# MOBILE Proof of Coverage

## Introduction​

The Helium blockchain uses a novel work algorithm called "Proof of Coverage" ("PoC") to verify that Hotspots are located where they claim. Put another way, PoC tries to verify, on an ongoing basis, that Hotspots are honestly representing their location and the wireless network coverage they are creating from that location.

While current 5G Hotspots are also able to participate in the IOT Network and PoC, the CBRS Small Cell and 5G aspects of a 5G Hotspot require a new approach to validating PoC.

Modeled Coverage introduces a fundamental difference in using hexes for the MOBILE Network compared to the IOT Network where hexes determine the locations and number of Hotspots within the given hex. In the MOBILE Network, hexes determine where the coverage exists. Modeled Coverage data allows us to un-tie a Radio's location from its signal strength and propagation.

One Way Traffic

A CBRS Small Cell Radio ("Radio") can only operate as a transmitter; they cannot receive incoming data and thus can not "hear" one another directly.

LoRaWAN Hotspots utilize a PoC method that benefits from Hotspots being used as senders ("Beacon") and receivers ("Witness") of PoC activity; read more here: Proof of Coverage

## Proof of Coverage Milestones​

Determining useful coverage and the impact on MOBILE PoC rewards will be based on a number of factors:

These factors will be rolled out in stages over the next twelve months and explained in detail to ensure Network Builders can take concrete steps to plan or improve their setups. Check out the MOBILE PoC Roadmap here.

## Reward Algorithm​

The proposed new algorithm for MOBILE Reward calculation in the MOBILE Rewards Oracle is as follows:

1. Supply the declared transmitter power of each Radio and its location to the Obstruction Data Oracle.
2. Get all hexes that have coverage from Outdoor Radios based on the information from the Obstruction Data Oracle.
3. Based on the location of Indoor Radios, get all hexes with Indoor coverage and all adjacent hexes.
4. Use projected signal loss information from the Obstruction Data Oracle to determine the potential signal strength of each Outdoor Radio in each hex.
5. For each hex, get at most 5 Outdoor Radios with the top signal strength of the same level.
• If there are more than 5 Radios with the same signal strength level, use the coverage_claim_time value to determine the top 5 oldest installations where coverage_claim_time is the timestamp when the Radio received the spectrum access grant for the first time.
• To prevent rewarding "dead" Radios, we propose to reset coverage_claim_time if the Radio was not generating a Heartbeat for more than 72 hours and use the time of the last Heartbeat as the new coverage_claim_time.
1. Get max 5 Indoor Radios using the same approach as above for Outdoor Radios.
2. Based on Modeled Coverage Reward Tiers, sum up all estimated coverage points earned by each Radio in all hexes and multiply that by speedtest_multiplier for each Radio.
3. Divide the total number of MOBILE Rewards emitted during the Rewards Period by the sum of multiples of heartbeat_multiplier, estimated_reward_points, and speedtest_multiplier for each Radio to determine MOBILE Rewards per estimated_reward_point for Radio with a passing Speed Test and valid Heartbeats.
4. Multiply the MOBILE per estimated_reward_point by the sum of each Radio's reward points to determine the MOBILE Rewards for each Radio.

The new formula for Reward calculation per Radio:

$W = k_H \times k_S \times C_E \times W_p$
VariableDescription
$W$Total rewards
$k_H$Heartbeat multiplier
$k_S$Speedtest multiplier
$C_E$Estimated coverage points
$W_p$Epoch rewards per coverage point

### Calculation Example​

For simplicity, assume that the total MOBILE Rewards per period is 10,000.

RadioHeartbeatHeartbeat multiplier $k_H$Speed TestSpeedtest Multiplier $k_S$Hex 1 - Hex 10Hex 11 - Hex 20Hex 21 - Hex 220Total Coverage PointsTotal Reward Points
1 (Outdoor)Ok1Acceptable1160808001,0401,040
2 (Outdoor)Ok1Poor0.25804012030
Points1,070

Table 3. Simplified data for two Outdoor Radios with Heartbeat, Speed Test, and Estimated Coverage Points for one Reward Period.

RadioHeartbeatHeartbeat multiplier $k_H$Speed TestSpeedtest Multiplier $k_S$Hex 1Hex 2Hex 3Hex 4Total Coverage PointsTotal Reward Points
Points350

Table 4. Simplified data for one Indoor Radio with Heartbeat, Speed Test, and Estimated Coverage Points for one Reward Period.

$R \times (1 \times 1 \times 1040 + 1 \times 0.25 \times 120 + 1 \times 0.5 \times 700) = 10,000$

Where R is the reward per one estimated coverage point.

$R = 6.54$
CalcuationTotal MOBILE Rewards
Radio 1 (Outdoor)6.54 x 1 x 1 x 10406,806.30
Radio 2 (Outdoor)6.54 x 1 x 0.25 x 120903.14
Radio 3 (Indoor)6.54 x 1 x 0.5 x 7002,290.58

## Modeled Coverage​

With the passing of HIP-74 Modeled Coverage aims to allow for more appropriate Rewards and incentivizes the deployment of Radios at optimal locations.

