U.S. patent application number 11/664727 was filed with the patent office on 2007-11-15 for wireless lan transmission system and wireless communication terminal.
Invention is credited to Kouichi Masuda, Mariko Nakaso.
Application Number | 20070263578 11/664727 |
Document ID | / |
Family ID | 25531274 |
Filed Date | 2007-11-15 |
United States Patent
Application |
20070263578 |
Kind Code |
A1 |
Nakaso; Mariko ; et
al. |
November 15, 2007 |
Wireless Lan Transmission System and Wireless Communication
Terminal
Abstract
Provided in a wireless LAN transmission system, having
convenience and improved security, in which a wireless
communication terminal located in a wireless communication area is
capable of changing a setting of a connection, and capable of
disconnecting the wireless communication terminal from the
connection if the connection is unnecessary. A control management
section (7) controls a switching section (5) based on an initial
setting (S001). When a beacon signal transmitted from the wireless
communication terminal is detected in a signal monitoring block (8)
(S002), the control management section switches an operation of the
switching section (5) so as to transmit signals outputted from all
of at least one access point (4) to the wireless communication
terminal (S003). If the wireless communication terminal issues a
communication path-setting-change request while the signals
outputted from all of the at least one access point is transmitted
to the wireless communication terminal (S004), the control
management section examines whether the wireless communication
terminal is operated by an authorized user (S005), further
determines whether a setting can be changed in accordance with the
communication path-setting-change request (S006), and updates a
stored setting based on the communication path-setting-change
request (S008). Thereafter, the control management section
transmits a message indicating that a change in the setting has
been completed (S009), and changes the setting of a communication
path to the updated setting thereof (S0101), thereby allowing the
wireless communication terminal to connect with a desired one of
the at least one access point (4) (S011).
Inventors: |
Nakaso; Mariko; (Osaka,
JP) ; Masuda; Kouichi; (Osaka, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK L.L.P.
2033 K. STREET, NW
SUITE 800
WASHINGTON
DC
20006
US
|
Family ID: |
25531274 |
Appl. No.: |
11/664727 |
Filed: |
November 21, 2005 |
PCT Filed: |
November 21, 2005 |
PCT NO: |
PCT/JP05/21341 |
371 Date: |
April 5, 2007 |
Current U.S.
Class: |
370/338 |
Current CPC
Class: |
H04W 84/12 20130101;
H04W 92/14 20130101; H04W 36/0011 20130101; H04W 28/16 20130101;
H04W 36/14 20130101 |
Class at
Publication: |
370/338 |
International
Class: |
H04Q 7/24 20060101
H04Q007/24 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 1, 2001 |
US |
09985193 |
Claims
1. A wireless LAN transmission system capable of allowing a
wireless communication terminal existing in a local area to
communicate with networks inside and outside the local area, the
wireless LAN transmission system comprising: a wireless base
station for forming a wireless communication area in the local
area, and performing a wireless communication with the wireless
communication terminal existing in the wireless communication area
corresponding to the wireless base station, by means of the
wireless LAN transmission system; and a control station including
at least one wireless LAN access point which is connected to the
wireless base station via a wired communication path, wherein the
control station includes: a communication path switching section
for transmitting a signal outputted from each of the at least one
wireless LAN access point to the wireless base station; a control
management section for controlling the communication path switching
section and storing the communication path having been set; and a
beacon signal detecting section for detecting a beacon signal for
active scanning transmitted from the wireless communication
terminal via the wireless base station, when a signal transmitted
to the wireless communication area in which the wireless
communication terminal exists is not a signal transmitted from a
predetermined one of the at least one wireless LAN access point,
but is a signal transmitted from any of the at least one wireless
LAN access point to which the wireless communication terminal is
not permitted to connect, and the control management section has a
control station for controlling the communication path switching
section so as to transmit signals outputted from all of the at
least one wireless LAN access point to the wireless base station
through which the beacon signal has been transmitted, when the
beacon signal is detected in the beacon signal detecting section,
and causes the wireless communication terminal to temporarily
connect with any of the at least one wireless LAN access point to
which the wireless communication terminal is permitted to connect,
by changing the communication path based on the beacon signal, and
causes the wireless communication terminal to permanently connect
with the predetermined one of the at least one wireless LAN access
point to which the wireless communication terminal is permitted to
connect, based on a communication path-setting-change request
transmitted from the wireless communication terminal to the control
management section, while the wireless communication terminal is
temporarily connected with the any of the at least one wireless LAN
access point to which the wireless communication terminal is
permitted to connect.
2. The wireless LAN transmission system according to claim 1,
wherein channels, having frequencies different from each other, are
respectively set for the at least one wireless LAN access point,
the wireless communication terminal is able to transmit a wireless
LAN channel signal corresponding to each of the at least one
wireless LAN access point, and the beacon signal detecting section
includes: a plurality of band path filters having frequency bands
in which the wireless LAN channel signal transmitted from the
wireless communication terminal is inputted to the band path
filters respectively corresponding to the channels, and the
wireless LAN channel signal inputted to each of the band path
filters is extracted; a signal detecting section for detecting a
signal which has passed through each of the band path filters; and
a determination section for determining whether or not the wireless
LAN signal inputted to all of the band path filters is extracted
within a predetermined time period, and determining that the beacon
signal has been transmitted, when it is determined that the
wireless LAN signal inputted to all of the band path filters is
extracted within the predetermined time period.
3. The wireless LAN transmission system according to claim 1,
wherein channels, having frequencies different from each other, are
respectively set for the at least one wireless LAN access point,
the wireless communication terminal is able to transmit a wireless
LAN channel signal corresponding to each of the at least one
wireless LAN access point, and the beacon signal detecting section
includes: two band path filters; and a signal detecting section for
detecting a signal which has passed through each of the band path
filters, wherein the two band path filters have frequency bands in
which the wireless LAN channel signal transmitted from the wireless
communication terminal is inputted to the two band path filters
respectively corresponding to the channels having frequencies
adjacent to each other, and the wireless LAN channel signal
inputted to each of the two band path filters is extracted, and a
determination section for determining whether or not the wireless
LAN signal inputted to all of the two band path filters is
extracted within a predetermined time period, and determining that
the beacon signal has been transmitted, when it is determined that
the wireless LAN signal inputted to all of the two band path
filters corresponding to the channels having the frequencies
adjacent to each other is extracted within the predetermined time
period.
4. The wireless LAN transmission system according to claim 1,
wherein the beacon signal detecting section includes: a conversion
section for frequency-converting a signal; at least two band path
filters for passing the frequency-converted signal; and a signal
detecting section for detecting the signal which has passed through
each of the band path filters, wherein the beacon signal detecting
section has a determination section for determining whether or not
the frequency-converted signal passes through all of the band path
filters within a predetermined time period, and determining that
the beacon signal has been transmitted, when it is determined that
the frequency-converted signal passes through all of the band path
filters within the predetermined time period.
5. A wireless LAN transmission system capable of allowing a
wireless communication terminal existing in a local area to
communicate with networks inside and outside the local area, the
wireless LAN transmission system comprising: a wireless base
station for forming a wireless communication area in the local
area, and performing a wireless communication with the wireless
communication terminal existing in the wireless communication area
corresponding to the wireless base station, by means of the
wireless LAN transmission system; and a control station including
at least one wireless LAN access point which is connected to the
wireless base station via a wired communication path, wherein the
control station includes: a communication path switching section
for transmitting a signal outputted from each of the at least one
wireless LAN access point to the wireless base station; a control
management section for controlling the communication path switching
section and storing the communication path having been set; and a
signal detecting section for detecting a signal transmitted from
the wireless communication terminal via the wireless base station,
wherein when the signal transmitted from the wireless communication
terminal is not detected in the signal detecting section within a
predetermined time period, the control management section changes
the communication path so as not to transmit signals outputted from
all of the at least one wireless LAN access point to the wireless
base station.
6. The wireless LAN transmission system according to claim 5,
wherein the signal detecting section detects a signal corresponding
to a channel set for each of the at least one wireless LAN access
point, and when the signal corresponding to the channel set for
each of the at least one wireless LAN access point is not detected
within a predetermined time period, the control management section
changes the communication path so as not to transmit the signal
corresponding to the channel set for each of the at least one
wireless LAN access point.
