11-520862.html 5
Introduction Long Range Wireless IoT ETSI defines Low Throughput Network (LTN) [1] • Long range; 10-12 km (city) 40-60 km (countryside) • Low throughput; few bytes per day, week or month • Ultra low power on the end points • Low cost of operations • Low cost of ownership. [1] “Low throughput networks (ltn); use cases for low throughput networks ,” ETSI GS LTN 001 V1.1.1, September 2014. [Online ]. Available: http://www.etsi.org/deliver/etsi gs/LTN/001 099/001/01.01. 01 60/gs LTN001v010101p.pdf 6
Long Range Wireless IoT Technologies; Network layer • Long range transmission compared to multihop • Advantage – Multihop have unequal and unpredictable energy consumption • Management traffic, forwarding – Multihop require dense and expensive deployment of infrastructure • Disadvantage – Long range have lower data rate 7
Long Range Wireless IoT Technologies; Medium access layer • The simple Aloha protocol used in several technologies – Low delay – However, high Collison probability • Carrier sense protocols (CSMA) – Reduces collisions – However, in LPWAN a high number of nodes may be ‘hidden nodes’ • Request to send/ Clear to send (RTS/CTS) – Prevents collisions – Less effective for short data packets – Added communication overhead • Time division multiple access (TDMA) – Reduces collisions – Increase overhead – Advanced protocols requiring tight synchronization is challenging due to cheep Time-frequency resources; figure from[1] end device oscillators [1] A. Laya, L. Alonso, and J. Alonso Zarate, "Is the Random Access Channel of LTE and LTE-A Suitable for M2M Communications? A Survey of Alternatives," IEEE Communications Surveys and Tutorials, vol. 16, no. 1, pp. 4-16, 2014. 8
Duty cycle Active / sleep - duty cycling of the end-devices is used to reduce energy consumption – Downlink only after uplink: End-devise stays awake a limited time after transmission – Scheduled downlink: A node periodically wake up There are restrictions limiting the duty cycle for some ISM bands – 0.1-10 % of the time 9
Frequency • Mainly sub-GHz ISM band – Some use 2.4GHz – Free of charge – Lower frequency signals experience less attenuation and multipath fading – However, Cross-technology interference • Cellular – Licensed frequencies 10
Modulation Receivers sensitivity is improved by slower modulation rate (slower data rate) Narrowband: (<25kHz) Ultra narrow band (UNB) (100Hz) • Share the overall spectrum efficiently • Efficient share of spectrum • • However, very low data rate Reduced noise • Increased duty time • However, low data rate Spread spectrum techniques • Several users • Harder to detect by an eavesdropper • More resilient to interference • However, require larger BW 1 11 1
Cellular • 3GPP: 3rd Generation Partnership Project (3GPP) [1] • The united telecommunications standard development organization • Produce Reports and Specifications that define 3GPP technologies: – Cellular network technologies [1] http://www.3gpp.org/ 12
Cellular LTE • New device category have the following reduced capabilities [1] – One receive (Rx), one receiver chain. – Reduced peak data rates;1 mbps in downlink and uplink. – Optional half-duplex FDD (Frequency Division Duplex) operation • LTE modulation [2] : • Downlink OFDMA (Orthogonal Frequency Division Multiple Access) – High peak-to-average • Uplink SC-FDMA (Single carrier) – Low peak-to-average [1] R. Ratasuk, A. Prasad, Z. Li, A. Ghosh, and M. A. Uusitalo, "Recent advancements in M2M communications in 4G networks and evolution towards 5G," in Intelligence in Next Generation Networks (ICIN), 2015 18th International Conference on , 2015, pp. 52-57: IEEE. [2] 3GPP online information: http://www.3gpp.org/technologies/keywords-acronyms/98-lte 13
