JP2007037164A - Wireless communication system, leaky transmission path, and antenna array cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate generation of dead areas in an indoor space, and to realize high-speed simulcast transmission that does not have inter-symbol interference at a low cost. <P>SOLUTION: A leaking waveguide 12 is arranged to meander on a ceiling of an indoor space 11 where a wireless LAN is to be operated. One end of the leaking waveguide is connected to a wireless base station unit 13 and the other end thereof is connected to a terminator 14. The wireless base station unit 13 makes wireless communication with a wireless terminal unit 17 via the leaking waveguide 12 by modulation and demodulation in OFDM system. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wireless communication system that performs wireless communication between a wireless base station device and a wireless terminal device indoors.

  As a wireless communication system that performs wireless communication between a wireless base station device and a wireless terminal device indoors, the one shown in FIG. 14 is known. In this configuration, a plurality of wireless base station devices 2 are arranged on the ceiling portion of the indoor 1 where the wireless LAN is operated, and a LAN cable 3 and a power cable 4 are connected to these wireless base station devices 2 from the outside.

  Each of the wireless base station devices 2 performs wireless communication with the wireless terminal device 6 in the cell 5 that is a wireless communication range, but the cell 5 needs to be arranged so as to cover the entire floor surface of the indoor 1. There is. That is, the radio base station apparatus 2 is arranged so that the cells overlap to some extent in view of safety. For example, when the radius of the cell 5 on the floor surface by the radio base station apparatus 2 is set to about 20 m and the floor surface is 50 m square, it is necessary to arrange at least four radio base station apparatuses 2.

In addition, the transmission / reception means via the antenna for the base station to perform wireless communication with the terminal station in the service area and the terminal station having a dead area where the radio wave radiated from the base station does not reach effectively. A transmission / reception means via a relatively large output power line for performing wireless communication, and an antenna or a leakage power supply line is arranged in the insensitive area according to the shape of the insensitive area. By connecting the power transmission / reception means via the power supply line of the base station with a power supply line having a predetermined attenuation constant and a predetermined length, the output level of radio waves radiated from the antenna or the leakage power supply line can be transmitted / received via the antenna of the base station. What is set so as not to exceed the level of radio waves radiated from is known (for example, see Patent Document 1).
Japanese Patent Laid-Open No. 06-188821 (paragraph “0006” etc.)

  However, in the case of the cell division method such as the former, in an indoor environment where there are many fixtures that interfere with radio wave propagation, it is necessary to arrange more radio base station devices in order to eliminate insensitive areas due to fixtures. As a result, the number of radio base station apparatuses used as an increase in the number of radio base station apparatuses and the installation work of radio base station apparatuses accompanying the increase in the number of radio base station apparatuses increases.

  Further, when the number of radio base station apparatuses to be arranged is increased, an incoming wave from each radio base station apparatus causes interference that cancels out between carriers at the antenna end of the receiving side. Therefore, orthogonal frequency division multiplexing modulation (hereinafter referred to as OFDM) Even if a modulation / demodulation scheme that is resistant to multipath interference such as the scheme is used, there is no effect. For this reason, radio waves are simultaneously transmitted from each radio base station apparatus and broadcast to all radio terminal apparatuses. There was a problem that could not. In addition, although it is possible to transmit each radio base station device one by one in time division, there is a problem that it takes a long time to complete information transmission as a whole.

  In the latter case, in addition to the wireless LAN system in which a normal base station is installed, a leakage feeder is further arranged in the insensitive area, and slave radio equipment as dedicated transmission means is provided for this. There is a problem that the overall equipment cost becomes high.

  Therefore, the present invention provides a wireless communication system that can eliminate the occurrence of an insensitive area indoors and can realize high-speed broadcast transmission without intersymbol interference at low cost.

  The present invention includes a leaky transmission path that is disposed indoors and functions as an antenna, and a radio base station apparatus that is connected to the leaky transmission path and performs radio communication with a radio terminal apparatus via the leaky transmission path. When orthogonal frequency division multiplex modulation / demodulation is used for communication modulation / demodulation, and when a wireless terminal device receives multiple incoming waves, multiple incoming waves occupying the main power come from multiple slots in the leaky transmission path In the wireless communication system, the time difference between a plurality of incoming waves occupying the main power falls within the guard interval of the orthogonal frequency division multiplexing modulation / demodulation method.

