JP3917377B2 - Wireless communication system and synchronization acquisition control method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radio communication system using a CDMA (Code Division Multiple Access) system, and more particularly to a radio communication system having a cell configuration called an umbrella cell and a synchronization acquisition method thereof.
[0002]
[Prior art]
In a wireless communication system using a CDMA system, initial synchronization is usually acquired in the following three steps.
[0003]
First, the mobile station uses a single matched filter, for example, for a so-called initial synchronization code (PSC) common to all cells, and establishes slot synchronization with the cell receiving the strongest power (step 1).
[0004]
Next, the mobile station performs frame synchronization using a so-called second synchronization code (SSC) (step 2).
[0005]
Finally, the mobile station synchronizes pilot symbols using the scrambling code used by the cell (step 3).
[0006]
In the conventional system, codes (PSC, SSC) used in each cell are assigned by a radio network controller (RNC) that controls a plurality of base stations, and the PSC is common to all cells.
[0007]
[Problems to be solved by the invention]
However, the conventional system as described above has a problem that there is a possibility that a desired area synchronization cannot be obtained in a wireless communication system employing a cell configuration called a so-called umbrella cell. Hereinafter, this problem will be described in detail with reference to FIGS.
[0008]
FIG. 6 is a diagram schematically showing a plurality of cells under the supervision of the RNC that employs umbrella cells. An umbrella cell is a base station that covers one or a plurality of large areas and a base station that covers one or a plurality of narrow areas under the same RNC control. Each cell refers to a cell configuration that is completely contained in any cell of a base station covering a large area.
[0009]
Here, as an example, a base station that covers a wide area (in the figure, “broad BS” for simplification) 602 and a narrow area that covers a region that overlaps with a cell managed by this base station 602 are covered. It is assumed that an umbrella cell is formed by the base stations 603 and 604 (in the figure, “narrow BS” for simplification).
[0010]
Here, consider a case where a mobile station (MS) 601 located in the cell of the base station 603 (ie, also located in the cell of the base station 602) takes initial synchronization.
[0011]
In an umbrella cell, a base station that covers a wide area includes (1) an area that cannot be completely covered by a base station that covers a narrow area, and (2) communication of a base station that covers a narrow area. The original objective is to provide a complementary cover when the capacity has already reached the maximum allowable amount. If a mobile station located in a cell of a base station covering a wide area is connected with a base station that always covers a wide area with priority regardless of the communication status, the load on the base station increases. In addition, a mobile station located in a place where a line can only be connected to a base station that covers a wide area can cause a situation in which the line cannot be connected, leading to deterioration in line utilization efficiency. Furthermore, communication quality may be deteriorated due to a so-called “far / near problem” in CDMA wireless communication by unnecessarily communicating with a distant base station.
[0012]
Looking at the above example shown in FIG. 6 from such a viewpoint, it is the system that the mobile station 601 trying to establish the initial synchronization is synchronized with the base station 603 that covers the closest narrow area. Most preferred.
[0013]
However, in the conventional system, since the PSC (initial synchronization code) assigned to the base stations 602, 603, and 604 by the RNC is common, when the mobile station 601 tries to synchronize using the PSC, it is shown in FIG. Thus, the synchronization signal is detected for the signals from all the base stations.
[0014]
Further, since the base station 602 needs to cover the wide area and transmits the synchronization signal with higher power than the base stations 603 and 604 covering the narrow area, as shown in FIG. The synchronization signal from is the most correlated.
[0015]
As a result, the mobile station 601 is synchronized with the base station 602 instead of the desired base station 603. Therefore, if the communication capacity of the base station 603 has a margin, the line that should be connected to the base station 603 is connected to the base station 602, the load on the base station 602 increases, and the line of the entire system increases. Usage efficiency deteriorates.
[0016]
In order to solve this problem, if the transmission power of a base station that covers a large area is lowered, it is located in a cell of a base station that covers a large area and not in a cell of a base station that covers a narrow area. There may be a new problem that it becomes difficult to acquire synchronization of mobile stations.
[0017]
Also, in an umbrella cell, if a mobile station located in a cell of a base station covering a narrow area is always synchronized with the base station, the communication capacity of the base station has already reached the maximum allowable amount Another problem may arise that the mobile station cannot synchronize with a base station covering a wide area and cannot communicate.
