Grant free IoT over 5G networks My presentation in Ericsson Research

1. KTH ROYAL INSTITUTE
OF TECHNOLOGY
Grant-Free Radio Access for IoT
Communications
Amin Azari
RS Lab, ICT School, KTH

2.  Part I: Introduction
 Part II) Coexistence analysis
 Interference analysis
 Coverage analysis
 Deployment and operation strategies
 Analytical coverage, reliability, cost modeling
 Optimized operation points
 Part IV) Protocol design
 Elements of the protocol
 Performance evaluation and results
 Part V: Future works
Outline
2 / 41

3.  Amin Azari, born 1988, Iran
 Education:
 BS (2010), MS (2013), Tehran & Rostock University (Iran & Germany).
 Lic. (2016) from ICT school, KTH:
 Battery lifetime-aware cellular network design
 Results: 1 thesis, 1 patent, 3 journals, 7 conf. publications
 Towards PhD (from 2017):
 Grant-free access for IoT communications
 Distributed optimization, machine learning, stochastic geometry
 Visit Aalborg University (3 months in spring 2017, Danish grant)
I.1) About me
3 / 41Part I) Introduction

4. I.2) Motivation
Characteristics of IoT
 massive in number of connections
 small payload size
 require long battery lifetime
Legacy cellular networks: grant-based radio access
 extensive signaling
 sending several bits requires several bytes overhead
– inefficiency for battery-limited devices
– causes congestion in network for control
– for URLLC: reliability depends on 3 transactions that cannot be
coded jointly, i.e. access reservation, response, data transfer.
4 / 41Part I) Introduction

5. I.2) Motivation
 no need for synchronization
– reduce delay & overhead & energy consumption
– reduce cost of device, i.e. low-cost oscillator
 no need for access reservation
– reduce delay & overhead & energy consumption
 but the above benefits are not coming for free…
– When/how much can we gain from grant-free access?
 Recent interests:
– [3GPP, “Overall solutions for UL grant free transmission”, 2017.]
– SigFox, LoRaWAN, etc.
5 / 41Part I) Introduction
Grant-free access

6. I.3) Prior Works
 Performance Evaluation:
– 2D time-frequency interference modelling using stochastic
geometry for performance evaluation LPWANs,
[Z. Li et al., 2016]
 Protocol design:
– Enhanced contention resolution ALOHA
[Clazzer et al, 2013]
– Asynchronous contention resolution diversity
[De Gaudenzi et al, 2014]
6 / 41Part I) Introduction

7.  Part I) Introduction
 Part II) Coexistence analysis
 Interference analysis
 Coverage analysis
 Part III) Deployment and operation strategies
 Analytical coverage, reliability, cost modeling
 Optimized operation points
 Part IV) Protocol design
 Elements of the protocol
 Performance evaluation and results
 Part V) Future works
Outline
7 / 41

8. II.1) system model
 Devices: 𝐾 types:
– Heterogeneous, e.g. SigFox, LoRa.
– Different in:
• Pattern of time/freq. usage,
• Transmit power,
• Rates of packet arrival at nodes, etc.
 Dense IoT device deployment, PCP.
– (𝜆 𝑘, 𝜐 𝑘, 𝑓(𝑥)) density of PP, avg. DP per PP, dist. of DP
 Fading: Nakagami-m. Pathloss:1/(𝑎 + 𝑏 𝑧
𝛿
)
 Application: ISM-band solutions, Cellular-band solutions
8 / 41Part II) Coexistence analysis
Type-1 node
Type-2 node Type-2 AP
Type-1 AP
𝐾 = 2, ISM

9. II.2) Research questions
 Probability of uplink coverage at distance 𝑑 from
the AP?
 Reliability of communications at a random point of
network for
– a given deployment of APs (joint and independent
reception), and
– a given number of transmissions per packet?
9 / 41Part II) Coexistence analysis

10. II.3) Interference analysis
 Finding Laplace functional (LF) of the interference,
because:
 LF of interference in cellular networks mature,
while for short packet communications there is no
prior work.
10 / 41Part II) Coexistence analysis
LF interference LF noise

