JP2015142371A - User device, base station, and frequency selection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology of implementing band dispersion for user device in a mobile communication system.SOLUTION: The mobile communication system includes detection means for detecting a plurality of frequencies of the same priority by cell-searching a user device communicating with a base station, and selection means for selecting a frequency of a cell in which the user device should be located based on conditions other than quality, among the plurality of frequencies.

Description

  The present invention relates to a technique for selecting a cell where a user apparatus is located in a mobile communication system.

  In LTE (including LTE-Advanced), the user apparatus UE is managed in two states, an RRC connected state and an IDLE state, as shown in FIG. The RRC connected state is a state in which connection is established by RRC, and the user apparatus UE can transmit and receive user data. Since the user apparatus UE having data transmits and receives data without delay, it is desirable to maintain the RRC connected state.

  On the other hand, the IDLE state is a state in which connection is not established by RRC, and when the user apparatus UE transmits and receives user data, it is necessary to first establish a connection with the NW. The user apparatus UE that does not have data is preferably in the IDLE state from the viewpoint of battery saving and resources.

3GPP TS 36.304 V11.6.0 (2013-12)

  As described above, it is desirable that the user apparatus UE having no data is in the IDLE state. However, in the current LTE system, the user apparatus UE in the IDLE state is located in the best cell (the cell with the highest quality). When making a call, the best cell is connected.

  If the user apparatus UE to be connected concentrates on a cell in a specific band, there is a possibility that the cell may be congested, and it is desirable to distribute a plurality of user apparatuses UE in different band cells.

  In order to distribute the band of the user apparatus UE in the IDLE state, it is necessary to temporarily connect the user apparatus UE to a cell in which the user apparatus UE is located, and then transition to a band to be distributed by handover (HO). That is, as shown in FIG. 2, the user apparatus UE makes a call (step 1), transitions from IDLE to Active (connected state) (step 2), and then determines the band dispersion (step 3). (Step 4).

  However, when such a step is taken, there is a possibility that the user throughput is lowered because a delay caused by sandwiching the connected state transition procedure and the HO procedure and a delay due to the HO failure occur.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a technique for performing band dispersion of user apparatuses in a mobile communication system.

According to an embodiment of the present invention, a user apparatus that communicates with a base station in a mobile communication system,
Detecting means for detecting a plurality of frequencies having the same priority by performing a cell search;
There is provided a user apparatus comprising: a selecting unit that selects a frequency of a cell in which the user apparatus should be located based on conditions other than quality from the plurality of frequencies.

Moreover, according to the present embodiment, a user apparatus that communicates with a base station in a mobile communication system,
Receiving means for receiving a priority for each frequency from the base station;
When the user apparatus performs transmission, cell search is performed in the order of frequencies based on the priority corresponding to the type of transmission, and the user apparatus is placed in a cell having a frequency satisfying a predetermined quality condition detected by the cell search. There is provided a user apparatus including a visiting area control means for staying in the area.

Moreover, according to the present embodiment, a user apparatus that communicates with a base station in a mobile communication system,
A connection processing means for transmitting a connection request to the base station and receiving a response to the connection request from the base station;
When the response received by the connection processing means includes predetermined information, a cell search is performed for a frequency different from the frequency of the cell in which the user apparatus is located, and the predetermined frequency detected by the cell search is detected. There is provided a user apparatus comprising: a location control unit that causes the user apparatus to be located in a cell having a frequency satisfying a quality condition.

Further, according to the present embodiment, a base station that communicates with a user apparatus in a mobile communication system,
Load determining means for determining a load in a cell formed by the base station;
When a connection request is received from the user apparatus residing in the cell and the load determination unit determines that the load of the cell is equal to or greater than a predetermined threshold, in a response to the connection request, There is provided a base station including connection processing means for transmitting a response including the predetermined information to the user apparatus, including predetermined information for refusing the connection to the cell by the user apparatus.

  According to the embodiment of the present invention, it is possible to provide a technique for performing band distribution of user apparatuses in a mobile communication system.

