Patent Publication Number: US-2002001291-A1

Title: Page response on existing radio signaling channel

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
     [0001] This application relates to U.S. Application Ser. No. ______ filed ______, (Atty. Docket No. 2380-18); entitled “Common Channel Changing” which is incorporated herein by reference. 
    
    
     
       FIELD OF THE INVENTION  
       [0002] This invention relates to telecommunications and more particularly to communication protocols in a mobile radio network.  
       BACKGROUND OF THE INVENTION  
       [0003] Mobile radio networks are wide-spread today and provide a mobile radio user with a large variety of communication options, including voice communications, data communications, short message service communications, voice paging communications, etc. As mobile radios become increasingly prolific in society, the strain on mobile radio communication network to accommodate the volume of mobile radio communications increases. For this reason, efficiencies are always desired in the mobile radio communications environment to simplify and improve call connection procedures and call connection protocols between telephone networks and mobile radios accessing them.  
       [0004] Typically, when a call request is made from a core telephone network to a mobile radio, the core network sends a page request through a radio access network to the mobile station. This page request is sent via a common paging channel monitored by all of the mobile stations assigned to the radio access network. The page request includes a unique identifier associated exclusively with the mobile radio to which the call is destined. The mobile radio (which, as stated previously, is monitoring the page channel) receives the page request and identifies the unique mobile radio identifier associated with the page request as its own. The mobile station then initiates a connection between itself and the caller. The call connection is performed by the radio access network by assigning a channel for use between the mobile station and the core network through which the mobile station and the call originator can communicate.  
       [0005] One of ordinary skill in the art will understand that radio access networks consist of a variety of basic building blocks such as base stations, base station controllers, mobile service switching centers, etc., which permit the mobile stations to communicate with a number of core networks as public telephone switched networks, etc. In this regard, throughout this specification, the phrase “generic radio access network” will refer to the building blocks requested to perform the call connection procedures between a mobile terminal and a core network.  
       [0006] As the volume of traffic in the mobile radio environment increases, it becomes increasingly likely that mobile stations receive simultaneous requests for call connections (or receive a request for a call connection while engaged in an active call). In such situations, the mobile station usually acknowledges to the second requester that it is busy with another call on another channel and therefore cannot accept the second call. It is possible, however, with current technology, for the mobile stations to accept two calls simultaneously, provided the generic radio access network can employ an efficient procedure to connect them. Thus, for example, a mobile station can engage in an active voice telephone call with one core network and still receive on another channel a short message service message from another core network, which can be displayed to the user when the voice telephone call is completed. Unfortunately, however, the present systems usually require the mobile station to employ multiple channels to receive multiple simultaneous messages.  
       SUMMARY OF THE INVENTION  
       [0007] In the present invention, a mobile station can receive simultaneous messages from two different core networks while employing only a single channel between the generic radio access network and the mobile station. Because the number of channels available to the generic radio access network to be employed simultaneously is limited, the consolidation of multiple simultaneous calls into a single channel reserves capacity in the generic radio access network for other mobile station call connections. In the preferred embodiment of the present invention, the simultaneous call connection is accomplished using a unique page procedure between the core networks, generic radio access network, and mobile station to which the simultaneous calls are destined.  
       [0008] First, a call is established between the mobile station and a first core network through the generic radio access network. Then, another core network pages the mobile station to initiate a second call connection. The page passes from the second core network through the generic radio access network to the mobile station via the dedicated page channel monitored continuously by the mobile station. The mobile station then returns the page response to the second core network using the existing signaling channel between the generic radio access network and the mobile station associated with the established user data channel. This is contrary to traditional thinking which would not provide the page response from the mobile station to the radio access network via the same channel in active use by the mobile station for the previously established call. In the present invention, the mobile station provides the page response to the second core network via the same channel being used for the established call (up to the generic radio access network) and via a newly established multiplexed channel (from the radio access network to the second core network). Thus, the page response triggers a multiplexing in the radio access network of two user connections: one from the radio access network to the first core network and a second from the radio access network to the second core network. The multiplexed connections are then fed from the mobile station to the radio access network via a single channel, preferably the previously established channel used by the first core network to communicate from the radio access network to the mobile station.  
       [0009] In alternative embodiments, the same procedure is used when a call is established with a first core network and a second call comes through the same core network. In such a case, the core network can multiplex the calls without coordinating with existing connections.  
       [0010] In some embodiments, the existing channel is reused. However, in other embodiments, the page message is kept uncoordinated (sent in parallel on the page channel). Thus, by avoiding the need to coordinate the page message with a possibly existing radio channel significantly reduces the complexity of the generic radio access network, e.g. in the case where a page request from the core network is sent to another node within the generic radio access network other than the one currently handling the connection to the mobile terminal. In this case, the added complexity in the mobile terminal to monitor a page channel in parallel to communication on a dedicated radio channel is minor compared to requiring the mobile terminal to receive and especially transmit two radio channels independently. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011] Other advantages and objects of the present invention will be described in detail with reference to the accompanying drawings, in which:  
     [0012]FIG. 1 is a schematic diagram of a simplified mobile radio network;  
     [0013]FIG. 2 is a schematic diagram of a page and page response in accordance with an example embodiment of the present invention; and  
     [0014]FIG. 3 is an example embodiment of a generic radio access network  10  in simplified form in accordance with an example embodiment of the present invention.  
    