  According to the present invention, it is possible to provide a wireless communication system that can eliminate the occurrence of an insensitive area indoors and can realize high-speed broadcast transmission without intersymbol interference at low cost.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
As shown in FIG. 1, a leaky waveguide 12 that is a type of leaky transmission path is meandered as a transmission path that functions as an antenna on the ceiling of an indoor 11 such as a store, for example, an indoor 11 where a wireless LAN is operated. It is arranged.

The leaky waveguide 12 is disposed, for example, on the front side of the ceiling panel, the back side of the ceiling panel, or the ceiling panel. When there is no ceiling panel, the leaky waveguide 12 is disposed in the upper space portion of the indoor 11 so as to be hung inside the roof.
As the leaky transmission line, a leaky coaxial cable can be used in addition to the leaky waveguide, but a leaky waveguide with a small transmission loss is more suitable for a low transmission power system such as a wireless LAN.

  As shown in FIG. 2, the leaky waveguide 12 is formed by providing a slot 12b of a predetermined length on a tubular conductor 12a over a whole at regular intervals and covering it with a covering material 12c. Radio waves are transmitted and received between the inside of the wave tube and the external space via the slot 12b.

  The radio wave radiation characteristic of the leaky waveguide 12 has a radiation pattern as shown in FIG. 3 unlike a general single antenna such as a whip antenna or a dipole antenna. That is, the radiation pattern is fan-shaped when viewed from the axial direction of the leaky waveguide 12, and this extends over the entire waveguide. An electric field strength distribution is obtained in the vicinity of the leaky waveguide 12, and an electric field strength distribution that gradually weakens as the distance increases.

  In the case of a 2.4 GHz band or 5 GHz band wireless LAN system having a transmission power of several tens to several hundreds mW, the interval between the leaky waveguides 12 arranged in a meandering manner is set to about 6 m to 10 m. It is reasonable in terms of both economy and economy.

  The leaky waveguide 12 has one end connected to the radio base station apparatus 13 and the other end connected to a terminator 14 as a termination load having a load resistance value equal to the characteristic impedance of the waveguide. The radio base station apparatus 13 is installed on a wall surface that can be easily maintained. In addition, you may install in a ceiling panel etc.

  The radio base station apparatus 13 is connected to a LAN cable 15 and a power cable 16. A plurality of wireless terminal devices 17 that perform wireless communication with the wireless base station device 13 are disposed on the floor surface of the indoor 11.

  In the wireless LAN system having such a configuration, information transmitted to the wireless base station apparatus 13 by the LAN cable 15 is modulated by the OFDM method and is supplied to the leaky waveguide 12 as a high-frequency signal in the 2.4 GHz band or the 5 GHz band. Sent out. While the high-frequency signal propagates through the leaky waveguide 12, a part of the high-frequency signal is radiated as a radio wave from a large number of slots 12b in an angle range of about 180 degrees in the space in the floor surface direction.

  In the wireless terminal device 17, among the slots 12 b of the leaky waveguide 12, a plurality of transmission waves radiated from relatively close slot groups 18 a and 18 b are received particularly strongly as incoming waves. The transmission waves have a time difference until they reach the reception point, but the interval between the leaky waveguides 12 is 10 m, the height of the leaky waveguide 12 from the floor is 3 m, If the distance between the slot group 18a and the slot group 18b is 20 m, the maximum value of the time difference of the incoming waves received by the wireless terminal device 17 is about 90 nsec.

  In the OFDM standard used for wireless LANs, the guard interval that can eliminate the influence of delayed waves is set to 800 nsec. That is, OFDM is a kind of multicarrier transmission scheme, and transmission data is transmitted by a number of subcarriers orthogonal to each other. Each subcarrier transmits a modulation symbol (multi-ary code) composed of an effective symbol period as shown in FIG. 4 and a guard period obtained by copying a part of the effective symbol period.

  Since there are a plurality of reflection paths as well as a direct path between transmission and reception, a plurality of symbols having time differences such as direct waves, reflected waves R1, R2, and R3 are received on the reception side as shown in FIG. Is done. On the receiving side, the composite wave in the Ts section includes only the component of the effective symbol j even if the arrangement order is different. This indicates that by adding a guard interval on the transmission side, the components of the preceding and following symbols i and k are not included in the interval Ts if the delayed wave is within the time difference of the guard interval. On the receiving side, OFDM demodulation can be performed without receiving interference with an adjacent symbol section by Fourier-transforming the portion cut out in this section Ts.

