DESCRIPTION
[Title of Invention]
CONTENT DELIVERY METHOD
5 Technical Field
[0001] The present invention relates to a content delivery method
and a communication terminal, which deliver a content.
Background Art
[0002] A scheme which is delivering data and contents mutually
10 among communication terminals (nodes) connected with each other
through wireless links, and thereby causing the communication terminals
to share the data and contents with each other, is generally utilized by
employing various application software. As its typical example,
Epidemic Routing disclosed in Non Patent Literature 1 is mentioned.
15 Epidemic Routing is a scheme of causing communication terminals to
dispersively share the same content with each other, in an unstable
wireless network such as a DTN (Delay/Disruption Tolerant Network).
[0003] Fig. 1 is a diagram showing a process sequence in Epidemic
Routing.
20 [0004] In Fig. 1, shown is an example of causing two
communication terminals, corresponding to a terminal 200-1 and a terminal
200-2 in this case, to share a content with each other, by means of
Epidemic Routing. Each of the terminals 200-1 and 200-2 periodically
transmits a message referred to as a summary vector message, which
25 includes information on the terminal (its node ID, IP (Internet Protocol)
address or the like) and a list of contents held by the terminal. Further, by
receiving a summary vector message transmitted from a terminal existing
in its vicinity, each of the terminal 200-1 and 200-2 can become aware of
information on a terminal neighboring itself and of a content not in its
3
possession.
[0005] Here, considered here is a case where the terminal 200-2
receives a summary vector message transmitted by the terminal 200-1, as
in the example shown in Fig. 1. Receiving a summary vector message
5 transmitted from the terminal 200-1 in the process of a step 21, the
terminal 200-2 becomes aware of the terminal 200-1 neighboring itself and
refers to a list of contents held by the terminal 200-1, on the basis of the
content of the received summary vector message.
[0006] Then, if detecting any content not in its possession (it does
10 not hold), among the contents held by the terminal 200-1, the terminal
200-2 transmits to the terminal 200-1 a request message (content request)
for acquiring the content, in the process of a step 22.
[0007] When receiving the content request transmitted from the
terminal 200-2, the terminal 200-1 delivers the requested content to the
15 terminal 200-2, in the process of a step 23.
[0008] As a result of the above-described way, where each of the
terminals 200-1 and 200-2 periodically transmits a summary vector
message and, if detecting any content not in its possession, requests and
acquires the content, in Epidemic Routing, it becomes possible for the
20 terminals to dispersively share the same content with each other.
[0009] Besides, a wireless LAN (Local Area Network) is widely
used as a scheme of constructing a wireless network. IEEE802.il is
generally used as a wireless LAN standard. Also, widely used is the name
Wi-Fi, which indicates that the interconnectivity between devices is
25 certified in conformity to the IEEE802.il standard.
[0010] In a wireless network of the case of using Epidemic Routing
described above, assumed is an environment, such as that in a DTN, where
disconnection of a link in the wireless network frequently occurs owing to
the influence of terminal movement and of an obstacle.
30 [001 1] In such an environment, it is desirable to use, as a setting of
4
the wireless LAN, not an infrastructure mode but an ad hoc mode. The
reasons to be mentioned are the following advantages of the ad hoc mode:
(1) capability of constructing a peer to peer type link even with no access
point existing, (2) no necessity of association establishment and rapid
5 session establishment, and the like.
[0012] The advantageous functions (1) and (2) are desired for
constructing a peer to peer type system, and for quickly exchanging control
messages (a summary vector or a content request) even within a short
link-up time, respectively.
10 Citation List
Non Patent Literature
[001 3J Non Patent Literature 1: A. Vahdat and D. Becker,
"Epidemic routing for partially-connected ad hoc networks", Duke Tech.
Rep. CS-2000-06, July 2000.
15 Technical Problem
[0014] As has been described above, by using Epidemic Routing, it
becomes possible to cause terminals to dispersively share the same content
with each other even in an unstable wireless network such as a DTN.
Further, when Epidemic Routing is performed using a wireless LAN, it is
20 desirable to use an ad hoc mode for the setting of the wireless LAN.
