WO2008088245A1

WO2008088245A1 - Soft inter-network handover using time scheduling

Info

Publication number: WO2008088245A1
Application number: PCT/SE2007/000358
Authority: WO
Inventors: Andreas Olsson; Erik Westerberg; Lars Boncz
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2007-01-15
Filing date: 2007-04-17
Publication date: 2008-07-24
Also published as: AR064914A1; WO2008088243A1

Abstract

When a communication path, between a mobile station (1) and a first telecommunication network (A) is to be used in parallel with an additional communication path between the mobile station and a second telecommunication network (B), a toggling procedure or dual scheduling mode is used. In this procedure the mobile station continues, during a communication adaptation period or dual scheduling period, to communicate using the communication path with the first network and in time intervals between periods in which the communication with the first network is scheduled it performs signaling and/or data transfer with the second network. The signaling and/or data transfer can e.g. be used to allow presence signaling or mobile TV interactivity. It can also be used to set up a communication path with the second network. After having set up the communication path with the second network the mobile station can instead use this communication path. This method may give a minimum interruption in the voice service at handover from the first network to the second network.

Description

SOFT INTER-NETWORK HANDOVER USING TIME SCHEDULING

RELATED APPLICATION

This application claims priority and benefit from International patent application. No. PCT/SE2007/000029, filed January 15, 2007, the entire teachings of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention is generally related to using radio resources for special purposes when a mobile station is capable of concurrently communicating through at least two different radio technologies, in particular for a mobile station having single radio circuitry for the radio communication. Such special purposes for which at least two communication services are used in parallel in first and second networks may include signaling and/or data transfer for e.g. allowing a mobile station currently communicating in the first network to gain information about the radio quality and the load situation for a neighboring cell in the second network and for allowing presence signaling or mobile TV interactivity. In particular the invention is related to a method and apparatus for changing a communication path between a mobile station and a first network to a different communication path between the mobile station and a second network or generally for establishing an alternative communication path between the mobile station and a second network.

BACKGROUND Today there exists a multitude of different radio access technologies by which a mobile station can communicate with a corresponding data network, servers, the Internet, other mobile stations and more. Examples of such radio access technologies are GSM, WCDMA, HSPA, cdma, LTE, WiMAX, satellite radio links and WiFi. In many situations the radio coverage of more than one radio access technology overlaps which means that the mobile station in principle can communicate with or through more than one radio system. One example of such overlapping coverage includes many of the combined WCDMA and GSM radio networks that are being deployed world wide. Another example is a local WiFi network set up in an area also covered by a GSM network. In addition to these examples there are several other scenarios with overlapping radio network coverage. Overlapping coverage from more than one radio access technology is also becoming more and more common as new radio technologies are deployed in parallel to legacy radio networks being expanded.

The overlapping coverage could for example, as have been discussed for some time, possibly be used for load sharing between radio technologies. E.g. if a WCDMA network goes towards congestion, it can be offloaded with traffic by re-directing it to a GSM network. However, the load sharing requires information about the traffic load in the other network. Such information can e.g. be obtained by core network signaling between RRMs₅ see Fig. 15, but may generally be incomplete, i.e. it does not give a full picture of the traffic situation. The missing information can e.g. include unknown quality of the radio link for a mobile at a certain position in the radio cell in the other network. Hence, in many situations of overlapping coverage it may be advantageous if the mobile station can communicate with two different radio networks simultaneously. One specific application of such parallel communication in two radio systems would then include the case where a mobile station that is communicating via a GSM system and is using the corresponding radio communication channel for receiving e-mail messages and on initiative from either the mobile station or the GSM system probes a second network for radio quality and load situation in a WiMAX system and reports the situation of the second network back to the first network.

Another example where parallel radio communication in two overlapping radio systems is necessary is when a service A is available in network A only, another service B is available in network B only and the mobile station needs to run both services in parallel. This could be e.g. a positioning service available in a WCDMA network only in parallel to a TV service available in an overlapping WiFi network or e.g. Interactivity signaling and/or data transfer in an LTE network in parallel with a mobile TV session in a DVB-H network.

Yet another application of parallel communication in two radio systems is a mobile station that is communicating via a WiFi system and is using the corresponding radio communication channel for a voice service. Li a situation where the mobile station starts to move out of coverage of the WiFi radio network it can be necessary to transfer the voice service to an overlapping GSM network. In order to transfer the voice service to the GSM network without interrupting the ongoing voice service the mobile station needs to set up a voice communication channel in the GSM network in parallel to receiving and transmitting data packets containing voice frames over the WiFi radio channel.

Another example is in the future radio system called LTE (Long Term Evolution) for which standardization work is ongoing in 3GPP. Networks according to the LTE standard will be packet switched only networks, i.e. no circuit switched traffic will be supported in such networks. Another example of radio access networks that go towards packet switched only traffic are networks according to WiMAX (Worldwide Interoperability for Microwave Access, a wireless industry coalition). Hence communication of speech will be carried out by VoIP in such networks. In a multi network scenario it is important to have at least one network that can provide coverage, since else the end-user can be without service. It is also important to provide a smooth transition for services between the different network for good end-user perceived service quality. E.g. in the case where an LTE network fails to provide coverage it will be important that e.g. a GSM (Global System for Mobile communication) network can provide a continuation of a speech call started in LTE and that the interruption during a move from an LTE network to the GSM network is minimal.

This complexity is not a problem that is new for moves between an LTE network and a GSM network. It has been observed in WiFi (Wireless Fidelity) discussions as well. The problem is to keep the service outage short so that the end-user does not perceive a quality degradation during the move. A prior art solution to the problem has been to introduce dual radio units ("dual radio"), i.e. radio circuitry specially adapted to communication with a WiFi network is installed in the mobile station in addition to parallel radio circuitry specially adapted for communication with a network of another kind, using e.g. a different wavelength band. The dual radio solution is not a recommendation for LTE-GSM co-existence due to the increased cost of the mobile stations.

To introduce a "normal" packet switched LTE handover to a circuit switched GSM network requires signaling and/or data transfer between the respective MSC (Mobile Switching Center) of the GSM network and the MME/UPE (Mobility Management Entity/User Plane Entity) in the LTE system, see Fig. 1. The GSM network further includes a BTS (Base Transceiver Station), i.e. base station, and a BSC (Base Station Controller), the interface between these devices called Abis and the interface between the MSC and the BSC called A. The LTE network includes a base station called eNode B and Sl is that standardized name of the interface between the eNode B and the MME/UPE. Here, a mobile station 1 (MS), also called a mobile terminal, simply a terminal, a mobile unit, a mobile device etc. and e.g. being a cellular telephone or mobile telephone, communicates through the node 3, i.e. the base station eNode B, in an LTE network and is going to use instead a 2G network and will then communicate through a base station 5 thereof. The necessary signaling and/or data transfer required to make this happen is indicated by the dashed circle 7. However, such signaling is not desirable in LTE networks due to the fact that the age of the protocols supported by the MSC of the 2G network would give a large cost for adapting the core network, not shown.

