Title: Communication apparatus and communication method
Abstract: A communication apparatus which is in a wireless network is characterized by comprising a communication means transmitting information among the other communication devices, a means receiving priority order information representing stand-by times different in each communication device from the control station and setting communication devices as control station candidates in a memory, and a means performing communication control as a control station in the wireless network when the stand-by time elapses.
Patent Number: 6,987,967 Issued on 01/17/2006 to Maeshima, et al.
| Inventors:
|
Maeshima; Yasunori (Tokyo, JP);
Sugaya; Shigeru (Kanagawa, JP);
Sugita; Takehiro (Kanagawa, JP)
|
| Assignee:
|
Sony Corporation (Tokyo, JP)
|
| Appl. No.:
|
082875 |
| Filed:
|
March 18, 2005 |
Foreign Application Priority Data
| Aug 30, 2000[JP] | 2000-261585 |
| Nov 27, 2000[JP] | 2000-359729 |
| Current U.S. Class: |
455/422.1; 455/500; 455/507; 370/254 |
| Current Intern'l Class: |
H04Q 7/20 (20060101) |
| Field of Search: |
455/500,507,420
370/449,457
|
References Cited [Referenced By]
U.S. Patent Documents
Primary Examiner: Trost; William
Assistant Examiner: Miller; Brandon J.
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation of application Ser. No. 09/940,579, filed
Aug. 29, 2001 now U.S. Pat. No. 6,876,850, the entire contents being incorporated
herein by reference.
Claims
What is claimed is:
1. A communication apparatus employing a plurality of communication devices to
construct a wireless network to be a control station transmitting management information
in the wireless network, the communication apparatus comprising:
a communication means transmitting information among the plurality of communication devices;
a determining means determining as to whether, when the control station disappears
from the wireless network, in order that any one of other communication devices
is newly operated as a control station, the other communication devices have a
control function as a control station candidate or not;
a set means setting priority order for each of control station candidates when
there exist a plurality of communication devices to be the control station candidates; and
a notification means for notifying the wireless network of priority order information
of the control station candidates, said priority order information identifying
a predetermined ordering of at least a subset of said other communication devices
based on at least one of performance and coverage information so as to avoid negotiation
between said other communication devices regarding which ultimately operates as
a replacement control station,
wherein the notification means specifies, as the priority order information,
stand-by times corresponding to the times until the respective control station
candidates start to reconstruct the wireless network, and
the set means sets the priority order in the order of the number of other communication
devices capable of being connected with the control station candidate for the respective
control station candidates.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to network systems, communication apparatus, and
communication control methods wherein various kinds of information is transmitted,
for example, through radio signals, among a plurality of communication terminals.
2. Description of the Related Art
Conventionally, a network system, for example, in which wireless
transmitters are incorporated in personal computers or audio-video devices so as
to transmit information among these plural personal computers or audio-video devices
is known. In such network system, employed generally is a method in which various
types of transmission managements are performed under the control of one central
control station, and a plurality of terminal stations are controlled. In this case,
a communicating station operating as a control station is set so as to subordinate
other communicating stations to the control station to form a network while employing
a plurality of wireless communication devices.
In the case where a network is formed employing a plurality of wireless communication
devices, a wireless communication control method and the like has been considered
wherein a predetermined wireless communication device is specified as the control
station of the network, and, for example, a periodic transmission frame cycle is
set, or access control of an information transmission region is performed, based
on the control of the control station.
In recent years, a wireless communication device has been developed wherein so
called an adhoc wireless network can be constructed in which a specific wireless
communication device is not determined as the control station from the beginning,
and an arbitrary wireless communication device is set as the control station of
the wireless network as the need arises so that information can be communicated
without any access points. For example, in Japanese Patent Application Laid-Open
No. 2000-082989, disclosed is a wireless communication method where so called an
adhoc wireless network is constructed in which information can be communicated
without any access points while a control station mode and a terminal station mode
are switched alternately.
However, in this conventional network system, it is supposed that some inconvenience
occurs in a central control station, and the function of the central control station
is damaged. In this case, in the conventional network system, a necessity occurs
wherein the operating condition of the network is once reset, and another terminal
station becomes the central control station so that a wireless network is newly
constructed once again. Thus, in the conventional network system, in order to perform
this reset (reconstruction of the new wireless network), data transmitted on the
network operating so far is temporarily suspended, taking an enormous time period
until the network is operated once again.
In order to solve the problem, in Japanese Patent Application Laid-Open No. 2000-151618,
the present applicant has proposed a system in which another terminal station in
the network is operated as a central control station automatically when some inconvenience
occurs in the central control station (master control station) in the network.
In this proposed system, the central control station needs to specify in advance
a terminal station which would be the central control station when an inconvenience
occurs in the master control station as a slave control station. However, for example,
in a case where a common power supply is employed for the master control station
and the slave control station, when only one slave control station is prepared
in the network, and when an inconvenience occurs in both stations at the same time,
such problem cannot be dealt with.
