JP2010010968A - Base station and antenna group switching method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a base station which can be switched adaptively in accordance with the number of accommodation users, and to provide an antenna group switching method. <P>SOLUTION: The base station characteristically includes: a plurality of antennas 218; an antenna group switching part 236 which switches current antenna groups to be utilized in radio communication among a plurality of antenna groups consisting of a part or the whole of the plurality of antennas; a monitoring part 222 of the number of stored users which monitors the number of stored users which is the number of communication terminals under communication at present; a base station memory 212 which stores the number of storable users to be determined corresponding to the number of antennas as a table 213 of the number of storable users; and a current antenna group determination part 220 which instructs that an antenna group having the minimum number of storable users exceeding the number of stored users is considered as a current antenna group to the antenna group switching part 236. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a base station and an antenna group switching method for dynamically switching a current antenna group used for wireless communication in order to perform wireless communication using an adaptive array system with a plurality of antennas.

  In recent years, communication terminals represented by PHS (Personal Handy phone System) and mobile phones have become widespread, making it possible to make calls and obtain information regardless of location or time. Especially in recent years, the amount of available information has been increasing, and high-speed and high-quality wireless communication systems have been introduced to download large amounts of data.

  In such wireless communication, it is necessary to duplicate signals in order to transmit and receive. Typical duplexing methods include TDD (Time Division Duplex) for switching between transmission and reception by time division and FDD (Frequency Division Duplex) for duplexing transmission and reception by changing the frequency. In addition, as a method for multiple access to communicate with a plurality of communication terminals at the same time, TDMA (Time Division Multiple Access) for switching a plurality of communication terminals by time division, FDMA (Frequency) for dividing a frequency band Typical examples include Division Multiple Access (frequency division multiple access) and CDMA (Code Division Multiple Access) that multiplies a different code for each communication terminal.

  For example, ARIB (Association of Radio Industries and Businesses) STD-28 (Non-Patent Document 1) is used as a PHS communication standard that has been conventionally used. Here, the TDMA-TDD system is adopted. In this communication standard, the base station transmits a control signal, and the mobile station (communication terminal) receives this signal to know the presence of the base station, perform location registration, and start communication. Is configured to do.

  Further, there is an adaptive array antenna technique that uses a plurality of antennas to control the directivity pattern as one means for improving communication quality while maintaining the communication speed.

  Such an adaptive array antenna technique is a technique for generating a composite wave by controlling the phases of radio waves transmitted from a plurality of antennas and controlling the traveling direction of the composite wave. Thus, radio waves can be transmitted in a predetermined direction, so that radio wave interference generated between base stations can be reduced and the transmission distance of radio waves can be extended.

  Specifically, by forming beamforming using adaptive array technology, radio waves can be focused in a predetermined direction, and by forming null steering, interference with other base stations can be minimized. It becomes possible. That is, if a communication terminal as a communication partner can be specified at a certain moment, it is possible to form beam forming in the direction of the specified communication terminal and to form null steering in a direction other than the direction of the specified communication terminal. Become.

  Conventionally, there is a technique for switching a plurality of antenna groups including a part or all of the plurality of antennas (for example, Patent Document 1). By switching antenna groups, the number of antennas used is changed, and the following effects are obtained.

  When the number of antennas used for one terminal is large, the communication quality is improved and the cover area is increased. However, the number of accommodated users per base station decreases. This is because if the number of antennas is increased, the resources of the base station are used accordingly.

When the number of antennas is small, the number of accommodated users per base station increases. However, the communication quality is lowered and the cover area is reduced.
ARIB RCR STD-28 (Association of Radio Industries and Broadcast Research and Development Center for Radio Systems) Japanese Patent No. 3326416

  However, since conventional antenna group switching is not performed adaptively, for example, although the call volume is small, the number of antennas used for one terminal is set small, and the cover area is reduced, On the contrary, although the number of antennas used for one terminal is set to be large and the cover area is increased, an environment in which the amount of calls is large and the user cannot be accommodated is generated.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a base station and an antenna group switching method capable of adaptively switching an antenna group of a base station including a plurality of antennas according to the number of accommodated users. It is said.

