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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. Summary Please read more LoRaWAN Spec.
Summary (Yes/No about LoRaWAN,
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