U.S. patent application number 11/038059 was filed with the patent office on 2005-08-18 for radio network expansion method.
Invention is credited to Ebata, Tomoichi, Matsui, Susumu, Monden, Kazuya, Osafune, Tatsuaki.
Application Number | 20050181798 11/038059 |
Document ID | / |
Family ID | 34747386 |
Filed Date | 2005-08-18 |
United States Patent
Application |
20050181798 |
Kind Code |
A1 |
Monden, Kazuya ; et
al. |
August 18, 2005 |
Radio network expansion method
Abstract
One objective of the present invention is to determine a
location for a relay terminal in a radio network, without
preparatory surveying a radio status, and to arrange the relay
terminal at the location. Another objective is to provide a method
for retrieving the arranged relay terminal. When a relay terminal
is to be arranged, the relay terminal transmits a survey packet to
examine the quality of communication with a communication terminal
or other relay terminal. Wherer a location is appropriate, the
relay terminal gives a notice. The arranged terminal relays
communication. Further, when the relay terminal is to be retrieved,
the relay terminal carried by a user transmits a retrieval packet
to the arranged relay terminal, which notifies the user of its
presence by light, sounds, or returning a packet. In this manner, a
single relay terminal provides functions of arrangement, relay and
retrieval.
Inventors: |
Monden, Kazuya; (Yokohama,
JP) ; Ebata, Tomoichi; (Sagamihara, JP) ;
Matsui, Susumu; (Machida, JP) ; Osafune,
Tatsuaki; (Cannes, FR) |
Correspondence
Address: |
MATTINGLY, STANGER, MALUR & BRUNDIDGE, P.C.
1800 DIAGONAL ROAD
SUITE 370
ALEXANDRIA
VA
22314
US
|
Family ID: |
34747386 |
Appl. No.: |
11/038059 |
Filed: |
January 21, 2005 |
Current U.S.
Class: |
455/446 ;
455/15 |
Current CPC
Class: |
H04L 45/00 20130101;
H04W 64/00 20130101; H04W 88/04 20130101 |
Class at
Publication: |
455/446 ;
455/015 |
International
Class: |
H04B 007/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 30, 2004 |
JP |
2004-022462 |
Claims
1. A radio network expansion method, for a radio network wherein a
plurality of communication terminals transmit or receive data and
one or more relay terminals relay or transmit the data that are
transmitted or received by the communication terminals; and wherein
the relay terminals perform measure qualities of communication with
the communication terminals, and employ results obtained by the
measurements to designate locations at which the relay terminals
are to be arranged.
2. A radio network expansion method according to claim 1, whereby
evaluation values for the qualities of communication are the field
intensities of signals received by the relay terminals.
3. A radio network expansion method according to claim 1, whereby
evaluation values for the qualities of communication are
signal-to-noise ratios for signals received by the relay
terminals.
4. A radio network expansion method according to claim 1, whereby
the relay terminals are capable of designating locations accessible
by at least two communication terminals and/or relay terminals so
as to increase reliability when a communication cutoff occurs that
is caused by the halting of the functions of the relay terminals,
due to a failure at or the destruction of the relay terminals, or a
battery shortage.
5. A radio network expansion method according to claim 4, whereby
the locations accessible by at least two communication terminals
and/or relay terminals are determined based on the field
intensities of received signals or the signal-to-noise ratios of
the signals.
6. A radio network expansion method according to claim 1, whereby
the relay terminals performs a function selected from among a relay
terminal arrangement support function, a relay function and a
retrieval support function.
7. A radio network expansion method according to claim 1, whereby a
user of the communication terminal is notified, by the relay
terminals, of the locations and currently selected functions of the
relay terminals.
8. A radio network expansion method according to claim 7, whereby
lights having different colors, and sounds, are employed, by the
relay terminals, to notify the user of the communication terminal
of the locations and currently selected functions of the relay
terminals.
