Radio base station, radio base station monitoring system, transmission power setting method of radio base station, program, and recording medium

The present invention relates to a radio base station, a radio base station monitoring system, a transmission power setting method of the radio base station, a program and a recording medium, and in particular, a transmission for minimizing interference between radio signals of an indoor base station and an outdoor base station. It is about the technology about power setting.

In a mobile communication network, a wide area is generally divided into small zones called wireless cells, and one wireless base station is deployed for each of about 1 to 10 wireless cells. Radio base stations are classified into outdoor base stations installed on dedicated steel towers and rooftops of buildings with good visibility conditions, and indoor base stations that mainly cover the inside of one building. The wireless cell of an outdoor base station varies depending on the installation environment such as urban areas and suburbs, and the radius of the wireless cell is about 100 m to 10 km. On the other hand, since the indoor base station is installed in the building, the radius of the radio cell is usually 100 m or less, and the radius of the radio cell may be several tens of m or less in the base station for general houses called femtocell base station. ..

In this way, since there is a large difference in the size of the wireless cell between the outdoor base station and the indoor base station, the topology is such that the wireless cell of the indoor base station is included in the wireless cell of the outdoor base station. It is common. Here, when the indoor base station and the outdoor base station use the same frequency carrier, if the transmission power of the indoor base station or the transmission power of the wireless terminal existing in the wireless cell of the indoor base station is set excessively, The interference with the wireless cell of the outdoor base station becomes excessive, and the system capacity deteriorates. On the other hand, if the transmission power is set to be too small, there is a problem that a dead area where the communication service cannot be received indoors occurs, and it is necessary to appropriately set the transmission power of the wireless base station and the wireless terminal under the control.

For example, Patent Document 1 is a conventional technique for setting the transmission power of an indoor base station. In Patent Document 1, an indoor base station measures the received electric field strength (RSCP: Received Signal Code Power) of the common pilot channel (CPICH: Common Pilot Channel) of the surrounding outdoor base stations, and the common pilot channel for the total transmission power is used. A method of setting the downlink transmission power obtained by the following equation 1 in consideration of the ratio and the minimum indoor loss is disclosed (Figure 4, step 108). <Equation 1> Power = (Minimum Indoor Loss) + (Largest Marco Node B RSCP value) -10log10 (Percentage of the Total Femtocell Basestation Power Allocated to CPICH)

Here, (Largest Marco Node B RSCP value) represents the highest level of received electric field strength when signals of a common pilot channel are received from a plurality of outdoor base stations in an indoor base station. Patent Document 1 states that the minimum indoor loss is provided by the central management system, and the details thereof are not specified. Assuming that the building intrusion loss is estimated correctly, if the downlink transmission power is set according to Equation 1 above, the received electric field strengths of the outdoor base station and the indoor base station will be equal near the building boundary, and the radio of the indoor base station will be exactly the same. The cell will be equal to the entire building.

Similarly, in Patent Document 1, a method of collecting measured values of received electric field strength of a radio signal from an outdoor base station from a terminal under a base station and using the measurement results to determine a maximum downlink transmission power and a maximum uplink transmission power. Is disclosed (Figure 6).

Next, Non-Patent Document 1 is known as a conventional technique for obtaining a building intrusion loss. Non-Patent Document 1 is a building intrusion loss derived based on measurement results in various buildings such as office buildings in urban areas, and the building intrusion loss can be obtained by the following empirical formula (Equation 2). <Equation 2> Loss [dB] = 0.6d-0.6Hm + 10

However, in Equation 2 above, d represents the distance [m] from the window in the building to the inside, Hm represents the reception floor height [m], and the first term (0.6d) on the right side is the indoor path loss, and the second term ( 0.6Hm) is the height correction, and item 3 (10) is the loss due to the outer wall of the building. According to Non-Patent Document 1, the standard deviation of the estimation error of the building intrusion loss according to Equation 2 is about 10 dB.

Further, Patent Document 2 discloses a method of estimating the electric field strength on the building surface by three-dimensional radio wave propagation estimation or the like, and estimating the electric field strength inside the building based on the estimation.

