U.S. patent application number 12/750346 was filed with the patent office on 2010-10-14 for wireless communication device, wireless communication system, wireless communication method and program.
Invention is credited to Katsutoshi Itoh, Masahiko NAITO.
Application Number | 20100260158 12/750346 |
Document ID | / |
Family ID | 42462390 |
Filed Date | 2010-10-14 |
United States Patent
Application |
20100260158 |
Kind Code |
A1 |
NAITO; Masahiko ; et
al. |
October 14, 2010 |
WIRELESS COMMUNICATION DEVICE, WIRELESS COMMUNICATION SYSTEM,
WIRELESS COMMUNICATION METHOD AND PROGRAM
Abstract
Provided is a wireless communication device which includes a
notification information transmitting unit for transmitting, via a
wireless communication network, notification information of the
wireless communication device, a notification information receiving
unit for receiving notification information transmitted from
another device, a frequency switching unit for successively
switching, at random cycles, a frequency at which the notification
information is transmitted or a frequency at which the notification
information is received, and a transmission processing unit for
performing a data transmission process after transmitting or
receiving an acknowledgement to the notification information
to/from such other device.
Inventors: |
NAITO; Masahiko; (Tokyo,
JP) ; Itoh; Katsutoshi; (Tokyo, JP) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER;LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Family ID: |
42462390 |
Appl. No.: |
12/750346 |
Filed: |
March 30, 2010 |
Current U.S.
Class: |
370/338 |
Current CPC
Class: |
H04W 84/18 20130101;
H04W 72/0406 20130101; H04W 8/005 20130101; H04W 72/02 20130101;
H04W 84/20 20130101 |
Class at
Publication: |
370/338 |
International
Class: |
H04W 40/00 20090101
H04W040/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 8, 2009 |
JP |
P2009-094369 |
Claims
1. A wireless communication device comprising: a notification
information transmitting unit for transmitting, via a wireless
communication network, notification information of the wireless
communication device; a notification information receiving unit for
receiving notification information transmitted from another device;
a frequency switching unit for successively switching, at random
cycles, a frequency at which the notification information is
transmitted or a frequency at which the notification information is
received; and a transmission processing unit for performing a data
transmission process after transmitting or receiving an
acknowledgement to the notification information to/from such other
device.
2. The wireless communication device according to claim 1, wherein
transmission of the notification information by the transmitting
unit and waiting for receipt of the notification information by the
receiving unit are performed in time-division manner, and wherein
the wireless communication device includes a random period setting
unit for setting a cycle for transmitting the notification
information or a waiting cycle for the receipt of the notification
information to a random period.
3. The wireless communication device according to claim 1,
comprising: an acknowledgement transmitting unit for transmitting,
in case the notification information transmitted from another
device is received by the notification information receiving unit,
the acknowledgement to such other device.
4. The wireless communication device according to claim 1,
comprising: a reception processing unit for receiving the
acknowledgement to the notification information of the wireless
communication device from another device which has received the
notification information of the wireless communication device.
5. The wireless communication device according to claim 1, wherein
transmission of the notification information by the transmitting
unit is performed at a determined specific frequency.
6. The wireless communication device according to claim 1, wherein
reception of the notification information by the receiving unit is
performed at a determined specific frequency.
7. The wireless communication device according to claim 1, wherein
the transmitting unit transmits a beacon as the notification
information, and wherein the receiving unit receives an
acknowledgement to the beacon transmitted as the notification
information.
8. The wireless communication device according to claim 1, wherein
the transmitting unit transmits a probe request as the notification
information, and wherein the receiving unit receives a probe
response to the probe request transmitted as the notification
information.
9. A wireless communication system, comprising: a first wireless
communication device including a first notification information
transmitting unit for transmitting, via a wireless communication
network, notification information of the first wireless
communication device, a first notification information receiving
unit for receiving notification information transmitted from
another device, a first frequency switching unit for successively
switching, at random cycles, a frequency at which the notification
information is transmitted or a frequency at which the notification
information is received, and a first transmission processing unit
for performing a data transmission process after transmitting or
receiving an acknowledgement to the notification information
to/from such other device; and a second wireless communication
device including a second notification information transmitting
unit for transmitting, via the wireless communication network,
notification information of the second wireless communication
device, a second notification information receiving unit for
receiving notification information transmitted from another device,
a second frequency switching unit for successively switching, at
random cycles, a frequency at which the notification information is
transmitted or a frequency at which the notification information is
received, and a second transmission processing unit for performing
a data transmission process after transmitting or receiving an
acknowledgement to the notification information to/from such other
device, wherein the second wireless communication device receives
the notification information transmitted from the first wireless
communication device, transmits the acknowledgement to the first
wireless communication device, and performs the data transmission
process with the first wireless communication device.