[0018]
The present invention has been made to solve such a problem, and provides a wireless communication system in which a mobile station located in an umbrella cell can establish initial synchronization with a desired base station most preferable in the system. Objective.
[0019]
[Means for Solving the Problems]
A wireless communication system according to a first aspect of the present invention has a predetermined communication area, and includes at least one first base station that communicates with a mobile station, and a communication area that is narrower than the predetermined communication area. In a wireless communication system having at least one second base station that communicates with a mobile station so as to overlap a communication area of one base station, priority order setting means for setting a priority order for the base station, A configuration is adopted in which the mobile station control means controls the mobile station so that the station tries to acquire synchronization in order from the base station with the highest priority.
[0020]
According to this configuration, priority is set for the base station, and the mobile station tries to acquire synchronization according to the priority, and establishes synchronization with the base station with the highest priority as much as possible from the system side. It can be synchronized with a preferred base station. In other words, the system allows the mobile station to synchronize with a desired base station desired in the system as viewed from the system side. Therefore, the system can improve the line utilization efficiency of the entire system by controlling the priority order based on the line utilization state of the entire system.
[0021]
The wireless communication system according to a second aspect of the present invention employs a configuration in which, in the first aspect, the priority order setting means determines the priority order based on a traffic amount in a base station.
[0022]
According to this configuration, by monitoring the traffic volume at the base station, the load status applied to the base station is grasped, and the priority order is determined so that the load is distributed to the entire system. It is possible to solve the problem and improve the line use efficiency.
[0023]
The wireless communication system according to a third aspect of the present invention is the wireless communication system according to the first or second aspect, wherein the priority order setting means sets different priorities to the first base station and the second base station. The configuration to be taken
[0024]
According to this configuration, in a so-called umbrella cell, it is possible to prevent a line from being concentrated unnecessarily on a base station that covers a wide area, so that the load on the base station that covers a wide area increases unnecessarily. Can be prevented. Further, the mobile station does not unnecessarily communicate with a distant base station, and deterioration of communication quality due to a so-called perspective problem can be prevented.
[0025]
A wireless communication system according to a fourth aspect of the present invention is the wireless communication system according to any one of the first to third aspects, wherein the priority order setting unit does not change the set priority order to the mobile station. A configuration is adopted in which priority is ignored and synchronization with a predetermined base station is achieved.
[0026]
According to this configuration, it is possible to cause a specific mobile station to fall back on priority and synchronize with a base station designated on the system side. That is, when the line usage status changes, by not changing the priority order, the mobile stations other than the specific mobile station follow the priority order and only connect the connection destination of the specific mobile station to any base. Since control is performed so as to synchronize with the station, the line usage status can be arbitrarily controlled from the system side, and the line usage efficiency of the entire system can be optimized.
[0027]
The wireless communication system according to a fifth aspect of the present invention is the wireless communication system according to any one of the first to third aspects, wherein the priority order setting unit is provided in the wireless control device and includes the determined priority order. It has a priority control unit that generates a priority control signal and transmits it to each base station. The base station transmits a synchronization signal holding unit that holds a plurality of synchronization signals corresponding to the priority, and a radio control device. The priority order control signal received is read, the priority order set for the own station is read from the signal, the synchronization signal corresponding to the priority order is read from the synchronization signal holding unit, and the synchronization signal is transmitted to the mobile station A synchronization signal control unit, wherein the synchronization acquisition destination control means is provided in the mobile station and receives a signal from a plurality of base stations, and a synchronization signal holding unit that holds a plurality of synchronization signals corresponding to the priority order And the received signal The synchronization unit establishes synchronization with a base station in order from the synchronization signal corresponding to the highest priority, the detection unit for detecting the synchronization signal by correlating with the synchronization signal held for the first time, and the synchronization signal corresponding to the highest priority A configuration having a synchronization signal control unit set in the detection unit until the detection is performed.
