How To Triple The Range of LoRa
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Haystack is introducing a new mode called DASH7 XR Mode that can triple the range of LoRa networks. It utilizes advanced error correction techniques as well as automated receipt responses. Testing shows it can achieve 2-3x the range of LoRaWAN networks while preserving multi-year battery life. Private beta testing of XR Mode is now underway.
How To Triple The Range of LoRa
- 1. How To Triple The Range of LoRa © 2019 Haystack Technologies, Inc.
- 2. 2 Executive Summary • Haystack is introducing a new DASH7 implementation for LoRa: XR Mode. • Using software-only enhancements, DASH7 XR Mode for LoRa provides 2-3x range improvements over comparable observed LoRaWAN performance at ground level while preserving multiple year endpoint battery life. • XR Mode utilizes 2-way LDPC Error Correction as well as Automated Receipt Response for guaranteed message delivery. Shorter packet sizes and lower data rates than are typically deployed with DASH7 are also utilized. • XR Mode running at a higher data rate can achieve the same QoS as LoRaWAN running at a much lower data rate. This translates to 10-20x the network density and 10-20x the battery life vs. LoRaWAN, for a given QoS. • Private beta testing for XR Mode is now underway.
- 3. 3 Background • Some LoRa range test results make aggressive claims (“Up to 30 miles!”) which often do not match real world customer results. These marketing claims are typically based on “best case” outdoor testing environments and may result in unhappy customers and harm long-term adoption. • In comparison, testing LoRa at ground level yields very different results from testing conducted in such ideal outdoor environments. Yet some Haystack customer requirements include both gateways and endpoints deployed at or near ground level. • To improve range performance at all levels, but in particular at ground level, we spent the last six months optimizing our OpenTag firmware stack for extended range and reduced packet error rates over LoRa. The result: DASH7 XR Mode.
- 4. DASH7™ 4 Technical Features ‣ 2-way LPWAN networking software ‣ Works across many different LPWAN radios ‣ Ultra-low power (years on coin cell) ‣ Low latency (<2 sec.) queries ‣ Broadcast, multicast, P2P messaging ‣ Two-way error correction ‣ Message delivery confirmation ‣ Real-time GPS, A-GPS support ‣ Indoor location via RSSI, TDOA, others ‣ AES128 private-key + public-key crypto ‣ OTA firmware updates, key refreshes ‣ Smart contract support at endpoint ‣ Invented by Haystack! OSI Layer 7 Application UDP + OIC + NDEF + iOS, etc. 6 Presentation DASH7 Core low power low latency low cost 5 Session 4 Transport 3 Network 2 Data Link 1 Physical (Radio) LoRa, Other Options DASH7: The Most Advanced Networking Stack for Low Power Wide Area Networks
- 5. LoRa® 5 For more information on LoRa: https://www.semtech.com/lora/ LoRa is a radio, not a protocol. To exploit its true potential and performance, it requires an advanced protocol stack Basic Attributes ‣ Popular low power, wide area networking radio from Semtech ‣ Promises multi-year battery life and multi- kilometer range ‣ Mostly intended for use in unlicensed spectrum (915 MHz in USA) ‣ Low cost (~$3 in volume today) ‣ Modules available from Murata, Microchip, ST Micro, others
- 6. 6 Today: Two DASH7 Options For LoRa Option 1: DASH7 LAN Mode Optimal for usage with most software & business logic. Includes fully bidirectional data transfers, point-to-point, broadcasting, and real-time (asynchronous) communication. Typ. Ground-to-Ground Range: Light-Urban 0.20 miles / 0.33 km Typical Data Rate 16 kbps Typical “Real World” Link Budget 130 dB Endpoint Default Operation Event-driven (asynchronous) LDPC Error Correction (Coming Soon) Message Delivery Confirmation Yes Send Commands, Queries To Endpoint Yes Real-Time Queries to Endpoint Yes Packet Size Variable: up to 256 bytes Multi-Year Battery Life Yes GPS-based Geolocation (Low Power) Yes: OTA A-GPS Geofencing Real-Time, Low Power Broadcast, Multicast Messaging Yes OTA Firmware Updates Yes 0.64 miles / 1 km Typ. Ground-to-Ground Range: Light-Urban 1.1 kbps Typical Data Rate 153 dB Typical “Real World” Link Budget Periodic Msg (synchronous) Endpoint Default Operation Yes LDPC Error Correction Yes Message Delivery Confirmation Limited Functionality Send Commands, Queries To Endpoint No Real-Time Queries to Endpoint Fixed: 16 bytes Packet Size Yes Multi-Year Battery Life Yes: Preloaded A-GPS GPS-based Geolocation (Low Power) Beacon Geofencing No Broadcast, Multicast Messaging No OTA Firmware Updates Option 2: DASH7 XR Mode Optimized for delivering LPWAN pub-sub messaging at maximum theoretical range.
