Digital Signal Processing Reference
In-Depth Information
22 DVBH Digital Video Broadcasting for
Handhelds
22.1 Introduction
The introduction of 2G GSM (2nd generation Global System for Mobile
Communication) has triggered quite a boom for this wireless type of com-
munication. If the possession of car telephones or similar mobile-type tele-
phones was the prerogative of mostly special circles of people at the be-
ginning of the nineties, at least every second person had his own personal
mobile telephone by the end of the nineties and in most cases it was used
only either for telephoning or for sending and receiving short messages -
SMS - until then. By then, however, people also wanted to be able to send
and receive data via a mobile telephone, e.g. from a PC. To be able to
check one's e-mail database was initially a pleasant way of keeping oneself
up-to-date, especially in the professional field; today, this is standard us-
age. In the GSM standard, developed mainly for mobile telephony, how-
ever, the data rates are about 9600 bit/s. This is quite adequate for simple
text e-mails without attachments but becomes rather troublesome when
long files are attached to the original message. It can also be used for surf-
ing the Internet but is a cumbersome and expensive way of doing this.
With the introduction of 2.5G mobile telephony, the GPRS (General
Packet Radio System), the data rate was increased to 171.2 kbit/s by form-
ing packets, i.e. combining time slots of the GSM system. It was only with
the 3rd generation, the UMTS (Universal Mobile Telecommunication Sys-
tem), that the data rate could be increased to 144 - 384 kbit/s and 2 Mbit/s,
respectively which, however, greatly depends on the respective conditions
of reception and coverage. Using higher-level modulation (8PSK), the
EDGE (Enhanced Data Rates for GSM Evolution) standard, too, allows
higher data rates of up to 345.6 kbit/s (ECSD) and 473.6 kbit/s (EGPRS),
repectively.
Due to their nature, all mobile radio standards are designed for bi-
directional communication between the terminal and the base station. The
Search WWH ::
Custom Search