It is a figure which shows the transition between the Idle state of RRC and the Connected state. It is a figure for demonstrating the present subject. 1 is an overall configuration diagram of a mobile communication system according to an embodiment of the present invention. It is a figure which shows the sequence of the process in 1st Embodiment. It is a figure for demonstrating the conventional cell reselection process. It is a figure for demonstrating the cell reselection process in 1st Embodiment. It is a functional block diagram of the user apparatus UE in 1st Embodiment. It is a flowchart which shows operation | movement of the user apparatus UE in 1st Embodiment. It is a function block diagram of the user apparatus UE in 2nd Embodiment. It is a sequence diagram which shows operation | movement of the user apparatus UE in 2nd Embodiment. It is a sequence diagram which shows the flow of the process in 3rd Embodiment. It is a function block diagram of the base station eNB in 3rd Embodiment. It is a flowchart which shows operation | movement of the base station eNB in 3rd Embodiment. It is a function block diagram of the user apparatus UE in 3rd Embodiment. It is a sequence diagram which shows operation | movement of the user apparatus UE in 3rd Embodiment. It is a figure which shows the example of the table which matched the value (Backoff Parameter value) of the back-off timer, and the index.

  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, although the following embodiment shows an example in which the present invention is applied to an LTE mobile communication system, the present invention can also be applied to mobile communication systems other than LTE. Note that “LTE” is used to mean including LTE-Advanced.

  In the following description, the term “frequency” is mainly used so that “frequency” is selected when the user apparatus UE performs a cell search or the like. This can be paraphrased as “band”, “carrier frequency”, and the like.

(Outline of the embodiment, overall system configuration)
In the present embodiment, band dispersion is performed by causing the user apparatus UE to be located in cells of various frequencies without causing the user apparatus UE to transition to the connected state. That is, by distributing a plurality of user apparatuses UE in the IDLE state to cells of various frequencies, it is possible to avoid delays associated with the connected state transition procedure and the handover procedure (+ handover failure).

  FIG. 3 shows an overall configuration diagram of the mobile communication system according to the embodiment of the present invention. This overall configuration is common to first to third embodiments described later. As illustrated in FIG. 3, the mobile communication system according to the present embodiment includes a base station eNB that forms a cell with carriers of a predetermined frequency, and a user apparatus UE that is located in the cell and communicates with the base station eNB.

  In the example of FIG. 3, the user apparatus UE is located in the serving cell A of the base station eNB. The serving cell A may be referred to as a connected cell. Also, FIG. 3 shows neighboring cells B and C adjacent to the serving cell A. The frequencies in these adjacent cells B and C may be the same as or different from the serving cell A. Also. The RAT (eg, LTE, 3G, etc.) in the neighboring cells B and C may be the same as or different from the serving cell A. An adjacent cell may be referred to as a peripheral cell.

  Hereinafter, first to third embodiments will be described. In 1st Embodiment, in selection of the frequency / RAT in each user apparatus UE, the control that the frequency / RAT which each user apparatus UE selects is distributed is introduce | transduced. In 2nd Embodiment, when the user apparatus UE performs transmission, control that frequency / RAT which each user apparatus UE selects is distributed is introduced. In the third embodiment, the user apparatus UE is connected in the serving cell, but the connection is temporarily rejected and cell reselection is performed without changing to the connected state under the control of the base station eNB.

  In addition, the description of “frequency / RAT” reselects a cell of a different frequency in the RAT or a cell of a RAT different from the RAT when viewed from the user apparatus UE located in a cell of a certain RAT. In the following description, instead of the description of “frequency / RAT”, it is simply described as “frequency”. Such description includes the meanings of both the transition to a different frequency cell and the transition to a different RAT within a certain RAT. Each embodiment will be described below.

(First embodiment)
A user apparatus UE in a mobile communication system defined by LTE selects a cell having a frequency with the best quality (the highest reception strength) in cell selection performed at power-on or the like, and is in the service area. . “To be in a cell” means, for example, receiving a synchronization signal from the base station eNB of the cell to synchronize with the base station eNB and receiving system information (may be called broadcast information) or the like ( Interpretation).

  In this Embodiment, the user apparatus UE residing in a certain cell pays attention to the operation | movement which is residing in the cell of the frequency different from the frequency of the said cell by performing a cell reselection (cell reselection) process. . In other words, cell reselection includes selecting a cell having a frequency different from that of the cell in which the cell is located, and selecting another cell having the same frequency as the cell being located. In the embodiment, attention is paid to cell reselection to a different frequency.

  The basic processing flow in the present embodiment will be described with reference to FIG. First, as a premise of the operation in FIG. 4, it is assumed that the user apparatus UE is located in the best cell with the maximum reception strength selected at the time of cell selection.

  First, the user apparatus UE receives system information including frequency (generally a plurality) of cells in which the user apparatus UE can be located and priority information (priority) of each frequency from the base station eNB (step 11). .

