METHOD FOR. ALLOW A MOBILE STATION TO RECEIVE A CIRCUIT SWITCHING PAGE
FIELD OF THE INVENTION The present invention relates generally to signaling in a GSM communication system, and in particular, the present invention relates to a method for receiving paging messages from a circuit switched data domain while a mobile station is involved in the exchange of packet-switched data.
BACKGROUND OF THE INVENTION The General Packet Radio Service (GPRS) of the Global System for Mobile Communications (GSM) is intended to enable a service subscriber to have the ability to send and receive data in an end-to-end packet transfer mode. without using network resources in circuit-switched mode. GPRS allows the efficient use of radio and network resources when the data transmission characteristics are i) packet-based, ii) intermittent and non-periodic, iii) possibly frequent, with small data transfers, for example less than 500 octets, or iv) possibly
infrequent, with large data transfers, for example, more than several hundred kilobytes. User applications can include Internet browsers, email, etc. The GSM specifications of the Institute of
European Telecommunications Standards (ETSI) defines what is referred to as a "mobile station class" for GPRS mobile stations. The class of mobile station specifies part of the behavior to which the mobile station must conform with respect to its operation in packet mode, circuit-switched mode, or packet-switched and circuit mode. For example, a mobile station class is a Class A mobile station that supports simultaneous joining; monitoring, activation, invocation and flow of traffic in both packet-switched data services and circuit-switched voice. On the other hand, a Class B mobile station has been defined to support only simultaneous joining, monitoring and activation in both packet switching and circuit switched voice services, with invocation and possible traffic flow on a mutually exclusive basis . Finally, a Class C mobile station is defined to support only non-simultaneous binding, that is, mutually exclusive union, in
any of the voice services of circuit switching or packet-switched data. The mobile station classes can also be assigned, or changed, in some cases by the user, subject to limitations such as manufacturer options and equipment limitations. For example, a user application may have the ability to issue a command to change the mobile station class of the subscriber equipment currently in use. Currently, mobile station classes will therefore be treated as "effective classes", since users can exercise certain. control over the identity of the mobile station class. Efforts that are currently underway to further develop ETSI GPRS specifications to specify the required pipeline and signaling techniques that allow a mobile station, which has an individual receiver / transmitter, to handle a simultaneous GSM voice and packet session . This effort has led to the creation of a dual transfer mode (DTM) in which the voice of GSM and GPRS, or EDGE, can exchange data in the same radio frequency (RF). When the mobile station is operated in dual transfer mode, the operational context of the mobile station
contains a circuit switched voice connection active in dedicated mode, and an active packet switching time block (TBF) stream in the GPRS / EDGE packet transfer mode. Current GPRS networks include a process for coordinating paging transmission for circuit-switched data services and packet-switched data in which the GPRS network sends paging messages for the circuit-switched service in the same channel as it is used for packet switching services, that is, in a GPRS paging channel or in an associated packet control channel. As a result of being able to receive the paging services, the mobile station needs to monitor the associated packet control channel (PACCH) while the mobile station is currently engaged in packet-switched transfer, or in the GPRS paging channel when the The mobile station is not currently engaged in the transfer of packet-switched or circuit-switched data. As illustrated in FIGURE 1, a mobile station 100, such as a wireless telephone device, communicates with a circuit switching network 102 and a packet data network 104 at the
transmit signals and receive signals from a base station 106. The base station 106 is coupled to a base station controller 108, which in turn is coupled to a mobile switching center 110 via an interface 112 commonly referred to as an "A-interface", and the mobile switching center 110 at its it is interconnected with the circuit switching network 102. As a result, it is possible for the circuit switching data to be transmitted between the mobile station 100 and the circuit switching network 102 along a signal path including the base station 106, the base station controller 108, and the mobile switching center 110. Similarly, the base station controller 108 is coupled to a Service GPRS Support Node 114 (SGSN), which is aware of the location of the mobile station 100 and performs security functions and access control, and interconnects with the packet data network 104. As a result, it is possible for the packet-switched data to be transmitted between the mobile station 100 and the packet data network 104 along a signal path including the base station 106, the base station controller 108, and the SGSN 114. A GPRS network of the prior art allows
