The Firehouse

It’s with surprise that I read a post on The Register and another on TUAW regarding the iPhone 3G’s speed, or lack thereof. The way 3G networks operate has some fundamental differences compared to GPRS or EDGE, the so-called 2G or 2.5G networks. A word of caution before you proceed, if you are a tech purist – I am explaining this in the simplest terms I can find, so don’t be offended by over-simplification.

“Scotty, we’ll need everything you’ve got.” ^[1]

Let me bore you with a primer on the “old” technology. In the very old days, packet data didn’t exist on GSM cellular networks. Each GSM frequency (also known as physical channel) would be split into eight full-rate (remeber the old EFR hacks?) timeslots, or sixteen half-rate. Voice was digitized using a vocoder, and transmitted to the cell tower using one of the timeslots. The tower then passed it along the switching network, to be terminated at another GSM terminal, or sent out to the PSTN where it could also be converted back to analog for further relay to landline phones. SMS would be sent over the control channel, thus not taking up timeslots for voice calls.

When data was first introduced to GSM, it was in the form of circuit-switched calls, the equivalent to the analog modems used in the early internet days. Since this was the equivalent of dialing a landline modem, the network could only provide one timeslot, and a brute rate of 9.6kbps (yeah, imagine the iPhone running on that!).

Then came GPRS, which brought packet-data to the phone, allowing the adjoining of several timeslots into one single packet-switched call, theoretically giving rates of 56 to 114kbps, which in reality could be as low as 9.6kbps, as cell operators would prioritize voice calls over data. The same occupation time of a timeslot on voice could earn the operator up to 10 times more than the same slot used for data. Thus, in the days when cell density was very low, and voice capability scarce, it was not uncommon to find that a tower would have only one timeslot reserved for GPRS and the rest for voice, sending you back to switched-call speeds.

I am the EDGE! ^[2]

When new modulation schemes and tighter timing capabilities made it possible, GPRS was upgraded to EDGE, which is an acronym for Enhanced Data rates for GSM Evolution. The theoretical maximum speed a packet-switched connection could now achieve was raised to 236.8kbps, with an upload speed of 59.2kbps. The upload and download speeds can be balanced to give a more symmetric connection, but this is rarely used.

Remember that we are still talking about chopping up a finite resource, a radio frequency channel, into smaller chunks, each of which can now carry data at increasing speeds, and also be aggregated to boost the overall transfer rate.

Slow? Twelve minutes? Hannibal, I had to say hello! ^[3]

One day in some lab, a fool invented CDMA. Well, not a fool, a very clever individual – just that the use of CDMA has been taken out of its initial expectations.

CDMA stands for Code Division Multiple Access. Contrary to GSM which uses TDMA, or Time Division Multiple Access, and divides the spectrum into timed slots for use by one mobile station at a time, CDMA allows ALL stations to talk to to the tower at once, with each given an individual code that is embedded in all transmissions. Then, using this code, the tower and terminal can tell who’s traffic it is amidst all the noise.

OK, it’s hard to imagine – let’s try a practical example. Imagine a room full of people, all talking at once to a host. The host gives each member of the public a phrase book in a different language, which they must use to translate what they want to say to the host. The host can then attempt to figure out who is saying what by figuring out the language of each utterance, and translating it back to the original. Sounds complex? You bet! The size of the room was also increased, whereas GSM used 200kHz of spectrum for its eight timeslots, 3G/UMTS using CDMA uses 5MHz, 25 times more spectrum, to achieve a theoretical maximum 14Mbps throughput. In practice, 3G HSDPA has only been able to achieve 7.2Mbps download so far, with HSUPA trying to improve the upload speed.

Before going further, if we compare the transfer speeds of each technology, EDGE can receive 1.18 kb/kHz, compared to 1.44 kb/kHz for HSDPA. Nothing to write home about, considering the huge costs this technology is having, I would say!

Stop it already, tell me what’s wrong with my iPhone!

What is basically wrong is that you have a beautiful screen on a beautiful mobile phone, capable of rendering full-size web pages…but you are sharing your internet connection with all your neighbors. In essence, 3G is allowing everyone to take a piece of the spectrum and use it to send and receive voice and data. This means a single 3G tower can handle a huge ammount of voice traffic, as it uses fewer resources, but when data is also added, it can be strongly degraded. I would venture that operators still prioritize voice over data on their 3G networks.

The key issue to remember is that the download rate is “per tower”, not per user. So, if two users using HSDPA are on the same tower, they will each get a maximum throughput of 3.6Mbps. Divide even further, and the more users you have the worse experience everyone gets. Further add tons of voice calls into the mix, and you have what The Register and TUAW describe in their posts – frustration. The blame may be at the iPhone’s radio, but from what I have been experiencing in Spain, Telefonica’s GPRS network provides almost as good speed as 3G in the very busy Barcelona. Why? Because my GPRS connection is getting better, as more voice traffic is dumped on the 3G networks, and I have more slots to myself!

Movie quotes:

1. Scotty in Star Trek, first series.
2. Aeon Flux in, well, Aeon Flux.
3. Face in The A-Team.

I visited this page which lets people give their details to Telefonica Movistar, and supposedly be sent information about the upcoming July 11th iPhone 3G release in Spain, for which they have exclusivity with Apple.

It seems that in earlier versions of this page, as iPhone Alley shows, Movistar showed a counter with the number of people that had submitted their details, but this counter is now gone. Worry not, however, as if you access this URL: http://www.iphone.movistar.es/cuenta_reg.php – it returns the number of signups to date. In the space of time it took to write this, the number went up by almost 30, standing at 141.723. Not bad, I guess the queues will be long at Telefonica stores this Friday!

