Abstract:
An object of the present invention is to provide efficient RFN timing passing between a User Plane Server (UPS) and Radio Control Server (RCS). In a radio base station control system that controls a radio base station device communicating with a mobile terminal over a radio link and includes an RCS performing signaling transfer control and a UPS performing user data transfer control relating to the terminal, the RCS and UPS being provided physically separated from each other, the RCS includes inquiry means for sending an inquiry signal for inquiring about timing information of the UPS, the timing information being required for signaling transfer control and being managed by the UPS; and the UPS includes sending means for sending the RFN to the RCS when the UPS receives the inquiry signal.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a mobile communications system and method that control a radio base station controllers sending and receiving a radio signal to and from mobile terminals.  
           [0003]    2. Description of the Related Art  
           [0004]    A radio access network (RAN) in a mobile communications system consists of radio base stations and base station control devices that control the base stations.  
           [0005]    A RAN based on 3GPP (3rd Generation Partnership Projects) specification is called a UMTS Terrestrial Radio Access Network (UTRAN) and includes a number of radio base stations (Node B)  501 - 504  and a Radio Network Controller (RNC)  505  as shown in FIG. 1. RNC  505  handles signaling control information relating to radio access as well as handling user data such as audio and video. A Control Plane (C-plane) provides signaling transfer control, and a User Plane (U-plane) handles user data such as audio and video data.  
           [0006]    In recent years, an approach has been proposed that divides the C-plane and the U-plane in an RNC and provides a number of U-planes for each C-plane. In the following description, a C-plane section is called an RCS (Radio Control Server) and a U-plane section is called a UPS (User Plane Server).  
           [0007]    [0007]FIG. 2 is a block diagram showing a configuration of such a mobile communication system. Included in the system are UPS  609  provided for radio base stations (Node B)  601 - 604 , UPS  610  provided for radio base stations (Node B)  605 - 608 , and one RCS  611  provided for UPS  609  and UPS  610 .  
           [0008]    In the UTRAN described above, an RNC frame number (RFN), Node B frame number (BFN), a cell system frame number (SFN), and a connection frame number (CFN) are provided as timing information. FIG. 3 shows the relationships between these items of timing information. The items of timing information are defined as follows:  
           [0009]    (1) The RNC uses RFN as timing reference and Node B uses BFN as its timing reference.  
           [0010]    (2) RFN and BFN have a frame length of 10 ms and are controlled with a cycle length of 4096 frames, in the range from 0 to 4095 frames.  
           [0011]    (3) The phase difference between RFN and BFN can be measured by a mechanism called Node Synchronization.  
           [0012]    (4) The frame numbers indicating timing of a cell under the control of Node B is called SFN. The output timing of each cell is determined by an offset relative to BFN called Tcell.  
           [0013]    (5) A user equipment (UE) such as a mobile phone that is in communication in a cell is also communicating with the UTRAN by using CFN. The timing of CFN is determined by a frame offset relative to SFN and a chip offset.  
           [0014]    Details of the architecture described above are specified in 3GPP (3rd Generation Partnership Projects).  
           [0015]    The Tcell, frame offset, chip offset for associating the items of timing information described above are values specified by the RNC and the phase difference between RFN and BFN can be measured by Node Synchronization. Accordingly, all of these values are held by the RNC.  
           [0016]    The RNC must know the CFN defined for each UE in order to indicate the timing to the UE. For example, CFN is used to specify activation time at which the encription function of user information flying over the radio is activated and start time at which Radio link Reconfiguration is performed for configuring a radio link.  
           [0017]    CFN of each UE can be obtained by calculating the offsets (Tcell, frame offset, chip offset, and the phase difference between RFN and BFN) described from RFN timing of the RNC. In particular, BFN timing can be obtained from RFN timing, SFN timing can be obtained from the BFN timing, and CFN timing of each UE can be obtained from the SFN timing.  
