1. Submission Title: IEEE Standards for Low Power Wide Area Networks
July 2016
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: IEEE Standards for Low Power Wide Area Networks
Date Submitted: July 2016
Source:
Joerg Robert, Friedrich-Alexander University (FAU) Am Wolfsmantel 33, Erlangen, Germany
Abstract: Suitability of IEEE Standards for LPWAN
Purpose: Discussion in IEEE SC WNG
Notice: This document has been prepared to assist the IEEE P It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.
Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P
Joerg Robert

2. IEEE Standards for Low Power Wide Area Networks
July 2016
IEEE Standards for Low Power Wide Area Networks
Joerg Robert
July, 2016
Joerg Robert

3. Concept of Low Power Wide Area Networks (LPWAN)
July 2016
Concept of Low Power Wide Area Networks (LPWAN)
e.g. 100m
e.g. 40km
e.g. 10dBm
Small and cost-efficient sensors nodes communicate using ultra-low power over ultra-long distances
The base-stations antennas are typically mounted at highly exposed sites (e.g. on top of TV broadcast transmitter masts)
A typical base-station serves up to one million sensor nodes
Typical application scenarios: Water/gas metering, environmental monitoring, ... [1]
Joerg Robert

4. Advantages of LPWAN / Motivation
July 2016
Advantages of LPWAN / Motivation
Possibility to setup large and cost-efficient networks, as only few base-stations are required
Possibility for ultra-low-cost and ultra-small devices that can operate for many years using tiny AA batteries
BUT:
How well is this network type covered by IEEE standards?
Which potential standards do exist?
Joerg Robert

5. July 2016
Challenges of LPWAN
Ultra-low power in addition to long distances leads to very weak reception levels (typical assumption < -140dBm)
Very low bit rates (1 < kbit/s)
Interference from other services as license-exempt bands are commonly used (e.g. 434MHz, 868/915MHz, 2.4GHz)
Further increased interference at base-station due to highly exposed antennas
Concepts as CSMA (Carrier Sense Multiple Access) do not work because of the hidden node problem
Use of spread spectrum (e.g. DSSS) or frequency hopping
.... and many additional challenges
Joerg Robert

6. Measured Spectrum in 868MHz Band
July 2016
Measured Spectrum in 868MHz Band
Joerg Robert

7. Potential Standards for LPWANs
July 2016
Potential Standards for LPWANs
Focusing on license-exempt bands:
IEEE k
SIGFOX
LoRaWAN
ETSI LTN, Weightless, IEEE ah
...
Focusing on licensed bands:
3GPP standards, e.g. NB-IoT (Narrow Band IoT)
Joerg Robert

8. Performance Evaluation in AWGN
July 2016
Performance Evaluation in AWGN
Payload bit rate as function of the reception level can be theoretically calculated using Shannon‘s findings for ideal systems
Assumptions:
Eb/N0=-1.59dB
Noise figure 0dB
Noise power spectral density -174dBm/Hz
Joerg Robert

9. Max. Payload Bit Rate vs. Rx Power
July 2016
Max. Payload Bit Rate vs. Rx Power
Example: -140dBm3.6kbit/s
Joerg Robert

10. July 2016
IEEE k DSSS-PHY ( I / II )
Amendment 5: Physical Layer Specification for Low Energy, Critical Infrastructure Monitoring Networks (LECIM)
DSSS Phy based on Gold (and optional OVSF code) with modulation rate 200ksym/s ksym/s
Spreading factor up to  R=3bit/s (BPSK)  Min. telegram length of 42s!  Max. spreading factor limited to 256 in the US (FCC regulation, max. 0.4s signal duration, [4, Q.2.1])
Interference reduction capabilities (linear receiver) of 45dB (spreading of 32768) and 25dB (spreading of 256)
2.5ppm radio frequency tolerance  requires precise oscillators
Joerg Robert

11. IEEE 802.15.4k DSSS PHY ( II / II ) FCC Max. Robust
July 2016
IEEE k DSSS PHY ( II / II )
FCC
Max. Robust
Assumptions concerning noise figure and implementation loss are unclear!
Joerg Robert