SUMMARY OF THE INVENTION
The present invention was developed considering such circumstances, and it is
an object of the present invention to provide communication devices and communication
methods by which stable information transmissions can be performed without stopping
the operating condition even when some inconvenience occurs in a central control station.
A communication apparatus, according to the present invention, which employs a
plurality of communication devices to construct a wireless network to be a control
station transmitting management information in the wireless network, is characterized
by comprising a communication means transmitting information among the plurality
of communication devices, a determining means determining as to whether, when the
control station disappears from the wireless network, in order that any one of
other communication devices is newly operated as a control station, the other communication
devices have a control function as a control station candidate or not, a set means
setting priority order for each of control station candidates when there exist
a plurality of communication devices to be the control station candidates, and
a notification means notifying the wireless network of priority order information
of the control station candidates.
That is, for the time when the master control station becomes incapable of communication,
priority order is set in advance for a plurality of slave control station candidates
in the wireless network.
A communication apparatus, according to the present invention, which is in a
wireless
network, is characterized by comprising a communication means transmitting information
among the other communication devices, a means receiving priority order information
representing stand-by times different in each communication device from the control
station and setting communication devices as control station candidates in a memory,
and a means performing communication control as a control station in the wireless
network when the stand-by time elapses.
That is, when the master control station becomes incapable of communication,
it is set that a plurality of slave control stations perform communication control
as control stations sequentially based on preset priority order.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an explanatory view illustrating an example of a network system structure
according to one embodiment of the present invention;
FIG. 2 is a block diagram illustrating an example of a communication terminal
structure according to one embodiment of the present invention;
FIG. 3 is an explanatory view illustrating an example of a frame structure according
to one embodiment of the present invention;
FIG. 4 is an explanatory view illustrating a communicable region of one communication
terminal (terminal 101) in a network system according to one embodiment
of the present invention;
FIG. 5 is an explanatory view illustrating a communicable region of one communication
terminal (terminal 102) in a network system according to one embodiment
of the present invention;
FIG. 6 is an explanatory view illustrating a communicable region of one communication
terminal (terminal 103) in a network system according to one embodiment
of the present invention;
FIG. 7 is an explanatory view illustrating a communicable region of one communication
terminal (terminal 104) in a network system according to one embodiment
of the present invention;
FIG. 8 is an explanatory view illustrating a communicable region of one communication
terminal (terminal 105) in a network system according to one embodiment
of the present invention;
FIG. 9 is an explanatory view illustrating a communicable region of one communication
terminal (terminal 106) in a network system according to one embodiment
of the present invention;
FIG. 10 is an explanatory view illustrating a communicable region of one communication
terminal (terminal 107) in a network system according to one embodiment
of the present invention;
FIG. 11 is an explanatory view illustrating a communicable region of one communication
terminal (terminal 107) in a network system according to one embodiment
of the present invention;
FIG. 12 is an explanatory view illustrating a communicable region of one communication
terminal (terminal 105) in a network system according to one embodiment
of the present invention;
FIG. 13 is an explanatory view illustrating a communicable region of one communication
terminal (terminal 103) in a network system according to one embodiment
of the present invention;
FIG. 14 is a flow chart explaining operations of a communication terminal as
a master control station according to one embodiment of the present invention;
FIG. 15 is a flow chart explaining operations of the time when a communication
terminal is set as a slave control station according to one embodiment of the present invention;
FIG. 16 is a flow chart explaining operations of a communication terminal as
a slave control station according to one embodiment of the present invention;
FIG. 17 is a chart illustrating network stand-by time for each communicating
station according to one embodiment of the present invention, and FIG. 17A corresponds
to a communication device 211, FIG. 17B a communication device 212,
FIG. 17C a communication device 213, FIG. 17D a communication device 214,
FIG. 17E a communication device 215, FIG. 17F a communication device 216,
and FIG. 17G a communication device 217;
FIG. 18 is a chart illustrating transition states of changes in network stand-by
time for each communicating station according to one embodiment of the present
invention, and FIG. 18A corresponds to the communication device 211, FIG.
18B the communication device 212, FIG. 18C the communication device 213,
FIG. 18D the communication device 214, FIG. 18E the communication device
215, FIG. 18F the communication device 216, and FIG. 18G the communication
device 217;
FIG. 19 is a chart illustrating confirmation states of changes in network stand-by
time for each communicating station according to one embodiment of the present
invention, and FIG. 19A corresponds to the communication device 211, FIG.