This new algorithm uses the location of the Radio to calculate MOBILE Rewards based on the number of res12 hexes receiving coverage from a given Radio.

The MOBILE Rewards Oracle will calculate a coverage model for each Radio by considering the physical location, antenna direction, radio max transmit power, and Obstruction Data Oracle inputs to calculate the number of res12 hexes receiving coverage from each Radio.

Depending on the number of res12 hexes and the resulting signal power in each, the MOBILE Rewards Oracle will allot Coverage Points to a given Radio for calculating its MOBILE Rewards instead of assuming a fixed Radio Type multiplier Reward.

### Reward Hexagon Sizing​

Analysis of the coverage by a single Outdoor Radio with Modeled Coverage data shows that the res8 hex used in the IOT Network is too large to represent a Radio's coverage. Using res12 hexes better aligns with what an Outdoor Radio can reasonably cover, with an average area of 0.0003071 km² and an edge length of 9.4 m, slightly bigger than an average single-family home.

To summarize:

• Hexes in the MOBILE Network identify the level of coverage from all the different Radios providing coverage to each res12 hex.
• A Radio can provide coverage for a hex it is not located within.
• A Radio can earn Rewards by providing coverage in multiple hexes.

To help visualize the significant difference between these two resolutions, below is a map with a green res8 hex and a purple res12 hex inside.

### Modeled Coverage Reward Tiers​

info

Each Radio is given a coverage points value depending on the number and signal strength of the res12 hexes receiving coverage from the Radio.

Modeled Coverage replaces Radio Type multipliers with coverage points represented by four tiers of potential signal power as modeled by the Obstruction Data Oracle - High, Medium, Low, and None.

The reward tiers for Outdoor Radios will be as follows:

Tier 1Tier 2Tier 3Tier 4
Potential Signal Power$P > -95 dBm$$-95 dBm \ge P > -105 dBm$$-105 dBm \ge P > -115 dBm$$P \le -115 dBm$
Potential Signal LevelHighMediumLowNone
Estimated coverage points16840
Modeled Coverage Distance Limit for Outdoor Radios

The Modeled Coverage algorithm limits the radius of coverage for a given Radio to 1000 meters. This value results from evaluating a selection of "ideal case" Radios, which provided usable coverage to roughly 500 meters and doubled that value. A larger radius would also be too heavy for the computation and is a current trade-off.

Like Outdoor, Indoor Radios can collect MOBILE Rewards by providing coverage in multiple hexes.

The Obstruction Data Oracle cannot evaluate coverage by Indoor Radios as there are no good and reliable data sources about obstacles in indoor spaces. Instead, the Modeled Coverage Oracle uses an approximation based on the data gathered while testing certified Indoor Radios in various indoor settings.

From this testing, the hex in which an Indoor Radio is physically located receives maximum signal strength coverage, and all adjacent hexes receive lower signal strength. Therefore, the algorithm errs on generosity to ensure equitable potential MOBILE Rewards for Indoor Radio coverage.

Estimated per-hex coverage points for Indoor Radios are intentionally significantly higher than those awarded to Outdoor Radios to balance the importance of Indoor Radios in the MOBILE Network with their relatively smaller coverage footprints.

The reward tiers for Indoor Radios will be as follows:

Tier 1Tier 2
Potential Signal LevelHighLow
Estimated coverage points400100

These values were chosen by taking all the Outdoor Radios in an example area and analyzing the resulting distribution of estimated coverage points per Radio . Estimated coverage point values were chosen such that Indoor Radios receive roughly ¼th the estimated coverage points as the 95th percentile Outdoor Radios and about ½ the points of the average Outdoor Radio.

These results align with the current Radio Type Multiplieres approach 1:2.5:4 for Indoor Radios, Outdoor Radios, and High-Power Outdoor Radios. Figure 2 below is the cumulative distribution function plot of the sample market Outdoor Radio estimated coverage points.

Cumulative distribution function of Outdoor Radio estimated coverage points for 904 Radios in the L.A. market area.

### Modeled Coverage Explorer​

check coverage

Modeled Coverage Explorer is available here.

Modeled Coverage data will play a key role in providing information to visualize it, with more data added as additional external sources (e.g., Mobile Mappers) come into play.

HIP-74 proposed the creation of a new Mobile Explorer dedicated exclusively to the MOBILE Network as adding more features and data for MOBILE Rewards to the IOT Network Explorer becomes practically impossible as the MOBILE Network grows. The first iteration of the MOBILE Explorer proposes a basic map overlay of 5G data coverage with signal strength.

## Uptime Heartbeats​

A "heartbeat" is data sent by the 5G Hotspot indicating that a connected Radio is authorized to transmit 5G coverage.

Heartbeats occur every 60 seconds and transmit authorizations are valid for 240 seconds. This rolling overlap ensures that a Small Cell Radio can broadcast on an ongoing basis while allowing for brief interruptions.