  In step 12, the user apparatus UE performs a cell reselection process. Regarding cell reselection (inter-frequency / inter-RAT cell selection) for transition to a cell of a different frequency, the user apparatus UE has a higher priority than the frequency of the serving cell among the frequencies reported in the system information. Based on the priority information, a cell having a frequency is searched, and if the frequency satisfies a predetermined quality condition (reception strength is equal to or higher than a predetermined threshold, etc.), an operation in the new cell is performed. Cell reselection, but depending on the quality of the current serving cell and the quality of the transition destination, cell reselection may be performed to a cell with a priority equal to or lower than the current priority. .

  In step 12, as a result of the cell search for measuring the carrier of each frequency, there are a plurality of adjacent cell frequencies (frequency different from the frequency of the connected cell) in which the user apparatus UE can be located, and they have the same priority. . “Available in the area” means satisfying a predetermined quality condition.

  Here, in the prior art, if the priority is the same, a higher quality frequency is selected, but this cannot achieve band dispersion. Therefore, in the first embodiment, in step 12, a frequency having, as an index, the number obtained by taking the mod of the number of frequencies (N) as the identifier of the user apparatus UE is selected from the plurality of frequencies, Located in a frequency cell.

  The identifier of the user apparatus UE is, for example, a telephone number, IMEI (International Mobile Equipment Identity), or the like, but is not limited thereto.

  Further, the number of frequencies (N) is the number of frequencies having the same priority (frequency different from the frequency of the connected cell) in which the user apparatus UE can be located. For example, if N is 2, indexes of 0 and 1 are given to the two frequencies. Since mod 2 is 0 or 1, a frequency of 0 or 1 is selected. By selecting a frequency based on the identifier of the user apparatus UE for the same priority frequency, the frequencies can be selected almost equally among the user apparatuses UE, so that band dispersion can be achieved.

  A more specific control example in the first embodiment will be described below.

  For example, as described in Non-patent Document 1, in LTE, (1) measurement rules for cell reselection (Measurement rules for cell re-selection), (2) different frequency cell reselection criteria (E-UTRAN Inter- frequency and inter-RAT Cell Reselection criteria), (3) same-frequency and same-priority different frequency cell reselection (Intra-frequency and equal priority prioritization) The operation is performed according to these rules.

Regarding (3) above, as described in Non-Patent Document 1, in each of the neighboring cell (neighbor cell) and connected cell (serving cell) of the same priority, as shown in FIG. The ranking is performed by the index (R _s , R _n ) based on the index, and the cell with the highest rank is selected. In addition, with respect to the neighboring cell (R _n ), it is possible to set a unique offset (Qoffset _frequency ) for each _frequency .

  On the other hand, in the present embodiment, (3) the same-priority different-frequency cell reselection operation in the same-frequency and same-priority different-frequency cell reselection is different from the operation in the prior art. In this embodiment, since there are two types of operations, description will be given below as specific example 1 and specific example 2, respectively.

<Specific example 1>
In the specific example 1, the parameters to be used are as shown in FIG. 5, but only one frequency (carrier) of the same priority frequency (inter-frequency) is set for each user apparatus UE Qoffset _frequency = The offset value that has been broadcast is applied to other frequencies. By setting Qoffset _frequency = 0, the index (R _n ) increases, and the cell of the frequency is easily selected.

And in the specific example 1, the frequency corresponding to the value which took the mod of N which is the number of the frequency of the same priority with respect to the identifier (example: IMSI) of the user apparatus UE is selected similarly to the method mentioned above. To do. For example, assume that there are two frequencies having the same priority and the index is i (i = 0, 1). In this case, if IMSI mod N = 0, Qoffset _frequency = 0 for the frequency of i = 0, and if IMSI mod N = 1, Qoffset _frequency = 0 for the frequency of i = 1. Note that which frequency is set to which i can be the order in the notification information of the frequency of the adjacent cell in the system information (example: SIB5).

<Specific example 2>
In Example 2, as shown in FIG. 6, in the calculation of _{R n,} it introduces a new parameter Qoffset, UE. Qoffset, UE is information notified to the user apparatus UE by system information. Qoffset, if the UE has been added, _{R n} is increased and the frequency is easily selected.

  The frequency Qoffset and UE to which the non-zero Qoffset and UE are applied are the same as in the first specific example. That is, Qoffset, UE is applied to the frequency corresponding to the value obtained by taking N mod, which is the number of frequencies of the same priority, for the identifier (eg, IMSI) of the user apparatus UE, and Qoffset is used for other frequencies. , UE = 0. For example, assume that there are two frequencies having the same priority and the index is i (i = 0, 1). In this case, if IMSI mod N = 0, Qoffset and UE are enabled for the frequency of i = 0, and if IMSI mod N = 1, Qoffset and UE are enabled for the frequency of i = 1. Note that which frequency is set to which i can be the order in the notification information of the frequency of the adjacent cell in the system information (example: SIB5).