10. A wireless communication method, comprising the steps of:
transmitting, via a wireless communication network, notification
information of a wireless communication device; waiting for
notification information transmitted from another device;
successively switching, at random cycles, a frequency at which the
notification information is transmitted or a frequency at which the
notification information is received; and performing a data
transmission process after transmitting or receiving an
acknowledgement to the notification information to/from such other
device.
11. A program for causing a computer to function as: means for
transmitting, via a wireless communication network, notification
information of a wireless communication device; means for receiving
notification information transmitted from another device; means for
successively switching, at random cycles, a frequency at which the
notification information is transmitted or a frequency at which the
notification information is received; and means for performing a
data transmission process after transmitting or receiving an
acknowledgement to the notification information to/from such other
device.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a wireless communication
device, a wireless communication system, a wireless communication
method, and a program.
[0003] 2. Description of the Related Art
[0004] In recent years, due to advantages such as a greater degree
of freedom of devices or the like, a wireless network typified by
IEEE 802.11, which is a LAN standard, is becoming more popular,
taking the place of a wired network, and applications that are used
are becoming more varied.
[0005] Citation List
[0006] Patent Literature
[0007] [Patent Literature 1] JP-A-2005-223767
[0008] [Patent Literature 2] JP-A-2005-151525
[0009] [Patent Literature 3] JP-A-2005-51522
SUMMARY OF THE INVENTION
[0010] In the infrastructure mode of IEEE 802.11, the operation of
an access point (AP) is started first, and notification information
(beacon) is periodically transmitted from the access point at a
frequency that is set in advance. A station (STA) finds the access
point, which is a communication counterpart, by receiving the
beacon transmitted from the access point.
[0011] On the other hand, a method is assumed of determining an
access point and a station by negotiation after connection has been
completed, without distinguishing in advance an access point and a
station among communicating devices. According to this method,
since it is not known at what frequency the counterpart is
operating, notifications, such as beacons, are transmitted while
switching the frequencies, and when the frequencies of devices
match at a certain timing, the notification information can be
received for the first time and connection can be completed.
[0012] However, in this case, if frequency switching timing of a
device matches that of a communication-counterpart device, a
situation is assumed where switching progresses with the frequency
of the devices remaining different and notification information
transmitted from a communication counterpart will not be
received.
[0013] In light of the foregoing, it is desirable to provide a
wireless communication device, a wireless communication system, a
wireless communication method, and a program which are novel and
improved, and which enable to reliably look for a communication
counterpart while switching frequencies.
[0014] According to an embodiment of the present invention, there
is provided a wireless communication device which includes a
notification information transmitting unit for transmitting, via a
wireless communication network, notification information of the
wireless communication device, a notification information receiving
unit for receiving notification information transmitted from
another device, a frequency switching unit for successively
switching, at random cycles, a frequency at which the notification
information is transmitted or a frequency at which the notification
information is received, and a transmission processing unit for
performing a data transmission process after transmitting or
receiving an acknowledgement to the notification information
to/from such other device.
[0015] Transmission of the notification information by the
transmitting unit and waiting for receipt of the notification
information by the receiving unit may be performed in time-division
manner. There may be provided a random period setting unit for
setting a cycle for transmitting the notification information or a
waiting cycle for the receipt of the notification information to a
random period.
[0016] There may be provided an acknowledgement transmitting unit
for transmitting, in case the notification information transmitted
from another device is received by the notification information
receiving unit, the acknowledgement to such other device.
[0017] There may be provided a reception processing unit for
receiving the acknowledgement to the notification information of
the wireless communication device from another device which has
received the notification information of the wireless communication
device.
[0018] Transmission of the notification information by the
transmitting unit may be performed at a determined specific
frequency.
