The invention also relates to a method for controlling quality of service in a packet radio system comprising a network part, at least one sub- scriber terminal and a bi-directional radio connection between the network part and the subscriber terminal, where the bi-directional radio connection is used for connection establishment and packet transmission, each subscriber termi- nal is provided with a specific service class, one or more radio connections use the same radio resource, and the subscriber terminal simultaneously em- ploys more than one applications of different levels.

The invention further relates to a packet radio system comprising a network part, at least one subscriber terminal and a bi-directional radio con- nection between the network part and the subscriber terminal, where the bi- directional radio connection is used for connection establishment and packet transmission, each subscriber terminal is provided with a specific service class, one or more radio connections are arranged to use the same radio re- source, and the mobile telephone network is arranged to provide the sub- scriber terminals with a desired amount of data transmission resources based on the service class of each subscriber terminal.

The invention also relates to a packet radio system comprising a network part, at least one subscriber terminal and a bi-directional radio con- nection between the network part and the subscriber terminal, where the bi- directional radio connection is used for connection establishment and packet transmission, each subscriber terminal is provided with a specific service class, one or more radio connections are arranged to use the same radio re-

source, and the subscriber terminal simultaneously employs more than one applications of different levels.

BACKGROUND OF THE INVENTION A packet radio system refers to a radio system using packet- switched technology known from the field of fixed networks. Packet switching is a method where a connection is established between users by transmitting data as packets containing address and control information. Several connec- tions can simultaneously use the same data link. The use of packet-switched radio systems has been studied in particular, since the packet-switched method is well suited for data transmission, where the data to be transmitted is created in bursts. Then, the data transmission link does not have to be allo- cated for the whole time, only for packet transmission. Significant cost and ca- pacity savings can thus be achieved during the construction and operation stages of the network.

Packet radio networks are currently particularly interesting subjects as the GSM system is being further improved, reference is then made to GPRS (General Packet Radio Service). An ETSI GSM specification (ETSI GSM 03.64) describes, for example, the air interface between the network part and the subscriber terminal in GPRS.

According to prior art data transmission at the GPRS system inter- face is carried out in packet-mode. When transmitting packet-mode data to a subscriber terminal the mobile telephone network has to allocate a radio re- source to the subscriber terminal. The subscriber identifies the data intended for him/her by means of the radio resource allocated to the subscriber. The subscriber terminals are divided into service classes, or what are known as QoS classes (QoS, Quality of Service), according to which some users can be provided with more data transmission resources than other users.

However, a drawback with the above system is that it is not possible to provide data transmissions of different service classes with a different amount of radio resources and thus also to ensure reliable service. According to prior art the transmission order of data packets by applying the same radio resource, for example in a loading situation, can be prioritized to be dependent on the service class in such a manner that the data transmission of a higher priority subscriber is completed before data transmission is initiated for the following subscriber. However, it is thus impossible to ensure that service will

be provided, since a higher priority subscriber always obtains service before a lower priority subscriber.

BRIEF DESCRIPTION OF THE INVENTION It is an object of the invention to provide a method for controlling quality of service in a packet radio system and a packet radio system so as to solve the above problems. This is achieved with the method set forth in the preamble, characterized by controlling the quality of service with the amount of data sent to the subscriber terminals in one transmission. The method is also characterized by application-specifically controlling the quality of service in the subscriber terminal among applications of different levels with the amount of data sent in one transmission to said applications. The packet radio system of the invention is, in turn, characterized by the packet radio system network part being arranged to control the amount of data to be sent to the subscriber ter- minal in one transmission. The packet radio system is also characterized by the subscriber terminal comprising an application-specific quality of service control among applications of different levels with the amount of data to be sent in one transmission to said applications. The preferred embodiments of the invention are disclosed in the dependent claims.

The invention is based on the idea that subscriber terminals allo- cated to the same radio resource are served in turn. Of the subscriber termi- nals allocated to the same radio resource the subscriber terminal to be served is switched to the following always when the mobile telephone network re- quests acknowledgement of the data blocks sent to the previous subscriber terminal. In the invention, the service time may vary among subscribers of dif- ferent service classes. By controlling the length of an acknowledgement se- quence, i. e. the amount of data sent to each subscriber terminal in one trans- mission, among different subscribers the data transmissions of various service classes can be provided with a different amount of radio resources, or trans- mission time.

Several advantages are achieved with the method and system of the invention. A mobile telephone network can control the quality of service, i. e. the speed and efficiency of data transmission, depending on the sub- scriber's service class. Then, some users can be provided with more data transmission resources than other users. This enables the prioritization of the subscriber terminals in a predetermined manner.

