Blockchains in Space: The Internet of Things Will Run on a LEO Satellite Network TLM Follow Feb 27, 2018 · 6 min read

Dr. Wei Songjie, Waltonchain’s Chief Blockchain Expert, has devised a way to implement a global anywhere-internet in Low Earth Orbit (LEO) satellites with the help of blockchain technology in order to create a world hub for Internet of Things devices.

Right now, you connect to the Internet via wires, Fiber Optic cables, WiFi, or cell towers (eg. 4G). And then there’s the uncommon, less-than-satisfactory GEO satellite internet. GEO satellites, or Geosynchronous satellites, are satellites that have the same orbital period as Earth’s rotation period, that is, they’re in sync with Earth’s rotation so that they appear stationary in the sky. To achieve that, GEO satellites must be around 36000 km (~22000 miles) above sea level, and they must orbit near the equator to match Earth’s spin. Internet comes at a cost. The signals to and from the satellites must travel very far, and the consequences are frustrating:

High latency (delay between instruction and action) — the time it takes to send a signal is considerable (about 120ms one way), and therefore is not suitable for applications such as real-time audio/video, gaming, etc.

(delay between instruction and action) — the time it takes to send a signal is considerable (about 120ms one way), and therefore is not suitable for applications such as real-time audio/video, gaming, etc. Low data caps — there are only a few satellites in GEO orbit, and many users

— there are only a few satellites in GEO orbit, and many users Weak signal — it’s too far away. This requires more advanced processing algorithms and equipment for amplification, which is expensive, and the price is passed onto the user

— it’s too far away. This requires more advanced processing algorithms and equipment for amplification, which is expensive, and the price is passed onto the user Poor coverage near the poles — GEO orbit is near the equator and difficult to broadcast to the poles

But there is one advantage. Since the satellites are locked with the Earth and don’t appear to move, a user can sustain a connection with the same satellite indefinitely. This contrasts with LEO satellites (Low Earth Orbit), which are much closer to the Earth (~800 km above sea level), and must move very quickly relative to Earth’s surface to stay in orbit. As a result, a LEO satellite makes a full trip around the earth in about 100 minutes, and so any single satellite is only in view of a user for about 10 minutes at a time.

Iridium LEO satellite grid

In order to maintain connectivity, the satellites have to handover the connection to an adjacent satellite to link to you, and they’ll have to do this at least every 10 minutes or the connection will be dropped.

Take the Iridium Constellation (above), for example. It is a network grid of 66 LEO satellites around the earth. You can use an Iridium satellite phone to make calls over this network, which will allow you to connect to anyone from anywhere. However, calls lasting longer than 5 minutes will on average require at least one satellite switch. Authentication is slow and costly, and performance is bottlenecked through the nearest centralized land base, and the spot beams of the satellites only overlap so much, so there is limited time to make the switch in connection from one satellite to the next. In order to handover the connection to another satellite, the satellite has to verify and authenticate the user’s information, and since the traditional methods are time-consuming and costly due to high computational overhead, combined with having to handover frequently, there is a high failure rate, and switching will often result in a dropped call. Furthermore, in order to switch satellite links, a soft handover is usually employed. This means the user will be connected to two satellites simultaneously during authentication and transfer of information before the first satellite disconnects and exits view of the user. Connecting a user to multiple satellites at a time bogs down the network and reduces the capacity of the network. In addition, calls can be easily intercepted because the connections are not secure.

Intersatellite handover

This is where blockchain comes in.

Dr. Wei Songjie has patented an invention that allows for fast-switching between satellite links via a distributed access authentication management system in a LEO satellite network. The invention uses a combination of blockchain to store user information in blocks and Identity-Based Cryptography for secure and quick authentication and verification.

The simplified explanation of the process is as follows:

The user registers their identity information and the Key Generation Center of the device generates a public and private key pair and stores the user information in a user block in the blockchain. Each satellite also has its own Key Generation Center and its own public and private key pair. The user and the satellite exchange, calculate, and verify each other’s private keys to generate session keys that are secure, and the satellite verifies the user’s identity which is stored in the blockchain for access and handover authentication. This involves low computational overhead and involves communication only between the user and the satellite. As such, the authentication is completely secure and decentralized, avoiding the performance bottleneck of centralized authentication, and it can be done in just several milliseconds. The user is verified and authenticated during every switch and the information is propagated through the satellite network and stores all of the user registration, login, logout, and switching information on the blockchain.

This means the satellites can achieve fast-switching of secure connections, while simultaneously and reliably logging all information onto the blockchain. It’s important to remember that a user in these examples doesn’t necessarily mean a human being. IoT devices can register and secure a connection with the network for constant data feed into the blockchain from anywhere on earth, at any time, with low latency, low cost, and with a reliable, secure connection.

As a bonus, Dr. Wei also patented an improved algorithm for self-adaptive routing in a LEO satellite network, published in May 2017, only days after the aforementioned authentication patent. Let’s say you want to connect with another user across the globe. Traditionally, the satellites will hop the signal through adjacent satellites to reach the user, and the signal travels the shortest distance with the fewest number of hops. This of course creates hot spots through certain satellites and congests the network. By increasing the number of hops and creating a network that can sense the network load and self-adapt, the load difference between satellites in the network can be reduced by over 50%, increasing the network capacity and reducing congestion and queues.