that a mobile station operating in a packet transfer mode receives a circuit-switched paging message when using an optional interface 116, commonly referred to as a "Gs interface", which connects to the mobile switching center 110 and the SGSN 114 The 116 Gs interface allows the mobile station 100 to receive a circuit-switched paging message while it is coupled in a packet-switched data transfer, by transmitting the circuit-switched paging information of the mobile switching center 110 directly. to the SGSN 114, along the Gs interface 116, instead of transmitting the paging message from the mobile switching center 110 through the base station controller 108 to the mobile station through a circuit switching paging channel in the combined control channel (CCCH). However, one of the problems associated with providing a Class A with capability for the mobile station operating in an environment that does not support the optional Gs interface 116, is that, while coupling in a packet-switched data transfer with wherein the packet data is being exchanged between the mobile station 100 and the packet data network 104, the mobile station 100 is unable to program the
receiving a circuit-switched paging block without attributing data reception from a packet data channel (PDCH), which may result in a loss of packet data production, since retransmissions may be required for blocks of lost data. In addition, differences in the organization of multiple-frame structures of the packet data channel, in which the packet-switched data are transmitted, and a combined control channel (CCCH), in which the concession channels are transmitted. paging and access (PAGCH), makes the programming of reception of a circuit switching paging block by the mobile station while it is problematic in a packet transfer of GPRS or EDGE. For example, as illustrated in FIGURE 2, the packet data control channel is organized as a multiple frame 100 having fifty-two frames 102 and twelve data blocks BO-Bll, in which each block BO-Bll of data is distributed over four time division multiple access (TDMA) frames. An "inactive" or "search" frame 106, located after every three blocks of data, allows the mobile station to perform the adjacent cell signal measurements, synchronization and verification and status of the cell.
synchronization in adjacent cells, measurements and interference, etc. Each block BO-Bll of data is made of four frames, each of which has a frame period f equal to 4.61538 milliseconds, and a period of block b which is equal to 18.4616 milliseconds, while each frame 106 inactive has a period of of inactive frame I that is equal to the frame period f, or 4.61538 milliseconds. The total period of a multiple frame structure 100 of the packet data channel is equal to 240 milliseconds. A combined control channel, on the other hand, is organized as a multiple frame 108 having fifty one frames 110, with the frame period f of each frame being equal to 4.61538 milliseconds. The multiple frame includes nine groups of four frames 1-9 including paging and access grant control channels, a contiguous four-frame block 114 which is a broadcast channel, and two inactive frames 116 positioned between each of a group of eight frames. The total structure period of the multiple frame 108 of the paging and access grant control channel is equal to 235,385 milliseconds. As can be seen in FIGURE 2, the structure of the multiple frame 100 for the packet data channel differs from the structure of the frame 108
multiple for the combined control channel, and as a result, the two channels are non-harmonically related so that the packet data control channel and the combined control channel slide in and out of the phase relative to each other as one time function. Since the only opportunity for a mobile station to read a circuit switching paging block may be during periods corresponding to the inactive frames 106 of the packet data control channel, it is difficult for the mobile station to schedule the reception of the blocks of circuit-switched paging, while the mobile station is coupled in a packet transfer of GPRS or EDGE. Further, since the total periods of the multiple frames 100 and 108 are unequal, a paging group to which an inactive frame refers at a point in time differs as time progresses, limiting the number of appropriate paging blocks visible to the mobile station in an inactive frame during a packet transfer. Accordingly, what is needed is a method for receiving and handling paging messages that originates from a circuit-switched domain while a mobile station is operating in a packet transfer mode.
