JP2001168812A - Communication characteristic control method for indoor radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication characteristic control method for indoor radio communication system that can reduce electromagnetic interference caused by a radio wave from a radio base station of other system and an indoor environment, in the case of utilizing the indoor radio communication system such as radio LAN. SOLUTION: This communication characteristic control method is used for the indoor radio communication system, to control a communication characteristic of a radio communication system consisting of a radio base station and one or more terminal stations that are installed in one indoor place. The communication characteristic control method is characterized, in that a radio wave propagation characteristic between the radio base station placed at a specific position and the terminal station or a radio wave propagation characteristic between a radio station belonging to other radio communication system, and the terminal station is obtained through a simulation or a measurement, one or more communication characteristic control positions, requiring absorption of the radio wave in the indoor place are decided on the basis of the obtained radio wave propagation characteristic and a barrier having a radio wave absorbing function, are placed at the communication characteristic control positions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling communication characteristics of an indoor wireless communication system, and is used for improving communication characteristics indoors and separating communication areas of a plurality of wireless communication systems installed in the same indoor space.

[0002]

2. Description of the Related Art Currently, a wireless LAN (Local Area Network) is used.
In an indoor wireless communication system such as k), it is required to accommodate as many users as possible with limited frequency resources. Therefore, in a communication area for one wireless base station, multiple access (Multiple Access) for efficient simultaneous communication by a large number of users, and a zone in which the same frequency as the radio wave of another wireless base station is repeatedly used apart from each other. Communication control techniques such as configuration and transmission power control for minimizing the transmission power of each terminal to a necessary minimum are widely used.

[0003] By using these communication control techniques, it is possible to minimize the interference that all wireless terminals receive from other wireless terminals, and all wireless terminals can communicate fairly. These communication control techniques are used for the purpose of improving the frequency use efficiency as a result. The multiple access method is roughly divided into time division multiplexing (TD
MA), frequency division multiplexing (FDMA), code division multiplexing (CDMA), etc., and channel sharing, such as ALOHA (ALOHA) and carrier detection multiple access (CSMA).

[0004] In the channel occupation method, each user can occupy a channel divided by time, frequency, or the like without receiving interference from other users. In the channel sharing scheme, each user shares the same channel, and communicates efficiently while allowing some interference from other users. In the zone configuration technology, an omnidirectional antenna is used in a horizontal plane. In addition, the plane is divided into zones having a predetermined shape, and a radio signal is emitted for each zone. Further, a different radio frequency is allocated to each adjacent zone, and the same radio frequency is allocated to each zone in a fixed repetition pattern.
This prevents interference of wireless signals between a plurality of zones. In this zone configuration technology, F is used between adjacent zones.
Avoid interference by DMA, TDM in zone
A or CDMA can avoid interference between wireless communication systems.

[0005] In the transmission power control technique, the transmission power of each terminal is minimized to prevent a radio communication signal from a specific transmission / reception device having a relatively high strength from affecting other transmission / reception devices. In wireless communication, when a plurality of wireless terminals make a simultaneous connection to a base station, control is performed so that all wireless terminals can communicate fairly, thereby improving frequency use efficiency.

[0006] For example, in a system such as a 2.4 GHz band wireless LAN, spread spectrum modulation is used.
When communication control by the MA system is difficult, the CSMA system is adopted so that all wireless terminals can perform fair communication.

[0007]

By the way, in an office where a plurality of independent networks exist on one floor, it is assumed that each network is constituted by a wireless LAN, and a wireless signal output from each wireless LAN is assumed. (Radio waves) reach the area of another wireless LAN with a sufficiently large electric field strength, so that each wireless LAN adversely affects each other.

For example, when a plurality of independent networks are configured on the same floor by using a plurality of sets of the same type of wireless LAN system, the carrier frequency of the plurality of networks is the same, so that the CSMA wireless communication system is used. LAN
Is adopted, the control station performs CSMA control even on a radio signal that is completely unrelated to the network to which the white body belongs, in order to avoid signal collision.

In other words, even if the channel is not used by the network to be controlled, the use of the channel for transmitting the communication signal by another network is restricted. A plurality of networks will share the wireless communication transmission path.
Therefore, when a plurality of wireless communication systems that perform transmission and reception using the same system are used in the same area, the number of wireless terminals that perform transmission and reception increases regardless of whether the networks to which they belong are the same. Then, there is a problem that the transmission rate decreases almost in inverse proportion to the number of sets of the wireless communication system that performs transmission and reception.

Further, even when a plurality of independent networks on the same floor use different wireless LAN systems, when a wireless LAN communication signal reaches an area where another network exists, a plurality of wireless networks are provided. LA
Some or all of the occupied frequencies of N overlap, causing electromagnetic interference, which may result in the loss of wireless communication signals.

Furthermore, indoor wireless systems such as wireless LANs have a higher communication speed than cellular phones and PHSs, and therefore tend to be susceptible to the effects of indoor communication environments. For example, the bit error rate (BER) increases due to the effect of a delayed wave generated by a strong reflected wave from a metal wall or the like, and the communication speed decreases. For this reason, it has been studied to adopt an antenna having directivity for each of the base station and the terminal so as not to be affected by the delay wave. However, directional antennas are expensive, so wireless LAN
Indoor wireless systems such as these are hardly available on the market, and there are many products equipped with inexpensive omnidirectional antennas on the market.

