JP2015115828A - Base station device and message discard control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology for making it possible to screen and discard a connection request message from user equipment depending on a device load's magnitude, in a base station device in a mobile communication system.SOLUTION: A mobile communication system includes a base station device for communicating with user equipment. The base station device comprises: a determination unit which receives a connection request message for requesting connection with the base station device from the user equipment and determines priority of the connection request message; and a discard control unit which discards a connection request message determined to be a non-priority one by the determination unit when a processing load of the base station device is larger than a predetermined threshold.

Description

  The present invention relates to a technique for reducing a processing load when traffic increases in a base station apparatus eNB in a mobile communication system.

  In a mobile communication system in which a base station apparatus eNB and a user apparatus UE perform radio communication, a call processing signal is discarded due to a device capacity limit of the base station apparatus eNB when, for example, traffic occurs in a burst due to a disaster or an event. There is a possibility that.

  Since it is not desirable as a mobile communication service to cancel the call processing signal of the currently connected user equipment UE, if the call processing load exceeds the capacity of the equipment, the acceptance of new calls can be canceled to cancel the existing call. It is desirable to adopt a method that protects Patent Document 1 is a prior art document that avoids congestion by discarding a signal.

JP 2013-038573 A

  In the mobile communication system compliant with LTE, random access is performed when the user apparatus UE establishes a connection with the base station apparatus eNB by transmission or reception. FIG. 1 shows an outline of a random access procedure in LTE.

First, the user apparatus UE transmits a preamble using PRACH (Physical Random Access Channel) (step 1). When the base station apparatus eNB detects the preamble, the base station apparatus eNB transmits a RACH response (RACH response) message as a response (step 2). The user apparatus UE that has received the RACH response message transmits an RRC connection request message (step 3). After receiving the RRC connection request message, the base station apparatus eNB transmits an RRC connection setup message including cell setting information for establishing a connection (step 4). The user apparatus UE whose own UE-ID was included in the RRC connection setup message establishes a connection. FIG. 1 shows up to the RRC connection procedure.
The RRC connection request message that is the third message is called RACH message 3. Here, the resources of the base station apparatus eNB are secured for call connection after the RACH message 3 is detected.

  Therefore, when discarding a new call in order to reduce the processing load of the call processing of the base station apparatus eNB when traffic increases, the RACH message 3 immediately before securing the device resource is discarded and the subsequent call processing is performed. Desirably not.

Here, the call handled by the mobile communication system includes an emergency call or a priority call in addition to a call used for a normal call or the like. However, if the RACH message 3 is discarded uniformly in order to reduce the processing load on the base station apparatus eNB, the RACH message 3 related to the emergency call / priority call that should not be discarded can also be discarded. There is a problem of having sex.
The present invention has been made in view of the above points, and in a base station apparatus of a mobile communication system, it is possible to select and discard a connection request message from a user apparatus according to the size of the apparatus load. It aims at providing the technology to do.

According to an embodiment of the present invention, a base station apparatus that communicates with a user apparatus in a mobile communication system,
A determination unit that receives a connection request message for requesting connection with the base station device from the user device, and determines the priority of the connection request message;
A base station apparatus comprising: a discard control unit configured to discard a connection request message determined to be non-priority by the determination unit when a processing load in the base station apparatus is greater than a predetermined threshold value Provided.

Further, according to the embodiment of the present invention, there is provided a message discard control method executed by a base station apparatus that communicates with a user apparatus in a mobile communication system,
A determination step of receiving a connection request message for requesting connection with the base station device from the user apparatus, and determining a priority of the connection request message;
A message discard control method comprising: a discard control step for discarding a connection request message determined to be non-priority by the determination step when a processing load in the base station apparatus is larger than a predetermined threshold value Is provided.

  According to the embodiment of the present invention, a technology is provided that enables a base station apparatus of a mobile communication system to select and discard a connection request message from a user apparatus according to the size of the apparatus load. The

It is a figure for demonstrating the outline | summary of random access. It is a figure which shows the example of a RRC connection request message. It is a figure which shows the example of a RRC connection reset request message. 1 is a configuration example of a mobile communication system according to an embodiment of the present invention. It is a functional block diagram of the base station apparatus eNB. It is a functional block diagram of the base station apparatus eNB. It is a flowchart which shows a message priority determination process. It is a figure which shows UL-CCCH-Message. It is a figure which shows the example of a correspondence of Establishment Cause and a bit value. It is a figure for demonstrating the outline | summary of a message discard determination process. It is a figure for demonstrating the outline | summary of a message discard determination process. It is a flowchart which shows a message discard control process.

