I think it's funny that my cell phone with a software defined radio
> that works around 1.9GHz can't talk to my DECT 6.0 base which also
> works around 1.9GHz...
A couple reasons:
1) Cell phones are heavilg cost- and performance-optimized. The whole idea that, "oh, it's a software-defined radio, so it'll work on any band with any bandwidth!" is largely a myth propagated by people who either don't understand the relationships between noise, bandwidth and dynamic range... or those who are looking for funding to build 24-bit 1GHz ADCs. :-) DECT operates at
1920-1930MHz whereas GSM is 1850-1910MHz (uplink) and 1930-1990MHz (downlink). Notice where DECT is... inbetween the two, where a cell phone is often trying very hard to have significant attenuation so that the uplilnk and downlink don't interfere with each other! The point here is that there's a good chance it's not *just* software that would have to be changed in a cell phone to make it DECT compatible, but hardware as well -- and this could have a negative impact on component count (size) or cost. (I realize many DECT phones are the same at the *digital* level as GSM cell phones, I'm talking about the RF front end here.)
2) There's not a big enough monetary incentive to the guy making the cell phone to do it.
I'd like to have just one telephone handset. It's a cell phone when
> I'm away from home, and it connects to my DECT base set when I'm at
> home so I can use VOIP.
I'd suggest that a software-only approach to make this happen would be to link to a VOIP box via Bluetooth, although I realize that Bluetooth's range is only ~30 feet and hence probably not a good solution.
Why does my Canon camera not present
> myself as a USB mass storage device?
Because the typical user doesn't want to see "just a drive letter" when they plug in their camera, hence there's a separate device class for cameras. There's no reason a camera couldn't present itself as *both" a "camera" and a mass storage device, but again, this requires significantly more work on the manufacturer's part for what's probably felt to be little if any extra income.
---Joel