JP2008022484A - Base station apparatus and communication distance control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optimize area arrangement in a mobile communication system adopting a cell system. <P>SOLUTION: The base station device 10 disposed adjacently with one or more other base station devices 10 includes: a receiving RF section 12 for sequentially receiving radio waves arriving at an antenna 11; a selection section 31 for selecting radio waves transmitted by the one or more other base station devices 10 from among radio waves sequentially received by the receiving RF section 12; and a communication distance control section 36 for controlling a communication distance of the relevant base station device 10 in accordance with reception power of the radio waves selected by the selection section 31. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a base station apparatus and a communication distance control method, and more particularly, to an area arrangement optimization technique in a cell system.

  Some mobile communication systems arrange base station device areas so as to form a cell shape. Such an area arrangement method is called a cell method. In the cell method, if the area arrangement is not optimized, the radio waves transmitted by the base station devices interfere with each other, and the radio waves transmitted by the base station device move. It may be difficult for the station device to receive. For this reason, it is desirable to optimize the area layout, but in many cases it is necessary to adjust the area over a wide range for optimization, and in practice it is actually necessary to perform optimization by manual setting work. difficult. In particular, it is almost impossible when additional base station devices are added one after another.

  Therefore, on the premise that the area arrangement is not optimized, several techniques for suppressing this interference have been proposed.

  One of them is a technique for narrowing the directivity of transmission radio waves in the direction in which the mobile station apparatus exists using an adaptive array antenna. According to this, since the base station apparatus transmits radio waves in a truly necessary direction, interference is reduced and the mobile station apparatus can easily receive the transmission radio waves of the base station apparatus.

The other is a technique for shifting the transmission timing for each base station apparatus. In this case, since the transmission timing is different, no interference occurs. Patent Document 1 describes an example of this technique.
Japanese Patent Application Laid-Open No. 07-264659

  However, in recent years, the amount of communication has increased due to the increase in subscribers and the adoption of flat-rate methods such as packet flat-rate and call flat-rate, and it has become difficult to suppress interference by the above technologies. . That is, even if base station apparatuses are added one after another, the probability of interference increases even if the directivity of the transmission radio wave is reduced. In addition, a sufficient margin is required for the band to shift the transmission timing, but the margin is almost lost.

  Therefore, it is required not only to rely on each of the above technologies but also to realize a technology that can optimize the area arrangement even in an environment where the amount of communication is increasing, thereby suppressing interference.

  Accordingly, one of the objects of the present invention is to provide a base station apparatus and a communication distance control method capable of optimizing the area arrangement in a mobile communication system employing a cell system.

  A base station apparatus according to the present invention for solving the above problems is a base station apparatus arranged adjacent to one or more other base station apparatuses, and receiving means for receiving radio waves arriving at an antenna; A selection means for selecting one of the radio waves received by the reception means transmitted by the one or more other base station apparatuses, and the base station apparatus according to the received power of the radio waves selected by the selection means Communication distance control means for controlling the communication distance.

  According to this, when it is estimated that there is another base station device nearby, for example, the communication distance of the base station device can be controlled. The placement can be optimized.

  In the base station apparatus, the communication distance control means controls the power of the transmission radio wave from the base station apparatus in accordance with the reception power of the radio wave selected by the selection means, so that the base station apparatus The communication distance may be controlled.

  According to this, area arrangement can be optimized by transmission power control.

  Also, in each of the above base station devices, when the base station device is requested to start communication from the mobile station device, the receiving state determines whether or not a radio wave having a predetermined reception power or higher is received by the receiving means And a communication start availability determination unit that determines whether communication with the mobile station apparatus can be started according to a determination result of the reception state determination unit, wherein the communication distance control unit includes the selection unit. The communication distance of the base station apparatus may be controlled by setting the value of the predetermined reception power in accordance with the reception power of the radio wave selected by.

  According to this, in the carrier sense performed by the reception state determination unit and the communication start availability determination unit, even if a transmission radio wave of another base station device is received, communication is performed by the communication start availability determination unit due to the presence of the radio wave. It is possible to prevent the start from being rejected.

  Further, in each of the above base station apparatuses, the communication distance control means acquires the arrival direction of the radio wave together with the reception power of the radio wave selected by the selection means, and based on the acquired arrival direction, the base station apparatus The communication distance may be controlled for each direction from the base station apparatus.