[0015] However, while the use of an ad hoc mode of a wireless LAN
has the advantages described above, it has problems described below.
[0016] A first problem is its vulnerability in security performance.
In general, security setting applicable in an ad hoc mode is up to WEP, and
25 it is impossible to use WPA (Wi-Fi Protected Access) or WPA2, which are
considered to be comparatively robust and generally applicable in an
infrastructure mode.
[0017] A second problem is its low communication speed. In
general, an ad hoc mode can deal with a communication speed only up to
30 54 Mbps used in IEEE802.11a and IEEE802.11g. In an ad hoc mode, it is
5
impossible to use a communication standard supporting a higher
communication speed, such as IEEE802.11n, which is generally applicable
in an infrastructure mode.
[0018] A third problem is its low utilization efficiency of wireless
5 resources. In an ad hoc mode, since terminals transmit management frames
to each other, such as beacon frames periodically transmitted, and
accordingly, the management frames use a certain amount of wireless
resources. Therefore, when the number of terminals is particularly large,
an overhead of the management frames or the like becomes large. In
10 contrast, in an infrastructure mode, transmission and reception of
management frames are performed between an access point and a terminal,
and accordingly, an overhead of them is relatively small.
[0019] Thus, while an ad hoc mode is a wireless LAN setting
suitable for Epidemic Routing, it also has some problems.
15 [0020] The objective of the present invention is to provide a
content delivery method and a communication terminal, both of which can
solve the problems described above.
Solution to Problem
[0021] A content delivery method of the present invention is a
20 content delivery method for performing content delivery among a plurality
of communication terminals via a wireless LAN, and the method
comprises:
a step wherein the plurality of communication terminals exchange
with each other control messages to be transmitted and received until a
25 request for the content delivery is made, in an ad hoc mode; and
a step wherein a communication terminal having received the
request for content delivery, among the plurality of communication
terminals, delivers the requested content to a communication terminal
having requested the content delivery, in an infrastructure mode.
30 [0022] A communication terminal of the present invention
6
comprises:
a wireless LAN interface unit for performing a wireless LAN
communication with other communication terminals;
a control message transmission/reception unit for setting the
5 wireless LAN interface unit at an ad hoc mode and exchanging with the
other communication terminals, via the wireless LAN interface unit,
control messages to be transmitted and received until a request for content
delivery is made; and
a content transmission/reception unit for, when having received the
10 request for content delivery, setting the wireless LAN interface unit at an
infrastructure mode and delivering the requested content via the wireless
LAN interface unit.
Advantageous Effects of Invention
[0023] As has been described above, according to the present
15 invention, efficient content delivery can be realized.
Brief Description of Drawings
[0024]
[Fig. 1] Fig.l is a diagram showing a process sequence in Epidemic
Routing.
20 [Fig- 2] Fig.2 is a diagram showing an exemplary embodiment of a
communication terminal of the present invention.
[Fig. 3] Fig.3 is a diagram showing an example of a configuration
of a wireless network for when an ad hoc mode is set for a wireless LAN
interface unit shown in Fig. 2.
25 [Fig. 4] Fig.4 is a diagram showing an example of a configuration
of a wireless network when an infrastructure mode is set for the wireless
LAN interface unit shown in Fig. 2.
[Fig. 5] Fig.5 is a flow chart for explaining an example of a process,
among those comprised in a content delivery method relating to the
30 embodiment shown in Fig. 2, when the communication terminal
7
corresponds to the content reception side.
[Fig. 6] Fig.6 is a flow chart for explaining an example of a process,
among those comprised in the content delivery method relating to the
embodiment shown in Fig. 2, when the communication terminal
5 corresponds to the content transmission side.
Description of Embodiments
[0025] Hereinafter, an exemplary embodiment of the present
invention will be described with reference to drawings.
[0026] Fig. 2 is a diagram showing an exemplary embodiment of a
10 communication terminal of the present invention.