[0012] Further, a method has been studied in which the strength of the reflected wave is reduced by attaching a radio wave absorber to a wall where a strong reflected wave is generated, thereby reducing the influence of the delayed wave. However, in an actual office or the like, a bookcase or the like is mostly installed on a wall, and it is often difficult to actually install a radio wave absorber on a wall. The present invention has been made in view of the above circumstances, and when using an indoor wireless communication system such as a wireless LAN, it is possible to reduce electromagnetic interference caused by the influence of radio waves and indoor environment of wireless base stations belonging to other systems. It is an object of the present invention to provide a communication characteristic control method for an indoor wireless communication system.

[0013]

An indoor radio communication system for controlling the communication characteristics of a radio communication system which is located in the same room and is constituted by a radio base station and one or more terminal stations. Communication characteristic control method, wherein the radio wave propagation characteristics between the radio base station and the terminal station located at a specific position, or radio waves between the radio station belonging to another radio communication system and the terminal station Propagation characteristics are obtained by simulation or measurement, and based on the obtained radio wave propagation characteristics, one or more communication characteristic control positions where the indoor radio waves need to be absorbed are determined, and the communication characteristic control positions have a radio wave absorption function. A partition is arranged.

According to the first aspect of the present invention, an indoor radio wave propagation characteristic is controlled by arranging a screen having a radio wave absorbing function indoors. Since the screen has a radio wave absorbing function, the position for controlling the communication characteristics changes according to the position where the screen is installed. Since the position where the partition is installed can be changed to various positions indoors as well as near the wall, radio wave propagation characteristics suitable for the wireless communication system to be installed can be realized.

For example, when a plurality of independent wireless communication systems are installed in the same room, if a partition is arranged at a predetermined position, radio waves radiated by other systems will be shielded and radio waves will reach. Areas can be separated for each system. In addition, if the wall has a characteristic of easily reflecting radio waves, such as metal, if the delay dispersion increases due to the effect of the delay wave generated by the reflection from the wall, the bit error of the data transmitted by the wireless communication may increase. Rate (BE
R) increases. If a partition is arranged on the front of a wall or the like, reflected waves from the wall can be reduced.

According to the first aspect, the radio wave propagation characteristics in the room before the partition is installed are determined, and the position where the partition is installed is determined based on the result. Position). For example, if a screen is arranged in a portion having a large delay dispersion value in a room, the generation of a reflected wave is suppressed by the radio wave absorption function of the screen, and the delay dispersion is reduced, so that the occurrence of a bit error in wireless data transmission is suppressed.

Further, for example, if a partition is disposed at a position where the electric field strength of the radio wave emitted from another system is large, the electric field strength of the radio wave from the other system is reduced and interference is less likely to occur. Useful for area separation. According to a second aspect of the present invention, in the communication characteristic control method for an indoor wireless communication system according to the first aspect, a radio wave propagation characteristic is obtained again for environmental conditions in a state where the partition is arranged at the communication characteristic control position, Is compared with a predetermined allowable condition, and if the radio wave propagation characteristic does not satisfy the allowable condition, at least one of the position, height, width, and radio wave absorption characteristic of the partition is changed to change the environment. The radio wave propagation characteristic under the condition is obtained again, and an environmental condition satisfying the allowable condition is specified.

Even if a partition is arranged at a communication characteristic control position determined from the radio wave propagation characteristics obtained in a state where no partition is arranged, required communication characteristics are not always obtained. Therefore, in the second aspect, the radio wave propagation characteristics are obtained even under the condition where the partition is arranged, and the result is compared with a predetermined allowable condition.

If the radio wave propagation characteristics do not satisfy the permissible conditions, at least one of the position, height, width and radio wave absorption characteristics of the partition is changed, and the radio wave propagation characteristics under the changed environmental conditions are obtained again. . By repeating such an operation, it is possible to specify an environmental condition satisfying the allowable condition. According to a third aspect of the present invention, in the communication characteristic control method for an indoor wireless communication system according to the first aspect, when a plurality of independent wireless communication systems are arranged in the same indoor space, at least based on the obtained radio wave propagation characteristics, One communication characteristic control position is determined in a space between a plurality of wireless base stations belonging to different wireless communication systems.

According to the third aspect of the present invention, the partitions are arranged in a space between a plurality of wireless base stations belonging to different wireless communication systems, so that the partitions receive radio waves from each wireless base station to reach the area of another system. Therefore, the areas can be separated so that the radio waves of a plurality of wireless communication systems do not interfere with each other. According to a fourth aspect of the present invention, in the communication characteristic control method for an indoor wireless communication system according to the first aspect, at least one communication characteristic control position is opposed to a metal wall surface based on the obtained radio wave propagation characteristic. The partition is set at a position at a predetermined distance or more from and the partition is arranged substantially parallel to the wall surface.

According to the fourth aspect, since the partition is arranged in front of the metal wall surface, reflected waves generated by the wall can be suppressed, and delay dispersion can be reduced. Further, since the partition is arranged in parallel with the wall surface with a predetermined interval or more between the wall surface and the partition, a passage can be formed between the wall surface and the partition.
For this reason, the partition can be arranged at an appropriate position and the communication characteristics can be improved with almost no change in the layout of a bookcase or desk in a room in a general office or the like.

