Long Range Wireless IoT Technologies - NTNU · Long Range Wireless IoT Technologies; Medium access layer • The simple Aloha protocol used in several technologies – Low delay –

Long Range Wireless IoT

Technologies:

Low Power Wide Area Network

(LPWAN) vs Cellular

______

Anne-Lena Kampen

Trondheim 18th of May 2017

2

Outline

• Introduction

• Long Range Wireless IoT Technologies; characteristics

• Cellular approaches

• Proprietary approaches

• Standards

• Comparing cellular versus LPWAN

• Research challenges

• Conclusion

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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

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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.

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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

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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

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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

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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 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.

Time-frequency resources; figure from[1]

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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

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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

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Modulation

Receivers sensitivity is improved by slower modulation rate (slower data rate)

Narrowband: (<25kHz)

• Share the overall spectrum efficiently

• Reduced noise

• However, low data rate

Spread spectrum techniques

• Several users

• Harder to detect by an eavesdropper

• More resilient to interference

• However, require larger BW

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Ultra narrow band (UNB) (100Hz)

• Efficient share of spectrum

• However, very low data rate

• Increased duty time

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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/

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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

http://www.3gpp.org/technologies/keywords-acronyms/98-lte

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Cellular NB-IoT

• Narrowband IoT (NB-IoT)– (3GPP Rel.13) [1]

• NB-IoT is designed to be tightlyintegrated with LTE

• Three different type of deployment

• BW: 180 kHz

• Uplink: – (SC- FDMA) (Single-carrier Frequency Division Multiple Access)

– 170 kbps

• Downlink: – Orthogonal FDMA (OFDMA) in downlink,

– 250 kbps [2]

Figure from [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

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Cellular – 5G Wireless

• First standard is expected in 2020 [1]

• High-frequency 3∼300 GHz

• Data rate 1 ∼ 10 Gbps

• 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 IEEE International Conference on, 2011, pp. 1-6: IEEE.

Figure from [1]

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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 UL170 kbps DL

10Gbps

Power saving mode X X X

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Proprietary - LPWAN LoRa

• Sub-GHz ISM band[1, 2]

• Phy layer, proprietary – CSS (Chirp Spread Spectrum)

– The data rate ranges from 300 bps to 37.5 kbps

– Link budget 154 dB [3 ]

• LoRaWAN, layer above physical is defined by LoRaTM Alliance – LoRaWANTM

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.[3] R. S. Sinha, Y. Wei, and S.-H. Hwang, "A survey on LPWA technology: LoRa and NB-IoT," ICT Express, 2017

Figure from [1]

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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/[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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Proprietary - LPWAN Ingenu (former OnRamp Wireless)

• Star network topology [1]

• Link budget 168dB

• 78kbps UL, 19.5 kbps DL

• Uplink: Patented Random Phase Multiple Access Direct Sequence Spread Spectrum (RPMADSSS) or just RPMA

• Downlink: CDMA

• 2.4 GHz ISM band – More relaxed regulations on the spectrum use across regions

• Deployed in USA- 22 cities.

[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.

CDMA RPMA

[Low throughput Network in the IoT Lessons learned]

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Standards IEEE 802.15.4k

• Topology : Star

• Sub-GHz and 2.4GHz ISM band

• Modulation DSSS and FSK

• Link budget up to 120dB

• Coverage 5-20 km

• Data rate 300 bps – 1.2 kb/s

• MAC:

• CSMA/CA or Aloha with or without PCA (Priority channel access) [1]– PCA: Introduce PCA slot in which only high priority message can be transmitted

[1] B. G. Gebremedhin, J. Haapola, and J. Iinatti, "Performance Evaluation of IEEE 802.15. 4k Priority Channel Access with DSSS PHY," in European Wireless 2015; 21th European Wireless Conference; Proceedings of, 2015, pp. 1-6: VDE.

Figure from[1]

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Standards 802.11ah

• Single hop

• Range 0.1-1Km

• Supports 800 nodes [1]

• Frequency band Sub-1GHz [2]

• Data rate: 0.15–7.8 Mb/s

• Modulation: OFDM

• MAC:– Divide the stations into Traffic Indication Map, TIM groups

– Different scheduling to different group

– Contend for channel access only among group members- CSMA

[1] A. Laya, C. Kalalas, F. Vazquez-Gallego, L. Alonso, and J. Alonso-Zarate, "Goodbye, aloha!," IEEE access, vol. 4, pp. 2029-2044, 2016.[2] T. Adame, A. Bel, B. Bellalta, J. Barcelo, and M. Oliver, "IEEE 802.11 AH: the WiFi approach for M2M communications," IEEE Wireless Communications, vol. 21, no. 6, pp. 144-152, 2014.

