JP2014143651A - Mobile communication system, communication method, and base station device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a mobile station device to perform efficient cell search operation.SOLUTION: While a first base station device is communicating with a mobile station device, when the first base station device requests handover of the mobile station from the first base station device to a second base station device which performs communication at a frequency different from the first base station device, determines the number of times or time limit for the mobile station device to search for the second base station device on the basis of speed of the mobile station device, and transmits the determined number of times or time limit to the mobile station device. The mobile station device searches for the second base station device within a range of the number of times or time limit given by the first base station device.

Description

  The present invention relates to a mobile communication system, a communication method, and a base station apparatus.

In a public wireless communication system such as LTE-A (Long Term Evolution-Advanced), when a mobile station moves during packet communication, handover is performed to switch from the currently communicating base station to another base station. There is. When the mobile station receives a message requesting handover from the base station, the mobile station searches for another base station using the same frequency as that of the currently communicating base station or another base station using a different frequency. Here, when searching for a base station using the same frequency, a search operation can be performed using a receiving circuit currently in communication. On the other hand, when searching for a base station using a different frequency, the search operation cannot be performed with the setting of the receiving circuit currently communicating, and a GAP (non-receiving interval) is set in order to change the frequency. Then, a frequency different from the frequency during communication is set for the wireless reception circuit, and a peripheral cell search operation with a different frequency is performed. In the time zone in which the GAP is set and the different frequency cell search operation is performed, the data communication with the communicating base station is temporarily interrupted.
In LTE-A, it is assumed that a small cell base station such as HetNet is arranged. In an area where a large number of small cell base stations assumed in LTE-A are arranged, the number of small cell base stations arranged is larger than the number of macro cell base stations. In order to prevent interference with surrounding small cell base stations and macro cell base stations, it is difficult to use the same frequency band, and different frequency bands that do not interfere with surrounding small cell base stations and macro cell base stations are used. It is assumed that
Note that LTE-A employs a carrier aggregation (CA) technique for the purpose of maintaining compatibility with LTE as much as possible. In the CA technology, a communication device performs broadband communication by simultaneously using a plurality of frequency bands up to a bandwidth of 20 MHz called a component carrier (CC). In LTE-A, it is considered to perform a different frequency cell search operation using a vacant radio reception circuit for a mobile station having a plurality of CA-compatible reception circuits. (For example, refer nonpatent literature 1).

NTT DOCOMO, "LTE / Hetnet Mobility: Inter-frequency Hetnet", 3GPP, 3GPP TSG-RAN WG2 # 78 R2-122568

  When a mobile station performs handover to a small cell base station according to a handover request message from a macro cell base station in a situation where many small cell base stations operating using different frequencies are arranged, The operation of searching for a small cell base station (search operation) may frequently occur. Since a small cell base station generally has a narrow service area, when the mobile station is moving, even if a different frequency cell search operation is performed, the small cell base station cannot be detected or the reception level is low. The reception level may not be stable. In this case, the probability of detecting a small cell base station suitable for handover is lowered, and a useless different frequency cell search operation may be performed. In addition, if a macro cell base station requests a search operation several times until a small cell base station with a different frequency suitable for handover is found, the power consumption of the mobile station increases according to the number of times the search is performed. . As a result, an inefficient cell search operation may be performed.

  The present invention has been made in consideration of such circumstances, and an object thereof is to allow a mobile station apparatus to perform an efficient cell search operation.

  One embodiment of the present invention includes a first base station device, a second base station device that performs communication at a frequency different from that of the first base station device, a first base station device, and a second base station device. The first base station device can communicate with the mobile station device when requesting a handover from the own device to the second base station device during communication with the mobile station device. The number of times or time limit for searching for the second base station device is determined based on the speed of the mobile station device, and the determined number of times or time limit is transmitted to the mobile station device. This is a mobile communication system that searches for the second base station device within the range of the number of times notified from or the time limit.

  According to one aspect of the present invention, it is possible to cause a mobile station apparatus to perform an efficient cell search operation.