  Embodiments of the present invention will be described below with reference to the drawings. The embodiment described below is only an example, and the embodiment to which the present invention is applied is not limited to the following embodiment. For example, the mobile communication system according to the present embodiment assumes a system based on LTE, but the present invention is not limited to LTE and can be applied to other systems.

  In the present specification and claims, “LTE” includes not only a communication system corresponding to Release 8 or 9 of 3GPP but also a communication system corresponding to Release 10, 11 or 12 of 3GPP or later. Use in a broad sense.

(Outline of the embodiment)
In the present embodiment, by analyzing (decoding) information in the RRC connection request message (RACH message 3 described above) in the RRC connection procedure, it is determined whether or not the new call related to the RRC connection request message is an emergency call / priority call. Determine whether. When the processing load on the base station apparatus eNB increases, the emergency call / priority call is protected as much as possible, and the RRC connection request message related to other calls is discarded. Note that the RRC connection reset request message transmitted when the RRC connection is broken is also a message requesting a call connection, similar to the RRC connection request message. It is a target for destruction. In the following description, the description of the “RRC connection request message” is basically the same as the “RRC connection reconfiguration request message”. Further, the “RRC connection request message” and the “RRC connection reset request message” may be collectively referred to as “connection request message”. However, the “connection request message” may include other than “RRC connection request message” and “RRC connection reset request message”.

  Here, the RRC connection request message includes a lot of information in addition to the information indicating whether it is an emergency call / priority call, and the base station apparatus eNB performs decoding of the RRC layer (layer 3), and stores these information. Extracting. For reference, FIG. 2 shows an ASN. FIG. 3 shows an ASN.1 in the RRC connection reconfiguration request message. One notation example is shown. Both messages are specified in LTE.

  However, decoding and analyzing the entire RRC connection request message requires a large amount of CPU processing by the base station apparatus eNB. That is, a large amount of processing is required to determine whether to discard a new call, and discarding a new call may not reduce the load on the base station apparatus eNB. Therefore, in the present embodiment, it is determined whether or not the call is an emergency call / priority call by viewing a part of information of layer 2 (eg, MAC layer) data carrying the RRC connection request message, and the RRC layer (layer 3). It is determined whether or not the call is an emergency call / priority call without performing decoding, and a discard determination is performed. As a result, the message discarding process can be performed after determining the emergency call / priority call without increasing the processing load of the base station apparatus eNB. Hereinafter, a connection request message related to an emergency call / priority call is referred to as a “priority message”, and the others are referred to as “non-priority messages”.

(Device configuration example)
FIG. 4 shows a configuration example of the mobile communication system according to the embodiment of the present invention. As shown in FIG. 4, the mobile communication system according to the present embodiment includes a base station apparatus eNB that forms a cell and a user apparatus UE that is located in the cell and performs radio communication with the base station apparatus eNB. In FIG. 4, one base station apparatus eNB and one user apparatus UE are shown, but these are representative and may be plural. In the present embodiment, the mobile communication system can operate at least according to LTE. That is, PHY, MAC, RLC, PDCP, RRC or the like is used as a radio interface protocol, and an RRC connection procedure or the like is executed between the base station apparatus eNB and the user apparatus UE at the time of call connection.

  FIG. 5 shows a functional configuration diagram of the base station apparatus eNB according to the present embodiment. FIG. 5 shows only functions according to the embodiment of the present invention, and the base station apparatus eNB includes functions not shown for realizing communication based on LTE.

  As illustrated in FIG. 5, the base station apparatus eNB according to the present embodiment includes a reception unit 10, a message priority determination unit 11, a message discard control unit 12, and a message processing unit 13. The functional outline of each functional unit is as follows.

  The receiving unit 10 receives a radio signal from the user apparatus UE, acquires layer 2 data (eg, MAC PDU, a header included therein, MAC SDU, and the like), and passes the data to the message priority determination unit 11. Note that “passing” includes, for example, a case where layer 2 data is stored in a memory buffer included in the base station apparatus eNB and a process of reading data from the memory buffer is performed.

  The message priority determination unit 11 determines whether the message carried in the received signal is an RRC connection request message based on the value of a predetermined bit included in the layer 2 data, and is carried in the received signal. If the message is an RRC connection request message, it is determined whether or not it is a priority message. The message priority determination unit 11 passes the layer 2 data corresponding to the RRC connection request message and the determination result of priority / non-priority to the message discard control unit 12, and the layer 2 data other than the connection request message is not subject to discard control. It passes to the processing unit 13.