<Other examples in the first embodiment>
Although the example described so far is intended for cell reselection, the method of selecting a frequency based on the result of taking N mod for the identifier of the user apparatus UE is the cell selection performed before cell coverage. Is also applicable.

  That is, in the prior art, when selecting a cell, a cell having the best frequency is selected based on only quality, but this cannot achieve band dispersion. Therefore, in the present embodiment, when the user apparatus UE detects a plurality of frequencies of quality that can be located during cell selection (these can be regarded as the same priority), the number is set to N. The mobile station is located in the cell of the frequency corresponding to the result of taking N mod for the identifier of the user equipment UE. The ordering of N is arbitrary, and may be, for example, the detected order or the quality order.

  Further, in the example of cell reselection described so far, the selection is made so as to be evenly distributed such as taking mod. However, the capability, access class, reason of transmission (cause) of the user apparatus UE ), The frequency in the service area may be selected from a plurality of frequencies having the same priority according to the type. Further, as information replacing the existing priority information, information associating capability / access class or the like with a frequency to be preferentially selected may be notified as system information.

  For example, since a user apparatus UE (Voice capable UE) having voice communication capability is predicted to perform voice transmission, control can be performed to preferentially select a frequency from the core band. The “core band” is a band that serves as a predetermined core, and is a band suitable for voice communication. Moreover, the user apparatus UE (CA capable UE) having the capability of carrier aggregation can also be controlled to select a frequency of a band corresponding to CA. In addition, the user apparatus UE (for example, Premium User) having high priority may perform control so as to select a cell having a core band frequency in order to reduce cell reselection delay. For example, the user apparatus UE receives information associating the capability / access class and the frequency to be preferentially selected as system information, and based on the information and its own information. Can be executed.

  The access class corresponds to the priority of access, and each user apparatus UE generally has one of access classes 0 to 9. 11 to 15 are access classes with higher priority, and are assigned to user devices UE for special purposes such as security services.

  In the present embodiment, for example, the user apparatus UE having an access class of 0 to 9 can also perform control such that the user apparatus UE is located in a cell having an index frequency obtained by taking N mod in its own access class. N is as described above, and is the number of frequencies that can be located in the same priority in the cell reselection, and is the number of frequencies that can be located in the cell selection based on the quality.

  Also, it is possible to control the user apparatuses UE having access classes of 11 to 15 in the core band frequency.

  In addition, a history of which service (voice, Internet access, etc.) the user apparatus UE has made may be held, and frequency selection may be performed based on the history in cell selection or cell reselection. For example, since the user apparatus UE that frequently performs voice communication may be voice next time, the core band frequency may be preferentially selected. Voice communication is frequently performed, for example, when the ratio of the number of times of voice transmission is greater than or equal to a predetermined threshold among the number of times of transmission from a predetermined period before to the present.

  Moreover, the user apparatus UE may select the cell of the frequency which communicated last in cell selection. This is based on the fact that if the band distribution during communication is successful, the user apparatuses UE that are present will also be distributed. Further, the user apparatus UE may randomly select one frequency from frequencies at which the quality is equal to or higher than a predetermined level, and may be located in a cell having the frequency.

<Device configuration, processing flow example>
FIG. 7 shows a functional configuration of the user apparatus UE in the first embodiment. As shown in FIG. 7, user apparatus UE according to the present embodiment includes UL signal transmission section 101, DL signal reception section 102, control information storage section 103, and area control section 104. The functional configuration shown in FIG. 7 shows a configuration particularly related to the present embodiment, and includes a function for executing an operation defined in LTE as its basic function. The same applies to other embodiments.

  The UL signal transmission unit 101 transmits a radio signal to the base station eNB. The DL signal receiving unit 102 receives a radio signal from the base station eNB. In the control information storage unit 103, control information (for example, priority information) acquired from the radio signal received from the base station eNB by the DL signal receiving unit 102, information set in advance in the user apparatus UE (for example, identifier) ) Is stored.

  The located area control unit 104 performs a cell search and selects a frequency or the like as described above. For example, the located area control unit 104 selects N frequencies having the same priority that can be located based on the cell search result (quality of each frequency and the like) and the priority information stored in the control information storage unit 103. If detected, a cell having a frequency corresponding to a value obtained by taking N mod for the identifier of the user apparatus UE is selected and located.

  FIG. 8 is a diagram illustrating an example of a processing flow executed by the user apparatus UE in the present embodiment. In this example, the user apparatus UE receives, from the base station eNB, a flag that indicates whether or not to perform in-zone control for band distribution as described in the present embodiment, and the flag is ON. In some cases, the location control is performed.