<p><patcit num="1"><text>International Public WO2008 / 093100 Pamphlet</text></patcit><patcit num="2"><text>Special Table 2001-506460 Gazette</text></patcit></p>

<p><nplcit num="1"><text>Hideaki Okamoto, Shinichi Ichitsubo, "Examination of 800MHz-8GHz Building Intrusion Characteristics in Cities", 2005 IEICE General Conference, S.23-24, ABS-1-12</text></nplcit></p>

<p> The first problem is that the actual building transmission loss varies depending on the size and location of the building where the indoor base station is installed, so it is uniquely given by the central monitoring system according to Equation 1 in Patent Document 1. This means that there is a possibility that it will deviate significantly from the permeation loss. For example, building transmission loss of radio waves is greatly affected by the material of the outer wall such as wood, the height of the outer wall, the ratio of window glass, the number of inner walls and the floor area of concrete, but these data are generally available. Since it is not included in the digital map information, it is not easy to accurately predict the building transmission loss in advance.</p><p> The second problem is that the number of wireless terminals existing inside the wireless cell of the indoor base station is generally smaller than that of the outdoor base station, so that the terminals are not always distributed over the entire wireless cell. Therefore, even if the measurement information is collected from the wireless terminal as shown in Figure 6 of Patent Document 1, there is a possibility that the transmission power setting for which the building transmission loss is estimated correctly cannot be set.</p><p> In addition, Equation 2 in Non-Patent Document 1 expresses the tendency of building intrusion loss as a whole, but there is a problem that the loss for individual buildings includes errors due to differences in building materials and structures. was there. Therefore, if the transmission power setting of the indoor base station is too large, excessive interference is given to the wireless cell of the outdoor base station, and if the transmission power setting of the indoor base station is too small, the indoor area cannot be sufficiently covered. was there.</p><p> An object of the present invention is to appropriately set the transmission power of a radio signal of an indoor base station in view of the above circumstances so that interference with an outdoor base station can be suppressed to a minimum.</p>

<p> The radio base station, which is one aspect of the present invention, is a radio base station installed indoors, and as shown in FIG. 1, the received electric field strength for measuring the received electric field strength of a radio signal from an outdoor radio base station. Indoor radio based on the measuring means, the building intrusion loss estimating means for estimating the building intrusion loss of the radio signal in the building where the indoor radio base station is installed, and the building intrusion loss estimated by the building intrusion loss estimating means. It has a transmission power setting means for setting the maximum transmission power of the base station.</p><p> The radio base station monitoring system, which is one aspect of the present invention, is a radio base station monitoring system that monitors the communication status of a radio base station, and is a radio signal transmitted by an outdoor radio base station as shown in FIG. , The received electric field strength estimating means for estimating the received electric field strength of the radio signal in the field near the building where the indoor radio base station is installed, and the received electric field strength estimated by the received electric field strength estimating means for the radio signal in the building. It has an estimation result notification means for estimating a building intrusion loss and notifying the indoor radio base station for obtaining the maximum transmission power.</p><p> The transmission power setting method of a radio base station, which is one aspect of the present invention, is a transmission power setting method of a radio base station installed indoors, and is an estimated value of the received electric field strength of a radio signal from an outdoor radio base station. The estimated value acquisition step acquired from the wireless base station monitoring system that monitors the communication status of the wireless base station, and the received electric field strength of the wireless signal from the outdoor wireless base station are measured to obtain the measured value of the received electric field strength. The building intrusion loss estimation step for estimating the building intrusion loss of the radio signal in the building where the indoor radio base station is installed, and the building intrusion loss step, using the measured value acquisition step to be acquired, the estimated value and the measured value of the received electric field strength, and the building intrusion. It has a transmission power setting step for setting the maximum transmission power of an indoor radio base station based on the building intrusion loss estimated in the loss estimation step.</p><p> The program according to one aspect of the present invention is a program used in a radio base station installed indoors, and a computer is provided with an estimated value of the received electric field strength of a radio signal from an outdoor radio base station. Estimated value acquisition processing acquired from the wireless base station monitoring system that monitors the communication status of, and measurement value acquisition that acquires the measured value of the received electric field strength by measuring the received electric field strength of the wireless signal from the outdoor wireless base station. Estimated by the building intrusion loss estimation process and the building intrusion loss estimation process that estimate the building intrusion loss of the radio signal in the building where the indoor radio base station is installed, using the processing and the estimated and measured values of the received electric field strength. Based on the building intrusion loss, the transmission power setting process for setting the maximum transmission power of the indoor wireless base station is executed.</p><p> The recording medium, which is one aspect of the present invention, is a computer-readable recording medium on which the above program is recorded.</p>

<p> According to the present invention, it is possible to appropriately set the transmission power of the indoor base station by correctly estimating the building intrusion loss according to the building in which the indoor base station is installed. As a result, it is possible to secure a coverage area in the building where the indoor base station is installed and prevent excessive interference with the outdoor base station, so that the system capacity of the indoor base station and the outdoor base station can be increased. It will be possible.</p>

