Abstract:
The present invention relates to an apparatus and method for estimating down link wide-band interference power and noise power in a mobile communications system. By using filters that are matched to the multipath channels of a number of base stations the received powers from the base stations may be differentiated and calculated. The impulse responses of the multipath channels are estimated and the filters are matched such that the impulse response of each filter is the complex conjugate of the time reverse of the estimated impulse response of one of the multipath channels. White noise is modelled as a signal that has passed a single-ray channel. The received noise power is estimated by means of the output signals from the matched filters and the total received signal.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to methods and arrangements in a mobile 3 rd  generation communication system and user equipments intended for usage in such systems. It relates in particular to situations when certain services, e.g. related to emergency calls, in the UTRAN are not available while the user equipment could perform this service also over a backup network, e.g. a GSM-network, which it can access.  
       SUMMARY OF THE INVENTION  
       [0002]     The present invention relates to the radio network part (UTRAN) of a 3 rd  generation communication system, e.g. a WCDMA-system, to which the following will refer to as an example, and addresses in particular problems that may arise when certain services, which the network is supposed to offer, are unavailable, e.g. due to faults in one of the units or links of said communication system or due to temporary congestions in said communication system.  
         [0003]     Present 3 rd  generation communication systems, as standardised by the 3 rd  Generation Partnership Project (3GPP), do not fully support to use another communication system, e.g. a GSM-system, as a backup system for services that are temporarily unavailable. Vice versa, there is presently no full support to use the UTRAN as a backup system, e.g. of a GSM-system, which is only used for certain services. Instead, a user equipment must stay in the communication system, which it presently is associated to, although a required service is presently not available or the user equipment is forced to move entirely to the backup communication system, although certain services that are needed by the user equipment would still be available in the disturbed system.  
         [0004]     It is therefore an object of the present invention to increase the availability of services to user equipments even when the UTRAN temporarily does not work properly with regard to a certain service. Within the scope of the present invention, services relate to such services that can be performed typically in the one network, e.g. the UTRAN, but also in a backup communication network, e.g. the GSM-system. One important example of such services relates, e.g., to emergency calls. However, the invention is notwithstanding also applicable for other kinds of services.  
         [0005]     It is a further object of the present invention to achieve a prioritisation with respect to certain services between a first and a second communication network, i.e. certain services are preferably performed in one of the communication networks although the user equipment remains associated with one network.  
         [0006]     This and other objects of the present invention are achieved by a communication system and a user equipment that are capable of providing the following features:  
         [0007]     1) An appropriate network unit  12  within the UTRAN  10 , e.g. the Radio Network Controller serving said user equipment, comprises means to inform user equipments  14  that are served by said system  10  about UTRAN services that are not available and, optionally, additional information that may indicate, e.g., a reason for said unavailability or an estimated time interval within which a service is unavailable. Possible reasons for such service unavailability can be, e.g., a network fault or a traffic congestion. Alternatively, the network  10  can instead indicate the still available alternatives in case of a network fault. More generally, the UTRAN  10  comprises an appropriate status information with regard to the availability of at least a certain range of its services.  
         [0008]     2) The network  10  is capable to re-direct a user equipment  14  to a backup network  11 , e.g. a GSM-network, in cases where a needed service in the UTRAN  10  is not available. It is thus possible for the user equipment to use available services in UTRAN while the network or user equipment can arrange that temporarily unavailable services are instead provided by the backup network  11 .  
         [0009]     3) A user equipment  14  comprising means to indicate to the network the priority of new requested services. The priority information can be used by the network, e.g., when the user equipment requests a temporarily unavailable service while already using another network service. Then, the re-direction is only performed if the new service has a higher priority.  
         [0010]     It is a first advantage of the present invention that the service availability is increased although, e.g., a fault or temporary congestion limits or prevents a user equipment from using this service in the network, which it is associated to.  
         [0011]     It is thus a further advantage of the present invention that the overall availability of services can be increased due to the possibility to obtain certain services from the one or other network, which can be used advantageously in congestion situations and, thus, can serve for load control purposes.  
         [0012]     It is still another advantage of the present invention that the time within which a user equipment is not pageable after a RRC Connection Release message and data interrupt times are significantly reduced.  
         [0013]     Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings and claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  shows a first and second communication network within which the present invention can be applied.  
         [0015]      FIG. 2  illustrates an RRC Connection Establishment procedure in UTRAN.  