[0028]
According to this configuration, a plurality of synchronization signals used for initial synchronization are prepared, each of which corresponds to the priority order, and the synchronization signal is held in advance by the base station and the mobile station. By assigning a different synchronization signal to each base station, it becomes possible to set a priority order to each base station. Also, the mobile station side can detect only the synchronization signal from the base station to which the synchronization signal is assigned by using the synchronization signal in order from the synchronization signal corresponding to the higher priority. Can be easily synchronized with the desired base station in the system.
[0029]
Furthermore, even if signals from a plurality of base stations are received, the type of transmitted synchronization signal is different, so it is possible to omit the process of comparing the reception levels after obtaining the correlation, and the time required to acquire synchronization is shortened. The
[0030]
The wireless communication system according to a sixth aspect of the present invention is the wireless communication system according to the fifth aspect, wherein the priority control unit generates a switching control signal for instructing a mobile station a synchronization signal used for synchronization signal detection, The synchronization signal control unit receives the switching control signal and reads the synchronization signal instructed by the signal from the synchronization signal holding unit. The configuration set in the detection unit is adopted.
[0031]
According to this configuration, by using the switching control signal as described above, a specific mobile station can be turned into a priority order and synchronized with a base station designated on the system side. That is, when the line usage status changes, the radio network controller does not change the priority order, and the mobile stations other than the specific mobile station follow the priority order, and the connection destination of the specific mobile station Therefore, it is possible to arbitrarily control the line usage status from the system side and to optimize the line usage efficiency in the entire umbrella cell.
[0032]
A synchronization acquisition control method according to a seventh aspect of the present invention includes a predetermined communication area, and includes at least one first base station that communicates with a mobile station, and a communication area that is narrower than the predetermined communication area. In a wireless communication system having at least one second base station that communicates with a mobile station so as to overlap the communication area of the first base station, a priority order setting step for setting a priority order to the base station; And a mobile station control step of controlling the mobile station so that the mobile station tries to acquire synchronization in order from the base station with the highest priority.
[0033]
According to this method, priority is set for the base station, and the mobile station tries to acquire synchronization according to the priority and establishes synchronization with the base station with the highest priority as much as possible from the system side. It can be synchronized with a preferred base station. In other words, the system allows the mobile station to synchronize with a desired base station desired in the system as viewed from the system side. Therefore, the system can improve the line utilization efficiency of the entire system by controlling the priority order based on the line utilization state of the entire system.
[0034]
In the synchronization acquisition control method according to an eighth aspect of the present invention, in the seventh aspect, the priority setting step adopts a method of determining the priority based on a traffic amount in a base station.
[0035]
According to this method, by monitoring the traffic volume at the base station, the load status applied to the base station is grasped, and the priority order is determined so that the load is distributed to the entire system. It is possible to solve the problem and improve the line use efficiency.
[0036]
The synchronization acquisition control method according to a ninth aspect of the present invention is the seventh or eighth aspect, wherein the priority order setting step assigns different priority orders to the first base station and the second base station. Use the setting method.
[0037]
According to this method, in a so-called umbrella cell, it is possible to prevent a line from being concentrated unnecessarily on a base station that covers a large area, so that the load on a base station that covers a large area increases unnecessarily. Can be prevented. Further, the mobile station does not unnecessarily communicate with a distant base station, and deterioration of communication quality due to a so-called perspective problem can be prevented.
[0038]
The synchronization acquisition control method according to a tenth aspect of the present invention is the synchronization acquisition control method according to any one of the seventh to ninth aspects, wherein the priority order setting step is performed by the mobile station without changing the set priority order. A method of ignoring the priority order and synchronizing with a predetermined base station is adopted.
[0039]
According to this method, it is possible to cause a specific mobile station to fall back on priority and synchronize with a base station designated on the system side. That is, when the line usage status changes, by not changing the priority order, the mobile stations other than the specific mobile station follow the priority order and only connect the connection destination of the specific mobile station to any base. Since control is performed so as to synchronize with the station, the line usage status can be arbitrarily controlled from the system side, and the line usage efficiency of the entire system can be optimized.