For the terminal 1 to make a hard break from an LTE network and perform a terminal initiated call re-establishment would at least take 1 s, which is well above the requirement of the time period of 300 ms stated in the document 3GPP TS 22.278 vl.0.0. SUMMARY

It is an object of the invention to provide an efficient method of allowing signaling between or generally data transfer between a mobile station, that is currently communicating in and/or through a first network, and another, second network. It is another object of the invention to provide an efficient method of replacing a communication path between a mobile station and a first telecommunication network with a communication path between the mobile station and a second telecommunication network.

It is another object of the invention to provide a mobile station adapted to allow signaling or data transfer between the mobile station, when it is in communication with and/or in a first telecommunication network, and a second telecommunication network.

It is another object of the invention to provide a mobile station adapted to efficiently replace a communication path between a mobile station and a first telecommunication network with a communication path between the mobile station and a second telecommunication network.

It is another object of the invention to provide a base station that is connected in a first telecommunication network and is adapted to allow signaling or data transfer between a mobile station, when it is communicating with and/or through the base station, and a second telecommunication network.

Generally thus, a method and apparatus are provided for establishing and at least for some time period maintaining communication between a mobile station and two different radio systems such as for the purpose of using several communication services in parallel or for changing a communication path between the mobile station and a first of the radio systems to a different communication path between the mobile station and a second of the two radio systems.

A time mapped scheduling for receiving from/communicating with two different systems or networks can be used. Then, the mobile station operates in two radio access technologies in a repeated, alternating manner, for some time period. In this time the mobile station toggles between the two systems in some suitable way and a scheduling map may be used for timing in the toggling procedure. Hence, during this time period the mobile station in communicating with a second telecommunication network while never releasing the communication path with the first telecommunication network. An aspect of the scheduling is that time gaps in a communication path between a mobile station and a first network are created in order to allow the mobile station to communicate with a second network.

The method can generally allow signaling and/or data transfer between a mobile station and a second telecommunication network when the mobile station already is communicating with a first telecommunication network over a first communication path between the mobile station and the first telecommunication network. Then the mobile station continues to communicate using the first communication path with the first network and in the free time intervals between periods in which the communication with the first network is scheduled or is performed, the mobile station can perform signaling with the second network or generally allow communication of data to and from the second network to e.g. set up a second communication path with the second network. The method can e.g. be used in a case where a serving base station orders a mobile station to probe, i.e. to gain information about, the radio quality and the load situation for a neighboring cell.

The method can also be used for replacing a first communication path between a mobile station and a first telecommunication network with a second communication path between the mobile station and a second telecommunication network, i.e. moving or changing a communication path over which voice and/or other end user data are transmitted. The second network may be of a kind different from that of the first network, such as using a different radio access technology, e.g. using a different standard. During a transitional period the mobile station can then continue to communicate using the first communication path with the first network and in time intervals between periods in which the communication with the first network is scheduled it can perform the signaling with and/or the communication of data to and from the second network that is necessary to set up a communication path with the second network. After having set up the communication path together with and through the second network the mobile station can continue or proceed to use only this communication path for transmitting the voice or other end user data.

The first network may be arranged to send, to the mobile station and before the transitional period, information on times, when said signaling with and/or communication of data to and from the second network is allowed. Such information can include a scheduling map or other information from which a suitable scheduling map can be derived. The time intervals for scheduling the communication between the two networks and the mobile station, i.e. the scheduling, may be determined in accordance with the timing or frame structures of the two networks and in some cases only the timing or frame structure of the second network has to be considered. The information on the times when the signaling with and/or said communication of data to and from the second network is to take place can in some cases be sent from the mobile station to the second network and before the transitional period.

In the case where the second network is a GSM network, the mobile station cannot, according to prior art, know exactly when in time the response to a request might come. It must be ensured that the that the mobile station receives the response to the request, i.e. an Immediate Assignment Command, from the GSM network even though the mobile station might have to leave the GSM network to communicate with the first network, due to the scheduling map, before the Immediate Assignment Command have been received. In order to ensure this, an Immediate Assignment Command or similar information may be sent from the GSM network in multitude over time resulting in that the mobile station receives an Immediate Assignment Command when returning from the first network to listen the GSM system. An alternative method to ensure that the mobile station receives an Immediate Assignment Command includes that the GSM network sends the Immediate Assignment Command or some similar information at a fixed time or in a predetermined frame after the request for a resource has been received by the GSM network, in the case where the time period it is known when the mobile station has again returned to the GSM network. Similar procedures can be used in a general case when the mobile station, for setting up some communication channel with the second network, has to receive initial information or data before the dual scheduling can start, i.e. the mobile station can in some request message also include details of how the response should be sent, such as that a predetermined number of tries should be made or that the response should be sent at some specified time.

The mobile station may in some case send information about the timing of the frame structure of the second network to the first network.

A mobile station for executing the method must be capable of communicating through both the first and second networks, in particular by using the same radio circuits or the same radio transceiver and hence it may include a unit or a set of units for handling communication with the first system and another unit or another set of units for handling communication with the second system. The mobile station suitably includes a dual scheduling unit that is e.g. adapted to command, when a communication path between the mobile station and the first telecommunication network is to be replaced with a communication path between the mobile station and the second telecommunication network or generally when some signaling with and/or communication of some data to and from the second network is desired: - that first respective circuits/units of the mobile station are to continue, during some period, to communicate using the communication path with the first network, and

- that second respective circuits/units of the mobile station are to perform, in time intervals between periods in which the communication with the first network is scheduled, signaling with and/or communication of data to and from the second network to e.g. set up a communication path with the second network.

After the second respective circuits/units have set up the communication path with the second network, the first respective circuits/units can suitably stop communicating through the first network, and the second respective circuits/units are now used for communication over the now set-up communication path with the second network. A base station for the first telecommunication network may also include a dual scheduling unit. The base station is then suitable adapted to be in communication, when a mobile station for which a communication path is already established through the base station and the first telecommunication network requires some signaling with or generally communication of some data to and from a second, different telecommunication network, only during periods set according to a scheduling map. Such a scheduling map may incur that the time periods during which the base station is in communication over said communication with the mobile station occur more seldom than before or more seldom than during ordinary operation. This may allow the mobile station to communicate in the intervals between the time periods with the second network. The method as described herein may generally be performed in a system including a terminal, typically a mobile station, a first telecommunication network and a second telecommunication network, the latter typically being cellular networks but also other networks can be considered in which communication is performed in predetermined time periods such as time slots and in which the terminal may not be mobile. The method allows signaling and/or data transfer between the mobile station and the second telecommunication network when the mobile station is already communicating with or through the first telecommunication network, using a communication path between the mobile station and the first telecommunication network. In the method the mobile station continues to communicate using the communication path with the first network, and the signaling and/or transfer is performed during a dual scheduling time period and in time intervals between periods in which the communication with the first network is scheduled or is performed. The second network may e.g. be of a kind different from that of the first network, such as using a different radio access technology. The communication path may e.g. be adapted to communicate speech or end user data. During the dual scheduling time period when the mobile station and the second network perform the signaling and/or transfer of data, the time intervals during which the communication between the mobile station and the first network is scheduled or is performed can appear according to a dual scheduling pattern. This pattern can be adapted so that these time intervals appear more seldom than in the case where the mobile station is only communicating with the first network.