         [0016]      FIG. 3  illustrates the RRC Connection Release procedure in UTRAN. 
     
    
     DETAILED DESCRIPTION  
       [0017]     According to a first aspect of the present invention the communication system  10  comprises means to inform user equipments  14  that are served by said system about the availability of UTRAN services. This network means is capable to inform the user equipment  14  about services, or at least a certain range of services, that are not available or inform it about available alternatives for the use of a certain requested service. It is then up to the user equipment, or the user, to select the appropriate network when requesting for a new service. This can be realised by means of including such availability information in an appropriate information message that is sent within certain time periods, e.g. the system information that is updated periodically and sent to the user equipment  14 . The information element transmitted in such a message should be such that all user equipments are requested to read this information when the system information is updated. This could be achieved by applying mechanisms that are currently specified in the Technical Specification document 3GPP TS25.331 “RRC Protocol Specifications” where a system information block is repeatedly sent on the BCCH with a certain periodicity. For instance, a system information block type  1 , which currently contains core network related information, can also include indications about service availability. When the system information carrying the indications are updated a Paging type  1  message is sent to all user equipments in the cell with an information about the updated BCCH, which is also specified in said document 3GPP TS25.331. The user equipment  14  comprises the necessary means to perform a switch to the backup network  11  immediately if a service that is requested by the user equipment  14  is indicated to be unavailable. This method implies the advantage that the system information also covers all idle user equipments and user equipments on common channels. Alternatively, it would be possible to include availability information in a dedicated message, e.g. in the UTRAN mobility information, and send this information to the user equipments on dedicated channels whenever the information changes.  
         [0018]     In a conceivable embodiment of the present invention, the user equipment comprises means to inform the user about the unavailable service, either immediately or as soon as the user takes any actions to request an unavailable service. By that the user is also able to choose the appropriate priority level for a new requested service.  
         [0019]     The following describes an example of the above mentioned functionality in said network  10  and said user equipment  14 : When assuming that the Iu-link towards a circuit-switched core network is interrupted, while the corresponding Iu-link towards the packet-switched core network works as usual, a user equipment  14  that is about to make, e.g., an emergency call is informed and can realise that the circuit-switched services are not available and instead set up a call over the backup network  11 . Then, the same user equipment  14  when downloading packet data can continue to use the packet-switched core network part as usual on the original network or transfer also the packet-switched core network part to the backup network  11 .  
         [0020]     According to a second aspect of the present invention the network  10  is capable to re-direct a user equipment  14  to a backup network  11  in cases where a needed service in the UTRAN  10  is not available. The following describes thus an embodiment where the network arranges said re-direction autonomously with consideration of the assigned priority for said service where the user equipment is not involved in the decision for re-directing. There could be several reasons that services are not available: Link interruption, e.g. an Iu-link break, various congestion situations in the communication system, or resource shortages, e.g. for a call setup. This is true both when the user equipment  14  already applies a certain service that suddenly becomes unavailable or when the user equipment  14  requests for a new service. The user equipment can only apply services in one network at a time whereby the communication network  10  comprises the necessary means that enable the user equipment  14  to use those services that are still available in its present communication network  10  and re-direct the user equipment  14  to a backup network  11  if a requested service is not available but offered in said backup network  11 .  
         [0021]     In order to always be able to re-direct a user equipment  14  from UTRAN  10  to, e.g., a GSM-network  11 , an information element (IE) denoting a re-direction retry indication must be included in the RRC Connection Setup Reject message, as provided for in the Technical Specification document 3GPP TS25.331, issued by the 3GPP, but at least the same parameters must also be included in the RRC Connection Release message. It is essential that this re-direction retry indication is included in said RRC Connection Release message as it is otherwise not possible to re-direct the user equipment  14 , e.g., to said GSM-network  11  until said user equipment  14  makes a new access from its idle state.  
         [0022]     This becomes apparent from the following example: If the user equipment  14  already has a connection towards a core network domain, a new request will be made with an already established RRC Connection instead of starting from the idle mode. When the original attempt fails, the user equipment  14  still has the RRC-Connection, it will make a new attempt, which also fails, i.e. the user equipment  14  is locked in UTRAN  10  where the requested service is not available. Moreover, if the current connection is, e.g., towards the packet-switched core network and UTRAN  10  releases said user equipment  14  at, e.g., an incoming circuit-switched call (without a re-directed retry) it is very likely that the application in the user equipment  14  will connect again to the packet-switched Radio Access Bearer in the UTRAN before the user equipment has had the possibility to make a new attempt from its Idle mode towards the circuit-switched core network potentially through any existing backup network.  