19B the communication device 212, FIG. 19C the communication device 213,
FIG. 19D the communication device 214, FIG. 19E the communication device
215, FIG. 19F the communication device 216, and FIG. 19G the communication
device 217;
FIG. 20 is a chart illustrating a transmission sequence example of control station
candidate information according to one embodiment of the present invention;
FIG. 21 is a view illustrating an example of the structure of a control station
candidate specifying packet according to one embodiment of the present invention; and
FIG. 22 is a view illustrating an example of the structure of a priority order
confirming packet according to one embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Network systems to which the present invention is applied are explained as
embodiments of the present invention below referring to drawings.
1) Embodiment 1
A network system
1 is, for example, composed of eight communication terminals
100,
101,
102,
103,
104,
105,
106,
107 as shown in FIG. 1. The respective communication terminals
100
to
107 perform wireless communications of signals obtained by modulating,
for example, carrier waves of 5 GHz, and mutually transmit information. Here, the
communication terminal
100 becomes a central control station (master control
station) and directly controls communications of all peripheral stations
101
to
107 in a radio wave attainable region
10 of the communication
terminal
100. When the communication terminal
100 cannot perform
operations as the central control station, the communication terminals
103,
105,
107 are here prepared as communication terminals (slave control
stations) which can be the central control stations. Here, a radio wave attainable
region
13 of the communication terminal
103, a radio wave attainable
region
15 of the communication terminal
105, and a radio wave attainable
region
17 of the communication terminal
107 do not cover all communication
terminals in the network system
1. However, transmitting with a terminal
outside of a radio wave attainable region is possible through a relay transmission
as described later on.
FIG. 2 is a diagram illustrating the respective communication terminals
100
to
107 and a configuration connected to the communication terminals. Here,
two wireless communication devices
20A,
20B are shown. The respective
wireless communication devices
20A,
20B are provided with transmission
control management sections
22A,
22B to which management information
storing sections
21A,
21B are connected, and wireless transmission
processing is performed under the control of the transmission control management
sections
22A,
22B. The data transmission processing between devices
27A,
27B connected to the respective wireless communication devices
20A,
20B is performed in interface sections
23A,
23B.
High frequency transmission processing sections
25A,
25B are connected
to the interface sections
23A,
23B via coding/decoding sections
24A,
24B, and sending and receiving of radio signals are performed through antennas
26A,
26B connected to the high frequency transmission processing
sections
25A,
25B. Various information devices such as a personal
computer unit, an audio-video device, or the like, are employed as the devices
27A,
27B connected to the wireless communication devices
20A,
20B.
The management information storing sections
21A,
21B store network
management information, operating program, and the like, such as information necessary
as a master control station and a slave control station (the details are set forth
later on). These management information storing sections
21A,
21B
also store and hold data related to the priority order that a slave control station
described later on needs.
The transmission control management sections
22A,
22B govern and
control the interface sections
23A,
23B, the coding/decoding sections
24A,
24B, and the high frequency transmission processing sections
25A,
25B based on the information stored in the management information
storing sections
21A,
21B. The interface sections
23A,
23B
send/receive data to/from the devices
27A,
27B connected to the wireless
communication devices such as a personal computer unit and an audio-video device.
The connections between the interface sections
23A,
23B and the devices
27A,
27B are bridges in conformity to a bus line standardized, for
example, as IEEE (The Institute of Electrical and Electronics Engineers) 1394 format.
The coding/decoding sections
24A,
24B perform coding of data transmitted
via the network and decoding of data received via the network. The high frequency
transmission processing sections
25A,
25B perform modulation/demodulation
processing or the like of data transmitted via the antennas
26A,
26B.
The wireless communication devices
20A,
20B are not limited to
ones with the structures as shown in FIG. 2, and any other structures can be employed
as far as they can realize the present invention. Although only two wireless transmission
devices are shown in FIG. 2, for example, in the case of the network structure
shown in FIG. 1, the network system
1 is formed preparing eight wireless
transmission devices. However, it is not necessary that all the wireless transmission
devices in the network system
1 are connected to devices (the devices
27A,
27B in FIG. 2) such as a personal computer unit or an audio-video device.
The transmission control management sections
22A,
22B do not have
to make all the wireless transmission devices in the network system
1 perform
control operations necessary as a master control station or a slave control station,
and for example, a means or a program for performing control operations are not
necessary to be prepared for some number of wireless transmission devices in the
network system
1. In the explanation below, all wireless transmission devices
in the network system
1 can be a master control station or a slave control station.
An example of a frame structure of data transmitted among the respective communication
terminals
100 to
107 is shown in FIG. 3.
The transmission among the respective communication terminals
100 to
107
is performed in setting a frame period here. One frame is, for example, set to
4 ms, and a media information transmission region and a control information transmission
region are provided in one frame so that this frame structure is repeated. Real
data exchanged among the respective communication terminals
100 to
107
is transmitted in the media information transmission region. The control information
transmission region is provided with a section in which descending control information
that a master station transmits control information to the respective communication
terminals is transmitted and a section in which all communication terminals on
the network transmit ascending control information. Another frame structure may
be set wherein a fixed time slot divided for each station is prepared between the
ascending control information transmitting sections, and the ascending control
information is sent/received to/from all stations on the network so that mutual
connection condition is confirmed through information of connection link relationship
among respective stations.