[0019] Reception of the notification information by the receiving
unit may be performed at a determined specific frequency.
[0020] The transmitting unit may transmit a beacon as the
notification information, and the receiving unit may receive an
acknowledgement to the beacon transmitted as the notification
information.
[0021] The transmitting unit may transmit a probe request as the
notification information, and the receiving unit may receive a
probe response to the probe request transmitted as the notification
information.
[0022] According to another embodiment of the present invention,
there is provided a wireless communication system which includes a
first wireless communication device including a first notification
information transmitting unit for transmitting, via a wireless
communication network, notification information of the first
wireless communication device, a first notification information
receiving unit for receiving notification information transmitted
from another device, a first frequency switching unit for
successively switching, at random cycles, a frequency at which the
notification information is transmitted or a frequency at which the
notification information is received, and a first transmission
processing unit for performing a data transmission process after
transmitting or receiving an acknowledgement to the notification
information to/from such other device, and a second wireless
communication device including a second notification information
transmitting unit for transmitting, via the wireless communication
network, notification information of the second wireless
communication device, a second notification information receiving
unit for receiving notification information transmitted from
another device, a second frequency switching unit for successively
switching, at random cycles, a frequency at which the notification
information is transmitted or a frequency at which the notification
information is received, and a second transmission processing unit
for performing a data transmission process after transmitting or
receiving an acknowledgement to the notification information
to/from such other device. The second wireless communication device
may receive the notification information transmitted from the first
wireless communication device, transmit the acknowledgement to the
first wireless communication device, and perform the data
transmission process with the first wireless communication
device.
[0023] According to another embodiment of the present invention,
there is provided a wireless communication method which includes
the steps of transmitting, via a wireless communication network,
notification information of a wireless communication device,
waiting for notification information transmitted from another
device, successively switching, at random cycles, a frequency at
which the notification information is transmitted or a frequency at
which the notification information is received, and performing a
data transmission process after transmitting or receiving an
acknowledgement to the notification information to/from such other
device.
[0024] According to another embodiment of the present invention,
there is provided a program for causing a computer to function as
means for transmitting, via a wireless communication network,
notification information of a wireless communication device, means
for receiving notification information transmitted from another
device, means for successively switching, at random cycles, a
frequency at which the notification information is transmitted or a
frequency at which the notification information is received, and
means for performing a data transmission process after transmitting
or receiving an acknowledgement to the notification information
to/from such other device.
[0025] According to the embodiments of the present invention
described above, there can be provided a wireless communication
device, a wireless communication system, a wireless communication
method, and a program which are novel and improved, and which
enable to reliably look for a communication counterpart while
switching frequencies.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a sequence diagram showing a flow of a sequence
until communication is started between an access point and a
station, in the infrastructure mode of IEEE 802.11;
[0027] FIG. 2 is a sequence diagram showing an example of
transmitting notification information by using a beacon in
communication by direct connection;
[0028] FIG. 3 is a sequence diagram showing a case where frequency
change cycles of a station 1 and a station 2 match;
[0029] FIG. 4 is a block diagram showing an example of the
configuration of a wireless communication device according to each
embodiment of the present invention;
[0030] FIG. 5 is a schematic diagram showing a flow of a sequence
according to a first embodiment; and
[0031] FIG. 6 is a schematic diagram showing a flow of a sequence
according to a second embodiment.
DETAILED DESCRIPTION OF THE EMBODIMENT(S)
[0032] Hereinafter, preferred embodiments of the present invention
will be described in detail with reference to the appended
drawings. Note that, in this specification and the appended
drawings, structural elements that have substantially the same
function and structure are denoted with the same reference
numerals, and repeated explanation of these structural elements is
omitted.
[0033] The explanation will be given in the following order.
1. First Embodiment
[0034] (1) Technical Basis
[0035] (2) Communication Method where Access Point is Not
Determined in Advance and Its Demerit
[0036] (3) Configuration of Wireless Communication Device
[0037] (4) Flow of Processes according to First Embodiment
2. Second Embodiment
[0038] (1) Flow of Processes according to Second Embodiment
1. First Embodiment
[0039] (1) Technical Basis
[0040] Most of the wireless LAN connection modes defined by IEEE
802.11, which is a wireless LAN standard, are an infrastructure
mode of performing communication via an access point. At the time
of connecting wirelessly, a radio has to somehow find a connection
counterpart. To find here means to be in a state where
synchronization of frequency channels and timings can be
established.