         [0023]     The following describes several examples of re-directions of user equipments  14  to a backup network  11 :  
         [0024]     1) A user equipment  14  has an ongoing emergency call when a Iu-link break towards the circuit-switched core network occurs. In this case, the call is to be released and re-directed to the backup network  11 , e.g. the GSM-network. The UTRAN  10  releases the RRC connection by sending a RRC Connection Release message, as specified above, to the user equipment  14 . The RRC Connection Release message includes the re-direct indication to, e.g., the GSM-network  11  so that the user equipment  14  does not retry to connect through UTRAN  10  again where the last connection failed.  
         [0025]     2) A user equipment  14  having an ongoing communication over a packet-switched Radio Access Bearer when there is a Iu-link break towards the circuit-switched core network intends to apply a temporary unavailable service, e.g. to set up an emergency call. In this case, the user equipment  14  shall be released and re-directed to the backup network  11 , e.g. the GSM-network. Also for this case, the UTRAN  10  releases the RRC connection with a RRC Connection Release message including an indication that the user equipment shall try, e.g., the GSM-network instead. Without this indication a normal RRC Connection release would lead to that the user equipment  14  appears to remain connected to the UTRAN  10  and will try to establish, e.g., currently unavailable service once more in this network. This is true especially since the ongoing packet-switched radio access bearer will try to re-establish the connection directly after the RRC connection release to the UTRAN, where the packet-switched services are available.  
         [0026]     3) A user equipment  14  that wants to establish a packet Radio Access Bearer but fails due to a congestion shall have a possibility to be re-directed to a backup network  11 , e.g. the GSM-network. For this purpose an appropriate information element (IE) denoting the re-direction retry indication is included in the RRC Connection Release message, said information element including at least the same parameters as specified in the RRC Setup Reject message in order to re-direct the user equipment  14  to said backup network  11 . If the packet-switched Radio Access Bearers are not available in the one network, the circuit-switched Radio Access Bearers can still be used in that network; however, if a user equipment wants to set up a packet connection it could be re-directed to the backup network that would provide the packet-switched Radio Access Bearers, e.g. in this case a GPRS-based network.  
         [0027]     The present invention also allows shortening times within which a user equipment  14  is not pageable after a RRC Connection Release message and shortening of data interrupt times. This becomes apparent when assuming, e.g., that the UTRAN  10  releases a packet-switched connection, e.g. due to a congestion. Then, the data transfer interrupt time might be less if the user equipment  14  is directed to the backup network  11  after a RRC Connection Release message compared to the time during which the user equipment  14  could not transmit any data at all until the congestion in the original network  10  has been resolved. When assuming on the other hand that, e.g., the core network, or connections to it, do not work properly it would not be possible to page user equipments  14 . In this case the time during which the user equipment  14  is not pageable can be significantly reduced by re-directing said user equipment  14  to the backup network  11  after a RRC Connection Release instead of waiting until the original network  10  works properly again.  
         [0028]     When seen from the perspective of the user equipment, the present invention enables the user equipment  14  to inform the UTRAN  10  about the priority of requested services. In order for the UTRAN  10  to make the right decisions regarding whether a user equipment  14  should be re-directed to a backup network  11  or not it is important that the user has a possibility to inform the UTRAN  10  about the priority of a requested service and if current services should be released to make sure that the new attempt will work. In order to cover service requests both for the idle user equipments and user equipments that already are connected, the indications for “priority” and “allow to release other services” are both included in the RRC Connection Request, the Initial Direct Transfer, the UL Direct Transfer, and the Cell Update.  
         [0029]     This can be explained by help of an example: Assuming a user equipment having an ongoing Radio Access Bearer and requesting a new Radio Access Bearer. The reason why this request fails could be, e.g., a congestion in the transport network or that a service-server is not available. If the user can inform the UTRAN about the priority level of the requested Radio Access Bearer, e.g. a high priority, and that a release of other services is allowed, the UTRAN may release the user equipment using the RRC Connection Release with re-directed retry in order to be able to use the new requested service in a backup network, e.g. GSM or GPRS.