  The user apparatus UE reads the system information of the serving cell (eg, the best quality best cell) (step 101), and checks whether the serving control flag is ON (step 102). If it is not ON, the location control process according to the present embodiment is not performed.

  When the in-zone control flag is ON, the user apparatus UE determines whether or not a cell search for transition to another cell is necessary based on the quality of the frequency of the located cell (step 103). If no cell search is required, the mobile station is located in the current cell (step 104).

  When cell search is necessary, cell search and frequency selection are performed (step 105). In step 105, when the user apparatus UE detects a plurality of high-priority frequencies having the same quality by cell search, for example, the user apparatus UE selects one frequency using the above-described selection method using mod, In the cell.

  Note that the configuration of the user apparatus in the present embodiment is not limited to the above, and may be any configuration that can execute the processing described in the present embodiment. For example, the following configuration may be used.

  That is, the user apparatus according to the present embodiment is a user apparatus that communicates with a base station in a mobile communication system, and performs a cell search to detect a plurality of frequencies having the same priority, Selecting means for selecting a frequency of a cell in which the user apparatus should be located based on conditions other than quality from among the frequencies.

  The selection unit can select a frequency of a cell in which the user apparatus should be located based on identification information of the user apparatus and the number of the plurality of frequencies. The selection unit may select a frequency of a cell in which the user apparatus should be located based on the capability of the user apparatus or an access class. With such a configuration, it is possible to select a frequency to be in service from a plurality of frequencies having the same priority according to information other than quality.

(Second Embodiment)
In the first embodiment, cell selection and cell reselection in a state where transmission is not performed have been described. On the other hand, in 2nd Embodiment, when the user apparatus UE transmits, cell reselection is performed in consideration of factors other than quality.

  Also in the present embodiment, the priority information is notified to the user apparatus UE for each frequency in the system information as in the first embodiment.

  However, the priority information in the present embodiment is associated with the type of transmission, access class, service type, and the like.

  As an example, in the adjacent cell, when the frequencies F1 and F2 exist in the core band and the frequencies F3 and F4 exist in the capacity band, the base station eNB performs F1 → The user apparatus UE is notified of priority information in the order of F2 → F3 → F4. Since the core band has a lower frequency than the capacity band and has a wide coverage, in the case of a voice service that requires coverage, the order is F1 → F2 → F3 → F4.

  Further, for example, in the case of a best effort (BE) service requiring a wide band (Web access or the like), the order may be F3 → F4 → F1 → F2.

  When the user apparatus UE makes a call, the user apparatus UE identifies the type of call (voice, BE data, etc.) and performs cell reselection according to the priority information notified by the system information corresponding to the type. Here, for example, regarding the identification of the type of voice transmission, the user apparatus UE may identify the voice transmission by detecting that the call button of the telephone is pressed, or transmit (or receive) the random access procedure. ) May be identified by information in the message to be identified, or may be identified by other methods. As for the best effort service, when it is detected that http data for accessing the Internet is transmitted, it may be detected that the best effort service is transmitted, or transmitted by a random access procedure. It may be identified by information in the (or received) message, or may be identified by other methods.

  The user apparatus UE starts a search (measurement) from a high-priority frequency, performs a search in descending order according to the priority until a predetermined quality is obtained, and is located in a cell of a frequency at which the predetermined quality is obtained. Make outgoing calls.

  In addition, when a plurality of frequencies having a predetermined quality and the same priority are detected, the frequencies may be selected at random, or, as in the first embodiment, the identifier (telephone number, IMEI) may select a frequency corresponding to the result of taking mod by the number of detected frequencies (N). Furthermore, the frequency corresponding to the result of taking the mod by the number of frequencies (N) at the time when the transmission is triggered (expressed by SFN, TTI, etc.) may be selected.

<Device configuration, processing flow example>
FIG. 9 shows a functional configuration of the user apparatus UE in the second embodiment. As shown in FIG. 9, user apparatus UE according to the present embodiment includes UL signal transmission section 201, DL signal reception section 202, control information storage section 203, transmission processing section 204, and area control section 205.

  The UL signal transmission unit 201 transmits a radio signal to the base station eNB. The DL signal receiving unit 202 receives a radio signal from the base station eNB.

  The control information storage unit 203 is control information (for example, system information) acquired from a radio signal received from the base station eNB by the DL signal receiving unit 202, or control information (for example, identifier) preset in the user apparatus UE. Is stored.