[0041] In the infrastructure mode of IEEE 802.11, the operation of
an access point (AP) is started first, and a beacon is periodically
transmitted at a frequency (referred to as F1) that is set in
advance. Here, the beacon is notification information including an
ESS-ID, which is an identifier of a network, a time stamp, which is
time information in the network, a list of supported wireless
transmission rates, or the like. A station (STA) finds the access
point (AP), which is a communication counterpart, by receiving the
beacon transmitted from the access point. At this time, the
frequency of the station (STA) may be set by a user to be the same
as the frequency F1 of the access point (AP). Alternatively, the
frequency of the station (STA) may be set such that the station
continues reception while switching the frequency channels defined
by IEEE 802.11 one by one until the station detects the beacon.
[0042] FIG. 1 is a sequence diagram showing a flow of a sequence
until communication is started between an access point and a
station, in the infrastructure mode of IEEE 802.11. First, the
power of an access point is turned on in step S10, and the access
point starts transmission of beacon at the frequency F1 in the next
step S12. Additionally, the access point can autonomously find the
frequency set by a user or a frequency at which an access point is
vacant. After the power is turned on in step S20, the station
starts waiting for a beacon in step S22. The station keeps waiting
while switching frequencies.
[0043] In step S24, the frequency at which the station waits for a
beacon is set to Fl. Accordingly, a beacon (frequency F1)
transmitted from the access point is received at the station, and
in step S26, the station perceives the existence of the access
point.
[0044] Then, authentication and association are performed between
the access point and the station, and connection is completed in
step S28. After the connection is completed, a beacon is
transmitted from the access point to the station, and data
communication between the access point and the station is
started.
[0045] (2) Communication Method where Access Point is Not
Determined in Advance and Its Demerit
[0046] On the other hand, a method can be assumed according to
which two terminals are connected by direct connection in a simple
manner by using the mechanism of IEEE 802.11 wireless LAN without
the user consciously distinguishing between an access point and a
station. According to this method, the terminals are equal to each
other without the distinction of access point and station, and at
the time of communication, both start searching for each other at
the same time. Negotiation is performed after each other is found,
and one plays the role of a simple access point, and the other
plays the role of a station. Accordingly, this method enables to
realize a simple infrastructure mode without distinguishing between
an access point and a station.
[0047] According to the method described above, two terminals have
to find each other simultaneously without which terminal is to play
the role of starting continuous transmission of beacons (the role
of the access point) being determined. At this time, the two
terminals start operation while still not knowing the frequency of
a counterpart and not even knowing if a counterpart exists at all.
Accordingly, the two terminals have to transmit notification
information while switching the frequencies, and at the same time,
to wait in anticipation of reception of notification information of
a counterpart.
[0048] FIG. 2 is a sequence diagram showing an example of
transmitting notification information by using a beacon in
communication by direct connection using the mechanism of IEEE
802.11 wireless LAN. First, the power of a station 1 (STA1) is
turned on in step S30. In the next step S32, the station 1
transmits a beacon at the frequency F1, and after transmitting the
beacon, waits, in step S34, for a response from other station at
the frequency F1.
[0049] On the other hand, at a station 2 (STA2), power is turned on
in step S40. In the next step S42, the station 2 transmits a beacon
at the frequency F1, and after transmitting the beacon, waits, in
step S44, for a response from other station at the frequency
F1.
[0050] In the example of FIG. 2, the frequency F1 of the beacon
transmitted by the station 1 and the frequency F1 at which the
station 2 is waiting match. Accordingly, the station 2 can receive
the beacon transmitted by the station 1. When receiving the beacon
transmitted by the station 1, the station 2 perceives the existence
of the station 1 in step S46. Then, negotiation for determining
which is to play the role of an access point is performed between
the station 1 and the station 2. As a result of the negotiation, it
is determined in step S48 that the station 1 will play the role of
an access point, and the connection is completed. In this case, the
station 2 will play the role of a station (station (STA) shown in
FIG. 1) in the infrastructure mode. After the connection is
completed, a beacon is transmitted from the access point to the
station, and data communication is performed between the access
point and the station.