To encourage reliable signal availability, 5G Hotspots and connected CBRS Small Cell Radios must generate at least one heartbeat per hour in 12 unique hours of the 24-hour Reward Period.

### Heartbeat Reward Tiers​

Each Radio is given a heartbeat multiplier of either 0 or 1.

Each Radio is awarded 1 point for a successful heartbeat in each hour, with a maximum of 24 points in the Reward Period. All Radios with at least 12 points in the 24-hour Reward Period are given a heartbeat multiplier of 1 and will be eligible to earn MOBILE Rewards.

### Heartbeat Examples​

Choose from the options below to see some heartbeat example scenarios and the impact on MOBILE rewards.

The Radio generated a heartbeat every hour of the day, earning 24 points.

This Radio will be eligible for rewards during the Reward Period.

## Backhaul Speed Tests​

A 5G Hotspot automatically performs Speed Tests, with the results averaged by the MOBILE PoC Oracle. The MOBILE PoC Oracle includes these Speed Test metrics in the Rewards calculations for each 5G Hotspot.

The 5G Hotspot will randomly measure download, upload, and latency to the MOBILE verifier twice in a given 24-hour period. If a test can not complete successfully, the 5G Hotspot automatically retries every 30 minutes until a Speed Test is successful. The first Speed Test for a newly installed 5G Hotspot is performed within the first 12 hours after powering it on.

A minimum of two and maximum of six Speed Tests are required in the previous 48 hours to calculate a Moving average results for each download, upload, and latency, after which a new series of Speed Test results must be collected before a Moving Average can be calculated.

### Speed Test Reward Tiers​

Speed test impact on Radio rewards

Each 5G Hotspot is given a speedtest multiplier of either 0.0, 0.25, 0.5 or 1.0.

This multiplier is applied to all connected Radios in rewards calculations.

Many locations where CBRS connectivity is being deployed, including some rural areas, do not always have the high-speed Internet connectivity needed to meet the acceptable Internet requirements for Genesis rewards consistently.

Often these areas do not have good cellular coverage either. That's why we believe it is essential to incentivize Helium deployments in less well-connected areas.

In response to community feedback and further exploration by Chris from DeWiPulse for his analysis of and commentary on public Internet data in the United States, Speed Test results are categorized into one of four Tiers - Acceptable, Degraded, Poor, and Fail.

Speed Test TierSpeedtest MultiplierRequirement (speeds in Mbps, latency in ms)
Acceptable1.00x100+ Download, AND 10+ Upload, AND <50 Latency
Degraded0.50x50+ Download, AND 5+ Upload, AND <75 Latency
Poor0.25x30+ Download, AND 2+ Upload, AND <100 Latency
Fail0.00x<30 Download, OR <2 Upload, OR >100 Latency

Tiered Speed Test values are used as a multiplier in Rewards calculations as follows:

• Speed Test Results are put into Tiers based on the minimum value of each Download, Upload, and Latency (logical AND).
• Speed Test results that do not meet the minimum requirements for any Download, Upload, or Latency are considered to have Failed and are not eligible for Rewards until the Speed Test Average is improved (logical OR).
Requirements Will Evolve

As the needs and realities of the Network change, backhaul requirements will evolve to better suit the Network and its users.

### Speedtest Examples​

Choose from the options below to see some speedtest example scenarios and the impact on MOBILE rewards.

Download    200 ->  AcceptableUpload       40 ->  AcceptableLatency      15 ->  Acceptable---------------------------------Speed Test Tier ->  Acceptable  -> 1.0x Multiplier

### Speed Test Example Calculations​

Here are a set of tables to help visualize the components that make up the Speed Test result.

info

It may take up to 12 hours for newly connected 5G Hotspots to perform a Speed Test, and a minimum of 2 Speed Tests are required for the MOBILE PoC Oracle to calculate a moving average.

This 5G Hotspot is passing all Speed Test metrics and is providing a high-quality connection.

Test 1

This 5G Hotspot will not be eligible for rewards during the Reward Periods for which the results of Test 1 are the most recent as there is not enough data to calculate a Moving Average.

Test 2 and Later

This 5G Hotspot will be eligible for full rewards during the Reward Periods for which the results of these are the most recent.

## Statistics on Helium Explorer​

Speed Test metrics are viewable on the 5G Hotspot's page on Explorer under the 5G Statistics tab. Here are examples of each status and a brief description of each metric and the resulting impact on Rewards calculations.

### Helium Explorer Examples​

Choose from the options below to see some example scenarios and the impact on MOBILE rewards.

Speed Test Passing - Acceptable

The Moving Average for all Speed Test metrics is in the Acceptable range.

A 1.0x multiplier is applied for the current Reward Period.

The Moving Average for Latency metrics is in the Acceptable range, however the 10 Mbps Download and 1 Mbps Upload metrics are below the Poor Tier.
A 0.0x multiplier is applied for the current Reward Period.