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Direct-to-Gateway, Direct-to-Device, Direct-to-cell
Direct-to-Gateway
Direct-to-Gateway (Terminal) is the most common method of connecting devices to a satellite. This scheme is used when various sensors and terminal devices measure parameters such as temperature, pressure, gas content, humidity, vibration, radiation, light, and acceleration, but do not have a direct connection with the satellite. Instead, they transmit data to the terminal through various interfaces such as Ethernet, Bluetooth, NFC, or Wi-Fi. The terminal then processes the data using its own components. They transmit data to the terminal through various interfaces, such as wired (Ethernet) and wireless (Bluetooth, NFC, Wi-Fi). The terminal already has components, such as modulators, power amplifiers, controllers, and antennas, to generate and emit radio signals for satellites. Terminals, also known as nodes, base stations, gateways, subscriber receiving and transmitting devices, receiving and transmitting modules, have no direct connection with the satellite. In this context, a terminal forms a mini-network with its sensors. This network can operate within a range of units to hundreds of metres, and even kilometres.
The scheme serves various locations such as settlements, residential buildings, schools, hospitals, cafes, logistics hubs, warehouses, enterprise workshops, quarries, mines, substations, well pads, car service stations, and grain elevators. It can also serve mobile objects such as ships, trains, airliners, and cars.
Direct-to-Device (D2D)
The miniaturisation, cost reduction, and standardisation of components has resulted in small sensors being transformed into separate terminals the size of a matchbox. These terminals are capable of generating radio signals that can recognise satellites in orbit. This technology is known as Direct-to-Device. Although many satellite operators claim to use it, individual sensors are rarely connected directly to a satellite. There are examples of smart bracelet trackers for animals and small-sized trackers for UAVs, but these are essentially mini-terminals. Therefore, working directly with sensors is a technological variation for satellite IoT systems, following the usual Direct-to-Gateway (Terminal) scheme. However, in the statements of operators, it is more of a marketing ploy. The concept of edge computing involves shifting computations and data processing to the front edge, specifically to sensors, in order to avoid overloading higher ranked network nodes, including satellites. This is because traffic volume increases as devices get closer to the end. Short-range ecosystems and last-mile devices generate vast amounts of global traffic every day. For example, dozens of car sensors communicating with a central computer, a laptop’s external storage, and sensors inside a smart home. It is essential to adhere strictly to metrics and units when measuring this traffic. When we hear about data transmission from billions of Bluetooth devices to satellites, such as the system proposed by US startup Hubble Networks, it is important to consider factors such as the business model, capacity, and target customers.
Direct-to-cell
Direct-to-cell technology is a popular and promising topic in the satellite industry. It enables a direct connection between a satellite and a smartphone without the need for intermediary devices such as wearable terminals or routers. This is particularly relevant given the projected growth of smartphones, with an estimated 4.3 billion in use worldwide by 2023 (GSMA).
Experts often discuss the potential of technology, including its risks, and support their claims with statistics. For example, if we assume that 500 million people worldwide are willing to pay $1.5 per month for global communication and an additional $10 for connection, the total market volume would be $9 billion per year. Despite the absence of the need to develop, produce, promote, and sell special additional satellite phones, trackers, base stations, and routers for users, the idea is still tempting and attracts major players. Global partnerships such as Globalstar-Apple, Starlink-T-Mobile, AST-Mobile-Google, Lynk Global, Kuiper, Lightspeed (TELESAT), and Guowang are developing technological opportunities and business models. Starlink is already testing a direct communication service for thousands of users, supported by up to 840 satellites on LEO-VLEO. It is important to note that the language used in this text is neutral and free from personal bias or opinion.
Varieties of Direct-to-cell
A )IRIDIUM, Globalstar, and ECHOSTARMOBILE are satellite communication providers that offer additional devices, which act as intermediaries between smartphones and satellites. These devices are mini-satellite phone modems. Although not Direct-to-cell, there is already a market for such services that emerged with the first smartphones.
B) Direct-to-cell communication can be achieved by modifying a serial smartphone. This involves adding a transceiver module and antenna to establish a connection with a satellite. The modification does not significantly alter the appearance, weight, or maximum power of radiation of the smartphone. Apple has adopted this approach with the release of the I-Phone 14 in 2021, which supports SOS messages via GLOBALSTAR satellites. IRIDIUM and Qualcomm attempted to create a chipset for Android smartphones. However, it seems that Android smartphone manufacturers either develop their own chipsets, which is typical of the Chinese strategy, or wait. Currently, Qualcomm has put this project on pause.
C) The smartphone should be able to function on both cellular and satellite networks without any modifications to its hardware. This will save smartphone manufacturers from incurring additional costs on separate electronics. It appears that the developers may not be truthful and modifications may be necessary. Additionally, there may be hidden components inside smartphones. However, this mainly affects the cost of development and mass production of such modules, with the design of the system-on-chip alone costing up to $1 billion. The market’s reaction is currently being observed. There is no doubt that these business models and technologies will emerge. The question is who will lead the way. A smartphone connected to NTN networks will be the core of the future ecosystem. This ecosystem will include internet phones, sensors in clothing, shoes, personal items, gadgets, and even inside the human body. It is possible that in the future, smartphones will become distributed, with functionality shared across the entire ecosystem. This could mean that people will no longer need to physically hold anything in their hands, as antennas and microelectronics will be sewn into clothing and images will be projected. Connecting to this ecosystem could allow satellites to transmit data about humans and their immediate environment, as well as the objects they visit. However, it is important to consider that certain parameters in industrial facilities, forests, agricultural lands, ocean coasts, etc. may require monitoring even if they are not frequently visited by people. This is a classic example of IIoT (Industrial Internet of Things) or M2M (Machine-to-Machine) communication. It involves the interaction between physical objects such as machines, mechanisms, robots, UAVs, and cars, and control centres. It is important to note that data transmission cannot be done through a person’s smartphone.