BRIEF DESCRIPTION OF THE DRAWINGS The characteristics of the present invention that are believed to be novel are established with particularity in the appended claims. The invention, together with additional objects and advantages thereof can be better understood by reference to the following description, tonada together with the attached drawings, in the various figures of which similar reference numbers identify similar elements, and wherein: FIGURE 1 is a schematic diagram of a communication network in a GPRS system. FIGURE 2 is a schematic diagram of multiple frame structures for a packet data channel and a combined control channel. FIGURE 3 is a schematic diagram of a communication network, according to the present invention. FIGURE 4 is a signal flow diagram of a signaling path in a communication network according to the present invention. FIGURE 5 is a flow diagram of a mechanism for notifying a mobile station of a circuit switching paging message, in accordance with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED MODE The present invention is a method for a notification of a dual mode GPRS Class A mobile transfer station, operating in a packet transfer mode, of a circuit-switched paging message. Once notified of the circuit-switched paging message, the mobile station aborts a temporary block flow (TBF) in which the mobile station is currently exchanging packet data with packet-switched data, and returns to a control channel Combo (CCCH) having random access to establish the circuit-switched voice connection corresponding to the circuit-switched paging message. The combined control channel is a signaling channel that establishes a simultaneous voice channel and a data channel according to the requirements of double transfer mode. As a result, the mobile station is able to continue with the previously aborted packet data transfer and acquire a circuit switched voice session. As illustrated in FIGURE 3, a communication network 200 according to the present invention includes a mobile switching center 202 and a plurality of cell sites 204. Each cell site 204 includes a
base station 206 coupled to a base station controller 208. A protocol control unit 210 is coupled or contained within each base station controller 208, and each protocol unit 210 interconnects with a Service GPRS Support Node 212 (SGSN) which in turn interconnects with a network 214 of package data. The base station controller 208 is coupled to the mobile switching center 102 along a 215 A interface, and the mobile switching center 202 in turn interconnects with a circuit switching network 216. The SGSN 212 can also be connected to other SGSNs belonging to other service providers, which in turn can also be connected to other SGSN, etc. A mobile station 218, such as a wireless telephone device, is adapted to communicate the base stations associated with each base station controller 208 to maintain communications with another mobile station, the circuit switching network 216 or the network data network 214. packages. The mobile station 218 includes a transceiver 220 for receiving the signals from and transmitting the signals to the base station control 208, and a processor 222 for processing the signals sent and received from the base station controller 208. The SGSN 212 is aware of the location of the
station 218 mobile, and performs the functions of security and access control. It is understood that although only one mobile station 218 is shown in FIGURE 3, more than one mobile station is located within the communication network 200 at a time. FIGURE 4 is a signal flow diagram illustrating a signaling path and a communication network in accordance with the present invention. As illustrated in FIGURES 3 and 4, when the mobile station 218 is initially coupled in the packet data transfer, an existing packet data transfer, line 224 of FIGURE 4, occurs along a stream of data. temporary block (TBF) so that the mobile station 218 is coupled in a packet data exchange by the SGSN 212 in the packet transfer mode. When the circuit-switched information directed to the same mobile station 218 is received by the mobile switching center 202 from the circuit switching network 216, the mobile switching center 202 sends a circuit-switched paging message throughout from the interface 215 A to the base station controller 208, line 226, to inform the base station controller 208 of the circuit switching information, which includes the intended mobile station 218.