- 7. 7 Today: Two DASH7 Options For LoRa Option 1: DASH7 LAN Mode Optimal for usage with most software & business logic. Includes fully bidirectional data transfers, point-to-point, broadcasting, and real-time (asynchronous) communication. Typ. Ground-to-Ground Range: Light-Urban 0.20 miles / 0.33 km Typical Data Rate 16 kbps Typical “Real World” Link Budget 130 dB Endpoint Default Operation Event-driven (asynchronous) LDPC Error Correction (Coming Soon) Message Delivery Confirmation Yes Send Commands, Queries To Endpoint Yes Real-Time Queries to Endpoint Yes Packet Size Variable: up to 256 bytes Multi-Year Battery Life Yes GPS-based Geolocation (Low Power) Yes: OTA A-GPS Geofencing Real-Time, Low Power Broadcast, Multicast Messaging Yes OTA Firmware Updates Yes 0.64 miles / 1 km Typ. Ground-to-Ground Range: Light-Urban 1.1 kbps Typical Data Rate 153 dB Typical “Real World” Link Budget Periodic Msg (synchronous) Endpoint Default Operation Yes LDPC Error Correction Yes Message Delivery Confirmation Limited Functionality Send Commands, Queries To Endpoint No Real-Time Queries to Endpoint Fixed: 16 bytes Packet Size Yes Multi-Year Battery Life Yes: Preloaded A-GPS GPS-based Geolocation (Low Power) Beacon Geofencing No Broadcast, Multicast Messaging No OTA Firmware Updates Option 2: DASH7 XR Mode Optimized for delivering LPWAN pub-sub messaging at maximum theoretical range.
- 8. DASH7 XR Mode for LoRa • XR: “eXtended Range” DASH7 protocol • Runs concurrently with DASH7 LAN Mode • Improves real-world signal propagation over LoRaWAN by 10-13 dB (10-20x) • Retains essential features like real-time GPS location and multi-year battery life • Software-based approach: No HW or antenna modifications required • XR Mode delivers the longest range connectivity for battery-powered LoRa devices in the world today 8 Observed Sensitivity @ 1kbps 110 117.5 125 132.5 140 LoRaWAN DASH7 LAN DASH7 XR - - - - - dBm How is this gain possible? XR Mode algorithms come from very recent technology for communicating with probes in deep space.
- 9. XR Mode: Shorter Packet Lengths 9 • We reconfigured DASH7 frame from the conventional, variable size (up to 256 bytes), to a fixed size of 16 bytes. • Most LPWANs use small packets, so we picked a size that gives the best efficiency for our deep space error correction algorithm. • The packet is small, but it is sufficient for geolocation or sensor data, and it can support strong cryptography. 1 2 3 4 65 8 9 10 11 12 13 14 15 Link Info Subnet Info Tokenized ID Encrypted Forward CRC8 XR Mode 16 Byte Frame 7 16 Data ID Data Payload Data CRC8
- 10. XR Mode: Lower Data Rate, Greater Range 10 • Basic Truth 1: lower data rate = more energy per bit = longer range • Basic Truth 2: lower data rate = longer transmission = device drains more power • We observed that roughly 1 kbps is the best data rate trade-off (using LoRa) for achieving maximum range in an LPWAN device with multi-year battery requirement. ‣ DASH7 LAN Mode uses 16 kbps (LoRa SF7, 500 kHz) ‣ XR Mode uses 1.1 kbps (LoRa SF11, 500 kHz, + Haystack LDPC encoding) • We observed a range improvement of XR Mode vs LAN Mode ‣ 3x: Ground-to-Ground with obstacles (extreme non-line-of-sight) ‣ 6x: Elevated antenna to ground endpoint, with obstacles (moderate non-line-of-sight) ‣ >20x: Line of Sight
- 11. XR Mode: More Efficient than LoRaWAN 11 • Basic Truth 1: lower data rate = more energy per bit = longer range • Basic Truth 2: lower data rate = longer transmission = device drains more power • In order to determine energy use to send a message, we need to establish a baseline QoS. In this case, it is 1% PER (packet loss) at 146 dB link budget. • We observed that XR Mode performs significantly better than LoRaWAN at any data rate. As result, if we set equal QoS, XR Mode is 22 times more energy efficient than the longest-range LoRaWAN Mode. ‣ “LoRaWAN DR0” | 150 bps | -126 dBm @ PER 30% | 811 mJ per msg ‣ XR Mode | 1074 bps | - 132 dBm @ PER 1% | 36.5 mJ per msg TPKT Packet Time-on-Air PTX TX Power PRX RX Power XC Cumulative probability of error EMSG Energy of message EMSG = TPKT (PTX + PRX) * XC TPKT 1254 ms PTX 412.5 mW (@ 20 dBm) PRX 42.9 mW XC 1.42 EMSG 811 mJ LoRaWAN DR0 TPKT 194 ms PTX 145.2 mW (@ 14 dBm) PRX 42.9 mW XC 1.0 EMSG 36.5 mJ DASH7 XR Mode
- 12. 12 The greatest advancement DASH7 XR Mode brings is its error correction technology.
