Source: http://www.google.com/patents/US20040009773?dq=456322
Timestamp: 2015-01-31 16:47:21
Document Index: 452806931

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Patent US20040009773 - Mobile communication system and operation control method thereof - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsIn a W-CDMA communication system, even the RNC goes into the congestion state due to increasing user data, the RNC may distribute loads while continuously performing its processing without causing system down. An ATM network used in a RAN is IP-networked, where a C plane processing device for signaling...http://www.google.com/patents/US20040009773?utm_source=gb-gplus-sharePatent US20040009773 - Mobile communication system and operation control method thereofAdvanced Patent SearchPublication numberUS20040009773 A1Publication typeApplicationApplication numberUS 10/612,949Publication dateJan 15, 2004Filing dateJul 7, 2003Priority dateJul 10, 2002Also published asCN1276607C, CN1471253A, US7113480Publication number10612949, 612949, US 2004/0009773 A1, US 2004/009773 A1, US 20040009773 A1, US 20040009773A1, US 2004009773 A1, US 2004009773A1, US-A1-20040009773, US-A1-2004009773, US2004/0009773A1, US2004/009773A1, US20040009773 A1, US20040009773A1, US2004009773 A1, US2004009773A1InventorsHidenori KatoOriginal AssigneeNec CorporationExport CitationBiBTeX, EndNote, RefManReferenced by (14), Classifications (25), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetMobile communication system and operation control method thereofUS 20040009773 A1Abstract In a W-CDMA communication system, even the RNC goes into the congestion state due to increasing user data, the RNC may distribute loads while continuously performing its processing without causing system down. An ATM network used in a RAN is IP-networked, where a C plane processing device for signaling processing and a U plane processing device for user data processing are provided in a physically separated manner. With the U plane processing device, a backup system is prepared independently from an active system. When congestion occurs in the active system, part of processing is switched to and inherited by the backup system. Images(19) Claims(14)
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0043] An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram illustrating a constitution of an RNC 4 applied to the embodiment of the present invention. As shown in FIG. 1, the RNC 4 is so constituted that a C plane processing device 41, which is equivalent to a processing function part responsible for a C plane for controlling signaling, and a U plane processing device 42, which is equivalent to a processing function part responsible for a U plane for transfer of user data, are separated from each other. [0044] More specifically, the C plane processing device 41 has a function of generating and terminating an RRC massage in Layer 3 of an RRC layer 13, and the U plane processing device 42 has functions for which layer 2 of a MAC layer 121 and an RLC layer 122 are responsible. An RRC signaling between a mobile unit (UE) 2 and the RNC 4 is transferred to the RRC layer 13 in the C plane processing device 41 positioned as an upper layer after the use of the functions offered by the MAC layer 121 and the RLC layer 122 in the U plane processing device 42. [0045] Accordingly, in the existing RNC protocol architecture shown in FIG. 19, the physical layer (PHY) 11 denoted as Layer 1, the data link layer 12 denoted as Layer 2, and the network layer 13 denoted as Layer 3 are separated into a Node B (radio base station) 6, the U plane processing device 42, and the C plane processing device 41, respectively. In FIG. 1, the connectivity between the MAC layer 121 and the RLC layer 122 is the same as in the example of FIG. 19, so is omitted. [0046] The RRC layer 13 in the C plane processing device 41 controls the physical layer 11 in the Node B, and the MAC layer 121 and the RLC layer 122 in the U plane processing device 42, by using a C-SAP (Control Service Access Point) that provides a control channel. A signaling between the RNC 4 and each of a MSC (Mobile Switching Center) 31 and a SGSN (Serving GPRS (Global Packet Radio Service) Switching Node) 32 is terminated for processing in the C plane processing device 41. [0047] The MSC 31 has a line switching function and the SGSN 32 has a packet switching function, both of which are included in the core network (CN) 3 shown in FIG. 18. User information is transferred via the U plane processing device 42 between the mobile unit (UE) 2 and each of the MSC 31 and SGSN 32. [0048] The constitution of the device shown in FIG. 1 makes it possible to configure a system with high scalability. That is, only the C plane processing device 41 may be added to enhance signaling processing capability, and only the U plane processing device 42 may be added to increase transfer speed of user data. In addition, every device having each function in the U plane processing device 42 has no relation with each other and is controlled by the RRC 13 in the C plane processing device 41, which thus enables the implementation as an independent device. [0049]FIG. 2 is a schematic system diagram in the embodiment of the present invention. Referring to FIG. 2, the RAN (radio access