  In this way, by transmitting and receiving information between the radio base station apparatus 13 and the radio terminal apparatus 17 by the OFDM scheme, the radio terminal apparatus 17 receives the incoming waves from the slot group 18a and the slot group 18b and performs OFDM demodulation, Information can be acquired reliably. Even if the transmission wave from the slot group 18a is completely blocked by an obstacle such as a person or a fixture, the remaining transmission wave from the slot group 18b reaches the receiving antenna.

  That is, even if the transmission wave from the wireless terminal device 17 has some kind of obstacle, there is a propagation path that is not affected by any obstacle with any of the slots 12b on the leakage waveguide 12, so that the leakage guide The wave tube 12 is reached.

  In addition, the receiving antenna of the wireless terminal device 17 receives a large number of incoming waves, but these are radiated from a large number of slots 12b, and the phase difference of each incoming wave is different in very small steps. Can be considered almost continuous. Therefore, even if there are some combinations of incoming waves that completely cancel each other with a phase difference of 180 degrees at the receiving antenna, there is effective received power due to the majority of the remaining incoming waves.

  On the other hand, the OFDM method is resistant to delayed waves that arrive in the guard interval in the demodulation process on the reception side, and therefore there are multiple time differences on the reception side when there are multiple transmission sources or when there are multipaths due to reflected waves. Even when a certain radio wave is received, there is little deterioration in transmission quality due to intersymbol interference in the demodulation stage. Therefore, when a large number of incoming waves having different phases are received, normal demodulation is performed if the maximum time difference between the plurality of incoming waves occupying the main power is within the guard interval.

  As described above, since the leaky waveguide 12 is used as the antenna of the radio base station apparatus 13, even if there are many fixtures in the indoor 11, it is possible to communicate with the radio terminal apparatuses 17 scattered in the indoor 11. The radio wave propagation path between them can be ensured. Further, since the OFDM system is used for modulation / demodulation between the radio base station apparatus 13 and each radio terminal apparatus 17, it is possible to eliminate the influence of intersymbol interference due to time differences of incoming waves arriving from a large number of radio wave propagation paths. In addition, it is not necessary to arrange a large number of radio base station apparatuses in the indoor 11 and there is no equipment cost. Therefore, the generation of the dead area in the indoor 11 can be eliminated, and high-speed broadcast transmission without intersymbol interference can be realized at low cost.

  Further, since the leaky waveguide 12 is meanderingly disposed on the ceiling portion of the indoor 11, even if the leaky waveguide 12 does not exist immediately above the radio terminal device 17, Two leaky waveguides 12 pass through a relatively close distance. Therefore, a large number of slots 12 b exist at a relatively close distance to the wireless terminal device 17, and the wireless terminal device 17 can secure a good wireless propagation path with the leaky waveguide 12.

  Here, the leaky waveguide is meandered in the ceiling portion of the indoor 11, but the present invention is not necessarily limited thereto. For example, as shown in FIG. 6, the leaky waveguide 12 may be disposed in a spiral shape on the ceiling portion of the indoor 11, or the leaky waveguide 12 may be provided on the ceiling portion of the indoor 11 as shown in FIG. 7. You may arrange in a zigzag. Further, the leaky waveguide 12 may be disposed under the floor of the indoor 11.

(Second Embodiment)
In addition, the same code | symbol is attached | subjected to the part same as embodiment mentioned above, and detailed description is abbreviate | omitted.
As shown in FIG. 8, for example, three leaky waveguides 21, 22, and 23 are arranged in parallel at predetermined intervals as a leaky transmission path on the ceiling portion of the indoor 11 where the wireless LAN is operated. Yes.

  Each of the leaky waveguides 21, 22, and 23 has the configuration shown in FIG. 2 like the leaky waveguide 12. In the case of a 2.4 GHz band or 5 GHz band wireless LAN system with a transmission power of several tens to several hundreds mW, the interval between the leakage waveguides 21, 22, and 23 is set to about 6 m to 10 m. It is reasonable in terms of both performance and economy.

  Each of the leakage waveguides 21, 22, 23 has one end connected to the power combiner / distributor 24 and the other end terminated as a termination load having a load resistance value equal to the characteristic impedance of the waveguide. , 27. The common terminal of the power combiner / distributor 24 and the radio base station apparatus 13 are connected by a coaxial cable 28.

