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Tuesday, August 19, 2008

So what's up with the 3G performance in the iPhone?

Having been buried in work & on holiday for much of the past month, I hadn't really caught up with some of the news about the 3G iPhone. There seems to be widespread consternation about the performance of the device when connected via 3G, both in terms of connect speed and download performance.

About 200-300kbit/s seems to be a typical connection speed in the US, with some people reporting much worse performance (on the fringes of coverage). However, according to Wired's 3G iPhone performance map, many users in Europe are getting 1-2Mbit/s quite easily.

Various fingers of blame are being pointed - is it the AT&T network in the US? Is it the Infineon chipset?

Or is this just another manifestation of my favourite bugbear - the disconnect between mobile network designers and device developers (and thus by extension the 'real' user experience). It is simply the case that the original usage cases envisaged for HSDPA didn't include the type of rich, demanding applications (and implied traffic patterns) that iPhones generate?

Some thoughts:

- firstly, this could well be a manifestation of the HSDPA "idle mode" latency I discussed a few weeks ago. For iPhone users used to always-on, instant-connect WiFi, or even a nailed-up EDGE connection on a matured & optimised network - the initial "time to connect" could well be notably worse.
- secondly, in many countries, 3G is deployed in a higher frequency band than 2G (1900MHz vs 850MHz for AT&T, or 2100MHz vs 900/1800MHz in Europe). This means it will have shorter range, lesser coverage, and crucially worse indoor penetration.
- the audience of 3G iPhone users is fairly self-selecting: almost all actually use the data capabilities. While some of that is attributable to the phone's useability, it's also the case that it has attracted existing data-oriented users. It also tends to come bundled with data plans. This contrasts with most other popular 3G phones, for which only a small minority regularly use data (or even have a data plan). I'll bet the average Nokia N95 or SonyEricsson K-series user wouldn't notice lousy 3G signal, because they only fire up the browser once a month.
- various blogs have commented on the new 2.0.2 firmware release, wondering whether it contains changes to the radio stack. Some have claimed that they're seeing more bars of signal strength subsequently - although the cynic in me suspects it's easier to change the signal-strength indicator software, than the underlying radio.
- AT&T has not previously had the consumer 3G dongle phenomenon take off the same way it has in many other countries (reflecting different pricing strategies). So its network engineers may be a little behind the curve on dealing with massive, sudden ramp-ups of data traffic growth, often in new and unexpected geographic locations. They're probably faced with a whole range of optimisation headaches, and may even be needing to split cells & find new locations.
- Expectations of WiFi-like performance by end users reading about HSDPA's "headline" speeds may have been unrealistic. Normally, WiFi AP's only have 1-3 users attached simultaneously, whereas a 3G base station might have hundreds - with the available capacity in a sector shared amongst them all. Then there's another set of questions about the backhaul capacity from the cell site, in comparison with WiFi which usually has a home/office broadband connection to exploit.
- Somewhere there must be some side-by-side comparisons of an iPhone running next to another 3G handset (Nokia, Moto, whatever) connected to the same operator's network. If there was a big performance delta, that would point the finger of blame clearly at the phone/chipset rather than the network.
- It could be that the radio chip or antenna has worse performance on AT&T's 1900MHz band than on most European operators' 2100MHz for some reason.
- I'd imagine that the density of iPhone users in the US is higher than in most other countries, and thus more likely to put a strain on AT&T's network in dense urban areas.

Based on what I've been reading, I'm more inclined to point the finger at AT&T than at Infineon. Its 3G network has (to date) been geared more towards corporate PC + datacard users - and I suspect it's realising that massmarket consumer usage patterns are very different indeed.


Anonymous said...

Very good analysis!!

Anonymous said...

dean, good post, but the problem seems to be worldwide, so i am not sure if it is just a problem that can be solved just by at&t engineers learning how to optimize the RAN...


Anonymous said...

good articles u mentioned above.

Anonymous said...

I agree with anon1, there have been wide complaints of the same headaches in Europe. And, the 2.0.2 doesn't seem to be working too well.


Anonymous said...

Agree. Dean needs to get out of his "all operators are assholes" mode. Its an iPhone problem, get over it.

Dean Bubley said...


I'm neutral towards operators - some do good things, some do poor things. Some do both. If you look through my archives you'll see a broadly 50/50 split of positive & negative opinions.

I say things how I see them. I don't mind criticising my clients where appropriate either. End of.

There also seems to be a broad split of opinion on the iPhone/AT&T thing. I've seen reports that the 3G Blackberry Bold suffers on the network as well, but then other stories have reported lab test issues with the iPhone. (And yet more have refuted this)

Some things remain indisputable:
- 3G iPhones seem to work well on a number of networks around the world (eg T-Mobile Germany, and I haven't seen many complaints about O2 UK)
- 3G iPhones don't work so well in parts of the US
- Some work so well in certain countries that I've heard reports of one operator actually deliberately throttling speeds for iPhones on their network

It could be that there's poor quality control on certain batches of iPhones. It could be that they tend to perform worse on certain frequency bands.

But in either case, given US operators normal extensive acceptance testing of new phones, I find it hard to imagine that AT&T has been caught out by faults that didn't appear in its labs. (Unless it is indeed a QC issue with recent batches of iPhones)