[0027] As shown in Fig. 2, the communication terminal 100 in the
present exemplary embodiment is provided with application software 111,
a control message transmission/reception unit 112, a content
transmission/reception unit 113, a TCP/IP communication unit 1 14, a
15 wireless LAN interface setting unit 115, a wireless LAN interface unit 116
and a wireless LAN adapter 117. Here, the wireless LAN adapter 117 may
be provided as a part of the wireless LAN interface unit 116, as shown in
Fig. 2, or as a component separated from the wireless LAN interface unit
116. The communication terminal 100 shown in Fig. 2 is a communication
20 device connected to a communication network via a wireless link, and it
may be a communication terminal, such as a PC (Personal Computer) and a
smart phone, which itself executes application software, or may be a
communication device, such as a wireless LAN bridge, which relays
communication performed by a communication terminal under its control,
25 which executes application software. In the following descriptions, the
case of the communication terminal 100 being a communication terminal
such as a PC and a smart phone will be taken as an example.
[0028] The application software 111 is application software for
performing content delivery. An application software which delivers a
30 content, such as location information, sensor information or the like on the
8
communication terminal 100, to be shared, to other communication
terminals, by means of Epidemic Routing, can be exemplified as the
application software 111. Further, before content delivery, the application
software 111 performs a procedure of exchanging control messages with
5 neighboring communication terminals via the control message
transmission/reception unit 112, and after ending of the procedure, it
actually performs content delivery to or from the neighboring
communication terminals via the content transmission/reception unit 113.
Here, when Epidemic Routing is used, the control messages include a
10 summary vector message and a content request message before content
delivery.
[0029] The control message transmission/reception unit 112 is
provided with a function to transmit and receive control messages to and
from neighboring communication terminals, in a procedure prior to
15 delivery of a content on which the application software 111 performs a
process for its transmission or reception. Besides, the control message
transmission/reception unit 112 is also provided with a function to set, via
the wireless LAN interface setting unit 115, the wireless LAN interface
unit 1 16 such that an ad hoc mode is used in transmission and reception of
20 the control messages.
[0030] The content transmission/reception unit 1 13 is provided with
a function to transmit or receive a content, on which the application
software 11 1 performs a process for its transmission or reception, to or
from neighboring communication terminals. Also, the content
25 transmission/reception unit 1 13 is provided with a function to set, via the
wireless LAN interface setting unit 115, the wireless LAN interface unit
116 such that an infrastructure mode is used in transmission and reception
of contents.
[0031] The TCP/IP communication unit 114 has a standard
30 communication function installed in an OS (Operation System). In the
9
present exemplary embodiment, the TCP/IP communication unit 114
provides transmission and reception services of messages and contents for
the control message transmission/reception unit 112 and the content
transmission/reception unit 113. The messages and contents are transmitted
5 and received using a protocol of TCP (Transmission Control Protocol) or
UDP (User Datagram Protocol).
[0032] The wireless TAN interface setting unit 115 is provided with
a function to change (switch) the setting of the wireless LAN interface unit
116 in response to a request from the control message
10 transmission/reception unit 112 or the content transmission/reception
unit 113. Specifically, when having received a request from the control
message transmission/reception unit 112, the wireless LAN interface
setting unit 115 sets the wireless LAN interface unit 116 such that an ad
hoc mode is used in transmission and reception of data (control messages).
15 On the other hand, when having received a request from the content
transmission/reception unit 113, the wireless LAN interface setting unit
115 sets the wireless LAN interface unit 116 such that an infrastructure
mode is used in transmission and reception of data (contents).
[0033] The wireless LAN interface unit 116 is an interface with a
20 wireless LAN, which is connected with the wireless LAN via the wireless
LAN adapter 117. The wireless LAN interface unit 116 has two operation
modes, which are an ad hoc mode and an infrastructure mode.
[0034] Fig. 3 is a diagram showing an example of a configuration of
a wireless network when an ad hoc mode is set for the wireless LAN
25 interface unit 116 shown in Fig. 2.
[0035] In Fig. 3, there exist communication terminals 100-1 to
100-3. There, dashed circles having respective ones of the communication
terminals 100-1 to 100-3 located at their centers express areas in which the
respective communication terminals 100-1 to 100-3 can be connected with
30 the other communication terminals via wireless links, in the case an ad hoc
10
mode is set for the wireless LAN interface unit 116 of each of the
communication terminals 100-1 to 100-3. Here, it is considered that the
areas do not actually become true circles, but for convenience of
explanation, the areas are assumed to be circular in Fig. 3. As shown in Fig.