12. IEEE 802.15.4k FSK-PHY Second Phy offered by 802.15.4k
July 2016
IEEE k FSK-PHY
Second Phy offered by k
(Position based) (G)FSK modulation down to very low rates 0.5kbit/s
Document states minimum required receiver sensitivity of -97dBm, independently of any modulation and coding  Would correspond to 37dB loss wrt. theory
No real robustness wrt. interferers, as no frequency hopping or spreading are used
Potential issue with required frequency accuracy
Joerg Robert

13. July 2016
SIGFOXTM ( I / II )
SIGFOX is a fully proprietary system offered by the company SIGFOX  detailed information about the system is not available
The modulation format is BPSK using a data rate of 100bit/s where each message contains 12 bytes payload [3]  Telegram time of approx. 6s (each message is transmitted three time  effective rate of 33bit/s)
The original SIGFOX standard is not FCC compliant [3]  Modified version for US market with less link budget
Robustness against interference is reached by means of three transmissions of the same data on different channels
Joerg Robert

14. July 2016
SIGFOXTM ( II / II )
Assumed receiver sensitivity of -142dBm [3] with 33bit/s effective bit rate (does potentially not include receiver noise figure)
Joerg Robert

15. July 2016
LoRaWANTM ( I / II )
Specification of the LoRa Alliance (mainly driven by Semtech)
Modulation uses spread spectrum with data rate ranging from 0.3 kbps to 50 kbps
Interference reduction capabilities due to spread spectrum modulation
Performance figures available due to existing chip implementations [5], e.g. 18 bit/s at -148dBm
Joerg Robert

16. July 2016
LoRaWANTM ( II / II )
Assumed receiver sensitivity of -148dBm with 18bit/s effective bit rate (represents available receiver design SX 1276 [5] including all implementation losses)
Joerg Robert

17. Other Standards for License-Exempt Bands
July 2016
Other Standards for License-Exempt Bands
ETSI is working on “ETSI LTN” standard for LPWANs [2]
Contributions from SIGFOX, Semtech, ...
Weightless is an additional standard for sub-GHz LPWAN [6]
Based on DBPSK with ultra-low bandwidth (similar to SIGFOX)
IEEE ah
Slowest mode offers 150kbit/s  perfect system would require PRx=-123dBm  no real long-range system
Joerg Robert

18. 3GPP NB-IoT Narrow Band IoT is part of 3GPP Release 13 [7]
July 2016
3GPP NB-IoT
Narrow Band IoT is part of 3GPP Release 13 [7]
System can operate stand-alone, in LTE guard band or within normal LTE carrier
NB-IoT was created under strong pressure from the mobile network operators
Further enhancements will be part of 3GPP Release 14
Joerg Robert

19. Summary LPWANs are interesting networks for many applications
July 2016
Summary
LPWANs are interesting networks for many applications
A variety of proprietary and non-IEEE standards are appearing
The full suitability of existing IEEE standards for LPWANs is not clear
Existing standards may offer significant room for improvements
The 3GPP community is highly focusing on the development of LPWAN standards
Joerg Robert

20. July 2016
What should IEEE do?
Should IEEE leave the field to 3GPP and proprietary systems? OR
Investigate the suitability of existing IEEE standards for LPWANs?
Possible way forward:
Setup Interest Group to evaluate existing IEEE standards
Create usage scenarios for license-exempt bands
Create suitable channel and interference models
Investigate performance of existing standards
Joerg Robert

21. July 2016
Questions?
Joerg Robert

22. July 2016
References
[1] X. Xiong, K. Zheng, R. Xu, W. Xiang and P. Chatzimisios, "Low power wide area machine-to-machine networks: key techniques and prototype," in IEEE Communications Magazine, vol. 53, no. 9, pp , September [2] for-internet-of-things-and-machine-to-machine-low-throughput-networks [3] b8cd-f6e cb_RPMA%20Technology.pdf [4] IEEE k Amendement [5] [6] [7]
Joerg Robert