Table of Contents
Advertisement
Départ. Technical support- CM640
PHILIPS Consumer
Communications
Centre du Mans
7.9.3
Technical characteristics
Circuit switched mode or virtual access
The first advantage of the GPRS is to allow a better use of the radio and technical resources. While the GSM works
in "connected" mode, called also "circuit-switched" mode, the GPRS uses for its part the virtual connection mode.
In "virtual" mode, the resources are shared. The transmission channel is never allocated to a unique user, but
shared between several users. Every user has it when he needs it and only in that case. The rest of the time they
are available. The circuit switched mode corresponds to the functioning of a GSM line or still a standard telephone
line. It consists in establishing a physical link between two points or two correspondents. Once the number is
dialled, a circuit is permanently allocated to the communication, without any sharing with the other customers. This
mode of functioning which does not take into account periods of silence, when no data is passed on, does not
optimise at its best the radio resources.
The GPRS puts in evidence the more important role of the network administrator. In a GSM infrastructure the role
of the administrator amounts to affect physical resources at the beginning of every communication. With the GPRS,
its role is more important. It consists in assigning, in real time, the physical resources (memories and electronic
circuits), in managing the radio resources, and in affecting them according to the demand.
The GPRS settles down on the existing GSM network
The GPRS-system is built upon the existing GSM-infrastructure. Basic stations undergo no modification with
exception of the specific software, that can be installed by downloading.
Next, the Basic Stations Controller (BSC) should be doubled by a Packet Controller Unit (PCU).
Then comes the path intended for data packets, its composed of :
- The Serving GPRS Specific Node (SGSN) , equivalent of the Mobile Switch Controller ( MSC), which aims to
check subscribers registering , to authenticate them and to authorise the communications,
- The Access module (GGSN) to the IP world (Internet or Intranet).
GGSN and SGSN are described later.
PHILIPS ELECTRONICS N.V. 1999
All rights reserved. Reproduction in whole
or in part is prohibited without the written
consent of the copyright owner.
PROCEDURE
Service Repair Support
COMPANY RESTRICTED
VY-V-640-82x
Page : 18 of 71
Langue : EN
Date : 25/02/03
VY-V-640-82x
Advertisement
Table of Contents