           [0018]    In a configuration in which a single radio network controller controls a number of radio base stations as shown in FIG. 1, the radio network controller controls these timings. Therefore, the calculation of the CFN timing of each individual UE on the basis of RFN timing as described above can be calculated by the single radio network controller. In contrast, in a configuration in which a radio network controller is made up of an RCS and a UPS, RFN timing is controlled in the UPS as shown in FIG. 2. Therefore, the RCS must in some way know the RFN timing managed in the UPS. However, no protocol for how an RCS gets to know RFN timing managed in a UPS.  
         SUMMARY OF THE INVENTION  
         [0019]    The present invention has been made in light of the problem with the related art and an object of the present invention is to provide a system and method that allow RFN timing to be passed efficiently between a user plane server (UPS) and a radio control server (RCS).  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    [0020]FIG. 1 shows a network configuration according to the background art.  
         [0021]    [0021]FIG. 2 shows a network configuration according to the background art;  
         [0022]    [0022]FIG. 3 shows a relationship between items of timing information in a UTRAN;  
         [0023]    [0023]FIG. 4( a ) shows a configuration of a relevant part of a first embodiment of the present invention and FIG. 4( b ) shows a configuration of a relevant part of a second embodiment of the present invention;  
         [0024]    [0024]FIG. 5( a ) shows a configuration of a relevant part of a third embodiment of the present invention and FIG. 5( b ) shows a configuration of a relevant part of a fourth embodiment of the present invention;  
         [0025]    [0025]FIG. 6 shows a configuration of a relevant part of a fifth embodiment of the present invention;  
         [0026]    [0026]FIG. 7 shows a configuration of a relevant part of a sixth embodiment of the present invention; and 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]    Embodiments of the present invention will be described below with reference to the accompanying drawings.  
         [0028]    [0028]FIG. 4( a ) is a block diagram showing a configuration of a relevant part of a first embodiment of the present invention. The embodiment shown in FIG. 4( a ) comprises an RCS  101 , which is a first control means, and a UPS  102 , which is a second control means. The RCS  101  comprises an RCS processing unit  103  that performs processing required for functioning as an RCS and an RFN value inquiry unit  104 . The UPS  102  comprises a UPS processing unit  106  that performs processing required for functioning as a UPS and an RFN value notification unit  105 .  
         [0029]    Among items of timing information, Tcell, frame offsets, and chip offsets are specified by the RCS processing unit  103 . RFN timing is managed by the UPS processing unit  106 . The RCS processing unit  103  inquires about an RFN value through the RFN value inquiry unit  104  to the UPS  102  when the RCS processing unit  103  requires RFN timing. The inquiry is received at the RFN value notification unit  105 . The RFN value notification unit  105  reads the RFN timing from the UPS processing unit  106  and sends it to the RCS  101 . It sends the phase difference between RFN and BFN obtained by the UPS processing unit  106  from the result of Node synchronization to the RCS  101  along with the RFN timing. The RCS processing unit  103  receives these signals through the RFN value inquiry unit  104  and performs appropriate processing.  
         [0030]    In the first embodiment configured as described above, communication relating to an RFN value is performed between the RCS  101  and the UPS  102  only when the RCS processing unit  103  required RFN timing. Consequently, the efficiency of communication between them is improved.  
         [0031]    A second embodiment of the present invention will be described below with reference to FIG. 4( b ).  
         [0032]    In the second embodiment, an RFN value correction unit  107  is added to the RCS  101  described with respect to the first embodiment as shown in FIG. 4( a ). The other components of the configuration are the same as those shown in FIG. 4( a ), and are therefore labeled with the same reference numerals and the description of which will be omitted here.  
         [0033]    In the second embodiment, RFN timing sent from the UPS  102  is sent to the RFN value correction unit  107 , where it is corrected. The correction is performed in order to compensate for a propagation delay between the RCS  101  and the UPS  102 .  
         [0034]    The second embodiment configured as described above has, in addition to the advantage of the first embodiment, the advantage that control is provided through the use of a more precise RFN value.  
         [0035]    A third embodiment of the present invention will be described below with reference to FIG. 5( a ), which shows a configuration thereof.  
