Duty-Cycle-Aware Real-Time Scheduling of Wireless Links in Low Power

Duty-Cycle-Aware Real-Time Scheduling of Wireless Links in Low Power WANs Md Tamzeed Islam

Popularity of Low Power Wide Area Network Long Range Low Power Low Data Rate LPWAN is becoming popular day-by-day

Different LPWANs LoRa is one of the most popular LPWANs

Features of LoRa 9 miles 50 kbps 10 years

Overview of LoRa

Overview of LoRa Node Gateway Node Network Server Node Application Server Gateway Node LoRA 4G/Ethernet TCP/IP 4G/WiFi

LoRa Properties frequency Chirp Spread Spectrum (CSS) Modulation time Figure: CSS Operates on ISM band

Issues Pure Aloha Uses ALOHA for MAC Layer protocol.

Duty-Cycle Limit Node : 1st transmission Channel 1 Duty Cycle: 50% Duty Cycle Limit, 50% L1 Can not use Channel 1 (C1) for duty-cycle limit τ11 L1 0 1 2 3 4 5 6 Time Channel1 (C1) Figure: Duty Cycle Limit 7 8 9 10

Duty-Cycle Limit Node : 1st transmission Channel 1 Duty Cycle: 10% Duty Cycle Limit, 10% L1 Can not use Channel 1 (C1) for duty-cycle limit τ11 L1 0 1 2 3 4 5 6 Time Channel1 (C1) Figure: Duty Cycle Limit 7 8 9 10

Real Time Scheduling for LoRa

Motivation Link Release Time Time on Air Deadline Period L1 0 2 3 5 L2 0 4 5 5 L1 Can not use Channel 1 (C1) for duty-cycle limit Duty Cycle Limit, 40% τ12 τ11 L1 0 1 2 3 4 5 6 Time Channel1 (C1) 7 8 9 10

Traditional Scheduling Algorithm L1 Can not use Channel 1 (C1) for duty-cycle limit Deadline miss τ12 τ11 L1 L2 Can not use Channel 2 (C2) for duty-cycle limit τ21 τ22 L2 0 1 2 3 4 5 6 7 8 Time Channel1 (C1) Channel2 (C2) 9 10

Desired Scenario τ12 τ11 L1 τ21 L2 0 1 τ13 τ22 2 3 4 5 6 7 τ23 8 9 10 Time Channel1 (C1) Channel2 (C2) 11 12 13 14 15

Proposed Solution Gr(C1, 5) 0 Gr(C1, 2) 3 L1 τ11 Time Channel1 (C1) Gr (C1) max (Gr (C1),𝑇¿¿𝑜𝑓𝑓 ) max ( 0,3 ) 3¿

Proposed Solution Packet Selection: Least Laxity First Channel Selection: Available channel with the maximum gravity.

Proposed Solution Gr(C1, 2) 3 Gr(C2, 4) 6 τ12 τ11 L1 τ21 L2 0 Gr(C1, 5) 0 Gr(C2, 5) 5 1 τ22 2 3 4 5 6 7 8 Time Channel1 (C1) Channel2 (C2) 9 10

Implementation & Setup

Implementation

Implementation (LoRa Node) Components: A LoRa radio shield with an Arduino Uno. LoRa radio shield: transceiver SX1272/73. Software: IBM lmic Library. Power: 10,000mAh USB power bank. Clock: an external real-time clock.

Implementation(Gateway) Multitech Conduit device. Runs on an enhanced closed source embedded Linux platform. a configurable and scalable Internet gateway for industrial IoT. listens to one sub-band at a time. a gateway can listen to eight channels simultaneously.

Implementation (Application Server)

Setup

Setup

Indoor Setup N1 -82dB 5 transmitters 1 receiver N2 -113dB N3 rio (b) Indoor Scenario ment of the nodes and the gateway in the real-world experiment.

Result Indoor 9.23 Percentage 10 8 6 4.62 4 2 1.54 0.00 0 D-LLf LLF Scheduling Algorithm Packets Missing Deadline Packets Dropped

Lora Map Outdoor Setup Untitled layer N1 Point 10 Point 12 Point 13 Point 5 N1 -82dB Point 6 23 3m N5 185m 12m -34dB 2 20 8m 21 N4 -103dB m N2 -113dB -91dB N3

Result Outdoor 9.23 Percentage 10 8 6.15 6 4.62 4 2 0.00 0 D-LLf LLF Scheduling Algorithm Packets Missing Deadline Packets Dropped

Future Work Fixing issues in simulation. Necessary/sufficient condition for schedulibility. Distributed version of scheduling algorithm.

Thank You