  According to this, since the area can be controlled with respect to the arrival direction of the radio wave selected by the selection means (that is, the direction in which the other base station device exists), the area arrangement with the other base station device is possible. Can be optimized.

  A communication distance control method according to the present invention is a communication distance control method for controlling a communication distance of a base station apparatus arranged adjacent to one or more other base station apparatuses, and arrives at an antenna. A reception step of receiving radio waves; a selection step of selecting one of the radio waves received in the reception step transmitted by the one or more other base station devices; and a reception power of the radio wave selected in the selection step And a communication distance control step for controlling the communication distance of the base station apparatus.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a system configuration and functional blocks of a base station apparatus 10 according to the present embodiment. The base station device 10 is a computer having a CPU and a memory. The CPU is a processing unit for executing a program stored in the memory, and performs processing for controlling each unit of the base station apparatus 10 and implements each functional unit described later. The memory stores programs and data for carrying out the present embodiment. It also operates as a work memory for the CPU.

  Moreover, the base station apparatus 10 is configured to be capable of wireless communication with a mobile station apparatus that is within a reachable range of radio waves emitted from each other. This wireless communication is multiplexed by a time division multiplexing method, a frequency multiplexing method, a space division multiplexing method, and a time division duplex method.

  An area within the above distance from the base station apparatus 10 is called an area of the base station apparatus 10. In the cell-type mobile communication system, a plurality of base station devices 10 are used so as to eliminate as much as possible the range where the mobile station device cannot communicate. That is, the base station devices 10 are arranged adjacent to each other so that the mobile station device can communicate with at least one of the base station devices 10. As a result, the area of each base station apparatus 10 forms a cell shape.

  FIG. 2 (1) shows an example of areas constituting the cell shape. In the figure, base station apparatuses 10-1 to 7 are shown. The mobile station devices 20-1 and 2 are located in the area of the base station device 10-1, and can wirelessly communicate with the base station device 10-1.

  Here, consider a case where the base station apparatus 10-8 is added. FIG. 2B is an example in which the base station apparatus 10-8 is added between the base station apparatus 10-1 and the base station apparatus 10-4 in FIG. In this case, the mobile station apparatuses 20-1 and 2 can wirelessly communicate with both the base station apparatus 10-1 and the base station apparatus 10-8, while the base station apparatus 10-1 and the base station apparatus 10-8 Interference between transmitted radio waves is likely to occur. In addition, the base station device 10-8 receives a radio wave emitted from the base station device 10-1. Since this radio wave becomes an interference wave when communicating with the mobile station device 20, communication performed by the base station device 10-8 with the mobile station device 20 may be hindered. Specifically, in the carrier sense performed by the base station device 10-8 at the start of communication, since the radio wave emitted by the base station device 10-1 is received, it is determined that “communication cannot be started because there is another radio wave” It may be done.

  In this embodiment, in such a case, the base station device 10-8 autonomously narrows the own station area. As a result, the mobile station device 20-1 becomes incapable of wireless communication with the base station device 10-8, but interference between radio waves transmitted by the base station device 10-1 and the base station device 10-8 is suppressed. . In addition, the base station apparatus 10-8 performs communication with the mobile station apparatus 20 by preventing the radio waves generated by the base station apparatus 10-1 from being recognized as “other radio waves” in the carrier sense. Make sure that is not disturbed. Below, the function of the base station apparatus 10 for realizing these will be described in detail.

  As shown in FIG. 1, the base station apparatus 10 includes an antenna 11, a reception RF (Radio Frequency) unit 12, a reception BB (Base Band) processing unit 13, a transmission BB processing unit 14, and a transmission RF unit 15, and further functions. Specifically, a detection unit 30, a selection unit 31, an RSSI (Received Signal Strength Indicator) storage unit 32, a reception state determination unit 33, a carrier sense threshold storage unit 34, a communication start availability determination unit 35, and a communication distance control unit 36 are included. Composed. The communication distance control unit 36 includes a carrier sense threshold update unit 37 and a transmission power control unit 38 therein.

