Communication: GSM Introduction

Showing posts with label GSM Introduction. Show all posts

Monday, February 2, 2009

Figure shows the GSM evolution steps according to how it is seen by most of the major cellular network suppliers and operators. The development is seen to go towards the 3G via intermediate high bit rate mobile communications systems.
The global GPRS market, together with HSCSD, is now beginning to take off. The introduction of GPRS is one of the key steps in the evolution of today’s GSM networks to 3G. GSM operators around the world are upgrading their networks, with a view to launching commercial GPRS services in 2000. UMTS services will launch commercially from 2002.

WCDMA is a totally new radio access technology which is not anymore based on GSM radio frequency but brings a completely new modulation method. It can provide a high capacity radio interface to the GSM core network, though. WCDMA will provide access at up to 2 Mbit/s in the local area and less than 1 Mbit/s wide area access with full mobility. These higher data rates require a wide radio frequency band, which is why a WCDMA with 5MHz carrier has been selected. This corresponds to the 200 kHz carrier for GSM.

EDGE, a new radio interface technology with enhanced modulation increases the HSCSD and GPRS bit rates by up to three folds. EDGE air interface channel coding offers approximately 48 kbit/s per air interface traffic channel. Consequently Enhanced GPRS (EGRPS), as it is referred to, offers theoretically 384 kbit/s bit rate by using all eight air interface time slots.

GPRS provides mobile subscribers with packet switched connection to packet data networks, like the Internet or corporate networks. GPRS will offer a tenfold increase in data throughput rates, from 9.6 kbit/s to 115 kbit/s. The maximum bit rate, theoretically, is 171.2 kbit/s which is achieved using 8 air interface time slots simultaneously. In GPRS, a separate IP backbone network will be introduced which acts as an interface between GSM and packet data networks, like the Internet.

HSCSD is a circuit switched connection over a standard GSM network. The channel speed of HSCSD is 14.4 kbit/s and it provides a possibility to use multiple time slots for the data transmission. The first commercial HSCSD mobile stations will be capable to use up to four time slots simultaneously.

As mentioned in the previous section, the air interface is the bottleneck when transmitting data between a mobile station and a data network using the current mobile services. A major part of the evolution of mobile data communications services is dependent on the evolution of the GSM.
GSM radio access technology has a clear evolution path and, eventually, it will provide a bandwidth wide enough for various kinds of services. Hence, GSM radio technology will remain an essential access network well into the next century.

Today, the cellular networks are evolving to meet the new requirements of mobile data communications. The target of the mobile communications system development is to create service that is able to offer global coverage with multi-media access speed. Today, satisfactory mobile data communications are possible only via a second generation digital mobile communications network. The world's most advanced and wide spread second generation mobile network is GSM (Global System for Mobile Communications).
There are two methods how data can be transferred in GSM: Short Message Service (SMS) and GSM data service. Both of them enable 9.6 kbit/s circuit switched connection. However, data transmission capabilities of SMS are much more restricted and thus it is only suitable for transmitting short text messages.
There are several drawbacks in the second generation GSM being a bearer service for data. For example, the bit rate of the GSM radio access network is very low, thus clearly acting as a bottleneck in the end-to-end system. In addition, a relatively long connection setup time and the typical restrictions of a circuit switched connection method in data transmission limit data applications to be offered.