         [0036]    The embodiment shown in FIG. 5( a ) comprises an RCS  201  and a UPS  202 . The RCS  201  comprises an RCS processing unit  203  which performs processing required for functioning as an RCS and an RFN value receiving unit  204 . The UPS  202  comprises a UPS processing unit  206  which performs processing required for functioning as a UPS and an RFN value notification unit  205 .  
         [0037]    Among items of timing information, Tcell, frame offsets, and chip offsets are specified by the RCS processing unit  203 . RFN timing is managed by the UPS processing unit  206 . The RFN value notification unit  205  periodically reads RFN timing from the UPS processing unit  206  and sends it to the RCS  201 . It sends the phase difference between RFN and BFN obtained by the UPS processing unit  206  from the result of Node synchronization to the RCS  201  along with the RFN timing. The RCS processing unit  203  receives these signals through the RFN value receiving unit  204  and performs appropriate processing.  
         [0038]    In the third embodiment configured as described above, RFN timing is periodically sent to the RCS, unlike in the first and second embodiments. Consequently, the need for the RCS processing unit  203  to inquire about RFN timing is eliminated and therefore the communication control arrangement can be simplified.  
         [0039]    A fourth embodiment of the present invention will be described below with reference to FIG. 5( b ), which shows a configuration thereof.  
         [0040]    In the fourth embodiment, an RFN value correction unit  207  is added to the RCS  201  described with respect to the third embodiment. The other components of the configuration are the same as those shown in FIG. 5( a ), and are therefore labeled with the same reference numerals and the description of which will be omitted here.  
         [0041]    In the fourth embodiment, RFN timing sent from the UPS  102  is sent to the RFN value correction unit  207 , where it is corrected. The correction is performed in order to compensate for a propagation delay between the RCS  201  and the UPS  202 .  
         [0042]    The fourth embodiment configured as described above has, in addition to the advantage of the third embodiment, the advantage that control is provided through the use of a more precise RFN value.  
         [0043]    A fifth embodiment of the present invention will be described with reference to FIG. 6, which shows a configuration thereof.  
         [0044]    The fifth embodiment comprises time information sending means  301 , which sends information indicating a time to an RCS  302  and a UPS  308 .  
         [0045]    The RCS  302  comprises an RCS processing unit  306  which performs processing required for functioning as an RCS, an RFN value inquiry unit  307 , a time information receiving unit  303  which receives time information from the time information sending means  301 , a clock  305 , and a clock control unit  304  which adjusts the time of clock  305  to time information received at the time information receiving unit  303 .  
         [0046]    The UPS  308  comprises a UPS processing unit  309  which performs processing required for functioning as a UPS, an RFN value notification unit  313 , a time information receiving unit  310  which receives time information from the time information sending means  301 , a clock  312 , and a clock control unit  311  which adjusts the time of the clock  312  to time information received at the time information receiving unit  310 .  
         [0047]    Among items of timing information, Tcell, frame offsets, and chip offsets are specified by the RCS processing unit  306 . RFN timing is managed by the UPS processing unit  309 . The RCS processing unit  306  inquires about an RFN value through the RFN value inquiry unit  307  to the UPS  308  when the RCS processing unit  306  requires RFN timing. The inquiry is received at the RFN value notification unit  313 . The RFN value notification unit  313  reads the RFN timing from the UPS processing unit  309  and sends it to the RCS  302 . It sends the phase difference between RFN and BFN obtained by the UPS processing unit  309  from the result of Node synchronization to the RCS  302  along with the RFN timing. The RCS processing unit  306  receives these signals through the RFN value inquiry unit  307  and performs appropriate processing.  
         [0048]    The time of the clock  305  built into the RCS  302  and the time of the clock  312  built into the UPS  308  are synchronized with each other through the use of timing information sent from the time information sending means  301 . Time information from the clock  312  is added to information sent from the UPS  308  to the RCS  302 . The RCS processing unit  306  calculates an RFN value from the information it received and time information from the clock  305  and the UPS  308  and performs processing.  
         [0049]    Methods for calculating an RFN value when information is sent and received according to the present invention will be described below.  