Furthermore, for example, in a loading situation the different quality of service level offered by the base station system ensures that each sub- scriber terminal obtains at least some kind of service. Data transmission de- lays are thus fairly divided among various subscriber terminals in such a man- ner that the subscriber terminals requiring better quality of service obtain on average more data transmission time, but the subscriber terminals requiring poor quality of service are not completely left without data transmission re- sources.

BRIEF DESCRIPTION OF THE DRAWING In the following the invention will be described in greater detail in connection with the preferred embodiments with reference to Figure 1 showing a cellular radio network as a block diagram.

DETAILED DESCRIPTION OF THE INVENTION Figure 1 describes a typical structure of a cellular radio network of the invention and connections thereof to a fixed telephone network and a packet transmission network. Figure 1 comprises only parts essential for the description of the invention, but for those skilled in the art it is obvious that a conventional cellular radio network comprises other functions and structures too, which will not be explained in greater detail in this context.

The cellular radio network comprises a network part 100,102,132, 140 and a subscriber terminal 150. The network part 100,102,132,140 in- cludes base stations 100 which have a bi-directional radio connection 170 to the subscriber terminal 150, the radio connection 170 sending a radio signal at a particular carrier frequency. The subscriber terminals 150 can be fixedly mounted, vehicle-mounted or hand-held portable terminals. Several base sta- tions 100 are, in turn, controlled in a centralized manner by a base station controller 102 communicating with them. The base station 100 comprises transceivers 114, typically one to sixteen transceivers 114. One transceiver 114 offers radio capacity to one TDMA frame i. e. typically to eight time slots.

The base station 100 comprises a control unit 118 controlling the operation of the transceivers 114 and a multiplexer 116. The multiplexer 116 locates traffic and control channels used by several transceivers 114 to a sin- gle data link 160. The structure of the data link 160 is accurately determined and referred to as an Abis interface. The data link 160 is typically implemented

using a 2 Mbit/s link, or a PCM link (Pulse Coded Modulation).

There is a connection from the transceivers 114 of the base station 100 to an antenna unit 112 implementing the bi-directional radio connection 170 to the subscriber terminal 150. The bi-directional radio connection 170 is used for connection establishment and packet transmission. The structure of the frames to be transmitted also on the bi-directional radio connection 170 is accurately determined and referred to as an air interface.

The subscriber terminal 150 can be, for example, a standard GSM mobile phone, whereto a laptop computer 152 that can be used in packet transmission for ordering and processing packets can be connected using an additional card. Protocol processing can be placed in the subscriber terminal 150 and/or in the computer 152 connected to the subscriber terminal 150.

A base station controller 102 establishes a connection with the sub- scriber terminal 150 by requesting the base station 100 to send a message to the subscriber terminal 150 for connection establishment. The base station controller 102 comprises a group switching field 120 and a control unit 124.

The group switching field 120 is used to switch speech and data and to con- nect signalling circuits. The base station 100 and the base station controller 102 form a base station subsystem (BSS) also comprising a transcoder, also known as a speech codec, or a TRAU (Transcoder and Rate Adapter Unit) 122. The transcoder 122 is generally placed as close as possible to a mobile services switching centre 132, as speech can then be transferred in cellular network form between the transcoder 122 and the base station controller 102, thus saving transmission capacity.

The transcoder 122 converts different digital coding forms of speech used between a public switched telephone network and a cellular net- work to suit one another, for example, from the 64 kbit/s fixed network form to another cellular network form (e. g. 13 kbit/s) and vice versa. The control unit 124 performs call control, mobility management, statistical data collection and signalling.

As Figure 1 shows the group switching field 120 can perform switching (indicated by black spots) to a public switched telephone network (PSTN) 134 through the mobile switching centre 132 and to a packet trans- mission network 142. A typical terminal 136 in the public switched telephone network 134 is an ordinary or an ISDN (Integrated Services Digital Network) phone.

A support node (SGSN = Serving GPRS Support Node) 140 estab- lishes the connection between the packet transmission network 142 and the group switching field 120. The aim of the support node 140 is to transfer pack- ets between the base station system and a gateway node (GGSN = Gateway GPRS Support Node) 144, and to keep record of the location of the subscriber terminal 150 within its area.