  In order to solve the above problems, a typical configuration of a base station according to the present invention is a current configuration used for radio communication among a plurality of antenna groups and a plurality of antenna groups including a part or all of a plurality of antennas. An antenna group switching unit that switches antenna groups, an accommodated user number monitoring unit that monitors the number of accommodated users, which is the number of currently communicating communication terminals, and a value representing communication quality that is determined according to the number of antennas is a predetermined threshold value Instructs the antenna group switching unit to make the current antenna group the antenna group having the minimum number of users that can be accommodated and the minimum number of users that can be accommodated, which is the maximum number of communication terminals capable of maintaining And a current antenna group determination unit.

  With the above configuration, the base station can accommodate the largest number of communication terminals within a range in which a value representing communication quality does not deteriorate below a predetermined threshold.

  The current antenna group selection unit may select that the antenna group having the maximum accommodable user number is the current antenna group when there is no antenna group having the accommodable user number exceeding the accommodating user number. In this case, the threshold value cannot be maintained, but it is for accommodating as many users as possible.

  The values representing the communication quality are as follows: Signal to Interference and Noise Ratio (SINR), Received Signal Strength Indicator (RSSI), Signal to Interference Ratio (SIR), and Signal to Noise (SNR). Ratio, bit error rate (BER), or frame error rate (FER).

  In order to solve the above-described problem, the present invention provides an antenna that dynamically switches a current antenna group used for wireless communication among a plurality of antenna groups including a part or all of a plurality of antennas provided in a base station. In the group switching method, the number of accommodated users, which is the number of communication terminals currently communicating, is monitored, and the number of accommodated users is the maximum number of communication terminals that can maintain a predetermined threshold value indicating the communication quality of the current antenna group. The current antenna group is characterized in that an antenna group having the smallest number of accommodable users exceeding the number of accommodable users is set as the current antenna group.

  When there is no antenna group having the maximum number of users that can be accommodated, the antenna group having the maximum number of users that can be accommodated may be the current antenna group.

  The component corresponding to the technical idea in the base station mentioned above and its description are applicable also to the said antenna group switching method.

  According to the present invention, it is possible to provide a base station that can accommodate as many users as possible while maintaining communication quality and a coverage area by adaptively switching the number of antennas according to the environment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

(Wireless communication system)
FIG. 1 is an explanatory diagram showing a schematic connection relationship of a wireless communication system to which a base station according to an embodiment of the present invention is applied. The wireless communication system 100 includes base stations 110A and 110B, PHS terminals 120A and 120B, a communication network 130 including an ISDN (Integrated Services Digital Network) line, the Internet, a dedicated line, and the like, and a relay server 140. Consists of.

  In the wireless communication system 100, when a user connects a communication line from his / her PHS terminal 120A to another PHS terminal 120B, the PHS terminal 120A performs an open search and has the best communication quality within the communicable range. A wireless connection request is made to the base station 110A. The base station 110A that has received the wireless connection request requests the relay server 140 to establish a communication connection with the communication partner via the communication network 130, and the relay server 140 refers to the location registration information of the PHS terminal 120B to determine another PHS terminal. For example, the base station 110B within the wireless communication range of 120B is selected to secure a communication path between the base station 110A and the base station 110B, and communication between the PHS terminal 120A and the PHS terminal 120B is established.

  In such a wireless communication system 100, various techniques are employed to improve the communication speed and communication quality between the base station 110A and the PHS terminal 120A or between the base station 110B and the PHS terminal 120B. In the present embodiment, for example, ARIB STD-28 is adopted, and wireless communication based on the TDMA-TDD scheme is executed between the base station and the PHS terminal.

  Hereinafter, specific configurations and operations of the base stations 110A and 110B in the wireless communication system 100 will be described. In the following embodiments, since base stations 110A and 110B have the same configuration, the configuration of base station 110A will be described as a representative.

(base station)
FIG. 2 is a functional block diagram showing a hardware configuration of the base station 110A of FIG. The base station 110A includes a base station control unit 210, a base station memory 212, a base station wireless communication unit 214, a base station wired communication unit 216, a plurality of antennas 218, a accommodated user number monitoring unit 222, and transmission data. A generation unit 224 and a reception data processing unit 226 are included.