Information can be sent, from the first network to the mobile station and before said dual scheduling time period, on times when the signaling and/or data transfer between the mobile station and the second network is allowed. The time intervals for scheduling communication between the two networks and the mobile station can be adapted in accordance with the frame structures of the two networks, in particular in accordance with the frame structure of the second network. Information on times when the signaling and/or data transfer between the mobile station and the second network is to take place can be sent from the mobile station to the second network and before the dual scheduling time period.

Information about the timing of the frame structure of the second network can be sent from the mobile station to the first network to allow the first network to adapt the scheduling of communication with the mobile station accordingly. In the signaling and/or data transfer between the mobile station and the second network, information may e.g. be acquired that is necessary for setting up a communication path from the mobile station through the second network. This information can be used for establishing such a communication path and thereafter this new communication path can be used. In this case the communication with the first network can be terminated so that after the dual scheduling period the mobile station only communicates with and through the second network.

In the signaling and/or data transfer presence signaling between the mobile station and the second network may be performed. Alternatively, instead probing for radio resources and radio quality or mobile TV interactivity signaling in the second network may be performed. A mobile station for performing the method as described herein may generally include a dual scheduling unit that is adapted to command, during a dual scheduling time period a set of first circuits or units of the mobile station to continue to communicate using the communication path with the first network according to a scheduling pattern, and a set of second circuits or units station to perform, in time intervals between periods in which the communication with the first network is scheduled, communication such as signaling and/or data transfer with the second network.

A base station for performing the method as described herein and for connection in a first telecommunication network may generally also include a dual scheduling unit. This unit should then be adapted to control the base station to be in communication, when a mobile station for which a communication path is already established through the base station and the first telecommunication network requires communication such as signaling and/or data transfer with a second, different telecommunication network, only during periods set according to a scheduling map, also called scheduling pattern. The dual scheduling unit may be arranged to perform the control so that the time periods during which the base station is in communication with the mobile station occur more seldom than before. This allows the mobile station to communicate, in the intervals between said time periods, with the second network. The communicating with the second network can be required e.g. in the case where the base station and/or the first network requires information from or about the second network or the already established communication path is to be replaced with a communication path between the mobile station and the second telecommunication network. hi a special case the method as described herein may also be seen as a method of adapting a communication link, in particular the characteristics of the communication link such as the time scheduling of the actual transmission of information in the link, between a mobile station and a first telecommunication network to allow establishment of a communication path between the mobile station and a second telecommunication network. During a communication adaptation period the mobile station continues to communicate using the communication path with the first network and in time intervals between periods in which the communication with the first network is scheduled performs signaling and/or data transfer with the second network to set up a communication path with the second network. Such a method can allow that the communication path with the second network is established and used without the need for releasing the communication path with the first network.

Using the method as described herein e.g. a short interruption may be achieved when moving to a new communication path.

Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the methods, processes, instrumentalities and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS While the novel features of the invention are set forth with particularly in the appended claims, a complete understanding of the invention, both as to organization and content, and of the above and other features thereof may be gained from and the invention will be better appreciated from a consideration of the following detailed description of non-limiting embodiments presented hereinbelow with reference to the accompanying drawings, in which: - Fig, 1 is a schematic illustrating a mobile station that is communicating in an LTE network but will start instead communicating in a 2G network,

- Fig, 2 is a schematic of the general layout of a mobile station that is communicating in an LTE network and uses a dual scheduling method for starting communicating in a 2G network,

- Fig. 3 is a schematic of combined general system including two networks and a mobile station, in which a dual scheduling method is used for changing a communication path between the mobile station and one of the networks to instead extend between the mobile station and the other of the networks,

- Fig. 4 is a schematic of the timing for communication between an MS and a BS on an SDCCH (Stand Alone Dedicated Control Channel) in a GSM network at e.g. a call set-up on the SDCCH, - Fig. 5 is a timing diagram when changing a communication path from a mobile station to a first network to a communication path from a mobile station to a second, different network,

- Fig. 6 is a flow diagram of steps taken in the mobile station in a method in which a radio node in a first system initiates a dual scheduling mode,

- Fig. 7 is a flow diagram of steps taken in a radio node in a first system using the same method as in Fig. 6, - Fig. 8 is a flow diagram of steps taken in a radio node in a second system in a method in which a mobile terminal communicates the structure of a dual scheduling map to the second system,

- Fig. 9 is a timing diagram similar to Fig. 5 when changing communication for voice through an LTE network to instead pass a GSM network, - Fig. 10 is a block diagram of a mobile station showing some components that may be used in a dual scheduling procedure,

- Fig. 11 is a block diagram of a base station showing some components that may be used in a dual scheduling procedure,

- Fig. 12 is a timing diagram similar to Fig 5 for a procedure in which a mobile station executes activities in a second network (WiMAX) in parallel to an ongoing service communicated in a first network (LTE),

- Fig. 13 is a timing diagram similar to Fig 5 for a case where a mobile station MS indicates to a GSM system that a toggle mode and multiple resource assignment messages are to be used,

- Fig. 14 is a timing diagram similar to Fig 5 for a procedure in which a mobile station executes probing for radio resources and radio quality in a second network (WiMAX) in parallel to an ongoing service communicated in a first network (GSM),

- Fig. 15 is a schematic of an example of two neighboring radio systems that use inter RRM signaling for handover due to load sharing,

- Fig. 16 is a schematic similar to Fig. 15 of two neighboring systems having no interface between their RRM functionalities, still allowing signaling for a handover operation,

- Fig. 17 is a flow diagram of substeps taken in the mobile station in a method in which the mobile station informs a radio node in a second system about a scheduling map, and

- Fig. 18 is a flow diagram of steps taken in a general system when a scheduling pattern is negotiated for. DETAILED DESCRIPTION

Methods and apparatus allowing simultaneous use of two radio paths for a mobile station will now be described. In the general case a mobile station 1 is wirelessly communicating through a base station BS_A in a first network A, for instance in an ongoing session for a telephone call, see Fig. 3. For some reason the mobile station may want some signaling with or wants to acquire data from or about a second network B and/or transfer data to the second network B, in particular to or through a base station BS_B thereof. The two networks can include switching centers SCA, SCg, respectively, that may correspond to an MSC, BSC or node B in e.g. a GSM network or an MME/UPE in an LTE network. Then, during a period of time a method or process of time mapped scheduling is used for receiving from or generally communicating simultaneously in the two networks, also called systems or radio systems and being e.g. mobile telephony networks, also called cellular networks, mobile access networks or radio access networks. During this period the mobile station 1 operates in two radio access technologies at the same time and toggles between them. After the data has been transferred or acquired the time mapped scheduling can be terminated. During in the time mapped scheduling the mobile station 1 can be said to have entered a scheduled dual mode or dual scheduling mode, this allowing a minimum interference with the ongoing communication session in the first network. The scheduling during said time period which may be a rather limited time period can be made so that packets or frames are received only during predefined intervals in one system, this leaving the remaining time for the mobile station to interact with the other system. In a particular case, the time mapped scheduling method can be used for transferring an ongoing communication session, such as telephone call, for the mobile station 1, that is currently communicating through the base station BSA in the first network A, to the second network B, in particular to instead communicate through the base station BSβ. During the time period for dual scheduling that in this case can be called a transition period the time mapped scheduling method is used for sending and/or receiving data, that can be required for the transfer of the communication session. As already described, the mobile station 1 during this period operates according to two different access procedures at the same time and switches or alternates between them in a suitable, e.g. predetermined, manner. After the switching center SC_B of the second network B has set-up a path therethrough, this fact may, if required, be signaled also to the first network A and thereafter the mobile station 1 only communicates with and through the second network B. The time scheduled dual mode can minimize the interruption so that the user of the mobile station 1 may experience only a very little disturbance of the communication or may even hardly notice the interruption. The scheduling during the transition period can be made so that packets or frames are received only during predefined intervals in one system at a time, this leaving the remaining time for the mobile station to interact with the other system. In the schematic of Fig. 2 the dual scheduling mode is illustrated for the specific example of a transition from communication in an LTE network to a 2G network such as a GSM network.

