Minimum RF Performance?

Bubba DeBub wrote:
> Why does the customer have to be concerned with which cell phone
> provides the best reception if he lives in a low signal area? I have
> seen many folks try to purchase the phone that has the best
> reception. Note that the phone with the best reception is not always
> the most expensive phone.
>
> Why can't the cell phone manufacturers establish standards for RF
> performance so that all cell phones sold by a cellular carrier will
> provide adequate reception in the most minimal signal conditions?
>
> It seems that the cell phone carriers could solve this problem by
> establishing better RF performance standards for all cell phone
> suppliers. Therefore the reception of all makes and models of phones
> would be identical.

This reminds me of the baseball player who suggested that first base be
moved out an extra six inches. The idea was to eliminate all the close
calls.

Same thing with phone coverage. If all the phones suddenly became twice as
sensitive, it would be silly for the providers to build so many cells.
Economics would dictate that the number of cells be decreased by - oh about
1.0/1.414.

Then, in this imaginary world of incredible receivers, like the baseball
players who have to go an extra six inches to get to first base, some phones
will make it, and others will not. We'll be back where we are today, only
with more of our nickles and dimes tied up in great receiver technology, and
less money invested in cell towers.
--

Mike Russell
www.geigy.2y.net

---

› See More: Minimum RF Performance?

"Manufacturers consider it to be sensitive proprietary information."

Not so.... They can consider all they want but in the US all RF issues
are regulated by the FCC. Every cell phone in the US has an FCC ID
number. To get approved for use in the US all cell phone manufacturers
have to submit all pertinent information for every model to the FCC
which makes it public information.

"Chas." <[email protected]> wrote in message news:[email protected]...
> "Manufacturers consider it to be sensitive proprietary information."
>
> Not so.... They can consider all they want but in the US all RF issues
> are regulated by the FCC. Every cell phone in the US has an FCC ID
> number. To get approved for use in the US all cell phone manufacturers
> have to submit all pertinent information for every model to the FCC
> which makes it public information.

OK, I'll bite. If RF sensitivity data is public information, where can I access it?
Fact is, the FCC's mandate deals with issues that will affect interference
to other services, parameters like radiated power, frequency stability,
spurious harmonics, etc., but they couldn't care less about receiver
RF sensitivity.

--
John Richards

John Richards wrote:
> "Joel Kolstad" <[email protected]> wrote in message
> news:[email protected]...

>> It just can't be done. As I mentioned, try something simpler first
>> -- computers. How do you go about boiling their performance down to
>> just one number that lets you choose the better one?
>
>
> I don't think the OP is asking for an overall performance measurement,
> just the RF sensitivity, which is only one parameter, and is indeed
> measurable.

And we're saying that that's all fine and good, but just knowing RF
sensitivity isn't going to be an accurate indicator. In fact given the
nature of CDMA, a phone that is TOO sensitive can actually be a
detriment in a heavily-loaded network, because the phone will see too
much of a noise floor, and the EC/Io seen by the handset will such that
the phone actually won't be useable.

I think the problem here is that most people THINK they understand the
electronics in their phones, but in reality they don't know the half of
it. This isn't analog radio, where greater sensitivity is all you need
to pull in a weak signal. It USED to be that simple, but the public
demanded that cell phones be more common, work in more places, overcome
all kinds of interference that wasn't so much of a concern before, and
still be relatively cheap. And in order to meet all that,network
designers were forced to use signalling schemes and formats that aren't
exactly conventional in how they operate, and so things get pretty dicey
when you try to equate a single value with a phone being the "best."


> I've seen RF sensitivity spec'd for high performance receivers
> such as military and ham shortwave radios,

Military grade equipment tends to be either in-the-clear analog
communications for for more basic functions, and encrypted signalling
sent over analog for more sensitive communications (even the president's
wireless communications use encryption-over-AMPS... they still haven't
gone fully digital). Shortware radio has ALWAYS been analog and
in-the-clear. Even the military's implementation of CDMA is very
different from the Qualcomm standard we use today (and GSM will be using
tomorrow). So for that type of equipment, yes RF sensitivity has
relevance. For your phone, however, a high sensitivity can be misleading.


--
E-mail fudged to thwart spammers.
Transpose the c's and a's in my e-mail address to reply.