It is a figure which shows typically the whole structure of the mobile communication system 1 of 1st Embodiment. FIG. 2 is a diagram illustrating an example of functional configurations of a mobile station 100 and a macrocell base station 200. It is an example of the flowchart which shows the flow of the process performed in the mobile communication system 1 of 1st Embodiment. 6 is an example of a timing chart showing an example of operations of transmission / reception units 102 and 104. It is the figure which illustrated transition of the reception level. It is the figure which illustrated the relationship between transition of the reception level in the mobile communication system 2 of 2nd Embodiment, and the time limit of a different frequency cell search trial. It is a figure which shows typically the whole structure of the mobile communication system 3 which concerns on 3rd Embodiment.

  Hereinafter, embodiments of a mobile communication system, a communication method, and a base station apparatus according to the present invention will be described with reference to the drawings.

<First Embodiment>
FIG. 1 is a diagram schematically showing an overall configuration of a mobile communication system 1 according to the first embodiment. 1, a mobile communication system 1 includes a mobile station 100, a macro cell base station 200, and small cell base stations 300-1, 300-2,... 300-n (n is an arbitrary positive integer). . In FIG. 1, A (200), A (300-1), A (300-2), and A (300-n) are the macro cell base station 200 and the small cell base stations 300-1, 300-2, 300, respectively. -N indicates a service providing area. Hereinafter, when it is not distinguished which small cell base station, it will be simply referred to as the small cell base station 300. In FIG. 1, the mobile station 100 is illustrated as a single unit, but actually, a plurality of mobile stations 100 may exist within the service range of the macrocell base station 200. Further, for example, one macro cell base station 200 is installed in a macro cell obtained by dividing an area, and a plurality of macro cell base stations 200 exist corresponding to a plurality of macro cells.

  Further, in the present embodiment, “small cell base station” is a general term for HeNB (Home eNode B), HetNet (Heterogeneous Network), etc., and is a concept that excludes the macro cell base station 200. For example, the small cell base station 300 is installed in the service providing area of the macro cell base station 200, and an area narrower than the service providing area A (200) of the macro cell base station 200 is set as the service providing area. The macro cell base station 200 and the small cell base station 300 are communicably connected via an IP (Internet Protocol) network or the like. In the present embodiment, there is no particular limitation on the number of small cell base stations 200. The small cell base station 300 may include one that performs communication at the same frequency as the macro cell base station 200 and one that performs communication at a different frequency. The notations such as F1, F2,... In FIG. 1 represent frequencies used by the macro cell base station 200 and the small cell base station 300 in communication. In the example of FIG. 1, the macro cell base station 200 and the small cell base station 300-1 communicate at the frequency F1, the small cell base station 300-2 communicates at the frequency F2, and the small cell base station 300-3 communicates at the frequency. Communication is performed at F3. Each base station is assumed to perform communication using a frequency “band” having a certain bandwidth, but will be described simply as a frequency in this specification.

  FIG. 2 is a diagram illustrating an example of functional configurations of the mobile station 100 and the macrocell base station 200. As illustrated in FIG. 2, the mobile station 100 includes, for example, a plurality of CA compatible transceiver units 102 and 104, a user interface unit 106, a memory unit 108, and a control unit 110. Moreover, the macrocell base station 200 includes, for example, a transmission / reception unit 202, a memory unit 204, and a control unit 206. In addition, although illustration is abbreviate | omitted about the function structure of the small cell base station 300, you may have a structure similar to the macrocell base station 200. FIG.

  The mobile station 100 is, for example, a mobile phone or a tablet terminal. The transmission / reception units 102 and 104 are each provided with a transmission / reception antenna, perform processing such as down-conversion and demodulation on the signals received from the macro cell base station 200 and the small cell base station 300, and output to the control unit 110. In addition, the transmission / reception units 102 and 104 perform processing such as modulation and up-conversion on the signal input from the control unit 110 and transmit the processed signal to the macro cell base station 200 or the small cell base station 300. The user interface unit 106 includes, for example, a display device such as a touch panel, input keys, a microphone, a speaker, and the like. The memory unit 108 stores information such as the IDs of the macro cell base station 200 and the small cell base station 300 and the frequencies used based on the communication information input from the transmission / reception units 102 and 104. The control unit 110 controls each unit of the mobile station 100 so as to establish a call or display an image / text according to the result of voice communication or image / text communication.