[0040]
The synchronization acquisition control method according to an eleventh aspect of the present invention is the synchronization acquisition control method according to any one of the seventh to ninth aspects, wherein the priority order setting step includes a priority that includes the determined priority order in the radio network controller. A priority control step of generating a priority control signal and transmitting it to each base station, and receiving a priority control signal transmitted from the radio controller at the base station, and setting the priority set in the own station from the signal A synchronization signal control step of reading and transmitting a synchronization signal corresponding to the priority order to the mobile station, wherein the synchronization acquisition destination control step receives signals from a plurality of base stations at the mobile station, A method including a detection step used for the synchronization signal detection processing for the received signal in order from the synchronization signal corresponding to the highest priority among the plurality of synchronization signals corresponding to the priority until the synchronization is established. That.
[0041]
According to this method, a plurality of synchronization signals used for initial synchronization are prepared, each of which corresponds to the above priority, and the base station and the mobile station hold these synchronization signals in advance. By assigning a different synchronization signal to each base station, it becomes possible to set a priority order to each base station. Also, since the mobile station side can detect only the synchronization signal from the base station to which the synchronization signal is assigned by using the synchronization signal corresponding to the higher priority in order, the system set by the system side It can be easily synchronized with the desired base station.
[0042]
A synchronization acquisition control method according to a twelfth aspect of the present invention is the synchronization acquisition control method according to the eleventh aspect, wherein the radio control apparatus generates a switching control signal instructing a synchronization code used for synchronization signal detection processing to the mobile station, A method is employed in which the mobile station receives the switching control signal and performs a synchronization signal detection process using the synchronization signal instructed by the signal.
[0043]
According to this method, by using the switching control signal as described above, a specific mobile station can be turned into a priority order and synchronized with a base station designated on the system side. That is, when the line usage status changes, the radio network controller does not change the priority order, and the mobile stations other than the specific mobile station follow the priority order, and the connection destination of the specific mobile station Therefore, it is possible to arbitrarily control the line usage status from the system side and to optimize the line usage efficiency in the entire umbrella cell.
[0044]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Each base station according to the present embodiment transmits an initial synchronization signal encoded with a different PSC.
[0045]
First, a schematic configuration of the entire system will be described with reference to FIG. FIG. 1 is a diagram schematically showing a plurality of cells under the supervision of an RNC that employs an umbrella cell. In this embodiment, as an example, a base station that covers a wide area (in the figure, “broad BS” for simplification) 102 and a region that overlaps with a cell that the base station 102 has jurisdiction over are set as the own cell. It is assumed that an umbrella cell is formed by base stations (in the figure, “narrow BS” for simplification) 103 and 104 covering a narrow area.
[0046]
As an example, as shown in the figure, the mobile station 101 is located in the cell of the base station 103, the mobile station 106 is located in the cell of the base station 104, and the mobile stations 107 and 108 are located in the cell of the base station 102. It shall be located in
[0047]
Further, the radio network controller (RNC) 105 assigns a different initial synchronization code to each base station. Details will be described later.
[0048]
Next, the configuration of the RNC 105 according to the present embodiment will be described with reference to FIG. FIG. 2 is a schematic configuration diagram schematically showing only the components of the RNC 105 related to the present invention. The RNC 105 includes a transmission / reception unit 201, a memory 202, and a priority order control unit 203.
[0049]
The transmission / reception unit 201 transmits a priority control signal, which will be described later, generated by the priority control unit 203 to each base station under the jurisdiction, receives information on the traffic volume from each base station, and sends it to the priority control unit 203. Forward. In the present embodiment illustrated in FIG. 1, the traffic amount is the communication amount and interference amount of the mobile stations 101, 106, 107, and 108.
[0050]
The memory 202 holds information on the maximum allowable communication capacity of each base station under the control of the RNC 105.
[0051]
The priority order control unit 203 compares the traffic amount of each base station under the jurisdiction with the maximum allowable communication capacity of each base station held in the memory 202, determines the priority order for each base station, Is transmitted as a priority control signal to each base station via the transmission / reception unit 201.
[0052]
Further, the priority control unit 203 increases the traffic volume of one base station (for example, the base station 103), and adjusts the traffic volume of another base station (for example, the base station 102) having the same area as the one base station as a cell. If there is room, the mobile station (for example, the mobile station 101) located in a place where it can synchronize with the base stations without changing the priority order of the base stations, A switching control signal for instructing synchronization is transmitted to each base station via the transmission / reception unit 201.