Based on the classmark of the intended mobile station 218, the base station controller 208 determines whether the mobile station 218 supports a dual transfer mode. In addition, the base station controller 208 also determines whether the mobile station 218 is currently in a temporary block flow. In accordance with the present invention, if the base station controller 208 determines that either the mobile station 218 does not support a dual transfer mode, or that the mobile station 218 is currently not in a temporary block flow, the switching message by circuits is sent to the mobile station 218 along the existing paging channel. However, according to the present invention, if the base station controller 208 determines that the mobile station 218 supports a dual transfer mode, and that the mobile station 218 is currently in a temporary block flow, the station controller 208 base sends a message to the protocol control unit 210, line 228, informing the protocol control unit 210 that a circuit switching page is on the waiting list for the identified mobile station 218, and instructing the unit 210 protocol control to send a circuit-switched paging message in a block
radio link control (RLC) control to a radio resource layer (RR) of the mobile station 218. The protocol control unit 210 then sends a radio link control / medium access control (RLC / MAC) block to the base station controller 208, and the base station controller 208 sends the RLC / MAC control block to the mobile station 218 by inserting the RLC / MAC control block into a block of the multiple frame structure of the frame 52 of the packet data channel, line 230. The inserted RLC / MAC control block indicates to the mobile station 218 that the "directed mobile station is now being paged by circuit switching". According to the present invention, for example, the RLC / MAC control block which notifies the mobile station 218 of the circuit switching paging message can be located in any of the blocks BO-Bll of the multiple frame 100 of the channel of packet data of FIGURE 2. Once the transceiver 222 of the mobile station 218 receives the RLC / MAC control block that notifies the mobile station that is being paged by circuit switching, the processor 220 of the station 218 The mobile processor processes the RLC / MAC control block and determines that the mobile station 218 is being paged with circuit switching. As a result,
the mobile station 218 aborts its current packet data transfer and begins to monitor a combined control channel with random access, i.e. the mobile station 218 is now in an idle mode, setting the circuit-switched voice exchange activity using known signaling sequences, line 232 of FIGURE 4. The combined control channel can also be used to exchange signaling information to be able to establish a simultaneous voice channel and data channel according to the double mode transfer requirements. This allows the mobile station 218 to continue with the previously aborted packet data transfer and acquire a circuit switched voice session. The user channel preferably includes a half-way traffic channel and a half-packet data channel (TCH / H + PDCH / H), or may optionally include a full traffic channel plus one or more data channels of contiguous packages (TCH / F + PDCH / F). With the term of the signal flow described in the above, corresponding to lines 226-232 of FIGURE 4, the data is now exchanged between the mobile switching center 202 and the mobile station 218 in the form of circuit-switched data , line 234, and between the SGSN 212 and the mobile station 218 in the form of
packet switching data, line 236, so that the mobile station 218 is now operating in a simultaneous voice and data session of user packets. FIGURE 5 is a flowchart of a mechanism in a communication network for notifying a mobile station of a circuit-switched paging message, in accordance with the present invention. As illustrated in FIGURE 5, after a circuit-switched paging message originating from a circuit-switched domain is received by a base station controller from a mobile switching center, Step 300, the controller of The base station determines whether the mobile station is capable of operating in a dual transfer mode, Step 310, using the mobile station classmark. If the base station controller determines that the mobile station is not capable of operating in double transfer mode, the circuit-switched paging message is sent to the mobile station in the paging channel (PGCH), Step 320. If the Base station controller determines that the mobile station is capable of operating in a dual transfer mode in Step 310, the base station controller then determines whether the mobile station is
currently engages in a packet-switched data exchange activity, Step 330. If the base station controller determines in Step 330 that the mobile station is not currently engaged in the packet-switched data exchange activity, the message circuit switching paging signal is sent to the mobile station in the paging channel (PGCH), Step 320. On the other hand, if the base station controller determines in Step 330 that the mobile station is currently engaged in the activity of exchanging packet-switched data, the base station controller informs the protocol control unit that the mobile station is being paged, and the protocol control unit sends the RLC / MAC control block to the mobile station within of a block of the multiple frame of the packet data channel, Step 340. With the reception of the RLC / MAC control block, the mobile station realizes that is being paged, aborts its current packet data transfer and begins to monitor a control channel combined with random access to establish the circuit switched voice connection, Step 350, which may include a user data channel with assignment for a voice channel and a data channel of
according to the requirements of double transfer mode. As a result of the signaling of the present invention, a simultaneous voice and data session is created by allowing the mobile station to continue with the aborted packet data transfer and acquire the circuit switched voice session. In this manner, the present invention provides a mechanism for receiving and handling a paging message originating from a circuit-switched domain while a mobile station is coupled in a packet-switched domain data exchange. While a particular embodiment of the present invention has been shown and described, modifications may be made. Therefore, it is intended that the appended claims cover all changes and modifications that fall within the real spirit and scope of the invention.