9. A radio network expansion method according to claim 1, whereby
the user of the communication terminal is notified, by the relay
terminals, that the relay terminals are present.
Description
INCORPORATION BY REFERENCE
[0001] This application claims priority based on a Japanese patent
application, No. 2004-022462 filed on Jan. 30, 2004, the entire
contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to an expansion method for a
radio network having communication terminals and a relay terminal
and a support method therefor, and also relates to the
communication terminals and the relay terminal.
[0003] To extend the communication range of a radio network, a
presently available method requires that a relay terminal be
positioned between a communication terminal and a base station. But
generally, when this method is employed, a radio wave status survey
must be performed in advance, to ensure that the relay terminal is
properly positioned and that a desired communication quality is
obtained. According to another method, however, the performance of
a preparatory radio wave status survey is not required. With this
method, in order to determine the location of a relay terminal that
relays a communication terminal and a base station, an adjustment
signal is transmitted by the base station (see, e.g., Japanese Laid
Open Patent Publication No. 2000-4469).
SUMMARY OF THE INVENTION
[0004] These conventional techniques, however, do not take into
consideration the method by which the location of a relay terminal
should be determined, and how to position the relay terminal cannot
easily be determined without a survey of the wave status being
performed.
[0005] Furthermore, the redundancy relative to the halting of the
function of a relay terminal is not taken into account, and
communication would be cut off due to the halting of the function
of the relay terminal.
[0006] In addition, a method for retrieving a thus arranged relay
terminal is not considered.
[0007] The present invention enables the arrangement of a relay
terminal without performing a preparatory survey of a radio wave
status. Also, a support function for retrieving the thus arranged
relay terminal is provided.
[0008] According to the present invention, in a radio network
having communication terminals that transmit or receive data and
relay terminals that relay data, each relay terminal transmits a
packet to detect the presence of a communication terminal relative
to the current location of the relay terminal, or the presence of
another relay terminal that can relay communications for the
communication terminal, and to examine communication quality, so
that the relay terminal can locate a site that can relay
communications for the communication terminal.
[0009] The relay terminal employs light or sound to indicate that
the current location is an appropriate one for relaying
communications for the communication terminal.
[0010] The relay terminal includes a communication quality
evaluation unit for determining whether the current location is an
appropriate one for relaying communications for the communication
terminal.
[0011] Further, provided is a method whereby, in order to prevent
the cutting off of communications for communication terminals, the
relay terminal is located so that it can communicate with at least
two communication terminals or with another relay terminal that can
communicate with the communication terminals.
[0012] Furthermore, in order to retrieve relay terminals that have
been located, a relay terminal used to support the collection
transmits packets to relay terminals in order to determine whether
they are within radio communication range, and relay terminals that
receive these packets verify their presence by employing lights or
sounds or by returning the packets.
[0013] The relay terminals have arrangement, relaying and retrieval
functions, and these functions can be switched so that all of them
can be provided by a single terminal.
[0014] According to the present invention, the arrangement and/or
collection of relay terminals used in a radio network is
enabled.
[0015] These and other benefits are described throughout the
present specification. A further understanding of the nature and
advantages of the invention may be realized by reference to the
remaining portions of the specification and the attached
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a diagram exemplifying the procedures of an
operation according to one embodiment of the present invention.
[0017] FIG. 2 is a diagram exemplifying an appropriate location
according to the embodiment wherein a relay terminal is
arranged.
[0018] FIG. 3 is a diagram exemplifying an appropriate location
according to the embodiment wherein a relay terminal that can
communicate with two or more terminals is arranged.
[0019] FIG. 4 is a flowchart exemplifying the arrangement support
function of a relay terminal according to the embodiment.
[0020] FIG. 5 is a flowchart exemplifying the arrangement support
function of the relay terminal according to the embodiment.
[0021] FIG. 6 exemplifies the detail flowchart of the object
terminal input subroutine shown in FIG. 4.