         [0050]    Method 1: Reporting Phase Difference  
         [0051]    The UPS processing unit  309  and the RCS processing unit  306  use the same method to calculate a frame number from the clock  312  and  305  in the UPS  308  and the RCS  302 , respectively, (hereinafter referred to as an own-clock frame number) in a 4096 frame period with a 10-ms interval.  
         [0052]    Because the clock  312  provided in the UPS  308  and the clock  305  provided in the RCS  302  are synchronized with each other, the own-clock frame numbers calculated will be virtually the same. An example of a formula is shown below.  
         Own-clock frame number of UPS  308 , RCS  302 =(current time expressed in 10 ms) mod 4096  
         [0053]    The UPS processing unit  309  indicates the following phase difference between an RFN value and a UPS own-clock frame number that it controls to the RCS  302 .  
         Phase difference=(RFN−UPS own-clock frame number) mod 4096  
         [0054]    The RCS processing unit  306  uses the phase difference value received from the UPS  308  to obtain the RFN value at the current time by the following calculation:  
         RFN value=(RCS own-clock frame number+phase difference) mod 4096  
         [0055]    The RFN value obtained by the RCS processing unit  306  varies depending on the precision of the clocks  312  and  305  in the UPS  308  and the RCS  302  to which it synchronizes. However, the precision of the RFN value required by the RCS processing unit  306  is low compared with the one required by the UPS processing unit  309  and therefore synchronization with an acceptable error will suffice. Typically, an error of several frames is acceptable.  
         [0056]    Method 2: Reporting Current RFN Value  
         [0057]    The UPS processing unit  309  and the RCS processing unit  306  use the same method to calculate an own-clock frame number from the clock  312  and  305  in the UPS  308  and the RCS  302 , respectively, in a 4096 frame period with a 10-ms interval.  
         [0058]    Because the clock  312  provided in the UPS  308  and the clock  305  provided in the RCS  302  are synchronized with each other, the own-clock frame numbers calculated will be virtually the same. An example of a formula used is shown in below.  
         Own-clock frame number of UPS  308 , RCS  302 −(current time expressed in 10 ms) mod 4096  
         [0059]    The UPS processing unit  309  indicates the correspondence between an RFN value and a UPS own-clock value it controls to the RCS  302 : (RFN, UPS own-clock time)  
         [0060]    The RCS processing unit  306  calculates the RFN value at the current time from the correspondence between the RFN value and the UPS own-clock value received from the UPS  308 .  
         [0061]    For example, the RFN value can be calculated as follows:  
         RFN (UPS)=RFN value received from UPS  
         TIME (UPS)=UPS own-clock time (in 10 ms)  
         TIME (RCS)=RCS own-clock current time (in 10 ms)  
         RFN value=[RFN (UPS)+[TIME (RCS)−TIME (UPS)]] mod 4096  
         [0062]    The RFN value obtained by the RCS processing unit  306  varies depending on the precision of the clocks to which the UPS and RCS synchronizes. However, the precision of the RFN value required by the RCS is low compared with the one required by the UPS and therefore synchronization with an acceptable error will suffice. Typically, an error of several frames is acceptable.  
         [0063]    A sixth embodiment of the present invention will be described with reference to FIG. 7, which shows a configuration thereof.  
         [0064]    Time information sending means  401 , an RCS  402 , time information receiving units  403 ,  410 , clock controlling units  404 ,  411 , clocks  405 ,  412 , a UPS  408 , an RCS processing unit  406 , and a UPS processing unit  409  in the sixth embodiment are the same as the time information sending means  301 , RCS  302 , time information receiving units  303 ,  310 , clock control units  304 ,  311 , clocks  305 ,  312 , UPS  308 , RCS processing unit  306 , and UPS processing unit  309  in the fifth embodiment shown in FIG. 6.  
