why is mobile call quality so terrible?
May 3, 2015 10:00 AM   Subscribe

When calling landline to landline, I have no trouble hearing every word that's said. Meanwhile, my friend just called someone to give an ETA and ended up shouting NATO phonetic alphabet into a smart phone that can stream 1080p video. After he hung up, he admitted that he hated talking on telephones because one party or the other always needed something repeated. Why is mobile call quality so terrible? Why do people not demand this (in the economic sense)?

I realize on my eight year old flip phone with some $10 a month plan, this will be some sordid story of poor-quality microphones feeding noisy signal onto under-provisioned networks via an excessively lossy encoder running on wimpy hardware. But my friend tells me that even if I were willing to shell out for a latest-generation handset and high-end service plan, I just cannot buy anything like the call quality I get on my 1960s model 500 rotary-dial.
posted by d. z. wang to Technology (18 answers total) 13 users marked this as a favorite
 
Cell phones use a stupidly low audio stream rate. See a list here for comparisons.

Why this is still the technology used on phones more powerful than the computers used to run the Apollo missions, I have no idea.
posted by phunniemee at 10:08 AM on May 3, 2015 [1 favorite]


One specific problem is a lot of calls are half duplex; when one party is talking the other end of the line goes silent. It doesn't have to be this way, and not all calls are like that, but it happens often enough to me (iPhone, Verizon, San Francisco) I do my best to never use the cell phone as, you know, a phone.
posted by Nelson at 10:10 AM on May 3, 2015 [2 favorites]


Phones, and cell phones in particular have a very low sample rate. Voice over LTE will eventuall improve that some. In the mean time smart phone users can use Skype, Google hangouts, etc... which all have the potential for higher quality.
posted by token-ring at 10:16 AM on May 3, 2015 [1 favorite]


There's been a mismatch of technology and expectations since the very beginning of mobile service. We compare them to landlines, but a mobile phone is really a tiny FM radio with an equally tiny antenna. It's not a phone, per se. It's a walkie-talkie.

The marketing makes it worse. Notice that companies talk about coverage, not quality, and even then, coverage is a meaningless distinction for 99.9999 percent of Americans.

There used to be "bag phones" that were larger phones built into purpose-built handbags. About the size of a day planner book. They were much more powerful, had bigger batteries and offered better call quality. But they didn't fit into a pocket, ya' know.
posted by Cool Papa Bell at 10:23 AM on May 3, 2015 [1 favorite]


Why do people not demand this (in the economic sense)?

One reason is that talking on the phone is becoming less and less necessary as people transition to more text-based communication. Although I think one of the reasons I loathe talking to people on the phone so much is just how difficult it is on a mobile. This may be a feed-forward cycle.
posted by grouse at 10:42 AM on May 3, 2015 [4 favorites]


Virtually everyone involved with cell phones made the decision in the 90s to focus on capacity - systems to support the most simultaneous calls - rather than quality.

Cell phones that used the now-deprecated analog AMPS networks in the US actually used to sound pretty good. The AMPS networks used 30Mhz of bandwidth per call, resulting in quality that sounded roughly like a wired voice call over a slightly crackly radio. It was OK.

However, as digital standards - GSM, CDMA and D-AMPS - came into vogue in the 90s as additional bandwidth opened up for digital communications. These standards also provided desirable additional services like packet data and SMS on top of voice services. In order to assure maximum capacity as the cell phone networks started to fill with new subscribers, digital voice calls were compressed to what is essentially a minimal acceptable level of service. D-AMPS, for example, took the bandwidth that could be used for one analog phone call and turned it into enough bandwidth for three digital phone calls. More available capacity for calls in the same bandwidth meant more subscribers could be added and generate more revenue with the same bandwidth costs, saving a little room for data and text messages. You can see how this would have made sense at the time.

You can see the same thing happening with satellite television services. Satellite HDTV could potentially look wonderful, but as the satellite providers added more channels to the limited bandwidth of their available transponders, they turned up the digital compression to cram more in, resulting in lower-quality, blocky video. Available channels were (and still are) considered more important than video quality.

As more bandwidth becomes available through the LTE bands, providers are starting to change their stance on this by making "HD" calls available via LTE, but this change is in its infancy. Most phones are not HD voice compatible with the exception of the most recent high-end phones, areas that don't have LTE coverage can't use HD voice, and many lower-cost providers simply do not offer the service.