According to a fifth aspect of the present invention, there is provided the communication characteristic control method for an indoor wireless communication system according to the first aspect, wherein the radio wave propagation characteristics include a reception electric field strength, a delay dispersion value, a bit error rate, and a bit error rate at the position of the terminal station. It is characterized in that at least one of the propagation loss with the terminal station is obtained. According to a sixth aspect of the present invention, in the communication characteristic control method for an indoor wireless communication system according to the second aspect, a plurality of candidate points are determined at regular intervals in an area where the terminal station can be arranged indoors, and each of the candidate points is determined. Assuming that the terminal station is arranged, radio wave propagation characteristics are obtained for each position of the candidate point, and the position of the partition, until the radio wave propagation characteristics at all positions of the candidate point satisfy the allowable condition, height,
It is characterized in that at least one of the width and the radio wave absorption characteristics is changed.

When a wireless LAN or the like is adopted as a wireless communication system, the number of terminal stations included in the system is often large, and there is a possibility that the terminal stations are installed at various positions in a room. Therefore, it is not sufficient that the radio wave propagation characteristics satisfy the permissible condition at one place in the room. According to the sixth aspect, the radio wave propagation characteristics can be obtained for each position of various candidate points, and the partitions can be arranged so that the radio wave propagation characteristics of each position of the candidate points satisfy the allowable condition.

According to a seventh aspect of the present invention, in the communication characteristic control method for an indoor wireless communication system according to the first aspect, a simulation of a radio wave propagation characteristic between the wireless base station and the terminal station is performed by using ray tracing. And According to the seventh aspect, since ray tracing is used, the radio wave propagation characteristics including the influence of the reflected wave can be obtained by simulation without actually installing a wireless base station and a terminal station in a room or installing a measuring instrument.

A communication characteristic control method for an indoor wireless communication system according to claim 8 for controlling communication characteristics of a wireless communication system which is arranged in the same indoor room and is configured by a wireless base station and one or more terminal stations. A communication characteristic control method for an indoor wireless communication system, wherein an environmental condition is to arrange a partition having a radio wave absorbing function at a specific position separated from an indoor metal wall by a predetermined distance. The radio wave propagation characteristics between the radio base station and the terminal station are obtained by simulation or measurement, and the effect of improving the communication characteristics by the partition is confirmed from the obtained radio wave propagation characteristics.

According to the present invention, the indoor radio wave propagation characteristic is controlled by disposing a screen having a radio wave absorbing function at a specific position separated by a predetermined distance from an indoor metal wall surface. Since the partition can be freely changed in position, it can be placed away from the wall. By disposing the partition on the front surface of the metal wall, it is possible to suppress the reflected wave from the wall and improve the radio wave propagation characteristics between the wireless base station and the terminal station.

Further, the radio wave propagation characteristics between the radio base station and the terminal station are obtained by simulation or measurement, and the effect of improving the communication characteristics by the screen is confirmed from the obtained radio wave propagation characteristics. Can be identified as appropriate. According to a ninth aspect, in the communication characteristic control method for an indoor wireless communication system according to the eighth aspect, the radio wave propagation characteristic between the wireless base station and the terminal station is determined for each of a plurality of types of environmental conditions having different partition heights. It is characterized in that a preferable environmental condition is specified by comparing the radio wave propagation characteristics of a plurality of types of environmental conditions.

The radio wave propagation characteristics are changed by changing the height of the partition to be used. According to the ninth aspect, the radio wave propagation characteristics are obtained in the case of using the screens of the respective heights, so that a preferable environmental condition can be specified by comparing the radio wave propagation characteristics of a plurality of types of environmental conditions. Claim 10
The communication characteristic control method for an indoor wireless communication system according to claim 8, wherein a simulation of a radio wave propagation characteristic between the wireless base station and the terminal station is performed by using ray tracing.

According to the tenth aspect, since ray tracing is used, the radio wave propagation characteristics including the influence of the reflected wave can be obtained by simulation without actually installing a radio base station and a terminal station or installing a measuring instrument indoors. Can be.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) One embodiment of a communication characteristic control method for an indoor wireless communication system according to the present invention will be described with reference to FIGS. This form corresponds to claims 1, claim 2, claims 4 to 7.

FIG. 1 is a flowchart showing a communication characteristic control procedure of this embodiment for implementing the communication characteristic control method for an indoor wireless communication system according to the present invention. Figure 3 shows indoor 1
It is a top view showing the example of composition of a floor. In this embodiment, it is assumed that a set of wireless LAN systems is installed as a wireless communication system on a general indoor floor as shown in FIG. In order to improve the communication characteristics during the period, the procedure shown in FIG. 1 is performed, and the communication characteristics are controlled by installing a partition having a radio wave absorbing function.

In this embodiment, a simulation relating to the radio wave propagation state is performed using a computer (not shown). In steps S10, S11, S12, S13 and S15 of FIG. 1, various information necessary for this control is input to the computer. In step S10, the arrangement (position, position, etc.) of each wall or building material (column) existing in the room to be controlled
Enter information about size and material.