5 3, each of the communication terminals 100-1 to 100-3 is connected, via
wireless links, with all communication terminals existing within the
corresponding dashed circle, and the topology is thereby constructed.
[0036] Fig. 4 is a diagram showing an example of a configuration of
a wireless network when an infrastructure mode is set for the wireless LAN
10 interface unit 116 shown in Fig. 2.
[0037] In the configuration shown in Fig. 4, there exist
communication terminals 100-1 to 100-3. Then, in Fig. 4, shown is a
configuration for a case where an infrastructure mode is set for the
wireless LAN interface units 116 of each of the communication terminals
15 100-1 to 100-3, and the communication terminal 100-1 corresponds to the
access point, and the communication terminals 100-2 and 100-3 to the
clients. As shown in Fig. 4, all communication terminals existing within a
dashed circle having the communication terminal 100-1 located at its
center (in the case of Fig. 4, the communication terminals 100-2 and 100-3)
20 are connected with the communication terminal 100-1 corresponding to the
access point via wireless links, and the topology is thereby constructed.
[0038] As an example of a method of constructing a dynamic
wireless network in such a manner of setting the communication terminal
100-1 to be the access point as that shown in Fig. 4, the Wi-Fi direct
25 standard defined by the Wi-Fi alliance is known. In this manner, when a
wireless network of an infrastructure mode is constituted by a plurality of
communication terminals to participate in content delivery, by dynamically
setting any one of the communication terminal to be the access point, as in
the above-described way, it becomes possible to cut out the need of
30 installing a dedicated access point device in advance.
11
[0039] Besides, in that case, it is further desirable to set a
communication terminal which transmits (delivers) a content to be the
access point and communication terminals which receive the content to be
the clients. It is because a star-shaped wireless topology centered at the
5 access point is thereby constructed, as shown in Fig. 4, and as a result, it
becomes possible to increase the utilization efficiency of wireless
resources during the content delivery.
[0040] The wireless LAN adapter 117 includes a physical device.
which provides the wireless LAN interface unit 1 16 and its function.
10 Further, the wireless LAN adapter 1 17 is not limited to provide, in the
wireless LAN interface unit 116, only one wireless LAN interface, but
there may be also a case where it provides a virtual plurality of wireless
LAN interfaces on a single physical wireless LAN adapter. As an example
of a technology of providing such a virtual plurality of wireless LAN
15 interfaces, the Virtual Wi-Fi is known. When the wireless LAN adapter 117
can provide a virtual plurality of wireless LAN interfaces, as in the Virtual
Wi-Fi, the wireless LAN interface unit 1 16 has at least two wireless LAN
interfaces, where an ad hoc mode is set for one of the wireless LAN
interfaces (a first interface), and an infrastructure mode for the other one
20 (a second interface). By thus setting the two wireless LAN interfaces, it
also becomes possible to use them properly such that, with no need of
dynamically switching between the wireless LAN operation modes, the
wireless LAN interface set at the ad hoc mode is used for transmission and
reception of control messages, and the wireless LAN interface set at the
25 infrastructure mode for transmission and reception of contents.
[0041] Besides, in the above description of the configuration of the
communication terminal 100, the four components, that is, the application
software 111, the control message transmission/reception unit 112, the
content transmission/reception unit 113 and the wireless LAN interface
30 setting unit 115, have been described to be separate functions, but they
12
may be actually installed together into a single application program.
[0042] Hereinafter, a content delivery method relating to the
embodiment shown in Fig. 2 will be described. Here, a description will be
given of operation of content delivery performed by the communication
5 terminal 100 using Epidemic Routing. Firstly, a case where the
communication terminal 100 receives a content is described.
[0043] Fig. 5 is a flow chart for explaining an example of a process
performed when the communication terminal 100 receives a content,
among processes included in the content delivery method relating to the
10 embodiment shown in Fig. 2 .
[0044] In the communication terminal 100, in order for the
application software 111 to perform content sharing by means of Epidemic
Routing, it is necessary first to exchange control messages. Accordingly,
for the purpose of exchanging control messages, the control message
15 transmission/reception unit 112 sets the operation mode of the wireless
LAN interface unit 11 6 at an ad hoc mode, via the wireless LAN interface
setting unit 115, in the process of a step 1.
