WO2002025974A1

WO2002025974A1 - Method and arrangement in a telecommunication system

Info

Publication number: WO2002025974A1
Application number: PCT/SE2001/002047
Authority: WO
Inventors: Rolf Hansson; Ulf Olsson; Konrad Feyerabend
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2000-09-22
Filing date: 2001-09-21
Publication date: 2002-03-28
Also published as: SE0003394D0; AU2001290446A1

Abstract

The present invention relates to cellular communication networks, in particular to methods to access packet-based wireless data services, which allow a mobile user equipment to receive various alternatives of packet paging messages and/or to apply various alternatives to access such services. The method according to the present invention performs the steps of receiving and identifying incoming packet paging messages, e.g. transmitted by applying a Short Message Service (SMS) or via the system paging channel, and selecting an appropriate access method to connect to a packet data service by means of interpreting a potential content in said paging message and/or determining from the cell broadcast channel whether a dedicated common packet data channel is supported in a cell of said cellular communication network to which the user equipment can establish a packet data connection.

Description

Method and Arrangement in a Telecommunication System

FIELD OF THE INVENTION

The present invention relates to interconnected datacommunication networks and cellular communication networks, in particular to various access methods for user equipments in the cellular network using packet-based wireless data services in the datacommunication network.

BACKGROUND OF THE INVENTION

Modern telecommunication systems, both wired and wireless systems, are intended to support a variety of different communication services, e.g. for voice communication or data communication. For voice communication, a fixed communication channel must exclusively be reserved on the air interface between the user equipment and its serving base station during the whole communication. Data communication, on the other hand, which normally occurs in bursts of data packets, can often be transmitted on a best- effort basis.

In a circuit-switched telecommunication system, which is in general not optimised for the transmission of such packet data, it would be a first alternative to transmit said packet data on a fixed air interface time slot having a fixed data rate as it is applied for voice communication. This approach implies on the one hand that the same traffic channels as for voice communication can also be used for data communication, which advantageously implies no or very limited hardware modifications in the base station. However, each user equipment must reserve a traffic channel for its packet data transmission and, due to the bursty nature of data traffic, there are frequent phases where no data is transmitted, which implies on the other hand an inefficient use of said reserved traffic channel.

Another alternative is described, e.g., in the standard document RCR STD-27H by The Association of Radio Industries and Businesses (ARIB) for the "Personal Digital Cellular Telecommunication System Radio Interface" as in use in Japan. In this alternative the air interface is more efficiently used because several user equipments share a common air interface channel for their data traffic, i.e. whoever wants to transmit data reserves the timeslot and transmits its data. This common channel is referred to as the User Packet Channel (UPCH) and announced to the user equipments by means of a Broadcast Channel (BCCH) that is supported by each cell of the cellular network. The Broadcast Channel contains network information, which includes inter alia optional fields for extension standard information indicating, e.g., whether a cell supports such a common User Packet Channel for packet data traffic. However, the support of such a User Packet Channel will imply additional hardware in the base stations and other network components of some systems or additional transceivers and transmission capacity for the additional packet data channels .

A communication connection can be mobile originated, i.e. initiated by the user equipment, e.g., for a data connection if the user wants to send data or establish an Internet connection, or can be mobile terminated, i.e. initiated by the network, e.g. for a data connection if a server in the network gets a trigger to push data to the user equipment, for instance for a news update or message delivering. However, for connections that are initiated by the network the location of the user equipment must at first be determined. This can be done, e.g., by help of a paging message that is broadcasted on a special Paging Channel (PCH) . When regarding the structure of the paging message as applied in the above mentioned standard RCR STD-27H a paging message can be specified depending on the type of the incoming call for the demanded user equipment. In case of incoming packet data, e.g., a packet paging message for packet data is sent. Each user equipment listens in the idle mode to at least one paging channel and can thus be informed on incoming calls by means of an identification of the user equipment that is sent along with the paging message. When the user equipment responds to said paging message the network will in its turn take the appropriate measures to establish a connection for the call or data that shall be forwarded to the user equipment.

SU-Y-MARY OF THE INVENTION

It has been observed to be a problem that a cellular communication network does not necessarily support the same kind of access to a service in all cells, e.g. for services basing on a packet data communication, while a mobile user equipment in said network only has one alternative to access such a service. It is a further problem that it is not possible to send additional information to a user equipment that shall connect to such a service.