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Comparing LPWAN - summaryLoRaWAN SigFox Ingenu IEEE 802.15.4 IEEE 802.11 ah

Link budget 154dB 155dB 168dB 120dB

MAC Unslotted Aloha Unslotted Aloha Slotted Aloha-like CSMA, Aloha/PCA

CSMA

Data rate 300bps-37.5kbps 100 bps 78kB(UL)19.Kbps (DL)

300bps- 1.2 kbps 0.15-7.8mbps

Coverage rangekm

Rural: 10–15Urban: 3–5

Rural: 30–50Urban: 3–10

Urban: 15 5-20 km 0.1-1Km

Aloha approach in DSSS channels is validated in [1]:IEEE802.15k prototype radio, urban environments and 5 end-devices. The preamble of each packets is properly detected and distinguishable.

Calculations [2] LoRaWAN, suburban: Can serve up to 7 million units. However, less than 10% of the end-devices can reside at a distance over 5km.

[1] X. Xiong, K. Zheng, R. Xu, W. Xiang, and P. Chatzimisios, "Low power wide area machine-to-machine networks: Key techniques and prototype," IEEE Communications Magazine, vol. 53, no. 9, pp. 64-71, 2015.[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.

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Comparing Technologies

LoRaWAN SigFox Ingenu IEEE 802.15.4 IEEE 802.11 ah

Link budget 154dB 155dB 168dB 120dB

Data rate 300bps-37.5kbps 100 bps 78kB(UL)19.Kbps (DL)

300bps- 1.2 kbps 0.15-7.8mbps

LTE NB-IoT 5G


Data rate 1mbps UL & DL 250 kbps UL170 kbps DL

10Gbps

Cellular

LPWAN

NB-IoT SigFox

BW 180kHz 100Hz


Data rate 250 kbps UL, 170 kbps DL 100 bps

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Comparing technologies

Cellular

• Massive infrastructure (Worldwide?) -

Continued investment

– Global standard infrastructure

• Licensed spectrum - Cost

– Time and frequency resources are to be

shared between M2M and H2H

– Massive amount of M2M devices

increase signaling and control traffic

– Different communication characteristics

• QoS can be guaranteed

• Secure communication (SIM card)

• The cost and complexity is high

• Concurrent transmit messages form a large

number of M2M devices can impact the

operation of the whole mobile network

LPWAN

• Some infrastructure

– Several LPWAN technologies, no

interoperability

• Unlicensed spectrum, free of charge

– Every country has different rules about

using the sub-GHz spectrum.

– ISM employs different SubGHz frequency

band: Europe (868 MHz), U.S. (915 MHz)

– Cross-technology interference

• QoS requirements difficult to guarantee

• Some solutions have poor security (ex. SigFox)

• Stripped complexity to reduce cost.

• Improving LPWAN scalability with increased

base-station density

– Interference

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Standardization

• ETSI [1]:

• Standardize low data rate LPWAN– Low Throughput Networks (LTN); Use Cases for Low Throughput Networks

– Low Throughput Networks (LTN); Functional Architecture

– Low Throughput Networks (LTN); Protocols and Interfaces

• IETF [2]:– The range of several kilometers and a long battery lifetime, has a price

• The application is often wired to the layer 2 frame format

– However, the systems should be able to interoperate

– The IETF contribute by providing IPv6 connectivity• Propose technologies to secure the operations and

• Manage the devices and their gateways

[1]“Low throughput networks (ltn); use cases for low throughput networks,”; “Low throughput networks (ltn); functional architecture,” ; “Low throughput networks (ltn);protocols and interfaces,” 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[2] LPWAN Work Group – about, available, https://datatracker.ietf.org/wg/lpwan/about/

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Research challenges - I

Scalability

• LPWAN specific – Challenge: Cross-technology interference

– Authority can propose rules for spectrum sharing

– Improve channel access techniques

• Cellular specific – Challenge: Resource sharing H2H vs M2M

– Challenge for M2M traffic: Low ratio between payload and control information

– Improve channel access techniques

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Research challenges - II

Scalability [1,2]

• Use of multiple base-stations to improve availability – Challenge: Interference, management and low spectrum utilization

– Effective spectrum sharing; cognitive radio

– Transmission schedule

• MAC layer protocols– Challenge: congestion, collisions, BW-utilization

– Appropriate backoff parameter settings

– Slotted solutions require some signaling overhead

• Cellular networks are designed by network operators

[1] U. Raza, P. Kulkarni, and M. Sooriyabandara, "Low Power Wide Area Networks: An Overview," IEEE Communications Surveys & Tutorials, vol. PP, no. 99, pp. 1-1, 2017.[2] F. Ghavimi and H.-H. Chen, "M2M communications in 3GPP LTE/LTE-A networks: architectures, service requirements, challenges, and applications," IEEE Communications Surveys & Tutorials, vol. 17, no. 2, pp. 525-549, 2015.