  The antenna 11 is an adaptive array antenna composed of a plurality of antenna elements. The reception RF unit 12 sequentially receives radio waves arriving at the antenna 11, converts them into signals in the baseband frequency band, and outputs them to the reception BB processing unit 13. Also, the reception RF unit 12 calculates a reception weight indicating the amount of difference in frequency and phase between signals received by each antenna element for each mobile station apparatus 20 that has transmitted the signal. The reception BB processing unit 13 demodulates the input signal to acquire communication data, and outputs the communication data to a communication processing unit (not shown).

  The transmission BB processing unit 14 receives an input of communication data to be transmitted to a specific mobile station apparatus 20 from a communication processing unit (not shown), converts it to a signal in the baseband frequency band, amplifies it, and transmits the transmission RF unit 15. Output to. The transmission RF unit 15 converts the input signal into a signal of a radio frequency band, amplifies it, and further calculates the transmission based on the reception weight calculated by the reception RF unit 12 for the destination mobile station apparatus 20 of the signal. After multiplying the weight, it is output to the antenna 11. The antenna 11 sends the input signal as a radio wave from each antenna element to the wireless section. The radio wave transmitted at this time has directivity based on the transmission weight.

  The detection unit 30 periodically detects a radio wave received by the antenna 11 over a predetermined detection period, and acquires reception power (RSSI) and phase for each frequency component and each antenna element. Furthermore, the detection unit 30 acquires the arrival direction of the radio wave based on the received power and phase for each antenna element acquired in this way. In addition, it is suitable for the detection part 30 to acquire an arrival direction with the resolution of the grade which divides 360 degrees around the said base station apparatus 10 into 4 (or 8).

  Based on the detection result of the detection unit 30, the selection unit 31 selects a radio wave sequentially transmitted by the reception RF unit 12 and transmitted by another base station device 10. Specifically, for the combination of the frequency and the direction of arrival in which the radio wave having a predetermined reception power or higher and a constant reception power is constantly (or at a frequency equal to or higher than a predetermined value) over the detection period, It is determined that it is transmitted by the above, and is selected. Then, the received power is stored in the RSSI storage unit 32 in association with the frequency direction information indicating the frequency and the arrival direction.

  The radio wave transmitted by another base station apparatus 10 may include a known signal (UW, Unique Word). In this case, the base station device 10 also holds this UW, calculates the correlation between the radio wave and the UW held, and if the correlation value is equal to or greater than a predetermined value, It is determined that the data is transmitted by the base station apparatus 10.

  The communication distance control unit 36 controls the communication distance of the base station apparatus 10 according to the received power stored in the RSSI storage unit 32. Further, the communication distance control unit 36 controls the communication distance of the base station device 10 for each direction from the base station device 10 based on the arrival direction of the radio wave selected by the selection unit 31. More specifically, this control by the communication distance control unit 36 is performed by two types of processing, that is, transmission power control and carrier sense threshold setting. Hereinafter, each process will be described.

  First, transmission power control will be described.

  The transmission power control unit 38 controls the transmission power of the base station apparatus 10 according to the reception power stored in the RSSI storage unit 32. Here, the transmission power is controlled by controlling the amplification factors of the amplifiers provided in the transmission BB processing unit 14 and the transmission RF unit 15.

  More specifically, the transmission power control unit 38 acquires frequency direction information stored in association with received power. Then, the transmission radio wave transmitted with directivity with respect to the arrival direction indicated by the acquired frequency direction information at the frequency indicated by the acquired frequency direction information is reduced by a predetermined amount. Thereby, the area of the base station apparatus 10 is narrowed. This is because the radio waves of the base station device 10 do not reach far.

  Next, carrier sense threshold setting will be described. In the following description, carrier sense will be described first, and then carrier sense threshold setting will be described.

  The carrier sense threshold value storage unit 34 stores a carrier sense threshold value that is an arbitrary power value in association with each of a plurality of direction information indicating each direction from the base station apparatus 10.

  The communication start availability determination unit 35 receives a communication start request from the mobile station device 20 and causes the reception state determination unit 33 to determine a reception state described later.

  The reception state determination unit 33 determines whether a radio wave equal to or higher than the carrier sense threshold is received by the reception RF unit 12 (reception state) when the mobile station device 20 requests communication start. This radio wave includes those transmitted by other base station devices 10 and other mobile station devices 20.

