# Study of Data Transfer in a Heterogeneous LoRa-Satellite Network for the Internet of Remote Things
## 1 Introduction  
The task of deploying data collection networks in regions without any existing infrastructure poses a number of challenges for engineers. With the Internet of things (IoT) spreading its influence in cities and their suburbs, it is still an open question of how IoT can further extend in regions such as the Arctic or Antarctic, unpopulated deserts or tropical forests. The concept of smart autonomous devices operating in remote undeveloped areas has recently gained its own name--the Internet of Remote Things (IoRT) [1].  
There are a number of IoRT application areas, in which satellite communication (SATCOM) is of primary importance, being the only feasible option of integrating a local data collection system into the global network--shipping, vessel tracking, marine engineering [2], smart grid [3, 4], ecological monitoring, emergency management and medicine [4], earthquakes, flash floods, terrorist attacks and tsunami detection [5, 6], oil and gas industries [7] and backhaul connectivity [3, 8]. Other notable scenarios include the Internet of Underground Things (IoUT) [9], the Internet of Cultural Things (IoT) [10, 11], the Internet of Arctic Things (IoAT) [12, 13] and security and military affairs (the Internetof Battle Things, IoBT) [14; 15]. In general, the organization of ubiquitous internet access using backhaul space communications is discussed in a wide range of research papers [16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31].  
Apart from the obvious technical difficulties related to placing sensors in an unsupervised aggressive environment, the key problems in satellite IoRT are the high cost of sending messages and the occurrence of collisions and significant delays [4; 13; 15; 17; 19; 23; 24] in data acquisition and transmission. As a result, plenty of algorithmic issues are still being researched, with authors presenting new methods of channel access [27; 28; 29], modulation techniques [2; 25], routing mechanisms [17; 23; 29], load balancing [23; 29], data transfer algorithms and protocols [6; 20; 26; 28] and methods of increasing network throughput [19; 31], as well as schemes of reducing power consumption of the network infrastructure [19] and lowering the cost of message transmission [23]. In addition, new architectures [12; 21; 22; 30; 31] of heterogeneous IoT-satellite networks, including the ones based on long range (LoRa) [18; 25; 32] and Iridium [3; 13; 15; 17; 33] have been proposed.  
Energy efficiency remains the main requirement for data transmission in the Internet of things as it directly affects the lifetime of autonomous devices. One of the factors that influence energy efficiency is the amount of transmitted data or the ratio between service data and useful payload. Optimizing such a ratio can be done by changing the existing network algorithms and protocols. In a heterogeneous structure, novel algorithms and approaches can be applied on the edge of the two networks, which is done in our work and which we find as the main distinctive feature compared with other existing approaches.  
We propose an architecture of a hybrid IoT-terrestrial-satellite network and a two-step Gateway Data Encoding and Packaging (GDEP) method for the LoRa-Iridium configuration that transforms a sequence of incoming LoRa Message Queuing Telemetry Transport (MQTT) messages into an output sequence of Protocol Buffers (Protobuf) Short Burst Data (SBD) containers.  
We present our results in the following order: Section 2 contains an overview of related works. Because of the vast array of technologies existing both on the terrestrial side and the satellite side, in Section 3 we first justify our choice of standards and protocols, then present an architecture of a low power wide area network (LPWAN) [34]-satellite network for the Internet of things in hard-to-reach areas. Further on, we describe our encoding and packaging method. In Section 4, we review results of experimental verification of the main hypotheses using semi-natural simulation.