In the network system
1 of such structure, a master control station functioning
as a central control station performing management of the information transmission
among the respective communication terminals is set. In the network system
1
shown in FIG. 1, for example, the communication terminal
100 is set as the
master control station (hereafter, this communication terminal
100 may also
be called the master control station
100). This master control station
100
transmits management information in the section in which the descending control
information described above is transmitted and controls transmission of data by
the respective communication terminals. The peripheral communication terminals
101 to
107 exist in the radio wave attainable region
10 of
the master control station
100. That is, the master control station
100
can directly communicate with the peripheral communication terminals
101
to
107.
In the network system
1 having such structure, when an inconvenience occurs
in the master control station
100 and the master control station
100
does not carry out the function as the central control station, a plurality of
slave control stations carrying out the function as the central control station
are set as a substitute for the master control station
100. In the network
system
100 shown in FIG. 1, for example, three communication terminals
103,
105,
107 are set as the slave control stations (hereafter, these
communication terminals
103,
105,
107 may also be called the
slave control stations). In this case, priority order is set for the case where
the communication terminals
103,
105,
107 carry out the function
as the central control stations among the three communication terminals
103,
105,
107. This priority order is determined by the master control
station
100 instructing one terminal to be a slave control station, and
the order of the stations are stored in the respective slave control stations
103,
105,
107 themselves.
These slave control station
103,
105,
107 transmit the
management information during the section in which the descending control information
described above is transmitted and control transmission of data by the respective
communication terminals when the function as the central control station is not
carried out since an inconvenience occurs in the master control station
100.
However, processing to transmit the management information in accordance with the
priority order described above is supposed to be performed, and when a state where
transmission control is correctly performed by any one of the slave control stations
occurs, other slave control stations do not carry out the transmission control
and wait.
Here, in the network system
1, the master control station
100
specifies three communication terminals as slave control stations in the order
of most excellent communication terminals in an information transmission condition
with other peripheral stations among the peripheral communication terminals
101
to
107 with which the master control station
100 can directly communicate.
The communication terminal excellent in the information transmission condition
herein is determined, for example, from the number of communication terminals capable
of direct communication in the network and communication quality with the respective
communication terminals. Specifically, for example, in the order from a communication
terminal with which the number of communication terminals capable of direct communication
in the network is the largest, one is set as a slave control station with a high
priority order, and when the number of communication terminals capable of direct
communication in the network is the same, a communication terminal for which the
communication quality with other communication terminals at the time is judged
as being excellent is selected as a slave control station with a high priority
order. The communication quality herein is determined from, for example, the electric
power of a received signal, error rate, or the like.
For a determination as to whether there is a connection with a peripheral station,
which is necessary in making the above decisions, for example, techniques described
in Japanese Patent Application No. Hei 10-47416 (Counterpart application in U.S.
Ser. No. 09/252,807 and Japanese Patent Application No. Hei 10-258855 (Counterpart
application in U.S. Ser. No. 09/392,739 that the present applicant has proposed
may be employed wherein respective stations on a network mutually send/receive
ascending control information in a fixed time slot to grasp a station existing
around a station itself.
Here, decision processing for selecting a slave control station in the network
system
1 of the present example is explained. When a case where the communication
terminal
101 is set as the central control station is supposed, the communication
terminals
100,
102,
106,
107 exist in a radio wave
attainable region
11, and the communication terminal
101 can communicate
with these four stations as shown in FIG. 4.
The communication terminals
100,
101,
103,
107 exist
in a radio wave attainable region
12, and the communication terminal
102
can communicate with these four stations as shown in FIG. 5.
The communication terminals
100,
102,
104,
105,
107
exist in a radio wave attainable region
13, and the communication terminal
103 can communicate with these five stations as shown in FIG. 6.
The communication terminals
100,
103,
105 exist in a radio
wave attainable region
14, and the communication terminal
104 can
communicate with these three stations as shown in FIG. 7.
The communication terminals
100,
103,
104,
106,
107
exist in a radio wave attainable region
15, and the communication terminal
105 can communicate with these five stations as shown in FIG. 8.
The communication terminals
100,
101,
105,
107 exist
in a radio wave attainable region
16, and the communication terminal
106
can communicate with these four stations as shown in FIG. 9.
The communication terminals
100,
101,
102,
103,
105,
106 exist in a radio wave attainable region, and the communication terminal
107 can communicate with these six stations as shown in FIG. 10.
As a result, in the network system
1, other than the central control station
100, since the communication terminal
107 can connect with the largest
number of communication terminals (can connect with six stations), the communication
terminal
107 is specified as a slave control station whose priority order
is the highest.