So, if you happen to have an iPhone 6 or Nexus 6, are on a post-paid contract with one of the big four, and are in an area with decent LTE coverage talking to someone else who fulfills all of those requirements, voice calls can actually sound pretty good. However, since there are so many older phones, non-HD providers and areas without good LTE coverage out there that do not fulfill all the requirements, it's pretty unlikely you'll be able to reap the benefit of HD voice on a day to day phone call.

It does seem like now that additional capacity has been built into the networks and the number of subscribers is stabilizing, manufacturers and providers have seen the demand for clear calls and are starting to change. It can't come soon enough. Most cell phone calls do indeed sound awful, and it has always been surprising to me that more people didn't complain.
posted by eschatfische at 10:43 AM on May 3, 2015 [14 favorites]


In my mother's case, and I suspect many, she doesn't hold the phone up to her mouth. It's like ... Charlie Brown's teacher. Then when I ask her to put the phone closer to her mouth, magic! Modern phones don't have the physical cue for 'put this next to your mouth and talk into it'.

Also, I wonder whether smartphone microphone designers account for the about of silicone or plastic that anyone sane immediately puts on a new phone.
posted by Dashy at 10:50 AM on May 3, 2015 [3 favorites]


I think this might be a country-specific thing; I live in the UK and I don't think I've ever experienced poor mobile call quality since I first got a mobile in about 1998. If I have a bad signal the call might cut out, very occasionally I get problems with one end or the other being completely silent, but never poor audio quality.

Maybe this is something to do with relative population density and its impacts on the economics of the thing?
posted by emilyw at 10:51 AM on May 3, 2015 [1 favorite]


When I got an iPhone 5 with LTE on t-mobile a few years back, it was enabled for "HD voice," or some such. As long as I am talking to someone else on an iPhone or other high end smartphone who is also on T-Mo, the voice quality is a fucking revelation. Better than any landline I still use. And I hear that from others who have this as well. Not sure what the difference is or whether other operators offer this, but for the past couple of years I have been deliriously happy with the voice call quality on my cell after years of saying "can you repeat that?"

I also find that using a good quality wired earbud and mic or my car's excellent Bluetooth hookup helps a lot compared to using the phone' built in speaker and mic.

Here is T-Mo's info page about it. I love it.
posted by spitbull at 10:51 AM on May 3, 2015 [2 favorites]


Same as emilyw I'm in the UK and call quality isn't an issue for me, to be fair I am in decent-sized (500k population) city. Lots of people here justify spending on their Iphones by economising and doing without their landlines, although some broadband packages force you to have a landline too. Our landline is more a nuisance than anything else with call centres phoning those numbers while actual friends will text rather than phone 9 times out of 10.
posted by AuroraSky at 10:55 AM on May 3, 2015 [1 favorite]


Most manufacturers don't seem to care. I thought all smartphones were the same until my husband got a Google Nexus 5. It must have a great directional mic as in can hear everything he says very clearly even if he's next to a commuter train whizzing by or talking outside in wind. I've never heard anyone else's phone provide such good audio.
posted by quince at 10:57 AM on May 3, 2015 [1 favorite]


One specific problem is a lot of calls are half duplex...

This one point has been my biggest hate-point about cellular in the US. You can't have a natural conversation over the damned things. It's crazy that my more-or-less 100+ year-old landline technology still delivers clearer and higher quality voice quality than does my cellular. Ditto with landline vs. VOIP (at least any VOIP I've tried)
posted by Thorzdad at 11:06 AM on May 3, 2015 [1 favorite]


8 years old? Yeah, you're probably not even on 3g, let alone 4g/lte...that's probably 2g/edge that you're using. As the providers continue fleshing out their lte networks, they're putting like zero effort into maintaining their 2g networks, which may even go away altogether in the not-too-distant future. Borrow a friend's newer phone and call someone with it. You will definitely hear a big difference. I would look into upgrading (jeez...8 years? You might as well be banging rocks together). Check out swappa.com for bargains.
posted by sexyrobot at 4:13 PM on May 3, 2015 [1 favorite]


(To clarify...2g/3g/4g/lte are different networks altogether...different areas of the electromagnetic spectrum...with 4g/lte having the greatest amount of bandwith capability. You can't access the 4g speeds/voice quality on your phone in the same way you can't watch tv on a radio. However, current 4g phones also have 3g and 2g radios in them, so if you go out of 4g coverage you aren't completely cut off. It's like being able to listen to radio on the tv.)
posted by sexyrobot at 4:21 PM on May 3, 2015


Why do people not demand this (in the economic sense)?

