The history of mobile : part three

The history of mobile : part three

 

Hello fellow :

To complete our talk about the history of mobile and we started from generation two (G 2) :

The second generation of mobile communications (G2)

Second classifies tricks of mobile communications within digital systems supported by the treaties of international roaming, which allows for the possibility of running a mobile phone outside the international border of any country. Second-generation networks have much larger, with a capacity of capacity of the first-generation networks, which have been achieved by dividing the channel of communication between multiple users and other improvements to the system (such as the use of the hierarchical structure of the cells .

This generation is called 2.5G Name or GSM + +. The main problem in the GSM system is the data transfer rate radio (through the air) low, where the only 9.6kbps. System enabled  High Speed Circuit Switched Data (HSCSD) increase the cracks of time Slots to eight for data connections and thus increase the data transfer rate to 115kbps. Since the system is a system switch circuits Circuit Switched So is the allocation and use of cracks eight permanently even if there is not what needs to be sent, and this is one of the problems in this system.

In any case this system did not last long due to the increasing need to transfer data using systems that rely on switching Packet Switched parcels instead of circuit-switch technology Circuit .

In the absence of a unified body specializing in the development of global standards varied techniques, but the most famous Titles GSM in Europe, which laid a European standards body correspondence and then took the European Telecommunications Standards Institute to develop these standards. The first network operating according to the standards backhaul SM was in Finland in 1991 backhaul networks operate SM radio frequencies ranging from 900 Megahertz and 1800 Megahertz but in the United States operates backhaul networks SM at 850 Megahertz frequencies and 1900 Megahertz reason for this is that the frequencies the first was already booked there.

Introduced the second generation more services, such as the ability to send SMS messages and connect to the internet and global roaming service and emergency services and send and receive faxes and call forwarding to another number and prevent calls .... The maximum speed for data transfer were 20 KB or less than half of those in browsing through a regular phone ((Ground)) and a traditional modem.

With increased reliance on services for the first phase of the second generation became there is a need for further developments and improvements have given way to the so-called second-generation and half ((2.5 G)) is used to describe the systems operating between the second and third generation. The merger between the conversion between circuits ((Circuit Switching)) and packet transfer digital ((Packet Switching)) and provides data transfer faster updated across networks of second generation .

The following summary is the famous systems of the  second-generation systems :

General Packet Radio Service (GPRS)

This system provides a high data transfer rate of up to 115kbps. GPRS system is based on switching packages Packet Switched, so it does not allocate radio sources permanently fixed, but only when there is what needs to be sent .The GPRS system proportionate to non-real-time applications such as e-mail and surf the Web sites . GPRS system can be considered as a link between second-generation and third-generation mobile communications.

 

System consists GPRS network of Public Land Mobile Network (PLMN) based on the Protocol Internet Protocol (IP), Base Station System (BSS), Mobile Station (MS) in addition to the Mobile Switching Center (MSC) for access to the network switch circuits and databases.

PLMN is composed of:

• GPRS services support contract
Serving GPRS Support Nodes (SGSN)

• Support contract gateways GPRS
Gateway GPRS Support Nodes (SGSN)

The process of roaming by connecting a number of service areas PLMN, SGSN and GGSN with Home Local Register (HLR) and to retrieve profiles of users in order to facilitate the completion of the connection. GGSN offers the possibility of contact with parcels networks Data Packet Data Network (PDN) such as the Internet or a network of type 2.5G.

The BTS transmission and reception over the air (using CDMA, TDMA) and thus the delivery of voice and data wirelessly to the mobile phone MS. Directed BSC data connections to the service area PLMN using switch packages using link Frame Relay (FR), also directed voice communications to PLMN networks that use switching circuits such as PTSN and ISDN. The MSC requests from the VLR wandering store subscriber information.

Reverse process occurs in the target network PLMN and the BSS goal. In the sender of the data, shall be forwarded by the BSC data connections to the SGSN, then the data is converted to the external PDN through the GGSN or be converted to another subscriber on the cellular network.

GPRS system provided valuable services, but not voice services, that allows you to send and receive data via mobile phone networks. As the day progresses Short Message Service (SMS) and data transfer over  Circuit Switched Data.

For the rest of the interview . . . . to be continue in the fourth part of the history of mobile .