7. A wireless LAN transmission system capable of allowing a
wireless communication terminal existing in a local area to
communicate with networks inside and outside the local area, the
wireless LAN transmission system comprising: a wireless base
station for forming a wireless communication area in the local
area, and performing a wireless communication with the wireless
communication terminal existing in the wireless communication area
corresponding to the wireless base station, by means of the
wireless LAN transmission system; and a control station including
at least one wireless LAN access point which is connected to the
wireless base station via a wired communication path, wherein
channels, having frequencies different from each other, are
respectively set for the at least one wireless LAN access point,
the control station includes: a communication path switching
section for transmitting a signal outputted from each of the at
least one wireless LAN access point to the wireless base station; a
control management section for controlling the communication path
switching section and storing the communication path having been
set; and a beacon signal detecting section for detecting a beacon
signal for active scanning transmitted from the wireless
communication terminal via the wireless base station, when a signal
transmitted to the wireless communication area in which the
wireless communication terminal exists is not a signal transmitted
from a predetermined one of the at least one wireless LAN access
point, but is a signal transmitted from any of the at least one
wireless LAN access point to which the wireless communication
terminal is not permitted to connect, and the control management
section has a control station for controlling the communication
path switching section so as to transmit signals outputted from all
of the at least one wireless LAN access point to the wireless base
station through which the beacon signal has been transmitted, when
the beacon signal is detected in the beacon signal detecting
section, and causes the wireless communication terminal to
temporarily connect with any of the at least one wireless LAN
access point to which the wireless communication terminal is
permitted to connect, by changing the communication path based on
the beacon signal, and causes the wireless communication terminal
to permanently connect with the predetermined one of the at least
one wireless LAN access point to which the wireless communication
terminal is permitted to connect, based on a communication
path-setting-change request transmitted from the wireless
communication terminal to the control management section, while the
wireless communication terminal is temporarily connected with the
any of the at least one wireless LAN access point to which the
wireless communication terminal is permitted to connect, and
changes, when the beacon signal detecting section does not detect
signals corresponding to all of the channels or a signal
corresponding to a predetermined one of the channels, the
communication path so as not to transmit the signals outputted from
all of the at least one access point or the signal outputted from
one of the at least one access point set for the predetermined one
of the channels, to the wireless base station through which the
beacon signal has been transmitted.
8. The wireless LAN transmission system according to claim 7,
wherein the control management section changes, at a predetermined
time interval, the communication path so as not to transmit the
signals outputted from all of the at least one access point or the
signal outputted from the one of the at least one access point set
for the predetermined one of the channels, to the wireless base
station, and changes the communication path so as to transmit the
signals outputted from all of the at least one wireless LAN access
point to the wireless base station, when the beacon signal is
detected in the beacon signal detecting section, and operates in
accordance with a communication path setting, which is stored in
the control management section when a predetermined time period has
passed after the beacon signal is detected.
9. A wireless LAN transmission system capable of allowing a
wireless communication terminal existing in a local area to
communicate with networks inside and outside the local area, the
wireless LAN transmission system comprising: a wireless base
station for forming a wireless communication area in the local
area, and performing a wireless communication with the wireless
communication terminal existing in the wireless communication area
corresponding to the wireless base station, by means of the
wireless LAN transmission system; and a control station including
at least one wireless LAN access point which is connected to the
wireless base station via a wired communication path, wherein the
control station includes: a communication path switching section
for transmitting a signal outputted from each of the at least one
wireless LAN access point to the wireless base station; a control
management section for controlling the communication path switching
section and storing the communication path having been set; and a
detection section for detecting unauthorized access from the
wireless communication area, and the control management section
causes the control management section not to transmit, for a
predetermined time period, signals outputted from all of the at
least one wireless LAN access point to the wireless base station,
when the unauthorized access is detected in the detection
section.
10. The wireless LAN transmission system according to claim 1,
wherein the wireless base station has a communication path setting
information displaying section for displaying communication path
setting information, of each of the at least one wireless LAN
access point, which is transmitted from the control station.
11. The wireless LAN transmission system according to claim 5,
wherein the wireless base station has a communication path setting
information displaying section for displaying communication path
setting information, of each of the at least one wireless LAN
access point, which is transmitted from the control station.
12. The wireless LAN transmission system according to claim 7,
wherein the wireless base station has a communication path setting
information displaying section for displaying communication path
setting information, of each of the at least one wireless LAN
access point, which is transmitted from the control station.
13. The wireless LAN transmission system according to claim 9,
wherein the wireless base station has a communication path setting
information displaying section for displaying communication path
setting information, of each of the at least one wireless LAN
access point, which is transmitted from the control station.
14. The wireless LAN transmission system according to claim 10,
wherein the control station includes signal oscillators, whose
number is the same as that of the at least one wireless LAN access
point, for transmitting signals having oscillatory frequencies
different from each other, and superimposes each of the signals
transmitted from the signal oscillators on the signal transmitted
through the communication path from each of the at least one
wireless LAN access point, so as to be transmitted to the wireless
base station, and the wireless base station includes: a detection
section for detecting each of the signals transmitted from the
signal oscillators; and a display section for displaying that the
signal outputted from each of the at least one wireless LAN access
point is transmitted, when the detection section detects each of
the signals transmitted from the signal oscillators.
15. The wireless LAN transmission system according to claim 11,
wherein the control station includes signal oscillators, whose
number is the same as that of the at least one wireless LAN access
point, for transmitting signals having oscillatory frequencies
different from each other, and superimposes each of the signals
transmitted from the signal oscillators on the signal transmitted
through the communication path from each of the at least one
wireless LAN access point, so as to be transmitted to the wireless
base station, and the wireless base station includes: a detection
section for detecting each of the signals transmitted from the
signal oscillators; and a display section for displaying that the
signal outputted from each of the at least one wireless LAN access
point is transmitted, when the detection section detects each of
the signals transmitted from the signal oscillators.
16. The wireless LAN transmission system according to claim 12,
wherein the control station includes signal oscillators, whose
number is the same as that of the at least one wireless LAN access
point, for transmitting signals having oscillatory frequencies
different from each other, and superimposes each of the signals
transmitted from the signal oscillators on the signal transmitted
through the communication path from each of the at least one
wireless LAN access point, so as to be transmitted to the wireless
base station, and the wireless base station includes: a detection
section for detecting each of the signals transmitted from the
signal oscillators; and a display section for displaying that the
signal outputted from each of the at least one wireless LAN access
point is transmitted, when the detection section detects each of
the signals transmitted from the signal oscillators.
17. The wireless LAN transmission system according to claim 13,
wherein the control station includes signal oscillators, whose
number is the same as that of the at least one wireless LAN access
point, for transmitting signals having oscillatory frequencies
different from each other, and superimposes each of the signals
transmitted from the signal oscillators on the signal transmitted
through the communication path from each of the at least one
wireless LAN access point, so as to be transmitted to the wireless
base station, and the wireless base station includes: a detection
section for detecting each of the signals transmitted from the
signal oscillators; and a display section for displaying that the
signal transmitted from each of the at least one wireless LAN
access point is transmitted, when the detection section detects
each of the signals outputted from the signal oscillators.
18. A wireless communication terminal for communicating with
networks inside and outside a local area by using the wireless LAN
transmission system according to claim 1, the wireless
communication terminal comprising: a transmission section for
transmitting a beacon signal, when a signal transmitted to the
wireless communication area in which the wireless communication
terminal exists is not a signal transmitted from a predetermined
one of the at least one wireless LAN access point, but is a signal
transmitted from any of the at least one wireless LAN access point
to which the wireless communication terminal is not permitted to
connect, in the wireless transmission system, wherein when a signal
is transmitted, in response to the transmitted beacon signal, to
the wireless communication terminal from any of the at least one
wireless LAN access point to which the wireless communication is
permitted to connect, the wireless communication terminal receives
the signal via a wireless base station included in the wireless LAN
transmission system, and temporarily connects with the any of the
at least one wireless LAN access point which has transmitted the
signal, and transmits a communication path-setting-change request
to the control management section included in the wireless LAN
transmission system, while the wireless communication terminal is
temporarily connected with the any of the at least one wireless LAN
access point, and permanently connects with the predetermined one
of the at least one wireless LAN access point to which the wireless
communication terminal is permitted to connect, after a setting of
a communication path is changed in accordance with the
communication path-setting-change request.
19. A wireless communication terminal for communicating with
networks inside and outside a local area by using the wireless LAN
transmission system according to claim 5, the wireless
communication terminal comprising: a transmission section for
transmitting a beacon signal, when a signal transmitted to the
wireless communication area in which the wireless communication
terminal exists is not a signal transmitted from a predetermined
one of the at least one wireless LAN access point, but is a signal
transmitted from any of the at least one wireless LAN access point
to which the wireless communication terminal is not permitted to
connect, in the wireless transmission system, wherein when a signal
is transmitted, in response to the transmitted beacon signal, to
the wireless communication terminal from any of the at least one
wireless LAN access point to which the wireless communication is
permitted to connect, the wireless communication terminal receives
the signal via a wireless base station included in the wireless LAN
transmission system, and temporarily connects with the any of the
at least one wireless LAN access point which has transmitted the
signal, and transmits a communication path-setting-change request
to the control management section included in the wireless LAN
transmission system, while the wireless communication terminal is
temporarily connected with the any of the at least one wireless LAN
access point, and permanently connects with the predetermined one
of the at least one wireless LAN access point to which the wireless
communication terminal is permitted to connect, after a setting of
a communication path is changed in accordance with the
communication path-setting-change request.