Since the number of communication terminals capable of connection regarding
the communication terminal
103 and the communication terminal
105
is large (communication with five stations is possible) next to that of the communication
terminal
107, these two communication terminals
103,
105 are
also specified as the slave control stations. However, since the number of stations
capable of connection is the same in the two communication terminals
103,
105, the priority order of a terminal in which it is determined that the
communication quality between each communication terminal
103,
105
and other communication terminals is excellent is set to a higher order. Here,
while it is supposed that it is determined that the communication quality with
peripheral stations regarding the communication terminal
105 is more excellent
than that regarding the communication terminal
103, the communication terminal
105 is specified as second slave control station in the priority order,
and the communication terminal
103 is specified as third slave control station
in the priority order.
The decision regarding the communication quality for determining the order between
the slave control station
103 and the slave control station
105 may
be made from other factors. For example, either station in the two communication
terminals
103,
105 which can directly communicate excellently with
the master control station
100 (that is, a station that is supposed to be
closer to the master control station) may be set to a higher order in the priority
order. Also, in the case where the number of stations capable of direct connection
is the same, a communication control station with a newer address may be simply
specified as a slave control with a higher priority order without determining the
communication quality as described above.
When the master control station
100 selects three slave control stations
103,
105,
107 as described above, the master control station
100 informs the entire network that the communication terminals
103,
105,
107 are specified as slave control stations. This notification
may be made through a broadcast transmission by descending control information.
In order to confirm the condition, confirmation information may be transmitted
by ascending control information. At this notification time, information regarding
the priority order of the three slave control stations
103,
105,
107 may also be notified.
In the notified three slave control stations
103,
105,
107,
based on the priority order of a station itself specified at the time, a stand-by
time of the time the master control station comes to a state where communication
is not possible is registered. Here, the stand-by time for the communication terminal
107 that is first in the priority order is set to 1 second, the stand-by
time for the communication terminal
105 that is second in the priority order
is set to 2 seconds, and the stand-by time for the communication terminal
103
that is third in the priority order is set to 3 seconds. In the case where there
are four or more slave control stations, each one second of stand-by time may be
added further each time the order is lowered.
FIG. 11 illustrates a communication state in the network of the time the communication
terminal
107 that is a slave control station becomes the central control
station when the master control station
100 becomes incapable of communication.
At this time, since the descending control information transmitted from the slave
control station
107 does not directly reach the communication terminal
104,
another communication terminal
103 or
105 needs to relay and transmit
it. The transmission of ascending control information and/or real data is also
needed to be relayed similarly.
FIG. 12 illustrates a communication state in the network of the time the communication
terminal
105 that is a slave control station becomes the central control
station when the master control station
100 becomes incapable of communication.
At this time, since the descending control information transmitted from the slave
control station
105 does not directly reach the communication terminals
101,
102, other communication terminals
103,
107 need
to relay and transmit it. The transmission of ascending control information and/or
real data is also needed to be relayed similarly.
FIG. 13 illustrates a communication state in the network of the time the communication
terminal
103 that is a slave control station becomes the central control
station when the master control station
100 becomes incapable of communication.
At this time, since the descending control information transmitted from the slave
control station
103 does not directly reach the communication terminals
101,
106, other communication terminals
102 and
105
or
107 need to relay and transmit it. The transmission of ascending control
information and/or real data is also needed to be relayed similarly.
With respect to processing incorporating a communication terminal existing outside
of a radio wave attainable region of a control station into a network by relay
and transmission, for example, it is possible to employing a technique shown in
Japanese Patent Application No. Hei 10-258855 submitted by the present applicant
and incorporate such terminal into the network as a hidden terminal station.
Next, operations of the master control station
100 are explained employing
a flow chart shown in FIG. 14.
The master control station
100 first forms network common information
from a collection result of connection information of the network and information
of a specified slave control station at step S
11. Then, at step S
12,
a broadcast transmission is performed on the network in the descending control
information communication section.
Thereafter, the master control station
100 receives the ascending
information sent from the peripheral communication terminals
101 to
107
at step S
13. Connection condition of the network is then grasped at step S
14.
The master control station
100 specifies and registers as slave control
stations three communication terminals in the order from a station in which the
number of connection links is the largest among the peripheral communication terminals
101 to
107 at step S
15.
Next, operations in the communication terminals
101 to
107 other
than the master control station
100 are explained employing a flow chart
shown in FIG. 15.
The communication terminals
101 to
107 receive the descending information
sent from the central control station (the master control station
100) at
step S
21. Confirmation operation of network information of the descending
control information is then performed at step S
22.