  Similarly, in macro cell base station 200, transmission / reception section 202 includes a transmission / reception antenna, performs processing such as down-conversion and demodulation on the signal received from mobile station 100, and outputs the result to control section 206. Further, the transmission / reception unit 202 performs processing such as modulation and up-conversion on the signal input from the control unit 206 and transmits the signal to the mobile station 100. The memory unit 204 stores information such as information on frequencies used by the small cell base station 300 and PCI (Physical Cell ID). The control unit 206 communicates with the mobile station 100 and performs various controls for causing the mobile station 100 to make a call or access the Internet. 2 and the above description are not limited to the single transmitter / receiver included in the macro cell base station 200 and the small cell base station 300. In addition, the mobile station apparatus 100 can perform a different frequency cell search, which will be described later, using a plurality of transmission / reception units 102 and 104 that are vacant.

FIG. 3 is an example of a flowchart showing a flow of processing executed in the mobile communication system 1 of the first embodiment. The flowchart in FIG. 3 is executed when communication connection is established between the mobile station 100 and the macrocell base station 200.
First, the macro cell base station 200 determines whether to request the mobile station 100 to perform a handover to the small cell base station 300 (step S400). The determination (determination) in step S400 is performed based on, for example, optimization logic for the purpose of distributing communication load and processing load. When the macro cell base station 200 determines to request handover, it notifies the mobile station 100 of neighboring cell configuration information (Report Proximity Config) as a reconfiguration message 1 (Reconfiguration 1) (step S402). The neighbor cell configuration information is information on the small cell base station 300 held by the macro cell base station 200.

  When the mobile station 100 receives the neighboring cell configuration information, the mobile station 100 collates the received neighboring cell configuration information with the information (cell list) stored in the memory unit 108 (step S404), and performs a small operation described in the neighboring cell configuration information. It is estimated whether the cell base station 300 exists nearby, and proximity information (Proximity Indication) is notified to the macro cell base station 200 (step S406). When the macro cell base station 200 receives the proximity information, the macro cell base station 200 determines whether or not the small cell base station 300 exists near the mobile station 100 based on the message contents of “enter” and “leave” included in the proximity information. . The macro cell base station 200 can determine that the small cell base station 300 exists near the mobile station 100 when the proximity information including “enter” is received. Further, the macro cell base station 200 can determine that the small cell base station 300 does not exist near the mobile station 100 when the proximity information including “leave” is received. Then, the macro cell base station 200 requests the mobile station 100 to notify the PCI of the neighboring cell notified by the neighboring cell configuration information as the reconfiguration message 2 (Reconfiguration 2) (step S408). In response to the received PCI request, the mobile station 100 notifies the macro cell base station 200 of the PCI of the small cell base station 300 estimated to exist nearby (step S410).

  When the macro cell base station 200 receives the PCI notification, the macro cell base station 200 collates with the information stored in the memory unit 204, and the small cell base station 300 specified by the PCI notification communicates at a frequency different from that of the own station (macro cell base station 200). It is determined whether or not to perform (step S412). When the small cell base station 300 specified by the PCI notification communicates at the same frequency as the own station, the macro cell base station 200 transmits a system information request message (SI request) to the reconfiguration message 3 (Reconfiguration message). 3) is transmitted to the mobile station 100 (step S414).

  On the other hand, when the small cell base station 300 specified by the PCI notification communicates at a frequency different from that of the own station, the macro cell base station 200 estimates the speed of the mobile station 100 (step S416). The macrocell base station 200 estimates the speed of the mobile station 100 based on the reception level of the signal from the mobile station 100, for example. The macro cell base station 200 determines that the moving speed is low when the reception level of the signal from the mobile station 100 is stable or changes little over time, and the reception level is unstable or changes over time. If is large, it is determined that the vehicle is moving at high speed. However, the macro cell base station 200 receives the speed calculated by itself by the mobile station 100 by integrating the output of the acceleration sensor from the mobile station 100 together with the PCI information, etc. May be estimated. For example, the macro cell base station 200 estimates the speed of the mobile station 100 in three stages of high, medium, and low. Not limited to this, the macrocell base station 200 may estimate the speed of the mobile station 100 in two stages, four stages or more, or may estimate it linearly as an analog value.