[0051] As described above, according to communication by direct
connection using the mechanism of IEEE 802.11 wireless LAN, a
simple infrastructure mode can be realized by negotiation at the
time of connection, without determining in advance which device is
to play the role of an access point or a station.
[0052] However, according to the communication by direct connection
described above, notification information (beacons) are
continuously transmitted with the frequencies continuously
changing. Thus, if the frequency change cycles of the station 1 and
the station 2 match, the frequencies are changed while maintaining
the state where the frequencies are shifted from each other, and
the terminals may not find each other. FIG. 3 is a sequence diagram
showing a case where frequency change cycles of the station 1 and
the station 2 match.
[0053] First, when the power of the station 1 (STA1) is turned on
in step S50, the station 1 sets a communication frequency to F1 in
the next step S52. In the next step S54, the station 1 transmits a
beacon at the frequency F1, and after transmitting the beacon,
waits, in step S56, for a response from other station at the
frequency F1.
[0054] On the other hand, when the power of the station 2 (STA2) is
turned on in step S60, the station 2 sets a communication frequency
to F2 in the next step S62. In the next step S64, the station 2
transmits a beacon at the frequency F2, and after transmitting the
beacon, waits, in step S66, for a response from other station at
the frequency F2.
[0055] The station 1 switches the frequency to F2 in step S58, and
transmits a beacon and waits as in steps S54 to S56. Subsequently,
the station 1 periodically switches the frequency in the order of
F3.fwdarw.F1.fwdarw.F2.fwdarw.F3, and performs the same
processes.
[0056] The station 2 also switches the frequency to F3 in step S68,
and transmits a beacon and waits as in steps S64 to S66.
Subsequently, the station 2 periodically switches the frequency in
the order of F1.fwdarw.F2.fwdarw.F3.fwdarw.F1, and performs the
same processes.
[0057] In FIG. 3, when the station 1 transmits a beacon at the
frequency F1 (step S54) and is waiting at the frequency F1 (S56),
the station 2 transmits a beacon at the frequency F2 (step S64) and
is waiting at the frequency F2 (step S66). Therefore, neither the
station 1 nor the station 2 can perceive the other because their
respective frequencies are different. Also, in FIG. 3, the
frequency switching cycle is the same for the station 1 and the
station 2. Thus, even if each of the stations 1 and 2 switches the
frequency after step S58 or S68, the frequency at which the station
1 performs transmission and the frequency at which the station 2 is
waiting will not match. Also, the frequency at which the station 2
performs transmission and the frequency at which the station 1 is
waiting will not match. Therefore, both station 1 and station 2
will not perceive each other.
[0058] (3) Configuration of Wireless Communication Device
[0059] FIG. 4 is a block diagram showing an example of the
configuration of a wireless communication device 100 according to
each embodiment of the present invention. The wireless
communication device 100 is configured to be able to communicate
with other wireless communication device by a wireless
communication network such as IEEE 802.11a, IEEE 802.11b and IEEE
802.11n, which are wireless LAN standards. As shown in FIG. 1, each
wireless communication device 100 includes a data processing unit
102, a transmission processing unit 104, a wireless interface unit
106, a control unit 108, a memory 110, and an antenna 112.
[0060] At the time of transmission, the data processing unit 102
creates various data frames and data packets in response to a
request from an upper layer, for example, and supplies the same to
the transmission processing unit 104. The transmission processing
unit 104 performs, at the time of transmission, processing such as
adding to a packet generated at the data processing unit 102
various data heads or an error detection code such as a frame check
sequence (FCS), and provides the data which has been processed to
the wireless interface unit 106. The wireless interface unit 106
generates, from the data received from the transmission processing
unit 104, a modulation signal in a frequency band of a carrier, and
makes the same transmitted from the antenna 112 as a radio
signal.
[0061] Furthermore, at the time of performing a reception
operation, the wireless interface unit 106 decodes the various data
frames by down-converting the radio signal received by the antenna
112 and changing the same to a bit sequence. That is, the wireless
interface unit 106 can function, in cooperation with the antenna
112, as a transmitting unit and a receiving unit. The transmission
processing unit 104 analyzes the headers added to the various data
frames supplied from the wireless interface unit 106 and checks,
based on the error detection code, that each data frame includes no
error, and then, supplies the various data frames to the data
processing unit 102. The data processing unit 102 processes and
analyzes the various data frames and data packets supplied from the
transmission processing unit 104.