11. II.3) Interference analysis
Problems in using stochastic geometry (prior art):
 Partial overlapping in time and frequency
 Different transmit powers, transmission times, packet
generation rates, BW of signals, total BW for
communications.
11 / 41Part II) Coexistence analysis

12. II.3) Interference analysis
 By defining time and frequency activity factors, we
have derived LF of interference:
 In PPP reduces to:
12 / 41Part II) Coexistence analysis
×
ℒ 𝐼Ψ 𝑧 𝑠 =
𝑖=1
𝐾
exp(− 𝜐𝑖 𝐸 ℎ 𝛿 Γ 1 − 𝛿 𝑠 𝑃𝑖
𝛿
)
Own cluster
All other clusters

13. II.3) Coverage analysis
 Lowerbound for type 𝑖 at distance ||𝑧||:
 Closed-form exact expressions for PPP.
 Insights: impact of 𝑊, 𝑃𝑡, 𝜆 𝑎on coverage.
13 / 41Part II) Coexistence analysis
Where for 𝑔 𝑧 = 𝑧
−𝛿
.

14. II.3) Coverage analysis
 Now, for any point in the network,
– given distance vector d from neighbour APs
– given number of transmissions per packet
We are able to derive the outage probability.
 In PPP deployment of APs:
– CDF of distance to 𝑙-th AP:
then, closed-form expression for outage for a random
device in the network is derived.
14 / 41Part II) Coexistence analysis

15. II.4) Simulation results
15 / 41Part II) Coexistence analysis
 Parameters (simplified LoRa network with interferers)

16. II.4) Simulation results
16 / 41Part II) Coexistence analysis

17. II.4) Simulation results
17 / 41Part II) Coexistence analysis

18.  Part I) Introduction
 Part II) Coexistence analysis
 Interference analysis
 Coverage analysis
 Part III) Deployment and operation strategies
 Analytical coverage, reliability, cost modeling
 Optimized operation points
 Part IV) Protocol design
 Elements of the protocol
 Performance evaluation and results
 Part V) Future works
Outline
18 / 41

19. III.1) system model
 Similar to part II:
– Dense IoT device deployment, PCP.
– Type of devices:
• Heterogeneous, e.g. SigFox, LoRa, Alarms, etc.
• Different in:
– Pattern of time/frequency resource usage,
– Transmit power,
– Rates of packet arrival at nodes, etc.
– Fading: Nakagami-m.
19 / 41Part III) Deployment and operation
Type-1 node Type-2 node BS
𝐾 = 2, Cellular

20. III.2) Research questions
 Deployment phase:
– Regarding impact of 𝑊 and 𝜆 𝑎 on coverage:
*optimized amount of investment in densification and
spectrum leasing for a given reliability for IoT.
 Operation phase:
– Regarding impact of transmit power and
subchannel/code selection:
*optimized online policy for transmission for a given
reliability and AP deployment density.
20 / 41Part III) Deployment and operation

21. III.3) KPI modeling
 Cost of the access network:
 Reliability of communications:
– Investigated in part II, e.g. for grid AP deployment:
 Expected battery lifetime of devices:
– 𝐿 𝑖 =
[Energy Storage: 𝐸0]
[Energy Consumed Per Reporting]
[Reporting Period: 𝑇𝑖]
21 / 41Part III) Deployment and operation

22. III.4) Analysis (ongoing)
 Investigation of the following problems:
– Deployment:
– Operation:
22 / 41Part III) Deployment and operation

23. III.4) Initial simulation results
23 / 41Part II) Coexistence analysis
 Fixed 𝑊 and 𝑃𝑖, variable 𝜆 𝑎
Dense BS deployment Sparse BS deployment

24.  Part I) Introduction
 Part II) Coexistence analysis
 Interference analysis
 Coverage analysis
 Part III) Deployment and operation strategies
 Analytical coverage, reliability, cost modeling
 Optimized operation points
 Part IV) Protocol design
 Elements of the protocol
 Performance evaluation and results
 Part V) Future works
Outline
24 / 41

25. IV.1) system model
 Dense IoT device deployment, PPP
 Packet arrival at nodes: Poisson

signal BW
Available spectrum
≪ 1
– Utra-NarrowBand (UNB) system
25 / 41Part IV) Protocol design