  The base station control unit 210 manages and controls the entire base station 110A using a semiconductor integrated circuit including a central processing unit (CPU). In addition, the base station control unit 210 controls communication connection of the PHS terminal 120A to the communication network 130 and other PHS terminals 120B using a program in the base station memory 212. The base station memory 212 includes ROM, RAM, EEPROM, nonvolatile RAM, flash memory, HDD, and the like, and stores programs processed by the base station control unit 210, time information, and the like.

  The base station memory 212 stores the number of users that can be accommodated, which is the maximum number of communication terminals that can maintain a predetermined threshold as a value representing the communication quality, which is determined according to the number of antennas used among the plurality of antennas 218. is doing. This is stored as a storable user number table 213 in which the number of antennas and the number of storable users are associated with each other.

  The base station wireless communication unit 214 establishes communication with the PHS terminal 120 via the antenna 218 and transmits / receives data. The base station wired communication unit 216 can be connected to various servers including the relay server 140 via the communication network 130.

  The base station wireless communication unit 214 includes an antenna group switching unit 236 that switches a current antenna group used for wireless communication among a plurality of antenna groups including some or all of the plurality of antennas 218.

  The antennas 218 are grouped. For example, when the number of antennas included in one antenna group can be two, four, or eight, the number of used antennas is 1, A few groups are formed.

  In the data reception processing, the base station radio communication unit 214 performs waveform processing for each antenna group, demodulates the data demodulation unit 234, and bit-processes the reception data in the reception data processing unit 226.

  In the data transmission process, a transmission frame is generated by the transmission data generation unit 224, modulated by the data modulation unit 232, and subjected to waveform processing for each antenna group by the base station radio communication unit 214 and transmitted.

  In the data transmission / reception process, the accommodated user number monitoring unit 222 monitors the accommodated user number, which is the number of communication terminals currently communicating.

  In the present embodiment, the base station control unit 210 also functions as the current antenna group determination unit 220. The current antenna group determination unit 220 acquires the number of accommodated users from the accommodated user number monitoring unit 222, and determines an appropriate current antenna group by the determination process of FIG. When switching the current antenna group, the antenna group switching unit 236 is instructed via the accommodated user number monitoring unit 222.

(Antenna group switching method)
FIG. 3 is a flowchart showing determination processing performed by the current antenna group determination unit 220 of FIG. FIG. 3 is broadly divided into a determination 300 for determining whether to increase the antenna number level and a determination 400 for determining whether to decrease the antenna number level.

  First, the current antenna group determination unit 220 determines whether or not the current antenna number level is smaller than the highest antenna number level (step S310). As a result, if it is small, that is, if there is room to increase the antenna number level, the current antenna group determination unit 220 acquires the current accommodated user number from the accommodated user number monitoring unit 222 and refers to the accommodable user number table 213. Then, it is determined whether or not the current number of accommodated users is smaller than the number of users that can be accommodated at the antenna number level one level higher (step S320). As a result, if it is smaller, the current antenna group determination unit 220 instructs the antenna group switching unit 236 to switch to the antenna number level one level higher (step S330). Then, determination 300 is repeated.

  If the maximum number of antennas has been reached in step 310, the process proceeds to decision 400. First, it is determined whether or not the current antenna number level is greater than the lowest antenna number level (step S410). As a result, when it is large, that is, when there is room to lower the antenna number level, the current antenna group determination unit 220 determines whether or not the current number of accommodated users is equal to or greater than the number of users that can be accommodated at the current antenna number level. (Step S420). As a result, in the above case, the current antenna group determination unit 220 instructs the antenna group switching unit 236 to perform switching to the antenna number level one level lower (step S430). Decision 400 is then repeated.

  With the above processing, the current antenna group determination unit 220 finally instructs the antenna group switching unit 236 to set the antenna group having the minimum number of users that can be accommodated exceeding the number of accommodated users as the current antenna group. Become.

  That is, the base station 110A can accommodate the largest number of communication terminals within a range in which a value representing communication quality does not deteriorate below a predetermined threshold.

  In this embodiment, as shown in step S420, the antenna group is switched after the current number of accommodated users exceeds the number of users that can be accommodated in the current antenna group. However, such switching is determined with a margin in advance. It's okay. That is, if it is about to exceed, it is preferable to lower the antenna number level in advance and increase the number of users that can be accommodated.