- 13. 1. Forward Error Correction (FEC), where sender encodes the data using an error- correcting code prior to transmission. The additional information (redundancy) added by the code is used by the receiver to recover the original data in the case of corruption. 2. Automatic Repeat Request (ARQ), which uses acknowledgements (messages sent by the receiver indicating that it has correctly received a packet) and timeouts (specified periods of time allowed to elapse before an acknowledgment is to be received) to achieve reliable data transmission over an unreliable service. If the sender does not receive an acknowledgment before the timeout, it usually re-transmits the packet until the sender receives an acknowledgment or exceeds a predefined number of retransmissions. Two Types of LPWAN Error Correction 13
- 14. LPWANs & Forward Error Correction 14 LPWANs operating in unlicensed radio spectrum contend with high levels of noise, unpredictable network congestion, or ground-level gateway deployments where terrain and other objects negatively impact range. Packet Error Rate (PER) Percentage of packets not successfully received by a gateway. If we can find a way to reduce PER, we can increase the range and/or Quality of Service (QoS) of the network. RangePER QoS= Forward Error Correction (FEC) FEC is a common remedy to high PER in virtually all contemporary wireless networking technologies, however it is strangely crude or non-existent in most LPWAN standards.
- 15. LoRa HW Built-in Forward Error Correction 15 • The LoRa radio includes a forward error correction (FEC) feature in the radio hardware. • The downside is that it is an outdated implementation, and it actually does more harm than good in most usages (including LoRaWAN) • The technical details of why it’s a poor design are beyond the scope of this presentation, but the basics are: ‣ It is 1950’s-era technology. Better technology is available. ‣ LoRaWAN and all known usages of LoRa, apart from DASH7, use suboptimal configurations of the built-in error correction. ‣ The actual implementation in HW seems to have some bugs that result in occasional false positives. • We have replaced LoRa’s HW FEC with our software implementation of the most advanced FEC technology known to man (as of 2019) Range PER No FEC LoRa HW FEC (Best config) DASH7 XR FEC LoRaWAN
- 16. Mobile LPWANs Require Better PER 16 Environmental Variables Terrain Diversity Multipath/ Fading Distance from gateway Distance traveled/day Frequency of Movement Elevation We can see that robust error correction not only makes range greater, but it improves the shape of the PER curve. • For LPWANs of fixed-position endpoints, the endpoints can be adjusted at time-of-deployment to achieve acceptable PER. • Mobile LPWAN solutions must contend with changing or unpredictable variables. PER must be acceptable for worst-case scenarios. • If the environmental variables are unpredictable, you want a PER curve that is as flat as possible. Range PER LoRa HW FEC (Best config) DASH7 XR FEC LoRaWAN Robust FEC flattens the PER curve, making XR Mode more reliable than LoRaWAN when the environment is unpredictable
- 17. XR Mode Error Correction DASH7 XR Mode uses the most advanced FEC in conjunction with ARQ 17 Automatic Repeat Requests (ARQ) • Operates via DASH7 Networking Layer ‣ Devices know to retransmit incorrectly received frames. ‣ Devices will automatically reduce transmission power to suit the required link budget (saves energy and creates less interference for others) • DASH7 ARQ process operates until: ‣ Packet is corrected ‣ Time-out is reached ‣ Shannon limit reached Forward Error Correction (FEC) • Haystack proprietary implementation of CCSDS “Orange Book” Non-binary LDPC coding ‣ Bidirectional: full decoder implemented on cheap ARM Cortex M0+ endpoint, as well as gateway. ‣ Performance is very close to theoretical limit (Shannon) • Engineering challenge was to get it working in such a RAM & CPU constrained environment. • Similar tech is used to enable communication with space probes out in deep space, and also in 5G Cellular.
- 18. 18 Important Note: DASH7 Error Correction is Fully Bidirectional 2Way • FEC Encoders are relatively simple to implement. FEC Decoders are much harder to implement. ‣ For example, Sony Eltres implements uplink LDPC, but does not implement a downlink to the endpoint. ‣ SigFox also has optional uplink FEC (Convolutional code) • In order to have guaranteed message delivery, the gateway needs to be able to send ARQ messages to the endpoint. ‣ Very important for broadcast-with-acknowledgement, which (for example) Haystack uses to do real-time queries. • If the endpoint cannot decode FEC, the gateway needs to compensate by transmitting messages to endpoint with much greater power. ‣ In rare cases this is OK, but most of the time there are regulatory limits that make it impossible for a gateway to compensate with enough power to reach the endpoint.