[0062] The control unit 108 is a block for controlling the
respective operations of the data processing unit 102, the
transmission processing unit 104, and the wireless interface unit
106. The control unit 108 performs operations such as determination
of a transmission/reception frequency, creation of a control
message (notification information such as a beacon, a beacon
acknowledgement, a probe request and a probe response), issuance of
a transmission command for the control message, and interpretation
of the control message. Also, the control unit 108 controls various
operations of the wireless communication device 100, such as
reception operation and transmission operation.
[0063] As shown in FIG. 4, the control unit 108 includes, as main
structural elements, a notification-information
creation/transmission-instruction unit 108a, a
reception/interpretation processing unit 108b, a frequency
switching unit 108c, and a random period setting unit 108d. The
notification-information creation/transmission-instruction unit
108a creates the control message, or issues a transmission command
for the control message. The reception/interpretation processing
unit 108b performs a reception process or an interpretation process
for the control message transmitted from the communication
counterpart. The frequency switching unit 108c performs an
operation of switching transmission frequencies or of switching
waiting frequencies. The random period setting unit 108d performs
an operation of setting a transmission cycle or a waiting cycle to
a random period.
[0064] The memory 110 plays the role of a work area for the data
processing by the control unit 108, and has a function of a storage
medium for holding various types of data. Various storage media,
for example, a volatile memory such as a DRAM, a non-volatile
memory such as an EEPROM, a hard disk and an optical disk, may be
used as the memory 110. Additionally, each block shown in FIG. 4
can be configured from hardware (circuit). Furthermore, each block
can be configured from a processor (CPU) and software (program) for
making the processor function. In this case, the program can be
stored in the storage medium included in the wireless communication
device 100, such as the memory 110.
[0065] (4) Flow of Processes according to First Embodiment
[0066] The present embodiment makes the frequency change cycle
inconstant (random) in view of the issue described with FIG. 3.
FIG. 5 is a schematic diagram showing a flow of a sequence
according to the present embodiment. As with FIG. 3, two stations
(STA1 and STA2) are to look for a communication counterpart. Both
stations 1 and 2 are assumed to have a function conforming to IEEE
802.11. Also, as with FIG. 3, usable frequencies are F1, F2 and F3
for both stations 1 and 2.
[0067] There are two kinds of messages to be transmitted by each of
the station 1 and the station 2, namely, a beacon and a beacon
acknowledgement which is transmitted at the time of receiving a
beacon. Also, there are four states in relation to the states of
each of the station 1 and the station 2, namely, beacon
transmission, waiting, frequency changing, and beacon response
transmission.
[0068] In FIG. 5, the station 1 is to transmit a beacon at the
frequency F1 during the beacon transmission cycle. Also, the
station 2 is to transmit a beacon at the frequency F2. With both
station 1 and station 2, the transmission of a beacon is to be
alternately performed every 2 cycles of the frequency switching
cycles and waiting is to be performed every cycle.
[0069] First, when the power of the station 1 (STA1) is turned on
in step S100, the station 1 sets a communication frequency to F1 in
the next step S102. In the next step S104, the station 1 transmits
a beacon at the frequency F1, and after transmitting the beacon,
waits, in step S106, for a response from other station at the
frequency F1.
[0070] On the other hand, at the station 2 (STA2), when the power
is turned on in step S200, a communication frequency is set to F2
in the next step S202. In the next step S204, the station 2
transmits a beacon at the frequency F2, and after transmitting the
beacon, waits, in step S206, for a response from other station at
the frequency F2.
[0071] Then, in step S208, the station 2 sets the frequency to F3.
Since the transmission of a beacon is performed every 2 cycles of
the frequency switching cycles, the station 2 waits without
transmitting a beacon at the frequency F3 (step S210). Then, the
frequency is switched to F2 in step S212, and a beacon is
transmitted at the frequency F2 in the next step S214.
[0072] The station 1 changes the frequency to F2 in step S108.