Here, as a result of analysis of the information, when specifying as slave
control stations is performed by the master control station at step S
23,
operation to register as slave control stations is performed proceeding to step
S
24. At this time, at step S
25, from a specified priority order,
the stand-by time until the time of performing control operation as a central control
station is registered. This registration is performed by storing it, for example,
in the management information storing sections
21A,
21B of the wireless
transmission devices
20A,
20B shown in FIG. 2 under the control of
the transmission control management sections
22A,
22B. When the registration
as a slave control station is performed, the confirmation information may be sent
to the master control station (central control station), employing the ascending
control information and the like.
When it is determined that the number of communication terminals with which
that slave control station can directly communicate is larger than that of the
master control station from network connection condition determined at the time
of specifying a slave control station, a change request of a control station may
be sent to the master control station so that the slave control station becomes
the central control station.
Next, operations in the communication terminals (slave control stations
103,
105,
107) registered as slave control stations are explained employing
a flow chart shown in FIG. 16.
The communication terminals as the slave control stations first try to receive
the descending control information sent from the central control station (the master
control station
100) at step S
31.
When the descending control signal can be received at step S
31, network
information is confirmed with peripheral communication terminals at step S
32.
At step S
33, it is determined whether or not specifying as a slave control
station is cancelled from the master control station, and when the specifying as
a slave control station is cancelled, the specifying as a slave control stations
is cancelled so that a station performs an operation as a usual peripheral terminal
station at step S
34. When the specifying is not cancelled, an operation
as a slave control station is performed as it is.
When the descending control information cannot be received at step S
31,
the ascending control information is received at step S
35, and connection
condition of the network is grasped at step S
36. Then, at step S
37,
it is determined whether or not an inconvenience occurs in the master control station.
With respect to the determination as to whether or not an inconvenience occurs
in the master control station herein, for example, when the descending management
information periodically transmitted from the master control station cannot be
received, it is determined that an inconvenience is occurring in the master control
station. However, since it can also be supposed that the descending management
information cannot be received from about one time to several times for some reason
even when the master control station operates correctly, it is preferred that it
is determined that an inconvenience is occurring in the master control station
when the descending management information cannot be received for some time continuously.
Further, when the master control station cannot be recognized in all other peripheral
terminal stations from the connection condition of the network grasped at step
S
36 (that is, the signal from the master control station cannot be received),
it may be determined that an inconvenience is occurring in the master control station.
When it is determined that an inconvenience is occurring in the master control
station, at step S
38, it is determined whether or not another station which
can operate as the control station is generated so that the descending management
information can be received. Here, when the descending management information comes
to be received, the station does not perform the operation as the central control
station (that is, does not perform management of information transmission by sending
of the descending management information) to perform the operation as a peripheral
terminal station at step S
39.
When the descending management information cannot be received at step S
38,
at step S
40, it is determined whether or not the stand-by time registered
in the station has elapsed since an inconvenience occurs in the master control
station. For example, in the slave control station
107 that is first in
the priority order, it is determined whether 1 second has elapsed since an inconvenience
occurs in the master control station. In the slave control station
105 that
is second in the priority order, it is determined whether 2 seconds has elapsed
since the inconvenience occurs in the master control station. In the slave control
station
103 that is third in the priority order, it is determined whether
3 seconds has elapsed since the inconvenience occurs in the master control station.
When it is determined that the stand-by time registered in the station has not
elapsed in the determining at step S
40, the step returns to the determining
of step S
38.
When it is determined that the stand-by time registered in the station has not
elapsed in the determining of step S
40, an operation necessary as the central
control station is performed. Specifically, periodic transmission of the descending
management information is started to carry out the management of information transmission
in the network at the station.
In the network system
1 of the embodiment of the present invention as
described
above, when some inconvenience occurs in the master control station
100
functioning as the central control station, a slave control station functions as
a central control station, and stable information transmission can be performed
without stopping the operating condition of the network.
In this case, since it is set that a slave control station which becomes a central
control station at the time an inconvenience occurs in the master control station
specifies a plurality of communication terminals in the network, in a state where
at least one among the specified slave control stations normally operates, the
operating condition at the time can be maintained without resetting the network,
and the possibility that the operating condition of the network can be maintained
can be enhanced compared with a case where only one is specified as a slave control
station. In this case, since priority order is set in the plurality of slave control
stations and the plurality of slave control stations are operated as central control
stations after standing by only each different stand-by time set in accordance
with the priority order, the plurality of slave control stations do not start to
operate as the central control stations at the same time, whereby a situation where
a plurality of central control stations exist in one network can be avoided reliably.
In the embodiment described above, although three communication terminals in
the
network are specified as slave control stations, two or four or more communication
terminals may be given priority order to be specified as slave control stations.
In this case, when all communication terminals in the network has a network structure
in which all communication terminals can be control stations, all the communication
terminals may be given priority order to be specified as slave control stations.