The gateway node 144 connects a public packet transmission net- work 146 and the packet transmission network 142. An Internet protocol or an X. 25 protocol can, for instance, be used at the interface. The gateway node 144 encapsulates the internal structure of the packet transmission network 142 from the public packet transmission network 146, so for the public packet transmission network 146 the packet transmission network 142 resembles a sub-network, the public packet transmission network 146 being able to ad- dress packets to the subscriber terminal 150 placed therein and to receive packets therefrom.

The packet transmission network 142 is typically a private network using an Internet protocol carrying signalling and tunnelled user data. The structure of the network 142 may vary operator-specifically concerning the ar- chitecture and protocols below the Internet protocol layer.

The public packet transmission network 146 may be, for example, a global Internet network, and a therewith communicating terminal 148, for ex- ample a server computer, wants to transfer packets to the subscriber terminal 150.

A laptop computer 152 is connected to the subscriber terminal 150.

The data to be transferred is carried from the laptop computer 152 to the server computer 148. Data can naturally be transferred in the opposite direc- tion too, from the server computer 148 to the laptop computer 152. Data is carried through the system at the air interface 170, from the antenna 112 to the transceiver 114 and from there multiplexed in the multiplexer 116 along the data link 160 to the group switching field 120, where a connection is estab- lished to the output of the support node 140. From the support node 140 data is applied along the packet transmission network 142 through the gateway node 144 and is connected to the server computer 148 connected to the pub- lic packet transmission network 146.

The invention is applicable to be used in basic GSM cellular net- works and in networks further developed therefrom, like GSM1800 and

GSM1900 systems. The invention is most preferably used in a 2+ phase packet transmission of the GSM system, i. e. packet transmission is conducted using GPRS (General Packet Radio Service), where packet transmission is carried out in packet-mode. Additional information on GPRS and the protocols used therein can be obtained, if needed, from ETSI (European Telecommuni- cations Standards Institute) GPRS specifications, such as ETSI GSM 03.60 and ETSI GSM 04.64.

When transferring packet-mode data to the subscriber terminal 150 the mobile telephone network 142 has to allocate a radio resource to the sub- scriber terminal 150. The radio resource allocated to the subscriber terminal 150 allows the subscriber to identify the data intended for himself/herself by means of a TFI identifier (Temporary Flow Identity) which is included in each data block sent over the radio path. Occasionally the network has to request acknowledgement of the transmitted data blocks from the subscriber terminal 150, for example a mobile phone, to ensure that data transmission to said subscriber terminal 150 is successfully completed over the radio path.

The radio interface resources are allocated to a particular sub- scriber terminal 150 only for the time that a temporary block flow (TBF) re- quires. Radio resources independent of one another are generally allocated to different subscriber terminals 150 so that data transmission to each subscriber terminal should be as fast and efficient as possible. However, several sub- scriber terminals 150 can, if desired, be simultaneously allocated to the same physical radio interface resource, or time slot. Then, different subscriber termi- nals 150 distinguish the data intended for themselves by applying said radio resource using the TFI identifier specifically allocated to each subscriber ter- minal 150.

In the invention subscriber terminals 150 allocated to the same ra- dio resource are served in turn. Of the GPRS subscribers 150 allocated to the same radio resource the subscriber terminal 150 to be served is switched to the following always when the mobile telephone network 100,102,132,140 requests acknowledgement of the data blocks sent to the previous subscriber terminal 150.

The subscriber terminals 150 are prioritized in a predetermined manner. Each subscriber terminal 150 is preferably provided with a specific service class, or what is known as a QoS class (QoS, Quality of Service). In this invention the base station system (BSS) offers the GPRS system sub-

scriber different quality of service, i. e. efficient data transmission, depending on the service class used by the mobile phone subscriber 150. The service time varies for subscriber terminals 150 of different service classes. By con- trolling the length of the acknowledgement sequence, i. e. the amount of data sent to each subscriber terminal 150 in one transmission, among various sub- scribers 150, the data transmissions of various service classes can be pro- vided with a desired amount of radio resources, or transmission time. The network 100,102,132,140 thus controls the quality of service, or speed and efficiency of the transmission.

When applications of different levels are simultaneously being car- ried out in the subscriber terminal, data transmission resources can also be application-specifically divided according to the principe of the invention.

The packet radio system and the method for controlling quality of service in a packet radio system are very good particularly when the base sta- tion system is in a loading state. The invention then ensures that each sub- scriber terminal 150 obtains at least some kind of service and that the data transmission delays caused by the loading situation are fairly divided among various subscriber terminals 150.

Even though the invention has been described above with refer- ence to the example of the accompanying drawing, it is obvious that the in- vention is not restricted thereto but can be modified in various ways within the scope of the inventive idea disclosed in the attached claims.