<figref num="1">It is a block diagram of the radio base station and the radio base station monitoring system which concerns on this invention.</figref><figref num="2">It is a block diagram of the wireless network in 1st Embodiment of this invention.</figref><figref num="3">It is a block diagram of the radio base station (indoor base station) in 1st Embodiment of this invention.</figref><figref num="4">It is an internal block diagram of the radio base station monitoring system in 1st Embodiment of this invention.</figref><figref num="5">It is a flowchart which shows the operation of the propagation estimation means of the radio base station monitoring system in 1st Embodiment of this invention.</figref><figref num="6">It is a flowchart which shows the operation of the building intrusion loss estimation means of the radio base station (indoor base station) in the 1st Embodiment of this invention.</figref><figref num="7">It is a flowchart which shows the operation of the propagation estimation means of the radio base station monitoring system in 2nd Embodiment of this invention.</figref>

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

[First Embodiment] With reference to FIG. 2, the configuration of the wireless network in the first embodiment as one embodiment of the present invention is shown. The outdoor base station 10 communicates with a terminal located in a wide area indicated by the wireless cell 40 via the wireless link 80. Further, the indoor base station 20 mainly covers the radio cell 50 near the building 70 where the indoor base station is installed. The wireless base station monitoring system 30 is located inside the wired network 90, monitors the communication status of the outdoor base station 10 and the indoor base station 20, and is connected via the wired links 60 and 61, respectively.

The detailed configuration of the indoor base station 20 is shown in FIG. The wireless transmitter / receiver 21 transmits / receives a physical signal at the wireless link 80, and outputs the received signal to the received electric field strength measuring means 22. The received electric field strength measuring means 22 measures the received electric field strength of the pilot channel of a nearby outdoor base station such as the outdoor base station 20, and outputs the result to the building intrusion loss estimating means 23. The building intrusion loss estimating means 23 estimates the amount of signal attenuation when the radio signal of the outdoor base station invades the inside of the building or when the radio signal of the indoor base station penetrates the outside of the building, and determines an appropriate maximum transmission power. Is calculated. The transmission power setting means 24 outputs the maximum transmission power calculated by the building intrusion loss estimation means 23 to the wireless transmitter / receiver 21. The wired transmitter / receiver 25 relays the signal of the wireless terminal and the wired network via the wired link 60, and notifies the wireless base station monitoring system 30 of the monitoring information of the indoor base station.

FIG. 4 shows the internal configuration of the radio base station monitoring system 30 according to the first embodiment of the present invention. The propagation estimation means 36 refers to the map information and the antenna setting information of the radio base station from the map information database 31 and the radio base station database 32, and estimates the received electric field strength in the vicinity of the indoor base station. Even if the propagation estimation method uses a statistical model represented by the Okumura-Hata formula, it predicts the radio wave propagation situation with high accuracy using a deterministic method such as ray tracing. There may be. Propagation estimation result The communication means 33 outputs the received electric field strength in the vicinity of the indoor base station estimated by the radio wave propagation estimation means 36 to the indoor base station 20 via the data transmission / reception means 37. Further, the monitoring information collecting means 34 inputs the activation state and communication state of a general base station from the data transmitting / receiving means 38, and stores the monitoring information database 35 in the monitoring information database 35.

Although the configuration of the embodiment has been described in detail above, other outdoor base stations 10 and wireless terminals are well known to those skilled in the art and are not directly related to the present invention, and therefore the detailed configuration thereof will be omitted. ..

Next, FIG. 5 shows the operation of the radio wave propagation estimation means 36 of the radio base station monitoring system 30.

The wireless base station monitoring system 30 starts the estimation process when it acquires the state change of the base station activation from the indoor base station 20 (step S101). First, the antenna setting information and the pilot signal transmission power of the outdoor base station 10 are acquired from the wireless base station database 32 (step S102). Next, the topographical information and building information near the radio cell 40 are acquired from the map information database 31 (step S103), and the pilot signal reception electric field strength of the outdoor base station 10 outdoors near the building 70 where the indoor base station is installed is estimated (step S103). Step S104). Finally, the pilot signal of the outdoor base station 10 is transmitted to the indoor base station 20 with the estimated value of the received electric field strength outside the building, and the process ends (step S105). In this way, the propagation estimation means 36 can estimate the received electric field strength near the building boundary of the indoor base station 20.

FIG. 6 shows the operation of the building intrusion loss estimation means 23 of the indoor base station 20.