The general scheduling method is illustrated in the timing diagram of Fig. 5. Initially, in a first period pi the mobile station 1 (MS) is communicating only with or through the first system A. Initiated either by the mobile station or the first system A, the mobile station enters the dual scheduling mode, also called an alternating scheduling mode, i.e. it starts an alternating scheduling period p2. In this period p2 the total system is in an alternating scheduling mode in which the mobile station 1 alternates in its communication with the first and second systems A and B. The inter-radio technology alternating scheduling pattern may e.g. be assumed to be known by both the first system A, the second system B and the mobile station. In the last period p3 the mobile station 1 has left the alternating scheduling period and is, in the case where only some information exchange has taken place between the mobile station and the second system B, again only communicating through the first system A, or is, as in the case illustrated in Fig. 5, involving a transfer of communication session, only communicating through the second system B.

The knowledge of the inter-radio technology alternating scheduling pattern that is used in the dual scheduling mode can be obtained in different ways such as:

- The pattern may be predefined and known by only the first system A that e.g. on request informs the mobile station 1 thereof which may in turn inform the second system B. - The pattern may be predefined by standardization for both the first system A, the second system B and the mobile station 1.

- The pattern may be predefined by standardization for only the first system A and the mobile station 1 whereas the second system B then can be unaware that the procedure of alternating between the two systems takes place. This presupposes that the first system A and the mobile station know the time structure when system B is in communication with the mobile station. Then, the first system A and the mobile station utilize gaps existing in this time structure to communicate between them. E.g. the SDCCH frame structure for a GSM network, see Fig. 4, may be known to the first system A and the mobile station 1.

- A set of alternative scheduling patterns may be predefined by standardization for both the first system A, the second system B and the mobile station 1, as will be described below with reference to Fig. 18. Then these three parties have to negotiate for which one to use.

In the flow diagram of Fig. 6 the main steps taken by the mobile station 1 are illustrated for the case where the radio node BS_A in the first system A initiates the dual scheduling mode. As an alternative, the dual scheduling mode can be initiated by some other party such as the mobile station itself such as will be described below with reference to Fig. 12. In a first step 61 the MS 1 receives a request for dual scheduling from the first network A, this request specifically indicating, in some suitable way, that the second system B will participate in the dual scheduling and also containing information about the task that the mobile station will execute in the communication with the second system B in the dual scheduling mode. In the next step 62 the MS decides whether it is capable of participating in the dual or alternating scheduling mode, i.e. whether it has been enabled for this operational mode such as by modifying its software. Receiving the request and the deciding can be performed by the control unit 101 of a dual scheduling unit 103 in the mobile station 1, see the block diagram Fig. 10. If it is capable, an acknowledgement message is sent to the first system A in a step 63. In the case where a dual scheduling map is not predefined for and known by the mobile station 1 the acknowledgement message can contain a request for a dual scheduling map or some information pointing to e.g. one of several predefined maps, already stored in the mobile station, to be sent from the first system A. This step can be performed by a corresponding unit or module 105 in the dual scheduling unit 103. Then it is determined in a step 64 whether a dual scheduling map or corresponding information has been received, i.e. the map is awaited for some predetermined time, and after or if it has been received a step 65 is executed, in which a confirming message is sent to the first system A.

In the next step 66 a procedure for performing the dual scheduling and performing the special task is initiated such as by a unit 107, using the information in the original request received from the first system A and the information about the dual scheduling map to be used. Then the toggling sending/receiving procedure is executed in a step 67, performing the requested task, as controlled by a unit 108. Then the dual scheduling mode is terminated in a step 68 such as after a communication path to and through the second system B has been established. The term "communication path" as used herein means a communication path or communication channel having one end at the mobile station 1 and passing through a radio access network into a core network, not shown. That a communication path has been established is thus herein taken to mean that a path, suitable for transmitting primarily speech but also data such as streaming data, has been established between the end user's mobile station 1, through a radio access network, into the core network, hi the flow chart of Fig. 6 the procedure is ended in a step 69. If it was decided in step 62 that the MS 1 is not enabled for dual scheduling or if a dual scheduling map has not been received during a predetermined time, as determined in the step 64, a dual scheduling abort message is sent to system A in a step 70. Then the procedure is terminated in the step 69.

Thereafter some other procedure, not illustrated or described in detail herein, can in the special case be used, such as performed or commanded by a unit 110, for moving the communication path from the first system A to the second system B, i.e. the mobile station will from this moment only communicate with and through the second system B.

The dual scheduling mode is started by the first system A when it receives the respective confirmation message that the dual scheduling map has been received. Then, first time intervals or frames are determined and used in which the communication between the first system A and the mobile station 1 is performed and also there are free time intervals, also called second time intervals, between the first intervals. In the second time intervals the communication between the mobile station and the second system B is performed. Hence, in the first free time interval between the first time intervals the mobile station 1 can send some message to the second system B, e.g. requesting that dual scheduling now will be performed, this corresponding to a first substep 171, see Fig. 17, included in the general step 67 of performing dual scheduling in Fig. 6 and executed by the unit 108. In such a message also, if necessary or suitable, some information can be added about the time or how a response should be sent, e.g. in a following predetermined frame, at a predetermined time or that multiple responses spread over time should be sent, such as a repeated, regular times or randomly. Then, in the next free time intervals the mobile station is in a substep 172 waiting for a response from the second system B for example confirming the dual scheduling mode and requesting a scheduling map for the following communication between the mobile station and the second system B. The request can be received by e.g. a unit 109 in the dual scheduling unit 133. Another unit 111 sends in a step 173 the scheduling map to system B if a request therefor has been received and otherwise a unit 113 sends an abort message to system B in a step 174 and also an abort system can be sent to system A in a step 175. Then, the substep procedure is ended in step 176. If a dual scheduling map was sent to the second system B, communication between the mobile station 1 and the second system B is then performed in a step 177 whereupon the substep procedure is ended in step 176.

It is also possible that the scheduled times for communicating with the two systems A, B are determined by e.g. the mobile station 1 itself. This could then be executed by a scheduling map determining unit 115 that can contain units 117 and 119 for comparing the timing, i.e. when packets or frames are ordinarily sent, in the two systems A, B and for evaluating said timing, respectively. Such units can use information on the two systems e.g. stored at memory places 121, 123 in a memory 125 of the dual scheduling unit 103. Such a memory then also has a memory area 127 in which the determined or predefined or received scheduling map is stored.

