GSM Mobile Network – mobile network of 2nd generation
GPRS Data Transmission in GSM Network

In order to increase the transmission rate in the original GSM network, which is solely circuit oriented, packet oriented transmission mode had to be introduced. For this purpose, it is necessary to supplement the original network by new equipments as it is shown in the figure below. This new network structure enables packet oriented transmission called as GPRS.

Data transmission through GPRS

Data node, SGSN, communicates with the radio part of GPRS network. For the data transfer to other packet networks, such as the Internet, a GGSN data gateway is used; this entity acts as a router. Access of user into defined networks is allowed through APN (Access Point Name). This way, the operator can enable access to given APN only for defined set of SIM cards and can thus to create a GPRS network for the private group of users, whose traffic is strictly separated from other traffic. From the information mentioned above, public data networks or private data networks can be created by this way. Transmitting data through the APN can be also a different way how to determine price for individual service of provider, such as WAP (Wireless Application Protocol) or MMS (Multimedia Messaging Service).

Access to the Internet is possible by WAP, which makes accessible the content of the web sites and information services on MSs through low-capacity channels and displays with limited resolution. The application of data communication and WAP allow utilization of GPRS (packet oriented transmission) and enhancement of transfer rates theoretically up to 192 kbps. However, the implementation of this service requires much more extensive and costly investments not only in the structure of the GSM network, but also in the MSs.

Within the GSM network with GPRS is already implemented cooperation between SGSN and BSC for efficient allocation of transmission resources, which means that transmission resources are allocated to the MS only if it has data to send or receive.

There are not permanently blocked transmission paths unlike in the conventional data transmission in GSM network using HSCSD.

Higher transfer rates of GPRS are enabled by association of more than one timeslots for a user and by selecting a suitable coding system for this channel. In this context, we refer to transmission using combination of 3+1, 4+1 or 4+2 timeslots (represents downlink + uplink). If asymmetrical data transmission is used in the GPRS, then the direction to the subscriber (downlink) is always of a higher transfer rate. The available transmission rates are strongly dependent on the specific location and BS load.

A negative impact of delay can be observed in GSM network with GPRS. It is caused by data packets passing through packet oriented networks. The delay is strongly dependent on the length of packets. Short packets (up to 100 bytes) have the transmission delay from 0.5 up to 1 second depending on the network load. Moreover, packets with length of 1 kB can be delayed even few seconds.