When the indoor base station 20 is activated, the building intrusion loss estimating means 23 acquires an estimated value of the received electric field strength outside the building with respect to the pilot signal of the outdoor base station from the radio base station monitoring system 30 (step S201). Next, the pilot signal received electric field strength measurement value of the actual outdoor base station is acquired from the received electric field strength measuring means 22 (step S202). Here, the building intrusion loss is estimated using the following equation 3 (step S203). In Equation 3, the building intrusion loss is estimated by taking the difference between the estimated value and the measured value. &lt;Equation 3&gt; Building intrusion loss [dB] = Estimated received electric field strength outside the building-Measured received electric field strength

Then, using this building intrusion loss, the maximum transmission power is obtained according to the following equation 4 (step S204). Then, the obtained maximum transmission power is output to the transmission power setting means 24 as the maximum transmission power setting value (step S205). &lt;Equation 4&gt; Maximum transmission power [dBm] = Building intrusion loss [dB] + Pilot signal reception field strength measurement value of outdoor base station [dBm] + Pilot signal transmission power ratio [dB] + Margin [dB]

In the first embodiment of the present invention, as described above, in the indoor base station, the received electric field strength (estimated value) outdoors of the building where the indoor base station is installed obtained by the radio wave propagation estimation means and the actual reception from the outdoor base station. By taking the difference from the signal strength (measured value), it is possible to accurately grasp the building intrusion loss. Then, by setting the maximum transmission power of the indoor base station based on the building intrusion loss, it is possible to minimize the amount of interference between the outdoor base station and the indoor base station and maximize the system capacity.

[Second Embodiment] Next, as the second embodiment of the present invention, the radio wave propagation estimation means 36 of the radio base station monitoring system 30 in the first embodiment predicts the propagation loss inside the building 70 in which the indoor base station 20 is installed. , An example of setting an appropriate margin is shown.

FIG. 7 is a flowchart showing the operation of the propagation estimation means of the radio base station monitoring system according to the second embodiment of the present invention. Steps S301, 302 and 304 are the same as steps S101, 102 and 104 in the first embodiment. The propagation estimation means 36 acquires the height and floor length of the building 70 with the indoor base station in addition to the topographical information and building information near the radio cell 40 from the map information database 31 (step S303). Next, using the height information and floor length information of the building 0 where the indoor base station is installed, the maximum propagation loss in the building is estimated according to the above equation 2. However, the maximum propagation loss in the building is estimated except for the third term (loss due to the outer wall of the building) in Equation 2 (step S305). Next, the estimated value of the electric field strength received outside the building and the maximum propagation loss in the building are transmitted to the indoor base station 20 of the pilot signal of the outdoor base station (step S306).

In the second embodiment of the present invention, the transmission power of the indoor base station can be set more appropriately by adding the maximum propagation loss in the building as a margin in step S204 of FIG.

It should be noted that the above-described embodiment is a preferred embodiment of the present invention, and the scope of the present invention is not limited to the above-described embodiment, and various modifications are made without departing from the gist of the present invention. It is possible to carry out in. For example, as an application example of the present invention, there is a radio base station installed indoors and a monitoring system thereof in a land public mobile communication system.

The program executed by the radio base station in the present embodiment has a modular configuration including the above-mentioned means (received electric field strength measuring means 22, building intrusion loss estimating means 23, transmission power setting means 24, etc.). , Realize concrete means using actual hardware. That is, when a computer (CPU) reads a program from a predetermined recording medium and executes it, each of the above means is loaded on the main storage device and generated.

Further, the program executed by the wireless base station in the present embodiment may be stored on a computer connected to a network such as the Internet, and may be configured to be provided by downloading via the network. Further, the above program may be configured to be provided or distributed via a network such as the Internet.

In addition, the above program is a file in an installable format or an executable format, such as a floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, DVD, non-volatile memory card, etc. It may be configured to be recorded and provided on a computer-readable recording medium. Further, the above program may be configured to be provided by incorporating it into a ROM or the like in advance.

In this case, the program code itself read from the recording medium or loaded and executed through the communication line realizes the function of the above-described embodiment. The recording medium on which the program code is recorded constitutes the present invention.

1 Radio base station 6 Received electric field strength estimation means 7 Estimated result notification means 10 outdoor base station 20 indoor base station 21 Wireless transmitter / receiver 2,22 Received electric field strength measuring means 3,23 Building intrusion loss estimation method 4,24 Transmission power setting means 25 Wired transmitter / receiver 5,30 wireless base station monitoring system 31 Map information database 32 Radio base station database 33 Propagation estimation result Communication means 34 Monitoring information collection means 35 Monitoring information database 36 Radio wave propagation estimation means 37 Data transmission / reception means 40,50 wireless cell 60,61 Wired link 70 Building with indoor base station 80 wireless link 90 Wired network