Long-Range Low-power Radio (LoRa) Low Power Wide-Area Networks (LP-WAN) 11/27/2018 Chao GAO, VAMK

Long-Range Low-Power Radio Sensor Networks and IoT can be long range, e.g., electricity distribution substations are scattered. A wind farm could also cover a very large area. "A single gateway or base station can cover entire cities or hundreds of square kilometers.[LoRa Alliance 2015]" 11/27/2018 Chao GAO, VAMK

Short/Long Range/Cellular Applications: [LoRa Alliance 2015] Electric metering, Precision farming, Manufacturing automation, Intelligent building, Point of Sale (POS), Logistics, UAV, Medical wearables, Bicycle / vehicle tracking & location, Street Lighting, Smart parking, Waste management, Facility management, Airport management, etc. Short range WLAN,WPAN Long range LPWAN Cellular IoT Traffic provision 40% 45% 15% Well-established standards, Low cost Low/medium power consumption Low-power Low cost High data rate High reliability Short range WLAN high energy consumption Low data rate Lack of standards Extremely high cost High power 11/27/2018 Chao GAO, VAMK

Comparison ~10 years battery life 200 bps – 50kbps communication rate 2-5km in urban, 15-20km in suburban area. Star-of-stars topology Data rate 3G/4G Cellular WLAN BT LoRa Range Power consumption 11/27/2018 Chao GAO, VAMK

LoRa at 868MHz In EU LoRa operates on 433 and 868MHz. 8 channels defined in 868Mhz band. 865.2MHz 865.5MHz 867MHz 868MHz 10 11 12 13 14 15 16 17 Channel spacing: 0.3MHz { sx1272.setChannel(CH_10_868); // Set channel sx1272.getChannel(); // Get Channel } 11/27/2018 Chao GAO, VAMK

Increased Link Budget In order to get addition power gain, a DSSS spreading is applied. Spreading Factor (SF) varies 7… 12. Symbol duration is depended on SF and Bandwidth (BW), which can be chosen as 62.5, 125 or 250kHz. Bit rate of LoRa is depended on symbol rate 𝑇 𝑠 , and code rate (CR). CR is a Forward Error Correction (FEC) encoding and 𝐶𝑅= 4 4+𝑛 , 𝑛= 1,2,3,4. (with a bigger n, the receiver has better ability to correct errors) E.g., if BW=125kHz, SF=12, CR=4/5, 𝑇 𝑠 =32.8𝑚𝑠, 𝑅 𝑏 =293bps. (with a smaller SF, 𝑅 𝑏 gets bigger.) 𝑇 𝑆 = 2 𝑆𝐹 𝐵𝑊 Increasing SF will decrease 𝑅 𝑏 , but a better spreading gain, thus increase link budget. 𝑅 𝑏 =𝑆𝐹× 𝐶𝑅 𝑇 𝑠 11/27/2018 Chao GAO, VAMK

Increased Link Budget As SF decreases, the receiver sensitivity decreases. This makes communication range shorter. LoRa module can be configured into different modes: Mode BW CR SF Receiver Sensibility (dBm) Tx time to send 100 bytes (ms) Tx-Ack time to send 100 bytes (ms) Comments 1 125 4/5 12 -134 4245 5781 Max range, min rate 2 250 -131 2193 3287 3 10 -129 1208 2120 … 9 500 8 -117 220 890 7 -114 186 848 Min range, max rate { sx1272.setMode(3); // Sets the LoRa mode in transmission mode 3 } 11/27/2018 Chao GAO, VAMK

Tx Power Gain It is possible to vary Tx power for customized communication ranges. A LoRa module is able to be set in 0,1,2,…,5 power levels, with 0 corresponding to maximum Tx power and 5 to minimum power. Minimum power is 2dBm, every next level increase 3dB. All the above values depend on the type of LoRa module. 11/27/2018 Chao GAO, VAMK

LoRa SX1272 module Working with RPi, Arduino, and Libelium, a multiprotocol radio shield is needed to bridge the connection. 11/27/2018 Chao GAO, VAMK

LoRaWAN: Star of Stars Topology End device, LoRa gateway, IoT server. LoRaWAN LoRa GW End device End device End device End device End device End device LoRa GW LoRaWAN LoRa GW End device End device IoT Server End device IP connection 11/27/2018 Chao GAO, VAMK

LoRaWAN: node classes 3 classes [LoRaWAN Specification, 2015] Class A nodes use pure ALOHA access for the uplink. (what is ALOHA?) Class B comes with synchronization beacon. Class C has continuous receive window for low latency communications. Application LoRa MAC Class A Class B Class C LoRa Modulation EU 868 EU 433 US 915 AS 430 11/27/2018 Chao GAO, VAMK

LoRaWAN: Frame Format Sent out Uplink PHY frame format Preamble PHY Hdr PYH hdr CRC PYH Payload CRC Uplink PHY frame format Preamble PHY Hdr PYH hdr CRC PYH Payload Downlink PHY frame format MType Description 000 Join Request 001 Join Accept 010 Unconfirmed Data up 011 Unconfirmed Data down 100 Confirmed data up 101 Confirmed data down 110 RFU (Res. For future Use) 111 Proprietary MAC Hdr (1) MAC Payload (1-M) MIC (4) Major Description 00 LoRaWAN R1 01-11 RFU Mtype (3 bits) RFU (3 bits) Major (2 bits) DevAddr (4) Frame Control (1) Frame Count (2) Frame Opt. (0…15) 11/27/2018 Chao GAO, VAMK

Class A Communication is initiated by end devices. 2 Rx windows are reserved after every uplink package. RX1 is set in the frequency channel. RX2 is set in a pre-configured channel. Collision Downlink frame Downlink frame Gateway TIME End device 1 Uplink frame Uplink frame RX1 RX2 Uplink frame End device 2 RECV_DELAY1 RECV_DELAY2 11/27/2018 Chao GAO, VAMK

Summary Please read more LoRaWAN Spec. Summary (Yes/No about LoRaWAN, https://www.thethingsnetwork.org/wiki/LoRaWAN/Limitations): Long range, a few kms. low power, months – years operation low cost, < 20€/end device low bandwidth, a few hundred bytes/hour Reatltime data, such as realtime GPS update Phone call/streaming data High bandwidth data (sending photos, watching CCTV) 11/27/2018 Chao GAO, VAMK