20. A wireless communication terminal for communicating with
networks inside and outside a local area by using the wireless LAN
transmission system according to claim 7, the wireless
communication terminal comprising: a transmission section for
transmitting a beacon signal, when a signal transmitted to the
wireless communication area in which the wireless communication
terminal exists is not a signal transmitted from a predetermined
one of the at least one wireless LAN access point, but is a signal
transmitted from any of the at least one wireless LAN access point
to which the wireless communication terminal is not permitted to
connect, in the wireless transmission system, wherein when a signal
is transmitted, in response to the transmitted beacon signal, to
the wireless communication terminal from any of the at least one
wireless LAN access point to which the wireless communication is
permitted to connect, the wireless communication terminal receives
the signal via a wireless base station included in the wireless LAN
transmission system, and temporarily connects with the any of the
at least one wireless LAN access point which has transmitted the
signal, and transmits a communication path-setting-change request
to the control management section included in the wireless LAN
transmission system, while the wireless communication terminal is
temporarily connected with the any of the at least one wireless LAN
access point, and permanently connects with the predetermined one
of the at least one wireless LAN access point to which the wireless
communication terminal is permitted to connect, after a setting of
a communication path is changed in accordance with the
communication path-setting-change request.
21. A wireless communication terminal for communicating with
networks inside and outside a local area by using the wireless LAN
transmission system according to claim 9, the wireless
communication terminal comprising: a transmission section for
transmitting a beacon signal, when a signal transmitted to the
wireless communication area in which the wireless communication
terminal exists is not a signal transmitted from a predetermined
one of the at least one wireless LAN access point, but is a signal
transmitted from any of the at least one wireless LAN access point
to which the wireless communication terminal is not permitted to
connect, in the wireless transmission system, wherein when a signal
is transmitted, in response to the transmitted beacon signal, to
the wireless communication terminal from any of the at least one
wireless LAN access point to which the wireless communication is
permitted to connect, the wireless communication terminal receives
the signal via a wireless base station included in the wireless LAN
transmission system, and temporarily connects with the any of the
at least one wireless LAN access point which has transmitted the
signal, and transmits a communication path-setting-change request
to the control management section included in the wireless LAN
transmission system, while the wireless communication terminal is
temporarily connected with the any of the at least one wireless LAN
access point, and permanently connects with the predetermined one
of the at least one wireless LAN access point to which the wireless
communication terminal is permitted to connect, after a setting of
a communication path is changed in accordance with the
communication path-setting-change request.
Description
TECHNICAL FIELD
[0001] The present invention relates to a system for transmitting
any of a plurality of wireless LAN signals to a wireless base
station, and more particularly to a wireless LAN transmission
system, having convenience and a high level of security, in which a
wireless communication terminal is capable of performing connection
and disconnection settings.
BACKGROUND ART
[0002] In general, a conventional wireless LAN system operating in
an infrastructure mode comprises a wireless communication terminal
and a wireless LAN access point (hereinafter referred to as an
access point), and a communication is performed between the
wireless communication terminal and the access point by means of a
wireless communication path. The access point is installed indoors
or outdoors, and if a wireless communication terminal is located in
an area where a wireless signal transmitted from an access point
can be received, the wireless communication terminal can
communicate with the access point. Typically, when the wireless LAN
system, which complies with IEEE 802.11a or IEEE 802.11b, is used
indoors where line of sight visibility is good, a communication can
be performed within a range of a radius of 50 m or 100 m,
respectively.
[0003] Therefore, if the wireless communication terminal is moved
away from the access point to another area in which the wireless
signal cannot be received, the wireless communication terminal
cannot communicate with the access point.
[0004] Also, in recent years, in order to improve security, when a
wireless communication terminal communicates with an access point,
a password certification such as a WEP (Wired Equivalent Privacy)
or a MAC certification is performed. In a case where these
certifications are performed, the wireless communication terminal
can connect to only an access point to which the wireless
communication terminal is previously permitted to connect. Even
when a wireless communication terminal is located in a
communication area of an access point, the wireless communication
terminal cannot communicate with the access point without a
permission to connect to the access point.
[0005] In order to solve such problems, there is a wireless LAN
system in which a control station controls communication paths of a
plurality of wireless LAN signals, and any of the wireless LAN
signals is optically transmitted to an arbitrary wireless base
station. FIG. 13 is a diagram illustrating a configuration of a
conventional wireless LAN transmission system. In the wireless LAN
transmission system shown in FIG. 13, a control station 3b is
connected to a plurality of wireless base stations 14a and 14b via
a plurality of optical fibers 12a and 12b, respectively.
Furthermore, a great number of wireless communication terminals
(not shown) exist in each of the wireless communication areas 23a
and 23b, where the wireless base stations can perform a wireless
communication, respectively. Hereinafter, an operation of the
conventional wireless LAN transmission system will be described
with reference to FIG. 13.
[0006] The control station 3b includes a plurality of access points
4a to 4d, a plurality of optical transmission/reception sections
11a to 11d, a switching section 5, and a control management section
7 for controlling and managing the switching section 5. In general,
an access point releases a modulated signal, as a wireless signal,
into the air via an antenna. However, each of the access points 4a
to 4d outputs the modulated signal, not as the wireless signal but
as an electric signal, to a transmission path via a coaxial cable.
For example, taking the access point 4a as an example among the
access points 4a to 4d, when a signal outputted from the access
point 4a is transmitted to the wireless communication area 23a, the
control station 3b firstly causes the switching section 5 to
transmit an electric signal outputted from the access point 4a to
the optical transmission/reception section 11a, and then causes the
optical transmission/reception section 11a to convert the electric
signal into an optical signal and to transmit the optical signal to
the wireless base station 14a via the optical fiber 12a.
Thereafter, the optical signal is reconverted into an electric
signal in an optical transmission/reception section 17a included in
the wireless base station 14a, and the electric signal is
transmitted, as a wireless LAN signal, from an antenna section 22a
to the wireless communication terminals located in the wireless
communication area 23a. Similarly, when signals outputted from a
plurality of access points are transmitted to one wireless
communication area, or when a signal outputted from one access
point is transmitted to a plurality of wireless communication
areas, the control management section 7 controls the switching
section 5 so as to set a desired commutation state.
[0007] As described above, the conventional wireless LAN
transmission system changes a communication path of a signal
outputted from an access point with which a wireless communication
terminal is permitted to communicate, thereby making it possible to
allow the wireless communication terminal located in any of the
wireless communication areas to communicate with any of the access
points. Furthermore, the aforementioned system interrupts a signal
outputted from an access point to an unnecessary communication
area, thereby making it possible to improve security.
[0008] [Patent Document 1] International Publication No. WO
04/036832
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0009] In the conventional wireless LAN transmission system, the
control management section 7 performs a setting of a connection
between each of the access points and each of the wireless
communication areas, and changes the setting of the connection
therebetween. In general, the control management section 7 is
installed inside or in the vicinity of the control station 3b, or
in other areas. As methods of causing the control management
section 7 to change the setting the connection mentioned above, a
user of a wireless communication terminal visits the control
station 3b so as to directly cause the control management section 7
to change the setting of the connection, or the user remotely
causes the control management section 7 to change the setting of
the connection via a network. However, it is cumbersome for the
user of the wireless communication terminal to visit the control
station 3b. Even when the user of the wireless communication
terminal remotely causes the control management section 7 to change
the setting of the connection, he or she is required to enter a
wireless communication area which is accessible to the control
management section 7. That is, when a user located in a wireless
communication area operates a wireless communication terminal to
perform a communication, and a signal, outputted from an access
point to which the wireless communication terminal is permitted to
connect, is not transmitted to the wireless communication area,
there is a problem in that the user must move once to an
environment in which he or she can control the control management
section 7, i.e., another wireless communication area receiving the
signal outputted from the access point to which the wireless
communication terminal is permitted to connect, change the setting
of the connection, and return to the wireless communication
area.
[0010] Furthermore, in the conventional wireless LAN transmission
system, if a connection setting is once performed so as to transmit
a signal outputted from an access point to a wireless communication
area, and a disconnection setting for interrupting the signal fails
to be performed even after a communication is ended, there is
another problem in that the signal outputted from the access point
continues to be transmitted to the wireless communication area even
during an unnecessary time period, thereby increasing a possibility
that a malicious third party located in the wireless communication
area may connect to the network.
[0011] Therefore, an object of the present invention is to provide
a wireless LAN transmission system, having convenience and a high
level of security, in which a wireless communication terminal is
capable of, regardless of whether the wireless communication
terminal is located in a wireless communication area corresponding
to an access point to which the wireless communication terminal is
permitted to connect, or the wireless communication terminal moves
to another wireless communication area corresponding to another
access point to which the wireless communication terminal is not
permitted to connect, changing a connection setting while being in
either of the wireless communication areas, establishing a
communication with a desired access point to which the wireless
communication terminal is permitted to connect, and disconnecting
the wireless communication terminal from the access point, when
necessary.