network) is IP-networked, where an IP address is assigned in advance to each device described in the following. Both U plane processing devices 42 a and 42 b operate as an active system, and in subordination thereto, a plurality of Node B6 a to 6 d are connected. [0050] As a backup for the active U plane processing devices 42 a and 42 b, which is used in the case of congestion, another U plane processing device 42 c is provided. Besides, the C plane processing device 41 is provided in the upper position of these U plane processing devices 42 a to 42 c, and each of these devices are connected via a router 5 to the core network (CN) 3 operating as a host system. [0051] The backup U plane processing device 42 c monitors, in a normal state, control signals for signaling transfered between the active U plane processing device 42 a and the C plane processing device 41, and user data transfered between the U plane processing device 42 a and the core network 3. When the processing of the active U plane processing device 42 a goes into the congestion state, part of the processing of the U plane processing device 42 a is inherited by the backup U plane processing device 42 c in order to distribute loads of the U plane processing device 42 a. Also when the congestion occurs on processing in the other active U plane processing device 42 b, part of the processing of the U plane processing device 42 c is inherited by the backup U plane processing device 42 c. The part of the processing means some of a plurality of calls (call unit) currently being connected. [0052]FIG. 3 is a schematic functional block diagram of the active U plane processing device 42 a, and FIG. 4 is a schematic functional block diagram of the backup U plane processing device 42 c. Referring to FIG. 3, the active U plane processing device 42 a comprises an ATM/IP-IF (interface) part 71, a Layer 2 processing part 72, and an APL (application part) 73. The ATM/IP-IF part 71 has a function of converting a data packet transmitted between an IP network involving the radio access network (RAN) 1 and an ATM network involving the Node B6 a to 6 d corresponding to the physical layer composing a lower protocol layer (Layer 1). [0053] More specifically, the ATM/IP-IF part 71 has a function of converting ATM packets input from the Node B to IP packets to transfer them to the Layer 2 processing part 72 or the router 5, and a function of also converting IP packets input from the Layer 2 processing part 72 or the router 5 to ATM packets to transfer them to the Node B, and further has a function of switching a transfer destination of IP packets to either the Layer 2 processing part 72 or the backup U plane processing device 42 c in accordance with directions from the APL part 73. [0054]FIG. 5 is an image diagram showing an example of data conversion between the ATM packets and IP packet. Fixed length of multiple packets (cell) is transmitted in the ATM network, and a variable length packet is transmitted in the IP network. Therefore, when the ATM packets are converted to the IP packet, multiple payloads on the ATM packets are integrated together, and thereafter an IP header is added thereto, as shown in FIG. 5. Contrary to this, when the IP packet is converted to the ATM packets, a payload portion on the IP packet is divided in the fixed length, and thereafter an ATM header is added to each packet. [0055] At this time, the ATM/IP-IF part 71 holds in advance as internal data, a table for converting ATM header information (ATM address of VPI, VCI, etc.) to IP header information (IP address) or vice versa. [0056] The Layer 2 processing part 72 has a function of performing protocol processing of the MAC layer 121 and the RLC layer 122 shown in FIG. 1 for signals from the ATM/IP-IF part 71, and then outputting to the ATM/IP-IF part 71. The APL part 73 has a function of managing each lower protocol, a function of detecting congestion, a function of directing the ATM/IP-IF part 71 to switch a transmission/reception destination of control signals and user data to the backup U plane processing device 42 c when detecting the congestion, and a function of notifying the backup U plane processing device 42 c of information about calls (hereinafter referred to as call information) necessary for call processing to be inherited when detecting the congestion, the call information which is held by each protocol for every call, every cell, and every Node B. [0057] Each function of the APL part 73 is executed by an application program, which means that these functions are realized by making the CPU read and execute this application program. FIG. 6 shows these functions by a functional block. That is, the APL part 73 includes a lower protocol management part 731, a congestion detection part 732, a congestion state control part 733 for controlling as described above at the time of congestion, a memory 734 for storing programs, data, and the like, a control part 735 for controlling these parts, and a bus 736 for connecting these parts. [0058] The backup U plane processing part 42 c comprises an IP-IF part 81, a Layer 2 processing part 82, and an APL part 83 as shown in FIG. 4. The IP-IF part 81 has a function of transferring signals received from the ATM/IP-IF part 71, the C plane processing device 41, and the