Therefore, it is a first object of the present invention to achieve a method that makes a mobile user equipment more flexible to receive various alternatives of packet paging messages and/or to apply various alternatives to access services basing on a packet data communication.

This is advantageously solved by the teaching of claims 1 and 8.

It is a further object of the present invention to achieve an arrangement in a user equipment that can be applied for the methods according to claims 1-7 and/or 8. This is advantageously solved by the teaching of claim 9.

Briefly, these objects of the present invention are accomplished by a method in a user equipment in a circuit- switched communication network performing the steps of receiving and identifying incoming packet paging messages, e.g. transmitted by applying a Short Message Service (SMS) or the system paging channel, and selecting an appropriate access method to connect to a packet data service by means of interpreting a potential content in said paging message and/or determining from the cell broadcast channel whether a dedicated common packet data channel is supported in a cell of said cellular communication network to which the user equipment can establish a packet data connection.

It is a first advantage of the present invention that a user equipment is reachable for packet based services even in those cells of a circuit-switched communication network that do not support a dedicated common packet data channel .

It is another advantage of the present invention that a network operator of a circuit-switched communication network does not need to support a dedicated common packet data channel in all cells, e.g. due to a lack of space to install additional equipment or due to other hardware limitations.

It is thus another advantage of the present invention that a network operator can expand said network gradually from using traffic channels for packet data services to the usage of dedicated common packet data channels in accordance with the demand for such services.

Yet another advantage of the present invention is an increased flexibility to access mobile user equipments in a network within which not all cells support dedicated common packet data channels . It is still another advantage of the present invention that, within the same network or between networks, roaming of users of a packet data service is facilitated between cells that support dedicated common packet data channels and cells that do not support such channels.

Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings and claims .

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding, reference is made to the following drawings and preferred embodiments of the invention.

Figure 1 shows a part of an interconnected network structure in which the method and arrangement according to the present invention could be applied.

Figure 2 shows a comprehensive flowchart including the method steps according to the present invention.

Figure 2a shows a part of the flowchart according to figure 2 comprising a first alternative of sending a paging message.

Figure 2b shows a part of the flowchart according to figure 2 comprising a second alternative of sending a paging message.

Figure 2c shows a part of the flowchart according to figure 2 comprising the necessary method steps for packet data transmissio . Figure 3 shows functional units in a user equipment that are necessary in order to perform the method according to the present invention.

DETAILED DESCRIPTION

Figure 1 shows a part of an interconnected network structure within which the method and arrangement according to the present invention could be applied: A first communication network 10, which is in this example basically a cellular circuit-switched telecommunication network, could be composed, e.g., of cells 111 that are part of solely circuit-switched subnetworks 11 and of cells 121 of circuit- switched subnetworks 12 that also support packed data communication. These subnetworks 11,12 could represent, e.g., the networks of different operators within the same or neighboured geographical areas . Another possibility would be a circuit-switched network of a single operator that is in parts extended to a network comprising cells that also support packet data communication, e.g., a network under expansion or a network containing cells that does not justify the efforts and investments of such a network expansion. A plurality of user equipments 13 that are distributed in the various cells will apply for a range of services that must be offered by said first communication network 10.

Additionally, this first communication network provides connections 14 to a second communication network 15, which is a packet-based datacommunication network, e.g. the Internet, consisting of an interconnection of data servers and terminals 16. Access facilities are provided between this packed-based second communication network 15 and the part 12 of said first communication network 10 that is extended to support packet data communication. In addition to this, access facilities are also provided between said packed-based second communication network 15 and the circuit-switched part 11 of said first communication network 10. In the present example, this is done by using a so called Direct Access Server (DAS) 17, which functions as a modem to convert the packet data to signals that can be transmitted through the circuit-switched network and vice versa. Thus, there are two principally different access paths between the first and second communication network.

The method according to the present invention could be applied in such a network structure to make a user equipment 13 in said first communication network 10 reachable for packet data based communication services to or from a server 16 in said second communication network 15, irrespective of whether the cell in which the user equipment is presently located supports dedicated common packet data channels or not.

