5 ms·

If you look at the image at the bottom of the "tech" page, there's a picture of a device + a tag that reads "802.15.4"

by nielsbot 12y ago

densone 12y ago
Helium Protocol is based on 802.15.4. You are correct.
- amscanne 12y ago
  How can one bridge handle tens and thousands of devices and cover 50 square miles per the tech page? That doesn't make sense.
  - pharkmillups 12y ago
    Hey amscanne - It's solely based on throughput. The helium bridge has very little state. Our true limitation will be how much we can put in the air to a single bridge. Our metro networks will have a lot of bridges.
  - jrockway 12y ago
    Well, they don't tell you the bitrate. WSPR is a protocol that can make worldwide contact on the HF bands (3-30MHz) with 0.01mW of power. The catch is that it takes 2 minutes to send a message like "KD2DTW/FN30". 900MHz signals don't propagate like HF (by refracting off the top of the ionosphere), but they do have interesting propagation characteristics like bouncing off of passing airplanes. If you have a protocol that can extract signals from below the noise floor, and enough erasure coding (reed-solomon, etc.) to handle bursts without connectivity, you can build an urban network fairly easily. The only problem is that it's not that useful. My guess is that they are like FitBit and just plan to blanket every home with one of these things, and allow devices to roam to whatever access point is closest (like when you walk past someone's house with a FitBit, and notice yours has synced).
    - amscanne 12y ago
      The site says specifically that one bridge can cover tens of thousands of devices and 50 square miles. It also seems to be based on ZigBee (that is, ZigBee devices can be retrofitted) so it's 2.4ghz, 915mhz or 868mhz. Like you said, there are plenty of ways to go one way (from a powerful transmitter). But those are noisy frequencies for a weak transmitter to make it several miles... Anyways, agreed that the plan is probably fitbit-style. But the crazy specs make it seem a bit like snake oil to me...
      - pharkmillups 12y ago
        Hey Amscanne - There are two things we're trying to convey here (but rest-assured we're not trying to be misleading): 1. We can support a lot of connections. I mean a lot. This is based on our design, but truly limited by the receiving radio. 2. 50 square miles is optimal conditions. It's hard to quantify how bridges and radio enabled devices will work in populated metropolitan areas. These numbers are solely based on field testing, not in metro areas.
        amscanne 12y ago
        I'm commenting because I'm genuinely curious about the technology, I'm not trying to tear anything down. That said, the technology page is not very clear. The wording doesn't currently indicate this is idealized or limit conditions. Because you say it covers tens of thousands of devices over such a large area, I assumed this would be expected (like a cell tower). Your description actually fits very closely with a cell network. Why would a device that covers only my home need to support connections with tens of thousands of devices? Would it cover me and all my co-workers at the office 1 mile away (well within it's 4 mile range)? Or would I be expected to have a bridge at home and in the office? Is it like a Femtocell in a mall or like the ZigBee bridge sitting in my living room? Given that picture, I'm genuinely curious about the capabilities. Immediately below that paragraph are bars that show a 700+ day battery life and a transmission power of 0.025mA. Are these for a totally different use case? If so, I'm confused. If not, it's amazing and I'm very exited. How is a transmission power of 0.025mA @ 915MHZ possible at a range of 4 miles? I would have assumed 1000x that (at least) would be necessary on unlicensed ZigBee spectrum. Similarly power would need to be amped up on the receive side,... meaning receive windows would be costly.

If you look at the image at the bottom of the "tech" page, there's a picture of a device + a tag that reads "802.15.4"

densone 12y ago

Helium Protocol is based on 802.15.4. You are correct.

amscanne 12y ago
How can one bridge handle tens and thousands of devices and cover 50 square miles per the tech page? That doesn't make sense.
- pharkmillups 12y ago
  Hey amscanne - It's solely based on throughput. The helium bridge has very little state. Our true limitation will be how much we can put in the air to a single bridge. Our metro networks will have a lot of bridges.
- jrockway 12y ago
  Well, they don't tell you the bitrate. WSPR is a protocol that can make worldwide contact on the HF bands (3-30MHz) with 0.01mW of power. The catch is that it takes 2 minutes to send a message like "KD2DTW/FN30". 900MHz signals don't propagate like HF (by refracting off the top of the ionosphere), but they do have interesting propagation characteristics like bouncing off of passing airplanes. If you have a protocol that can extract signals from below the noise floor, and enough erasure coding (reed-solomon, etc.) to handle bursts without connectivity, you can build an urban network fairly easily. The only problem is that it's not that useful. My guess is that they are like FitBit and just plan to blanket every home with one of these things, and allow devices to roam to whatever access point is closest (like when you walk past someone's house with a FitBit, and notice yours has synced).
  - amscanne 12y ago
    The site says specifically that one bridge can cover tens of thousands of devices and 50 square miles. It also seems to be based on ZigBee (that is, ZigBee devices can be retrofitted) so it's 2.4ghz, 915mhz or 868mhz. Like you said, there are plenty of ways to go one way (from a powerful transmitter). But those are noisy frequencies for a weak transmitter to make it several miles... Anyways, agreed that the plan is probably fitbit-style. But the crazy specs make it seem a bit like snake oil to me...
    - pharkmillups 12y ago
      Hey Amscanne - There are two things we're trying to convey here (but rest-assured we're not trying to be misleading): 1. We can support a lot of connections. I mean a lot. This is based on our design, but truly limited by the receiving radio. 2. 50 square miles is optimal conditions. It's hard to quantify how bridges and radio enabled devices will work in populated metropolitan areas. These numbers are solely based on field testing, not in metro areas.
      - amscanne 12y ago
        I'm commenting because I'm genuinely curious about the technology, I'm not trying to tear anything down. That said, the technology page is not very clear. The wording doesn't currently indicate this is idealized or limit conditions. Because you say it covers tens of thousands of devices over such a large area, I assumed this would be expected (like a cell tower). Your description actually fits very closely with a cell network. Why would a device that covers only my home need to support connections with tens of thousands of devices? Would it cover me and all my co-workers at the office 1 mile away (well within it's 4 mile range)? Or would I be expected to have a bridge at home and in the office? Is it like a Femtocell in a mall or like the ZigBee bridge sitting in my living room? Given that picture, I'm genuinely curious about the capabilities. Immediately below that paragraph are bars that show a 700+ day battery life and a transmission power of 0.025mA. Are these for a totally different use case? If so, I'm confused. If not, it's amazing and I'm very exited. How is a transmission power of 0.025mA @ 915MHZ possible at a range of 4 miles? I would have assumed 1000x that (at least) would be necessary on unlicensed ZigBee spectrum. Similarly power would need to be amped up on the receive side,... meaning receive windows would be costly.