Solution to the Problems
[0012] The present invention is a wireless LAN transmission system
capable of allowing a wireless communication terminal existing in a
local area to communicate with networks inside and outside the
local area, the wireless LAN transmission system comprising: a
wireless base station for forming a wireless communication area in
the local area, and performing a wireless communication with the
wireless communication terminal existing in the wireless
communication area corresponding to the wireless base station, by
means of the wireless LAN transmission system; and a control
station including at least one wireless LAN access point which is
connected to the wireless base station via a wired communication
path, wherein the control station includes: a communication path
switching section for transmitting a signal outputted from each of
the at least one wireless LAN access point to the wireless base
station; a control management section for controlling the
communication path switching section and storing the communication
path having been set; and a beacon signal detecting section for
detecting a beacon signal for active scanning transmitted from the
wireless communication terminal via the wireless base station, when
a signal transmitted to the wireless communication area in which
the wireless communication terminal exists is not a signal
transmitted from a predetermined one of the at least one wireless
LAN access point, but is a signal transmitted from any of the at
least one wireless LAN access point to which the wireless
communication terminal is not permitted to connect, and the control
management section has a control station for controlling the
communication path switching section so as to transmit signals
outputted from all of the at least one wireless LAN access point to
the wireless base station through which the beacon signal has been
transmitted, when the beacon signal is detected in the beacon
signal detecting section, and causes the wireless communication
terminal to temporarily connect with any of the at least one
wireless LAN access point to which the wireless communication
terminal is permitted to connect, by changing the communication
path based on the beacon signal, and causes the wireless
communication terminal to permanently connect with the
predetermined one of the at least one wireless LAN access point to
which the wireless communication terminal is permitted to connect,
based on a communication path-setting-change request transmitted
from the wireless communication terminal to the control management
section, while the wireless communication terminal is temporarily
connected with the any of the at least one wireless LAN access
point to which the wireless communication terminal is permitted to
connect.
[0013] In a case where the wireless LAN wireless communication
terminal is not connected to any of the at least one access point,
a method, in which the wireless LAN communication terminal
transmits a probe request frame as the beacon signal, and searches
for the predetermined one of the at least one access point based on
a response for the beacon signal, is used (active scanning).
[0014] According to the present invention, when the control station
detects the beacon signal for active scanning, the signals
outputted from all of the at least one access point are transmitted
to the wireless base station, thereby allowing the wireless
communication terminal to communicate with any of the at least one
access point to which the wireless communication terminal is
permitted to connect, while receiving the signals outputted from
all of the at least one access point. Thus, the wireless
communication terminal is able to connect to the control management
section via the network, thereby making it possible to change a
connection setting so that the signal outputted from the
predetermined one of the at least one access point (among any of
the at least one access point to which the wireless communication
terminal is permitted to connect) is to be permanently transmitted
to the wireless communication area in which the wireless
communication terminal exists. Thereafter, the wireless
communication terminal is also able to interrupt, based on the
changed connection setting, signals outputted from any of the at
least one access point which is unnecessary, thereby making it
possible to improve security.
[0015] Note that the control management section is preferably
configured so as to operate in accordance with a setting, of the
communication path, which is stored in the control management
section when a predetermined time period has passed after the
beacon signal is detected.
[0016] According to the present invention, it is preferable that
channels, having frequencies different from each other, are
respectively set for the at least one wireless LAN access point,
the wireless communication terminal is able to transmit a wireless
LAN channel signal corresponding to each of the at least one
wireless LAN access point, and the beacon signal detecting section
includes: a plurality of band path filters having frequency bands
in which the wireless LAN channel signal transmitted from the
wireless communication terminal is inputted to the band path
filters respectively corresponding to the channels, and the
wireless LAN channel signal inputted to each of the band path
filters is extracted; a signal detecting section for detecting a
signal which has passed through each of the band path filters; and
a determination section for determining whether or not the wireless
LAN signal inputted to all of the band path filters is extracted
within a predetermined time period, and determining that the beacon
signal has been transmitted, when it is determined that the
wireless LAN signal inputted to all of the band path filters is
extracted within the predetermined time period.
[0017] After the wireless communication terminal transmits the
beacon signal for the probe request while active scanning is
performed, a timer waits for a time period called a minimum channel
monitoring time. When no response is transmitted from any of the at
least one access point after the minimum channel monitoring time
has passed, the wireless communication terminal searches for
another channel.
[0018] On the other hand, when the response is transmitted from the
aforementioned access point within the minimum channel monitoring
time, the wireless communication terminal continues to monitor the
channel. When a time measured by the timer reaches a time period
called a maximum channel monitoring time, the control management
section performs a response process based on the received probe
request. Thereafter, if a communication is established, the channel
is fixed so as to continue the communication. Therefore, the band
path filters, for respectively passing the plurality of wireless
LAN signals corresponding to the channels, are provided in the
control station. When the signals passed through all of the band
path filters are detected within the predetermined time period, it
can be determined that the beacon signal for active scanning has
been transmitted from the wireless base station.
[0019] According to the present invention, it is preferable that
channels, having frequencies different from each other, are
respectively set for the at least one wireless LAN access point,
the wireless communication terminal is able to transmit a wireless
LAN channel signal corresponding to each of the at least one
wireless LAN access point, and the beacon signal detecting section
includes: two band path filters; and a signal detecting section for
detecting a signal which has passed through each of the band path
filters, wherein the two band path filters have frequency bands in
which the wireless LAN channel signal transmitted from the wireless
communication terminal is inputted to the two band path filters
respectively corresponding to the channels having frequencies
adjacent to each other, and the wireless LAN channel signal
inputted to each of the two band path filters is extracted, and a
determination section for determining whether or not the wireless
LAN signal inputted to all of the two band path filters is
extracted within a predetermined time period, and determining that
the beacon signal has been transmitted, when it is determined that
the wireless LAN signal inputted to all of the two band path
filters corresponding to the channels having the frequencies
adjacent to each other is extracted within the predetermined time
period.
[0020] Generally in the wireless LAN system, when a plurality of
access points are used, interference occurs between channels having
adjacent frequencies. Thus, a frequency interval is provided
between each two of the channels. Therefore, two band path filters,
respectively corresponding to two channels having frequencies
adjacent to each other, are intentionally provided, thereby
detecting whether a signal passes through the both band path
filters. Thus, it can be determined that the beacon signal is
transmitted as a special signal from the wireless base station,
thereby making it possible to further simplify a configuration of
the system, as compared to the case where three or more band path
filters are provided.
[0021] According to the present invention, it is preferable that
the beacon signal detecting section includes: a conversion section
for frequency-converting a signal; at least two band path filters
for passing the frequency-converted signal; and a signal detecting
section for detecting the signal which has passed through each of
the band path filters, wherein the beacon signal detecting section
has a determination section for determining whether or not the
frequency-converted signal passes through all of the band path
filters within a predetermined time period, and determining that
the beacon signal has been transmitted, when it is determined that
the frequency-converted signal passes through all of the band path
filters within the predetermined time period. Each of the band path
filters preferably has a pass band corresponding to a wavelength of
a wireless LAN signal which has been frequency-converted.
[0022] Therefore, the band path filters can be simplified, and can
be smaller in size.
[0023] The present invention is a wireless LAN transmission system
capable of allowing a wireless communication terminal existing in a
local area to communicate with networks inside and outside the
local area, the wireless LAN transmission system comprising: a
wireless base station for forming a wireless communication area in
the local area, and performing a wireless communication with the
wireless communication terminal existing in the wireless
communication area corresponding to the wireless base station, by
means of the wireless LAN transmission system; and a control
station including at least one wireless LAN access point which is
connected to the wireless base station via a wired communication
path, wherein the control station includes: a communication path
switching section for transmitting a signal outputted from each of
the at least one wireless LAN access point to the wireless base
station; a control management section for controlling the
communication path switching section and storing the communication
path having been set; and a signal detecting section for detecting
a signal transmitted from the wireless communication terminal via
the wireless base station, wherein when the signal transmitted from
the wireless communication terminal is not detected in the signal
detecting section within a predetermined time period, the control
management section changes the communication path so as not to
transmit signals outputted from all of the at least one wireless
LAN access point to the wireless base station.
[0024] Thus, when no signal is detected in the signal detecting
section of the control station for the predetermined time period,
i.e., when no wireless communication terminal exists in the
communication area formed by the wireless base station, the control
management section physically interrupts the signals outputted from
all of the at least one wireless LAN access point. Therefore, since
no signal is outputted to the communication area during an
unnecessary time period, a malicious third party cannot tap or
intercept a signal, or cannot connect to the network, thereby
making it possible to improve the security.
[0025] According to the present invention, it is preferable that
the signal detecting section detects a signal corresponding to a
channel set for each of the at least one wireless LAN access point,
and when the signal corresponding to the channel set for each of
the at least one wireless LAN access point is not detected within a
predetermined time period, the control management section changes
the communication path so as not to transmit the signal
corresponding to the channel set for each of the at least one
wireless LAN access point.