  Even in such a configuration, the leaky waveguides 21, 22, and 23 function as antennas of the radio base station apparatus 13, so that even if there are many fixtures in the indoor 11, the wireless terminals scattered in the indoor 11 A radio wave propagation path with the device 17 can be reliably ensured. Further, since the OFDM system is used for modulation / demodulation between the radio base station apparatus 13 and each radio terminal apparatus 17, it is possible to eliminate the influence of intersymbol interference due to time differences of incoming waves arriving from a large number of radio wave propagation paths. In addition, it is not necessary to arrange a large number of radio base station apparatuses in the indoor 11 and there is no equipment cost. Therefore, in this embodiment, the same operational effects as those of the above-described embodiment can be obtained.

(Third embodiment)
In addition, the same code | symbol is attached | subjected to the part same as embodiment mentioned above, and detailed description is abbreviate | omitted.
This will be described as an example of a state in which a large number of long product display shelves 31 are arranged on the floor in the room, for example.

  When the leaky waveguide 12 is meandered on the indoor ceiling as in the first embodiment described above, as shown in FIG. The pipes 12 are arranged in a meandering manner so as to traverse the product display shelves 31 in the front-rear direction.

  Further, as in the second embodiment described above, when a plurality of leaky waveguides 21, 22, and 23 are arranged at predetermined intervals on the indoor ceiling portion, as shown in FIG. For a large number of merchandise display shelves 31, leakage waveguides 21, 22, and 23 are disposed across the merchandise display shelves 31.

  Thus, even if the wireless terminal device 17 is installed in the passage sandwiched between the product display shelves 31 by disposing the leakage waveguide so as to cross the product display shelf 31 back and forth. Since the leaky waveguide can always be seen from the radio terminal device 17, the radio terminal device 17 can reliably transmit and receive with the radio base station device 13 via the leaky waveguide without being obstructed by the merchandise display shelf 31. . In addition, since there are a plurality of leaky waveguides that can be seen from the wireless terminal device 17, even if one is temporarily blocked by a person or the like, a propagation path with the leaky waveguide is secured, so that normal communication is possible. Can do.

  Therefore, the wireless LAN system shown in FIG. 9 and FIG. 10 has uniform radio wave radiation and reception of the leaky waveguide even in an environment such as a retail store where a large number of merchandise display shelves are arranged and a large number of customers come and go. Depending on the characteristics, it becomes possible to eliminate insensitive areas hidden behind product display shelves and crowded people and to ensure the stability of communication quality.

(Fourth embodiment)
In this embodiment, an antenna array cable 31 as shown in FIG. 11 is used as a transmission line that functions as an antenna. In the antenna array cable 31, for example, the first antenna portion 33 is disposed in the middle of the high-frequency cable 32 at an interval of 50 cm to 1 m, and the second antenna portion 34 is not a terminator at the end of the high-frequency cable 31. Arranged.

  As shown in FIG. 12 (a), the first antenna section 33 is obtained by patterning a high frequency coupler 331 and an antenna element 332 on a printed circuit board, and the antenna element 332 is a planar patch antenna. . The connection between the first antenna unit 33 and the high-frequency cable 32 is made, for example, via a connector.

  As shown in FIG. 12B, the second antenna unit 34 has no high-frequency coupler and is formed by patterning only the antenna element 341 on a printed circuit board. The antenna element 341 is also a planar patch antenna. It has become. The connection between the second antenna unit 34 and the high-frequency cable 32 is also made through a connector.

  The radio wave radiation characteristic of the antenna array cable 31 having such a configuration is different from a general single-type antenna such as a whip antenna or a dipole antenna, similarly to the above-described leakage waveguide when laid on the ceiling, A belt-like radiation pattern as shown in FIG. 13 is obtained.

  And this antenna array cable 31 is arrange | positioned in ceiling parts, such as the front side of a ceiling panel, a back side, or a ceiling panel similarly to a leaky waveguide. Moreover, when there is no ceiling panel, it hangs inside the roof and arrange | positions in the indoor upper space part.