  The message discard control unit 12 determines whether to discard the RRC connection request message based on the processing load of the base station apparatus eNB and the priority / non-priority determination result. When the message discard control unit 12 determines to discard the RRC connection request message, the message discard control unit 12 discards the layer 2 data corresponding to the RRC connection request message. To pass. The message processing unit 13 performs processing (message decoding or the like) of a layer higher than the layer handled by the message priority determination unit 11.

  FIG. 6 shows a configuration diagram close to an implementation example as another functional configuration diagram of the base station apparatus eNB according to the present embodiment. The base station apparatus eNB shown in FIG. 6 includes an antenna 20 that transmits and receives radio signals, an interface unit 21 connected to the antenna, a baseband processing unit 22, a device control unit 23, and an interface unit 24 connected to the core network. .

  The baseband processing unit 22 performs layer 1 and layer 2 processing. That is, the baseband processing unit 22 performs physical layer, MAC layer, RLC layer, and PDCP layer processing. The baseband processing unit 22 is realized by, for example, a DSP (Digital Signal Processor), but is not limited thereto. The device control unit 23 performs layer 3 or higher processing such as call connection control and monitoring control based on the RRC message.

  In the present embodiment, it is assumed that the message priority determination unit 11 and the message discard control unit 12 in the functional configuration diagram shown in FIG. 5 are included in the baseband processing unit 22 in FIG. It is not limited. The processing by the message priority determination unit 11 and the message discard control unit 12 is performed by the baseband processing unit 22 in FIG. 6, thereby further increasing the processing load of the device control unit 23 that performs a call connection control process with a large processing load. It is possible to determine whether or not to discard the message.

(Device operation example)
Hereinafter, the process regarding the message discarding performed by the base station apparatus eNB according to the present embodiment will be described in more detail. Hereinafter, description will be made based on the configuration of the base station apparatus eNB shown in FIG. In the following, priority / non-priority determination is performed by referring to the MAC data. However, this is an example, and for example, the determination may be performed by referring to other layer 2 data.

  First, message priority determination processing executed by the message priority determination unit 11 of the base station apparatus eNB will be described with reference to the flowchart of FIG.

  The message priority determination unit 11 determines whether or not the value of LCID (Logical channel ID) in each MAC subheader of the MAC data acquired from the reception unit 10 is a value indicating CCCH (common control channel) (step 101). The LCID is an ID indicating a logical channel to which a MAC SDU related to a MAC subheader including the LCID belongs.

  Since the uplink CCCH is used when transmitting the RRC connection request message or the RRC connection reconfiguration request message (see FIG. 8), in this embodiment, when the value of the LCID is a value indicating the CCCH, The message priority determination unit 11 determines that the MAC SDU corresponds to the RRC connection request message or the RRC connection reconfiguration request message, and proceeds to step 102 in FIG. When the value of the LCID is not a value indicating CCCH, the message priority determination unit 11 determines that the MAC SDU corresponds to a message other than the message to be discarded in this embodiment, and this is the message processing unit. 13 (step 103).

  In step 102, the message priority determination unit 11 checks the bit at a predetermined position of the corresponding MAC SDU and checks whether the bit is a predetermined value, so that the MAC SDU receives the RRC connection request message or the RRC connection reconfiguration request message. It is determined which one of them corresponds. In this embodiment, as an example, the value of the second bit from the head of the MAC SDU is examined, and if it is 0, the MAC SDU determines that it corresponds to the RRC connection reconfiguration request message, and proceeds to step 107. Is 1, it is determined that the MAC SDU corresponds to the RRC connection request message, and the process proceeds to step 104.

In step 104, the message priority determination unit 11 checks whether the RRC connection request message is priority or otherwise (non-priority) by checking the bit at the predetermined position of the corresponding MAC SDU and checking whether it is a predetermined value. Determine. In this embodiment, as an example, the setting value of Flag _{CCCH # 1 Priority} corresponding to the 45th to 47th bit values from the head of the MAC SDU is examined. The 45th to 47th bits correspond to “Establishment Cause” in the RRC connection request message, and LTE defines values as shown in FIG.

  In the present embodiment, the message priority determination unit 11 uses the priority message as the RRC connection request message corresponding to the MAC SDU if the value of the 45th to 47th bits from the head of the MAC SDU corresponds to the emergency or priority. It is determined that there is a message (step 105). Otherwise, it is determined that it is a non-priority message that is not a priority message (step 106).

