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Has your phone got UMTS or CDMA?…..what on earth?!

In my section on using mobile phones on board I keep referring obliquely to “modern phones”. One reader picked me up on this and asked me all sorts of questions about their phone. Unfortunately the reader was in the States so I did little bit of research on what is going on in the US with the mobile phones network. This is one technology where we in Europe can justly feel proud of the advanced technology that we get to use compared with our poor cousins in the USA,…sorry 🙂

Firstly – since many readers of this blog are all over the world you may have all sorts of technology being deployed at the same time even some quite old ones so watch out – even your laptop mobile broadband dongle that you just bought may still be out of date technology.

Originally data transmissions – which is what we are interested in on our boat – was sent over the analogue mobile phone network in much the same way as modems used to send data over computer dial up networks – i.e. as sounds -this practice even continued when the first GSM mobile network was deployed.

Stage 1 – CSD
The first digital systems for data was Circuit Switched Data (CSD). This is a real digital transmission of data using the GSM network. Unfortunately when the transmission left the GSM network to go to the internet for example – the transmission was converted back to analogue – and was not IP based – which is how the internet transmits data around the world. Data transfer was relatively slow: 14.4 kbps (kilobits per second) for GSM 1800 networks (Orange and T-Mobile) and 9.6 kbps for GSM 900 networks (Vodafone and O2).

Stage 1a – HSCD
HSCSD (High Speed Circuit Switched Data) enables data to be transferred more rapidly than the standard GSM (Circuit Switched Data) system by using multiple channels. The maximum number of timeslots that can be used is four, giving a maximum data transfer rate of 57.6 kbps (or 38.4 kbps on a GSM 900 network). HSCSD is more expensive to use than GPRS, because all four slots are used simultaneously – it does not transmit data in packets. Because of this, HSCSD is not as popular as GPRS and is being replaced by GPRS/EDGE.

Stage 2 – GPRS (or 2.5G)
Following this came GPRS – General Packet Radio Service. This is sometimes called 2.5G. This brought a full data channel of about 32/48kb/sec via the GPRS service to/from the internet. Most Blackberries use GPRS it is perfectly ok for email and light internet access. The class of a GPRS phone determines the speed at which data can be transferred. Technically the class refers to the number of timeslots available for upload (sending data from the phone) or download (receiving data from the network). The timeslots used for data are in addition to the slot that is reserved for voice calls. These timeslots are available simultaneously, so the greater the number of slots, the faster the data transfer speed. Because GPRS transmits data in packets, the timeslots are not in use all the time, but are shared amongst all users of the network. That increases the overall data capacity of the network, and it also means that you are billed for the quantity of data transmitted, not the time that you are online. It may mean that during busy times, data transfer rates slow down, because the network will give priority to voice calls.

GPRS Class Time slot Max Data Transfer Speed
Class 2 3 8 – 12 kbps upload / 16 – 24 kbps download
Class 4 4 8 – 12 kbps upload / 24 – 36 kbps download
Class 6 4 24 – 36 kbps upload / 24 – 36 kbps download
Class 8 5 8 – 12 kbps upload / 32 – 40 kbps download
Class 10 5 16 – 24 kbps upload / 32 – 48 kbps download
Class 12 5 32 – 48 kbps upload / 32 – 48 kbps download

Stage 2a – EDGE
An enhancement of GPRS is called EDGE or “Enhanced Data rates for GSM Evolution” – aren’t acronyms great 🙂 EDGE increases the speed of each timeslot to 48 kbps and allows the use of up to 8 timeslots, giving a maximum data transfer rate of 384 kbps.

Stage 3 – UMTS (or 3G)
This is the minimum standard for what I am calling a “modern phone”. Throughput should be up to 384kb/sec but because UMTS uses a different radio frequency to GPRS/GSM you should see a separate icon on your phone display indicating whether you have a “3G” signal or not. You can have one and not the other.

Stage 4 – HSDPA (or 3.5G)
An enhancement to UMTS/3G is High Speed Download Packet Access (HSDPA). This can give throughput from 14Mb/sec (downlink) and 6Mb/sec (uplink) – depending on your phone provider and proximity to a 3G aerial. This is sometime called 3.5G…

In the States they dont follow these standards of course ! They use CDMA (Code division multiple access)..

To see a summary of the GSM service around the world have a look at this site. If you are in the UK – then check out this site for extensive reviews of mobile phone networks and phones and their capabilities

The bottom line is that your “modern phone” in Europe at least..should have options to access data and the internet using all the standards from 2G upwards. These should be selectable in the configurations so that you can choose to not use HSDPA fro example if you suspect that you happen to be somewhere where there is a lot of competition for that signal e.g St Katherines Dock in the City of London, or Gosport Marina in Portsmouth perhaps – then setting your phone “down” to 2G or 2.5G may in fact get a better uncontended link to the local aerial and therefore better internet access on the phone, laptop dongle or laptop connected by phone to the internet.

..oh, and 4G is on the way


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