"John Richards" <[email protected]> wrote in message
news:[email protected]...
> "Chas." <[email protected]> wrote in message
news:[email protected]...
> > "Manufacturers consider it to be sensitive proprietary
information."
> >
> > Not so.... They can consider all they want but in the US all RF
issues
> > are regulated by the FCC. Every cell phone in the US has an FCC ID
> > number. To get approved for use in the US all cell phone
manufacturers
> > have to submit all pertinent information for every model to the
FCC
> > which makes it public information.
>
> OK, I'll bite. If RF sensitivity data is public information, where
can I access it?
> Fact is, the FCC's mandate deals with issues that will affect
interference
> to other services, parameters like radiated power, frequency
stability,
> spurious harmonics, etc., but they couldn't care less about receiver
> RF sensitivity.

True, all I'm saying is that it is not proprietary information.

There may be some place in FCC records where this info can be
obtained. A friend worked as an engineer for HP for years doing RF
interference testing on almost all of their products. Much of the
information in her test results were filed with the FCC.
--
Chas. [email protected] (Drop spamski to E-mail me)

"speedy" <[email protected]> wrote in message
news:[email protected]...
>
>
> CellGuy wrote:
>
> > It's interesting to note that one of the best RF performers was
the simple
> > Moto StarTac series. No frills - just great performance.
>
> Ditto!
>
> I dont want the extra crap, just a phone that is readable,
comfortable,
> and doesnt drop calls all the time.
>
> I still like the startac better than my VX4400
>
I haven't used any Moto phones in years but my experience was that
they had the poorest ergonomically designs and every model had a
different UI and key pattern.
--
Chas. [email protected] (Drop spamski to E-mail me)

"John Richards" <[email protected]> wrote in message
news:[email protected]...
> I don't think the OP is asking for an overall performance measurement,
> just the RF sensitivity, which is only one parameter, and is indeed
> measurable. I've seen RF sensitivity spec'd for high performance receivers
> such as military and ham shortwave radios, but never for consumer
> devices.

I believe that's because -- with the military and ham radios -- there's a
well-known, agreed-upon modulation method taking place. E.g., "-100dBm RF
input power required for demodulated audio to have 10dB SNR." And notice
that even this specification ignores the antenna, which is a very
significant factor for a cell phone since it can not or typically is not
changed.

For the cell phone, then, you could get as far as "-100dBm RF input power
required for raw bit error rate of 10^-2," but where do you go from there?
Different CoDecs and FEC schemes handle bit error rates very differently in
terms of their resulting performance; it is entirely conceivable that the
audio on one cell system (e.g., GSM or CDMA) sounds better with a 10^-4 BER
than a phone on another system with 10^-6 BER!

> Manufacturers consider it to be sensitive proprietary information.

Sure, but (going back to the camera lens review magazines analogy) if there
were a large demand for such data, there's no reason independent test labs
couldn't provide it.

---Joel

That's a BIG TEN-FOUR GOOD BUDDY!

Bubba
(Keep the rubber side down and keep on truckin)

"Joel Kolstad" <[email protected]> wrote in message
news:[email protected]...
> "John Richards" <[email protected]> wrote in message
> news:[email protected]...
>> I don't think the OP is asking for an overall performance measurement,
>> just the RF sensitivity, which is only one parameter, and is indeed
>> measurable. I've seen RF sensitivity spec'd for high performance
>> receivers
>> such as military and ham shortwave radios, but never for consumer
>> devices.
>
> I believe that's because -- with the military and ham radios -- there's a
> well-known, agreed-upon modulation method taking place. E.g., "-100dBm RF
> input power required for demodulated audio to have 10dB SNR." And notice
> that even this specification ignores the antenna, which is a very
> significant factor for a cell phone since it can not or typically is not
> changed.
>
> For the cell phone, then, you could get as far as "-100dBm RF input power
> required for raw bit error rate of 10^-2," but where do you go from there?
> Different CoDecs and FEC schemes handle bit error rates very differently
> in terms of their resulting performance; it is entirely conceivable that
> the audio on one cell system (e.g., GSM or CDMA) sounds better with a
> 10^-4 BER than a phone on another system with 10^-6 BER!
>
>> Manufacturers consider it to be sensitive proprietary information.
>
> Sure, but (going back to the camera lens review magazines analogy) if
> there were a large demand for such data, there's no reason independent
> test labs couldn't provide it.
>
> ---Joel
>
>