  Specifically, when a communication start request is received from the mobile station device 20, the reception state determination unit 33 acquires direction information indicating the arrival direction from the received power at each antenna element. Then, the carrier sense threshold stored in the carrier sense threshold storage unit 34 is acquired in association with the acquired direction information, and it is determined whether or not radio waves equal to or greater than the acquired carrier sense threshold are received by the reception RF unit 12. To do.

  The communication start availability determination unit 35 determines whether communication with the mobile station apparatus 20 that has requested the start of communication can be started according to the determination result of the reception state determination unit 33. Specifically, when the determination result of the reception state determination unit 33 indicates that a radio wave equal to or higher than the carrier sense threshold is received by the reception RF unit 12, the communication start availability determination unit 35 judge. On the other hand, if it indicates that it has not been received, it is determined that communication can be started.

  When it is determined that the communication can be started, the communication start availability determination unit 35 allocates a channel to the mobile station apparatus 20 that has requested the communication start, and transmits a channel allocation request indicating the allocated channel to the mobile station apparatus 20. On the other hand, when it is determined that the communication is not started, a channel assignment impossibility indicating that a channel is not assigned is transmitted to the mobile station apparatus 20. Carrier sense is performed as described above. In addition, the mobile station apparatus 20 that has received the channel assignment request starts communication on the assigned channel. On the other hand, the mobile station apparatus 20 that has received the message indicating that channel assignment is not possible transmits a communication start request to the other base station apparatus 10.

  The carrier sense threshold update unit 37 controls the communication distance of the base station apparatus 10 by setting the carrier sense threshold according to the reception power of the radio wave selected by the selection unit 31. Specifically, the carrier sense threshold update unit 37 acquires direction information indicating an arrival direction indicated by frequency direction information (referred to as setting target frequency direction information) stored in the RSSI storage unit 32. Then, the carrier sense threshold stored in the carrier sense threshold storage unit 34 in association with the acquired direction information is updated with a value equal to or higher than the received power stored in the RSSI storage unit 32 in association with the setting target frequency direction information. . As a result of this processing, radio waves emitted from other base station devices 10 are not recognized as “other radio waves” in carrier sense.

  Each process described above will be described in more detail with reference to the process flow of the base station apparatus 10.

  FIG. 3 is a diagram showing a processing flow of carrier sense threshold setting. As shown in the figure, the base station apparatus 10 performs all slot reception (reception in all combinations of frequencies and time slots (slots)), and acquires the electric field strength (reception power) of each slot (S1).

  Next, the base station apparatus 10 has an electric field strength in each of directions (direction i (i = 1 to 4 to 8)) obtained by dividing 360 ° around the base station apparatus 10 into 4 to 8. (I) is acquired (S2). Here, the electric field strength (i) is the electric field strength of the component arriving from the direction i in the received radio wave.

  The base station apparatus 10 stores the carrier sense threshold value (i) for each direction i, and compares them with the electric field strength (i) (S3). As a result, if the carrier sense threshold (i) is smaller, the carrier sense threshold (i) is increased (S4). Specifically, it is desirable that the carrier sense threshold (i) is the electric field strength (i). On the other hand, if the carrier sense threshold (i) is larger, the carrier sense threshold (i) is lowered (S4). However, if the carrier sense threshold (i) is lowered too much at this time, it will be determined that communication starts or not with only a little noise in the carrier sense. Therefore, a lower limit of the carrier sense threshold (i) is set in advance. It is desirable to keep it.

  When the processes of S3 to S5 are completed for all directions (i) (S6), the base station apparatus 10 returns to the operating state (S7). Then, if carrier sense NG (communication start / no decision) frequently occurs, the process returns to S1 again and the above process is performed to review the carrier sense threshold (S8).

  FIG. 4 is a diagram illustrating a processing flow of transmission power control. As shown in the figure, the base station apparatus 10 first performs the processes of S1 and S2.

  Next, the base station apparatus 10 determines whether or not the radio wave received from the direction i is transmitted by another base station apparatus 10 (whether or not the signal is transmitted within the same system). judge. Specifically, the radio wave transmitted by the other base station apparatus 10 includes a known signal (UW). The base station apparatus 10 holds the UW, calculates the correlation between the radio wave and the UW held, and when the correlation value is equal to or greater than a predetermined value, the received radio wave is transmitted to another base station. It is determined that it is transmitted by the station apparatus 10 (S10).