  The transmission processing unit 204 performs a transmission process of voice, data, and the like based on a user operation, for example. The located area control unit 205 performs the cell reselection process according to the control method described so far when the call processing unit 204 detects that the call is transmitted. For example, it is assumed that the frequencies F1, F2, F3, and F4 of adjacent cells exist, and priority information in the order of F1 → F2 → F3 → F4 is notified in the descending order of priority for the voice service. When the transmission processing unit 204 detects that the voice transmission is performed, the located area control unit 205 searches in the order of F1 → F2 → F3 → F4 until a frequency higher than the predetermined quality is found, and exceeds the predetermined quality. Is in a cell with a frequency of.

  FIG. 10 is a diagram illustrating an example of a processing flow executed by the user apparatus UE in the present embodiment. In this example, the user apparatus UE receives, from the base station eNB, a flag that indicates whether or not to perform in-zone control for band distribution as described in the present embodiment, and the flag is ON. In some cases, the location control is performed.

  The user apparatus UE reads the system information of the serving cell (eg, the best quality best cell) (step 201), and checks whether the serving control flag is ON (step 202). If it is not ON, the location control process according to the present embodiment is not performed.

  When the location control flag is ON, the user apparatus UE checks whether or not there is a call (step 203), and when the call is detected, the cell based on the priority information corresponding to the type of call or the like Reselection processing is performed (step 204). Here, a search is performed based on the priority information, but if a frequency of an adjacent cell satisfying a predetermined quality is not found, the cell is transmitted in the cell in which it is located (step 205). In the case of cell transition, transmission is performed after cell transition (step 206).

  Note that the configuration of the user apparatus in the present embodiment is not limited to the above, and may be any configuration that can execute the processing described in the present embodiment. For example, the following configuration may be used.

  That is, the user apparatus according to the present embodiment is a user apparatus that communicates with a base station in a mobile communication system, and a receiving unit that receives a priority for each frequency from the base station; In performing area control, cell search is performed in the order of frequencies based on the priority corresponding to the type of transmission, and the user apparatus is located in a cell having a frequency that satisfies a predetermined quality condition detected by the cell search. Means.

  The location control means may select a frequency of a cell in which the user apparatus should be located based on a condition other than quality when a plurality of frequencies having the same priority satisfying a predetermined quality condition are detected. it can. With such a configuration, it is possible to make the frequency range suitable for the user's transmission type and to achieve appropriate band dispersion.

(Third embodiment)
Next, a third embodiment will be described. In the third embodiment, it is the best cell based on quality that is selected by cell selection, and the best cell is connected as usual, but it is subject to loose regulation according to the load situation of each cell. To do.

  Also in the present embodiment, the user apparatus UE receives and holds priority information for each frequency from the base station eNB.

  The overall processing flow of the present embodiment will be described with reference to the sequence diagram of FIG. In order to communicate with the base station eNB, the user apparatus UE transmits a connection request (in this example, a random access preamble) to the base station eNB (step 301).

  The base station eNB that has received the connection request determines whether or not band distribution is necessary based on the load status of the cell in which the user apparatus UE is located (step 302). For example, the number of connected UEs in the cell, the ratio of UEs performing DRX, and the like can be used as the load status. If the value indicating the load status is equal to or greater than a predetermined threshold, it is determined that the user apparatus UE is excessively concentrated in the cell, and it is determined that band dispersion is necessary.

  When the base station eNB determines that band distribution is necessary, the base station eNB rejects the connection of the user apparatus UE to the cell. In this embodiment, the back-off timer in the response (random access response in this example) is set to infinity and the response is transmitted (step 303). The back-off timer is a timer indicating a time to wait before trying to connect again when the random access procedure fails in the user apparatus UE. When this value is Infinity, the user apparatus UE temporarily gives up connection to the cell, stops the random access procedure, and tries connection in order of higher priority at another frequency that satisfies the predetermined quality. The cell of another frequency may be another cell formed by the same base station eNB as the cell that has failed to connect, or may be a cell formed by the adjacent base station eNB, but the example of FIG. Shows an example of a cell formed by an adjacent base station eNB.

  As illustrated in FIG. 11, the user apparatus UE that has received a response including Infinity searches for another cell, stays in the cell (step 304), and tries to connect in the cell (step 305). In step 304 of FIG. 11, it is assumed that the priority of the cell to be connected in step 301 is the highest, and the priority of the cell to be connected next is the next.

  Even if the user apparatus UE is notified of the infinity, the user apparatus UE may notify the infinity in the case of a connection related to transmission by a specific service (eg, voice) or when the user apparatus UE itself is a high-priority user apparatus UE. You may try to connect to another cell again. However, this is a case where the cell that has notified the infinity is the best cell with the best quality. If it is not the best cell, the best cell may be detected by cell search, and the location and connection to the best cell may be performed.