core network 3 to the Layer 2 processing part 82, according to the direction from the APL part 83 during the congestion, a function of also transferring signals received from the Layer 2 processing part 82 to the ATM/IP-IF part 71, the C plane processing device 41, and the core network 3, and further has a function of monitoring control signals and user data transmitted between the U plane processing device 42 a and the C plane processing device 41, and between the U plane processing device 42 a and the core network 3. [0059] The Layer 2 processing part 82 has the same function as that of the Layer 2 processing part 72 in the active U plane processing device 42 a shown in FIG. 3. The APL part 83 has a function of managing lower protocols, a function of receiving a switching request of processing directed from the U plane processing device 42 a and the call information held by each protocol, and a function of developing the received and inherited information of each protocol in the lower protocols. [0060] Each function of the APL part 83 is executed by an application program similarly to the APL part 73 in FIG. 3, and is indicated by a functional block as shown in FIG. 7. That is, the APL part 83 includes a lower protocol management part 831, a receiving part 832 for receiving the switching request and information inherited from the U plane processing device 42 a, an inherited information developing part 833 for developing the inherited information of each protocol in the lower protocols, a downlink signal transmission destination IP address direction part 834 for directing the C plane processing device 41 and the CN 3 to change the IP address of transmission destination of downlink control signals or user data of calls to be inherited, to an IP address of the backup U plane processing device 42 c, a memory 835 for storing programs, data, and the like, a control part 836 for controlling these parts, and a bus 837 for connecting these parts. [0061] In the following, operations in the embodiment of the present invention will be described. FIG. 8 is a diagram showing a flow of the uplink and downlink control signals (C plane information) when the active U plane processing device 42 a is not in the congestion state but in the normal state, and indicates the flow by a dotted line. FIG. 9 is an operational sequence diagram in this case. [0062] Referring to FIGS. 8 and 9, when the processing of the active U plane processing device 42 a is not in the congestion state, the uplink control signal received from the Node B6 a, for example, is converted from the ATM packet to the IP packet in the ATM/IP-IF part 71 (step S1), and is subjected to Layer 2 processing by the Layer 2 processing part 72 (step S2), then transferred to the C plane processing device 41 to be subjected to Layer 3 processing therein (step S3). Finally, it is transmitted to the CN 3. [0063] The downlink control signal is transmitted from the CN 3 to the C plane processing device 41, and is subjected to the Layer 3 processing (step S4). Then, it is transferred to the U plane processing device 42 a for the Layer 2 processing in the Layer 2 processing part 72 (step S5), and finally transmitted to the Node B6 a after converted from the IP packet to the ATM packet in the ATM/IP-IF part 71 (step S6). At this moment, the backup U plane processing device 42 c monitors the control signals transmitted between the C plane processing device 41 and the U plane processing device 42 a. [0064]FIGS. 10 and 11 show a flow of control signals and an operational sequence, respectively, when the U plane processing device 42 a is in the congestion state. Now, when the processing in the U plane processing device 42 a goes into the congestion state, the congestion detection part 732 in FIG. 6 detects it (step S11), and part of the processing, that is, processing for some calls out of those currently being connected is switched to the backup U plane processing device 42 c, whereupon the switching request to switch the processing from the U plane processing device 42 a to the backup U plane processing device 42 c is generated (step S12), and call information of calls to be inherited, which is held by each protocol, is transferred to the backup U plane processing device 42 c by the congestion state control part 733 (step S13). Simultaneously with this, the control signals are so controlled by the congestion state control part 733 that they may not be transmitted to the upper protocol Layer 2 processing part 72 but may be looped back in the ATM/IP-IF part 71 (step S14). [0065] Next, the backup U plane processing device 42 c having received the switching request of processing from the U plane processing device 42 a inherits the call processing on the basis of information hitherto monitored and the call information transferred in step S13 (step S15). This inheritance is allowed when the inherited information developing part 833 shown in FIG. 7 develops the call information in Layer 2 protocols. [0066] Then, the backup U plane processing device 42 c directs the C plane processing device 41 by the downlink signal transmission destination IP address direction part 834 shown in FIG. 7 to change the transmission destination IP address of the downlink control signal of calls to be inherited from the IP