Cellular NB-IoT • Narrowband IoT (NB-IoT) – (3GPP Rel.13) [1] • NB-IoT is designed to be tightly integrated with LTE • Three different type of deployment • BW: 180 kHz Figure from [2] • Uplink: – (SC- FDMA) (Single-carrier Frequency Division Multiple Access) – 170 kbps • Downlink: – Orthogonal FDMA (OFDMA) in downlink, – 250 kbps [2] [1] “LTE: Evolved Universal Terrestial Radio Access (E-UTRA); Mediaum Access Control (MAC) protocol specification (3GPP TS 36.321 version 13.2.1 Release 13), available, http://www.etsi.org/deliver/etsi_ts/136300_136399/136321/13.02.00_60/ts_136321v130200p.pdf [2]“LTE evolution for IoT connectivity” Nokia white paper”, Nokia 2017. Available http://resources.alcatel -ucent.com/asset/200178 14
Cellular – 5G Wireless • First standard is expected in 2020 [1] High-frequency 3 ∼ 300 GHz • Data rate 1 ∼ 10 Gbps • Figure from [1] • Support IoT (M2M) • To support massive IoT connections: – Heterogeneous Networks (HetNets), small cells having low transmission power • MAC layer protocols – CSMA; adapted for directional antennas [2], – TDMA; spatial reuse enables concurrent transmission [1]M. Agiwal, A. Roy, and N. Saxena, "Next generation 5G wireless networks: A comprehensive survey," IEEE Communications Surveys & Tutorials, vol. 18, no. 3, pp. 1617-1655, 2016. [2] M. X. Gong, D. Akhmetov, R. Want, and S. Mao, "Multi-user operation in mmwave wireless networks," in Communications (ICC), 2011 15 IEEE International Conference on , 2011, pp. 1-6: IEEE.
Comparing cellular - summary LTE NB-IoT 5G Link budget 141dB 164dB Output power 23dBm 23dBm BW 20Mhz 180kHz Data rate 1mbps UL & DL 250 kbps UL 10Gbps 170 kbps DL Power saving mode X X X 16
Proprietary - LPWAN LoRa • Sub-GHz ISM band[1, 2] • Phy layer, proprietary – CSS (Chirp Spread Spectrum) Figure from [1] – The data rate ranges from 300 bps to 37.5 kbps – Link budget 154 dB [3 ] LoRaWAN, layer above physical is defined by LoRa TM Alliance – LoRaWAN TM • specification – Unslotted Aloha – Topology: star-of-star topology • End device does not associate with a certain gateway, only to the backhaul NetworkServer – Three different classes of end-devices [1] M. Centenaro, L. Vangelista, A. Zanella, and M. Zorzi, "Long-range communications in unlicensed bands: The rising stars in the IoT and smart city scenarios," IEEE Wireless Communications, vol. 23, no. 5, pp. 60-67, 2016. [2] K. Mikhaylov, J. Petäjäjärvi, and T. Haenninen, "Analysis of capacity and scalability of the LoRa low power wide area network technology," in European Wireless 2016; 22th European Wireless Conference; Proceedings of , 2016, pp. 1-6: VDE. 17 [3] R. S. Sinha, Y. Wei, and S.-H. Hwang, "A survey on LPWA technology: LoRa and NB-IoT," ICT Express, 2017
Proprietary - LPWAN SigFox • SIGFOX one of the first LPWAN technologies proposed for IoT, founded in 2009 [1,2] • Global connectivity to a single core • Link budget 155dB • Sub-GHz ISM band carrier – Ultra narrow band (UNB) – 100Hz – Data rate 100 bps ! • Aloha based access protocol [3] • Optimized for uplink transmissions – Retransmit default 3 times [1]G. Margelis, R. Piechocki, D. Kaleshi, and P. Thomas, "Low throughput networks for the IoT: Lessons learned from industrial implementations," in Internet of Things (WF-IoT), 2015 IEEE 2nd World Forum on , 2015, pp. 181-186: IEEE. [2]: “LPWAN Overview : draft -ietf-LPWAN-overview- 01”, IETF, February 2017, Available, https://datatracker.ietf.org/doc/draft -ietf- lpwan-overview/01/ 18 [3] A. Laya, C. Kalalas, F. Vazquez-Gallego, L. Alonso, and J. Alonso-Zarate, "Goodbye, aloha!," IEEE access, vol. 4, pp. 2029-2044, 2016.
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