Light Hotspots Software Upgrade [Updated]

This document describes the architecture and technical roadmap planned for converting existing Approved Hotspots to Light Hotspots as a software upgrade; updated with HIP70 in mind, should it pass.

The conclusion of the Light Hotspot project is in progress. Last updated Friday September 16, 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? [Updated]

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.

Before the introduction of HIP 70, the goal was to move Challenge creation and Consensus work to Validators. Since HIP-70 and the introduction of Off-Chain PoC Oracles, the definition of Light Hotspot and what it will do has changed. Please read on for detailed changes and timelines.

Light Hotspot Properties [Updated]

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

• A Hotspot on the Helium network will Beacon (also known as emitting a challenge for Proof-of-Coverage) automatically on a pre-determined time interval (up to several times a day);
• Will submit PoC receipts directly to an Off-Chain PoC Oracle;
• Does not store a copy of the Blockchain, eliminating synchronization;
• Will transmit packets on behalf of IoT devices on the network to an Off-Chain Data Oracle;
• Does not participate in Consensus Groups;
• 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 Proof-of-Coverage receipts to an Oracle. At the conclusion of Light Hotspot development, the entire Helium blockchain will be removed from Hotspots, Hotspots will Beacon on their own without external input, and all data transfer and Proof-of-Coverage receipts will go to Off-Chain Oracles.

HIP-70 Changes

HIP-70 proposes a new architecture that involves several Oracles that allow Proof-of-Coverage generation to be automated and its receipts to be off-chain. The most "expensive" piece of Proof-of-Coverage is not just Challenge creation, but Receipt validation and verification. By taking these tasks off-chain, PoC frequency can increase dramatically, up to several times a day. Hotspot owners can expect more reliable challenges and witnessing.

The core team has started work on these Oracles. Roughly speaking, a Hotspot will Beacon on its own, with neighboring Hotspots witnessing and submitting their receipts to an Ingestor Oracle. The Ingestor** uploads receipts into a cloud store where another Oracle, called a Verifier runs through the files to filter out invalid receipts. The output of the Verifier is passed to a Reward Oracle that determines how much reward shares a Hotspot should earn for that period. Finally, Hotspots are rewarded for their work in Proof-of-Coverage.

For this to happen, two blockchain-related pieces must complete:

1. The launch of the IOT Subnetwork as described in HIP-52
2. The passing of HIP-70 and the completed transition to a new L1

To avoid further delays, the core team believes the work for Off-Chain PoC has progressed enough to allow an intermediate step that allows Hotspots to remove the Erlang miner, have Hotspots beacon at a more frequent interval, and remove PoC off chain.

The change to complete Light Hotspot will be at the Reward Oracle step. Instead of the Verifier submitting its Proof-of-Coverage results to the Reward Oracle, all Proof-of-Coverage receipts will be signed and submitted to the Helium L1 Blockchain where rewards will be paid out in HNT (as they are today) by a new Oracle called the Injector. This removes the need for the IOT Subnetwork to exist and removes the dependency of the L1 switchover.

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.

Oracle work can be found at the Oracles repository.

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
• September 2022:
• Introduction of HIP-70, Off-Chain Oracles, and Hotspots transferring data, and Challenging more reliably
• Continuing Oracle Work and beta gateway-rs builds to allow Hotspots to Beacon on a regular interval and send its receipts to a Devnet Oracle for further receipt processing
• ~November 2022: Should HIP-70 pass, the completion of Light Hotspots with the launch of PoC Oracles, Data Transfer Oracles, and a final gateway-rs build to remove the Erlang miner