What the heck is 3.5G?

Whilst shopping recently in Madeira I was stopped short by a large banner in a mobile phone store depicting 3.5G. Now I consider myself pretty network savvy, but what the heck is 3.5G? If you’ve been around mobile wireless you’re...

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Whilst shopping recently in Madeira I was stopped short by a large banner in a mobile phone store depicting 3.5G. Now I consider myself pretty network savvy, but what the heck is 3.5G?

If you’ve been around mobile wireless you’re probably already aware that 3G doesn’t particularly mean anything technically specific to the mobile providers’ marketing departments. It’s just been a marketing slogan which applied to a number of high speed standards. Basically then 3G is a marketing slogan that is faster than “2G", and 2G itself has a number of variants at times referred to as 2.5G (GPRS), and 2.75G (sometimes even known as 2.9G-Edge).

So, I thought it would be worth looking at what 3.5G is, and when we are sold a service like 3G what are we actually getting? We need to get into the detail to understand more, but before I do that, running alongside the marketing terms there are some actual definitions from the ITU (International Telecommunications Union).

To the ITU, 2G and 3G actually mean something; it’s standards-based, and interestingly the ‘Edge’ technology that was bandied around as a 2.75G (or 2.9G) technology, is, from an ITU perspective, actually a 3G technology. So we can see how the marketers have played with these terms.

If you Google search for 3.5G, used as a marketing term in some countries, the actual technology is called HSPA, and if you look up HSPA you will find there are a number of variants of it: HSUPA has a much faster uplink, than HSPDA which favours the downlink side (a network asymmetry which would improve web browsing in the latter and photo uploads in the former) and then there’s HSPA+ which tries to offer the best of both these worlds.

So are we actually getting any of these? For iPhone users, when connected to a 3G service the phone simply says 3G; the original 3G was, by today’s standards, quite a slow service at 384Kbps (with whole heaps of latency dramatically slowing down the connection further). But even though what’s displayed on the iPhone is "3G", in truth the device might be getting an HSPA type connection: HSUPA, HSPDA or HSPA+. It just doesn’t tell you.

Interestingly, those of you that are using an Android device will sometimes see a little letter in the top bar called ‘H' as well as seeing 3G. 3G on the Android device means the original 3G service; 384Kbps and ‘H’ means the device is getting HSPDA, which goes from a few megabits a second up to a maximum of 14.4Mbps at the HSPA+ level (theoretically). So, an Android device already differentiates between 3G and 3.5G (H).

We have this conflict of what the marketers of the mobile companies are actually selling us, where they freely bandy terms 2G, 2.5G and 2.75G (2.9G), with the implication that 3.5G was better than 3G but not 4G.

So what changes when they finally launch 4G on us? For those who have been watching this space, you will know that what they are actually referring to here is a new mobile data technology properly called 3GPP LTE (Long Term Evolution) that promises much higher data rates.

The ITU says that LTE falls short of being a proper 4G technology, and we now have another conflict with the marketeers. By ITU standards, LTE is in fact 3.9G — in other words still a 3G technology but a very fast and advanced one, approaching but not achieving all the 4G requirements.

This means the marketing term 4G is actually incorrect for LTE. But I don’t think we should worry about that; what we should be concerned about more is speed, latency and loss, and certainly LTE is aiming for very high speeds and low latencies.

In a recent blog I discussed I discussed the likelihood of us actually seeing those promised speeds. According to the ITU it won’t be until another standard called ‘LTE advanced’ appears before LTE becomes a proper 4G technology, at which point marketing definitions and standards will have converged for a while.

In conclusion: All of these terms - 2G, 2.5G, 2.75G, 2.9G, 3G and 3.5G that you see are all marketing and in some cases misused —  so LTE is not really 4G, and Edge was a 3G technology and but called 3G.

The hype bears only a passing resemblance to the underlying technology, and now we have LTE which is actually a 3G technology (be it advanced) that is about to be branded as 4G for convenience. But, the truth of it is you don’t care; what you care about is the speed that you are going to get, which is principally dependent on the technology being used.

Don’t rely on what the marketers are advertising (2G, 3G or 4G). If you know that what you are really getting is HSPA+ (a 3G technology) for example, you can look at the advertised data rates for the up and down link speeds and typical latencies.

I’ll go back to the iPhone on this one - when the iPhone displays 3G you could be getting anything from 384Kbps to 14.4Mbps and I’m not allowing for contention between users or issues in the mobile provider’s back haul. As always, caveat emptor!


By Frank Puranik, Product Director, iTrinegy

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