Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1998-08-14
2002-03-19
Patel, Ajit (Department: 2661)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S328000, C455S422100
Reexamination Certificate
active
06359904
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for data transfer in a digital mobile communications network, in which method it is handled user data in certain layers according to certain protocols, in a certain layer of said layers it is transferred user data over a physical radio channel between a mobile station and a fixed mobile communications network in radio blocks, for the transfer of said layer it is formed in the radio block a payload of a certain size comprising check bits connected with the performing of the transfer and transfer bits available for the transfer of user data, each radio block is channel coded using a certain coding method and the size of said payload is dependent on the coding method. The invention also relates to a transmitter/receiver device operating according to the method and a mobile communications system. The invention relates in particular to data transfer in the GSM-system in the GPRS-packet switched service.
BACKGROUND OF THE INVENTION
Out of the present mobile communications systems a majority is offering data- and voice services based upon circuit switched technique. In the circuit switched technique a transfer connection is maintained during the whole connection even if no information would be transferred time to time. This unnecessarily consumes the transfer resources, shared by also many other users, in which case the maintaining of a circuit switched transfer connection to one user consumes unnecessarily the transfer resources of other users. Because of the bursts in the GSM-transmission, data services are not optimal in the circuit switched technique. However, the packet switched information transfer for the increasing of the efficiency of the utilization of a channel is known.
As well as the fixed network also a future mobile communications network must be able to transfer both circuit switched and packet data transfer, e.g. ISDN-transfer (Integrated Services Digital Network) and ATM-transfer (Asynchronous Transfer Mode). For information transfer using packet switching it is known in mobile communications systems a protocol based upon packet reservation multiple access called PRMA (PRMA, Packet Reservation Multiple Access). It is also spoken of as packet radio. PRMA is a technique for multiplexing digital speech or data in a time division carrier wave, i.e. PRMA uses in a radio channel a time division multiple access (TDMA, Time Division Multiple Access), in which case transmission and reception take place at certain moments using time division. The PRMA-protocol has been developed to utilize the discontinuity of speech transfer in order to support more users than the number of speech channels in a time division carrier wave. In such a case a channel is allocated to a mobile station, for example a speech channel when speech is being produced and when the speaking ends the channel is released, in which case the mobile station does not unnecessarily reserve capacity, but the channel is channel is free for other purposes, for example the transmissions of other mobile stations in the cell. The PRMA-protocol is used in cellular mobile communications systems in the communication between a mobile station and a base station. The GSM GPRS (General Packet Radio Service)-system is an example of a system based upon a PRMA-type protocol.
GPRS is a new GSM-service, by using which the packet radio operation can be made available to GSM-users. GPRS reserves radio resources only when there is something to transmit, in which case the same resources are shared between all mobile stations as needed. The normal circuit switched network of the GSM-system has been designed for circuit switched speech transmissions. The main goal of the GPRS-service is to realize the connection from a mobile station to a public data network using prior known protocols, such as TCP/IP and X.25. However, there is a connection between the packet switched GPRS-service and the circuit switched services of the GSM-system. In a physical channel resources can be reused and certain signalling can be common to both. It is possible to reserve in the same carrier wave time slots for circuit switched use and for the packet switched GPRS-use.
FIG. 1
presents telecommunication network connections in a packet switched GPRS-service. The main element of the infrastructure of the network for GPRS-services is a GPRS-support node, so called GSN (GPRS Support Node). It is a mobility router which realizes the connecting and co-operation between different data networks, for instance to PSPDN (Packet Switched Packet Data Network) through interface Gi or to another operator's GPRS-network through interface Gp, mobility management using GPRS-registers over interface Gr and the transfer of data packets to mobile stations MS independent of their location. It is possible to integrate physically GPRS-node GSN with mobile switching center MSC (Mobile Switching Center) or it can be a separate network element based upon the architecture of data network routers. User data passes directly between support node GSN and base stations system BSS, consisting of base stations BTS and base station controllers BSC, through interface Gb, but between support node GSN and mobile switching center MSC there is signalling interface Gs. In
FIG. 1
the uninterrupted lines between blocks represent data traffic (i.e. the transfer of speech or data in a digital form) and the interrupted lines represent signalling. Physically the data can pass transparently over mobile switching center MSC. The radio interface between mobile station MS and the fixed network passes through base station BTS and it has been marked with reference Um. References Abis and A represent the interface with base station BTS and base station controller BSC, and respectively between base station controller BSC and mobile switching center MSC, which is a signalling connection. Reference Gn represents an interface between the different support nodes of the same operator. The support nodes are normally divided into gateway support nodes GGSN (Gateway GSN) and serving or home support nodes SGSN (Serving GSN) as presented FIG.
1
.
The GSM-system is a time division multiple access-type (TDMA, Time Division Multiple Access) system, in which the traffic in the radio path is time-divided and takes place in repeated TDMA-frames, each of which consists of several (eight) time slots. In each time slot it is transmitted an information packet in form of a radio frequency burst of finite duration consisting of a number of modulated bits. The time slots are mainly used as control channels and traffic channels. On the traffic channels it is transferred speech and data and in the control channels it is carried out signalling between base station BTS and mobile station MS.
In the following it is explained the protocols of GPRS and the protocol hierarchy in radio interface Um between mobile station MS and a fixed network (home support node SGSN) with reference to
FIG. 2
a
. User data is handled hierarchically on different levels, when it is converted into a form suited for the physical radio path and the public data network. On the highest level A) the user data (coming e.g. from an application App) is in a form suited for the protocol of the public data network, such as TCP/IP and X.25 and on the lowest level E) the data is in a form suited for transferring in the GSM-radio path.
The highest level A) protocol SNDCP (Subnetwork Dependent Convergent Protocol), i.e. a convergence protocol dependent of a subnetwork is explained in more detail in GSM radio specifications 04.65 and 03.60. According to SNDCP a network protocol data unit is segmented between mobile station MS and home support node SGSN into one or several SNDCP data units, the maximum size of the payload of which is approximately 1600 octets. The SNDCP-data unit is transferred in one LLC-fame (Logical Link Control) over the radio interface. The SNDCP-protocol includes multiplexing of user data, segmenting and compressing, and the compressing of the TCP/IP-header. It is possible to transfer
Hämäläinen Jari
Huttunen Kari
Leppisaari Arto
Nokia Mobile Phone Ltd.
Patel Ajit
Perman & Green LLP
Phunkulh Bob A.
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