In Fig. 7 the main steps performed in the radio node BS_A in the first system A in the same case where the radio node initiates the dual scheduling mode are illustrated. In a first step 71 it is decided, either in the node itself or the node being informed thereof from some other component of the first network or possibly the core network, that a task will be executed that requires or can be best executed using dual scheduling for the mobile station 1, the mobile station then also communicating with the second system B. In the next step 72 a request for dual scheduling is sent to the MS 1. This step can e.g. be executed by a sending unit 131 included in a dual scheduling unit 131 in the node that also includes a control unit 135 and a memory 137, see Fig. 11. Then it is determined, or awaited for a predetermined time period, as indicated by the line 72 whether the node has received an acknowledgment message from the MS requesting a dual scheduling map, i.e. information from which the time periods for communication with system A can be derived, or a dual scheduling abort message. If an acknowledgment message has been received a message including information in regard of the dual scheduling map is sent to the MS 1 in a step 74, as from a unit 139. Then a message confirming the receipt of the dual scheduling map is awaited in step 75. If a confirming message is received, the dual scheduling mode is started and performed by a unit 141 in the next step 76 and the task is performed whereupon the dual scheduling is terminated in a step 77, e.g. after the MS 1 has established a communication path through the second system B. The procedure is ended in a step 78. If no acknowledgement message has been received during the predetermined time, the request for dual scheduling in step 72 can be repeated a predetermined number of times. If no acknowledgment message has been received or after time or after a dual scheduling abort message has been received from the MS 1 the procedure is also ended in the step 78.

The scheduled times for communicating with the two systems can be determined by e.g. the base station BSA- The control unit 135 or a special unit 143 could be used for e.g. retrieving a predetermined or predefined scheduling map from a memory place 145. The special unit 143 could also determine a suitable scheduling map from knowledge about the timing in systems A and B, this knowledge stored in memory places 147 and 149, respectively. The unit 143 can then contain units 117 and 119 for comparing the timing and for evaluating said timing, respectively.

In the flow diagram of Fig. 8 the main steps executed by a radio node BSB in the second system B in a procedure in which the mobile station 1 communicates the structure of the dual scheduling map to the second system B. In a first step 81 the radio node receives a request for dual scheduling from the MS. Then it is in next step 82 determined whether the node itself if capable of executing dual scheduling. If it is capable, an acknowledgement is sent to the MS 1 in a step 83, the acknowledgement requesting a dual scheduling map. In step 84 it is determined, or it is waited a predetermined time, whether a dual scheduling map has been received from the MS. After the map has been received, the dual scheduling mode is started in a step 85 and the procedure is ended in a step 86 after a communication path to the second system has been established. If it was determined in step 82 that the radio node is not capable of dual scheduling or if is determined in step 84 that no dual scheduling map has been received after a predetermined time, a message is sent in a step 87 to the MS that the dual scheduling is aborted. Then the procedure is terminated in the step 86.

The case where a set of alternative scheduling patterns is predefined for all participants and scheduling pattern is negotiate for is illustrated in the flowchart of Fig. 18. In a first step 181 there is somewhere in the general system decided that a task has to be executed that is best performed using dual scheduling. In step 182 system A sends to the MS 1 information indicating preferred scheduling patterns, the scheduling patterns also called toggle schemes, selected from the predefined set of scheduling patterns, the information including a rank order for the preferred scheduling patterns. Information of each of the predefined patterns can e.g. be assumed to stored in each of the participants or at least is easily available to each of them. Information indicating the same preferred scheduling patterns, or possibly some subset thereof as selected by the MS, is from the MS sent to system B, in a time interval between the now more separated intervals in which the communication between the MS and system A is performed as described above.

System B receives the information and decides in a step 184 whether it can participate in dual scheduling according to an of the scheduling patterns which are indicated in the received information. If at least one scheduling pattern can be used, this is acknowledged in step 185 by sending a message to the MS 1 including information pointing to the acceptable scheduling patterns. The MS selects in the step 186 that scheduling pattern that has the highest rank according to the information received from system A in step 183 and sends information indicating this scheduling pattern to system A. The dual scheduling mode is started and performed and the task is performed in the next step 187 whereupon the dual scheduling is terminated in a step 188, such as by sending suitable abort message, and the procedure is ended in step 189.

If system B in step 184 determines that none of the proposed scheduling patterns are acceptable, it asks in a step 190 whether it is the Nth time that is makes this determining operation. If it is not, a step 191 is executed in which system B finds other scheduling patterns, selected from the predefined set, that are acceptable and sends information thereof to the MS 1.

The MS forwards this information to system A in step 192. System A then receives in a step 193 the information and evaluates whether any of the now proposed scheduling patterns can be used.

If it finds that at least one of now proposed scheduling patterns can be used, it sends an acknowledging message to the MS 1 in a step 194 , the message holding information indicating the suitable scheduling patterns. Then the step 186 is executed as described above.

If system B in step 190 finds that it is the Nth time that it makes the evaluation and determining in regard of proposed scheduling patterns indicated in received messages, the procedure must be aborted. Then the MS 1 is informed thereof in a step 195 and the MS in turn informs system A in a step 196, whereupon the procedure is ended in step 189.

If system A in step 193 determines that none of the new proposed scheduling patterns which are indicated in the message from the MS 1 is suitable or acceptable, it asks in a step 197 whether it is the Nth time that is performs this determination operation. If it is not, a step 198 is executed in which at least one new possible scheduling is selected, whereupon step 183 is performed as described above. If system A in the step 197 finds that it is the Nth time the procedure is aborted by informing the MS 1 thereof in a step 1995, the MS in turn informing system B in the following step 200, whereupon the procedure is ended in step 189.

The general method as described above can, in the case where a communication path is moved from an LTE network to a GSM network, see Fig. 2, be performed as follows. 1. The mobile station 1 communicates only in the LTE network. 2. A change of the communication to GSM instead is decided by the LTE network.

3. The LTE network requests that the mobile station shall start the dual map procedure and contact the GSM network.

4a. The mobile station 1 accesses the GSM system and indicates to the GSM that it should use an SDCCH for signaling and/or data transfer.

4b. The mobile station 1 accesses the GSM system with no indication of the dual scheduling mode or of any need for an SDCCH. This works well if the GSM system does not use the procedure "Assignment directly to a TCH (Traffic Channel)" since the channel that is to be setup and used will automatically be an SDCCH and the toggle map usage is secured. 4c. The mobile station 1 accesses the GSM system and indicates to the GSM that it should use a toggle map defined for dual mode scheduling. The GSM system then adapts the scheduling of signaling and/or data transfer over the air according to the toggle map.

4d. The mobile station 1 accesses the GSM system without a new indication. Then it is up to the mobile station to utilize the existing time gaps in the GSM system and try to synchronize this with the LTE system scheduling.