  As described above, which service or UE priority is controlled according to Infinity may be notified from the base station eNB in the system information, or included in the information element in the random access response. May be.

  If the base station eNB determines in step 302 in FIG. 11 that band dispersion is not required, a response in which a finite value is set in the back-off timer is returned in the same manner as a normal random access response.

(Device configuration, processing flow)
FIG. 12 shows a functional configuration diagram of the base station eNB in the present embodiment. As illustrated in FIG. 12, the base station eNB includes a UL signal reception unit 301, a DL signal transmission unit 302, a load determination unit 303, and a UE connection processing unit 304.

  The UL signal reception unit 301 receives a radio signal from the user apparatus UE. The DL signal transmission unit 302 transmits a radio signal to the user apparatus UE. As described above, the load determination unit 303 acquires and holds a value indicating the load status such as the number of connected UEs for each cell, and band dispersion is necessary by comparing the value indicating the load status with a predetermined threshold. It is determined whether or not there is a need for band dispersion, and the UE connection processing unit 304 is notified of this.

  The UE connection processing unit 304 is a functional unit that performs connection processing with the user apparatus UE. When a connection request is received from the user apparatus UE located in a certain cell, the load determination unit 303 needs to perform band distribution. When the determination result is obtained, a response storing Infinity is returned to the user apparatus UE.

  FIG. 13 is a flowchart showing the operation of the base station eNB in the present embodiment. The UE connection processing unit 304 of the base station eNB receives a connection request from the user apparatus UE (step 401). The load determination unit 402 determines whether or not band distribution is necessary (step 402). If the band distribution is not necessary, the UE connection processing unit 304 transmits a response in which the back-off timer is set to a finite value (step 403). ). If band distribution is necessary, the UE connection processing unit 304 transmits a response in which the back-off timer is set to infinity (step 404).

  In FIG. 14, the function structure of the user apparatus UE in 3rd Embodiment is shown. As illustrated in FIG. 14, the user apparatus UE according to the present embodiment includes a UL signal transmission unit 401, a DL signal reception unit 402, a control information storage unit 403, a connection processing unit 404, and a location control unit 405.

  The UL signal transmission unit 401 transmits a radio signal to the base station eNB. The DL signal receiving unit 402 receives a radio signal from the base station eNB. The control information storage unit 403 includes control information (for example, system information) acquired from a radio signal received from the base station eNB by the DL signal receiving unit 402, information set in advance in the user apparatus UE (for example, access class, UE priority etc. are stored.

  The connection processing unit 404 performs connection processing (eg, random access procedure) with the base station eNB. The located area control unit 405 is a functional unit that performs cell reselection in the present embodiment, and checks the backoff timer in the response received from the base station eNB by the connection processing unit 404, and if it is Infinity, the priority information Based on the cell reselection, cell transition is performed. If it is a valid value, the normal connection procedure is continued.

  FIG. 15 is a diagram illustrating an example of a processing flow executed by the user apparatus UE in the present embodiment. Also in this example, the user apparatus UE receives, from the base station eNB, a flag instructing whether to perform location control based on the backoff timer as described in the present embodiment, and the flag is ON. In some cases, the location control is performed.

  The user apparatus UE reads the system information of the serving cell (eg, the best quality best cell) (step 501) and checks whether the serving control flag is ON (step 502). If it is not ON, the location control process according to the present embodiment is not performed.

  When the presence control flag is ON, the presence control unit 405 of the user apparatus UE checks whether or not the back-off timer included in the response received after transmitting the connection request is infinite (step 503). If it is infinite, cell search is performed at a frequency different from that of the cell in which the cell is located, and the cell is located in a cell having a different frequency with high priority in the neighboring cell that can be located and connected (step 504). If the back-off timer is a finite value, the normal connection procedure is continued (step 505).

  Note that the value of the backoff timer (Backoff Parameter value) may be associated with the index and the index notified. An example of the association table in that case is shown in FIG. “Voice only” in the figure indicates that it is applied only to voice communication.

  Note that the configuration of the user apparatus in the present embodiment is not limited to the above, and may be any configuration that can execute the processing described in the present embodiment. For example, the following configuration may be used.

  That is, the user apparatus according to the present embodiment is a user apparatus that communicates with a base station in a mobile communication system, and transmits a connection request to the base station and receives a response to the connection request from the base station. When a predetermined information is included in the response received by the processing means and the connection processing means, a cell search for a frequency different from the frequency of the cell where the user apparatus is located is performed and detected by the cell search A location control means for causing the user apparatus to be located in a cell having a frequency satisfying the predetermined quality condition.