[0026] Thus, it becomes possible to manage a timing of
disconnecting the wireless communication terminal from each of the
at least one access point. As compared with a case where the
wireless communication terminal is disconnected from all of the at
least one access point when no signal transmitted from the wireless
communication terminal is detected, the security can be further
improved.
[0027] The present invention is a wireless LAN transmission system
capable of allowing a wireless communication terminal existing in a
local area to communicate with networks inside and outside the
local area, the wireless LAN transmission system comprising: a
wireless base station for forming a wireless communication area in
the local area, and performing a wireless communication with the
wireless communication terminal existing in the wireless
communication area corresponding to the wireless base station, by
means of the wireless LAN transmission system; and a control
station including at least one wireless LAN access point which is
connected to the wireless base station via a wired communication
path, wherein channels, having frequencies different from each
other, are respectively set for the at least one wireless LAN
access point, the control station includes: a communication path
switching section for transmitting a signal outputted from each of
the at least one wireless LAN access point to the wireless base
station; a control management section for controlling the
communication path switching section and storing the communication
path having been set; and a beacon signal detecting section for
detecting a beacon signal for active scanning transmitted from the
wireless communication terminal via the wireless base station, when
a signal transmitted to the wireless communication area in which
the wireless communication terminal exists is not a signal
transmitted from a predetermined one of the at least one wireless
LAN access point, but is a signal transmitted from any of the at
least one wireless LAN access point to which the wireless
communication terminal is not permitted to connect, and the control
management section has a control station for controlling the
communication path switching section so as to transmit signals
outputted from all of the at least one wireless LAN access point to
the wireless base station through which the beacon signal has been
transmitted, when the beacon signal is detected in the beacon
signal detecting section, and causes the wireless communication
terminal to temporarily connect with any of the at least one
wireless LAN access point to which the wireless communication
terminal is permitted to connect, by changing the communication
path based on the beacon signal, and causes the wireless
communication terminal to permanently connect with the
predetermined one of the at least one wireless LAN access point to
which the wireless communication terminal is permitted to connect,
based on a communication path-setting-change request transmitted
from the wireless communication terminal to the control management
section, while the wireless communication terminal is temporarily
connected with the any of the at least one wireless LAN access
point to which the wireless communication terminal is permitted to
connect, and changes, when the beacon signal detecting section does
not detect signals corresponding to all of the channels or a signal
corresponding to a predetermined one of the channels, the
communication path so as not to transmit the signals outputted from
all of the at least one access point or the signal outputted from
one of the at least one access point set for the predetermined one
of the channels, to the wireless base station through which the
beacon signal has been transmitted.
[0028] Thus, when any of the at least one access point is not used,
no signal is transmitted from the any of the at least one access
point to the wireless communication terminal via the wireless base
station, thereby improving the security. Also, when the beacon
signal for active scanning transmitted from the wireless
communication terminal is detected, the signals outputted from all
of the at least one access point is once transmitted to the
wireless base station, thereby allowing the wireless communication
terminal to perform a setting of the communication path while
receiving the signals outputted from all of the at least one access
point.
[0029] According to the present invention, it is preferable that
the control management section changes, at a predetermined time
interval, the communication path so as not to transmit the signals
outputted from all of the at least one access point or the signal
outputted from the one of the at least one access point set for the
predetermined one of the channels, to the wireless base station,
and changes the communication path so as to transmit the signals
outputted from all of the at least one wireless LAN access point to
the wireless base station, when the beacon signal is detected in
the beacon signal detecting section, and operates in accordance
with a communication path setting, which is stored in the control
management section when a predetermined time period has passed
after the beacon signal is detected.
[0030] Thus, it becomes possible to regularly determine whether the
wireless communication terminal is operated by an authorized user,
thereby making it possible to further improve the security.
[0031] The present invention is a wireless LAN transmission system
capable of allowing a wireless communication terminal existing in a
local area to communicate with networks inside and outside the
local area, the wireless LAN transmission system comprising: a
wireless base station for forming a wireless communication area in
the local area, and performing a wireless communication with the
wireless communication terminal existing in the wireless
communication area corresponding to the wireless base station, by
means of the wireless LAN transmission system; and a control
station including at least one wireless LAN access point which is
connected to the wireless base station via a wired communication
path, wherein the control station includes: a communication path
switching section for transmitting a signal outputted from each of
the at least one wireless LAN access point to the wireless base
station; a control management section for controlling the
communication path switching section and storing the communication
path having been set; and a detection section for detecting
unauthorized access from the wireless communication area, and the
control management section causes the control management section
not to transmit, for a predetermined time period, signals outputted
from all of the at least one wireless LAN access point to the
wireless base station, when the unauthorized access is detected in
the detection section.
[0032] Thus, even when the malicious third party attempts to tap or
intercept a wireless signal, or attempts to connect to the network,
the signals transmitted to the wireless base station are forcefully
interrupted for the predetermined time period, thereby making it
possible to further improve the security.
[0033] According to the present invention, it is preferable that
the wireless base station has a communication path setting
information displaying section for displaying communication path
setting information, of each of the at least one wireless LAN
access point, which is transmitted from the control station.
[0034] Thus, it becomes possible to allow a user of the wireless
communication terminal located in the wireless communication area
to determine one of the at least one access point which has
transmitted a signal to the wireless base station, thereby
providing the user with convenience.
[0035] According to the present invention, it is preferable that
the control station includes signal oscillators, whose number is
the same as that of the at least one wireless LAN access point, for
transmitting signals having oscillatory frequencies different from
each other, and superimposes each of the signals transmitted from
the signal oscillators on the signal transmitted through the
communication path from each of the at least one wireless LAN
access point, so as to be transmitted to the wireless base station,
and the wireless base station includes: a detection section for
detecting each of the signals transmitted from the signal
oscillators; and a display section for displaying that the signal
outputted from each of the at least one wireless LAN access point
is transmitted, when the detection section detects each of the
signals transmitted from the signal oscillators.
[0036] Thus, it becomes possible to allow the wireless base station
to easily determine one of the at least one access point which has
transmitted a signal thereto, thereby making it possible to
simplify the wireless base station.
[0037] The present invention is a wireless communication terminal
for communicating with networks inside and outside a local area by
using the wireless LAN transmission system according to claim 1,
the wireless communication terminal comprising: a transmission
section for transmitting a beacon signal, when a signal transmitted
to the wireless communication area in which the wireless
communication terminal exists is not a signal transmitted from a
predetermined one of the at least one wireless LAN access point,
but is a signal transmitted from any of the at least one wireless
LAN access point to which the wireless communication terminal is
not permitted to connect, in the wireless transmission system,
wherein when a signal is transmitted, in response to the
transmitted beacon signal, to the wireless communication terminal
from any of the at least one wireless LAN access point to which the
wireless communication is permitted to connect, the wireless
communication terminal receives the signal via a wireless base
station included in the wireless LAN transmission system, and
temporarily connects with the any of the at least one wireless LAN
access point which has transmitted the signal, and transmits a
communication path-setting-change request to the control management
section included in the wireless LAN transmission system, while the
wireless communication terminal is temporarily connected with the
any of the at least one wireless LAN access point, and permanently
connects with the predetermined one of the at least one wireless
LAN access point to which the wireless communication terminal is
permitted to connect, after a setting of a communication path is
changed in accordance with the communication path-setting-change
request.
[0038] Thus, in the wireless communication area, it becomes
possible to change a setting of the communication path by using the
wireless communication terminal, and cause the wireless
communication terminal to start communicating with the
predetermined one of the at least one access point.
Effect of the Invention
[0039] According to the present invention, it is possible to
provide a wireless LAN transmission system, having convenience and
a high level of security, in which a wireless communication
terminal is capable of, regardless of whether the wireless
communication terminal is located in a wireless communication area
corresponding to an access point to which the wireless
communication terminal is permitted to connect, or the wireless
communication terminal moves to another wireless communication area
corresponding to another access point to which the wireless
communication terminal is not permitted to connect, establishing a
communication with a desired access point to which the wireless
communication terminal is permitted to connect while being in
either of the wireless communication areas, and disconnecting the
wireless communication terminal from the access point when
necessary.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 is a diagram illustrating a configuration of a
control station according to a first embodiment of the present
invention.
[0041] FIG. 2 is a diagram illustrating a process flow performed by
a control management section according to the first embodiment of
the present invention
[0042] FIG. 3 is diagram illustrating a process flow performed by a
wireless communication terminal according to the first embodiment
of the present invention.
[0043] FIG. 4 is a diagram illustrating a configuration of a beacon
signal monitoring section according to the first embodiment of the
present invention.
[0044] FIG. 5 is a diagram illustrating another configuration of
the beacon signal monitoring section according to the first
embodiment of the present invention.
[0045] FIG. 6 is a diagram illustrating another configuration of
the beacon signal monitoring section according to the first
embodiment of the present invention.
[0046] FIG. 7 is a block diagram illustrating a configuration of a
wireless communication terminal according to the first embodiment
of the present invention.