    
     DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS  
     [0015]FIG. 1 illustrates a schematic diagram of a simplified mobile radio services network in accordance with an example embodiment of the present invention. In FIG. 1, core networks CN 1 , CN 2 , . . . CN n  communicate with a generic radio access network  10 . The principle function of the generic radio access network  10  is to establish channels for calls to connect between the various core networks CN 1 , CN 2 , . . . CN n  and the various mobile stations MS 1 , MS 2 , MS 3  . . . MS n  to which the generic radio access network  10  communicates. One of ordinary skill in the art will understand that the generic radio access network  10  comprises a number of basic building blocks including base stations, base station controllers, etc. The various functionalities of these building blocks are well-known in the art for establishing call connections between the core networks CN 1 , CN 2 , . . . CN n  and the various mobile stations.  
     [0016] In FIG. 1, a user data channel (UDC)  13  is established between core network  1  and mobile station  1  through the generic radio access network  10 . The UDC  13  consists of a signaling channel  14  and a traffic channel  15 . The UDC  13  is the channel assigned by the generic radio access network  10  for an active call between the core network  1  and the mobile station  1 . That is, in the instant in time reflected in FIG. 1, mobile station  1  is engaged in active communication between itself and the core network  1  via the UDC  13 .  
     [0017] At the same time, the mobile station  1  is continually monitoring the common page channel  12  of the generic radio access network  10 . Equally so, all of the mobile stations MS 2 , MS 3 , MSn are also monitoring the page channel  12  for page requests. The pages received via the page channel contain information identfying the mobile station to which the page is intended to be delivered. The mobile stations monitor the page channel  12  for pages, as shown in FIG. 1 (via the dotted lines).  
     [0018] In the moment in time shown in FIG. 1, although mobile station MS 1  is engaged in the active call between itself and CN 1  via UDC  13 , a page request comes from CN n  at channel  17  to the generic radio access network  10 , which passes the page request onto the common page channel  12  where it is received by the mobile station MS 1  via page request channel  16 . The mobile station MS 1  is thus in a conflict since it is engaged in an active call from CN 1  while receiving a page request on channel  16 . Traditionally, the mobile station MS 1  would have to respond to the page request (to CNN) by indicating its busy status or (if very sophisticated) by requesting a second UDC to be established between the CN 1  and the mobile station MS 1  via the generic radio access network  10 .  
     [0019] In accordance with the present invention, however, the situation shown in FIG. 1 is handled by multiplexing call connections from the core networks CN 1  and CN n  at the generic radio access network  10  such that the mobile station  1  receives both calls (from CN 1  and CN n ) simultaneously over a single UDC access channel portion  13 ′. In order to accomplish this, the page request sent from CNn to generic radio access network  10  (item  17 ) is received by the mobile station MS 1  via channel  16 . Then, MS 1  responds to the page request via UDC access channel portion  13 ′ (to the radio access network  10 ). That is, the mobile station receives the page request from core network CN n  and then responds to the page request on the same channel being actively used for a communication session with a different core network CN 1 . In particular, the page response from the mobile station MS 1  is sent to radio access network  10  via the same channel portion  13 ′ used by the core network CN 1  to engage in the active call with the mobile station MS 1 .  
     [0020] The receipt of the page response in the radio access network  10  triggers the situation illustrated in FIG. 3. In particular, the UDC  13  from core network CN 1  is shown entering the generic radio access network  10  and continuing through a multiplexer  33  to access channel portion  13 ′ to the mobile station MS 1 . Also, UDC  30  is established from core network CN n  to multiplexer  33  in the generic radio access network  10 . Like UDC  13  from CN 1 , the UDC  30  from CN n  includes a traffic channel  32  and a signaling channel  31 . The traffic channel  32  and signaling channel  31  connect communications between the core network CN n  and the multiplexer  33 . Then, when the MS 1  responds to a page request, it does so via channel  13 ′ to radio access network  10  (that is, the same channel being used previously to communicate from CN 1  to MS 1 ). MUX  33  then splits the signal such that data and signaling relevant to the previously established call are routed to CN 1 , while data and signaling relevant to the page response are routed to CN 1 . From radio access network  10 , the established call data and signaling travels via UDC  13  (as before) and the page data/signaling travels via channel  30  (established between radio access network  10  and CN n ).  