[0053]
Next, the configuration of the base station 300 according to the present embodiment will be described using FIG. FIG. 3 is a schematic configuration diagram schematically showing only the components of the base station 300 related to the present invention. Base station 300 includes transmission / reception unit 301, antenna 302, synchronization signal holding unit 303, and synchronization signal control unit 304.
[0054]
The transmission / reception unit 301 receives the priority control signal from the RNC 105 and transfers it to the synchronization signal control unit 303. A predetermined PSC is transmitted via the antenna 302. Further, the traffic volume (communication volume and interference volume) in the base station 300 is monitored and transmitted to the RNC 105. In addition, the switching control signal is received from the RNC 105 and transmitted via the antenna 302 to the mobile station instructed to switch the base station.
[0055]
The synchronization signal holding unit 303 is a memory, for example, and holds a plurality of types of PSCs. In the plurality of PSCs, an order corresponding to the priority order of the base stations with which the mobile station is synchronized is defined.
[0056]
The synchronization signal control unit 304 extracts a corresponding predetermined PSC from the synchronization signal holding unit 303 based on the priority order control signal from the RNC 105 received via the transmission / reception unit 301, and transmits via the transmission / reception unit 301 and the antenna 302. Send.
[0057]
Next, the configuration of the mobile station 400 according to the present embodiment will be described using FIG. FIG. 4 is a schematic configuration diagram schematically showing only the components of the mobile station 400 related to the present invention. The mobile station 400 includes a transmission / reception unit 401, an antenna 402, a synchronization signal control unit 403, a synchronization signal holding unit 404, and a synchronization signal detection unit 405.
[0058]
The transmission / reception unit 401 receives the synchronization signal and the switching control signal transmitted from the base station via the antenna 402.
[0059]
When initial synchronization is established, the detection code control unit 403 reads from the synchronization signal holding unit 404 in order from the PSC having the highest priority set, and sets it in the synchronization signal detection unit 405. In addition, once the synchronization is established, when the switching control signal instructs the RNC 105 to switch the base station to be synchronized, the PSC used in the newly synchronized base station is read from the synchronization signal holding unit 404, The synchronization signal detection unit 405 is set.
[0060]
The synchronization signal holding unit 404 is a memory, for example, and holds a plurality of types of PSCs corresponding to the priority order. The synchronization signal detection unit 405 is, for example, a matched filter, and obtains a correlation between the synchronization signal set by the synchronization signal control unit 403 and the received signal.
[0061]
Next, the operation of the mobile station initial synchronization acquisition method in the wireless communication system according to the present invention will be described with reference to an example shown in FIG.
[0062]
First, a priority order control signal for setting a priority order for each base station is generated by the priority order control unit 203 of the radio network controller (RNC) 105, and each base station 102, 103, And 104. When determining the priority order, the traffic volume at each of the base stations 102 to 104, that is, the communication volume and the interference volume of the mobile stations 101 and 106 to 108 is referred to, and the communication capacity of the base station covering a narrow area has a margin. For example, the priority order is determined so as to accept a line connection request from a mobile station with priority over a base station covering a wide area.
[0063]
Here, it is assumed that the highest priority (hereinafter referred to as priority 1) is set for the base stations 103 and 104, and the lowest priority (hereinafter referred to as priority 2) is set for the base station 102. And
[0064]
The priority order control signal containing the setting contents is received by the transmission / reception unit 301 of each base station and transferred to the synchronization signal control unit 302. The priority control signal is referred to when the synchronization signal control unit 302 reads from the synchronization signal holding unit 303 an initial synchronization signal (PSC) transmitted to the mobile station in the base station. That is, the synchronization signal control unit 302 reads a synchronization signal corresponding to the priority order set for the base station.
[0065]
In this example, the synchronization signal control unit 304 of the base stations 103 and 104 reads an initial synchronization signal (hereinafter referred to as PSC1) corresponding to the priority order 1 from the synchronization signal holding unit 303, and the spreading code control unit of the base station 102 304 reads an initial synchronization signal (hereinafter referred to as PSC 2) corresponding to priority 2 from the synchronization signal holding unit 303.