[0047] FIG. 8 is a diagram illustrating a configuration of a signal
monitoring section according to a second embodiment of the present
invention.
[0048] FIG. 9 is a diagram illustrating another configuration of
the signal monitoring section according to the second embodiment of
the present invention.
[0049] FIG. 10 is a diagram illustrating a configuration of a
control station according to a third embodiment of the present
invention.
[0050] FIG. 11 is a diagram illustrating a configuration of a
channel information transmitting section according to the third
embodiment of the present invention.
[0051] FIG. 12 is a diagram illustrating a wireless base station
according to the third embodiment of the present invention.
[0052] FIG. 13 is a diagram illustrating a configuration of a
conventional wireless LAN transmission system.
DESCRIPTION OF THE REFERENCE CHARACTERS
[0053] 1 Ethernet.RTM. cable [0054] 2 switching hub [0055] 3
control station [0056] 4 access point [0057] 5 switching section
[0058] 6 transmission/reception separating section [0059] 7 control
management section [0060] 8 signal monitoring section block [0061]
9, 15 optical transmission section [0062] 10, 16 optical reception
section [0063] 11, 17 optical transmission/reception section [0064]
12 optical fiber [0065] 13 channel information transmitting block
[0066] 14 wireless base station [0067] 18, 21, 811 band path filter
[0068] 19 signal detecting section block [0069] 20 information
displaying section [0070] 22 antenna section [0071] 23 wireless
communication area [0072] 24 CPU [0073] 25 wireless modulation
section [0074] 26 wireless transmission section [0075] 27 wireless
demodulation section [0076] 28 wireless reception section [0077] 29
communication path-setting-change software storing section [0078]
132 isolator [0079] 812 signal detecting section [0080] 813 AND
circuit [0081] 814 mixer [0082] 815 signal oscillator
BEST MODE FOR CARRYING OUT THE INVENTION
First Embodiment
[0083] FIG. 1 is a diagram illustrating a configuration of a
control station included in a wireless LAN transmission system
according to a first embodiment of the present invention. Note that
in an entire configuration of the wireless LAN transmission system,
the descriptions of the same elements as those shown in FIG. 13
illustrating the configuration of the conventional wireless LAN
transmission system will be omitted.
[0084] The wireless LAN transmission system according to the first
embodiment of the present invention comprises the plurality of
wireless base stations (see FIG. 13) and the control station 3.
[0085] As shown in FIG. 1, the control station 3 includes the
access points 4a to 4d, the switching section 5,
transmission/reception separating sections 6a to 6d, optical
transmission section 9a to 9d, optical reception section 10a to
10d, a signal monitoring section block 8, and the control
management section 7. Note that when it is unnecessary to
distinguish between the access points 4a and 4d, between the
transmission/reception separating sections 6a and 6d, between the
optical transmission sections 9a and 9d, and between the optical
reception section 10a and 10d, the access points 4a to 4d, the
transmission/reception separating sections 6a to 6d, the optical
transmission sections 9a to 9d, and the optical reception section
10a to 10d are generically referred to as the access point 4, the
transmission/reception separating section 6, the optical
transmission section 9, and the optical reception section 10,
respectively.
[0086] When a signal transmitted to a wireless communication area
in which a wireless communication terminal exists is not a signal
transmitted from one desired wireless LAN access point 4, but is a
signal transmitted from another wireless LAN access point to which
the wireless communication terminal is not permitted to connect,
the wireless communication terminal transmits a beacon signal for
active scanning to the control station 3 via the wireless base
station.
[0087] The access point 4a is connected to an external network (not
shown) via an Ethernet.RTM. cable 1a and a switching hub 2. The
access point 4 modulates a signal transmitted from the external
network via the Ethernet.RTM. cable 1a with a wireless LAN signal,
and outputs the modulated signal as an electric signal. In
accordance with a communication path set by the control management
section 7, the switching section 5 connects the outputted signal to
the optical transmission section 9, which corresponds to a wireless
base station to which the signal is to be transmitted. Note that
the optical transmission/reception section 11 is simply shown in
FIG. 13. However, as shown in FIG. 1, the optical
transmission/reception section 11 includes the optical transmission
section 9, the optical reception section 10, and the
transmission/reception separating section 6. The
transmission/reception separating section 6 is operable to achieve
separation between a downlink signal and an uplink signal. The
transmission/reception separating section 6 transmits a signal
outputted from the access point 4 to the optical transmission
section 9, and transmits a signal transmitted from the optical
reception section 10 to the switching section 5.
[0088] A portion of the uplink signal is separated therefrom, and
the signal monitoring section block 8 monitors the beacon signal
for active scanning which is transmitted from each of the wireless
base stations. Note that the signal monitoring section block 8 is
shown as one block in order to simplify the drawing. However, the
signal monitoring section block 8 is a group of functions of
individually monitoring signals transmitted from the optical
reception section 10. Based on monitored information obtained from
the signal monitoring section block 8, the control management
section 7 changes the setting of the communication path. An
operation of the control management section 7 will be described
with reference to FIG. 2. FIG. 2 is a flowchart illustrating the
operation of the control management section 7 according to the
first embodiment of the present invention. FIG. 3 is a flowchart
illustrating process steps performed by a wireless communication
terminal changing a setting of a communication path. Note that the
wireless communication terminal and the wireless base stations are
shown in FIG. 13.
[0089] In a case where the signal monitoring section block 8
detects no beacon signal for active scanning included in a signal
transmitted from each of the wireless base stations, the control
management section 7 controls the switching section 5 so as to set
the communication paths based on an initial setting (see FIG. 2,
S001). When the signal monitoring section block 8 detects a beacon
signal (S002), the control management section 7 changes an
operation of the switching section 5 so as to transmit signals
outputted from all of the access points 4 to a wireless base
station through which the detected beacon signal has been
transmitted (S003).
[0090] While receiving the signals outputted from all of the access
points 4, the wireless communication terminal which has transmitted
the beacon signal (see FIG. 3, ST001 to 003) is connected to the
access point 4 to which the wireless communication terminal is
permitted to connect via the wireless base station (ST004). This is
only a temporary connection. In this state, the control management
section 7 is installed in a network (in the control station 3)
including the access point 4, thereby allowing the wireless
communication terminal to access the control management section 7.
For example, there is a method in which the wireless communication
terminal can remotely control the control management section 7 by
using a network function, or a method in which the wireless
communication terminal can be connected to the control management
section 7 by using a server function, thereby allowing the wireless
communication terminal to display a control screen by means of a
browser. Note that FIG. 1 shows that the control management section
7 is connected to the access point 4 and the switching hub 2 via
the Ethernet.RTM. cable 1b. However, only if the wireless
communication terminal can access the control management section 7
via the access point 4, the control management section 7 and other
elements may be connected to each other in a different manner. When
the wireless communication terminal can access the control
management section 7 via the access point 4 (ST005), and it is
determined that a signal, outputted from the access point 4 to
which the wireless communication terminal is temporarily connected,
is set so as not to be transmitted to a wireless communication area
in which the wireless communication terminal exists (ST006), the
wireless communication terminal transmits a communication
path-setting-change request (ST007), and the communication
path-setting-change request is repeatedly transmitted until a
message, indicating that a change in the setting of the
communication path has been completed, is transmitted to the
wireless communication terminal (ST008). Upon receiving the
communication path-setting-change request from the wireless
communication terminal (S004), the control management section 7
examines whether the wireless communication terminal is operated by
an authorized user by means of a password or a MAC address (S005),
and determines whether it is possible to change the setting of the
communication path in accordance with the communication
path-setting-change request (S006). For example, if an access point
is required to maintain particularly high security, there may be a
case where a network manager previously sets the access point so as
to restrict a communication area, by transmitting a signal only to
a specified communication area. When it is determined that it is
possible to change the setting of the communication path in
accordance with the communication path-setting-change request, a
stored setting is to be updated based on the communication
path-setting-change request (S008). Thereafter, the control
management section 7 transmits to the wireless communication
terminal a message indicating that the change in the setting of the
communication path has been completed (S009), and interrupts
signals corresponding to channels other than a predetermined
channel, so as to realize an updated setting of the communication
path (S010), thereby making it possible to allow the wireless
communication terminal to be connected with the desired access
point via the wireless base station (S011). Thereafter, the
wireless communication terminal is to be permanently connected to
the desired access point. Taking security into consideration, when
the control management section receives no communication
path-setting-change request even after receiving a beacon signal,
or a wireless communication terminal is not operated by an
authorized user, it is preferable that the control management
section interrupts, after a predetermined time period has passed,
the signals corresponding to the channels other than the
predetermined channel based on the initial setting.
[0091] FIG. 4 is a diagram illustrating a detailed configuration of
the signal monitoring section block 8. The signal monitoring
section block 8 includes a plurality of beacon signal monitoring
sections 8a-1, 8a-2, . . . (the remaining sections are not shown)
for monitoring the signals transmitted from the optical reception
section 10. As an example, a function block of monitoring a signal
transmitted from the optical reception section 10a is the beacon
signal monitoring section 8a-1.