Next, the macro cell base station 200 determines the number of different frequency cell search trials performed by the mobile station 100 based on the estimated speed of the mobile station 100 (the number of times the small cell base station is searched at a frequency different from the frequency currently being communicated). (Step S418) The macro cell base station 200 has a lower speed of the estimated mobile station 100, and the closer the state is to a stationary state, the more the number of different frequency cell search trials, and the higher the estimated speed of the mobile station 100 is. For example, the macro cell base station 200 determines the number of times of different frequency cell search attempts based on the following relationship. Will be described later.
Mobile station 100 speed: Low-Different frequency cell search trials: 3 times Mobile station 100 speed: Medium-Different frequency cell search trials: 2 Mobile station 100 speed: High-Different frequency cell search trials: 1 Times

  Then, the macro cell base station 200 uses the SI request including the frequency used by the small cell base station 300 specified by the PCI notification and the determined number of different frequency cell search attempts as the reconfiguration message 3 as the mobile station. 100 (step S420). When receiving an SI request including the number of different frequency cell search attempts, the mobile station 100 starts a cell search operation (step S422). The cell search operation is continued until it is confirmed that a sufficient reception level is obtained from the target small cell base station 300 or until the number of searches is completed (steps S424 and S426). When the SI request received from the macro cell base station includes the number of different frequency cell search attempts, the number of searches is the number of different frequency cell search attempts, and when the SI request does not include the number of different frequency cell search attempts, for example, This is a predetermined number of times. When the cell search operation ends, the mobile station 100 notifies the macro cell base station 200 of the cell search result as a measurement report (step S428).

  FIG. 4 is a timing chart showing an example of operations of the transmission / reception units 102 and 104 when the search is performed three times and the small cell base station 300 to be searched communicates with the macro cell base station 200 at a different frequency F2. It is an example. As shown in FIG. 4, for example, the transceiver unit 102 communicates with the macrocell base station 200 at the frequency F1, while the transceiver unit 104 receives a common channel signal (broadcast information) from the small cell base station 300 at the frequency F2. To do. If the mobile station 100 determines that the reception level does not reach a sufficient level even if the broadcast information of the small cell base station 300 is acquired in the first cell search, the mobile station 100 performs the second cell search. If the reception level does not reach a sufficient level as a result of the second cell search, the third cell search is performed. When the mobile station 100 performs the third cell search, the mobile station 100 determines whether or not the handover is possible based on the three determination results. When a sufficient reception level can be secured in the three cell searches, the mobile station 100 notifies the macro cell base station 200 that the handover can be performed. When a sufficient reception level cannot be ensured in the three cell searches, the mobile station 100 notifies the measurement report that the handover is not performed or the small cell base station 300 is not found. If the reception level of the small cell base station 300 is sufficiently high in the first cell search, the cell search may be completed once. The “reception level” is, for example, an index such as desired signal power versus interference signal power (SIR), reference signal received power (RSRP), channel quality indicator (CQI), and the like. is there.

The mobile station 100 determines whether or not a sufficient reception level has been secured using, for example, two threshold values A and B (A> B) as follows. The threshold A is sufficiently high as long as it is greater than this, and is a value that can suitably perform handover. Further, the threshold value B is a value that is determined to be better if handover is not performed below this threshold value B. Note that the mobile station 100 may set the reception level from the macrocell base station 200 performing communication at that time as the threshold A. This is because if the reception level is equal to or higher than the threshold value A, it can be determined that if the handover is performed, the reception level is improved from that point.
(1) The mobile station 100 determines that handover is possible when the reception level reaches the threshold value A in any one of the cell searches. In this case, the mobile station 100 ends the cell search when it is confirmed that the reception level has reached the threshold value A.
(2) When the mobile station 100 is not (1) and the reception level reaches the threshold value B in all cell searches (“the reception level did not fall below the threshold value B in all cell searches) It is also possible to make a handover.
(3) When the mobile station 100 is not (1) and the reception level at any time does not reach the threshold value B (in the cell search at any time, “when the reception level falls below the threshold value B”) It may be determined that the handover is not performed.

  FIGS. 5A to 5C are diagrams illustrating the transition of the reception level corresponding to the cases (1) to (3). 5A corresponds to (1), FIG. 5B corresponds to (2), and FIG. 5C corresponds to (3). In the transition of the reception level shown in FIG. 5A, since the reception level has reached the threshold A in the first cell search, it is determined that the handover is possible, and the second and subsequent cell searches are not performed. In the transition of the reception level shown in FIG. 5B, the reception level has not reached the threshold A in the first to third cell searches, but the reception level has reached the threshold B in each cell search. It is determined that over is possible. In the transition of the reception level shown in FIG. 5C, the reception level does not reach the threshold A in the first to third cell searches, and the reception level reaches the threshold B in each cell search. Therefore, it is determined that the handover is not performed.

  According to the mobile communication system 1 of the first embodiment described above, the number of times that the mobile station 100 performs cell search is determined based on the speed of the mobile station 100, and the mobile station 100 is within the determined number of times. Thus, since the small cell base station 300 is searched, the mobile station 100 can perform an efficient cell search operation.

  Here, when the mobile station 100 is moving at high speed, even if a handover to the small cell base station 300 is performed, the mobile station 100 immediately moves out of the service providing area of the small cell base station 300. Is assumed. When the mobile station 100 moves out of the service providing area of the small cell base station 300, the next handover is required, resulting in an increase in power consumption. Therefore, when the mobile station 100 is moving at high speed, it is considered better not to actively perform handover from the macrocell base station 200. However, if it is possible to perform handover to the small cell base station 300 with a small number of cell searches, the power consumption required for the handover itself is small, so that handover may be permitted.

  Conversely, when the mobile station 100 is stationary or moving at a low speed, it is considered better to actively perform handover to the small cell base station 300 from the viewpoint of distribution of communication processing load. In this case, the mobile communication system 1 can perform handover more reliably by causing the mobile station 100 to perform cell search more times than when moving at high speed. From the above viewpoint, the mobile communication system 1 according to the first embodiment can cause the mobile station 100 to perform an efficient cell search operation.

Second Embodiment
Hereinafter, the mobile communication system 2 of 2nd Embodiment is demonstrated. Here, parts that are the same as those in the first embodiment are denoted by the same reference numerals, description thereof is omitted, and only differences are described. In the mobile communication system 2 of the second embodiment, the macro cell base station 200 performs the different frequency cell search trial performed by the mobile station 100 based on the estimated speed of the mobile station 100 instead of the process of step S418 in FIG. The “time limit” is determined and notified to the mobile station 100. The macro cell base station 200 increases the time limit of the different frequency cell search trial as the estimated speed of the mobile station 100 is lower and is closer to a stationary state. The higher the estimated speed of the mobile station 100 is, the different frequency cell search trial is. Therefore, the time limit for the different frequency cell search trial is determined. For example, the macro cell base station 200 determines the time limit for the different frequency cell search trial based on the following relationship. The mobile station 100 performs cell search within the notified time limit. Whether or not the time is within the time limit is determined using a timer (not shown) provided in the control unit of mobile station 100.
Speed of mobile station 100: Low-different frequency cell search time limit: 500 [msec]
Mobile station 100 speed: Medium-different frequency cell search time limit: 200 [msec]
Speed of mobile station 100: High-Different frequency cell search time limit: 100 [msec]

  FIGS. 6A to 6C are diagrams illustrating the relationship between the transition of the reception level and the time limit for different frequency cell search trials in the mobile communication system 2 of the second embodiment. FIG. 6A shows a case where the time limit for the different frequency cell search trial is set to 500 [msec] and the reception level reaches the threshold value A. In this case, it is determined that a handover is possible. In the case of FIG. 6A, 500 [msec] has elapsed when the reception level reaches the threshold value A (or when the time when the reception level exceeds the threshold value A exceeds a predetermined time). Even if not, the different frequency cell search trial may be stopped. FIG. 6B shows a case where the time limit for the different frequency cell search trial is set to 500 [msec], and the reception level has not reached the threshold A, but never falls below the threshold B. In this case, it is determined that a handover is possible. FIG. 6C shows a case where the time limit for the different frequency cell search attempt is set to 100 [msec], and the reception level has not reached the threshold A, but never falls below the threshold B. In this case, it is determined that a handover is possible.

  According to the mobile communication system 2 of the second embodiment described above, the time limit for the mobile station 100 to perform cell search is determined based on the speed of the mobile station 100, and the mobile station 100 is determined by the macro cell base station 200. Since the small cell base station 300 is searched within the limited time limit, the mobile station 100 can perform an efficient cell search operation.

<Third Embodiment>
Hereinafter, the mobile communication system 3 of 3rd Embodiment is demonstrated. Here, parts that are the same as those in the first embodiment are denoted by the same reference numerals, description thereof is omitted, and only differences are described.

  FIG. 7 is a diagram schematically showing the overall configuration of the mobile communication system 3 according to the third embodiment. In the mobile communication system 3, the macro cell base station 200 and the small cell base station 300-1 communicate at the frequency F1, the small cell base station 300-2 communicates at the frequency F2 or F3, and the small cell base station 300- 3 communicates at the frequency F3.

In the mobile communication system 3 of the third embodiment, the macro cell base station 200 determines the number of different frequency cell search attempts for the small cell base station 300-2 having a plurality of frequencies to be used based on the estimated speed of the mobile station 100. (Or time limit) is determined for each frequency and notified to the mobile station 100. The following is an example of a part of information notified from the macro cell base station 200 to the mobile station 100 according to the third embodiment.
{Frequency F2: Different frequency cell search attempts 3 times}
{Frequency F3: Different frequency cell search trial count 3 times} or {Frequency F2: Different frequency cell search limit time 500 [msec]}
{Frequency F3: Different frequency cell search time limit 500 [msec]}

  The mobile station 100 performs a cell search within the range of the number of different frequency cell search attempts (or time limit) notified for each frequency. Accordingly, the mobile station 100 can perform an efficient cell search operation. The macro cell base station 200 increases the number of different frequency cell search trials (or lengthens the time limit) for a frequency with a small communication load in consideration of, for example, the communication load for each frequency in the small cell base station 300-2. Thus, handover to a frequency with a small communication load is performed preferentially.

  According to the mobile communication system 3 of the third embodiment described above, it is possible to cause the mobile station 100 to perform an efficient cell search operation as in the first embodiment and the second embodiment.

<Fourth embodiment>
Hereinafter, the mobile communication system 4 of 4th Embodiment is demonstrated. The mobile communication system 4 of the fourth embodiment has the same configuration as that shown in FIG. The macro cell base station 200 according to the fourth embodiment determines, for each frequency, the number of different frequency cell search attempts (or time limit) when performing handover to the small cell base station 300, and broadcast information that is a common channel. To the mobile station 100 that can communicate with its own device. The following is a diagram illustrating a part of information notified from the macro cell base station 200 to the mobile station 100 according to the fourth embodiment.
{Frequency F2: Different frequency cell search attempts 3 times}
{Frequency F3: Number of different frequency cell search attempts 3 times}
{Frequency F4: Different frequency cell search trials twice} or {Frequency F2: Different frequency cell search limit time 500 [msec]}
{Frequency F3: Different frequency cell search time limit 500 [msec]}
{Frequency F4: Different frequency cell search time limit 300 [msec]}

  When the mobile station 100 communicating with the macro cell base station 200 receives a handover request from the macro cell base station 200, the mobile station 100 within a range of the number of different frequency cell search attempts (or time limit) for each frequency received in advance. Perform cell search. Accordingly, the mobile station 100 can perform an efficient cell search operation.

  According to the mobile communication system 4 of the fourth embodiment described above, an efficient cell search operation can be performed by the mobile station 100 as in the first to third embodiments.

  As mentioned above, although the form for implementing this invention was demonstrated using embodiment, this invention is not limited to such embodiment at all, In the range which does not deviate from the summary of this invention, various deformation | transformation and substitution Can be added.