[0066]
Here, when the mobile station 101 located in the cell of the base station 103 starts the initial synchronization acquisition process, the PSC held in the synchronization signal holding unit 404 by the synchronization signal control unit 403 is sequentially changed according to the priority order. It is set to 405, and detection of the synchronization signal is tried in order. In this way, synchronization with the base station with the highest possible priority is established.
[0067]
Here, PSC1 is first set in the synchronization signal detection unit 405 by the synchronization signal control unit 403 of the mobile station, and an attempt is made to establish synchronization with the base station for which priority 1 is set. Then, the synchronization signal PSC1 transmitted from the base stations 103 and 104 can be detected, and synchronization with the base station 103 can be established from the level difference. Since the synchronization signal transmitted from the base station 102 is PSC2, it is not detected.
[0068]
As another case, when the remaining communication capacity of a base station covering a small area is small, priority order 1 can be set for the base station 102 and priority order 2 can be set for the base stations 103 and 104. In this case, the mobile station 101 is initially synchronized with the base station 102 that transmits the synchronization signal PSC1. As shown in FIG. 5, the synchronization signal PSC2 from the base stations 103 and 104 is not detected, and initial synchronization with these base stations is not established.
[0069]
In either case of the above two examples, the mobile station 101 can establish initial synchronization with a base station desirable in the system that optimizes line utilization efficiency in view of the traffic volume of each base station in the umbrella cell. it can.
[0070]
Further, in the above example in which priority order 1 is set for the base station 102, an increase in the traffic amount or interference amount of the base station 102 is recognized by the priority order control unit 202 of the RNC 105, and there is a margin in the communication capacity of the base station 103. Is generated, the priority control unit 202 generates a switching control signal from PSC1 to PSC2, and is transmitted to the base station 102 to which the mobile station 101 is connected via the transmission / reception unit 201, and further from the base station 102 to the mobile station 101.
[0071]
The synchronization signal control unit 403 of the mobile station 101 that has received the switching control signal switches the initial synchronization signal set in the synchronization signal detection unit 405 from PSC1 to PSC2, and newly resets the initial synchronization using PSC2. Here, the mobile station 101 newly establishes synchronization with the base station 103.
[0072]
By using the switching control signal in this way, the RNC 105 can change only the connection destination of a specific mobile station to another base station that forms an umbrella cell without changing the priority set in each base station. Therefore, even if the line usage status changes, the traffic amount of each base station can be controlled so that the line usage efficiency in the entire umbrella cell is optimized.
[0073]
In other words, once the initial synchronization is established, the mobile station changes the base station to be synchronized by the handover due to a decrease in the level of the synchronization signal and the handover by the priority change by the radio control device or the switching control signal. Communication will continue.
[0074]
In the above description, the case of determining the priority order based on the traffic volume in the base station has been described. However, the priority determination method may be arbitrary, and the line usage status in the entire system and the degree of load distribution / concentration Is preferably based on For example, it may be determined based on the remaining processing capability in the base station.
[0075]
Further, in the above embodiment, the case of a cell configuration called a so-called umbrella cell has been described. However, in the present invention, synchronization is acquired from the system side when the mobile station is located in a place where synchronization can be acquired with a plurality of base stations. Any system that designates the destination can be applied to a wireless communication system having another cell configuration.
[0076]
【The invention's effect】
  As described above, according to the wireless communication system according to claim 1 of the present invention, the mobile station can be synchronized with a desired base station desired in the system as viewed from the system side. The line utilization efficiency of the entire system can be improved.
  Further, in a so-called umbrella cell, it is possible to prevent lines from being concentrated unnecessarily at a base station that covers a wide area, so that it is possible to prevent an unnecessary increase in the load on a base station that covers a wide area. Further, the mobile station does not unnecessarily communicate with a distant base station, and deterioration of communication quality due to a so-called perspective problem can be prevented.
  AlsoBecause it is possible to reverse the priority order of a specific mobile station and synchronize with the base station specified by the system side, the system side can arbitrarily control the line usage status and optimize the line usage efficiency of the entire system. can do.