[0092] The beacon signal monitoring section 8a-1 includes a
plurality of band path filters 811a to 811n, a plurality of signal
detecting sections 812a to 812n, and an AND circuit 813. Note that
a configuration of each of other beacon signal monitoring sections
is the same as that described above. Each of the band path filters
has a function of passing a wavelength of a wireless LAN signal
corresponding to each of the channels. For example, in a case where
the wireless LAN system which complies with IEEE 802.11a is used,
four band path filters, having center frequencies of 5.17 GHz, 5.19
GHz, 5.21 GHz and 5.23 GHz, and having a pass band of 18 MHz or
less, may be provided so as to correspond to four channels,
respectively. Alternatively, in a case where the wireless LAN
system which complies with IEEE802.11b is used, three band path
filters, having the center frequencies of 2.412 GHz, 2.437 GHz and
2.462 GHz (or a center frequency of 2.484 GHz may be additionally
included), and having a pass band of 22 MHz or less, may be
provided so as to correspond to three channels, respectively (in a
case where the system is used in Japan). Note that depending on a
system configuration, there may be a case where it is not necessary
to provide all of the band path filters mentioned above. At least
one of the band path filters needs to be provided so as to
correspond to a channel which is not used in the system.
[0093] A signal transmitted from the optical reception section 10a
is inputted to the band path filters 811a to 811n, and each of the
signal detecting sections 812a to 812n detects whether the signal
corresponding to each of the channels has been transmitted. Note
that in FIG. 4, the number of the signal detecting sections is the
same as that of the band path filters 811a to 811n. However, the
signal detecting sections, whose number is smaller than that of the
band path filters 811a to 811n, may be switched from one to another
by using a switch or the like at a time interval shorter than a
minimum time period required for monitoring a channel while
performing active scanning, thereby detecting whether or not the
signal corresponding to each of the channels has been
transmitted.
[0094] When the signal, inputted to the band path filters 811a to
811n respectively corresponding to the channels, passes through all
of the band path filters 811a to 811n within a predetermined time
period, the AND circuit 813 outputs a signal so as to notify the
control management section 7 that a beacon signal has been
detected. In general, while active scanning is performed, a
wireless communication terminal sequentially transmits a signal,
changing a channel of the signal every several tens of
microseconds. Therefore, by detecting whether or not the signal
passes through all of the band path filters within several hundreds
of microseconds, it is possible to determine whether or not the
received signal indicates a beacon signal for active scanning. It
is preferable that signals transmitted from the signal detecting
section 812 are retained, for a predetermined time period, in an
element provided between the signal detecting section 812 and the
AND circuit 813, so as to be simultaneously inputted to the control
management section 7.
[0095] Generally in the wireless LAN system, when a plurality of
access points are used, interference occurs between channels having
adjacent frequencies. Thus, a frequency interval is provided
between each two of the channels. Therefore, as shown in FIG. 5,
two band path filters, respectively corresponding to the channels
having frequencies adjacent to each other, are intentionally
provided. At least either of the band path filters is provided so
as to correspond to a channel which is not used in the system.
Therefore, if a signal passes through the both band path filters,
it can be determined that a beacon signal is transmitted from a
wireless base station. As such, a configuration of a beacon signal
monitoring section 8b-1 can be simpler than that of the beacon
signal monitoring section 8a-1 shown in FIG. 4.
[0096] Alternatively, as shown in FIG. 6, a signal transmitted from
the optical reception section 10 may be frequency-converted into a
signal having a frequency lower than a wireless frequency of a
wireless LAN signal, so as to pass through the bandpath filters
811a and 811b. FIG. 6 is a diagram illustrating a configuration of
the beacon signal monitoring section. A basic configuration of a
beacon signal monitoring section 8c-1 is substantially the same as
those of the beacon signal monitoring sections shown in FIGS. 4 and
5, and the beacon monitoring section 8c-1 additionally includes a
mixer 814, and a signal oscillator 815. Note that FIG. 6 shows two
band path filters and two signal detecting sections. However, at
least two band path filters and at least one signal detecting
section are required.
[0097] This is because when only one band path filter is provided,
it is impossible to determine whether a passed signal is an
ordinary wireless LAN signal or a beacon signal.
[0098] A wireless LAN signal received by the optical reception
section 10a is down-converted into a signal having a frequency
lower than the wireless LAN signal by means of the mixer 814 and
the signal oscillator 815, so as to be transmitted to the band path
filters 811a and 811b. Therefore, in this case, center frequencies
of the band path filters 811a and 811b are desirably set to be
lower than those of the band path filters shown in FIG. 4 and FIG.
5. For example, when an oscillatory frequency of the signal
oscillator 815 is 4.89 GHz in the system which comprise with IEEE
802.11a, the center frequencies of the band path filter 811a and
the band path filter 811b may be set to be 280 MHz and 300 MHz,
respectively, and a pass band of both the band path filters 811a
and 811b may be set to be 18 MHz. Due to characteristics of
components used for fabricating a band path filter, the lower a
center frequency of the band path filter is, the more easily the
band path filter can be designed. Thus, as compared to the band
path filters shown in FIG. 4, the band path filters 811a and 811b
shown in FIG. 6 can be fabricated more easily, and can be smaller
in size.
[0099] FIG. 7 is a block diagram illustrating a configuration of a
wireless communication terminal of the present embodiment. The
wireless communication terminal is a wireless communication
terminal for communicating with networks inside and outside a local
area by using the wireless LAN transmission system, and a wireless
transmission section 26 is included therein.
[0100] In the wireless LAN transmission system, when a signal
transmitted to a wireless communication area in which the wireless
communication terminal exists is not a signal transmitted from a
desired wireless LAN access point, but is a signal transmitted from
a wireless LAN access point to which the wireless communication
terminal is not permitted to have access, the wireless transmission
section 26 is able to transmit a beacon signal.
[0101] In response to the transmitted beacon signal, when a signal
is transmitted to the wireless communication terminal from at least
one the wireless LAN access point to which the wireless
communication terminal is permitted to connect, the wireless
communication terminal receives the signal via a wireless base
station included in the wireless LAN transmission system, thereby
temporarily connecting with any of the at least one wireless LAN
access point which has transmitted the signal.
[0102] Then, while temporarily connecting with the aforementioned
access point, the wireless communication terminal transmits the
communication path-setting-change request to the control management
section of the wireless LAN transmission system.
[0103] After a setting of a communication path has been changed in
accordance with the communication path-setting-change request, the
wireless communication terminal permanently connects with a desired
one of the at least one wireless LAN access point.
[0104] Such functions are realized mainly by means of a CPU 24 and
a communication path-setting-change software.
[0105] The wireless communication terminal additionally includes
the CPU 24, a wireless modulation section 25 connected to an output
terminal of the CPU 24, a wireless transmission section 26
connected to the wireless modulation section 25, a wireless
demodulation section 27 connected to an input terminal of the CPU
24, a wireless reception section 28 connected to the wireless
demodulation section 27, and a communication path-setting-change
software storing section 29 individually connected to the CPU
24.
[0106] Software stored in the communication path-setting-change
software storing section 29 outputs a communication
path-setting-change command to the CPU 24, when necessary. The CPU
24 issues a command for transmitting a beacon signal, when
necessary. In response to the command, the wireless transmission
section 26 releases a radio wave of the beacon signal into the air.
Furthermore, in response to the command issued by the CPU 24, the
wireless transmission section 26 releases a radio wave of a signal
of the communication path-setting-change request described above.
After a setting of a communication path is changed, the wireless
communication terminal can permanently communicate with the desired
one of the at least one access point.
Second Embodiment
[0107] A second embodiment of the present invention will be
described with reference to FIG. 1. A basic function of the second
embodiment is the same as that of the first embodiment, and the
descriptions thereof will be omitted.
[0108] In the first embodiment, the signal monitoring section block
8 monitors a beacon signal for active scanning, which is
transmitted from each of the wireless base stations. In contrast,
in the present embodiment, the beacon signal for active scanning
and a data signal, both of which are transmitted from each of the
wireless base stations, are monitored. When no signal is detected
in the signal monitoring section block 8 for a predetermined period
of time, the control management section 7 interrupts the signals
outputted from all of the access points 4 to corresponding wireless
base stations. As described above, in a case where no wireless
communication terminal exists in a communication area, no wireless
signal is to be transmitted to the communication area. Therefore, a
malicious third party cannot tap or intercept a signal, or cannot
connect to the network, thereby making it possible to improve
security.
[0109] Furthermore, the signal monitoring section block 8 may
monitor a signal corresponding to each of the channels. FIG. 8 is a
diagram illustrating a signal monitoring section 8d-1,
corresponding to one of the wireless base stations, which is
included in the signal monitoring section block 8. A basic function
of the signal monitoring section 8d-1 is the same as that of the
beacon signal monitoring section shown in FIG. 4. However, in an
example shown in FIG. 8, the AND circuit 813 is not provided, and
information monitored by the signal detecting section 812 provided
for the signal corresponding to each of the channels is transmitted
to the control management section 7 so as to control an operation.
