For what it's worth, it didn't used to be this way. Back when CDMA was just getting started in the US, Qualcomm had these QCP-2700 digital cell phones that really did sound a LOT better than even a landline phone. of course, that was back when vocoders were set that 13kbps, which with compression, was ample bandwidth for human speech.
The problem here is that when digital started penetrating the market, cellular rates started coming down and demand for cellular phones increased. This taxed even the most well-off digital networks, and so to accomodate everyone, cell carriers began demanding vocoders that used less bandwidth. 13kbps vocoders gave way to 8kbps, and then even further to the variable rate vocoders that are in use today (which can step down as far as 4kbps depending on what sounds are being transmitted).
Probably not. In fact, the trend is for MORE compression, using less bandwidth. Granted the new vocoders being developed are using more ingenious methods to make this happen, and they promise to improve sound quality while still reducing their network overhead. We'll see if that promise is fulfilled.
Compression IS happening right now. The problem is that there is a huge difference between lossy compression (the type which is in use now, which discards certain elements of the audio that the codec thinks the human ear won't notice is missing much) and type of compression that you're probably expecting, lossless compression (the type which does not discard any audio information during compression).
Your modern cell phone has to be able to compress audio instantaneously. It wouldn't do anyone much good if the phone captured several seconds of audio, spent a few more seconds compression that audio using a lossless algorithm, and then sending it down the line where a further delay is added while the receiving end decompresses and replays the signal. At present, cell phones just don't have powerful enough processors to do lossless compression in real time.
The compromise then is to use a very lossy codec, one that discards portions of the sound that is presented to it, in the hopes that the human ear ont he receiving end will not notice that those components are missing. Although the quality suffers, it does allow a modern cell phone to quickly compress the audip it needs to transmit in almost-real time. You'll note, there is still a delay of about a quarter to a half a second between the time the person actually says something into a digital cell phone, and the time in which the sound arrives at the other end, and you'll also note that this delay just isnt't present when one uses an analog cellular or wireline phone.
No. Different digital cell phones use different codecs. ALL of them use compression, and NONE of them truly give toll quality speech, but the differing codecs DO sound different, and it tends to be a matter of personal preference as to which sounds better. I know some people who prefer GSM phones, as they feel the sound coming from GSM is more natural to them. I, on the other hand, find GSM to be very harsh sounding to my ears ... very raspy, very shrill, and actually rather painful to listen to after an extended period. I prefer my CDMA phone, as the sound from CDMA (in my opinion, yours may differ) is much easier on my ears.
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