[0045] Next, in the process of a step 2, the control message
transmission/reception unit 112 starts exchanging summary vector
20 messages with other communication terminals. The control message
transmission/reception unit 112 periodically transmits a summary vector
message. The summary vector message includes information on the own
communication terminal 100 (its node ID, IP address or the like) and a list
of contents in the possession of the communication terminal 100.
25 [0046] Receiving a summary vector message from any one of the
other communication terminals in the process of a step 3, subsequently in
the process of a step 4, the control message transmission/reception unit
112 checks the content list included in the received summary vector
message, and determines whether or not any content not in the possession
30 of (not held by) the own communication terminal 100 is included in the
13
content list.
[0047] If no content not in the possession of the own
communication terminal 100 is included in the content list, the process of
the step 2 is performed again, and thereby, the control message
5 transmission/reception unit 112 continues to exchange summary vector
messages.
[0048] On the other hand, if any content not in the possession of the
own communication terminal 100 is included in the content list, the control
message transmission/reception unit 112 performs, in the process of a step
10 5, a content request for the content not in the possession. Specifically, the
control message transmission/reception unit 112 transmits a content
request for the content not in the possession to a communication terminal
having transmitted the corresponding summary vector message, via the
TCP/IP communication unit 114 and the wireless LAN interface unit 116.
15 [0049] Subsequently, in the process of a step 6, the control message
transmission/reception unit 112 determines whether or not a response
message expressing permission for delivery of the requested content has
been sent back, in response to the content request message it transmitted.
The determination may be performed in a manner to set a certain time
20 period and then determine whether or not a response message has been sent
back within the set time period since the transmission of the content
request message.
[0050] If no response message has been sent back, the process of
the step 2 is performed again, and thereby, the control message
25 transmission/reception unit 112 continues to exchange summary vector
messages.
[0051] On the other hand, if any response message has been sent
back, the process is handed over from the control message
transmission/reception unit 112 to the content transmission/reception unit
30 1 1 3 by the application software 111. Accordingly, in the process of a step
14
7, the content transmission/reception unit 113 sets the operation mode of
the wireless LAN interface unit 11 6 at an infrastructure mode. In the
process of a step 8, the content transmission/reception unit 113 actually
performs content transfer and thereby receives the requested content.
5 [0052] When reception of the content has been completed in the
process of the step 8, subsequently in the process of the step 1, the control
message transmission/reception unit 112 sets the operation mode of the
wireless LAN interface unit 11 6 at the ad hoc mode, and thereby continues
to exchange summary vector messages.
10 [0053] Next, a case where the communication terminal 100
transmits a content will be described below.
[0054] Fig. 6 is a flow chart for explaining an example of a process
performed when the communication terminal 100 transmits a content,
among processes included in the content delivery method relating to the
15 embodiment shown in Fig. 2.
[0055] First, the same processes as those in the steps 1 and 2 are
performed, respectively, in a step 1 1 and in a step 12.
[0056] During exchanging summary vector messages, if receiving a
content request message transmitted from any one of the other
20 communication terminals in the process of a step 13, then in the process of
a step 14, the control message transmission/reception unit 112 inquires of
the application software 11 1 about whether the content requested through
the content request message is deliverable or not. While, all contents
usually should be deliverable, the requested content becomes undeliverable
25 in such cases, for example, where the communication terminal 100 cannot
correctly hold the content, where the expiration date of the content's
delivery (usage) has already passed, and where the content's delivery to the
communication terminal having made the request is not permitted.
[0057] If the requested content is undeliverable, then in the process
30 of a step 15, the control message transmission/reception unit 112 transmits
15
a response message expressing the undeliverability to the communication
terminal having made the request. Then, the process of the step 12 is
performed again, and thereby, the control message transmission/reception
unit 112 continues to exchange summary vector messages.