26. IV.3) Key idea
In UNB the signal bandwidth is smaller than the
precision of the carrier frequency
 random frequency deviation used as an
identification code as in:
[Fyhn, Jacobsen, Popovski, Scaglione, Larsen, 2011]
frequency
Intended carrier frequency
Max
drift
Max
drift
𝑉𝐹𝑖
Δ𝑓𝑖
𝜏𝑖
time
26 / 41Part IV) Protocol design

27. IV.4) Transmission structure
 virtual frame
– sends one replica of packet immediately;
– forms a virtual frame, selects N slots to send replicas.
– N: design parameter
– use of SIC
𝑀 slots =𝑀𝑇𝑝 seconds
Reference time
carrier frequency:
𝑓𝑖 = 𝑓 + Δ𝑓𝑖
selected N slots for
main packet/replicas
transmissions
27 / 41Part IV) Protocol design

28. IV.5) Receiver design
 Problem of partial interference due to
asynchronicity
Frequency
Intended carrier frequency
Max
drift
Max
drift
𝑉𝐹𝑖
Δ𝑓𝑖
𝜏𝑖
Time
28 / 41Part IV) Protocol design

29. IV.5) Receiver design
i. Use of Zadoff-Chu as preamble in transmitters:
i. length of preamble: design parameter.
ii. tradeoff: overhead vs. decodeability
ii. window the received signal
i. time length: design parameter.
ii. offers tradeoff: delay and decodeability
iii. decode with intended frequency
iv. use periodogram and search for peaks
i. peaks drift from carrier frequencies in the receive
signal, i.e. represent a signature of some devices.
29 / 41Part IV) Protocol design

30. IV.5) Proposed receiver design
 Potential solution: Graphical overview
30 / 41Part IV) Protocol design

31. IV.6) Analysis
31 / 41Part IV) Protocol design

32. IV.6) Analysis
 TiSy: devices are slot synchronized.
 FrSy: the CFOs of the devices can take equally-spaced
discrete values, i.e. the devices are sub-channel
synchronized, where the channels are spaced each 200 Hz.
 reference: granted radio access with
10 random access resources each 2 seconds.
 offered load per channel
32 / 41Part IV) Protocol design

33. IV.6) Analysis: network EE
33 / 41Part IV) Protocol design

34. IV.6) Analysis: battery lifetime
34 / 41Part IV) Protocol design

35. IV.6) Analysis: delay
35 / 41Part IV) Protocol design

36. IV.6) Analysis: reliability
36 / 41Part IV) Protocol design

37. IV.7: concluding remarks
 In low to medium traffic load regime,
grant-free access can:
– achieve low energy consumption,
– Decrease the experienced delay.
 There is a switchover traffic load beyond which
granted-access outperform grant-free access.
 Under very low load, reliability increased significantly
37 / 41Part IV) Protocol design

38.  Part I) Introduction
 Part II) Coexistence analysis
 Interference analysis
 Coverage analysis
 Part III) Deployment and operation strategies
 Analytical coverage, reliability, cost modeling
 Optimized operation points
 Part IV) Protocol design
 Elements of the protocol
 Performance evaluation and results
 Part V) Future works
Outline
38 / 41

39. V: Future works
 Use of ML for
– physical layer authentication!
– Better contention resolution!
– Less interference!
39 / 41Part V) Future works

40. V: Future works
 Publications:
– Grant-Free Radio Access for Short-Packet Communications over 5G
Networks, A Azari, P Popovski, G Miao, C Stefanovic, IEEE GC 2017
– Optimized Deployment and Operation Strategies for Grant-free Radio
Access IoT Networks, Amin Azari, M Masoudi, C Cavdar, IEEE wireless
communications letters (to be submitted, 2017)
– Grant-free, Grant-based, or Hybrid? Mode Switching MAC for Cellular IoT
Networks, Amin Azari, IEEE Transactions on Wireless Communications (to
be submitted, 2018)
– Grant-free Radio Access IoT Networks: Scalability Analysis in Coexistence
Scenarios, M Masoudi, A Azari, EA Yavuz, C Cavdar, IEEE ICC 2018
40 / 41Part V) Future works

41. Questions
 Thanks for your kind attention,
 Questions and answers.

42. The End
The End!