[0022] FIG. 7 is a diagram exemplifying the format of a survey
packet according to the embodiment.
[0023] FIG. 8 is a diagram exemplifying an object terminal
accessible list according to the embodiment.
[0024] FIG. 9 is a flowchart exemplifying the relay processing
according to the embodiment.
[0025] FIG. 10 is a diagram exemplifying the format of a survey
response packet according to the embodiment.
[0026] FIG. 11 is a diagram exemplifying the format of a retrieval
response packet according to the embodiment.
[0027] FIG. 12 is a diagram exemplifying the procedures of a
retrieval operation according to the embodiment.
[0028] FIG. 13 is a flowchart exemplifying a terminal retrieval
support function according to the embodiment.
[0029] FIG. 14 is a diagram exemplifying the format of a retrieval
packet according to the embodiment.
[0030] FIG. 15 is a diagram exemplifying a retrieved terminal list
according to the embodiment.
[0031] FIG. 16 is a diagram exemplifying the configuration of a
relay terminal according to the embodiment.
[0032] FIG. 17 is a diagram exemplifying the shifting of the
function state according to the embodiment.
[0033] FIG. 18 is a flowchart exemplifying a communication terminal
function according to the embodiment.
DESCRIPTION OF THE EMBODIMENTS
[0034] The embodiment of the present invention will now be
described while referring to the drawings.
[0035] FIG. 1 is a diagram showing a radio network expansion method
according to the embodiment of the present invention. A
communication terminal 105 is located in a supervisory hub 100, and
a supervisory target 104 is located outside the radio transmission
range (the communication range) of the communication terminal 105.
A relay terminal 101 is located between the supervisory hub 100 and
the supervisory target 104, and within the radio transmission range
(the communication range) of the communication terminal 105, and a
relay terminal 102 is located between the supervisory target 104
and the relay terminal 101 and within the radio transmission range
of the communication terminal 101. A supervisory person 106, having
a communication terminal 103, is located where he or she can
communicate with the relay terminal 102. Communication between the
communication terminal 105 and the relay terminal 101 is indicated
by an arrow 107, communication between the relay terminal 101 and
the relay terminal 102 is indicted by an arrow 108, and
communication between the relay terminal 102 and the communication
terminal 103 (supervisory person 106) is indicated by an arrow
109.
[0036] Hereinafter, when communication terminals and relay
terminals are not specified, they are referred to simply as
terminals.
[0037] The method of the embodiment for arranging the relay
terminal will now be described.
[0038] When an abnormality occurs at the supervisory target 104,
the supervisory person 106 is supposed to be dispatched from the
supervisory hub 100 to examine the abnormality. However, since the
supervisory target 104 is outside the radio transmission range of
the communication terminal 105, which is located in the supervisory
hub 100, upon arriving at the supervisory target 104, the
supervisory person 106 could not employ the communication terminal
103 to communicate with the communication terminal 105.
[0039] Therefore, upon departing the supervisory hub 100, the
supervisory person 106 carries the relay terminal 101, the relay
terminal 102 and the communication terminal 103. When the
supervisory person 106 arrives at a location, distant from the
supervisory hub 100, where the quality of the radio communication
with the communication terminal 105 reaches a predetermined
reference level, the arrangement of the relay terminal 101 is
requested of and is performed by the supervisory person 106.
[0040] Similarly, when the supervisory person 106 arrives at a
location, distant from the relay terminal 101, where the quality of
communication with the relay terminal 101 reaches the reference
level, the arrangement of the relay terminal 102 is requested of
and is performed by the supervisory person 106. In this manner, the
radio network is extended for the communication terminal 105 and
the communication terminal 103 carried by the supervisory person
106.
[0041] To establish the radio communication route for the expansion
of the radio network, a route control method, the standardization
of which has been discussed by the IETF (Internet Engineering Task
Force), can be employed for a mobile ad hoc network. In this
embodiment, it is assumed that route control software is supplied
for the terminals and is employed for route control.
