- freely available
Sensors 2016, 16(9), 1466; doi:10.3390/s16091466
1.1. Related Work
- Low power local area networks with a less than 1000-m range. This category includes IEEE 802.15.4, IEEE P802.1ah, Bluetooth/LE, etc., which are applicable directly in short-range personal area networks, in body area networks or, if organized in a mesh topology, also in larger areas.
- Low-power wide area networks, with a greater than 1000-m range, essentially low-power versions of cellular networks, with each “cell” covering thousands of end-devices. This category includes LoRaWAN, but also protocols, such as Sigfox, DASH7, etc.
1.1.3. IEEE 802.11 ah
1.2. Statement of Purpose
2. LoRa Overview
2.1. LoRa Protocol Stack
2.2. LoRa Network Architecture
3. The LoRa Physical Layer
3.1. Overview of the Physical Layer
3.2. Parameters of the Physical Layer
3.3. Physical Frame Format
3.4. Performance Evaluation
3.4.1. Receiver Sensitivity
3.4.2. Network Coverage
4. The LoRaWAN Protocol
4.1. Components of a LoRaWAN Network
- End-device: the low-power consumption sensors that communicate with gateways using LoRa.
- Gateway: the intermediate devices that forward packets coming from end-devices to a network server over an IP backhaul interface allowing a bigger throughput, such as Ethernet or 3G. There can be multiple gateways in a LoRa deployment, and the same data packet can be received (and forwarded) by more than one gateway.
- Network server: responsible for de-duplicating and decoding the packets sent by the devices and generating the packets that should be sent back to the devices.
- Class A, bi-directional: Class A end-devices can schedule an uplink transmission based on their own needs, with a small jitter (random variation before transmission). This class of devices allows bi-directional communications, whereby each uplink transmission is followed by two short downlink receive windows. Downlink transmission from the server at any other time has to wait until the next uplink transmission occurs. Class A devices have the lowest power consumption, but also offer less flexibility on downlink transmissions.
- Class B, bi-directional with scheduled receive slots: Class B end-devices open extra receive windows at scheduled times. A synchronized beacon from the gateway is thus required, so that the network server is able to know when the end-device is listening.
- Class C, bi-directional with maximal receive slots: Class C end-devices have almost continuous receive windows. They thus have maximum power consumption.
4.2. LoRaWAN Message Format
4.3. End-Device Setup
- End-device address (DevAddr): A 32-bit identifier of the end-device. Seven bits are used as the network identifier, and 25 bits are used as the network address of the end-device.
- Application identifier (AppEUI): A global application ID in the IEEE EUI64 address space that uniquely identifies the owner of the end-device.
- Network session key (NwkSKey): A key used by the network server and the end-device to calculate and verify the message integrity code of all data messages to ensure data integrity.
- Application session key (AppSKey): A key used by the network server and end-device to encrypt and decrypt the payload field of data messages.
4.4. LoRaWAN MAC Commands
5. LoRaWAN Analysis
5.1. Single Device Maximal throughput and MTU
5.2. Total Capacity and Channel Load
5.3. Estimation of the Collision Rate
5.4. The Network Server Role
5.5. The Gateway Role
Conflicts of Interest
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