5 ms·

I'm way out of my area of expertise, but I'd really like to know more about the underlying technology. I searched around a little, but I'm not sure about: 1. T

by ggreer 12y ago

I'm way out of my area of expertise, but I'd really like to know more about the underlying technology. I searched around a little, but I'm not sure about: 1. The frequency band(s) it operates on. 2. Average/best-case data transfer rates. 3. Energy usage. Sending 10 bytes uses 0.026mA? Ok... that's current, not energy. To get power usage (watts), you need voltage and current. To get energy usage (joules, watt-hours), you need voltage, current, and time. I assume the voltage is the same in the Bluetooth comparison, but it's unclear if both radios are on for the same amount of time. 4. The bridges. Claimed coverage is up to 50 square miles, so sqrt(50/pi) == 4 mile range. Are directional antennas required for that? Is this a limitation of the protocol or the radio? Based on the information available, I'm guessing this is an IEEE 802.15.4[1] device running on the 900Mhz ISM band. Transfer rates probably peak at 250Kbit/sec. I think the energy comparison to Bluetooth is disingenuous. Bluetooth probably has more expensive startup costs. Sending 10 bytes may take much less energy, but Bluetooth's faster data rates may allow it to win on a 10 megabyte transfer. It's interesting, but I really want to know more before considering the product. 1. http://en.wikipedia.org/wiki/IEEE_802.15.4 http://en.wikipedia.org/wiki/IEEE_802.15.4

notthetup 12y ago
I think the website compares it to BluetoothLE which is a really low energy. But typical BluetoothLE data rates are much much lower than 250Kbits/s. I'm still surprised that they can bring it down to lesser active current draw than BluetoothLE which was designed for low-data rate, low current draw, short distance comms. Edit : Here's a app note on real life current draw of TI's BluetoothLE solution. http://www.ti.com/lit/an/swra347a/swra347a.pdf http://www.ti.com/lit/an/swra347a/swra347a.pdf Edit 2: Here's another research paper comparing ZigBee and BLE solution's current draws. ZigBee is almost an order magnitude larger in current draw. http://research.microsoft.com/pubs/192688/IWS%202013%20wireless%20power%20consumption.pdf http://research.microsoft.com/pubs/192688/IWS%202013%20wirel... Edit 3: Old but good presentation on power usage in 802.15.4. http://www.cens.ucla.edu/sensys03/sensys03-callaway.pdf http://www.cens.ucla.edu/sensys03/sensys03-callaway.pdf
nielsbot 12y ago
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

by ggreer 12y ago

notthetup 12y ago

I think the website compares it to BluetoothLE which is a really low energy. But typical BluetoothLE data rates are much much lower than 250Kbits/s. I'm still surprised that they can bring it down to lesser active current draw than BluetoothLE which was designed for low-data rate, low current draw, short distance comms. Edit : Here's a app note on real life current draw of TI's BluetoothLE solution. http://www.ti.com/lit/an/swra347a/swra347a.pdf http://www.ti.com/lit/an/swra347a/swra347a.pdf Edit 2: Here's another research paper comparing ZigBee and BLE solution's current draws. ZigBee is almost an order magnitude larger in current draw. http://research.microsoft.com/pubs/192688/IWS%202013%20wireless%20power%20consumption.pdf http://research.microsoft.com/pubs/192688/IWS%202013%20wirel... Edit 3: Old but good presentation on power usage in 802.15.4. http://www.cens.ucla.edu/sensys03/sensys03-callaway.pdf http://www.cens.ucla.edu/sensys03/sensys03-callaway.pdf

nielsbot 12y ago

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