Also in step 107, as described above, the message priority determination unit 11 checks whether the RRC connection reconfiguration request message has priority by checking the bit at a predetermined position of the corresponding MAC SDU and checking whether it is a predetermined value. Determine whether it is other (non-priority). In the present embodiment, as an example, the setting value of Flag _{CCCH # 0} Priority in the corresponding MAC SDU is checked, and if it is a value corresponding to emergency or priority, an RRC connection reconfiguration request message corresponding to the MAC SDU is _displayed as a priority message. It is determined that there is a message (step 108). Otherwise, it is determined that the message is a non-priority message (step 109).

  Next, a processing example of the message discard control unit 12 will be described. 10 and 11 are diagrams for explaining an overview of the message discard control process executed by the message discard control unit 12 in the present embodiment.

In the present embodiment, the base station apparatus eNB counts (increases by 1) the number of connection request messages when receiving a connection request message (RRC connection request message or RRC connection reconfiguration request message). This number is Count _M3 . In addition, an acceptance determination threshold Th _M3low for non-priority messages and a threshold Th _M3 for discarding all messages are set in advance for device protection.

In the present embodiment, when the message discard control unit 12 determines that the connection request message related to the determination target layer 2 data (specifically, the MAC SDU) is accepted (not discarded), Count _{M3 is set} to 1. However, the method for counting connection request messages is not limited to this. The message discard control unit 12 includes a periodic timer that expires at a predetermined time T (seconds), and Count _M3 is reset to 0 each time the timer expires (every T seconds).

  Note that the above count and threshold setting may be performed in units of base station apparatuses eNB or in units of cells managed by the base station apparatus eNB.

As shown in FIG. 10, in this embodiment, the priority message is accepted when Count _M3 ≦ Th _M3 . The non-priority message is _accepted when Count _M3 ≦ Th _M3low . When Th _M3low ≦ Count _M3 ≦ Th _M3 , the priority message is _accepted , but the non-priority message is discarded.

FIG. 11 is a diagram expressing the value of Count _M3 in time series. As shown in FIG. 11, every time the period counter expires, Count _M3 becomes 0, and sequentially increases, and after a time period for accepting only priority calls, all new calls are not accepted. The counter cycle may be determined based on, for example, the number of new calls generated per unit time in the area where the base station apparatus eNB is installed.

An example of the operation of the message discard control unit 12 will be described with reference to the flowchart of FIG. The message discard control unit 12 receives the MAC SDU (determined to correspond to the CCCH) and the priority / non-priority determination result from the message priority determination unit 11. First, the message discard control unit 12 determines whether or not Count _M3 ≦ Th _M3 (step 201). If Count _M3 ≦ Th _{M3, the} MAC SDU is discarded (step 202). That is, the connection request message is discarded. If Count _M3 ≦ Th _M3 , the process proceeds to step 203. In step 203, if the corresponding MAC SDU corresponds to the priority message, the message discard control unit 12 adds 1 to Count _M3 (step 204), and passes the MAC SDU to the message processing unit 13 (step 205). .

In step 203, if the MAC SDU corresponds to the non-priority message, the process proceeds to step 206. In step 206, it is determined whether Count _M3 ≦ Th _M3low . If it is not Count _M3 ≦ Th _M3low , the message discard control unit 12 discards the MAC SDU (step 207). If Count _M3 ≦ Th _M3low , the message discard control unit 12 adds 1 to Count _M3 (step 208), and passes the MAC SDU to the message processing unit 13 (step 209).

  In the above example, the processing load is determined by the number of received messages, but the processing load may be determined by another index. For example, the processing load may be determined based on the CPU usage rate of the device control unit 23 in the base station device eNB illustrated in FIG.

  In this embodiment, the connection request message is classified into priority or non-priority, but more priority stages may be provided. However, even when more priorities are provided, for example, the highest priority can be regarded as “priority” and the others can be regarded as “non-priority”. included. That is, “non-priority” includes low priority and the like in meaning.

(Summary of the embodiment, effects, etc.)
As described above, according to the present embodiment, a base station apparatus that communicates with a user apparatus in a mobile communication system, the connection request message for requesting a connection with the base station apparatus from the user apparatus. A determination unit that receives and determines the priority of the connection request message, and discards the connection request message determined to be non-priority by the determination unit when the processing load in the base station apparatus is greater than a predetermined threshold There is provided a base station apparatus including a discard control unit.