4e. The mobile station 1 accesses the GSM system with an indication that it desires multiple assignments spread over the time, as will be described below with reference to Fig. 13. In a second phase the mobile station in the assigned resources indicates that a toggle map shall be used or negotiated for. 4f. The mobile station 1 accesses the GSM system with an indication that it requires the assignment in a predefined frame. In a second phase the mobile station in the assigned resources indicates that a toggle map shall be used or negotiated for.

5a-5f. For the alternatives 4a - 4f the mobile station 1 and the LTE system continue to communicate in the initially existing communication path but only within time periods in which no GSM communication can be assumed to take place.

5c, 5e, 5f. For the alternatives 4c, 4e and 4f the GSM system uses the predefined time slots, i.e. in time slots in said allowed time intervals, and performs the signaling and/or data transfer procedure required to create a new communication path with the GSM system. 5a, 5b, 5d. For the alternative 4d, the GSM system performs the signaling and/or data transfer procedure required to create a new communication path with the mobile station 1 and is unknown about the fact that the mobile station is in communication with the LTE system.

6. The communication path is routed to GSM, e.g. done by IMS (IP Multimedia Subsystem), i.e. all communication with the mobile station 1 is now through the GSM network.

7. The LTE network releases the radio connection with the mobile station 1 when there are no more packets to send. This specific method is also illustrated in Fig. 9, where the time is divided in time segments si - s7. si. The MS 1 is engaged in an ongoing voice call over the packet data LTE system. The mobile station receives and sends voice frames via the LTE system. s2. In response to a handover decision the LTE system initiates the period of alternating scheduling and provides the MS 1 with information about the alternating scheduling pattern. s3. The MS 1 uses the first scheduling opportunity in the GSM system to inform the GSM system about the structure of the alternating scheduling pattern that is to be used. s4. In the alternating scheduling mode the MS 1 and the LTE system use the scheduling periods in LTE to exchange voice frames, thus maintaining the voice call in the LTE system. s5. During the GSM scheduling periods the MS 1 and the GSM system establish a GSM circuit switched traffic channel and path up to and through the core network. Such a circuit switched traffic channel is the communication path over the air interface. s6. Once the circuit switched traffic channel has been established in the GSM system the MS 1 sends a message "handover complete" to the GSM system that is forwarded to the core network, compare the arrows at the top of Fig. 2. The core network may then inform, if required, the LTE system that the voice connection is now routed through the GSM system. s7. The mobile station 1 is now using the circuit switched GSM channel to send and transmit voice frames according to the GSM protocols, i.e. a legacy GSM voice call is established. The special case where the mobile station 1 desires multiple assignments as mentioned in point 4e is illustrated in the timing diagram of Fig. 13 and can include the following initial steps. si. The mobile station 1 is engaged in an ongoing voice call over the packet data LTE system.

The mobile station receives and sends voice data frames via the LTE system. s2. In response to a handover decision the LTE system indicates the period of dual scheduling and provides the mobile station 1 with information about the dual scheduling pattern. s3. The mobile station 1 sends a resource request message to the GSM system, indicating that a dual scheduling procedure is to be started and that multiple responses, i.e. multiple Immediate assignments should be used. s4. The mobile station 1 continues to communicate in the LTE according to the dual scheduling pattern. s5. hi order to secure that the mobile station 1 has possibility to receive the responses to the access in step s3, the GSM is allowed to send multiple responses, this since the mobile station can not know exactly when to expect the response. In the case illustrated in Fig. 13 the two first responses are not heard by the mobile station since the mobile station is busy communicating actively with the LTE system when they are transmitted. In the general case and as briefly described above, the dual scheduling method allows a mobile station 1 to execute activities in a second network B in parallel to an ongoing service- communicated in a first network A. Examples of such activities include, in addition to the procedure of changing a communication described above, presence signaling and/or data transfer in a WiMAX network in parallel to a file transfer operation in an LTE network and a positioning activity in an LTE network in parallel to an Internet session in a WiFi network. Other examples include probing for radio resources and radio quality in a WiMAX network in parallel to a file transfer in GSM and probing for radio resources and radio quality in LTE in parallel to an Internet session in a WiFi network. Such a procedure comprising an activity with or through a second parallel network is illustrated in Fig. 12 for the case of presence signaling and/or data transfer in an LTE system in parallel to an ongoing data service in a WiMAX network. The procedure includes the following general steps. si. The mobile station 1 is engaged in an ongoing data service in the WiMAX system. The mobile station receives and sends data PDUs via the WiMAX system. s2 In response to an internal timer related to the presence service the mobile station 1 sends a request to enter the dual scheduling mode to the WiMAX system. s3. The WiMAX system responds with a message the contains information about the structure of the dual scheduling map to use and grants the mobile station 1 to initiate the dual scheduling mode with the LTE system. s4. The mobile station 1 uses the first LTE communication time period to request the dual scheduling mode according to the message received from the WiMAX system in step s3. s5. The LTE system responds to the mobile station 1 with a dual scheduling accept message. The mobile station, the WiMAX system and the LTE system are now in agreement and all three systems conform to the dual scheduling procedure according to the dual scheduling map communicated in steps s3 and s4. s6. While in the dual scheduling mode the mobile station 1 synchronizes to the WiMAX system during time periods as instructed in the dual scheduling map communicated in steps s3 and s4. During these time periods the mobile station can be scheduled for UL and DL radio communication with the WiMAX system. The mobile station 1 and the WiMAX system use the scheduling opportunities to transfer data packets, thus maintaining the ongoing data service as described for step si . s7. While in the dual scheduling mode the mobile station 1 synchronizes to the LTE system during time periods as instructed in the dual scheduling map communicated in steps s3 and s4. These time periods are non-overlapping with the time periods used in the steps s6. There are further guard times between the time periods as described for steps s6 and s7 which the mobile station 1 uses to switch its sender and receiver between the WiMAX and LTE system. During the

LTE time periods the mobile station can be scheduled for UL and DL radio communication with the LTE system. The mobile station 1 and the LTE system use the scheduling opportunities to send data packets associated with the presence service mentioned in step s2. s8. After the mobile station 1 has determined that there are no more data packets associated with the presence service for the LTE system to be transferred it sends a "Dual scheduling release request" message to the LTE system. s9. The LTE system responds with a "Dual scheduling release accept message". At this point of time the LTE system leaves the dual scheduling mode. s 10. The mobile station 1 sends a "Resume standard scheduling mode request" to the WiMAX system. si 1. The WiMAX system responds to the request in step slO by sending a "Resume standard scheduling mode accept" message to the mobile station 1. At this point of time both the mobile station and the WiMAX system terminate the dual scheduling mode. s 12. The mobile station 1, the WiMAX system and the LTE system are now all back in the respective standard scheduling mode that can be also called single scheduling mode.

It should be obvious for anyone skilled in the art that the dual scheduling procedure as described herein above can be used for other services including positioning, broadcast TV, interactivity for mobile TV sessions in other networks, periodic network updates, web browsing and others.

Another example of a procedure comprising an activity with or through a second network in parallel to a session in a first network is illustrated in Fig. 14. hi this example it is probed for radio resources and radio quality in a WiMAX network in parallel to a file transfer operation in a

GSM network. The procedure includes the following main steps. si. The mobile station 1 is engaged in an ongoing data service in or through the GSM system.