In the embodiment described above, when a terminal to be specified as a slave
control station is selected, although a determination is made from the number of
terminals with which the terminal can communicate or the communication quality,
the determination may be made from another factor. For example, even in a structure
where a corresponding communication terminal can operate as a slave control station,
when it is not preferable for the corresponding communication terminal to be a
control station from the structure and/or the operating condition of the corresponding
communication terminal, the communication terminal may be ruled out from candidates
of the terminals specified as slave control stations.
Specifically, for example, a corresponding communication terminal may
be specified as a slave control station only when being operated by supply of commercial
AC power, and the terminal may not be specified as a slave control station when
an incorporated battery is employed as a power supply so as to restrain the consumption
of a battery. Or, one communication terminal in which a battery is set as the power
supply among a plurality of specified slave control stations may be specified as
one slave control station (however, it is preferred to specify the communication
terminal whose priority order is low as a slave control station), so that the operating
condition of the network may be maintained even when a service interruption occurs
wherein the supply of AC power to some number of communication terminals in the
network system is temporarily stopped.
In the embodiment described above, although the stand-by time set based on the
priority order is of one second interval time such as 1 second, 2 seconds, 3 seconds,
the present invention is not limited to such stand-by time. In a structure in which
an inconvenience in a control station can be detected faster, a shorter time may
be set as the stand-by time.
Further, slave control stations may be operated in accordance with the order
in a process in which differences are provided in the stand-by time other than
the process in which slave control stations are operated based on the set priority order.
2) Embodiment 2
Next, a second embodiment of the present invention is described.
FIG. 17 is a chart illustrating stand-by time for each communicating station.
In the drawing, a communication device
214 to be an existing control station
shown in FIG. 17D selects communication devices
211,
215,
216
to be control station candidates each shown in FIG. 17A, FIG. 17E, and FIG. 17F,
and FIG. 17 illustrates a state where priority order P
1, P
2, P
3
is set among them.
Here, for the sake of convenience, it is specified that the communication device
215 is the control station candidate of priority order P
1 representing
first priority order, the communication device
211 is the control station
candidate of priority order P
2 representing second priority order, and the
communication device
216 is the control station candidate of priority order
P
3 representing third priority order, and reconstruction start times T
2,
T
4, T
6 each of which is from the time of reconstructing the wireless
network to the time of starting operations as control stations are set.
The communication device
215 of the control station candidate of priority
order P
1 sets 2 units as the reconstruction start time T
2 with respect
to a predetermined base unit T
1, the communication device
211 of
the control station candidate of priority order P
2 sets 4 units as the reconstruction
start time T
4 with respect to the predetermined base unit T
1, and
the communication device
216 of the control station candidate of priority
order P
3 sets 6 units as the reconstruction start time T
6 with respect
to the predetermined base unit T
1.
By this, in a case where the communication device
214 which is an existing
control station disappears from the wireless network, the communication device
215 of priority order P
1 of the control station candidate obeys the
priority order and performs the operation as a control station prior to other communication devices.
Other communication devices
212,
213,
217 which do not
have specified priority order are in a state where specifying of priority order
is not performed, and since the communication devices
212,
217 are
provided with control functions necessary to operate as control stations, the communication
devices
212,
217 are allowed to start operating as control stations
simultaneously after a predetermined simultaneous cancel time TR has elapsed.
Since the communication devices
213 is not provided with the control
function necessary to operate as a control station, it is set that the communication
devices
213 is subordinate to a communication device to be a control station
candidate to form the wireless network.
At the predetermined simultaneous cancel time TR, for example, maximumly 15 communication
devices other than the control station can be provided, and when considering that
T
2 is set as a reconstruction start time in each communication device, a
reconstruction start time can be set to 30T (=15×2T).
FIG. 18 is a chart illustrating transition states of changes in stand-by time
of each communicating station. FIG. 18 illustrates transition states of a case
where the priority order for each communication device set in FIG. 17 described
above is respectively changed.
The drawing shows a case where priority order P
2 representing second priority
order of the communication device
211 is changed to priority order P
1
representing first priority order, priority order P
1 representing first
priority order of the communication device
215 is changed to priority order
P
2 representing second priority order, and no priority order of the communication
device
217 is newly set to priority order P
4 representing fourth
priority order. There is no change in priority order P
3 representing third
priority order of the communication device
216.
Here, although specifying reconstruction start times is performed in even number
units T
2, T
4, T
6 with respect to the base unit T
1 according
to priority order in FIG. 17 described above, to avoid a state where the existing
setting of reconstruction start times T
2, T
4, T
6 are duplicated,
in FIG. 19, specifying reconstruction start times is performed in odd number units
T
1, T
3, T
5, T
7 with respect to the base unit T
1
so as not to overlap with those of FIG. 17.
