An Overview of LoRA, Sigfox, and IEEE 802.11ah
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The slides provide an insight into different IoT and M2M specific protocols. Their main features and differences are highlighted. Potential research area in IEEE 802.11ah is identified. The slides also identifies the coexistence problem between Lora and Sigfox
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An Overview of LoRA, Sigfox, and IEEE 802.11ah
- 1. AN OVERVIEW OF LoRa, SigFox, and IEEE 802.11ah Faheem Zafari Computer & Information Technology Purdue University faheem0@purdue.edu
- 2. AGENDA • LoRa • SigFox • IEEE 802.11ah • Differences between LoRa, SigFox, IEEE 802.11ah • Use cases • Problem with IEEE 802.11ah • Co-existence problem
- 3. LoRa • Physical Layer LPWAN solution • High range (max 15km), low power, low data rate (0.3- 37.5 kbps), wideband, sub-GHz • The architecture consists of • LoRa end-devices • LoRa Gateways • LoRa Network Servers (NetServer) Taken from Centenaro et al.
- 4. LoRa • The MAC layer is basically ALOHA protocol controlled by the LoRa NetServer. • The LoRa MAC is designed to mimic IEEE 802.15.4 Mac to allow the accommodation of other protocols such as CoAP, 6LoWPAN etc. Taken from Centenaro et al.
- 5. • SIGFOX • First LPWAN technology. • The physical layer uses Ultra-Narrow Band (UNB) wireless modulation. • Network layer protocols are ‘secret sauce’. • Low throughput (~100 bps), low power, extended range (up to 50 km). • The end device must use SIGFOX modem to connect to the SIGFOX network • The device should initiate the communication.
- 6. • IEEE 802.11ah • Physical layer based on 802.11ac. • Low Data Rate (~100kpbs), extended range (up to 1km), low energy consumption, sub-GHz. • One hop network topology. • Supports MIMO, Single user beamforming etc on the Physical layer. • Three different types of stations supported • Traffic Indication Map (TIM): Listens to AP for data transfer • Non-TIM stations: Directly negotiate with AP during association process to obtain transmission time on Periodic Restricted Access Window (PRAW) • Unscheduled Stations: does not listen to any beacons and uses poll to access channels.
- 8. MAIN DIFFERENCES Parameter LoRa Sigfox IEEE 802.11ah Data rate (kbps) 0.3-37.5 0.1 >100 Coverage (km) Rural: 10-15 Urban: 3-5 Rural: 30-50 Urban: 3-10 1 Nodes per BS ≈ 104 ≈ 106 8191 Frequency (MHz) Various, Sub-Ghz 969 or 902 902-928 (US) Initiation Both node and NetServer Device Both device and the AP Energy Consumption Very low low slightly higher Dedicated Network No Yes No
- 9. USE CASES Technology Use Cases LoRa Garbage collection bin fill level for pick up route optimization Sigfox Smart meters, smoke detectors IEEE 802.11 ah Backhaul network for Sensors, Video Surveillance, wearable consumer electronics
- 10. PROBLEM WITH IEEE 802.11ah • As pointed out by Adame et al., a potential challenge in 802.11ah is the performance of Non-TIM and unscheduled stations, and their integration with TIM stations in a single WLAN. The problem is interesting to explore for further research. • The number of stations that IEEE 802.11ah is also much lesser than Sigfox and LoRa.
- 11. COEXISTENCE PROBLEM • One of the problems with the coexistence of Sigfox and LoRa is that, Sigfox is based on UNB sub-GHz while LoRa is wideband sub-GHz. The wideband solution is prone to the interference from UNB technologies. This problem can be interesting to explore for further research.
- 12. REFERENCES • Adame, T., Bel, A., Bellalta, B., Barcelo, J., & Oliver, M. (2014). IEEE 802.11 AH: the WiFi approach for M2M communications. Wireless Communications, IEEE, 21(6), 144-152 • Centenaro, M., Vangelista, L., Zanella, A., & Zorzi, M. (2015). Long- Range Communications in Unlicensed Bands: the Rising Stars in the IoT and Smart City Scenarios. arXiv preprint arXiv:1510.00620. • Centenaro, M., Vangelista, L., Zanella, A., & Zorzi, M. (2015). Long- Range Communications in Unlicensed Bands: the Rising Stars in the IoT and Smart City Scenarios. arXiv preprint arXiv:1510.00620. • Keysight Technology. Explosion of the Internet of Things: What does it mean for wireless devices? June, 2015
Notes de l'éditeur
- Class A defines the default functional mode of the LoRaTM networks, and must be mandatorily supported by all LoRaTM devices. In a Class A network, transmissions are always initiated by the end-devices, in a totally asynchronous manner. After each uplink transmission, the end-device will open (at least) two reception windows, waiting for any command or data packet returned by the Net- Server. The second window is opened on a different sub-band (previously agreed upon with the NetServer) in order to increase resilience to channel fluctuations. Class A networks are mainly intended for monitoring applications, where data produced by the end-devices have to be collected by a control station. Class B has been introduced to decouple uplink and downlink transmissions. Class B end-devices, indeed, get synchronized with the NetServer by means of beacon packets broadcast by Class B gateways, and can hence receive downlink data or command packets in specific time windows, irrespective of the uplink traffic. Class B is intended for end-devices that need to receive commands from a remote controller, e.g., switches or actuators, or need to provide data at user’s request. Finally, Class C is defined for end-devices without (strict) energy constraints (e.g., connected to the power grid), which can hence keep the receive window always open.