The mobile station receives and sends data PDUs via the GSM system. There is no interface available between the RRM nodes of the GSM and WiMAX systems, and hence the only way for the RRMs to communicate is through the mobile station, see Fig. 16. s2. When the GSM system wants to find out the resource load and the quality of the radio conditions in the neighbouring WiMAX system it orders the mobile station 1 to perform a probing session. s3. The mobile station 1 uses the first WiMAX communication time period to request dual the scheduling mode according to the message received from the GSM system in step s2. s4. The WiMAX system responds to the mobile station 1 with a dual scheduling accept message. The mobile station, the GSM system and the WiMAX system are now in agreement and all three systems conforms to the dual scheduling mode according to the dual scheduling map communicated in steps s2 and s3. s5. While in the dual scheduling mode the mobile station 1 synchronizes to the GSM system during time periods as instructed in the dual scheduling map communicated in steps s2 and s3. During these time periods the mobile station can be scheduled for UL and DL radio communication with the GSM system. The mobile station 1 and the GSM system use the scheduling opportunities to transfer data packets and thus maintaining the ongoing data service according to step si. s6. While in the dual scheduling mode the mobile station 1 synchronizes to the WiMAX system during time periods as instructed in the dual scheduling map communicated in steps s2 and s3. These time periods are non-overlapping with the time periods used for steps s5. Further, there are further guard times between the time periods used for steps s5 and s6 which the mobile station 1 uses to switch its sender and receiver between the GSM and WiMAX systems. During the WiMAX time periods the mobile station can be scheduled for UL and DL radio communication with the WiMAX system. The mobile station 1 and the WiMAX system use the scheduling opportunities to send test data packets to evaluate the radio quality of the WiMAX radio connection, and to communicate with the RRM (Resource Management Unit) of the WiMAX system for a load estimation of the WiMAX system. The test data packets that are sent by the WiMAX system and the mobile stations are according to predefined coding for a better evaluation of the radio quality for different modulations. s7. After the mobile station 1 has determined that there are no more data packets associated with the radio quality and load probing session as mentioned in step s2 to be transferred it sends a "Dual scheduling release request" message to the WiMAX system. s8. The WiMAX system responds with a "Dual scheduling release accept" message. At this point of time the WiMAX system leaves the dual scheduling mode. s9. The mobile station 1 sends a "Resume standard scheduling mode request" to the GSM system together with the information about radio quality and load of the WiMAX system. slO. The GSM system responds to step s9 by sending the message "Resume standard scheduling mode accept" message to the mobile station 1. At this point of time both the mobile station and the GSM system terminate the dual scheduling mode. si 1. The mobile station 1, the WiMAX system and the GSM system are now all back in their respective standard scheduling mode.

In a general, similar case for the network system illustrated in Fig. 16 the following main steps can be performed. 1. Measurement reports from the mobile station 1 about neighbor cells are sent to the serving base station, indicated by the arrow.

2. The serving RRM wants more information about a certain neighbor cell and orders the mobile station 1 to probe the situation for a certain cell.

3. The targeted cell is activated for this support, e.g. by a BCCH broadcast of a new or updated System Information. This can also be used to deny this kind of access during traffic peaks.

4. The mobile station 1 shall access the targeted cell. For e.g. a GSM network a new Establishment Cause in the Channel Request can be used.

5. The targeted base station answers the mobile station 1 with an assignment for a resource. On this resource the mobile station and the base station exchange at least one radio packet in each direction that can be used for evaluation of the neighbor cell. This exchange can be executed using a dual scheduling procedure as described herein. The targeted RRM also informs about the load situation in the cell.

6. The mobile station 1 informs about the result of this probing operation to the "home base station", i.e. the serving base station , which then forwards this information to the serving RRM. In this case there is no need for the mobile station 1 to get in contact with functions higher up than the target RRM, e.g. in GSM there is no need for the mobile station to involve more nodes than a BTS and the BSC to which it is connected.

The scheduling periods in the respective system may, while in the dual scheduling mode, advantageously be short enough not to cause significant latency additions to the data transfers in either system. In the case where an activity with or through a second network is executed in parallel to an ongoing, continuing session in a first network the time periods could e.g. be of the order of 10 - 30 ms while other time periods can be considered for other cases such as for transferring an ongoing voice session to another network. It should also be obvious that either or both of network one and network two can be any radio communication system including e.g. GSM, GPRS, EDGE, TETRA, WiMAX, HSPA, EV-DO, LTE₅ DVB-H and WiFi.

Using the method as described one or more of the following advantages may be achieved, at least in special cases:

- Only a single radio unit is used, i.e. single radio technology is used. "Single radio" means that a mobile station can at each instant be in active communication with only one system. - A minimum interruption in the user plane during handover between different networks, in particular between networks of different kinds.

- An RRM interface is not required for load sharing cases.

- A possibility is provided for the serving resource management unit to find out the radio quality for both uplink and downlink in a target cell. - An LTE MME/UPE does not have to use an interface towards an MSC. While specific embodiments of the invention have been illustrated and described herein, it is realized that numerous additional advantages, modifications and changes will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative devices and illustrated examples shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes as fall wrttiin a true spirit and scope of the invention.

Claims

1. A method in a mobile station comprising the step of.

- communicating over a first communication path via a first cellular network, characterized by the further steps of: .^{• •} ■^• . ...

5 - entering a dual scheduling mode wherein communication over the first communication path is scheduled to take place in first time intervals; and

- communicating with a second cellular network in second time intervals between the first time intervals.

2. A method according to claim 1, wherein communication with the first and second cellular 10 networks is performed using different radio access technologies.

3. A method according to claim 1, wherein said communicating with the second cellular network is used for setting up a communication path for data transmission via the second cellular network.

4. A method according to claim 3 comprising the additional steps of: 15 - ceasing the communicating over the first communication path,

- terminating the dual mode scheduling mode, and

- communicating over the second communication path.

5. A method according to claim 1, wherein, after said dual scheduling period, the mobile station ceases the communicating with the second cellular network and only communicates with

.20 and through the first cellular network.

6. A method according to claim 1, wherein said communicating with the second cellular network includes that data are transferred in a direction from the second cellular network to the mobile station, or in a direction from the mobile station to the second cellular network, or in both directions.

25 7. A method according to claim 1 comprising the additional steps of:

- receiving from the second cellular network assignment of the second intervals and identifying frame synchronization information in the assignment; and

- signaling to the first network information on the frame synchronization in the second cellular network.

30 8. A method according to claim 1, wherein information when the second time intervals may be scheduled is received from the first cellular network. ^■ . ■ .

9. A method according to claim 8 comprising the additional step of forwarding, to the second cellular network, the information when the second time intervals may be scheduled.

10. A method according to claim 1, wherein information when the second time intervals may 35 be scheduled is received from the second cellular network.

REGTIFiED SHEET (RULJE Si)

11. A method according to claim 10, wherein the information when the second time slots may be scheduled is forwarded to the first cellular network for adapting the first time intervals.

12. A method according to claim 1, wherein presence signaling is performed in the second ■ ^■ time intervals.

5 13. A method according to claim 1, wherein in the second time intervals, the mobile station measures the radio quality and receives information on the uplink radio quality and resources from the second cellular network.