Figure 2 shows a flowchart that illustrates, with particular regard to paging mechanisms, how packet data can be transmitted from a server in said second communication network to a mobile user equipment that is located in a cell of said first communication network as described in figure 1. Figure 2 demonstrates by means of a comprehensive flowchart where the inventive method steps are incorporated in said data transmission. In particular refer figures 2a and 2b to the transmission of paging messages and figure 2c to the response on such paging messages.

Supposing a server in said second communication network intends to transmit data to a user equipment in said first communication network, block 21. In case of a mobile user equipment in a cellular network, it is in the first place necessary to determine the current location of this user equipment and to transmit an appropriate information message on which the user equipment will respond with an indication whether it is ready to receive data from the requesting server. These tasks can be initiated, e.g., by help of a so called push server in the second communication network that requests, e.g., to perform a paging of the user equipment in said first communication network, block 22. Normally the push server already has the necessary address information about the user equipment, e.g. from the server that intends to transmit data. This address information could be the network specific address of the first communication network, i.e. the telephone number or the International Mobile Subscriber Number (IMSN) , or could be a dedicated IP-address of said user equipment, which is convertible to a telephone number, e.g., by means of a data base which said push server can access. By means of this user address information the push server can apply already available mechanisms in the first communication network in order to page the user equipment, block 23. As explained later, it is one principal aspect of the present invention that said paging can be performed in several ways. Accordingly, the user equipment must be able to interpret various received information whether it specifies a paging message and perform appropriate method steps, block 24. These various paging alternatives for the user equipment will be explained in greater detail in figures 2a and 2b. In a next step, block 25, the user equipment must initiate appropriate measures for a paging response. It is another principal aspect of the present invention that also said paging response and, successively, the packet data transmission can be performed in several ways. The various response alternatives for the user equipment will be explained in greater detail in figure 2c. The paging response is transmitted to the server in the second communication network that originally has started the paging request, block 26, whereupon this server can start its data transmission, block 27.

Figures 2a and 2b show two alternatives for transmitting a paging message. A user equipment as described in the state of the art is supposed to know only one kind of paging. However, in some cases it may be advantageous to provide several alternatives for transmission of paging information. In the first alternative, as shown in figure 2a, the user equipment in the first communication network is located and informed by means of a standard paging message, which is broadcasted via the standard paging channel (PCH) in each cell, block 231. A user equipment in the idle mode always listens to this paging channel, block 241, and must take appropriate measures to establish a communication connection on reception of a paging message containing its own identification, block 241Yes. In case of a packet data communication, as in this example, the user equipment will receive a "packet paging message" as defined in, e.g., the standard document RCR STD-27H.

When locating the user equipment by help of such a packet paging message it is not possible to send any further information on the paging channel together with said paging information although this might be advantageous in some cases. Therefore, figure 2b shows a conceivable modification of the method according to the present invention whereby the packet paging message is transmitted by means of a Short Message (SMS) . The server in the second communication network that has initiated the paging procedure knows or can retrieve the user address information of the user equipment in the first communication network. Therefore, it must only send such a Short Message to the SMS-server in said network which will then forward the Short Message by means of known mechanisms in said network, block 232. A user equipment must be able to receive Short Messages and to detect whether a Short Message must be interpreted as a paging message, block 242. In a next step the user equipment must evaluate the content of said message, block 243. This will be described later on in greater detail . The decision about which paging alternative should be used can depend on several criterions: It is on the one hand efficient and fast to apply the already available paging channel (PCH) for retrieving the location of a user equipment because signalling via said paging channel will not essentially increase the total system load. On the other hand, it is not possible to send any additional information along with the paging message as it is possible when applying a Short Message. However, this alternative will cause an increase of the system load.

According to the state of the art it is presumed that a user equipment receives paging messages from its serving network in one well-determined way. It is likewise presumed that the paged user equipment replies on this paging in a well- determined way. However, this solution has been observed to be disadvantageous in certain situations: Supposing a user equipment has received an indication for reception of packet data and is intended to use, e.g., a common User Packet Channel (UPCH) for packet data transmissions as described above. If the user equipment is currently in a cell that does not support such a common User Packet Channel it might not be able to connect to this channel when it receives the packet paging message from the network. Correspondingly, a user equipment that only can perform data transmission via a circuit-switched traffic channel will reduce the efficiency of the network even in those cells that support a common User Packet Channel. Therefore, the user equipment must have the capability to perform a packet data communication according to several alternatives. This implies additional method steps which constitute a part of the method of the present invention and which are now explained with reference to figure 2c.