address of the active U plane processing device 42 a to the IP address of the backup U plane processing device 42 c (step S16). Therefore, the C plane processing device 41 has a function of changing the transmission destination IP address of the downlink control signal for every call according to the direction from the backup U plane processing part 42 c. [0067] At this time, the uplink control signal which is transferred from the U plane processing device 42 a undergoes the ATM/IP conversion in the ATM/IP-IF part 71 of the U plane processing device 42 a (step S17) and also the IP address of the IP header part (see FIG. 5) is changed to the IP address of the backup U plane processing device 42 c and transmitted. In accordance with this IP address, the backup U plane processing device 42 c takes in the uplink control signal of takeover processing into the IP-IF part 81 to perform the Layer 2 processing at the Layer 2 processing part 82 (step S18). Then, the uplink control signal is subjected to the Layer 3 processing in the C plane processing device 41 (step S19), and finally transmitted to the CN3. [0068] On the other hand, the downlink control signal from the CN 3 undergoes the Layer 3 processing in the C plane processing device 41 (step S20), and it is transmitted from the C plane processing device 41 with the designated IP address of the backup U plane processing device 42 c in place of the IP address of the active U plane processing device 42 a, so that the backup U plane processing device 42 c takes in the downlink control signal designating the device 42 c by distinguishing the IP address in the IP header of the downlink control signal. [0069] The downlink control signal thus taken in by the backup U plane processing device 42 c undergoes the Layer 2 processing in the Layer 2 processing part 82 (step S21), and then transmitted to the ATM/IP-IF part 71 of the U plane processing device 42 a. In the ATM/IP-IF part 71, the downlink control signal is subjected to the IP/ATM conversion (step S22), and then finally transmitted to the Node B. [0070]FIGS. 12 and 13 show a flow of uplink and downlink user data and an operational sequence, respectively, when the active U plane processing device 42 a is not in the congestion state but in the normal state. When the U plane processing device 42 a is not in the congestion state, the uplink user data received from the Node B6 a is converted from the ATM packet to the IP packet in the ATM/IP-IF part 71 (step S31), and is thereafter subjected to the Layer 2 processing in the Layer 2 processing part 72, and then transferred to the CN 3. [0071] The downlink user data from the CN 3 is transmitted to the U plane processing device 42 a and then subjected to the Layer 2 processing in the Layer 2 processing part 72 (step S33), followed by conversion from the IP packet to the ATM packet in the ATM/IP-IF part 71 (step S34), then finally transmitted to the Node B6 a. At this time, the backup U plane processing device 42 c monitors the user data transmitted between the CN 3 and the U plane processing device 42 a. [0072]FIGS. 14 and 15 show a flow of the uplink and downlink user data and an operational sequence, respectively, when the U plane processing device 42 a goes into the congestion state. When the U plane processing device 42 a goes into the congestion state, similarly to the foregoing example in FIGS. 10 and 11, the congestion is detected (step S41), the switching request is generated to switch the processing to the backup U plane processing device 42 c (step S42), and the call information of calls to be inherited, that is held by each protocol, is transferred to the backup U plane processing device 42 c (step S43). [0073] At the same time of the above, the user data is made not to reach the upper but is made to loop back in the ATM/IP-IF part 71 (step S44). Subsequently, the backup U plane processing device 42 c received the switching request of processing from the U plane processing device 42 a develops the transferred call information in each protocol to thereby inherit the call processing to be inherited (step S45). [0074] The backup U plane processing device 42 c directs the CN 3 by the downlink signal transmission destination IP address direction part 834 to change the transmission destination IP address of the downlink user data of calls to be inherited from the IP address of the active U plane processing device 42 a to the IP address of the device 42 c itself (step S46). Therefore, the CN 3 has a function of changing the transmission destination IP address of the downlink user data for every call in accordance with the direction from the backup U plane processing device 42 c. [0075] At this time, the uplink user data transferred from the U plane processing device 42 a includes the designated IP address of the backup U plane processing device 42 c (the IP address is designated in the ATM/IP-IF part 71) (step S47), so that the backup U plane processing part 42 c takes in this user data and performs the Layer 2 processing thereto (step S48). [0076] On the other hand, the downlink user data from the CN 3 includes the designated IP address of the backup U plane processing device 42 c in place of the IP address of the U plane processing device 42 a, so that the backup U plane processing device 