Since, also at the station 1, the transmission of a beacon is
performed every 2 cycles of the frequency switching cycles, the
station 1 waits without transmitting a beacon at the frequency F2
(S110). Thus, the transmission timing of a beacon (frequency F2) by
the station 2 in step S214 is during the time the station has
started to wait (frequency F2) in step S110 and is still waiting at
the frequency F2. This is because, in this case, steps S212 and
S214 of the station 2 occurred before the timing of the station 1
changing the frequency after step S 108, because the cycle of the
station 1 for changing the frequency after step S108 was set to be
random. Therefore, the station 1 receives the beacon transmitted
from the station 2 at the frequency F2, perceives the existence of
the station 2 in step S112, and transmits a beacon response in the
next step S114.
[0073] The station 2 receives the beacon response transmitted from
the station 1 and perceives the existence of the station 1 in step
S216. Then, negotiation is performed between the station 1 and the
station 2 to determine which is to play the role of an access
point. Here, it is assumed that, as a result of the negotiation,
the station 1 is determined to play the role of an access point in
the infrastructure mode (step S218), and the connection is
completed. In this case, the station 2 will play the role of a
station in the infrastructure mode. After the connection is
completed, data communication is performed between the station 1
and the station 2.
[0074] In the sequence of the present embodiment shown in FIG. 5,
the cycle for transmitting beacons, the cycle for waiting, or the
cycle for changing the frequencies is set to a random period for
each of the stations 1 and 2. Referring to the station 2 as an
example, a time T1 from a timing of starting the waiting at the
frequency F3 (step S210) to a timing of changing to the frequency
F2 (step S212) can be set as the random period. Also, a time T2
from a timing of setting to the frequency F3 (step S208) to a
timing of changing to the next frequency F2 (step S212) can be set
as the random period.
[0075] Also, in case of the cycle for waiting after the
transmission of a beacon, a time T3 from a timing of transmitting a
beacon at the frequency F2 and of starting to wait (step S206) to a
timing of changing to the next frequency F3 (step S208) can be set
as the random period.
[0076] Also, a time T4 from setting the transmission frequency for
a beacon to F2 (step S202) to a timing of changing to the next
frequency F3 (step S208) can be set as the random period.
[0077] Also, a portion equivalent to 2 cycles of the frequency
switching cycles may be set as the random period. For example, a
time T5 from setting the transmission frequency for a beacon to F2
(step S202) to a next timing of setting the transmission frequency
for a beacon to F2 (step S212) may be set as the random period.
[0078] In this manner, by setting the cycle for transmitting
beacons, the cycle for waiting, or the cycle for changing the
frequencies at a random period, frequencies can be prevented from
being switched at the same cycles at both station 1 and station 2.
Accordingly, a state as described with FIG. 3 in which the
terminals will not find each other can be reliably prevented.
[0079] The random period may be period generated by a random number
generator, for example. By ending a waiting state at a certain
frequency at a timing of elapse of a random period and switching to
the next frequency, a situation as described in FIG. 3 where
devices will not find each other can be reliably prevented.
[0080] Additionally, in FIG. 5, it is assumed that the transmission
of a beacon is performed every 2 cycles of the frequency switching
cycles at each of the stations 1 and 2. However, as with FIG. 3,
the transmission of a beacon and waiting can be performed every
cycle. In this case, the transmission frequency for a beacon can
also be changed every cycle as with FIG. 3.
[0081] Additionally, although beacons are transmitted at a constant
frequency at all times in FIG. 5, the beacons may be transmitted at
periodically different frequencies (for example,
F1.fwdarw.F2.fwdarw.F3.fwdarw.F1, . . . ).
2. Second Embodiment
[0082] (1) Flow of Processes according to Second Embodiment
[0083] Next, the second embodiment of the present invention will be
described. The configuration of a wireless communication device 100
according to the second embodiment is the same as that of the first
embodiment described with FIG. 4. The waiting time for receiving a
beacon was made random in the first embodiment. However, in the
second embodiment, a cycle for transmission or a cycle for waiting
is set to a random period in case of receiving a probe response as
a response to a probe request. The probe request here is
notification information including an identifier of a network,
supported communication rate information, identification
information of each station, or the like.
[0084] In the second embodiment, there are two kinds of messages to
be transmitted by each of the station 1 and the station 2, namely,
a probe request and a probe response. Also, there are four states
in relation to the states of each of the station 1 and the station
2, namely, probe request transmission, waiting, frequency changing,
and probe response transmission.