- A distinguishing feature of the LoRa MAC is the Adaptive Data Rate, which allows the NetServer to adapt the transmit rate of an end-device by changing the SF index, in order to find the best tradeoff between energy efficiency and link robustness. Another important feature is the strong security mechanisms that entail a network key and an application key, which are set up through an over-the-air activation procedure, as well as an activation by personalization procedure (where the security parameters are set into the device at production time).
- Uses unlicensed spectrum –mostly sub-GHz band and patented ultra narrow band (UNB) communication ( bandwith with the order of 25 KHz) (wideband for LoRa is about 126-250 KHz) •Ultra low throughput -~100 bps -Devicecan send between 0 and 140 messages per day, each message is up to 12 bytes •Up to 20 years of battery life •Long range –up to 30 miles in rural area and 2-6 miles in urban area –Devices require a SIGFOX modem to connect to SIGFOX network –Target applications: smart meter, pet tracking, smoke detector, agriculture etc… –Have networks deployed in France, Netherlands, Russia and Spain; Launching 902 MHz network in San Francisco
- Traffic indication map (TIM) stations This is the only type of station that needs to listen to AP beacons to send or receive data. Their data transmissions must be performed within a restricted access window (RAW) period with three differentiated segments (multicast, downlink and uplink). Stations with a high traffic load should use this procedure to access the channel because it combines periodic data transmission segments with energy efficiency mechanisms. • Non-TIM stations: Non-TIM stations do not need to listen to any beacons to transmit data. During the association process, non-TIM devices directly negotiate with the AP to obtain a transmission time allocated in a periodic restricted access window (PRAW). The following transmissions can be either periodically defined or renegotiated, depending on the requirements set by the station. Although non-TIM stations can transmit data periodically, it is advisable to deploy TIM stations for high-volume data applications to achieve better management of channel resources and benefit from all the improvements developed by IEEE 802.11ah. • Unscheduled stations: These stations do not need to listen to any beacons, similar to non-TIM stations. Even inside any restricted access window, they can send a poll frame to the AP asking for immediate access to the channel. The response frame indicates an interval (outside both restricted access windows) during which unscheduled stations can access the channel. This procedure is meant for stations that want to sporadically join the network. –Target use cases •Large scale low power sensor networks and smart meter •Video surveillance, wearable consumer electronics •Backhaul for aggregated sensor and meter data •Outdoor Wi-Fi for cellular traffic offloading
- Traffic indication map (TIM) stations This is the only type of station that needs to listen to AP beacons to send or receive data. Their data transmissions must be performed within a restricted access window (RAW) period with three differentiated segments (multicast, downlink and uplink). Stations with a high traffic load should use this procedure to access the channel because it combines periodic data transmission segments with energy efficiency mechanisms. These novel features are described in detail below. • Non-TIM stations: Non-TIM stations do not need to listen to any beacons to transmit data. During the association process, non-TIM devices directly negotiate with the AP to obtain a transmission time allocated in a periodic restricted access window (PRAW). The following transmissions can be either periodically defined or renegotiated, depending on the requirements set by the station. Although non-TIM stations can transmit data periodically, it is advisable to deploy TIM stations for high-volume data applications to achieve better management of channel resources and benefit from all the improvements developed by IEEE 802.11ah. • Unscheduled stations: These stations do not need to listen to any beacons, similar to non-TIM stations. Even inside any restricted access window, they can send a poll frame to the AP asking for immediate access to the channel. The response frame indicates an interval (outside both restricted access windows) during which unscheduled stations can access the channel. This procedure is meant for stations that want to sporadically join the network. –Target use cases •Large scale low power sensor networks and smart meter •Video surveillance, wearable consumer electronics •Backhaul for aggregated sensor and meter data •Outdoor Wi-Fi for cellular traffic offloading