  As a result of this determination, if it is determined that the transmission is made by another base station apparatus 10, the base station apparatus 10 compares the carrier sense threshold (i) with the electric field strength (i) (S11). If it is determined that it has not been transmitted by another base station apparatus 10, the process proceeds to S15.

  If the carrier sense threshold (i) is smaller as a result of the comparison in S11, the transmission power (i) when transmitting the radio wave in the direction i is lowered, and the process proceeds to S15 (S13). On the other hand, if the carrier sense threshold (i) is larger, it is determined whether or not the transmission power (i) is smaller than the maximum standard value (S12). If the transmission power (i) is smaller than the maximum standard value, the transmission power is increased (S14). If the transmission power (i) is equal to or greater than the maximum standard value, no special process is performed, and the process proceeds to S15.

  When the processes of S10 to S15 are completed in all directions (i) (S15), the base station apparatus 10 returns to the operation state.

  As described above, according to the base station apparatus 10, for example, when it is estimated that there is another base station apparatus 10 nearby, the communication distance of the base station apparatus 10 can be controlled. In a mobile communication system that employs the method, the area arrangement can be optimized. Specifically, the area arrangement can be optimized by transmission power control.

  Further, even when a transmission radio wave of another base station apparatus 10 is received when performing carrier sense, it is possible to prevent the start of communication from being denied due to the presence of the radio wave.

  Furthermore, since the area can be controlled with respect to the direction of arrival of radio waves transmitted by another base station apparatus 10 (that is, the direction in which the other base station apparatus 10 exists), between the other base station apparatuses 10 Thus, the area arrangement can be optimized.

It is a figure which shows the system configuration | structure and functional block of the base station apparatus concerning embodiment of this invention. It is a figure which shows the example of the area which comprises the cell shape concerning embodiment of this invention. (1) shows an initial state, (2) shows a state in which base station devices are added in the initial state, and (3) shows a state in which the communication distance of the added base station device is controlled. It is a figure which shows the processing flow of the carrier sense threshold value setting concerning embodiment of this invention. It is a figure which shows the processing flow of transmission power control concerning embodiment of this invention.

Explanation of symbols

  10 base station apparatus, 11 antenna, 12 reception RF section, 13 reception BB processing section, 14 transmission BB processing section, 15 transmission RF section, 20 mobile station apparatus, 30 detection section, 31 selection section, 32 RSSI storage section, 33 reception State determination unit, 34 carrier sense threshold storage unit, 35 communication start availability determination unit, 36 communication distance control unit, 37 carrier sense threshold update unit, 38 transmission power control unit.

Claims (5)

A base station device arranged adjacent to one or more other base station devices,
Receiving means for receiving radio waves arriving at the antenna;
Selecting means for selecting one transmitted by the one or more other base station devices from radio waves received by the receiving means;
A communication distance control means for controlling the communication distance of the base station apparatus according to the received power of the radio wave selected by the selection means;
A base station apparatus comprising: The base station apparatus according to claim 1,
The communication distance control means controls the communication distance of the base station apparatus by controlling the power of the transmission radio wave from the base station apparatus according to the reception power of the radio wave selected by the selection means.
A base station apparatus. In the base station apparatus according to claim 1 or 2,
The base station device
A reception state determination unit that determines whether or not a radio wave having a predetermined reception power or higher is received by the reception unit when a communication start is requested from the mobile station device;
A communication start availability determination unit that determines whether communication with the mobile station apparatus can be started according to a determination result of the reception state determination unit;
Further including
The communication distance control means controls the communication distance of the base station apparatus by setting the value of the predetermined reception power according to the reception power of the radio wave selected by the selection means;
A base station apparatus. In the base station apparatus in any one of Claims 1 thru | or 3,
The communication distance control unit obtains the arrival direction of the radio wave together with the reception power of the radio wave selected by the selection unit, and determines the communication distance of the base station device from the base station device based on the obtained arrival direction. Control for each direction,
A base station apparatus. A communication distance control method for controlling a communication distance of a base station device arranged adjacent to one or more other base station devices,
A receiving step for receiving radio waves arriving at the antenna;
A selection step of selecting, from the radio waves received in the reception step, those transmitted by the one or more other base station devices;
A communication distance control step for controlling the communication distance of the base station apparatus according to the reception power of the radio wave selected in the selection step;
The communication distance control method characterized by including.

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