That is, the communication device
211 of the control station candidate
of priority order P
1 sets
1 unit of the base unit T
1 as the
reconstruction start time T
1, the communication device
215 of the
control station candidate of priority order P
2 sets 3 units of the base
unit T
1 as the reconstruction start time T
3, the communication device
216 of the control station candidate of priority order P
3 sets 5
units for the predetermined base unit T
1 as the reconstruction start time
T
5, and the communication device
217 of the control station candidate
of priority order P
4 sets 7 units of the base unit T
1 as the reconstruction
start time T
7.
Another communication device
212 which does not have specified priority
order is in a state where specifying of priority order is not performed, and since
being provided with the control function necessary to operate as a control station,
the communication device
212 is allowed to start operating as a control
station simultaneously after a predetermined simultaneous cancel time TR has elapsed.
Since the communication devices
213 is not provided with the control
function necessary to operate as a control station, it is set that the communication
devices
213 is subordinate to a communication device to be a control station
candidate to form the wireless network.
FIG. 19 is a chart illustrating confirmation states of changes in stand-by time
for each communicating station. FIG. 19 illustrates confirmation states of a case
where the priority order for each communication device set in the transition states
of FIG. 18 described above are respectively confirmed in order to correspond to
changes on next priority order. Therefore, in a case where the priority order is
changed over again from confirmation states of FIG. 19, after shift to the transition
states of FIG. 18 is once performed, shift to the confirmation states of FIG. 19
is performed once again.
Here, in the confirmation states of FIG. 19, specifying reconstruction start
times is performed in even number units T
2, T
4, T
6, T
8
with respect to the base unit T
1 similarly to that of FIG. 17, although
specifying reconstruction start times is performed in odd number units T
1,
T
3, T
5, T
7 with respect to the base unit T
1 according
to priority order in the transition states of FIG. 18 described above.
That is, the communication device
211 of the control station candidate
of priority order P
1 sets 2 unit of the base unit T
1 as the reconstruction
start time T
2, the communication device
215 of the control station
candidate of priority order P
2 sets 4 units of the base unit T
1 as
the reconstruction start time T
4, the communication device
216 of
the control station candidate of priority order P
3 sets 6 units for the
predetermined base unit T
1 as the reconstruction start time T
6, and
the communication device
217 of the control station candidate of priority
order P
4 sets 8 units of the base unit T
1 as the reconstruction start
time T
8.
Another communication device
212 which does not have specified priority
order is in a state where specifying of priority order is not performed, and since
the communication device
212 is provided with the control function necessary
to operate as a control station, the communication device
212 is allowed
to start operating as a control station simultaneously after a predetermined simultaneous
cancel time TR has elapsed.
Since the communication devices
213 is not provided with the control
function necessary to operate as a control station, it is set that the communication
devices
213 is subordinate to a communication device to be a control station
candidate to form the wireless network.
FIG. 20 is a chart illustrating a transmission sequence of control station candidate information.
FIG. 20 illustrates an operation sequence in which the communication device
214 that is an existing control station determines priority order of each
communication device for the communication devices
211,
215,
216
to be control station candidates to inform the network of selection result.
First, at step S
51, priority order information is transmitted via a
broadcast from the communication device
214 that is an existing control
station to each communication device on the network. Specifically, the priority
order information is priority order P
1 to P
4 for communication devices
of each control station candidate shown in FIG. 17, FIG. 18, FIG. 19 described
above, the reconstruction start times T
1 to T
8 for reconstructing
the wireless network, and the like.
At step S
52, the communication device
211 to which priority order
is given through the priority order information transmitted via the broadcast sends
back receipt confirmation information for the priority order information to the
communication device
214 that is an existing control station. Specifically,
by the sending back of the receipt confirmation information from the communication
device
211, it becomes clear that the communication device
211 recognizes
the priority order P
1 to P
4 of the priority order information of
the stations in the network and the reconstruction start times T
1 to T
8.
At step S
53, similarly, the communication device
215 to which priority
order is given through the priority order information transmitted via the broadcast
sends back the receipt confirmation information for the priority order information
to the communication device
214 that is an existing control station. Specifically,
by the sending back of the receipt confirmation information from the communication
device
215, it becomes clear that the communication device
215 recognizes
the priority order P
1 to P
4 of the priority order information of
the stations in the network and the reconstruction start times T
1 to T
8.
At step S
54, similarly, the communication device
216 to which priority
order is given through the priority order information transmitted via the broadcast
sends back the receipt confirmation information for the priority order information
to the communication device
214 that is an existing control station. Specifically,
by the sending back of the receipt confirmation information from the communication
device
216, it becomes clear that the communication device
216 recognizes
the priority order P
1 to P
4 of the priority order information of
the stations in the network and the reconstruction start times T
1 to T
8.
Here, regarding the communication devices
212,
213,
217
which do not have specified priority order, reduction in transmission traffic can
be achieved by omitting sending back of the receipt confirmation of the priority order.
FIG