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Research challenges - IIIScalability – suggested solutions MAC layer:

• Contention-based access for LTE:

• Example of suggested improvement [1]:

– Include data into the contention process

– Modify the Access Class Barring mechanism

– Split the available preambles into H2H and M2M

• Distributed Queue (DQ) based on two ques [2]:

– Colliding data enters Contention Resolution Queue

– Success data enters Data Transmission Queue

– Implement DQ in the RA procedure of the LTE standard.

• Simulation: Include RA in LTE

• Blocking probability becomes unaffected by the increase in simultaneous arrivals.

[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.[2] 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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Research challenges IV

Scalability – suggested solution:

• Group based operations of M2M communication: – group leader collects and forwards the information to the LTE/ LTE-A station[1]

• 5G: IoT gateway[2] :– Downlink connect the IoT devices using ex. ZigBee

– Uplink connect cellular network.

• Traffic classification

– Buffered in MAC buffers until transmission is triggered

• Compression

– A testbed setup of Classification reduced the number of uplink transmission form 120 to 60

– Further, using compression the number is reduced to 25.

[1] F. Ghavimi and H.-H. Chen, "M2M communications in 3GPP LTE/LTE-A networks: architectures, service requirements, challenges, and applications," IEEE Communications Surveys & Tutorials, vol. 17, no. 2, pp. 525-549, 2015.[2] N. Saxena, A. Roy, B. J. Sahu, and H. Kim, "Efficient IoT Gateway over 5G Wireless: A New Design with Prototype and Implementation Results," IEEE Communications Magazine, vol. 55, no. 2, pp. 97-105, 2017.

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Research challenges - V

Interoperability [1]

• Several LPWAN technologies – Challenge: No interoperability

– Challenge: Lack of universal infrastructure

– Challenge: Cost and revenue sharing / managing

• Standards needed to glue them together– IP based gateways

[1] U. Raza, P. Kulkarni, and M. Sooriyabandara, "Low Power Wide Area Networks: An Overview," IEEE Communications Surveys & Tutorials, vol. PP, no. 99, pp. 1-1, 2017.

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Research challenges - VI

Location challenge [1]– Various applications require accurate localization information

• objects, patients, alarms..

– Require accurate time synchronization and high base-station density.

– Locate the base station that a node is connected to

– Cellular provides location within base station area

Reliability /robustness challenges– Low base-station density, base-station becomes a single point of failure

• High base-station density: interference

– Cross-technology interference

– Cellular managed by network operators; hence more robust


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Research challenges -VII

High data rate modulation techniques [1]

– Modulation methods offer very low data rates.

– Higher data rates (more complex modulation schemes) increases the area of utilization

– Challenge: increase hardware cost, reduces transmission rage

Link optimization and adaptability

– Methods that adaptively monitor link quality to optimize performance

– Challenge: downlink information generally needed


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Research challenges - VIII

Security [1,2]– Challenge: Low energy nodes, limited data exchange

– Cellular: Subscriber Identity Modules (SIM) for identification and authentication.

– LRWA: Some solutions have poor security (SigFox do not encrypt payload (end-device <–> base station))

Mobility and roaming [1,2]– Challenge: Revenue, billing, varying spectrum regulations

– Provide roaming without compromising end-devices’ lifetime

– LPWAN: Low downlink communication rate, exploit uplink data

– Cellular networks have some roaming


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Research challenges - IX

Quality of Service [1,2]– Cellular network: QoS guarantee is easier in the licensed

spectrum

– LPWAN: QoS challenging due to unlicensed, spectrum, duty-cycle requirement etc.


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Conclusion

• There are various technologies addressing the huge IoT marked

• The cellular and the LPWAN technologies offers different capabilities – This may cause a differentiation between markets

• Cellular offer better bit rate, QoS and have higher geographical coverage

• LPWAN offer low initial cost and operation cost, and long lifetime. In addition flexible network design.

• In order to prevent vendor lock-in, standards are required

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Thank you for listening!

Documents

Long Range Wireless IoT Technologies - NTNU · Long Range Wireless IoT Technologies; Medium access layer • The simple Aloha protocol used in several technologies – Low delay –