  The arrangement pattern is meandering as shown in FIG. 1, arranged spirally on the ceiling as shown in FIG. 6, or arranged zigzag on the ceiling as shown in FIG. Set up. Also, as shown in FIG. 8, a plurality of antenna array cables 31 are arranged in parallel at predetermined intervals using a power combiner / distributor.

Furthermore, as shown in FIGS. 9 and 10, when a plurality of product display shelves are arranged, the product display shelves are arranged so as to cross the front and back.
Thus, even if the antenna array cable 31 is used instead of the leaky waveguide, the same effects as those of the above-described embodiments can be obtained.

  In each of the above-described embodiments, the present invention is applied to a wireless LAN system. However, the present invention is not necessarily limited to this. The present invention can also be applied to a wireless communication system that does not use a LAN.

The perspective view which shows the arrangement | positioning relationship of each part which shows 1st Embodiment of this invention. The figure which shows the structure of the leaky waveguide in the embodiment. The figure which shows the electromagnetic wave radiation pattern of the leaky waveguide in the embodiment. The figure which shows the structure of the modulation symbol of the OFDM system used by communication of the embodiment. The figure for demonstrating the effect of the guard area of the OFDM system used by communication of the embodiment. The figure which shows the other example of arrangement | positioning of the leaky waveguide in the same embodiment. The figure which shows the other example of arrangement | positioning of the leaky waveguide in the same embodiment. The perspective view which shows the arrangement | positioning relationship of each part which shows 2nd Embodiment of this invention. The figure which shows an example of the relationship between the arrangement | positioning of the merchandise display shelf in the 3rd Embodiment of this invention, and the meandering arrangement | positioning of a leaky waveguide. The figure which shows the other example of the relationship between arrangement | positioning of the merchandise display shelf in the same embodiment, and arrangement | positioning of a leaking waveguide. The figure which shows the structure of the antenna array cable in the 4th Embodiment of this invention. The figure which shows the structure of the antenna part of the antenna array cable in the embodiment. The figure which shows the electromagnetic wave radiation pattern of the antenna array cable in the embodiment. The perspective view which shows a prior art example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Indoor, 12 ... Leakage waveguide, 13 ... Wireless base station apparatus, 17 ... Wireless terminal device.

Claims (6)

A leaky transmission path that is disposed indoors and functions as an antenna, and a radio base station apparatus that is connected to the leaky transmission path and performs radio communication with the radio terminal apparatus via the leaky transmission path,
When an orthogonal frequency division multiplexing modulation / demodulation method is used for modulation / demodulation method of wireless communication, and the wireless terminal apparatus receives a plurality of incoming waves, a plurality of incoming waves occupying main power arrive from a plurality of slots of the leaky transmission path Therefore, a wireless communication system characterized in that a time difference between a plurality of incoming waves occupying the main power falls within a guard section of an orthogonal frequency division multiplexing modulation / demodulation system.   The leaky transmission line is characterized in that one transmission line is arranged indoors in a meandering, zigzag or spiral shape, one end thereof is connected to the radio base station apparatus, and the other end is connected to a termination load. The wireless communication system according to 1.   A leaky transmission path is a plurality of leaky transmission paths arranged indoors at predetermined intervals in parallel, and one end of each leaky transmission path is connected to a power distribution synthesizer. The wireless communication system according to claim 1, wherein the wireless communication system is connected to a station apparatus. An antenna array cable that is disposed indoors and functions as an antenna, and a radio base station device that is connected to the antenna array cable and performs radio communication with the radio terminal device via the antenna array cable,
When an orthogonal frequency division multiplexing modulation / demodulation method is used as a modulation / demodulation method for wireless communication, and the wireless terminal device receives a plurality of incoming waves, a plurality of incoming waves occupying main power arrive from a plurality of antennas of the antenna array cable Therefore, a wireless communication system characterized in that a time difference between a plurality of incoming waves occupying the main power falls within a guard section of an orthogonal frequency division multiplexing modulation / demodulation system.   The antenna array cable includes a plurality of high-frequency couplers and antennas in the middle of one high-frequency transmission line, and is arranged in a meandering, zigzag, or spiral shape indoors, and one end thereof is connected to a radio base station apparatus. The wireless communication system according to claim 4.   The antenna array cable is a plurality of antenna array cables arranged in parallel indoors at a predetermined interval, and one end of each antenna array cable is connected to a power distribution synthesizer. The wireless communication system according to claim 4, wherein the wireless communication system is connected to a station apparatus.

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