While analyzing the future of WiFi against the expanding 3G networks, it seemed curious that AT&T recommends using WiFi while abroad, and even Apple seems to really love WiFi instead of EDGE.

My theory is that Apple is itching to release the next generation of the iPhone without carrier lock-ins such as the current AT&T deal. They know very well they can sell a 3G version with a better camera and maybe GPS for $800 to $1000 in Apple stores, and people will queue to take them off the shelves, to then stick whatever SIM card they want in it. They could then be smart and have per-carrier features like Visual Voicemail, which doesn’t bind them to the operator, but gives subscribers a slight edge over “plain” iPhone users.

Apple will continue promoting WiFi on the iPhone and iPod touch for two reasons: it’s way cheaper and way faster to get iTunes content onto them over WiFi (a couple of movies will bust most 3G “flat” fee plans, and take eons to download). With the reported ‘edge cache’ for iTunes media deployed at Starbucks, for example, it only makes sense to promote WiFi as the access technology of choice.

WiFi also knowns no boundaries, and is the only cost-effective way to use data while roaming abroad – remember all those horror stories of four-digit roaming data bills after the iPhone was launched? Would never happen using WiFi. With the new Exchange integration coming with firmware 2.0, many more business travellers will want to tap into WiFi while abroad without having to pop open the laptop. In my opinion, it all points to a long life for WiFi, alongside mobile access technologies such as 3G and WiMAX/LTE.

One has to wonder, when you read news like this, where Orange France is stating that their 500MB per month data plan, tied to the iPhone, excludes pretty much everything other than email and web browsing. So no VoIP, modem access for your laptop, or even newsgroups (??).

In Spain, Vodafone has been toting 5GB/month plans for some time now, with similar “fair use” policies. What is exactly the point of having such huge data plans, when all you can do is squint at the web on a tiny screen, or read your email – without trying to open attachments which are even harder to read. Granted, the iPhone has represented a leap in usability on these two fields, with fantastic web browsing, and very usable email where attachments can at least be useful. The only problem is the iPhone is one device lacking many functionality other platforms already enjoy, such as VoIP, decent IM, and…newsgroup access. These will come for sure, only because there is a very dedicated community of hackers porting and writing applications for it.

During my first month of iPhone use, when the novelty wants to make you try everything and, for example, browse the web when you don’t really need to, but just because it’s so cool – I went through about 70MB of data. Peanuts, compared to the 1GB plan I had with Vodafone…

My first BlackBerry was a 7100v, the first that had the slim form factor and two letters per key – which despite what anyone says, is still more uncomfortable than a full-sized thumb pad. After a couple of years, I have returned to the BlackBerry (but still keep a Nokia N93 handy for pictures & video), getting an 8708v from Vodafone. Main features are a slower non-Intel processor, but CDMA 3G/UMTS technology, which makes surfing and downloading attachments much faster than over GPRS.

After a couple of days of trying to load my favorite software on it, I realized that the 8707v has a very big, very upsetting flaw for anyone who wants to use it beyond email, scheduling and phone duty. It doesn’t have a TCP/IP stack, like other BlackBerries – so connectivity has to be through BES/MDS or BIS, leaving out many applications which need a direct socket connection, for example, the very excellent jmIrc, which kept on saying “could not open tunnel” when trying to get connected. Checking out BlackBerryForums, and Jan-Piet Mens’ blog, the truth started to sink in – RIM had deliberately left out the IP stack, citing unknown problems as the reason. The official statement is here.

Some applications worked, such as Idokorro’s rather good SSH client, and IM+, configured to use a BIS connection. Performance was very poor though, taking a very long time to establish any connection.

Yesterday, I remembered using Opera on the 7100v and being a nice browser than the built-in one, so I set off to download and install it. Not exactly sure how it used to be installed in the days of the 7100v, but this time, when launching Opera, it attempted to run through a series of “tests”, eleven in total, trying to determine how to get connected to the net…and they all failed. A few minutes later on BlackBerryForums, this little gem showed up – explaining the method to configure an APN for the mobile operator in question in order to allow TCP connections – but surely it had to be wrong, the article refered to the 8707v. Well it turned out to be correct, and now, I have a TCP section in Advanced Options, where I can enter an APN, user name and password. I went ahead and tried Vodafone’s APN for Spain, airtelnet.es (Vodafone’s entry into Spain was through the purchase of Airtel, and it seems some things always stay the same!), and it worked! jmIrc also succeeded in connecting to the Freenode IRC server, as all other applications that weren’t working did.

What did installing Opera Mini do? Add a service book? Unlock the dormant stack, or install it? If anyone has an explanation, please do let me know – and to those who were undecided about the 8707v due to the lack of IP connectivity, this seems to be a solution.

If you have a 3G/UMTS phone and you are moving around Barcelona, it is likely that since Wednesday morning you could not receive any voice calls or SMS messages. Vodafone admitted that they had a failure in some parts of the network in the city of Barcelona, but didn’t give an estimated timeline for fixing the problem. Today, at 4pm, they still do not have an estimated time to solve the problem, and I could still not receive calls. This is extremely serious, as anyone having to receive important or emergency calls will not get them, and he will not know a thing about it. Your phone shows you have coverage, and you can dial out, so you are unaware until you meet someone that yells at you because they couldn’t get in touch for hours.

Vodafone support is usually quite good, but in this case…they really blew it!