  With this base station apparatus, the base station apparatus can select and discard the connection request message from the user apparatus according to the size of the apparatus load. In the above configuration, receiving a connection request message includes receiving a lower layer signal carrying the connection request message.

  The determination unit determines the priority of the connection request message based on a value of a predetermined bit in the layer 2 data carrying the connection request message.

  In this way, by determining the priority at the layer 2 processing stage with a relatively low processing load, the priority determination can be performed before performing the layer 3 decoding with a high processing load, which greatly increases the processing load. Message discard control can be performed without any problem.

  The discard control unit counts the number of connection request messages received without discarding as the processing load value. The connection request message received without discarding in the determination at the layer 2 processing stage (for example, a message placed in the MAC SDU) increases the device load in the subsequent layer 3 processing, so the connection accepted without discarding By using the number of request messages as the processing load, it is possible to appropriately determine the processing load.

  The base station apparatus includes a baseband processing unit that performs processing of layer 1 and layer 2, and a device control unit that performs processing of layers of layer 3 and higher, wherein the baseband processing unit includes the determination unit and the determination unit A discard control unit is included.

  With this configuration, priority determination and discard control can be performed before layer 3 decoding with a high processing load is performed, and message discard control can be performed without greatly increasing the processing load. It becomes.

  Although the embodiments of the present invention have been described above, the disclosed invention is not limited to such embodiments, and those skilled in the art will understand various variations, modifications, alternatives, substitutions, and the like. Will. Although specific numerical examples have been described in order to facilitate understanding of the invention, these numerical values are merely examples and any appropriate values may be used unless otherwise specified. The classification of items in the above description is not essential to the present invention, and the items described in two or more items may be used in combination as necessary, or the items described in one item may be used in different items. It may be applied to the matters described in (if not inconsistent). The boundaries between functional units or processing units in the functional block diagram do not necessarily correspond to physical component boundaries. The operations of a plurality of functional units may be physically performed by one component, or the operations of one functional unit may be physically performed by a plurality of components. For convenience of explanation, the base station apparatus has been described using a functional block diagram, but such an apparatus may be realized by hardware, software, or a combination thereof. Software that executes an operation corresponding to the processing described in the embodiment of the present invention (executed by a processor included in the base station apparatus) is a random access memory (RAM), a flash memory, a read-only memory (ROM), or an EPROM. , EEPROM, register, hard disk (HDD), removable disk, CD-ROM, database, server, or any other suitable storage medium. The present invention is not limited to the above embodiments, and various modifications, modifications, alternatives, substitutions, and the like are included in the present invention without departing from the spirit of the present invention.

UE user apparatus eNB base station apparatus 10 receiving unit 11 message priority determination unit 12 message discard control unit 13 message processing unit 20 antenna 21, 24 interface unit 22 baseband processing unit 23 device control unit

Claims (7)

A base station apparatus that communicates with a user apparatus in a mobile communication system,
A determination unit that receives a connection request message for requesting connection with the base station device from the user device, and determines the priority of the connection request message;
A base station apparatus comprising: a discard control unit that discards a connection request message determined to be non-prioritized by the determination unit when a processing load in the base station apparatus is greater than a predetermined threshold. The base station apparatus according to claim 1, wherein the determination unit determines a priority of the connection request message based on a value of a predetermined bit in layer 2 data carrying the connection request message. The base station apparatus according to claim 1 or 2, wherein the discard control unit counts the number of connection request messages received without discarding as the value of the processing load. The base station apparatus includes a baseband processing unit that performs processing of layer 1 and layer 2, and a device control unit that performs processing of layers of layer 3 and higher, wherein the baseband processing unit includes the determination unit and the determination unit The base station apparatus according to claim 1, further comprising a discard control unit. A message discard control method executed by a base station apparatus that communicates with a user apparatus in a mobile communication system,
A determination step of receiving a connection request message for requesting connection with the base station device from the user apparatus, and determining a priority of the connection request message;
A message discard control method comprising: a discard control step of discarding a connection request message determined to be non-priority by the determination step when a processing load in the base station apparatus is larger than a predetermined threshold value . The said base station apparatus determines the priority of the said connection request message based on the value of the predetermined | prescribed bit in the layer 2 data which carries the said connection request message in the said determination step. Message discard control method. The message discard control method according to claim 5 or 6, wherein, in the discard control step, the base station apparatus counts the number of connection request messages accepted without discarding as the value of the processing load. .

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