In step S11, position information of an area where a partition cannot be arranged is input. For example, a new partition cannot be placed inside a space in which fixtures such as immovable desks are placed in advance, so input that location information to exclude that area from the placement target area of the partition. deep. In step S12, a minimum distance Dmin (for example, 1 m) from the wall surface is input. Since it is necessary to secure a passage for humans near the wall surface, it is necessary to prevent the passage from being blocked by a partition. Therefore, a minimum distance Dmin is input in order to exclude a position close to the wall surface from the partition placement target area.

In step S13, the installation position (including the position of the antenna and the height from the floor) of the wireless base station of the wireless LAN system to be controlled is input. Step S
In 14, all the areas where indoor terminals can be installed are divided into a large number at regular intervals, and each divided area is determined as a reception position. That is, it is assumed that a terminal is installed at each reception position.

In step S15, the width and height of the partition used for controlling the communication characteristics and the radio wave absorption characteristics are input. In step S16, the radio wave propagation state from the position of the radio base station to the reception position is analyzed using the ray tracing technique for each reception position before the partition is arranged in the room, and the distribution of delay dispersion in the room is analyzed. Ask for. Delay dispersion is a value indicating the remaining amount of radio waves reflected at various positions and is closely related to the bit error rate (BER) of a wireless communication system. It is considered that the smaller the delay dispersion, the better the communication quality. good.

Here, as a ray tracing technique for obtaining the radio wave propagation state, reference 1 (KR Schau
bach, NJ Davis, and TS Rappaport, “A Ray Trac
ingMethod for Predicting Path Loss and Delay Sprea
d in Microcellular Environments, ”IEEE Vehicular T
echnol. Conf., pp. 932-935, May 1992).

Before executing step S16, information on the radio frequency, antenna type and directivity used by the wireless LAN system to be analyzed is input to the computer. In step S17, step S
Based on the indoor delay dispersion distribution state obtained in step 16,
The communication characteristic control position where the partition should be placed is determined. However,
The non-arrangeable position input in step S11 is excluded in advance. Further, the distance from the wall surface to the communication characteristic control position is at least larger than the minimum distance Dmin in step S12. When the screen is arranged near the wall, the direction of the screen is limited so that the screen is arranged substantially in parallel with the wall surface facing the wall in order to secure a space for the passage.

In step S18, it is assumed that a partition having radio wave absorption characteristics is installed at the communication characteristic control position determined in step S17. Actually, a non-metallic partition (which does not affect the radio wave propagation) having a radio wave absorbing plate attached to the surface facing the inside of the room can be used as a partition having radio wave absorbing characteristics. In step S18, the radio wave propagation state is analyzed by ray tracing in the same manner as in step S16 with the screen having the radio wave absorption characteristic installed at the communication characteristic control position, and the delay dispersion and the distribution of the received electric field strength at each position in the room are analyzed. Ask for.

In step S19, the delay dispersion and the received field strength are compared with predetermined allowable conditions for all of the various reception positions determined in step S14. If the delay dispersion and the received electric field strength of all the receiving positions are within the allowable range, the process proceeds to step S21, and if there is a receiving position outside the allowable range, the process proceeds to step S20. The criterion value (permissible condition) of the electric field strength and the delay dispersion differs depending on the wireless system. For example, 2.4 GHz band wireless LA
N, the electric field strength is -75 dBm or more, and the delay dispersion is 15
ns or less (however, BER is large but communication is possible even if it is about 40 ns or less), the communication area is available.
The communication area is 250 ns or less in delay dispersion.

In step S20, at least one of a partition arrangement position (communication characteristic control position), a partition height, a partition width, and a radio wave absorption characteristic of the partition is changed within a predetermined changeable range. . Then, the process returns to step S18, and the process is repeated until the communication characteristics satisfy the allowable condition. In practice, first try to change the position of the partition by moving it, and if the acceptable condition is still not met, change the height of the partition; Or the conditions may be sequentially changed so as to change the radio wave absorption characteristics.

For example, when the height is 0.9 m, 1.2 m, 1.
If a screen to be actually used can be selected from commercially available screens of 5 m and 1.8 m, a simulation is initially performed on the assumption that a screen having a height of 0.9 m will be used. If not, the height of the screen is set to 1.2 m, 1.5 m, 1..
What is necessary is just to change it to 8m.

In step S21, a partition having radio wave absorption characteristics is actually installed at the communication characteristic control position under the same conditions as when the simulation was last performed. Although not shown, in actuality, looking at the distribution of the delay dispersion obtained in step S16, the delay dispersion is small in the vicinity of the radio base station and in the vicinity of the glass window where radio wave reflection is unlikely to occur. In the vicinity of the wall, there is a tendency that the delay dispersion increases.

Therefore, in step S17, the partition is arranged so as to face the front surface of the wall at a distance of Dmin or more from the metal wall (to determine the communication characteristic control position). If a screen having radio wave absorption characteristics is arranged at that position, radio waves reaching the wall are attenuated and the influence of reflected waves is reduced, so that delay dispersion is reduced. In the example of FIG.
Surface walls 1101, 1102, and 1103 are all made of a material (metal or the like) that easily reflects radio waves, and the other surface is made of a glass wall (window or the like) 1104. Also,
The ceiling is a rock wool sound absorbing board and the floor is concrete. The size of the floor shown in FIG. 3 is 15 m in length, 30 m in width, and 2.8 m in height. The base station antenna 1107 is installed substantially at the center of the room.