     [0021] Methods for routing traffic information in a multiplexer  33  are well-known and vary widely depending on the kinds of efficiencies desired and the practical constraints of core networks. One example method is to assign headers associated with the respective core networks (or, alternatively associated with the respective data types) to identify to the radio access network  10  (and specifically MUX  33 ) to which core network (and hence which caller) the data packets should be routed. One of ordinary skill in the art will well understand other ways to generically combine traffic information (such as packet data) in multiplexer  33 , as depicted in FIG. 3. The effect of multiplexing the traffic at MUX  33  is a single channel between the generic radio access network  10  and the mobile station MS 1  containing the traffic and signal information to/from both the core network CN 1  and the core network CN n . As depicted in FIG. 3, the same UDC  13 ′ is employed from the generic radio access network  10  to the mobile station MS 1  to provide the multiplexed traffic information  33  and the multiplexed signaling information  34  to the mobile station MS 1 , thus requiring the radio access network to assign and tie up only one channel ( 13 ′) for the one mobile station MS 1 .  
     [0022] As also depicted in FIG. 3, the mobile station MS 1  will continue to monitor the page channel  12  from the generic radio access network  10 .  
     [0023] As one of ordinary skill in the art will readily understand, the present invention allows a mobile station to receive simultaneous calls from two different core networks, without further burdening mobile station channel availability at the radio access network. This can be particularly advantageous when the mobile station is engaged in an active voice telephone call and receives a page request for, for example, a short message service message. While the user is engaged in the voice telephone call, the mobile station can receive the short message service message from another core network and then display the short message service message to the user when the user has completed the voice telephone call, all over the same channel  13 ′. Other types of simultaneous call embodiments can also be envisioned in which the present invention allows multiplexed simultaneous calls to be received by a mobile station on a single channel.  
     [0024] By assigning two simultaneous calls to the same channel between a generic radio access network and a mobile station, channel capacity in the generic radio access network is reserved for other calls between the generic radio access network and other mobile stations. This thus preserves channel availability and reduces consumed radio resources. In addition, the generic radio access network in accordance with the present invention needs only to coordinate the connections when the paging is successful, which reduces the load on the generic radio access network  10 .  
     [0025] The present invention also provides the advantage of eliminating any requirement of the generic radio access network to maintain a table of identities of mobile stations for paging coordination purposes.  
     [0026] In an alternative embodiment, the core network CN 1  is engaged in an active call via UDC  13  and then receives a second call request through the same core network (CN n ) to the same mobile station MS 1 . In this embodiment, the same procedure can be employed in that the core network CN 1  pages the mobile station MS 1  with the second call request and the mobile station MS 1  responds to the page indicating its ability to receive the calls simultaneously. In this embodiment, there is the added advantage of the core network node CN 1  not needing to coordinate with existing connections to place the second call since the connection already exists between the core network CN 1  and the mobile station MS 1 .  
     [0027] While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended