JP4237205B2 - Mobile communication system, mobile station, and diversity handover branch control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel and useful diversity handover branch control method or the like. <P>SOLUTION: The mobile station monitors radio state quality corresponding to a plurality of branches while communicating simultaneously with a plurality of base stations, and notifies information of the plurality of branches including one or more branches during communication or one or more additional branch candidates to a center. The center receives the information of the plurality of branches. The mobile station arranges one or more branches during communication and one or more additional branch candidates in order of monitored radio state quality, and notifies the center in order of arranging the branches during communication and the additional branch candidates. The center sets one or more branches during communication for diversity handover using the notified additional branch candidates in oder of arrangement. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a novel and useful diversity handover branch control method and the like. Some embodiments of the present invention include a branch candidate selection method by a mobile station when a plurality of additional branch candidates and deleted branch candidates are detected by the mobile station, and diversity by the network side in the execution of diversity handover. The present invention relates to a handover branch (Diversity Handover Branch) control method.

  In recent years, code division multiple access (CDMA) technology has been proposed as one of radio transmission technologies for realizing multimedia communication in next-generation mobile communication network systems. In CDMA, a plurality of communication links (branches) are set between a mobile station and a plurality of base stations due to movement of a mobile station near the boundary of a radio area, and signal combining (selective combining) is performed on the plurality of communication links. Diversity Handover (DHO) is performed to perform communication. In the diversity state, the radio capacity can be expanded (transmission power control) by controlling the mobile station and each base station to perform communication with the minimum transmission output. Further, by performing communication in the diversity state, it is possible to eliminate the instantaneous interruption at the time of handover that has occurred in the conventional time division multiple access (TDMA) or the like.

  The setting of a new branch by DHO is specially called “additional DHO” in DHO. Deletion of a communicating branch that does not contribute to communication in a diversity state is specifically called “deleted DHO” in DHO. In the case of performing addition DHO and deletion DHO, the candidate for additional DHO (referred to as “additional DHO candidate” or “additional branch candidate”) and the candidate for deletion DHO (referred to as “deletion DHO candidate” or “deletion branch candidate”) Is generally detected by the mobile station. When the mobile station detects a candidate for addition or deletion branch by monitoring the radio state (for example, propagation loss) of the perch of its own sector and surrounding sectors, the mobile station notifies the detected candidate to the network side. The network side executes DHO (additional DHO, deletion DHO) based on the notified candidate. The network side generally refers to an exchange station or a base station control station, but the function may be provided in the base station.

  The mobile station communicates with each base station using an individual radio link (radio branch) corresponding to each base station. The switching center has a wired link (wired branch) with each base station with which the mobile station is communicating, and signals from these base stations are handed over (Handover: HO) processing devices or diversity handover trunks. Selective synthesis in (Diversity Handover Trunk: DHT). The basic operation of the diversity handover branch is shown in Japanese Patent Application No. 9-508773, and the network configuration and the method of controlling the diversity handover trunk are shown in Japanese Patent Application No. 8-348900.

  Due to reasons such as hardware implementation, the upper limit of the number of wireless branches that can be set simultaneously by the mobile station (maximum number of wireless branches) and the upper limit of the number of wired branches that can be connected or processed simultaneously by the DHT in the switching center (maximum wired branches) Number) is set.

  The smaller of the maximum number of wireless branches and the maximum number of wired branches is the upper limit (the maximum number of communication branches) of the number of communication branches that can be set in the diversity state. In a normal system, priority is given to the effective use of radio resources, so the maximum number of radio branches is set as the maximum number of communication branches.

  However, in a conventional paper (the 1997 IEICE General Conference “Handover Device and Control Method in Next Generation Mobile Communication System”, Shimizu et al.) Etc., the control unit for the number of branches added and deleted is one branch. There is no discussion about the control in the case of handling a plurality of additional branches and deletion branches at the same time. Also not specified in FIF version 6.

  However, as described above, in the conventional technique, the control unit for the number of branches to be added and deleted is one branch. Therefore, in the case of N branch control, N times of control are required in principle. However, since the detection of branch candidates in the mobile station depends on the surrounding radio conditions, a plurality of deleted branch candidates and a plurality of additional branch candidates may be detected at the same time.

  Therefore, in such a case, the same control is repeated a plurality of times between the mobile station and the switching station, which is not only inefficient but also the above-described control until all handover control is completed. The extra time will be required.

  In the prior art, considering the additional DHO of one branch, the maximum number of wired branches is set to one branch more than the maximum number of wireless branches. Therefore, the network side can prepare a branch of a wired section in advance by one branch more than the maximum number of wireless branches. Therefore, even when adding one branch during communication with the maximum number of wireless branches, by adding a wired branch prepared in advance without deleting the branch in communication, additional DHO can be added only by switching wireless sections. It was possible to complete.

  However, in the method of setting the maximum number of wired branches by one more than the maximum number of wireless branches based on the conventional idea, when processing a plurality of additional branch candidates, the network side control is executed as many times as the number of additional branch candidates. As a result, there was a problem in performing efficient control. Furthermore, in the prior art, due to the fact that the control unit is one branch and the limit on the maximum number of wired branches, handling of additional branch candidates that are not added even in the wired section even though the DHO priority is higher than the branch in communication. Was not considered.

  Therefore, an object of the present invention is to provide a novel and useful diversity handover branch control method and the like.

  Another object of the present invention is to select a branch candidate by the mobile station in consideration of the maximum number of wired branches and the maximum number of wireless branches of the mobile station when a plurality of additional branch candidates and deletion branch candidates are detected in the mobile station. The present invention provides a method for controlling a diversity handover branch on the network side in a method and DHO execution.

  Another object of the present invention is to attempt to set one or more communicating branches for diversity handover in the order of monitored radio condition quality in a mobile communication system.

  Furthermore, another object of the present invention is that, in the mobile communication system, the cost of the resources of the wired section and the resources of the wireless section is high and valuable. This is to prevent unnecessary securing of radio resources by performing the procedure for securing resources.

  A first aspect of the present invention is a diversity handover control method in a mobile communication system including a mobile station, a plurality of base stations, and a center connected to the plurality of base stations, wherein the mobile station The radio state quality corresponding to a plurality of branches is monitored while communicating simultaneously with the base station, and information on the plurality of branches including one or more communicating branches and one or more additional branch candidates is notified to the center. Then, in the diversity handover control method in which the center receives information of the plurality of branches, whereby the mobile communication system performs diversity handover, the mobile station includes the one or more communicating branches and the 1 The above additional branch candidates are arranged in the order of the monitored radio condition quality, and the corresponding branch branch is in communication. In addition, the center notifies the center in the order in which the additional branch candidates are arranged, and the center uses the notified additional branch candidates in the order in which they are arranged to set one or more communicating branches for diversity handover. This is a diversity handover control method to be attempted.

  Here, each of the plurality of branches includes a radio branch between the mobile station and one of the base stations, and a wired branch between one of the base stations and the center, and the diversity handover control In the method, when setting a communicating branch, after setting a wired branch of the communicating branch, the wireless branch of the communicating branch can be set.

  Here, each of the plurality of branches includes a wireless branch between the mobile station and one of the base stations, and a wired branch between one of the base stations and the center, Based on the monitored radio condition quality, one or more deletion branch candidates are selected, and the mobile station notifies the center of information of a plurality of branches including the one or more deletion branch candidates. Using the notified deletion branch candidate, one or more communicating branches used for diversity handover are deleted, and the diversity handover control method performs the communication when deleting the communicating branch. After deleting the wireless branch of the middle branch, the wired branch of the communicating branch can be deleted.

  According to a second aspect of the present invention, in a mobile station that communicates simultaneously with a plurality of base stations at the time of diversity handover, means for monitoring radio state quality corresponding to a plurality of branches, one or more communicating branches, and 1 Means for notifying the center of information on the plurality of branches including the additional branch candidates, wherein the mobile station monitors the one or more communicating branches and the one or more additional branch candidates in the monitored radio status. The mobile station is arranged in the order of quality, and notifies the center in the order in which the branch in communication and the candidate for additional branch are arranged.

  According to a third aspect of the present invention, in a mobile communication system center connected to a plurality of base stations and communicating with the mobile stations via these base stations, the mobile stations are arranged in order of radio state quality. Using the means for receiving notification of one or more communicating branches and one or more additional branch candidates, and the notified additional branch candidates in the order in which they are arranged, the one or more communicating branches for diversity handover And a center having means for attempting setting.

  A fourth aspect of the present invention is a mobile communication system including a mobile station, a base station wirelessly connected to the mobile station, and an exchange station connected to the base station, wherein the mobile station includes the mobile station and the base A mobile communication system that communicates information of one or more additional branch candidates with the station and information indicating the priority order of the additional branch candidates to the switching center, and the switching center performs handover control based on the communicated information It is.

  Here, the information communicated from the mobile station to the switching center may further include information on one or more communicating branches between the mobile station and the base station.

  Here, the switching center includes information on one or more communicating branches between the mobile station and the base station, and one or more additional branch candidates between the mobile station and the base station with which the mobile station has been communicated. A communication branch between the mobile station and the exchange can be set using the information and information indicating the priority order of the additional branch candidates.

  Here, when the total of the number of branches in communication and the number of additional branch candidates exceeds the maximum number of wireless branches that can be set simultaneously in communication between the mobile station and the base station, Communication branches can be set in order from the communication branch with the highest priority, with the maximum number of wired branches that can be simultaneously processed by the switching center as an upper limit.

  According to a fifth aspect of the present invention, in a mobile communication system including a mobile station, a base station wirelessly connected to the mobile station, and an exchange station connected to the base station, communication is performed from the mobile station to the exchange station. The information is a mobile communication system including information of one or more deletion branch candidates between the mobile station and the base station.

  A sixth aspect of the present invention is a mobile communication system including a mobile station, a base station that is wirelessly connected to the mobile station, and an exchange station that is connected to the base station. It is a mobile communication system which performs the setting which deletes a branch.

  A seventh aspect of the present invention relates to a mobile station of a mobile communication system including a mobile station, a base station that is wirelessly connected to the mobile station, and an exchange station that is connected to the base station. The mobile station communicates information on one or more additional branch candidates between and information indicating the priority of the additional branch candidates to the exchange.

  Here, when the mobile station and the base station are communicating with the maximum number of radio branches that can be set simultaneously, the priority of the additional branch candidate to be added is set from the priority of the communicating branch with the lowest priority. If the predetermined threshold is exceeded, the addition of the additional branch candidate can be communicated to the exchange.

  Here, the information communicated from the mobile station to the switching center may further include information on one or more communicating branches between the mobile station and the base station.

  According to an eighth aspect of the present invention, in a mobile station of a mobile communication system including a mobile station, a base station wirelessly connected to the mobile station, and an exchange station connected to the base station, the mobile station to the exchange station The information to be communicated is a mobile station including information of one or more deletion branch candidates between the mobile station and the base station.

  According to a ninth aspect of the present invention, the mobile station detects an additional branch candidate to be a candidate for a handover in communication between the mobile station and a base station wirelessly connected to the mobile station, and the base station In the diversity handover branch control method for communicating to the switching station connected to the mobile station, the information communicated from the mobile station to the switching station includes one or more additional branch candidates between the mobile station and the base station. A diversity handover branch control method including information and information indicating the priority order of the additional branch candidates.

Here, the information communicated from the mobile station to the switching center may further include information on one or more communicating branches between the mobile station and the base station.
Here, the information indicating the priority order may be an arrangement order of the information on the communicating branch and the information on the additional branch candidate.

  Here, as the information indicating the priority order, the information on the branch in communication and the information on the candidate additional branch can be designated by a predetermined numerical value.

  Here, the information indicating the priority order may be an arrangement order of the information of the additional branch candidates.

  Here, the arrangement order may be the order of propagation loss.

  Here, as the information indicating the priority order, the information of the additional branch candidate can be designated by a predetermined numerical value.

  Here, the switching center determines information on one or more communicating branches between the mobile station and the base station, information on the one or more additional branch candidates communicated, and priority of the additional branch candidates. The communication branch between the mobile station and the switching center can be set using the information shown.

  Here, when the total of the number of branches in communication and the number of additional branch candidates exceeds the maximum number of wireless branches that can be set simultaneously in communication between the mobile station and the base station, Communication branches can be set in order from the communication branch with the highest priority, with the maximum number of wired branches that can be simultaneously processed by the switching center as an upper limit.

  Here, the maximum number of wired branches can be increased by N (N ≧ 1) more than the maximum number of wireless branches.

  Here, when the total number of branches in communication and the number of additional branch candidates exceeds the maximum number of wired branches, the mobile station is not added due to the upper limit of the maximum number of wired branches. The additional branch candidates can be determined again and communicated to the exchange.

  Here, when the additional branch candidate cannot be added due to the upper limit of the maximum number of wired branches, the switching center stores the branch candidate that could not be added due to the upper limit of the maximum number of wired branches, and is autonomous. The control can be executed.

  A tenth aspect of the present invention is a diversity handover branch control method in a mobile communication system including a mobile station, a base station wirelessly connected to the mobile station, and an exchange station connected to the base station. The information communicated from the mobile station to the switching station is a diversity handover branch control method including information on one or more deletion branch candidates between the mobile station and the base station.

  An eleventh aspect of the present invention is a diversity handover branch control method in a mobile communication system including a mobile station, a base station wirelessly connected to the mobile station, and an exchange station connected to the base station. The switching center is a diversity handover branch control method for setting one or more communication branches to be deleted.

  A twelfth aspect of the present invention is a diversity handover branch control method in a mobile communication system including a mobile station, a base station wirelessly connected to the mobile station, and an exchange station connected to the base station. This is a diversity handover branch control method in which the mobile station performs a setting for autonomously deleting one or more communication branches.

  A thirteenth aspect of the present invention is a diversity handover branch control method in which a mobile station detects a communication branch that is a candidate for a handover and communicates to an exchange station. The mobile station autonomously has one or more communication branches. Is a diversity handover branch control method in which the deleted branch is notified to the exchange via the remaining communication branch.

  A fourteenth aspect of the present invention is a diversity handover branch control method for detecting a communication branch that is a candidate for a deletion handover candidate in a mobile station, wherein the mobile station autonomously deletes one or more communication branches, This is a diversity handover branch control method in which the exchange station connected to the mobile station via the base station detects the wireless branch disconnection to delete the corresponding wired branch.

  In a fifteenth aspect of the present invention, the mobile station detects an additional branch candidate to be a candidate for a handover in communication between the mobile station and a base station wirelessly connected to the mobile station, and the base station In the diversity handover branch control method for communicating to the switching station connected to the mobile station, the mobile station is the maximum number of wireless branches in which the number of communicating branches between the mobile station and the base station can be set simultaneously. In this case, the information of the additional branch candidate that is not likely to be added as diversity handover is a diversity handover branch control method that does not communicate with the exchange.

  In a sixteenth aspect of the present invention, the mobile station detects an additional branch candidate to be a candidate for handover in communication between the mobile station and a base station wirelessly connected to the mobile station, and the base station In the diversity handover branch control method for communicating to the exchange station connected to the mobile station, the mobile station has a sum of the number of communicating branches and the number of additional branch candidates between the mobile station and the base station. This is a diversity handover branch control method for notifying an additional branch candidate to the exchange when the number of wireless branches that can be set simultaneously in communication is within the range.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 schematically shows a diversity handover branch control method according to an embodiment of the present invention.

  In FIG. 1, a mobile station (MS) 20 is a device that performs mobile communication and has a wireless communication function such as a mobile phone or a personal digital assistant, and includes base stations (BS) 10, 14, and Reference numeral 16 denotes a wireless station that performs wireless communication with the mobile station 20. Mobile station 20 initially communicates wirelessly with base stations 10, 14 and 16. A switching station (MSC) 30, 32, or 34 is connected to a base station 10, 12, 14, 16, or 18 by wire, and has a base station control function for performing radio control on the base station 10 and the like, and a base station 10 has a call control function for providing a communication service to the mobile station 20 or the like via the network 10 or the like. However, it goes without saying that the connection between the exchange station 30, 32 or 34 and the base station 10, 12, 14, 16 or 18 may be a fixed wireless connection as an alternative to the wired connection. One switching center can correspond to a plurality of base stations. As shown in FIG. 1, the base station 10 is double-wired to the exchanges 30 and 32 for the purpose of load distribution or active standby switching, but one base station is one exchange station in one communication unit. It is connected to the. When the mobile station 20 moves to the position of the mobile station 22 and a good radio condition with the base stations 12 and 18 is newly obtained, the base stations 12 and 18 become candidates for additional branches. Here, when the radio conditions of the base stations 10 and 14 deteriorate, the base stations 10 and 14 become deletion branch candidates. That is, even if an additional branch candidate is raised, a deleted branch candidate is not necessarily raised. The exchanges 30, 32, and 34 are connected by a relay network 40.

  Hereinafter, first, the types of DHO control used in the present invention will be described.

  The DHO is roughly classified into an add DHO, a delete DHO, and an add / delete DHO which is a special case of the add DHO. The added DHO is a DHO for newly adding a branch candidate, and the deleted DHO is a DHO for deleting a branch candidate in communication that does not contribute to communication. The control procedure for each DHO is described below.

(Additional DHO)
FIG. 2 shows an image of branch connection and release on the network side and mobile station side in each DHO.

  The additional DHO wireless branch connection / release image in FIG. 2 indicates that a wireless branch 52 is newly added at time 60 when there is a communicating branch 50. The wired branch connection / release image indicates that a new wired branch 54 has been added. The branch control order in the additional DHO is first the additional (wired) branch 54, and the next is the additional (wireless) branch 52.

  The mobile station selects the additional branch candidate from those satisfying the additional branch candidate determination condition, which is the detection condition of the additional branch candidate by the mobile station, by monitoring the radio state of the peripheral sector (for example, monitoring the propagation loss of the perch) To do.

  FIG. 3 shows an image of the added DHO threshold and the deleted DHO threshold. In FIG. 3, the vertical axis represents the degree of propagation loss, and the horizontal axis represents the distance traveled by the mobile station.

  As shown in FIG. 3, when the mobile station moves from left to right on the horizontal axis, the mobile station enters the diversity state in the DHO area and communicates in two branches. During this time, a handover (handover: HO) is performed. Communication is performed on one branch on the left side of the DHO area. Therefore, when entering the DHO area, one additional branch candidate appears during one-branch communication. When entering the right side from the DHO area, one deletion branch candidate appears during the two-branch communication. The mobile station detects an addition / deletion branch candidate based on the difference between the HO source BS propagation loss and the HO destination BS propagation loss (addition / deletion branch candidate determination condition). When this difference is smaller than the additional DHO threshold (when the additional branch candidate determination condition is satisfied), an additional branch candidate is detected, and when the difference is larger than the deletion DHO threshold (when the deleted branch candidate determination condition is satisfied). , Delete branch candidates are detected. When both DHOs (addition / deletion DHO) are communicating with a plurality of communication branches, the propagation loss of the branch with the smallest propagation loss is set as the HO source BS propagation loss as a criterion for determination. In this case, the deleted DHO threshold is made larger than the added DHO threshold, and a difference (hysteresis) is provided between the two thresholds so that the deleted DHO branch is not immediately added again due to a change in radio state.

  The mobile station arranges both the above-described additional branch candidate and the communicating branch in the order of the small propagation loss, for example, or sets the arbitrary order together with the information indicating the priority, and adds the additional information in the handover trigger signal. Include in the parameter and notify the network. If there is a deletion branch candidate, the deletion information parameter is similarly notified.

  It is also possible for the switching center to obtain information on the communicating branch by itself, and in this case, it is not necessary to send information on the communicating branch from the mobile station to the switching station.

  The information indicating the priority order may be the arrangement order of additional branch candidates as described above, or may be other absolute values, relative values, or the like. For example, a numerical value indicating a small propagation loss may be transmitted as a set together with information of each branch independently of the arrangement order.

  FIG. 4A shows an example of the format of the above-mentioned additional information parameter, and FIG. 4B shows an example of the format of the above-mentioned deletion information parameter.

  In FIG. 4A, the number of sectors in communication indicates the number of sectors that are in DHO communication when the mobile station transmits a handover trigger signal, and the number of additional DHO candidate sectors indicates the number of DHO candidate sectors that can be newly added. The station number indicates the number of a base station in DHO communication with a mobile station or the number of a base station that is a candidate for an additional branch, the sector number indicates the number of a sector in the base station, and the perch CH reception SIR value is the reception of a broadcast channel. The perch CH transmission power value indicates the SIR value and the transmission power value of the broadcast channel. As a parameter, a set of a base station number, a sector number, a perch CH reception SIR value, and a perch CH transmission power value is repeated only without adding the number of in-service sector sectors and the number of additional DHO candidate sectors.

  In FIG. 4B, the number of deleted DHO candidate sectors indicates the number of DHO candidate sectors that can be newly deleted, and a set of base station numbers and sector numbers is repeated by the number of deleted DHO candidate sectors as in FIG. 4A.

  FIG. 5 shows a DHO execution image viewed from the threshold.

  In FIG. 5, the branch in communication with the highest priority is the branch 110, and the next is the branch 112. The thresholds 120 and 122 are thresholds based on the branch 110 having the highest priority among the communication branches. The threshold 120 indicates a deletion DHO threshold and the threshold 122 indicates an additional DHO threshold. The network side takes out the number of branches that can be executed at the same time, taking into account the number of branches that are currently in communication, in order from the branch with the highest priority of additional DHO (in the order of branch 114, branch 116, branch 118). Execute. It is clear that the additional DHO branch candidate 114 has a smaller propagation loss than the communicating branch 110 and satisfies the additional branch determination condition. The branch 116 having a larger propagation loss than the branch 110 having the smallest propagation loss among the communicating branches is considered to be a branch having a higher priority due to the balance with the other branches 118. In other words, a high priority means that the branch is preferentially executed when added.

  The selection of branch candidates by the mobile station in the present invention means that the mobile station performs control so that candidates for which the additional DHO is not executed among the additional branch candidates detected by the mobile station are not notified to the network side. It is.

(Delete DHO)
The deleted DHO wireless branch connection / release image in FIG. 2 indicates that the wireless branch 72 is deleted at time 80 when there is a communicating branch 70. The wired branch connection / release image indicates that the wired branch 74 has been deleted. The branch control order in the deletion DHO is the deletion (wireless) branch 72 first, and the deletion (wired) branch 74 next.

  The mobile station monitors the radio state of the communicating sector (for example, monitors the propagation loss of the perch), so that all the mobile stations that satisfy the deletion branch candidate determination condition are set as deletion DHO candidates. The deletion DHO does not consider the DHO priority. In other words, because it does not contribute to communication, if it is detected, it is deleted immediately. The mobile station includes these deletion DHO candidates in the deletion information parameter in the handover trigger signal and notifies the network side. In the deletion information parameter, a combination of the number of deleted DHO sectors, the base station number and the sector number corresponding to the number of deleted DHO sectors is repeated (see the deletion information parameter format in FIG. 4B). As shown in FIG. 5, the network side executes the deletion DHO, for example, deletes the branch 113 of the deletion DHO candidate. However, since the deletion DHO always deletes it if it is detected as described above, a method can be adopted in which the mobile station autonomously deletes and notifies only the report to the network side.

(Additional deletion DHO)
It is an additional DHO that is executed based on the restriction on the maximum number of wireless branches. The additional DHO is activated when the total number of communicating branches and the number of additional branches exceeds the maximum number of wireless branches. The reason why the maximum number of wired branches is set to be larger than the maximum number of wireless branches is to effectively execute this additional deletion DHO. Addition / deletion DHOs with higher priority are added in order from the highest DHO priority to the maximum number of wired branches.

  FIG. 6 shows the relationship between the numbers of branches as seen from the network side.

  As shown in FIG. 6, the (transient) wired branch number 126 obtained by adding the additional branch number 127 to the communicating branch number 128 exceeds the maximum wireless branch number 125. The setting of the number of wired branches exceeding this (transitional number of wired branches 126−maximum number of wireless branches 125 = M) is transitional for efficient additional DHO. Eventually, on the network side (transitional), including the wired branch and the communicating branch, those with relatively low priorities (for example, those with large propagation loss) to M (where N ≧ M, where N = the maximum number of wired branches 124−the maximum number of wireless branches 125) is deleted. In the wireless section, the addition of a wireless branch and the switching of the wireless branch are performed corresponding to the finally selected wired branch. Even if a branch is added as a wired branch, a control method may be adopted in which the relative priority is lower than that of the branch in communication and no additional processing is performed for candidates that are known to be deleted due to trade-offs. Is possible.

  The addition / deletion DHO wireless branch connection / release image in FIG. 2 includes a branch 92 added at time 100 and a branch 91 deleted and switched at time 102 when there are communicating branches 90 and 91. This indicates that the branch 93 is additionally switched later. The point at time 102 of the branch 93 is a white circle because the maximum number of wireless branches is set to three. In the wired branch connection / release image, branches 96 (wired branch) and 98 (wired branch) are added, and branch 94 (wired branch) is deleted. The branch control order in the add / delete DHO is (1) add branch 96 and add branch 98, (2) add branch 92, (3) delete switch branch 91, (4) add switch branch 93, and (4) delete branch 94. is there.

  FIG. 7 is a flowchart illustrating details of the handover trigger signal transmission algorithm in the mobile station.

  In FIG. 7, the mobile station monitors the radio conditions of its own sector and neighboring sectors to detect additional branch candidates and deleted branch candidates (step S10). The mobile station sets a communicating branch and an additional branch candidate in the additional information parameter in the handover trigger signal, and further sets a deletion branch candidate in the deletion information parameter in the signal. However, the additional information parameter is set and transmitted under the following conditions (S20 to S90).

When there is a deletion branch candidate (step S20), all the communicating branches and additional branch candidates are included in the additional information parameter and transmitted (condition 1) (steps S40 and S50).
When there is no deletion branch candidate and the number of wireless branches in communication is not the maximum (step S30), all detected additional branch candidates are included in the additional information parameter and transmitted together with the communicating branch (condition 2) (step 2) S40, S50).

  When the number of wireless branches in communication is maximum (step S30), the mobile station compares whether the difference between the branch in communication and the candidate for additional branch is larger than a fluttering prevention threshold (for example, transmission loss is small). (Step S60), only the additional branch candidate larger than the flapping prevention threshold is included in the handover trigger signal and transmitted (Condition 3) (Steps S80 and S90), and if it is smaller, it is not transmitted (Step S70).

  When the number of wireless branches in communication is maximum, the first reason for making the candidate transmission conditions stricter as in Condition 3 is that the normal additional branch determination condition is satisfied, but priority is given to any other branch in communication This is because an additional branch candidate with a low rank (for example, a large propagation loss) is not notified to the network side as an additional branch candidate because it is known in advance that additional processing is not performed even if notified to the network side.

  FIG. 8 shows a case where additional branch candidates are not notified during maximum wireless branch communication.

  In FIG. 8, branches 130, 132, and 134 indicate communicating branches, and a threshold 142 indicates an additional DHO threshold. The additional branch candidates are the branches 136 and 138 that satisfy the additional branch candidate determination condition (difference in propagation loss with respect to the branch 130 is smaller than the additional DHO threshold 142). These two branches 136 and 138 are more than the branch 134 in communication. Are not expected to be added due to their low priority. Further, a flutter prevention threshold value is set, and by making this condition more strict, a branch is repeatedly added and deleted, that is, “flutter” is prevented (second reason). The branch deleted by the activation of the additional deletion DHO has only become relatively worse than the other branches, and is not deleted because the deletion branch candidate determination condition is satisfied. Even if a branch that meets the requirements of a communication branch and contributes to communication is replaced with an additional branch candidate with a slightly higher priority, it will soon be deleted again as an additional branch candidate due to a change in the radio section. The added branch will be added to the network. If this is repeated, the control load on the network increases, so a flutter prevention threshold is set to prevent flutter. Note that the flapping prevention threshold is used to determine the magnitude of the difference in consideration of the difference between the additional branch candidate and the communication branch having the lowest priority (for example, the propagation loss is large) during communication with the maximum number of wireless branches. Set as The addition is performed when the difference is larger than the flapping prevention threshold.

  9A and 9B are explanatory diagrams of the flapping prevention threshold value. FIG. 9A shows a case where additional branch candidates are added, and FIG. 9B shows a case where additional branch candidates are not added. An additional branch having a lower priority than the communication branch, that is, a lower priority than the communication branch having the lowest priority among the communication branches is not added because it is unlikely to be added. Even if the priority is a little higher, it will not be added because it causes the above fluttering.

  In FIG. 9A, branches 150, 152, and 154 indicate communicating branches, and a branch 156 indicates an additional branch candidate that exceeds the flapping prevention threshold 157.

  In FIG. 9B, branches 160, 162, and 164 indicate communicating branches, and a branch 166 indicates additional branch candidates within the flapping prevention threshold 167.

  When there is a deletion branch candidate and when the number of communication branches is not the maximum, all candidates are notified to the network. Even if the network rejects DHO of an additional branch candidate for some reason, it is an alternative. This is for notifying additional branch candidates.

  However, it goes without saying to those skilled in the art that this control may be a control for adding only additional branch candidates that are surely added. Even if it is added as a wired branch that has already been pointed out, the relative priority is lower than that of the branch that is in communication, and for the candidates that are known to be deleted due to the tradeoff, the addition process of the wired branch is performed. It is the same as described above that it is possible to set the control to be no control.

  FIG. 10 is a flowchart for explaining the details of the DHO execution algorithm in the network.

In FIG. 10, when the network side receives the handover trigger signal (step S100), the deletion DHO is executed first (step S110), and after completion thereof, the additional DHO is executed (step S130). This deletion DHO sequence (step S200) is executed to execute the deletion DHO prior to the addition DHO and release the branches that do not contribute to communication, thereby increasing the number of branches that can be executed simultaneously with the addition DHO. is there. When the mobile station autonomously executes the deletion DHO, the deletion DHO can be executed independently of the execution of the additional DHO performed by receiving the handover trigger. However, prior to the trigger for the additional DHO, It is desirable to execute. The execution procedure of the additional DHO is such that the sum of the number of branches in communication (#Br) −the number of deleted DHO branches (#Del) (that is, the number of branches in communication after completion of deletion DHO) and the number of additional DHO branches (#Add) is the maximum. The case is divided depending on whether the number of radio branches (#Br _max ) is exceeded.

First, when the sum (# Br− # Del + # Add) of the number of communicating branches and the candidate for additional branch does not exceed the _maximum number of wireless branches (#Br _max ), additional DHO is executed according to a normal procedure (additional DHO sequence S210). Steps S120 and S130).

If the sum of the number of branches in communication and the candidate for additional branch (# Br− # Del + # Add) exceeds the maximum number of wireless branches (#Br _max ), an additional deletion DHO (addition / deletion DHO sequence S220) is executed. Wired branches are added with the maximum number of wired branches as a limit (step S140). Next, wireless branches are added and switched with the maximum number of wireless branches (#Br _max ) as a limit (step S150). Finally, unnecessary wired branches exceeding the maximum number of wireless branches (#Br _max ) are released (step S160).

  FIG. 11 shows a branch diagram for starting the DHO sequence.

  In FIG. 11, branch 1 (190), branch 2 (191), and branch 3 (196) are communicating branches, and branch 3 (196) is a branch outside the delete DHO threshold 194. Branch 4 (192) and branch 5 (193) are additional branch candidates, branch 5 (193) is within the additional DHO threshold 195, and branch 4 (192) has a higher priority than branch 2 (191). Show.

  FIG. 12A, FIG. 12B, and FIG. 12C are diagrams that are connected in this order. FIG. 12A shows a DHO processing sequence in which the branch priority is as shown in FIG. However, the case where the maximum number of wireless branches is 3 and the maximum number of wired branches is 4 is shown.

  FIG. 12A shows a delete DHO sequence, indicating that unnecessary radio branch 3 is being deleted.

  In FIG. 12A, it is shown that there are three wireless branches, wireless branches 1 to 3, three wired branches, wired branches 1 to 3, and five base stations with base station numbers 1 to 5. The mobile device 500 detects an additional DHO candidate / deleted DHO candidate (501), and determines an additional DHO candidate / deleted DHO candidate (505). A handover trigger request (branch deletion, branch addition) is sent from the mobile station 500 to the network 503 (510). The network 503 extracts a deletion DHO candidate (517), and a handover execution request (branch 3 deletion) is sent to the mobile device 500 (515). The mobile device 500 returns a handover execution response to the network 503 (520). In the mobile device 500, the wireless branch 3 is deleted (525), and the maximum ratio combining of the wireless branch 3 is stopped (530). This suspension of maximum ratio combining is indicated by the disappearance of the line of wireless branch 3 at 530 as indicated by the dotted line.

  A wireless and wired bearer release request (535) is sent from the network 503 to the base station of base station number 3. The base station with base station number 3 stops receiving the uplink radio channel CH (540), stops transmitting the downlink radio channel (545), releases the base station number resource (550), A wired bearer release response (560) is returned. The network 503 deletes the DHT wired branch 3 (565).

  12B and 12C show the addition / deletion DHO sequence. In the addition / deletion DHO sequence, after adding the wired branches 4 and 5 in advance, the addition of the wireless branch 4 corresponding to the added wired branch and the switching of the wireless branches 1 and 5 are executed. Delete 1

  In FIG. 12B, the network 503 detects an additional DHO candidate (600), determines an additional DHO destination (605), and adds wired branches 4 and 5 (610). The addition of the wired branches 4 and 5 is indicated by the fact that the lines of the wired branch 4 and the wired branch 5 in FIG. 12B appear from positions indicated by dotted lines from 610. Wireless and wired bearer setting requests (615, 620) are sent from the network 503 to the base station of the base station number 4 and the base station of the base station number 5, respectively. Downlink radio CH transmission start (625, 630) is sent from the base station of base station number 4 and the base station of base station number 5 to mobile device 500, respectively. The base station with the base station number 4 and the base station with the base station number 5 receive the uplink radio CH reception start (635, 640), respectively. Wireless and wired bearer setting responses (645, 650) are sent from the base station with the base station number 4 and the base station with the base station number 5 to the network 503, respectively.

  In FIG. 12C, the network 503 confirms the wired branches 4 and 5. A handover execution request (addition of branch 4, switching between branches 1 and 5) (705) is sent from network 503 to mobile device 500, and a handover execution response (710) is returned from mobile device 500 to network 503. The mobile device 500 adds the wireless branch 4 (715), establishes synchronization of the new branch 4 (720), starts maximum ratio synthesis of the wireless branch 4 (725), and switches between the wireless branches 1 and 5 (730). The synchronization of the new branch 5 is established (735). On the other hand, in the network 503, the wired branches 4 and 5 are added (727). The base station with the base station number 4 performs uplink wireless CH synchronization detection (740), and returns a wireless and wired bearer setting response to the network 503 (745). The base station with the base station number 5 performs uplink wireless CH synchronization detection (750), and returns a wireless and wired bearer setting response to the network 503 (755). The network 503 confirms the addition of the wireless branch 4 and the switching between the wireless branches 1 and 5 (757), and sends a wireless and wired bearer release request to the base station of the base station number 1 (760). The base station with the base station number 1 stops receiving the uplink radio CH (765), stops transmitting the downlink radio CH (770), releases the base station number resource (775), and transmits the radio to the network 503. A wired bearer release response is returned (780). The network 503 deletes the DHT wired branch 1 (785).

  In the following, control of candidates that are not added due to the limitation on the number of wired branches (maximum number of wired branches) despite being notified to the network side as additional branch candidates will be described. Since the maximum number of branches that can be processed by one network control is the maximum number of wired branches, if the sum of the number of communicating branches and the number of additional branch candidates exceeds the maximum number of wired branches, the branch that is communicating In some cases, a branch having a higher priority than that of a branch cannot be added by one control.

  FIG. 13 shows a candidate example that is not added due to the limitation on the maximum number of wired branches.

  In FIG. 13, branches 170, 172, and 174 are communicating branches, and branches 176, 178, and 180 indicate additional branch candidates. The branches 178 and 180 have a higher priority than the communicating branch 170, but since the maximum number of wired branches is 4, only the additional candidate branch 176 having the highest priority is added, and the additional candidate branches 178 and 180 are added. Not.

  An example of the control in this case is a method of notifying the network that the additional branch candidates 178 and 180 that have not been added are included in the handover trigger signal again by measurement on the mobile station side. On the network side, when the handover trigger signal including the additional branch candidates 178 and 180 is received again, additional DHOs that cannot be added by the first control may be executed. As another method, the additional branch candidates 178 and 180 are stored on the network side, and after completing the series of operations shown in FIG. A method for performing additional DHO may be selected.

  According to the present invention, the mobile station selects branch candidates in consideration of the maximum number of wired branches and the maximum number of wireless branches, so that branch candidates that are not DHO-executed even if notified to the network side are previously notified to the network side. . However, in this case, there are the following two methods.

  First, in consideration of the case where the addition of an additional branch candidate having a high priority is not executed on the network side for some reason, it is expected that an additional branch candidate that has not been added will be added. If there are no additional branch candidates, the network side is notified for replacement. As a result, all the additional branch candidates are notified. However, during communication with the maximum number of communication branches, control is performed so as not to notify the network side of additional branch candidates having a lower priority than the branch in communication. This is because, since the number of communication branches is already the maximum, a branch having a lower priority than the communicating branch cannot be added.

  Secondly, instead of notifying the alternative additional branch candidate, only the additional branch candidate that is considered to be added when the DHO processing is executed normally is notified to the network. This method can reduce the amount of signal compared to the first method, but the mobile station needs to consider the relationship between the number of communication branches and the number of deletion branch candidates. That is, since the deletion DHO is executed first, it is necessary to control to select only additional branch candidates that are considered to be surely added after the deletion DHO is executed.

  In the present invention, the mobile station does not include only the additional branch candidate in the notification signal (handover trigger signal), but includes both the additional branch candidate and the communicating branch in the handover trigger signal together with information indicating the priority. Notify the side. For example, the magnitude of the propagation loss is used as a guideline for the priority order, and stored in the notification signal in the order of priority order. Since the deletion branch candidate is a branch that does not contribute to communication, if it is detected, it may be deleted. Therefore, it is not necessary to indicate the priority and notify the network side together with the branch in communication. The network side can compare the priorities of the communicating branch and the additional branch candidate, so it is possible to determine which additional branch candidate is added and which communicating branch is left or deleted as necessary. .

  In the mobile station, a plurality of additional branch candidates and a plurality of deletion branch candidates, that is, all DHO candidates are included in one handover trigger signal and notified to the network. Specifically, the additional branch candidate is included in the additional information parameter in the handover trigger signal, and the deleted branch candidate is included in the deletion information parameter. Needless to say, the communicating branch is included in the additional information parameter together with the additional branch candidate. As a result, the number of handover trigger transmissions can be reduced, and radio resources can be used effectively. On the network side, in order to avoid complication of processing, the additional branch candidate and the deletion branch candidate are separated and each DHO is executed sequentially. Regarding the execution order, the deletion DHO is executed first. By executing deletion DHO first and deleting unnecessary branches, more additional branch candidates can be added by one-time transmission using a handover trigger signal, and wireless and wired resources can be used effectively.

  When the deletion DHO is executed under the initiative of the mobile station, the mobile station includes the deletion branch candidate in the handover trigger signal and notifies the network side and releases the radio branch. The network receives the detected deletion branch candidate's wireless disconnection and releases the corresponding wired branch.

  FIG. 14 shows a delete DHO sequence led by a mobile device. Additional DHO is performed independently of this sequence.

  By setting the maximum number of wired branches by N (N ≧ 1) more than the maximum number of wireless branches, more wired branches than when setting the maximum number of wired branches by one more than the maximum number of wireless branches. Can be added in advance. Thereby, it is possible to efficiently control the addition of a plurality of additional branch candidates.

  In the above control, there may be an additional branch candidate in which no wired branch is added due to the limitation of the maximum number of wired branches. In the present invention, the following two methods can be provided as control in this case.

  1. No special control is performed on the network side. In the state where the mobile station is using a new communication branch, an additional branch candidate is determined again, notified to the handover trigger signal network again, and additional DHO for the unexecuted portion is executed.

  2. On the network side, additional branch candidates that could not be executed by one control are stored, and the second control is executed autonomously.

  FIG. 15 shows an embodiment of connection of a base station, a switching center, etc. in the present invention.

  In FIG. 15, base stations BS1 (200) and BS2 (210) are connected to a switching center MSC200, and a switching center MSC220 includes a diversity handover trunk DHT230, a voice encoding device VXC240, a data service control device DSC250, and A processor PRC 260 is connected.

  FIG. 16 shows another embodiment of connection of a base station, a switching center, etc. in the present invention.

  In FIG. 16, components having the same functions as those in FIG. The connection form of FIG. 16 differs from the connection form of FIG. 15 in that a base station control station MSC1 (320) having a function of controlling a base station is newly added, and an exchange station MSC2 (330) having a normal exchange function. It is a point connected to. The base station control station MSC1 (320) can be installed in the vicinity of the base station BS1 or BS2. The switching center MSC2 (330) can also use a fixed network switching center as it is. DHT 230 and PRC 260 are connected to base station control station MSC1 (320), and VXC 240, DSC 250 and PRC 260 are connected to switching center MSC2 (330).

  As described above, according to the present invention, a novel and useful diversity handover branch control method and the like are provided.

  According to the diversity handover branch control method of the present invention, when a plurality of additional branch candidates and deletion branch candidates are detected in the mobile station, the mobile station considers the maximum number of wired branches and the maximum number of wireless branches. By performing selection, it is possible to provide a diversity handover branch control method in DHO execution.

  In the mobile communication system, it is possible to try setting one or more communicating branches for diversity handover in the order of the monitored radio condition quality.

  Furthermore, in the mobile communication system, the cost of the wireless section resource and the wireless section resource is high and valuable, so the procedure for securing the wireless section resource should be performed after securing the wired section. As a result, it is possible to prevent uselessly securing radio resources.

It is the schematic explaining the diversity handover branch control method which is one embodiment of the present invention. It is a figure which shows the image of the branch connection of the network side in each DHO, and the mobile station side, and releasing. It is a figure which shows the image of an addition DHO threshold value and a deletion DHO threshold value. It is a figure which shows the format of an additional information parameter. It is a figure which shows the format of a deletion information parameter. It is a figure which shows the DHO execution image seen from the threshold value. It is a figure which shows the relationship of each branch number seen from the network side. 5 is a flowchart illustrating details of a handover trigger signal transmission algorithm in a mobile station. It is a figure which shows the case where an additional branch candidate is not notified during maximum wireless branch communication. It is explanatory drawing of the threshold value for flapping prevention when an additional branch candidate is added. It is explanatory drawing of the threshold value for flapping prevention when an additional branch candidate is not added. It is a flowchart explaining the detail of the DHO execution algorithm in a network. It is a branch figure which starts a DHO sequence. FIG. 12 is a diagram illustrating the relationship between FIGS. 12A, 12B, and 12C. 12A, 12B, and 12C are connected in this order. FIG. 12 is a diagram showing a DHO processing sequence when the mobile station is in a wireless state as shown in FIG. 11. FIG. 12 is a diagram showing a DHO processing sequence when the mobile station is in a wireless state as shown in FIG. 11. FIG. 12 is a diagram showing a DHO processing sequence when the mobile station is in a wireless state as shown in FIG. 11. It is a figure which shows the candidate example which is not added by the restriction | limiting of the maximum number of wired branches. It is a figure which shows a deletion sequence. It is a figure which shows one Embodiment of the connection of the base station in this invention, an exchange, etc. It is a figure which shows other embodiment of the connection of the base station in this invention, an exchange, etc.

Claims (5)

A diversity handover control method in a mobile communication system including a mobile station, a plurality of base stations, and a center connected to the plurality of base stations, wherein the mobile station communicates simultaneously with the plurality of base stations, The radio condition quality corresponding to a plurality of branches is monitored, and further, information on the plurality of branches including one or more communicating branches and one or more additional branch candidates is notified to the center. In a diversity handover control method for receiving branch information, whereby the mobile communication system performs diversity handover,
The mobile station arranges the one or more communicating branches and the one or more additional branch candidates in the order of the monitored radio state quality, and notifies the center in the order in which the communicating branch and the additional branch candidates are arranged. And
2. The diversity handover control method according to claim 1, wherein the center attempts to set one or more communicating branches for diversity handover using the notified additional branch candidates in the order in which they are arranged. The diversity handover control method according to claim 1,
Each of the plurality of branches comprises a wireless branch between the mobile station and one of the base stations, and a wired branch between one of the base stations and the center;
The diversity handover control method is characterized in that, when setting a communicating branch, after setting a wired branch of the communicating branch, a radio branch of the communicating branch is set. The diversity handover control method according to claim 1,
Each of the plurality of branches comprises a wireless branch between the mobile station and one of the base stations, and a wired branch between one of the base stations and the center;
The mobile station selects one or more deletion branch candidates based on the monitored radio condition quality,
The mobile station notifies the center of information of a plurality of branches including the one or more deleted branch candidates,
The center deletes one or more communicating branches used for diversity handover using the notified deletion branch candidate,
In the diversity handover control method, when deleting a communicating branch, the wireless branch of the communicating branch is deleted, and then the wired branch of the communicating branch is deleted. In a mobile station that communicates with multiple base stations at the time of diversity handover,
Means for monitoring radio condition quality corresponding to multiple branches;
Means for notifying the center of information of the plurality of branches including one or more communicating branches and one or more additional branch candidates;
The mobile station arranges the one or more communicating branches and the one or more additional branch candidates in the order of the monitored radio state quality, and notifies the center in the order in which the communicating branch and the additional branch candidates are arranged. A mobile station characterized by: In a mobile communication system center that is connected to a plurality of base stations and communicates with a mobile station via these base stations,
Means for receiving notification from the mobile station of one or more communicating branches and one or more additional branch candidates arranged in order of radio quality;
And a means for attempting to set one or more communicating branches for diversity handover using the notified additional branch candidates in the order in which they are arranged.

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