GPRS & DECT & IS-95

GPRS

1) Characteristics of the GPRS:

The GPRS has been thought and developed in order to concur I use it of the cellular one also for multimediali applications, to such aim it is sceltor the following approach:

to)       tariffazione based on the volume and not on the time

b)       commutation of package instead that of circuit

c)       net parallel to puts into effect them net GSM

d)       GPRS finishes them is always connects to you but the resource radio is only used when finishes sends they or receives packages

 

2) Defects of the GPRS:

to)       the resource to disposition for the transmission given, it is the same one that comes also used for the transmission of the voice and therefore at the moment it is insufficient.

b)       the date installments of 172.2kbit/s is only theoretical, in how much it previews that the 8 slot they are all dedicates you to a single channel, only EDGE and UMTS will be in a position to increasing really the given speed of the transmission.

c)       Demands of finishes them furnitures purposely plans you for the GPRS.

d)       To the contrary of EDGE and UMTS that use a 8PSK, the GPRS uses the GMSK (gaussian Minimum Shift Keying) that from inferior performances regarding the previous one.

 

3) Architecture of net:

The net is parallel to net GSM puts into effect them, demands only the added one of two entity:

to)       SGSN

Serving GPRS Support Node is the equivalent of the MSC for the circuit commutation, is connected to the BTS and it is taken care to capture the packages, to carry out of the tunnelling and to transmit them to other SGSN or a GGSN

b)       GGSN

Gateway GPRS Support Node is taken care of instragive the packages towards the fixed net to package commutation let alone towards other nets GPRS

 

4) Tunnelling:

There are various nets to commutation of package in the world and these have wefts with various characteristics, the GPRS is proposed of not ago interfacciarsi to all and therefore other that to enclose the generic packages in a cocoon before the transmission and to eliminate such cocoon once that the package is reached destination.

DECT

5) Characteristics of channel DECT:

The DECT is not other that an interface radio towards net PSTN regarding the GMS concurs but to obtain greater speeds in how much can realize of the asymmetric connections, that they are those normally present ones in the transmission given.

 

6) Radio ducts:

There are 10 carrying from 1880MHz to 1900MHz, they are spaced of 1728kHz from the other, on ognuna comes true a weft TDMA to 1152kbit/s with 24 slot, the first 12 dedicates you to the downlink and successes to you 12 to the uplink, a TDD is had therefore.

Every RFP (Radio Fixed Part) pu² to manage a single one carrying to the time therefore is possible single 12 contemporary conversations carried out for means of PP (Portable Part).

 

7) Weft:

Draft of a TDMA/TDD in which the weft of 24 hard Time slot 10ms, the first 12 Time slot are dedicates you to the downlink while the following 12 to uplink however the allocation can also be reviews in function of the demands for the connection.

 

8) GMSK:

It is a modulation of phase to constant envelope that obtains one beginning from QPSK sfasando of a time of bit the flows on the channel p and on the channel q.

 

9) Types of Bearer:

There are 3 types of Bearer, the simplex it previews that it is transmitted alone in the first 12 slot, then is the two-station communication and the double simplex which it realizes a particularly useful strongly asymmetric connection in the Internet logon.

 

10) Structure of net DECT:

Every RFP manages a microcell that in atmospheres sluices can cover until 100m while in atmospheres opened until 300m, it has all and the 10 carrying radios to disposition of system DECT, on they ago measures in the moments in which it does not transmit the burst in order to serve the PP, in this way chooses always better carrying in order to continue the service and the planning of the frequencies is not necessary.

 

11) dynamics Allocation of the channels:

Every cell has to disposition all the channels, it is finishes them to choose which cell to connect itself and to manage the eventual one handover towards a base that it supplies marks them more fort.

IS-95

12) Block interleaving:

To the aim to avoid that of the burst they damage the intelleggibilità of the information, bit that they would have to be adjacent from a logical point of view comes separates to you by means of a interleaving that in short matrix consists in loading one on the columns and to read it from the lines.

 

13) Receiver RAKE:

He is a receiver constituted from 4 demodulatores that are coupled to 3 various ones walk multiple associate you to the same information, then is a fourth demodulatore that tries in air if there is some multiple way that has a quality of marks them greater.