Therefore, a timing, of disconnecting a wireless communication
terminal from each of the access points, can be managed, thereby
making it possible to further improve the security, as compared
with a case where a wireless communication terminal is disconnected
from all of the access points when no signal transmitted from the
wireless communication terminal is detected.
[0110] Still furthermore, preferably, the signal monitoring section
block 8 may include both the beacon signal monitoring section and
the signal monitoring section. When no signal is detected in the
signal monitoring section, signals outputted from all of the access
points may not be transmitted to a wireless base station, and when
a beacon signal for active scanning is detected, a setting of a
channel may be changed in accordance with the flowchart shown in
FIG. 2. In this case, the beacon signal monitoring section and the
signal monitoring section may be individually provided in the
signal monitoring section block 8. Or as shown in FIG. 9, the band
path filter 811 and the signal detecting section 812 which are the
same as those shown in FIG. 8 are provided, and a wiring connected
between the signal detecting section 812 and the control management
section 7 may be branched, thereby causing an information signal
outputted from the signal detecting section 812 to pass through two
communication paths. Then, the information signal, outputted from
the signal detecting section 812, which passes through one of the
communication paths, may be inputted to the AND circuit 813, and
the information signal, outputted from the signal detecting section
812, which passes through the other of the communication paths, may
be directly inputted to the control management section 7, without
passing through the AND circuit 813.
[0111] In a case of an example shown in FIG. 9, among signals
passing through the signal detecting section 812, by using a signal
which passes through the AND circuit 813, a signal for active
scanning can be monitored, and by using a signal which does not
pass through the AND circuit 813, a wireless LAN signal outputted
from each of the access points, i.e., a wireless LAN signal
corresponding to each of the channels, can be individually
monitored in a similar manner to that shown in FIG. 8, thereby
making it possible to interrupt a signal corresponding to each of
the channels when the signal is unnecessary.
[0112] Furthermore, regardless of the presence or absence of a data
signal, the control management section 7 may switch an operation,
at a predetermined time interval, so as not to transmit signals
outputted from all of the access points or not to transmit a signal
outputted from a predetermined access point. Thereafter, when a
beacon signal is detected, the control management section 7 may
change the setting of the channel in accordance with the flowchart
shown in FIG. 2. Thus, it can be regularly determined whether or
not a user is authorized, thereby making it possible to further
improve the security.
[0113] Still furthermore, the control station 3 may include a
detection section for detecting unauthorized access from a wireless
communication area. As one method of detecting the unauthorized
access, there is a method of counting a time period in which the
signal monitoring section block 8 does not receive a communication
path-setting-change request from a wireless communication terminal,
even in a state where the signal monitoring section block 8 detects
a beacon signal for active scanning. In this case, when an
authorized user operates a wireless communication terminal to
perform a wireless communication in a wireless communication area,
a malicious third party that is not connected to a system or
network may intercept a wireless data signal transmitted and
received by the wireless communication terminal operated by the
authorized user. As another method, there may be a method of
counting, even when the signal monitoring section 8 receives the
communication path-setting-change request after the beacon signal
for active scanning is detected, the number of times in which the
communication path-setting-change request is denied. As such, when
the unauthorized access is determined, it is desirable that
regardless of the presence or absence of the beacon signal for
active scanning and the data signal, the control management section
7 interrupts all the signals once, and returns the system to the
initial setting after a predetermined time period has passed, or
the network manager performs a manual reset.
Third Embodiment
[0114] FIG. 10 is a diagram illustrating a configuration of a
control station of a wireless LAN transmission system according to
a third embodiment of the present invention. Note that an entire
configuration of the wireless LAN transmission system is
substantially the same as that of the conventional wireless LAN
transmission system shown in FIG. 13, and a configuration of the
control station is substantially the same as that of the control
station shown in FIG. 1. Therefore, the descriptions of the same
elements will be omitted.
[0115] The control station 3a of the present embodiment is
different from the control station shown in FIG. 1 in that the
control station 3a includes a channel information transmitting
block 13, and a channel information signal transmitted from the
channel information transmitting block 13 is superimposed on each
of signals passing between the access point 4 and the switching
section 5. Note that the channel information transmitting block 13
is illustrated as one block in order to simplify the drawing.
However, the signal monitoring section block 8 is a group of
functions of individually superimposing the channel information
signals on the wireless LAN signals transmitted from the access
point 4.
[0116] FIG. 11 is a diagram illustrating a detailed configuration
of the channel information transmitting block 13. The channel
information transmitting block 13 includes a plurality of signal
oscillators 131a-A, 131a-B, . . . (the remaining oscillators are
not shown) and a plurality of isolators 132a, . . . (the remaining
isolators are not shown), and oscillatory frequencies of the
plurality of signal oscillators 131a . . . are different from each
other. As an example, a function of superimposing the channel
information signal on a wireless LAN signal transmitted from the
access point 4a is a channel information transmitting section
13a-A. Note that the isolator 132 is operable to prevent frequency
fluctuation to be caused when a signal is reversely inputted to the
signal oscillator 131. If the signal oscillator 131 allows for a
certain amount of the frequency fluctuation, the isolator 132 may
not be provided.
[0117] The channel information signal transmitted from each of the
signal oscillators 131 is superimposed on each of the wireless LAN
signals transmitted from the access point 4, and the switching
section 5 changes a communication path connected to each of the
wireless base stations. For example, when a signal outputted from
the access point 4a is transmitted to a wireless base station, the
channel information signal outputted from the channel information
transmitting section 13a-A is also transmitted simultaneously to
the wireless base station. FIG. 12 is a diagram illustrating a
configuration of a wireless base station included in the wireless
LAN transmission system according to the present embodiment of the
present invention. The wireless base station 14 includes an optical
transmission section 15, an optical reception section 16, bandpath
filters 18 and 21, a signal detecting section 19, an information
displaying section 20, and an antenna 22.
[0118] The wireless LAN signal and the channel information signal,
both of which are transmitted, as an optical signal, from the
control station 3 via the optical fiber 12 is converted into an
electric signal in the optical reception section 16, and the
electric signal is caused to be transmitted through two
communication paths, so as to pass through the band path filters 18
and 21. The band path filter 18 has a pass band for passing the
channel information signal, and the band path filter 21 has a pass
band for passing the wireless LAN signal. Note that an oscillatory
frequency of the signal oscillator 131 may be set to be lower than
that of the wireless LAN signal, so as to use the band path filter
18 as a low pass filter and to use the band path filter 21 as a
high pass filter. Note that the band path filter 18 is operable to
prevent a malfunction, of the signal detecting section block 19, to
be caused by a leakage of a high frequency component. If no
malfunction is caused by the leakage of the high frequency
component, the band path filter 18 may not be provided.
[0119] Next, a configuration of the signal detecting section block
19 will be described with reference to FIG. 8. A basic function of
the signal detecting section block 19 is the same as that of the
signal monitoring section shown in FIG. 8, and the signal detecting
section block 19 is different from the signal monitoring section
shown in FIG. 8 in that a pass band of the band path filter 811
corresponds to an oscillate frequency transmitted from the signal
oscillator 131 (see FIG. 11). Therefore, when a signal having a
frequency corresponding to each of the access points is detected,
information of the signal is displayed by means of the information
displaying section 20.
[0120] Note that it is preferable that a certain frequency interval
is provided between each two of the oscillate frequencies of the
signal oscillator 131, and the harmonic components of each of the
signals outputted from the channel information transmitting block
13 does not overlap with a frequency band of a wireless LAN signal
outputted from each of the access points.
[0121] As described above, by providing a channel information
transmitting section in the control station 3, it becomes possible
to detect channel information by means of a band path filter which
is simpler than that used for directly detecting a channel
corresponding to the wireless LAN signal.
[0122] Furthermore, it is preferable that each of the wireless
communication terminals used in the wireless LAN transmission
system described in the first to fourth embodiments has a function
of transmitting a beacon signal when a signal transmitted to a
wireless communication area in which each of the wireless
communication terminals exists is not a signal transmitted from a
desired access point, of connecting with the desired access point
while the control station 3 transmits signals outputted from all
the access points to the each of the wireless communication
terminals, and of transmitting the communication
path-setting-change request to the control management section.
[0123] Still furthermore, the aforementioned function may be
provided for all of the wireless communication terminals used in
the wireless LAN transmission system of the present invention, or
the aforementioned function may be provided for only a limited
number of specified wireless communication terminals (owned by the
network manager).
INDUSTRIAL APPLICABILITY
[0124] The present invention is applicable to a wireless LAN
transmission system, for example, having the convenience and
improved security, in which a wireless communication terminal
located in a wireless communication area is capable of changing a
setting of a connection, and capable of disconnecting the wireless
communication terminal from the connection if the connection is
unnecessary.
* * * * *