Topic: Broadcasting the Blockchain (Read 10469 times)

With the 'naked block' protocol being considered, you don't even need this much.  Currently, all full clients require all the data in order to completely check every block for validity, but a "light client" doesn't require this kind of certainty.  Since it's unlikely that clients receiving updates via this method would be mining, complete blocks are not necessary.  What is necessary is a complete block header chain, which only weighs in at 4 mb per year; and the merkle tree for any blocks that contain transactions that concern the client itself.  While it would be ideal to broadcast those merkle trees with the block header (i.e. the naked block, all except the actual transactions) it would be profoundly silly to broadcast every single transaction complete.

You can retransmit blocks with decreasing frequency as they get older. If you miss recent blocks, wait a little while and you get another copy. If you missed old blocks, you may have to wait a long time to get them, but you will eventually get them.

So, how do you know that you missed a needed block?

Double/tripple/etc broadcasting does not solve the problem. When is the block repeated? 8 hours later? What if you are off the grid for 24 hours, or just happen to be off when the rebroadcast occurs. The issue is not "unlikely" the issue is: the system is not 100% guaranteed.

Unfortunately, I can see some very real technical and legal issues with trying to do this as described.

First off, Wifi is possible in only two bands.  Since the higher N band is very new, and many smartphones still don't support it, I'm going to assume that the older B,G band is what they plan to use.  But there was a technical reason that this band was chosen at the time of development; namely that the B,G band was license free worldwide.  But why was that, since such license free technologies didn't really exist before Wifi itself?  Because the B,G band is the resonate frequency of hydrogen.  Thus, energy transmitted in this band is heavily attenuated by any water or hydrocarbons found in it's path, and was considered useless for distance communications.  This is still true, and has much to do with why Wifi is so poor at clear range.  It's also why this band is shared by every retail microwave that I know of, since food is pretty much all hydrocarbons and water.  While there wouldn't likely be much risk of hydrocarbons in the line of sight from low earth orbit, there would be much water.  On average, the Earth's atmosphere has enough water from space to sea level to equate to a 32 foot deep dive under the ocean's surface.  The amount of power that would be required to push through this and be receivable by common wifi hardware on the Earth's surface would be rediculous.

Second, there are also sound techincal reasons as to why wifi multicasting is not commonly used.  Mostly because wifi is a time-sharing technology that (generally) permits more than one unrelated connection to coexist on the same channel.  This is permitted because normal mode wifi requires that the hotspot 'listen' to it's own channel several times per second for other broadcasters trying to share the channel space.  This doesn't always work well, but it does work more often than most people realize.  However, a hotspot in space couldn't coordinate timesharing of all the hotspots in it's radio shadow even if it were possible for it to hear them.  In this case, the sat based signal would effectively 'jam' the chosen channel across the whole of it's radio shadow, and also be a violation of international communications treaties as a result.

Third, the licesne free broadcasting nature of the B,G band is limited to 'terrestrial' transmitters, and therefore doesn't apply to satillites at all.  A new treaty would be required to even permit such a license, since every country has max transmitter powers in the B,G band that would be WAY  what a sat would require.

While using the new N band would reduce the power requirements considerablely, the other two issues would still apply.  Perhaps a lower frequency license free band would work with modified FM band recievers, but I can't see a way around the international communications treaties regarding this.  Perhaps a broadcast stream that can switch around frequencies in the higher frequency shortwave bands would work, but the sat would have to be able to respond to the reflectivity of the ionosphere and changes in the critical frequency.  Most Shortwave broadcasters have to stay  the critical frequency so that their Earth bound transmitters can reflect their signal off of the F layer of the ionosphere, but what about a broadcaster in teh shortwave bands that deliberately stays above the critical frequency so that his signal is not reflected back into space?  Regardless, the data throughput woudl be low due to a narrow usable bandwidth and a particularly 'noisey' radio environment in those bands.

You don't always need a missed block, but if you do, there are alternative paths to aquire missed data.

Looks like someone is going to attempt this:

https://www.outernet.is/

You don't always need a missed block, but if you do, there are alternative paths to aquire missed data.

You don't always need a missed block, but if you do, there are alternative paths to aquire missed data.

The Bitcoin blockchain can be kept up-to-date with less than a 2400 baud connection.  ... Or is this concept simply wildly-unrealistic, pie-in-the-sky speculation?

Sadly thus far, there has been little 3rd party driver support to include this.  Note that all of the newer Atheros Chipsets starting with the 9XXX series (The stuff that now is pushing 802.11n) has dropped XR mode.