- 19. 19 We have begun range testing XR Mode in the SF Bay Area and have some results to share
- 20. XR Mode Range Test #1 20 Hardware STMicro Discovery Kit (SX1276) with external dipole TX Power 17 dBm Environment Light-Urban (San Mateo, CA), mostly flat Gateway Elevation 1 m / 3.3 feet Endpoint Elevation 1 m / 3.3 feet Results best range: 1 km / .64 miles Gateway (1m) Endpoint (1m) Propagation Fading Profile for Test #1 < 1% LOS (line of sight) 74% NLOS (non-line of sight) 25% Obstructed
- 21. XR Mode Range Test #2 21 Hardware STMicro Discovery Kit (SX1276) with external dipole TX Power 17 dBm Environment Light-Urban (San Mateo, CA), subtle rolling terrain Gateway Elevation 5 m / 16.4 feet Endpoint Elevation 1 m / 3.3 feet Results best range: 1.77 km / 1.1 mi Gateway (5m) Endpoint (1m) Propagation Fading Profile for Test #2 13% LOS (line of sight) 62% NLOS (non-line of sight) 25% Obstructed
- 22. XR Mode Range Test #3 22 Hardware STMicro Discovery Kit (SX1276) with external dipole TX Power 17 dBm Environment Hilltop, then over SF bay, then suburban Gateway Elevation 360 m / 1181 feet Endpoint Elevation 1 m / 3.3 feet Results best range: 27.5 km / 17.03 miles Gateway (360m) Endpoint (1m) Propagation Fading Profile for Test #3 80% LOS (line of sight) 10% NLOS (non-line of sight) 10% Obstructed
- 23. XR Mode Range Test #4 23 Hardware STMicro Discovery Kit (SX1276) with external dipole TX Power 17 dBm Environment Mountain and Valley Gateway Elevation 1170 m / 3838 feet Endpoint Elevation 1 m / 3.3 feet Results best range: 57 km / 35.9 miles Gateway (1170m) Endpoint (1m) Propagation Fading Profile for Test #4 93% LOS (line of sight) 6% NLOS (non-line of sight) 1% Obstructed
- 24. XR Mode Range Test Conclusions 24 Gateway (1170m) Endpoint (1m) Gateway (360m) Endpoint (1m) Gateway (5m) Endpoint (1m) Gateway (1m) Endpoint (1m) 1 km 1.77 km 27.5 km 57 km • Increasing gateway elevation has a major impact in improving range, because it increases the amount of the link that is Line of Sight. • LOS (Line of Sight) portions are shown in green. • The ground itself is a major cause of signal fading (attenuation). This is NLOS (Non-line-of- Sight) and is shown in orange. ‣ Visible light (~566,000 GHz) is a much higher frequency than LoRa (0.9 GHz). ‣ Lower frequencies can travel further, but they have a larger wavefront that is more effected by the ground. • Obstructions cause even more attenuation of the link. Obstructions are shown in red.
- 25. Antenna Design & Placement • Gateway antenna placement makes a huge difference when optimizing for range. • Nearly all LPWAN range tests with very long range claims (e.g., 10 miles+) use a combination of: 1.High-gain antennas located very high above the ground, 2.Data rates that are too low to be suitable for low-power devices 3.Very sophisticated receiver hardware. ‣ Haystack XR Mode outperformed these systems despite being tested with higher data rate, simple antennas, and low cost, low-power receivers • Even a small increase in gateway height can make a significant difference in range performance. In recent testing, the average difference between 2 meters and 5 meters was nearly 200%. • At these extreme sensitivities, it becomes very important to minimize electromagnetic noise generated in the electronics. This is an engineering challenge. STMicro’s LoRa dev kit, for example, is way too noisy. We needed to isolate the antenna in order to conduct the tests. 25 Option A Option B Guess which gateway option results in better range?
- 26. Final Thoughts • Haystack enables not just the longest range LoRa connectivity available today, but also the most reliable and the lowest power. • Few LPWAN networking stacks appear to have been designed for mobile use cases as most are only found being applied to fixed use cases and leave developers to “hack” mobile solutions or ignore them altogether. LoRa’s utility in mobile use cases is limited without robust two-way error correction and other features like multicast. Haystack XR Mode is directly targeted to mobile developers. • Haystack is offering XR mode demo software to a limited number of beta testers. Register here: http://bit.ly/XRModebeta. • Contact us: [email protected] 26