A user equipment, which is located in a cell of the first communication network, can retrieve various cell information by means of the Broadcast Information Channel (BCCH) , inter alia, whether a dedicated common packet data channel is supported in this cell and, if implemented, information about the timeslot and frequency that is used for this common User Packet Channel (UPCH) that is applied for said packet data traffic. Thus, the user equipment must at first evaluate this information and determine whether the cell within which it is currently located, or another cell to which it can establish a connection, supports said common User Packet Channel (UPCH) or not, i.e. whether or not such information is presented on the broadcast channel, block 251. The user equipment must also evaluate possible information that has been sent along with the paging message, e.g. when applying a Short Message for paging, block 252.

Then, in a next step, block 253, the user equipment decides by help of this information which of several possible access methods it must or can apply to connect to the packet data service: If the cell does not support said User Packet Channel, block 253No, the user equipment must establish a connection to the datacommunication network, e.g., via a Direct Access Server (DAS), block 255. The user equipment then sends its data via a traffic channel that normally is dedicated to voice communication in the circuit-switched network, block 262. For this purpose, the user equipment must know the dialling number of at least one Direct Access Server. Then, a connection can be established via said server between a user equipment in the circuit-switched part of the first communication network and the server in the second datacommunication network. The originating server can start to forward its data to the user equipment via said Direct Access Server by using the IP-address of the user equipment. However, if said cell supports the common User Packet Channel, block 253Yes, the user equipment can connect to this channel, block 254Yes. It is one possibility that the user equipment knows the IP-address of the originating server and can inform this server that it is ready to receive the packet data. In another possibility the user equipment will inform the push server that it is ready to receive data and the push server in its turn will inform the originating server about this along with the IP-address of the user equipment. However, even if a common User Packet Channel is supported the user equipment still has a choice to connect either to this channel, block 254Yes, or to establish nevertheless a connection via a traffic channel and using a Direct Access Server, block 254No, e.g. due to received broadcast or paging information.

Correspondingly, the method and arrangement according to the present invention can also be applied in case of a packet data communication that is initiated by the user equipment. Also in this case the user equipment must at first retrieve the necessary information from the broadcast channel whether the cell within which it is currently located supports a dedicated common packet data channel or not and decide by help of this information whether it can access a server in a datacommunication network either directly via the common User Packet Channel or via a traffic channel and a Direct Access Server.

As already mentioned above, it is a conceivable modification of the method according to the present invention to apply a Short Message in order to page a user equipment. This is advantageous because it allows to send additional information along with the paging message. A Short Message has a fixed format comprising essentially a header field and a user data field having a fixed length. Short Messages that are applied for paging purposes must contain an appropriate identifier in their header field. The paging information could contain, e.g., additional dialling information that specifies how a paged user equipment in a cell that only supports circuit-switched connections shall contact a Direct Access Server. Normally, it can be presumed that the user equipment has stored at least one dialling number of a Direct Access Server. However, as there are a plurality of such servers it could sometimes be advantageous, e.g., to make the user equipment contacting the datacommunication network via a specific server or to transmit the dialling number of an alternative server if the ordinary Direct Access Server is temporarily not available. Another option could be to send the IP-address either of the push server or the originating server along with the Short Message. It could also be advantageous to send other information along with the paging information: The Short Message may contain additional information that specifies the type of packet data that is to be delivered to the user equipment . Such information could relate, e.g., to user-defined settings about which kind of messages shall be forwarded or suppressed. It is in particular possible to indicate a message priority by means of said Short Message. Said additional information could also be used to indicate in which way the user equipment shall establish a connection. This might be advantageous when a user equipment that has received a paging message from a server in a datacommunication network, e.g. via the Internet, shall establish a connection to this server via a second datacommunication network, e.g. a company-owned Intranet. This option allows also that the paging of the user equipment is initiated by a first server while the user equipment shall establish a connection to a second server.

