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it can be that slow, if the operator built a crap system or if the system is given, but isnt that far developed, as the amount of the users. at more connections ( more uers in the same time as the system it allowes ) it gets slow. it happens to easto from time to time as well, shown " too many connections"
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Posted: 2007-05-05 20:35:02
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Hi,
to try and answer your oringal question.
First we have GSM, which origanlly was on the 900MHz frequency band. The GSM specification was enhanced with GPRS (packet data) for speeds up to 115 kbps (theoritical, 30 to 40 in reality). After GPRS, the GSM specification was further enhanced with EDGE, to support up about 200 kbps (about 100 to 150 in reality).
In radio specifications it is normal to specify the "peak data rate" i.e. the maximum possible bit rate (in GSM that is governed by the modulation scheme used and the number of timeslots allocated). It is rare to achieve these peak rates outside of lab conditions, because radio is a shared media and must be shared by all users in the cell (for voice and data). In live networks it is rare you can get the max possible resource allocation (because other people would also like to send data or make a call). In addition to that, interference and other problems means you rarely get the highest modulation scheme (the higher the modulation scheme, the higher the bit rate, but as you move away from the base station you get weaker signals and more interference, so you need more robust modulation schemes, i.e. lower modulation and lower bit rates).
As the 900 Mhz band was being filled to capacity, 1800 MHz was specified for GSM to allow for expansion (i.e. more capacity = more users).
Hence GSM is in the 900 and 1800MHz frequency bands worldwide, except the USA.
In the US, 900 & 1800 MHz is not available. Hence for the US market (but also for a few other countries), 1900MHz was specified for GSM.
Hence today the majority of GSM phones are tri-band, 900, 1800 & 1900 MHz to be able to work worldwide.
In recent years in the US, the 850MHz band became available for GSM and there are 850MHz GSM phones out there, typically tri-band 850, 1800 & 1900MHz or quad-band 850, 900, 1800 & 1900MHz.
When it came to 3G, the orginal specification for WCDMA (often referred to as Release 99 or R99 to indicate what year it was specified) it was decided that up to 2Mbps should be supported and a new technology needed a new spectrum allocation. Worldwide 2100MHz was identified as the spectrum band for WCDMA. The specification for WCDMA R99 does support up to 2Mbps, but in reality (mainly because of complexity & cost) most WCDMA networks & phones only support a max of 384 kbps.
Like GSM, it is rare you will achieve 384kbps outside a lab and speeds between 200 and 300 kbps are more common.
Also, to avoid having to rollout WCDMA nationwide on day 1, it was specified how to hand over from WCDMA to GSM (and vice versa). This meant you could start a voice call (or packet data session) on WCDMA and if you moved outside coverage handover to GSM. Hence most 3G phones typically support WCDMA on 2100MHz and GSM on tri-band 900, 1800 & 1900MHz.
Once again, 2100MHz was not available in the US, so for the US the 850 and 1900MHz frequency bands were specified for WCDMA as well.
It is only this year we are seeing the first quad-band 850, 900, 1800 & 1900MHz GSM + tri-band 850, 1900 & 2100MHz WCDMA terminals becoming available.
The next evolution step after WCDMA R99 (which covers voice & data) was to enhance the data speeds. So it was decided in release 5 (they changed the release numbering scheme as well, to make sure you were confused)
to enhance the downlink packet speeds, to support a peak data rate of 14Mbps. This is called HSDPA (High Speed Downlink Packet Data Access).
However to achieve 14Mbps you need a terminal (mobile) that supports up to 20 codes (in WCDMA you use codes, instead of timeslots). However this is both complex and costly. So the first generation of terminals only supported 2 codes (which is 1.8Mps). Then there were terminals that could support 5 codes (3.8Mbps) and finally there are a few terminals on the market capable of 10 codes (7.6Mbps). It is unlikely (but not impossible) we will see terminals (mobiles) capable of supporting the full 14Mbps any time soon.
In release 5, you are still limited to 384kbits on the uplink. So in release 6 (which we will see deployed in the market this year) they enhanced the uplink, called HUSPA (High Speed Uplink Packet Data Access) to support up to 5.6Mbps (although again, for complexity and cost reasons most first gen mobile terminals will only support 1.6Mbps on the uplink).
More commonly, HSDPA + HSUPA are referred to as simply HSPA (High Speed Packet Access).
In the future (release 7 and release 8 ) we will see the specfication for HSPA enchanced with MIMO to support 28 Mbps and later also higher modulation schemes as well, to boost peak data rates to 42Mbps.
Finally, to finish, you asked what is UMTS ? Well UMTS is the Universal Mobile Telephony System. It is the requirement specification for a 3G mobile telephony network. It comes from ITU (International Telecommunication Union).
You see GSM, WCDMA, HSPA all these lovely acroymns only refer to the radio interface. For a true mobile telephony system you need to specify the entire network inter-working (how to authenticate end users, how to sign on to the network, how to do roaming, how to do hand overs, charging etc.).
So 3GPP (an organisation that makes the specifications) covers the entire network architecture. 3GPP makes the specficiations for how it all works (according to the ITU requirements) and this is then sent to ITU to get it accepted internationally (which is why your mobile phone works when on holiday in Spain)
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I hope this helps and is not too confusing,
/Mike B.
[ This Message was edited by: mikeb on 2007-05-06 18:46 ]
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Posted: 2007-05-05 21:43:20
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Helped, in my case...
thanks...
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Posted: 2007-05-07 03:54:00
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Haha america is obviously left behind china. China is about to implement 4G, and you're talking about 3G here
and wikiPOOdia isn't a reliable resource...
Actually in some countries, wcdma/umts billing systems are provided in both time-based and data-based so users have an option which one to use.
And mike, good posting pal
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Posted: 2007-05-07 07:05:00
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