  If the result is NO in step S410, that is, if the current antenna number level is the lowest antenna number level and there is no antenna group having an accommodable number of users exceeding the current number of accommodated users, the maximum accommodation You may choose to make the antenna group with the number of possible users (the lowest antenna number level) the current antenna group. This is to accommodate as many users as possible.

  The flowchart of FIG. 3 is an example, and the determination order is not limited. That is, the determination 400 may be performed before the determination 300.

  The values representing the communication quality are as follows: Signal to Interference and Noise Ratio (SINR), Received Signal Strength Indicator (RSSI), Signal to Interference Ratio (SIR), and Signal to Noise (SNR). Ratio, bit error rate (BER), or frame error rate (FER). In addition, a bit error rate (BER) or a frame error rate (FER) may be used. The SIR includes a CI (Carrier Interface).

  FIG. 4 is a flowchart showing an example of a conventional antenna switching method. It is determined whether or not the communication environment of the user during a call has changed (step S10), and if it has changed, it is determined whether it has been improved or deteriorated (step S20). If improved, the mode is shifted to a predetermined antenna group mode and the number of antennas is decreased (step S40). When it deteriorates, it shifts to the all antenna mode using all antennas (step S30).

  As described above, conventionally, there is only an alternative of using all antenna groups or a predetermined antenna group. For example, the number of antennas is set to be small although the call volume is small, and the cover area is reduced. On the other hand, although the number of antennas was increased and the coverage area was increased, there was an environment where the amount of calls was large and the user could not be accommodated.

  The embodiment of the present invention solves such a problem and adaptively switches the number of antennas according to the environment, thereby maintaining a base station that can accommodate as many users as possible while maintaining communication quality and coverage area. It can be provided.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  INDUSTRIAL APPLICABILITY The present invention can be used for a base station and an antenna group switching method that dynamically switch a current antenna group used for wireless communication in order to perform wireless communication using an adaptive array system using a plurality of antennas.

It is explanatory drawing which showed the rough connection relation of the radio | wireless communications system to which the base station which is embodiment of this invention is applied. It is the functional block diagram which showed the hardware constitutions of the base station of FIG. It is a flowchart which shows the determination process which the current antenna group determination part 220 of FIG. 2 performs. It is a flowchart which shows an example of the conventional antenna switching method.

Explanation of symbols

110A ... Base station 212 ... Base station memory 213 ... Accommodable user number table 214 ... Base station radio communication unit 218 ... Antenna 220 ... Current antenna group determination unit 222 ... Accommodated user number monitoring unit 236 ... Antenna group switching unit

Claims (5)

Multiple antennas,
Among a plurality of antenna groups consisting of part or all of the plurality of antennas, an antenna group switching unit that switches a current antenna group used for wireless communication;
An accommodation user number monitoring unit for monitoring the number of accommodation users, which is the number of communication terminals currently communicating;
A memory that stores the number of users that can be accommodated, which is the maximum number of communication terminals that can maintain a predetermined threshold as a value representing communication quality, which is determined according to the number of antennas;
A current antenna group determination unit that instructs the antenna group switching unit to set the antenna group having the minimum number of users that can be accommodated exceeding the number of accommodated users as the current antenna group;
A base station comprising:   The current antenna group selection unit, when there is no antenna group having the number of users that can be accommodated exceeding the number of accommodated users, to select the antenna group having the maximum number of users that can be accommodated as the current antenna group. The base station according to claim 1, wherein:   The values representing the communication quality are signal to interference and noise ratio (SINR), received signal strength indicator (RSSI), signal to interference ratio (SIR), and signal to noise ratio (SNR). The base station according to claim 1, wherein the base station is a bit error rate (BER) or a frame error rate (FER). In an antenna group switching method for dynamically switching a current antenna group used for wireless communication among a plurality of antenna groups including a part or all of a plurality of antennas provided in a base station,
Monitor the number of accommodated users, which is the number of communication terminals currently communicating,
The number of accommodated users is compared with the number of accommodable users, which is the number of communication terminals that can maintain a predetermined threshold value indicating the communication quality of the current antenna group,
An antenna group switching method, wherein an antenna group having a minimum number of users that can be accommodated exceeding the number of accommodated users is set as the current antenna group.   5. The antenna group switching according to claim 4, wherein when there is no antenna group having an accommodable user number exceeding the accommodating user number, an antenna group having a maximum accommodable user number is set as the current antenna group. Method.

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