FIG. 3 shows the result of executing the procedure of FIG. 1 under such conditions and actually setting the partitions. FIG.
In the example, a non-metallic partition 1105 to which a radio wave absorbing plate 1106 is attached is installed on the front surface of each of three walls 1101, 1102, 1103.

(Second Embodiment) Another embodiment of a communication characteristic control method for an indoor wireless communication system according to the present invention will be described with reference to FIGS. This embodiment corresponds to claims 1 to 3, and claims 5 to 7. FIG. 2 is a flowchart showing a communication characteristic control procedure of this embodiment for implementing the communication characteristic control method of the indoor wireless communication system of the present invention. FIG. 4 is a plan view showing a configuration example of one indoor floor.

In this embodiment, for example, it is assumed that two independent wireless LAN systems are installed as a wireless communication system on one floor of a general indoor as shown in FIG. The procedure shown in FIG. 2 is implemented to prevent the two sets of wireless LAN systems from interfering with each other, and the communication characteristics are controlled by installing a partition having a radio wave absorbing function.
Also, a simulation by ray tracing is performed as in the first embodiment.

Steps S10 to S15 in FIG. 2 are the same as those in the first embodiment, but in step S13B, the position information of each base station of the two sets of wireless LAN systems is input. In the example of FIG. 4, base stations (antennas) 606 and 607 of two independent systems are arranged at substantially the centers of the communicable areas 608 and 609. In step S16B, in a state before the partition is arranged in the room,
The radio wave propagation state from the position of the radio base station to the reception position is
Analysis using ray tracing technology for each receiving position,
The distribution of indoor propagation loss (or received electric field strength) is obtained.

In step S17B, step S16B
The communication characteristic control position where the partition is to be arranged is determined based on the indoor propagation loss distribution state obtained in step (1). here,
In order to prevent radio waves from each base station from reaching and interfering with the communicable area of a system different from the system to which the base station belongs, a screen having a radio wave absorbing function is installed for the purpose of shielding radio waves.

Accordingly, the position where the partition is arranged in step S17B is a position in the space between the two base stations, that is, a position where the communicable areas 608 and 609 of a plurality of wireless LAN systems overlap. However, the non-arrangeable position input in step S11 is excluded in advance. In the example of FIG. 4, two sets of radio-absorbing partitions 10 (1) and 10 (2) constituted by a non-metallic partition 604 to which a radio-absorbing plate 605 is attached, It is located almost in the center. The radio wave absorbing plate 605 is arranged on the inner surface of each of the communicable areas 608 and 609.

In step S18B, step S17B
It is assumed that a partition having radio wave absorption characteristics is installed at the communication characteristic control position determined in (1). Actually, a non-metallic partition (which does not affect the radio wave propagation) having a radio wave absorbing plate attached to the surface facing the inside of the room can be used as a partition having radio wave absorbing characteristics. Step S18
In B, in the state where the screen having the radio wave absorption characteristic is installed at the communication characteristic control position, the radio wave propagation state is analyzed by ray tracing as in step S16B, and the distribution of the propagation loss at each position in the room is obtained.

In step S19B, step S18B
Based on the distribution of the propagation loss obtained in the above, it is checked whether or not the radio wave interference between the systems is within an allowable range. For example, Reference 2
(Takaya et al., “Inter-model interference characteristics of 2.4 GHz band wireless LAN”, IEICE B-II, Vol. J80-B-II, N
o. 3, pp. According to 368-371, 19977.4), if the intensity difference between base station radio waves of a plurality of wireless LANs is 15 dB or more, no electromagnetic interference occurs.

Therefore, for example, the threshold value may be set to 15 dB. Then, at each reception position in the communicable areas 608 and 609, the difference between the electric field strength of the radio wave from the base station of the system forming the area and the electric field strength of the radio wave from the base station belonging to another system is determined. Compare with threshold. If the difference between the electric field intensities at all the receiving positions is equal to or larger than the threshold value, no interference occurs, so that it can be regarded as being within the allowable range in step S19B.

When the conditions such as the output of a plurality of systems are the same, the propagation loss can be directly replaced with the received electric field strength, and the difference in the received electric field strengths of the plural systems can be compared. If any of the receiving positions is out of the permissible range, the process proceeds to step S20, and FIG.
As in the case of the above, the position at which the partition is arranged, the height of the partition, the width of the partition, or the radio wave absorption characteristics of the partition are changed.

In step S21, a partition having radio wave absorption characteristics is actually installed at the communication characteristic control position under the same conditions as when the simulation was last performed. An example of the actual arrangement of the radio wave absorbing partition 10 will be described with reference to FIG. The floor shown in FIG. 4 has a length of 15 m, a width of 45 m, and a height of 2.8 m, and the surrounding walls are composed of a gypsum board wall 601, a metal wall 602, and a glass wall 603.

In FIG. 4, two radio wave absorbing partitions 10 are provided.
(1) and 10 (2) prevent the radio waves transmitted by the base station 607 from affecting the communication of the system constituting the communicable area 608, and the radio waves transmitted by the base station 606 define the communicable area 609. It is arranged as a result of performing the processing shown in FIG. 2 in order to prevent the communication of the constituent systems from being affected.