In the glorious free market, consumers' demands of monopolies are often ignored.
posted by Noisy Pink Bubbles at 6:57 PM on May 3, 2015 [2 favorites]


The main problem is one of low bitrate. Some phones do have poor quality microphones or what have you, but in the end, it's mainly that the carriers have continually attempted to cram more calls into the same space. A secondary issue is that different wireless technologies use different codecs, which really screws things up at the low bitrates in use these days.

GSM carriers (at&t and T-Mobile) used to use a codec called EFR at about 13Kbps on their 2G networks. This allowed them to fit 8 calls in one 200Khz carrier, or one per time slot. This actually sounded really good, especially compared to D-AMPS. To increase capacity when additional spectrum was unavailable and they didn't want to expend the money and effort to split cells into smaller units, they switched to a half-rate codec, which is exactly what it sounds like. Rather than allowing 8 simultaneous calls, it allowed 16 per carrier (two per timeslot), at the expense of severely reduced quality. Despite having the capability of only using half rate when congestion was actually an issue, at&t in particular chose to use it full time. Eventually, they switched to a newer codec called AMR which sounds somewhat better, but it's still not very good in the half rate version. 6Kbps just isn't enough.

Ironically, if you can find an old phone that doesn't support half rate or will allow you to disable half rate in an engineering menu,, the network will use the old full rate codecs and you'll get good call quality, assuming both ends are using it (or one end is a landline).

Annoyingly, everyone has decided to continue using the lower bitrate codecs even with 3G and 4G. HD Voice is slowly changing that, but it somewhat unfortunately also increases the passband from around 4Khz to 12Khz or thereabouts, which is great in theory, but in practice means that when they inevitably reduce the bitrates in the future it will sound even worse than the current codecs do.

Another issue is that when you call someone on a different network, the audio is compressed with your network's choice of codec, decompressed to raw PCM, then recompressed at the other end with that network's codec. This isn't much of an issue if you are calling from at&t to T-Mobile or Verizon to Sprint as the GSM carriers all use AMR and the CDMA carriers all use EVRC, so there is no extra loss. If you call between technologies, however, you are guaranteed to have more loss since the different codecs make different choices about what to throw out.

If you want good call quality, use a VoIP provider that allows you to use a 64Kbps uncompressed PCM stream. It will be exactly the same as a landline, assuming both ends are using it and there is no transcoding along the way, which there usually isn't with VoIP providers that support standard SIP. You may have to disable compression in your VoIP software, though, as they often come configured to use compression by default. You can also find some that use G.722 or AMR-wideband and thus allow for a higher quality call despite having compression applied, but you have to have a phone (soft or otherwise) that supports it, whereas basically anything supports G.711 uncompressed PCM.

The long and short of it is that HD Voice isn't really necessary to get good quality out of cell phones, the carriers just need to tell the phones to use a higher bitrate (they all support it), but they won't because they can't market it as HD and it reduces both voice and data capacity. They'd rather say you can download 10Mbps or whatever than give you better sound.
posted by wierdo at 7:16 PM on May 3, 2015 [3 favorites]


When I got an iPhone 5 with LTE on t-mobile a few years back, it was enabled for "HD voice," or some such. As long as I am talking to someone else on an iPhone or other high end smartphone who is also on T-Mo, the voice quality is a fucking revelation.

This happens with T-Mobile over Wifi Calling, too. After I got an iPhone 6 I've had people (who weren't on T-Mobile!) remark about the improvement in voice quality.
posted by neckro23 at 8:29 AM on May 4, 2015


Yeah I think this is country-specific too. I have no idea what you're talking about - only one person can talk at at a time on American mobiles? What madness is that?

Obviously if somebody is outside on a mobile there is more background noise than there is on an office landline, but a mobile in my house sounds the same as a landline in my house. Skype is definitely crappier though. Lots of digital artefact and dropped calls.
posted by tinkletown at 2:16 PM on May 4, 2015


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