Re: cordless cell phone?

Jan 07, 2008 14 Replies


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


Hm. But when in DECT mode certainly the transmit power goes way down, no?

Follow the money, eh?

I don't know, my new Motorola KRZR has a menu that lets me put the phone in USB mass storage or modem mode. How much can that cost? Really? That's all I wanted from Canon who instead prefer some drivers to be required to access the camera at all.

Yes. I'm not suggesting that, when you already have a GSM 1.9GHz cell phone it's particularly *difficult* to add DECT functionality (I've seen presentations on how they manage to cram all of Bluetooth, WiFi, GPS and GSM into a phone which, at first, seems like it'd be horrifically expensive, but people have come up with very clever solutions to make it cheap), but even spending another dollar is enough that the manufacturer (or service provider) is probably going to do a marketing survey first to try to figure out whether or not it's really something people would pay an extra, e.g., $5 for.

It depends a lot on the company; I think it's impossible to really estimate. Depending on the talents and management of those involved and how much software they already have sitting around (e.g., does the company already have some mass storage device interface software they did for another product that can be re-used?), I can see anywhere from a few weeks to an entire year.

Buy a Mac? :-) (Macs come with Canon drivers built-in, last I heard...)

Yes, I saw that at work. Another thing that almost caused me to rupture an aneurysm is the fact that a camera that can drive a printer is acting as a host. You need a special cable to tell the camera it'll be acting as a peripheral... Thing is, they all look the same, and couldn't the devices just work it out in software?

ROFL! I almost spilled my water bottle.

Regards, Joerg http://www.analogconsultants.com/

Yeah, but you'd want to built it completely out of discretes! ;-)

Service to my country? Been there, Done that, and I\'ve got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida

Guilty. Not ADCs but I've reduced lots of circuits from the fancy digital domain to analog. Comment from an engineer after peeking at a new design last summer: "You mean, that's it?"

Regards, Joerg http://www.analogconsultants.com/

Do you ever worry that, on the off-chance you had to go out looking for a regular job again some day, you'd be hard-pressed to find one given that you just don't think widgets need to be as bloody complicated as the attending engineering manage has been led to believe... and they figure the problem is that you must be a little slow in comprehending the problem? :-)

[...]

I've seen DECT/GSM hybrids. There's just no market for them, especially since people now just set up their "home zone" and do away with the landline phone altogether.

The camera mfgr has nothing to do with it, it's just a software issue on the computer side which has been solved long ago. The name is gphotofs.

robert

On this very newsgroup we've had PICs suggested where a monoflop would have sufficed.

robert

Actually, no, I don't have such worries. For some reason I get swamped with work along the lines of "We have some really weird phenomena with this circuit and nobody out here has the foggiest ...". I can only guess but it might be because older guys are retiring. In at least one case that was definitely the reason.

Thing is, above a few hundred MHz stuff becomes analog again. But yeah, when I whip out a slide rule or a Smith chart I certainly get the looks. Anyone know where to buy pocket protectors these days ... ?

Regards, Joerg http://www.analogconsultants.com/

ROFL!

I've had one case where the delta between two events was calculated using an I/Q detector and a DSP. Then a larger DSP because it couldn't do it. Followed by the biggest honking DSP they could find because the larger one still wasn't powerful enough. Now it kind of worked but not very well. Replaced it with a bunch of fast comparators and adjustable delay lines. Out came a DC value and the rest of the math could have been done with a 4-bit uC on a watch crystal. Then came a question: "Why's that FET or whatever the heck it is over there have four connections coming out of it and what are those doughnut thingies for?"

Regards, Joerg http://www.analogconsultants.com/

1) I think gphotofs can reasonably be construed as "a lot of work." :-) It's great that some independent developers chose to do that work, but my point still stands that, had Canon done it, it still would have been "significantly more work." 2) gphotofs is Linux-only, so it leaves out the vast majority of digital camera users.

Thanks for the name, though -- I hadn't heard of gphotofs previously.

---Joel

If I had a knack for business I could probably make a living designing simple analog and digital electronics with no more background than Elektor-level hobby electronics of 20 years ago. My generation is probably the last one where hobby electronics "paid off" in the sense that for little money one could build stuff that was either too flashy and silly to be a marketable product (anything that beeps and blinks) or too expensive (stereo equipment). Now everything beeps and blinks and costs nothing.

But small-scale industry still has the need for simple custom solutions for simple problems such as motor control, interface adapters, power supplies and the like -- stuff that a 20-year-old EE fresh from college wouldn't know how to solve in software.

I wonder what will happen when all the ex-hobbyists die out.

robert

We'll probably have less reliable electronics. I have seen the front wave of that when taking apart appliances such as a pellet stove. Sat there in front of the controller and thought "What were they thinking?" I actually sent my findings to the stove manufacturer and upon some initial scoffing it resulted in an engineering change order ...

Regards, Joerg http://www.analogconsultants.com/

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required