In the example of FIG. 4, two radio wave absorbing partitions 10
The interval (width of the passage 20) between (1) and 10 (2) is 1 m, and the height of the radio wave absorbing partition 10 is 1.8 m. The two radio wave absorbing partitions 10 (3) and 10 (4) shown in FIG. 4 are arranged as a result of performing the processing shown in FIG.
It is provided in order to reduce the reflected wave from 02.

In FIG. 4, the left half of the room is the base station 6
06 is allocated as a communicable area 608 of the system including the base station 607, and the right half is allocated as a communicable area 609 of the system to which the base station 607 belongs.

The antenna of base station 606 is installed at a height of about 1.5 m from the floor substantially at the center of communicable area 608. The antenna of the base station 607 is installed at a height of about 1.5 m from the substantially central floor of the communicable area 609. Under the conditions of FIG. 4, the propagation loss at each position was actually measured in the case where the radio wave absorption screen 10 was provided and in the case where it was not provided. The result is shown in FIG. In this measurement, the receiving antenna is movably arranged on a line parallel to the line connecting the antennas of the two base stations 606 and 607 and on a line passing directly below the base stations 606 and 607 at a height of 1 m. Then, while moving the receiving antenna in the long side direction of the floor, the propagation loss from the antenna of the base stations 606 and 607 to the receiving antenna was measured.

In this measurement, an omnidirectional monopole antenna in a horizontal plane was used as an antenna of the base stations 606 and 607 and a receiving antenna. The frequency is 2.4 GH
The center frequency of the z-band wireless LAN was set to 2.484 GHz, and the measurement was performed using a network analyzer. FIG.
Referring to, within the communication area of each base station,
It can be seen that the propagation loss hardly changes with and without the partition, but a difference of 10 dB or more between the case with and without the partition occurs outside the communication area.

In FIG. 5, when there is no partition, the difference in the intensity of radio waves from the two base stations 606 and 607 near the center of the room is 15 dB or less. It can be seen that there is a difference in intensity. According to Document 2, electromagnetic interference does not occur when the intensity difference between base station radio waves of a plurality of wireless LANs is 15 dB or more. Therefore, by installing a partition, interference between base station radio waves can be prevented. Areas can be clearly separated.

In this embodiment, the radio wave propagation characteristics are obtained by simulation. However, it is also possible to determine the position of the partition from the result of actually measuring the characteristics using a measuring instrument or the like.

(Third Embodiment) Another embodiment of a communication characteristic control method for an indoor wireless communication system according to the present invention will be described with reference to FIGS. This embodiment corresponds to claims 8, 9, and 10. FIG. 6 is a plan view showing a configuration example of one indoor floor. FIG. 7 is a graph showing an example of the place ratio for each BER in the room. FIG.
6 is a graph showing an example of a location ratio for each delay dispersion indoors. FIG. 9 is a graph showing an example of the relationship between the return loss and the delay dispersion indoors.

In this embodiment, a partition 10 having radio wave absorption characteristics is installed at a position in front of a metal wall after a passage is secured by the wall of the floor. Then, it was confirmed from the radio wave propagation characteristics obtained by ray tracing or actual measurement that the communication characteristics of the wireless communication system were improved by installing the partition 10. Three examples of the results will be described below.

(Example (1)) The floor shown in FIG.
5m, width 9.1m, height 2.8m, wall is metal plate,
The ceiling is made of rock wool sound absorbing boards, and the floor is made of metal access floor. Further, on one surface of the wall, a radio wave absorber 801 is installed to simulate a building material with low reflection such as a window.

In this example, the radio wave absorption screens 10 (1), 10 (2), 10 (3) are located at a position 1 m away from the respective metal walls.
Is installed. Each radio wave absorbing partition 10 has a height of 1.8.
An electromagnetic wave absorbing plate 803 is attached to the entire non-metallic partition 802 inside the room. The non-metallic partition 802 is made of wood. The radio wave absorbing plate 803 has a thickness of 8 m.
m and an aluminum sheet having a thickness of 1 mm is lined. Each of the radio wave absorbing screens 10 is provided to weaken a reflected wave from a metal wall.

The base station antenna 804 is installed at a height of 1 m at the center of the room. In addition, a receiving antenna 80 arranged at a height of 1 m to confirm communication characteristics.
5 was moved at intervals of 20 cm vertically and horizontally. The communicable area 806 of the communication system is formed in a space inside the radio wave absorbing partition 10. Further, a passage 807 having a width of 1 m is provided between the radio wave absorbing screen 10 and the metal wall. As the base station antenna 804 and the receiving antenna 805, an omnidirectional monopole antenna in a horizontal plane was used.

FIG. 7 shows the measurement result of the BER in the floor environment of FIG. In this measurement, the actual BER is measured at each measurement point using a network analyzer,
The location ratio for the number of all measurement points was calculated for each BER. However, although the BER is actually 10 ⁻⁸ or less at many measurement points, FIG. 7 shows only the value of 10 ⁻⁸ or more.

Referring to FIG. 7, the location ratio of the BER between 10 ^{-2 and} 10 ^-1 is relatively large when there is no partition, but when the partition is installed, the BER having a large location ratio is 10 ^-5 or less. Has changed. In this way, BE
It was confirmed that R was improved. FIG. 8 shows a measurement result of the delay dispersion in the floor environment of FIG. In this measurement, the actual delay dispersion was measured at each measurement point using a network analyzer, and the location ratio with respect to the number of all the measurement points was calculated for each delay dispersion value. FIG. 8 also shows the results obtained by analyzing by ray tracing.