         [0065]    Among items of timing information in the sixth embodiment, Tcell, frame offsets, and chip offsets are values specified by the RCS processing unit  460 . RFN timing is managed by the UPS processing unit  409 . The RFN value notification unit  413  reads RFN timing from the UPS processing unit  409  and sends it to the RCS  402 . It sends the phase difference between RFN and BFN obtained by the UPS processing unit  406  from the result of Node synchronization to the RCS  402  along with the RFN timing. The RCS processing unit  406  receives these signals through the RFN value receiving unit  407  and performs appropriate processing.  
         [0066]    Also in the sixth embodiment, the time of the clocks  405  built in the RCS  402  and the time of the clock  412  built in the UPS  412  are synchronized with each other through the use of time information sent from the time information sending means  401 . Time information from the clock  412  is added to information sent from the UPS  408  to the RCS  402 . The RCS processing unit  406  calculates an RFN value from the information it received and time information from the clock  405  and performs processing.  
         [0067]    The calculation of the RFN value is accomplished according to the method 1 or 2 in the fifth embodiment shown in FIG. 6.  
         [0068]    While the UPS  408  periodically sends notification of a phase difference to the RCS  402  in the embodiment, it may send notification to the RCS  402  only when a change occurs in the phase difference. This arrangement allows the RCS  402  to always know an RFN value managed by the UPS  408 .  
         [0069]    In a method in which the UPS simply sends the current RFN value to the RCS as in the first and third embodiments, fluctuations in propagation delay and processing delay may have to be accommodated, depending on the communication distance or propergation delay. While a correction circuit is provided for correcting such fluctuations in the second and fourth embodiments, complicated correction is involved.  
         [0070]    In the fifth and sixth embodiment configured as described above, a propagation delay between the RCS and UPS presents no problem and therefore a correction circuit as in the second and fourth embodiments is not required.  
         [0071]    Time information sending means for synchronizing the clocks built in a UPS and RCS may be GPS (Global Positioning System), NTP (Network Time Protocol), standard time broadcast used for radio wave clocks, FM broadcast, or any other means. Furthermore, time synchronization that can substitute as clocks may be used in place of the clocks.  
         [0072]    GPS can globally provide time synchronization in a wide range with a very small error by using satellites. The error range of GPS-based time synchronization is approximately 100 ns. However, GPS can be used only in an environment in which radio waves from the satellites can be received.  
         [0073]    NTP is used to synchronize the time of a device to an NTP server in an internet-based network. It can provide clock synchronization with consideration given to propagation delays in information transmission.  
         [0074]    Standard time broadcast uses long or short waves to indicate a time. An advantage of the standard time broadcast is that an error in an indicated time is small. A problem with the standard time broadcast is that an error due to propagation time affects synchronization. However, an error can be corrected from the distance between the position at which a radio wave is emitted and the position at which a UPS or RCS is located.  
         [0075]    FM-broadcast-based time synchronization uses time information broadcasted from an FM radio station to provide time synchronization. It can provide synchronization with precisions ranging from 10 ms to 30 ms.  
         [0076]    Using any of these technologies, clocks built in a UPS and RCS are synchronized with each other, the UPS can indicate the correspondence between an RFN value and a built-in clock to the RCS, and the RCS can indirectly know the RFN value as the correspondence to the clock built in the RCS. It is not necessarily required that the clocks be synchronized directly to the RFN of the UPS. Preferably the buit-in clocks are completely independent from the RFN value.  
         [0077]    The RFN timing of a UPS and the BFN timing of Node B are required to be highly precise because they directly affect radio frame timing. In contrast, the RCS can know the RFN value of the UPS even if the precision of the built-in clocks of a UPS and RSC is not so high.  
         [0078]    Because the RCS has only to know an RFN value on a frame basis (in 10 ms), precisions of several to several tens ms may be sufficient for most systems. If the RCS is implemented by a personal computer or workstation, then its built-in clock can be used without modification because the RCS does not require a high-precision clock.  
         [0079]    The present invention configured as described above has an advantage that RFN timing can be passed between a UPS and RCS in an efficient manner.  
         [0080]    If a correction circuit is added, highly precise RFN value passing can be achieved.  
         [0081]    Furthermore, if time information sending means is provided, highly precise RFN value passing can be achieved with a simple configuration.