<Appendix>
The present invention can be implemented in the following modes.
[1] The first base station apparatus (200), the second base station apparatus (300-2, 300-n) that communicates at a frequency different from that of the first base station apparatus, and the first base station And a mobile station device (100) capable of communicating with the second base station device, wherein the first base station device is a hand from the own device to the second base station device during communication with the mobile station device. When requesting over, the mobile station device determines the number of times or time limit for searching for the second base station device based on the speed of the mobile station device, and transmits the determined number of times or time limit to the mobile station device, The mobile station device searches for the second base station device within the range of the number of times or the time limit notified from the first base station device, and the mobile communication system (1). According to this, it is possible to cause the mobile station to perform an efficient cell search operation.
[2] The mobile communication system according to [1], wherein the first base station device includes a plurality of first base station devices that perform handover at a plurality of frequencies when a second base station device that requests a handover from the own device performs communication at a plurality of frequencies. A mobile communication system that determines the number of times or the time limit for the mobile station apparatus to search for the second base station apparatus for each of the frequencies based on the speed of the mobile station apparatus, and transmits the determined number to the mobile station apparatus .
[3] The first base station apparatus can communicate with the second base station apparatus that communicates at a frequency different from that of the first base station apparatus, and the first base station apparatus and the second base station apparatus. In a mobile communication system comprising a mobile station device, when the first base station device requests a handover from the own device to the second base station device during communication with the mobile station device, the mobile station device Determines the number of times or the time limit for searching the second base station device based on the speed of the mobile station device, transmits the determined number of times or time limit to the mobile station device, and the mobile station device transmits the first base station. A communication method for searching for a second base station device within a range of the number of times notified from the device or a time limit.
[4] During communication between the mobile station apparatus and the transmission / reception unit (202) that communicates with the mobile station apparatus, a request for handover from the own apparatus to another base station apparatus that performs communication at a frequency different from that of the own apparatus is requested. The mobile station device determines the number of times or the time limit for searching for another mobile station device based on the speed of the mobile station device, and transmits and receives the determined number or time limit to the mobile station device. And a control unit (206) for controlling the base station device (200).
[5] The base station apparatus according to [4], wherein the control unit, when another base station apparatus that requests a handover from the own apparatus performs communication at a plurality of frequencies, A base station that determines the number of times or time limit for the mobile station device to search for another mobile station device based on the speed of the mobile station device, and controls the communication unit to transmit the determined number of times or time limit to the mobile station device. Station equipment.
[6] The first base station apparatus can communicate with the second base station apparatus that communicates at a frequency different from that of the first base station apparatus, and the first base station apparatus and the second base station apparatus. The first base station device searches for the second base station device when the first base station device performs a handover from the own device to the mobile station device capable of communicating with the own device. The mobile station device using the common channel, and the mobile station device searches for the second base station device within the range of the number of times or the time limit notified from the first base station device. To
Mobile communication system.

  DESCRIPTION OF SYMBOLS 1 ... Mobile communication system, 100 ... Mobile station, 102, 104 ... Transmission / reception part, 110 control part, 200 ... Macro cell base station, 202 ... Transmission / reception part, 206 ... Control part, 300 ... Small cell base station

Claims (5)

A first base station device;
A second base station apparatus that performs communication at a frequency different from that of the first base station apparatus;
A mobile station apparatus capable of communicating with the first base station apparatus and the second base station apparatus,
When the first base station device requests a handover from the own device to the second base station device during communication with the mobile station device, the mobile station device uses the second base station device. Determining the number of times to search or the time limit based on the speed of the mobile station device, and transmitting the determined number of times or time limit to the mobile station device;
The mobile station device searches for the second base station device within a range of the number of times notified from the first base station device or a time limit,
Mobile communication system. The mobile communication system according to claim 1, wherein
When the second base station apparatus that requests a handover from the first base station apparatus performs communication at a plurality of frequencies, the mobile station apparatus performs a second operation for each of the plurality of frequencies. Determining the number of times or time limit for searching the base station device based on the speed of the mobile station device, and transmitting the determined number of times to the mobile station device.
Mobile communication system. A first base station apparatus, a second base station apparatus that communicates at a frequency different from that of the first base station apparatus, and a mobile that can communicate with the first base station apparatus and the second base station apparatus In a mobile communication system comprising a station device,
When the first base station apparatus requests a handover from the own apparatus to the second base station apparatus during communication with the mobile station apparatus, the mobile station apparatus selects the second base station apparatus. Determining the number of times to search or the time limit based on the speed of the mobile station device, and transmitting the determined number of times or time limit to the mobile station device;
The mobile station device searches for the second base station device within the range of the number of times or the time limit notified from the first base station device;
Communication method. A transmission / reception unit for communicating with the mobile station device;
During the communication with the mobile station apparatus, when the mobile station apparatus requests a handover from the own apparatus to another base station apparatus that performs communication at a frequency different from that of the own apparatus, the mobile station apparatus transmits the other base station apparatus. A control unit that controls the transceiver unit so as to transmit the determined number of times or the time limit to the mobile station device;
A base station apparatus comprising: The base station apparatus according to claim 4, wherein
The control unit searches for another base station apparatus for each of the plurality of frequencies when another base station apparatus that requests a handover from the own apparatus performs communication at the plurality of frequencies. Determining the number of times or the time limit based on the speed of the mobile station device, and controlling the transceiver to transmit the determined number of times or time limit to the mobile station device;
Base station device.

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