UMTS networks
UMTS is the third generation of mobile networks and besides this it's a new type of network. UMTS is a new standard for Europe and Asia and after a while it will substitute and take over the current GSM standard. By UMTS more and more multimedia services will be available on the cellular phone.
UMTS networks emit on a frequency around 2000 Mhz. This is a high frequency (as a comparison, a car radio receives a frequency around 100 Mhz). A high frequency has a couple of big advantages. The (digital) network isn't interrupted by the influences of the weather. A result of this is that you have a crystal clear connection most of the times. Another advantage of a high frequency is that you only need a small antenna and because of this the portability of your cellular phone is a lot better. Although, the higher the frequency the smaller the reach. The frequency of UMTS networks is higher then the frequency of other cellular phone networks. The frequencies of cellular phone networks start at 850 Mhz and end at a little higher then 1900 Mhz.
In general there are seven cellular phone networks in the world. These networks are: UMTS 850 Mhz (especially in South and Latin America), GSM-R, E-GSM, 900 Mhz, 1800 Mhz networks (Europe and big parts of Asia) and 1900 Mhz networks (North America). All other types of networks except the UMTS network are handled elsewehere within this helpdesk.
1800 Mhz is a relatively high frequency for cellular phones. Because of this UMTS networks have a smaller and less penetrating reach then GSM networks. By this the reach in big buildings is low. For a good cover there are more masts needed and more mini antennas (repeaters) needed in buildings. An advantage of UMTS networks is that the capacity is bigger then the capacity of networks that emit on a lower frequention.
UMTS networks can offer a higher speed then GSM networks can, the frequency of UMTS networks isn't far away from the frequencies that GSM networks use. The high speed can be offered because the available capacity is better classified by the UMTS standard.
GSM networks use the TDMA-technique (Time Division Multiple Acces). Through TDMA a maximum of 8 callers can use one frequency at the same time. This frequency has a frequency width of 200 Khz. By giving every caller its own timelock at the frequency or a so-called emit moment once in a period of time, one frequency can be used by 8 callers at the same moment. The emitting at cellular phones takes as it were its turns and this goes that fast that the caller can't hear this. In the contrary TDMA is still inefficient because the silent moments are also emitted (because once in a period of time there is an emit moment). GPRS was the answer to that. When you use GPRS you only get a timelock when you are actually emitting something, by this a higher speed can be made by using GPRS.
The UMTS standard uses the W-CDMA-technique (Wideband Code Division Multiple Acces). This new technique can cope with an unending amount of users. W-CMDA doesn't use a fixed frequency width (just as GSM 200 Khz) but the width of a frequency is allocated to the amount of datatraffic that a user consumes. A user that doesn't talk that much or doesn't send much doesn't need much space at the frequency width, a user that talks a lot or sends a lot gets more space at the frequency width.
Every user within an UMTS network gets it's own cipher at it's datatraffic. This cipher is deciphered at the other side. In theory, by using an unending amount of ciphers an unending amount of users can utilize an UMTS network. When there are a lot of users at the same time some rustle can occur because of the amount of users.
The speed of UMTS in comparison with GSM (9,6 kbit/s) and GPRS (14,4 untill 57,6 kbit/s) will rise. A speed that stops at 384 kbit/s will be possible, this is a speed that can be compared to a small ADSL connection. By using this high speed, applications such as video calling, streaming music or video will not only be accessible by "normal" internet users.
|