Referring to FIG. 8, it can be seen that the delay dispersion is greatly improved by installing the partition. The peak value of the location ratio is improved by about 18 ns. The measured values and the values calculated by ray tracing show almost the same tendency. From the results of FIGS. 7 and 8, it was confirmed that the communication characteristics of the wireless communication system could be improved by installing the radio wave absorbing partition 10 as shown in FIG.

(Example (2)) On the floor shown in FIG. 3, for each of three types of environments in which the material combination of the walls 1101 to 1103 is different, the radio wave propagation characteristics after the partitions are arranged by ray tracing. And analyzed. In this example, delay dispersion was obtained as a radio wave propagation characteristic.

The size of the floor shown in FIG.
m and 2.8 m in height. The walls 1101 to 1103 are made of metal or gypsum board. The wall 1104 is made of glass. The ceiling is a rock wool sound absorbing board and the floor is concrete. In environment 1, the walls 1101-1103
Are all metal walls, the walls 1101 to 11
On the front of each of No. 03, a screen was arranged after securing a space of a passage of 1 m. Each of the screens is a non-metallic screen 110 having a height of 1.8 m to which a radio wave absorbing plate 1106 is attached.
5.

In the environment 2, it is assumed that the walls 1101 and 1102 are metal walls and the wall 1103 is a gypsum board, and a screen space of 1 m is secured in front of each of the walls 1101 and 1102. Was placed. Wall 110
No screen is placed in front of 3. Each partition is constituted by a non-metallic partition 1105 having a height of 1.8 m to which a radio wave absorbing plate 1106 is attached.

In the environment 3, the wall 1102 is a metal wall,
Assuming the case where the walls 1101 and 1103 are gypsum boards, the partitions were arranged only on the front surface of the wall 1102 after securing a space for the passage of 1 m. No partitions are arranged in front of the walls 1101 and 1103. Each partition is a non-metallic partition 11 having a height of 1.8 m, to which a radio wave absorbing plate 1106 is attached.
05.

In this example, the position where the base station antenna 1107 is installed is set at a position at a height of 1.5 m at the center of the room. The height of the receiving point of the receiving antenna provided for the analysis was set to 1 m, and 406 receiving points (observation points) were arranged at various intervals indoors at intervals of 1 m.

Here, the delay dispersion was analyzed by ray tracing for the frequency of 2.484 GHz which is the center frequency of the wireless LAN. The analysis was performed in consideration of reflections up to 15 times. The relative complex refractive index of building materials is described in the literature (Maeda et al., EMC'99 / TOKYO, 20A5).
04, pp. 672-677, 1999, 5).

FIG. 9 shows the analysis result of the delay dispersion. Here, the result of averaging the values at all reception points is shown. However, the return loss of the radio wave absorbing plate 1106 is 0 to 4
It was changed in the range of 0 dB. Also, it is assumed that a monopole antenna having a horizontal omnidirectional antenna is used as the base station antenna and the receiving antenna. Referring to FIG. 9, in any environment, the delay dispersion is reduced with an increase in the return loss, and by installing a screen having radio wave absorption characteristics only on the front surface of the metal wall, the improvement can be improved by 20 ns or more. It turns out that there is an effect.

When the return loss exceeds 12 dB, the delay dispersion hardly changes.
It is understood that about 10 dB is sufficient for the return loss of No. 6. As described above, it was confirmed from FIG. 9 that the communication characteristics of the wireless communication system were improved as a result of installing a screen having radio wave absorption performance in front of the metal wall after securing a passage in front of the metal wall. .

Further, the change in the location ratio of the delay dispersion with respect to the change in the height of the partition was examined. As a result, it was found that as the height of the partition increases, that is, as the area of the radio wave absorber increases, the delay dispersion decreases. That is, the higher the partition, the higher the effect of improving the communication characteristics.

[0079]

As described above, according to the communication characteristic control method of the indoor wireless communication system of the present invention, a plurality of screens used in actual offices and the like are provided with a radio wave absorbing performance, so that a plurality of screens can be provided. The communication area of the indoor wireless communication system can be separated or the communication characteristics can be improved, and a communication failure due to electromagnetic interference can be easily solved without changing the wireless system itself or the antenna system.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating a communication characteristic control procedure according to a first embodiment.

FIG. 2 is a flowchart illustrating a communication characteristic control procedure according to a second embodiment.

FIG. 3 is a plan view showing a configuration example of one indoor floor.

FIG. 4 is a plan view showing a configuration example of one indoor floor.

FIG. 5 is a graph showing a distribution example of a propagation loss.

FIG. 6 is a plan view showing a configuration example of one indoor floor.

FIG. 7 is a graph showing an example of a location ratio for each BER indoors.

FIG. 8 is a graph showing an example of a location ratio for each delay dispersion indoors.

FIG. 9 is a graph showing an example of the relationship between indoor return loss and delay dispersion.