14. A method according to claim 1, wherein in the communication in the second time intervals mobile TV interactivity signaling is performed through the second cellular network. 10

15. A method according to claim 1, wherein, after said dual scheduling period, the mobile station ceases communicating with the second cellular network and only communicates with and through the first cellular network.

16. A method according to claim 1 in the case where the second cellular network is a GSM network, comprising the additional step of sending, from the mobile station to the GSM network

15 and before entering said dual scheduling mode, a request for an SDCCH.

17. A method according to claim 1 in the case where the second cellular network is a GSM network, comprising the additional step of sending, from the mobile station to the GSM network and before entering said dual scheduling mode, a request for assignment of resources in or at a specific time.

20 18. A method according to claim 1 in the case where the second cellular network is a GSM network, comprising the additional step of sending, from the mobile station to the GSM network and before entering said dual scheduling mode, a request for multiple assignments of resources spread over time.

19. A mobile station adapted for performing the method according to claim 1 or any claim 25 dependent on claim 1.

20. A mobile station according to claim 19 comprising:

- a radio transceiver adapted for handling two radio access technologies, one radio access technology for communicating with the first cellular network and another one for communicating with the second cellular network;

30 - a first set of units, connected to the radio transceiver, and arranged for handling the communicating, through the radio transceiver, with the first cellular network;

- a second set of units, connected to the transceiver, and arranged for handling the communicating, through the radio transceiver, with the second cellular network; and

- a dual scheduling unit arranged to control the first and second sets of units to alternate the com- 35 municating between the first and second time intervals allocated for communicating with

RECTIFIED SHEET (RUlS 91) respectively the first and second cellular networks.

21. A mobile station according to claim 20, wherein

- the second set of units is arranged to acquire, from the communicating with the second cellular network, information necessary a to set up a communication path through the second cellular • ^• network, and to. set up this communication path; and .• ■ ^■

- the dual scheduling unit is arranged to command, after the set of second units has set up the . communication path with the second cellular network, the first set of units to stop communicating with the first cellular network, and the set of second units to use the now set-up communication path through the second cellular network.

22. A mobile station according to claim 21, wherein the first and second sets of units are arranged so that the communication path between the mobile station and the first cellular network can be replaced with the communication path between the mobile station and the second cellular network.

23. A mobile station according to claim 21, wherein the second set of units is arranged so that mobile TV interactivity signaling can be performed using the now set-up communication path through the second cellular network.

24. A mobile station according to claim 20, wherein the second set of units is arranged to perform, in the second time intervals, presence signaling with the second cellular network.

25. A mobile station according to claim 20, wherein the second set of units is arranged to measure the radio quality and/or to receive information on the uplink radio quality and resources from the second cellular network in the second time intervals.

26. A mobile station according to claim 20, wherein the first and second sets of units are arranged so that after said dual scheduling period, the mobile station ceases communicating with the second cellular network and only communicates with and through the first cellular network.

27. A mobile station according to claim 20 further comprising a memory place for storing information on times when the communicating with the second network can be performed, the second set of units adapted to use this information when commanded by the dual scheduling unit to perform the communicating with the second cellular network.

28. A mobile station according to claim 20, wherein the dual scheduling unit includes a sending unit for sending, to the second cellular network and before the entering of the. dual scheduling mode; information on times when the communicating with the second network' is to take place. . ^■

29. A mobile station according to the combination of claims 27 and 28, wherein the sending unit is adapted to retrieve, in sending said information, the information from said memory place.

30. A mobile station according to claim 20 further comprising a single radio transceiver for

BECTIFiED SHEET (RULE 91) 2? communicating both with the first cellular network and the second cellular network.

31. A. mobile station according to claim 20 further comprising a unit for comparing the timing of the frame structures in the first and second cellular networks. ^•

32. A mobile. station according to claim 31, wherein the mobile station is adapted to report . . 5 the result of the comparison to at least one of the first and second cellular networks.

33. A mobile station according to claim 20, wherein the second set of units is arranged to inform, in the second time intervals, the second cellular network of the way in which the following communication between the mobile station and the second cellular network is to be

^• performed.

10 34. A mobile station according to claim 33, wherein the second set of units is arranged to inform the second cellular network that a dual scheduling map will be used for the communication between the mobile station and the second cellular network.

35. A mobile station according to claim 34, wherein the second set of units is arranged to communicate, in the second time intervals, a request message and that multiple responses to the

15 request message spread over the time are to be sent.

36. A mobile station according to claim 34, wherein the second set of units is arranged to communicate, in the second time intervals, a request message and that a response to the request message is to be sent at a predetermined time.

37. A mobile station according to claim 34, wherein the second set of units is arranged to 0 communicate, in the second time intervals, a request message and that a response to the request message is to be sent in a predefined frame.

38. A mobile station according to claim 20, wherein the set of second units is arranged to inform, in the case where the second cellular network is a GSM system, the GSM system of the way in which the communicating with the GSM system is to be executed. 5

39. A mobile station according to claim 38, wherein the set of second units is arranged to inform that an SDCCH is to be used for the communicating with the GSM system.

40. A mobile station according to claim 20, wherein the set of second units is arranged to send, in the case where the second cellular network is a GSM system and before entering said dual scheduling mode, to the GSM network a request for assignment of resources in a specific .0 time. . . . .

41. A mobile station according to claim 20, wherein the set of second units is arranged to send, in the case where the second cellar network is a GSM system and before entering said dual . scheduling mode, to the GSM network a request for assignment of resources in predefined frame:

42. A mobile station according to claim 20, characterized in that the- set of second units is5 arranged to send, in the case where the second cellular network is a GSM system and before

RECTIf-lED SHbt i v -vn^ w entering said dual scheduling mode, to the GSM network a request for multiple assignments of resources spread over time.

43. A method in a radio base station arranged to support radio communication with at least one mobile station comprising the step of: - communicating with the at least one mobile station in a regular mode applying a first scheduling, . characterized by the further step of:

- entering a dual scheduling mode for communication with the mobile station wherein the communicating with the mobile station is scheduled to be performed in first time intervals with free time intervals between the first time intervals.

44. A method according to claim 43 comprising the further step of determining, before the step of entering the dual scheduling mode, that the dual scheduling mode will be entered.

: 45. A method according to claim 44 in the case where the radio base station is connected to or in a first cellular network, wherein the determining is based on one of: - a decision to handover the mobile station to a second cellular network,

- a need for receiving information on a second cellular network via the mobile station, and

- that a service requested by the mobile station cannot be supported by the first cellular network.

46. A method according to claim 44, wherein the entering step is preceded by receiving a request from the mobile station for entering the dual mode. .

47. A method according to claim 43 comprising the further steps of:

- receiving from the mobile terminal information when the free time intervals should occur, and

- adapting the first time intervals according to said received information.

48. A method according to claim 43 comprising the further step of informing the mobile terminal on a schedule for the free time intervals.

49. A base station for a first telecommunication network and adapted to perform the method according to claim 43 or any claim dependent on claim 43.

50. A base station according to claim 49 further comprising a dual scheduling unit arranged . to control the base station to communicate with the mobile station only in the first time intervals.

RECTIFIED SHEET (RULg §1) ISA/EP.