  Furthermore, it becomes possible to set the priority order to each base station by assigning a different synchronization signal for each base station, and even on the mobile station side, the synchronization signal is used in order from the synchronization signal corresponding to the higher priority order. Since only the synchronization signal from the assigned base station can be detected, it is possible to easily synchronize with a base station desired on the system set by the system side. Furthermore, even if signals from a plurality of base stations are received, the types of synchronization signals are different, so that the process of comparing the reception levels can be omitted, and the time required to acquire synchronization can be shortened.
[0077]
According to the wireless communication system of the present invention, the traffic concentration in the base station is monitored and the priority is determined so that the load is distributed over the entire system. Efficiency can be improved.
[0080]
  AlsoAnd claims of the present invention3According to the wireless communication system according to the present invention, it is possible to control a line usage state arbitrarily from the system side because a specific mobile station can be turned into a priority order and synchronized with a base station designated on the system side. Overall line utilization efficiency can be optimized.
[0081]
  Further, the claims of the present invention4According to the synchronization acquisition control method according to the above, since the mobile station can be synchronized with a desired base station desired in the system as viewed from the system side, the line utilization efficiency of the entire system can be improved. it can.
  Further, in a so-called umbrella cell, it is possible to prevent lines from being concentrated unnecessarily at a base station that covers a wide area, so that it is possible to prevent an unnecessary increase in the load on a base station that covers a wide area. Further, the mobile station does not unnecessarily communicate with a distant base station, and deterioration of communication quality due to a so-called perspective problem can be prevented.
  AlsoBecause it is possible to reverse the priority order of a specific mobile station and synchronize with the base station specified by the system side, the system side can arbitrarily control the line usage status and optimize the line usage efficiency of the entire system. can do.
  Furthermore, it becomes possible to set the priority order to each base station by assigning a different synchronization signal for each base station, and even on the mobile station side, the synchronization signal is used in order from the synchronization signal corresponding to the higher priority order. Since only the synchronization signal from the assigned base station can be detected, it is possible to easily synchronize with a base station desired on the system set by the system side. Furthermore, even if signals from a plurality of base stations are received, the types of synchronization signals are different, so that the process of comparing the reception levels can be omitted, and the time required to acquire synchronization can be shortened.
[0082]
  Further, the claims of the present invention5According to the synchronization acquisition control method according to the present invention, it is possible to eliminate load concentration and improve line utilization efficiency by monitoring the traffic volume at the base station and determining the priority order so that the load is distributed throughout the system. it can.
[0085]
  Further, the claims of the present invention6According to the synchronization acquisition control method according to the above, since it is possible to reverse the priority to a specific mobile station and synchronize with the base station specified by the system side, the line usage situation can be controlled arbitrarily from the system side, The line utilization efficiency of the entire system can be optimized.
[Brief description of the drawings]
FIG. 1 is a diagram schematically illustrating a plurality of cells under the supervision of an RNC that employs an umbrella cell.
FIG. 2 is a schematic configuration diagram schematically showing only components of the RNC 105 related to the present invention.
FIG. 3 is a schematic configuration diagram schematically showing only components related to the present invention of a base station 300;
4 is a schematic configuration diagram schematically showing only components related to the present invention of a mobile station 400. FIG.
FIG. 5 is a graph showing an example of a reception level of a synchronization signal from each base station detected in one mobile station in the system according to the present invention.
FIG. 6 is a diagram schematically illustrating a plurality of cells under the supervision of an RNC that employs an umbrella cell.
FIG. 7 is a graph showing an example of a reception level of a synchronization signal from each base station detected in one mobile station in a conventional system.
