Reception quality across technology platforms

Perhaps someone on here has some insight into this question:

It seems like the cleanest wireless call with optimum compression and
decompression would go from the phone of one company to another phone
on the same company's network (CDMA to CDMA, GSM to GSM, IDEN to IDEN,
etc.)

A close second would probably be the quality of any vendor's products
in reaching any landline telephone.

My question is: what is lost when technological standards need to be
jumped in order to complete a wireless call in the US? Should we
expect better connections between a CDMA-standard phone and a GSM phone
in the same general market area, or is there something inherently
faulty in the compression algorithms that will deliver a
less-than-top-quality phone call for both parties? In other words,
will a call from Sprint to Cingular (GSM) sound worse than one from
Sprint to Verizon (CDMA) simply because of differences in compression
technology?

At my job we have the vast majority of people on VZW, city employees on
Nextel-IDEN, a few Blackberry users on Cingular or T-Mobile, and the
rest of us on Sprint or something similar. I'm very happy with Sprint
quality AND 7pm nights. However, my question (above) remains - does
crossing a compression hurdle place any constraints on the best
possible call?

TIA.

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Der Tschonnie wrote:
> Perhaps someone on here has some insight into this question:
>
> It seems like the cleanest wireless call with optimum compression and
> decompression would go from the phone of one company to another phone
> on the same company's network (CDMA to CDMA, GSM to GSM, IDEN to IDEN,
> etc.)

In theory, yes, as long as signal quality on both ends were optimal.

> A close second would probably be the quality of any vendor's products
> in reaching any landline telephone.

Probably also true.

> My question is: what is lost when technological standards need to be
> jumped in order to complete a wireless call in the US? Should we
> expect better connections between a CDMA-standard phone and a GSM phone
> in the same general market area, or is there something inherently
> faulty in the compression algorithms that will deliver a
> less-than-top-quality phone call for both parties?

First off, by definition, all digital cell phone calls are "less than
optimal" from a purist standpoint. This is because a very lossy
compression method is applied in each case. The cell companies are
taking what used to occupy a 48-64kbps TDM voice channel, and is
compressing it down to between 8-13kbps. In doing this, the codecs
involved in compressing and decompressing the voice channel at each end
are removing aspects of the audio that sound engineers believe the human
brain will be able to compensate for when it hears what's left. The end
result is that what comes out at one end *somewhat resembles* what came
in at the other end, but isn't close to be an exact duplicate.

Now, the current codecs are a bit better than what they used to be at
compressing more data while losing less of it, but they still aren't
perfect. What's more, the codecs in use for GSM will exclude different
aspects of the voice pattern than will a CDMA codec, and so the end
result will be that you WILL lose more and more of the speech pattern
with each successive change in medium.

Having said all of this, most lay people really don't notice a
difference; they expect their phone to be a phone like any other phone,
and so they are not looking for artifacts or discrepancies in audio.
And in most cases, our ears and brains do just fine re-creating the
missing aspects of the speech patterns so that we don't notice what's
going on. COnsequently, most people don't notice too much of a
degradation when a CDMA user calls a GSM user or vice versa.


> In other words,
> will a call from Sprint to Cingular (GSM) sound worse than one from
> Sprint to Verizon (CDMA) simply because of differences in compression
> technology?

In theory, both won't sound the greatest. However, it's likely that a
cross-platform call will sound *slightly* worse.


> At my job we have the vast majority of people on VZW, city employees on
> Nextel-IDEN,

*shudder* iDEN. That's probably the worst example of a lossy codec
there is. iDEN by nature is an overstressed technology, and Motorola's
answer has been to cram as many people as possible into a channel by
compressing the hell out of the audio, and doing it more and more with
each successive "improvement" to the standard. Hands down, that's the
bottom of the barrel right there.

> a few Blackberry users on Cingular or T-Mobile, and the
> rest of us on Sprint or something similar. I'm very happy with Sprint
> quality AND 7pm nights. However, my question (above) remains - does
> crossing a compression hurdle place any constraints on the best
> possible call?

Yes it can, but usually not enough for it to be a problem.

>
> TIA.
>


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

Isaiah -

Exactly the information I was looking for, including specs. Thank you!


John

Der Tschonnie wrote:
> It seems like the cleanest wireless call with optimum compression and
> decompression would go from the phone of one company to another phone
> on the same company's network (CDMA to CDMA, GSM to GSM, IDEN to IDEN,
> etc.)
>
> A close second would probably be the quality of any vendor's products
> in reaching any landline telephone.

I noticed this a few years ago that when a caller from a cellular phone
(please, no flames that PCS is not cellular) leaves a message on some
digital answering machines, the answering machine's codec has a problem
with the phones's "codec'ed audio".