Figure 3 shows an arrangement 30 in a user equipment containing the necessary means 31-37 to perform the method according to the present invention. The method steps as presented in figures 2 and 2a-2c are preferably performed by means of software modules that can be incorporated in a processor of said user equipment. With regard to the paging mechanism, the arrangement 30 must comprise receiver means 31,33 to receive and interpret various types of paging messages: When applying a Short Message Service (SMS) for paging of a user equipment there must be facilities 31 to detect such a paging message and facilities 32 to interpret the content of the Short Message. Otherwise, a paging message that is transmitted via the paging channel (PCH) can- be detected by a paging channel receiver 33 that constantly listens to said paging channel. With regard to packet data transmission, the arrangement 30 must comprise means 34 for making an appropriate decision which of possibly incorporated access methods should be and can be used. The arrangement 30 must also comprise means 36,37 to send packet data by using one of said access methods, e.g. via a dedicated common User Packet channel (UPCH) or via a traffic channel that normally is dedicated for voice traffic . Therefore, the paging information, which can have been received in several ways, is forwarded to a central decision unit 34. This unit 34 makes a decision about which access method shall be used depending on possible information that is sent along with the paging information and information that is retrieved from a unit 35 that evaluates the information on the Broadcast Channel (BCCH) . This decision is forwarded to the respective module 36,37 that is responsible for sending packet data according to a certain access method, e.g., by responding via the common User Packet Channel (UPCH) by help of a module 36 or by applying a voice channel for data transmission by help of a module 37.

Claims

1. Method in a user equipment (13) to perform a mobile terminated packet data service from a server (16) in a packet data network (15) to said user equipment (13) in a cellular circuit-switched communication network (10) , which provides in at least a number of cells (121) also the facilities of a packet data network,

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receiving and identifying (24) an incoming message as a paging message that indicates to connect to a packet data service,

initiating (25) a paging response in order to connect to said packet data service by selecting an appropriate access method, inter alia on grounds of potentially received paging information.

2. Method according to claim 1, comprising the step of

receiving (241) a standard paging message on the standard paging channel .

3. Method according to claim 1, comprising the step of

receiving (242) a paging message that has been sent by applying a Short Message Service (SMS) .

4. Method according to claim 3, comprising the step of

determining (243) whether the received Short Message contains at least one dialling number of a Direct Access

Server that can be used to connect to the packet data network .

5. Method according to one of claims 3 or 4, comprising the step of

determining (243) whether the received Short Message contains the IP-address of a destination server in the packet data network.

6. Method according to one of claims 3-5, comprising the step of

determining (243) whether the received Short Message contains information regarding the type of the data packet message that is to be delivered.

7. Method according to one of claims 1-6, comprising the step of

selecting (254) an appropriate access method to connect to a packet data service by means of interpreting (252) the content of a paging Short Message and/or determining (251) from the cell broadcast channel whether a common packet data channel is supported in a cell of said cellular communication network (10) to which the user equipment (13) can establish a connection.

8. Method in a user equipment (13) to perform a mobile originated packet data service from in a cellular circuit- switched communication network (10) , which provides in at least a number of cells (121) also the facilities of a packet data network,

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selecting (254) an appropriate access method to connect to a packet data service by means of determining (251) from the cell broadcast channel whether a common packet data channel is supported in a cell of said cellular communication network (10) to which the user equipment (13) can establish a connection.

9. Arrangement (30) for providing mobile-terminated and mobile-originated packet data services in a user equipment

(13) in a cellular circuit-switched communication network (10) , which provides in at least a number of cells (121) also facilities for a packet data network,

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units (31,33) that enable to identify an incoming message as a paging message,

a unit (32) that enables to interpret potential information in a received paging message,

a unit (35) that enables to interpret information from a cell broadcast channel,

a unit (34) that enables to determine from said received information whether a common packet data channel is supported in a cell of said cellular communication network (10) to which the user equipment (13) can establish a connection, and that enables to select an appropriate access method to said packet data service on grounds of the received information,

units (36,37) that enable an access to said packet data service.

10. Arrangement according to claim 9, comprising means for storing address information that is necessary in order to establish a connection to a packet data network (15) .

11. Computer program product loadable on a memory in a user equipment

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that it is capable of performing the methods according to one of claims 1-7 or 8.