[0085] FIG. 6 is a schematic diagram showing the flow of processes.
It is assumed that, for both the station 1 and the station 2, the
transmission of a probe request is performed every 2 cycles of the
frequency switching cycles and waiting is performed every
cycle.
[0086] First, when the power of a station 1 (STA1) is turned on in
step S300, the station 1 sets a communication frequency to F1 in
the next step 5302. In the next step S304, the station 1 transmits
a probe request at the frequency F1. Then, after transmitting the
probe request, the station 1 waits, in step S306, for the reception
of a probe response to the probe request that has been
transmitted.
[0087] On the other hand, when the power of a station 2 (STA2) is
turned on in step S400, a communication frequency is set to F3 in
the next step S402. The station 2 transmits a probe request at a
frequency F2 in the next step S404. Then, after transmitting the
probe request, the station 2 waits, in step S406, for a probe
response to the probe request that has been transmitted.
[0088] Then, in step S408, the station 2 sets the frequency to F1,
and waits for a probe request at the frequency F1 in step S410.
Then, in step S412, the frequency is switched to F3, and a probe
request is transmitted at the frequency F3 in the next step
S414.
[0089] The station 1 changes the frequency to F3 in step S308,
starts waiting for a probe request at the frequency F3 in the next
step S310, and will keep waiting. Then, the transmission timing of
a probe request (frequency F3) by the station 2 in step S414
matches the timing of the station 1 waiting (frequency F3), after
step S310, for a probe request. This is because, in this case,
steps S412 and S414 of the station 2 occurred before the timing of
the station 1 changing the frequency after step S308, because the
cycle of the station 1 for changing the frequency after step S308
was set to be random. Therefore, the station 1 receives the probe
request transmitted from the station 2 at the frequency F3,
perceives the existence of the station 2 in step S312, and
transmits a probe response in the next step S314.
[0090] The station 2 receives the probe response transmitted from
the station 1 and perceives the existence of the station 1 in step
S416. Then, negotiation is performed between the station 1 and the
station 2 to determine which is to play the role of an access
point. Here, it is assumed that, as a result of the negotiation,
the station 1 is determined to play the role of an access point in
the infrastructure mode (step S418), and the connection is
completed. In this case, the station 2 will play the role of a
station in the infrastructure mode. After the connection is
completed, data communication is performed between the station 1
and the station 2.
[0091] Also in the sequence of the embodiment shown in FIG. 6, the
waiting time is set to a random period for both station 1 and
station 2. Referring to the station 2 as an example, any of T6 to
T11 shown in FIG. 6 or some of T6 to T11 can be made to be the
random period.
[0092] In the present embodiment, in case of transmitting a probe
request, it is assumed for both station 1 and station 2 that the
probe request is transmitted with usable frequencies periodically
switched in turn. In FIG. 6, the station 1 switches the frequency
in the order such as F1.fwdarw.F2.fwdarw.F3.fwdarw.F1 . . . , and
the station 2 switches the frequency in the order such as
F2.fwdarw.F3.fwdarw.F1.fwdarw.F2 . . . .
[0093] On the other hand, since the counterpart is transmitting
probe requests while switching the frequencies, a probe request is
to be waited for at a constant frequency. In the example of FIG. 6,
the station 1 waits for a probe request at the frequency F3, and
the station 2 waits for a probe request at the frequency F1.
However, the waiting frequency may be periodically differing
frequencies, and may be switched in the order of
F1.fwdarw.F2.fwdarw.F3.fwdarw.F1, . . . , for example.
[0094] As described above, according to the present embodiment, by
making random the time during which a waiting state is continued,
the frequencies of the devices are not set to be different at all
times, and a situation where the devices will not find each other
can be prevented.
[0095] It should be understood by those skilled in the art that
various modifications, combinations, sub-combinations and
alterations may occur depending on design requirements and other
factors insofar as they are within the scope of the appended claims
or the equivalents thereof.
[0096] The present application contains subject matter related to
that disclosed in Japanese Priority Patent Application JP
2009-94369 filed in the Japan Patent Office on Apr. 8, 2009, the
entire content of which is hereby incorporated by reference.
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