5 [0058] On the other hand, if the requested content is deliverable,
then in the process of a step 16, the control message transmission/reception
unit 112 transmits a response message expressing the deliverability to the
communication terminal. Then, the process is handed over from the control
message transmission/reception unit 112 to the content
10 transmission/reception unit 113 by the application software 111. In the
process of a step 17, the content transmission/reception unit 113 sets the
operation mode of the wireless LAN interface unit 116 at the infrastructure
mode.
[0059] After the setting of the operation mode of the wireless LAN
15 interface unit 1 1 6 at the infrastructure mode, the content
transmission/reception unit 113 performs actual content transfer in the
process of a step 18, and thereby transmits (delivers) the requested
content.
[0060] When delivery of the content has been completed in the
20 process of the step 18, subsequently in the process of the step 11, the
control message transmission/reception unit 1 12 sets the operation mode of
the wireless LAN interface unit 1 1 6 at the ad hoc mode, and thereby
continues to exchange summary vector messages.
[0061] In the above description given of operation of content
25 delivery performed by the communication terminal 100 using Epidemic
Routing in the present exemplary embodiment, the operation for two
communication terminals is exemplified, the operation is similarly
applicable to three or more terminals.
[0062] Hereinafter, the effect of the present exemplary embodiment
30 will be described.
16
[0063] In the present exemplary embodiment, when content
delivery is performed among communication terminals via a wireless LAN,
each of the communication terminals performs the step of exchanging with
the other communication terminals control messages until a request for
5 content delivery is made, with setting its wireless LAN interface at an ad
hoc mode, and subsequently performs the step of delivering a content to or
from the other communication terminals, with setting its wireless LAN
interface at an infrastructure mode.
[0064] As a result of that way of settings, during exchanging
10 control messages, because of the characteristics of the ad hoc mode, the
exchange can be performed in a peer to peer type manner and in a short
link-up time, and it becomes easy to be aware of a neighboring
communication terminal and of a content not in the own possession even in
an unstable wireless network such as a DTN.
15 [0065] Further, during content delivery, because of the
characteristics of the infrastructure mode, the delivery can be performed
with higher security, higher communication speed and higher utilization
efficiency of wireless resources than those in the ad hoc mode, and it
accordingly becomes possible to efficiently deliver contents having a
20 larger volume and higher confidentiality than control messages.
[0066] The whole or part of the exemplary embodiments disclosed
above can be described as, but not limited to, the following supplementary
notes.
[0067] (supplementary note 1) A content delivery method for
25 performing content delivery among a plurality of communication terminals
via a wireless LAN, and the method comprises:
a step wherein the plurality of communication terminals exchange
with each other control messages to be transmitted and received until a
request for the content delivery is made, in an ad hoc mode; and
30 a step wherein a communication terminal having received the
17
request for the content delivery, among the plurality of communication
terminals, delivers the content to a communication terminal having
requested the content delivery, in an infrastructure mode.
[0068] (supplementary note 2) The content delivery method
5 according to supplementary note 1, further comprising:
a step wherein each of the communication terminals switches the
operation mode of a wireless LAN adapter provided in the communication
terminal from the ad hoc mode to the infrastructure mode.
[0069] (supplementary note 3) The content delivery method
10 according to supplementary note 1, comprising:
a step wherein each of the communication terminals, by comprising
a wireless LAN adapter provided with a first virtual interface set at the ad
hoc mode and a second virtual interface set at the infrastructure mode, uses
the first interface when transmitting or receiving data in the ad hoc mode;
15 and
a step wherein each of the communication terminals uses the second
interface when transmitting or receiving data in the infrastructure mode.
[0070] (supplementary note 4) The content delivery method
according to any one of supplementary notes 1 to 3, comprising:
20 a step wherein each of the communication terminals operates as an
access point when delivering the content in the infrastructure mode; and
a step wherein each of the communication terminals operates as a
client when receiving the content in the infrastructure mode.
[0071] (supplementary note 5) A communication terminal
25 comprising:
a wireless LAN interface unit for performing wireless LAN
communication with other communication terminals;
a control message transmission/reception unit for setting the
wireless LAN interface unit at an ad hoc mode and exchanging with the
30 other communication terminals, via the wireless LAN interface unit,
18
control messages to be transmitted and received until a request for content
delivery is made; and
a content transmission/reception unit for, when having received the
request for the content delivery, setting the wireless LAN interface unit at
5 an infrastructure mode and delivering the content via the wireless LAN
interface unit.