[Explanation of symbols]

 Reference Signs List 10 radio wave absorbing screen 20 passage 601 gypsum board wall 602 metal wall 603 glass wall 604 non-metal screen 605 radio wave absorbing plate 606, 607 base station 608, 609 communicable area 801 radio wave absorber 802 non-metal screen 803 radio wave absorbing plate 804 Base station antenna 805 Receiving antenna 806 Communication area 807 Passage 1101, 1102, 1103 Wall 1104 Glass wall 1105 Non-metallic partition 1106 Radio wave absorption plate 1107 Base station antenna

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuhiro Takaya 2-3-1 Otemachi, Chiyoda-ku, Tokyo Inside Nippon Telegraph and Telephone Corporation (72) Kanya Shiokawa 3-fourth Shibaura, Minato-ku, Tokyo No. 1 Inside NTT Facilities Co., Ltd. (72) Inventor Akihiko Naganaga 3-4-1 Shibaura, Minato-ku, Tokyo F-term inside NTT Facilities Co., Ltd. 5K042 AA01 AA06 BA08 CA02 CA13 DA01 EA01 FA10 FA11 FA17 LA06 5K067 AA02 AA03 BB02 BB45 EE02 EE10 LL11

Claims (10)

[Claims] 1. A communication characteristic control method of an indoor wireless communication system for controlling communication characteristics of a wireless communication system which is arranged in a same indoor place and is configured by a wireless base station and one or more terminal stations, The radio wave propagation characteristics between the radio base station and the terminal station located at a specific position, or the radio wave propagation characteristics between a radio station belonging to another radio communication system and the terminal station are obtained by simulation or measurement. Based on the obtained radio wave propagation characteristics, one or more communication characteristic control positions where the indoor radio waves need to be absorbed are determined, and a screen having a radio wave absorption function is arranged at the communication characteristic control positions. A communication characteristic control method for an indoor wireless communication system. 2. The communication characteristic control method for an indoor wireless communication system according to claim 1, wherein a radio wave propagation characteristic is obtained again for environmental conditions in a state where the partition is arranged at the communication characteristic control position, and the obtained radio wave propagation characteristic is obtained. Is compared with a predetermined allowable condition. If the radio wave propagation characteristics do not satisfy the allowable condition, at least one of the position, height, width, and radio wave absorption characteristics of the screen is changed to change the environment. A communication characteristic control method for an indoor wireless communication system, wherein a radio wave propagation characteristic under the condition is obtained again, and an environmental condition satisfying the allowable condition is specified. 3. The communication characteristic control method for an indoor wireless communication system according to claim 1, wherein when a plurality of independent wireless communication systems are arranged in the same indoor space, at least based on the obtained radio wave propagation characteristics, A communication characteristic control method for an indoor wireless communication system, wherein one communication characteristic control position is determined in a space between a plurality of wireless base stations belonging to different wireless communication systems. 4. The communication characteristic control method for an indoor wireless communication system according to claim 1, wherein at least one communication characteristic control position faces a metal wall surface based on the obtained radio wave propagation characteristic, and A method of controlling communication characteristics of an indoor wireless communication system, wherein a partition is set at a position separated by a predetermined distance or more and a partition is arranged substantially in parallel with the wall surface. 5. The communication characteristic control method for an indoor wireless communication system according to claim 1, wherein the radio wave propagation characteristic includes a received electric field strength, a delay dispersion value, a bit error rate, a bit error rate, a radio base station and a terminal station. A communication characteristic control method for an indoor wireless communication system, wherein at least one of propagation losses during the communication is determined. 6. The communication characteristic control method for an indoor wireless communication system according to claim 2, wherein a plurality of candidate points are determined at regular intervals in an area where the terminal station can be located indoors, and each of the candidate points is determined. Assuming that the terminal station is arranged, radio wave propagation characteristics are obtained for each position of the candidate point, and until the radio wave propagation characteristics at all positions of the candidate point satisfy the permissible condition, the position of the partition, A communication characteristic control method for an indoor wireless communication system, wherein at least one of a height, a width, and a radio wave absorption characteristic is changed. 7. The communication characteristic control method for an indoor wireless communication system according to claim 1, wherein a simulation of a radio wave propagation characteristic between the wireless base station and the terminal station is performed by using ray tracing. A communication characteristic control method for a wireless communication system. 8. A method for controlling communication characteristics of an indoor wireless communication system for controlling communication characteristics of a wireless communication system which is disposed in the same indoor place and is configured by a wireless base station and one or more terminal stations, It is determined as an environmental condition that a partition having a radio wave absorbing function is arranged at a specific position separated by a predetermined distance from an indoor metal wall surface, and a radio wave propagation characteristic between the wireless base station and the terminal station in the environmental condition. A communication characteristic control method for an indoor wireless communication system, comprising: determining the effect of improving the communication characteristics by the partition from the obtained radio wave propagation characteristics. 9. The communication characteristic control method for an indoor wireless communication system according to claim 8, wherein a radio wave propagation characteristic between the wireless base station and the terminal station is determined for each of a plurality of types of environmental conditions having different partition heights. A communication characteristic control method for an indoor wireless communication system, wherein a preferable environmental condition is specified by comparing radio wave propagation characteristics of a plurality of types of environmental conditions. 10. The communication characteristic control method for an indoor wireless communication system according to claim 8, wherein a simulation of a radio wave propagation characteristic between said wireless base station and said terminal station is performed by using ray tracing. A communication characteristic control method for a wireless communication system.