42 c takes in the user data designating the U plane processing device 42 c itself by distinguishing the IP address of the IP header of the downlink user data. [0077] Subsequently, the user data taken in by the U plane processing device 42 c is subjected to the Layer 2 processing (step S49), and is then converted from the IP packet to the ATM packet in the ATM/IP-IF part 71 of the U plane processing device 42 a (step S50), and finally transmitted to the Node B6 a. [0078] In the foregoing embodiment, the ATM/IP-IF is used for an interface with the Node B, however, when an IP interface is eventually used for the interface with the Node B as a result of advanced IP networking of the RAN, the conversion processing between the ATM packet and IP packet is no longer necessary when the active U plane processing device goes into the congestion state and thus switches the processing thereof to the backup U plane processing device, eliminating the necessity of passing through the ATM/IP-IF part 71 of the active U plane processing device 42 a. This allows the backup U plane processing device 42 c to inherit all the processing in the active U plane processing device 42 a, which means that the U plane processing device 42 a may not interrupt services even when causing system down or needing to halt the system in updating and adding files, and all the processing may be inherited to the backup U plane processing device 42 c. [0079] In the foregoing embodiment, it is described the case where, after the active U plane processing device 42 a goes into the congestion state, it is inherited part of a plurality of calls currently being connected (call connection unit) to the backup U plane processing device 42 c, however, there is a conceivable case where, when the mobile unit (UE) brings a new call connection request in a state that the active U plane processing device 42 a is nearly congested, this new call is inherited to the backup U plane processing device 42 c. The operation in this case will be described below referring to FIGS. 16 and 17. [0080] First, the control signal is described with reference to FIG. 16. In the state shown in FIG. 8, when the active U plane processing device 42 a is close to the congestion state and a connection request comes from a new mobile unit to the U plane processing device 42 a, the U plane processing device 42 a reaches the congestion state, and therefore generates the switching request so as to inherit the processing for the connection request to the backup U plane processing device 42 c when detecting the congestion, and further generates a loopback instruction to the ATM/IP-IF part 71, these processing of which are the same as in steps S11, S12, and S14 of FIG. 11. [0081] The backup U plane processing device 42 c having received this request transmits the connection request to the C plane processing device 41 (step S51) as well as notifies the C plane processing device 41 of the IP address of the backup U plane processing device 42 c (step S52). Then, the subsequent processing is the same as the operations in steps S17 to S22 of FIG. 11 and the flow of the control signal shown in FIG. 10, wherein the packets of both the uplink and downlink control signals processed in the backup U plane processing device 42 c hold the designated IP address of the backup U plane processing device 42 c. [0082] Next, user data is described with reference to FIG. 17. In the state shown in FIG. 12, when the active U plane processing device 42 a is close to the congestion state and a connection request comes from a new mobile unit to the U plane processing device 42a, the U plane processing device 42 a reaches the congestion state, and generates the switching request so as to inherit the processing for the connection request to the backup U plane processing device 42 c when detecting the congestion, and further generates the loopback instruction to the ATM/IP-IF part 71, these processing of which are the same as in steps S41, S42, and S44 of FIG. 15. [0083] The backup U plane processing device 42 c having received this request transmits the connection request to the CN 3 (step S61) as well as notifies the CN 3 of the IP address of the backup U plane processing device 42 c (step S62). The subsequent processing is the same as the operations in steps S47 to S50 of FIG. 15 and the flow of the user data shown in FIG. 12, wherein and the packets of both the uplink and downlink user data hold the designated IP address of the backup U plane processing device 42 c. [0084] As described above, in a W-CDMA mobile communication system according to the present invention, even when data communication using notebook-sized personal computers or the use of large amount of data such as images or moving pictures is accelerated and the upsurge of the user data amount is thereby expected, the processing loads in the RAN handling the user data may easily be distributed, and system down of the entire system may effectively be prevented. This is because, when the U plane processing device handling the user data goes into the congestion state, the U plane processing device is able to inherit part of the processing to another backup U plane processing device to thereby continuously perform the processing. 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