[Explanation of symbols]
101, 106, 107, 108 Mobile station
102 Base station covering a wide area
103, 104 Base station covering a small area
105 Radio Control Unit (RNC)
201 Transceiver
202 memory
203 Priority control unit
300 base station
301 transceiver
302 Antenna
303 Synchronization signal holding unit
304 Sync signal controller
305 Diffusion unit
400 mobile stations
401 transceiver
402 Antenna
403 Sync signal controller
404 Sync signal holding unit
405 Sync signal detector

Claims (6)

Having a predetermined communication area, having at least one first base station communicating with a mobile station, and having a communication area narrower than the predetermined communication area overlapping the communication area of the first base station; In a wireless communication system having at least one second base station communicating with a mobile station,
Priority setting means for setting different priorities for the first base station and the second base station;
Mobile station control means for controlling the mobile station so that the mobile station tries to acquire synchronization in order from the base station with the highest priority, and
The priority order setting means reduces the number of mobile stations that communicate with the higher priority base station of the first base station and the second base station, and sets the lower priority base station. When it is desired to increase the number of mobile stations that communicate with a station, it is possible to communicate with both the first base station and the second base station without changing the set priority, and the set priority is high. Configured to cause a mobile station communicating with a base station to ignore the priority and synchronize with a base station with a lower priority ,
The priority order setting means includes:
A priority control unit that is provided in the wireless control device, generates a priority control signal containing the determined priority, and transmits the priority control signal to each base station;
The base station
A synchronization signal holding unit that holds a plurality of synchronization codes corresponding to the priorities;
Receives a priority control signal transmitted from the radio controller, reads the priority set in the local station from the signal, reads a synchronization code corresponding to the priority from the synchronization signal holding unit, and transmits the synchronization code to the mobile station. A synchronization signal control unit for transmitting a synchronization code,
The synchronization acquisition destination control means is provided in a mobile station,
A synchronization signal holding unit that holds a plurality of synchronization codes corresponding to the priorities;
A detector that receives signals from a plurality of base stations, detects a synchronization code by correlating the received signal with a synchronization code held in advance;
A synchronization signal controller configured to set a plurality of synchronization codes corresponding to the priorities in order from the synchronization code corresponding to the highest priority until the synchronization with one base station is established. A wireless communication system. The wireless communication system according to claim 1,
The wireless communication system, wherein the priority setting means determines the priority based on a traffic amount in a base station. The wireless communication system according to claim 1 or 2 ,
The priority control unit generates a switching control signal that instructs a synchronization code used for synchronization signal detection to the mobile station, and transmits the switching control signal to the mobile station via a base station that performs radio communication with the mobile station,
The wireless communication system, wherein the synchronization signal control unit receives the switching control signal, reads a synchronization code instructed by the signal from the synchronization signal holding unit, and sets the synchronization code in the detection unit. Having a predetermined communication area, having at least one first base station communicating with a mobile station, and having a communication area narrower than the predetermined communication area overlapping the communication area of the first base station; A method of controlling synchronization acquisition with a base station by a mobile station in a wireless communication system having at least one second base station communicating with the mobile station, comprising:
A priority setting step for setting different priorities for the first base station and the second base station;
A mobile station control step of controlling the mobile station so that the mobile station attempts to acquire synchronization in order from the base station with the highest priority;
Of the first base station and the second base station, the number of mobile stations communicating with the higher priority base station set is reduced, and the number of mobile stations communicating with the lower priority base station is reduced. When it is desired to increase the number, it is possible to communicate with both the first base station and the second base station without changing the set priority, and communicate with the base station with the higher set priority. by ignoring the priority order to the mobile station it is, possess a switching control step to assume a lower base station and synchronization priority, and
The priority order setting step includes:
In the wireless control device, a priority order control step for generating a priority order control signal containing the determined priority order and transmitting it to each base station;
Synchronization signal control in the base station that receives the priority control signal transmitted from the radio controller, reads the priority set in the local station from the signal, and transmits a synchronization code corresponding to the priority to the mobile station A process,
The synchronization acquisition destination control step includes:
In the mobile station, signals are received from a plurality of base stations, and from the synchronization code corresponding to the highest priority among the plurality of synchronization codes corresponding to the priority, the reception is sequentially performed until synchronization with one base station is established. A synchronization acquisition control method , comprising: a detection step used for synchronization signal detection processing for a signal . The synchronization acquisition control method according to claim 4 , wherein
In the priority order setting step, the priority order is determined based on a traffic amount in a base station. The synchronization acquisition control method according to claim 4 or 5 ,
A radio control device generates a switching control signal that instructs a synchronization code used for synchronization signal detection processing to the mobile station, and transmits the switching code to the mobile station via a base station that performs radio communication with the mobile station,
A synchronization acquisition control method, wherein a mobile station receives the switching control signal and performs a synchronization signal detection process with a synchronization code indicated by the signal.

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