[0072] (supplementary note 6) The communication terminal
according to supplementary note 5, wherein
the content transmission/reception unit switches the operation mode
10 of a wireless LAN adapter provided in the wireless LAN interface unit
from the ad hoc mode to the infrastructure mode.
[0073] (supplementary note 7) The communication terminal
according to supplementary note 5, wherein
the wireless LAN interface unit comprises a wireless LAN adapter
15 provided with a first virtual interface set at the ad hoc mode and a second
virtual interface set at the infrastructure mode, and uses the first interface
when transmitting or receiving data in the ad hoc mode and uses the second
interface when transmitting or receiving data in the infrastructure mode.
[0074] (supplementary note 8) The communication terminal
20 according to any one of supplementary notes 5 to 7, wherein
the communication terminal operates as an access point when
delivering the content in the infrastructure mode, and operates as a client
when receiving the content in the infrastructure mode.
[0075] While the invention has been particularly shown and
25 described with reference to exemplary embodiments thereof, the invention
is not limited to these embodiments. It will be understood by those of
ordinary skill in the art that various changes in form and details may be
made therein without departing from the spirit and scope of the present
invention as defined by the claims.
30 [0076] This application is based upon and claims the benefit of
19
priority from Japanese patent application No. 2012-228770, filed on
October 16, 2012, the disclosure of which is incorporated herein in its
entirety by reference.

WE CLAIM:
[1] A content delivery method for performing content delivery
among a plurality of communication terminals via a wireless LAN, and the
method comprises:
5 a step wherein the plurality of communication terminals exchange
with each other control messages to be transmitted and received until a
request for the content delivery is made, in an ad hoc mode; and
a step wherein a communication terminal having received the
request for the content delivery, among the plurality of communication
10 terminals, delivers the content to a communication terminal having
requested the content delivery, in an infrastructure mode.
[2] The content delivery method according to claim 1, further
comprising
a step wherein each of the communication terminals switches the
15 operation mode of a wireless LAN adapter provided in the communication
terminal from the ad hoc mode to the infrastructure mode.
[3] The content delivery method according to claim 1, comprising:
a step wherein each of the communication terminals, by comprising
a wireless LAN adapter provided with a first virtual interface set at the ad
20 hoc mode and a second virtual interface set at the infrastructure mode, uses
the first interface when transmitting or receiving data in the ad hoc mode;
and
a step wherein each of the communication terminals uses the second
interface when transmitting or receiving data in the infrastructure mode.
25 [4] The content delivery method according to any one of claims 1 to
3, comprising:
a step wherein each of the communication terminals operates as an
access point when delivering the content in the infrastructure mode; and
a step wherein each of the communication terminals operates as a
30 client when receiving the content in the infrastructure mode.
21
[5] A communication terminal comprising:
a wireless LAN interface unit for performing wireless LAN
communication with other communication terminals;
a control message transmission/reception unit for setting the
5 wireless LAN interface unit at an ad hoc mode and exchanging with the
other communication terminals, via the wireless LAN interface unit,
control messages to be transmitted and received until a request for content
delivery is made; and
a content transmission/reception unit for, when having received the
10 request for the content delivery, setting the wireless LAN interface unit at
an infrastructure mode and delivering the content via the wireless LAN
interface unit.
[6] The communication terminal according to claim 5, wherein
the content transmission/reception unit switches the operation mode
15 of a wireless LAN adapter provided in the wireless LAN interface unit
from the ad hoc mode to the infrastructure mode.
[7] The communication terminal according to claim 5, wherein
the wireless LAN interface unit comprises a wireless LAN adapter
provided with a first virtual interface set at the ad hoc mode and a second
20 virtual interface set at the infrastructure mode, and uses the first interface
when transmitting or receiving data in the ad hoc mode and uses the second
interface when transmitting or receiving data in the infrastructure mode.
[8] The communication terminal according to any one of claims 5 to
7, wherein
25 the communication terminal operates as an access point when
delivering the content in the infrastructure mode, and operates as a client
when receiving the content in the infrastructure mode.