This document describes the architecture and technical roadmap planned for converting existing Approved Hotspots to Light Hotspots as a software upgrade. As part of this migration, we have introduced a new Hotspot variant onto the network, called a Data Only Hotspot.

A conversion of a Full Hotspot running Light Hotspot software is now being tested on Testnet.

This project is in progress and subject to change. Last updated Monday April 12, 2022.

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For real-time development and community support of Data Only Hotspots and Light Hotspots, please join the #gateway-development channel on Helium Discord

What is a Light Hotspot?

Light Hotspots are the evolution of how LoRaWAN gateways will interact with the Helium blockchain. Since the genesis block, the Helium blockchain has run entirely on the physical Hotspot itself. As the blockchain network grows, each Hotspot running a full node undergoes increasing load and are starting to fall out of sync due to the higher compute requirements.

To mitigate this, the Hotspot's consensus work has been moved off of physical Hotspots and onto Validators. This simplifies the architecture and enables us to grow the Network exponentially while keeping blocktimes and epochs stable.

As all approved Hotspots transition to a Light Hotspot architecture, we also introduce a new type of Hotspot known as Data Only Hotspots, to satisfy the increasing demand and continue to expand network coverage.

Rewards Type	Data Only Hotspots	Full & Light Hotspots
Network Data Forwarding	YES	YES
Proof of Coverage	NO	YES

Light Hotspot Properties

When the Light Hotspot software is fully developed and in production, they will satisfy the following properties:

• A Hotspot on the Helium network that, via Validators, can participate in PoC beacons and witnesses, and forwards data packets;
• Does not store a copy of the Blockchain, eliminating synchronization;
• Does not create challenges (relies on Validators to create challenges on their behalf);
• Does not participate in Consensus Groups (relies on Validators for block production);
• Will no longer depend on libp2p or "gossip", and instead use gRPC, a new framework to communicate between distributed systems;
• Will be eligible to earn $HNT (see table below)

In other words, the Light Hotspot software will allow the Hotspot to participate as a Full Hotspot, without the extra overhead of maintaining a local copy of the blockchain.

Architecture

This image shows the progression to Light Hotspots, with the role of Miner being deprecated as we move the blockchain off the Hotspots and into the Validator infrastructure. At the conclusion of Light Hotspot development, the entire Helium blockchain, and the coordination of Proof of Coverage, will be handled by Validators.

Code and Development

The bulk of the code that enables Light Hotspots on actual LoRaWAN gateways is called gateway-rs. It's easiest to think of this as Helium's next-generation packet forwarder.

Development of this code takes place in the above GitHub repo, as well at the #gateway-developement channel on the Helium Discord Server.

Development Timelines

• March 18 2021: Data Only Hotspots routes free packets
• July 8 2021: Hotspot Consensus work moves to Validators
• July 20 2021: Data Only Hotspots activated on Helium Network (appears on chain)
• October 11 2021: Data Only Hotspots mine HNT
• December 2021: Validators creating challenges for software-based miners on Testnet
• January 2022: Hardware Audit starts for Light Hotspot manufacturers
• February 2022: Introduce hardware-based Hotspots on Testnet (Full Hotspots running Light Hotspot firmware). Validators create challenges using H3dex targeting.
• February 22 2022: HIP 54 and HIP 55 passes
• February 2022: HIP-19 Approved Makers participating in Testnet
• April 6 2022 April 13: Code related to Light Hotspot merged to production, in an inactive state. Light Hotspot software update tagged for Makers to upgrade their fleet. Validators will also receive a mandatory software update.
• April 19 2022 May 11: Activate set of chain variables to enable Light Hotspots on Mainnet
• Several weeks later: Deactivate Miner on Light Hotspots on Mainnet such that they run gateway-rs only

Current progress on Testnet

Hotspots on Testnet running Light Hotspot software are now participating in a new Proof-of-Coverage with Validators. In this test, all Hotspots use Testnet Validators for blockchain information and do not need to sync the blockchain directly. They also receive PoC Challenges from the Validator pool.

You can see their progress on Testnet.

These Hotspots are also running a dockerized version of gateway-rs (rust-based gateway firmware) and an updated packet forwarder that relies on Validators.

Note that these Hotspots are earning testnet tokens (TNT) and not HNT.

Current progress on Mainnet

A portion of the complete Light Hotspot software is also on mainnet, transferring non-PoC packets on a test Hotspot using the new packet forwarder that relies on Validators.

What's Next

Merge code related to Light Hotspots to mainnet, in an inactive state.