LoRaWAN Satellite Architecture:Components,Advantages,Challenges

Introduction: LoRaWAN is a low power and wide area networking technology developed to support IoT applications. It uses terrestrial gateway and base stations to communicate with distributed end nodes. To extend its coverage in remote and inaccessible areas, LoRaWAN is being merged with existing satellite communication systems. This integrated LoRaWAN-Satellite system helps to provide seamless connectivity in regions where traditional cellular or optical fiber infrastructure is not feasible such as forests, oceans etc.

LoRaWAN Satellite Architecture

Before we explore LoraWAN and Satellite fusion, let us understand basic architecture of satellite IoT system. As shown in the figure, it consists of following five elements.

1. IoT/M2M data acquisition systems : These systems collect environmental or industrial data from connected sensors or machines in remote areas. These collected data are transmitted to satellite directly or via gateway or VSAT terminal.
2. Satellite terminals and/or gateways : These act as local uplinks to the satellite, aggregating sensor data and transmitting it to the satellite. In some cases, gateways also support LoRaWAN or cellular backhaul before routing via satellite.
3. Satellite networks : This includes LEO or GEO satellites that relay data from ground terminals to central ground stations. The satellite provides wide coverage, especially in remote or infrastructure poor regions.
4. Ground networks : These are terrestrial stations that receive data from satellites and route it to the appropriate data centers or cloud based servers. They often include satellite dishes, routers and control systems.
5. IoT application servers : These cloud or enterprise hosted servers process, analyze and visualize the received IoT data. They provide dashboards, alerts and integrations for end users and decision making platforms.

Figure-1: LoRaWAN Satellite network Architecture

LoRaWAN Satellite Network Implementation

There are two approaches of integrating LoRaWAN network with the satellites. Let us understand working of both of these methods.

1. Direct to Satellite LoRa : In this mode, LoRa end devices communicate directly with LEO satellites. This mode works when satellites used carry LoRa compatible payloads. This LoRa capable satellites act as LoRaWAN gateway in space orbit. This scenario does not require LoRaWAN gateway in the architecture. Let us understand data processing involved in the uplink/downlink directions.

• Uplink Processing : End devices (LoRa sensor or nodes) sent data directly to LEO satellites having LoRa compatible payload. The uplink communication uses UHF band (400-470 MHz or 433-450 MHz) and Sub-GHz ISM bands. There are different ISM bands allocated to various countries. EU uses 863-870 MHz, US uses 902 to 928 MHz and Asia uses 865 to 867 MHz frequencies.
• Downlink Processing : The data is directly sent down to the LoRaWAN nodes or end devices by LEO satellites in these same frequency bands. These modulated data are received often with directional antennas. The received packets are time synchronized to match LoRaWAN class A or B receive windows.

Figure-2: LoRaWAN Satellite Connectivity Modes

2. Relay via terrestrial Gateways to satellite : In this mode, LoRaWAN gateway collects the data from LoRa End devices/sensors. The collected data is relayed to the traditional satellites with the help of satellite modem interfaced with LoRaWAN Gateway.

Let us understand data processing involved in the uplink/downlink directions.

• Uplink Processing : In this case, LoRaWAN end devices/nodes send data to terrestrial LoRaWAN compatible gateway. The gateway is interfaced with non-LoRa satellite modem. This traditional satellite modem send data to the satellite (LEO or GEO based on use case). LoRaWAN end devices or sensor nodes communicate on LoRa frequency with terrestrial gateway in ISM bands EU868, US915, AU915, AS923, IN865, KR920 etc. Check exact frequencies as assigned by LoRa Alliance. The received packets are aggregated by LoRaWAN Gateway. Traditional satellite modem receives data from Gateway and are uplinked to the satellite after necessary RF frequency up conversion. Ground gateway and satelite communicate in various frequency bands such as L-band, S-band, ku-band etc.
• Downlink Processing : In the reverse direction, satellite sends data to the ground station based gateway in various bands such as L-Band, Ku-Band, Ka-band etc. In this mode of architecture, the satellite connectivity is independent of the LoRaWAN protocol and handled by a satellite modem/router.

Advantages of LoRaWAN-Satellite integrated System

Following are some of the benefits of LoRaWAN-Satellite integrated approach.

1. The system offers IoT connectivity even in the most remote or maritime areas.
2. Maintains LoRaWAN’s key feature of low power usage, enabling long battery life for end nodes/devices.
3. Reduces the need for costly terrestrial infrastructure.
4. Operates independently of local infrastructure, making it ideal for emergency and disaster scenarios.
5. Supports a wide range of applications from environmental monitoring to maritime tracking.

Challenges in Deployment of LoRaWAN integration with Satellite System

Following are implementation related drawbacks or challenges being encountered during deployment of LoRaWAN along with LEO/GEO satellite network.

1. Due to limited bandwidth in LoRaWAN; it offers low data rate, which is further constrained in satellite applications.
2. Store and forward mechanisms in satellite links can introduce significant delays. This is due to higher latency in GEO orbiting satellites.
3. Different countries have varying rules for satellite based IoT communications.
4. Not all LoRaWAN end devices can communicate effectively with satellites without hardware adaptation.
5. Ensuring end to end encryption and data integrity across satellite links is critical.

LoRaWAN Chipset and Equipment Manufacturers

Following are popular companies being involved in manufacturing of LoRaWAN compatible chipsets, modules and equipments.

Conclusion: It is recommended to use both direct and indirect modes together to avail benefits of both in LoRaWAN-Satellite integrated network. Moreover when both modes are used, if one mode is not available or fails, the other mode provides the LoRaWAN connectivity to the LoRaWAN end nodes or sensors or devices.