Because he doesn’t have enough going on, Elon Musk—head of Tesla Motors, SpaceX, SolarCity, and the Hyperloop—is launching another project. Musk wants to build a second Internet in space and one day use it to connect people on Mars to the Web.
Link to BusinessWeek article
4000 geosynchronous LEO satellites !
4000 geosynchronous LEO satellites !
Not geosynchronous satellites, they are very low flying at 750 miles to keep latency down.
If he can do it so that the phone can be like a normal cellphone (in size and battery life) then he will do well because he will put all the terrestrial cellular companies out of business!
That will need a vastly better signal to noise ratio than the existing satphone networks have. Existing satphones have big antennae and resemble cellphones from the early 1990s. They are also crap functionally but that is just due to having been developed by incompetent people; there is no reason why a satphone could not be functionally identical to any modern smartphone.
It will also improve coverage in UK countryside, most of which is around one bar signal level and the data is the awesome GPRS at 20kbits/sec 
If he can do it so that the phone can be like a normal cellphone (in size and battery life) then he will do well because he will put all the terrestrial cellular companies out of business!
He won’t, because there is no way he can get the capacity of the terrestrial network. The number of terrestrial base stations worldwide must be in the millions.
He won’t, because there is no way he can get the capacity of the terrestrial network.
No way. The power requirements alone can not be met by the small satellites that he wants to install. Somewhere on the internet a former Iridium engineer explains that the network proposed by Musk can not even meet G3 standards.
As always, Shannon is the key.
You either wind up the transmit power until the signal pokes sufficiently above the noise floor (the traditional approach to communication) or you do some correlation and then you can work below the noise floor (as say GPS does) but then you need more bandwidth.
It’s obvious that at 750+ miles, this guy cannot hope to achieve it above the noise floor, using existing cellphone technology and using existing tower power output.
As always, Shannon is the key.
But that was long known before Iridium set up their network. GPS was up and working when Iridium (and Thuraya) set up their network. The technology is commonplace so to say. If they don’t achieve decent data bandwidths, why should Musk?
you do some correlation and then you can work below the noise floor (as say GPS does) but then you need more bandwidth.
Yes, but that decimates your datarate. And as you’re the first to complain about GPRS data rates…
Let’s wait and see. The last time someone tried (Iridium), it brought an industry giant (Motorola) down…
I still cannot understand why Iridium have such a rubbish data rate – 2400 bits/sec.
Because the satellites are too far away. You need a certain amount of power to overcome the path loss. On the user terminal you’re limited to ~5W output power (both due to battery and nonionizing radiation safety limits), and roughly non-directional antennae. Now Shannon tells you what Eb/N0 you need. N0 is given, the power is given, now the only variable you have to come up with the required Eb (energy per bit) is to make the bits longer.