  The response is a random access response in a random access procedure, and the predetermined information is information indicating that the back-off timer is an infinite value. With such a configuration, band dispersion is realized.

  In addition, the configuration of the base station in the present embodiment is not limited to the above, and any configuration that can execute the processing described in the present embodiment may be used. For example, the following configuration may be used.

  That is, the base station according to the present embodiment is a base station that communicates with a user apparatus in a mobile communication system, and is located in the cell, load determining means for determining a load in a cell formed by the base station When the load determination unit determines that the load of the cell is equal to or greater than a predetermined threshold when the connection request is received from the user apparatus, the cell by the user apparatus is included in a response to the connection request. Connection processing means for transmitting a response including the predetermined information including the predetermined information for refusing the connection to the user apparatus to the user apparatus. The response is a random access response in a random access procedure, and the predetermined information is information indicating that the back-off timer is an infinite value.

  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. I 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 user apparatus and the base station have been described using functional block diagrams, but such an apparatus may be realized in hardware, software, or a combination thereof. Software operated by a processor included in a user apparatus and software operated by a processor included in a base station according to the embodiment of the present invention are random access memory (RAM), flash memory, read-only memory (ROM), EPROM, and EEPROM. , A register, a hard disk (HDD), a removable disk, a CD-ROM, a database, a 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 101 UL signal transmission unit 102 DL signal reception unit 103 control information storage unit 104 presence control unit 201 UL signal transmission unit 202 DL signal reception unit 203 control information storage unit 204 transmission processing unit 205 presence control unit 301 UL signal reception unit 302 DL signal transmission unit 303 Load determination unit 304 UE connection processing unit 401 UL signal transmission unit 402 DL signal reception unit 403 Control information storage unit 404 Connection processing unit 405 In-zone control unit

Claims (10)

A user apparatus that communicates with a base station in a mobile communication system,
Detecting means for detecting a plurality of frequencies having the same priority by performing a cell search;
A selection unit that selects a frequency of a cell in which the user apparatus should be located based on a condition other than quality from the plurality of frequencies;
A user apparatus comprising: 2. The user apparatus according to claim 1, wherein the selection unit selects a frequency of a cell in which the user apparatus should be located based on identification information of the user apparatus and the number of the plurality of frequencies. . The user apparatus according to claim 1, wherein the selection unit selects a frequency of a cell in which the user apparatus should be located based on a capability of the user apparatus or an access class. A user apparatus that communicates with a base station in a mobile communication system,
Receiving means for receiving a priority for each frequency from the base station;
When the user apparatus performs transmission, cell search is performed in the order of frequencies based on the priority corresponding to the type of transmission, and the user apparatus is placed in a cell having a frequency satisfying a predetermined quality condition detected by the cell search. A user apparatus comprising: a visiting area control means for allowing a user to be in the area. The location control means, when detecting a plurality of frequencies of the same priority satisfying a predetermined quality condition, selects a frequency of a cell to which the user apparatus should be located based on conditions other than quality. The user device according to claim 4, characterized in that: A user apparatus that communicates with a base station in a mobile communication system,
A connection processing means for transmitting a connection request to the base station and receiving a response to the connection request from the base station;
When the response received by the connection processing means includes predetermined information, a cell search is performed for a frequency different from the frequency of the cell in which the user apparatus is located, and the predetermined frequency detected by the cell search is detected. A user apparatus comprising: a location control means for causing the user apparatus to be located in a cell having a frequency satisfying a quality condition. The user apparatus according to claim 6, wherein the response is a random access response in a random access procedure, and the predetermined information is information indicating that a back-off timer is an infinite value. A base station that communicates with a user apparatus in a mobile communication system,
Load determining means for determining a load in a cell formed by the base station;
When a connection request is received from the user apparatus residing in the cell and the load determination unit determines that the load of the cell is equal to or greater than a predetermined threshold, in a response to the connection request, Connection processing means for transmitting a response including the predetermined information to the user apparatus, including predetermined information for refusing connection to the cell by the user apparatus. The base station according to claim 8, wherein the response is a random access response in a random access procedure, and the predetermined information is information indicating that a back-off timer is an infinite value. A frequency selection method executed by a user apparatus communicating with a base station in a mobile communication system,
A detection step of detecting a plurality of frequencies having the same priority by performing a cell search;
A selection step of selecting a frequency of a cell in which the user apparatus should be located based on a condition other than quality from the plurality of frequencies;
A frequency selection method comprising:

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