[0042] Initially, the route control software for the communication
terminal 105 is activated, while the route control software for
each of the relay terminals 101 and 102 is activated once the
terminal has been arranged. A communication route is then provided
when a communication request from one of the communication
terminals is received.
[0043] A redundancy may be provided for a radio network so that
when a malfunction occurs, due to a failure at or the destruction
of a relay terminal, or a shortage of batteries, the cutting off of
the radio network can be prevented. In this case, each relay
terminal may have a function for so arranging itself that it can be
connected to at least two other terminals.
[0044] While referring to FIG. 2, an explanation will be given for
a method for determining an appropriate location for the
arrangement of a relay terminal. The quality of the communication
with the terminal 101 is shown in FIG. 2. Circles 201 and 200 are
used to describe the communication quality boundaries: within the
inner circle 201, the communication quality is high; in the area
delimited by the circle 200 and the circle 201, the communication
quality is intermediate; and beyond the outer circle 200, either
the communication quality is low or the range for radio
communication is exceeded.
[0045] The communication quality is measured as an electric field
relative to the terminal 101, or a signal-to-noise ratio, and a
reference value indicating a border is determined in advance. When
the supervisory person 106 carrying the relay terminal 102 enters
the range delimited by the circles 201 and 200, wherein the radio
communication quality is "intermediate", it is determined that the
location is appropriate for the relay terminal 102.
[0046] While referring to FIG. 3, an explanation will be given for
a method for determining a location, appropriate for the relay
terminal 103, whereat communication with at least two terminals is
possible. Circles 202 and 203 describe the boundaries for the
quality of communication with the terminal 102. When the
supervisory person 106 carrying the relay terminal 103 enters an
area defined by the circles 200 and 203 and excluding areas
delimited by the circles 201 and 202, i.e., enters an area in which
the quality of communication, with two or more terminals, is
"intermediate", but that excludes areas in which the quality of
communication, with two or more terminals, is "high", it is
determined that the relay terminal 103 is appropriately located for
communicating with the two relay terminals 101 and 102 at
least.
[0047] An explanation will now be given for a relay terminal.
First, an example configuration for a relay terminal will be
described while referring to FIG. 16. A relay terminal F10 includes
a CPU F01, a memory F02, a timer F00, a radio communication unit
F95, a light emission controller F04, an audio controller F06 and a
switch F08. An antenna F09 is connected to the radio communication
unit F05, a light-emitting unit F03 is connected to the light
emission controller F04, and a loudspeaker F07 is connected to the
audio controller F06.
[0048] The antenna F09 is used by the relay terminal F10 to relay
packets. The light-emitting unit F03 in this embodiment can emit
light in four colors and can turn light on or blink it, and can
change the blinking speed. Sounds can be produced by the
loudspeaker F07.
[0049] The relay terminal F10 has three functions: a terminal
arrangement support function G00, used for the arrangement of the
relay terminal; a relay function G01, for relaying a packet after
the relay terminal has been arranged; and a terminal collection
support function G02, for retrieving the arranged terminal.
[0050] The relay terminal F10 selectively performs one of the three
functions. The functions can be changed by depressing the switch
F08, as is shown in FIG. 17. In this embodiment, the terminal
arrangement support function G00, the relay function G01 and the
terminal retrieval function G02 of the relay terminal F10 are
sequentially altered by depressing the switch F08. The currently
selected relay terminal F10 function can be identified from the
color of the light emitted by the light-emitting unit F03.
[0051] Various lists, which will be described later, and the ID of
a terminal at a communication object are stored in the memory F02.
The timer F00 measures a wait time for determining a time-out for
each packet, which will be described later. A corresponding wait
time is registered in advance for each type of packet.
[0052] The functions explained in this embodiment are performed
when the CPU F01 of a terminal executes programs stored in the
memory F02. At least part of each function may be performed by
hardware.
[0053] The programs may be stored in the memory F02 in advance, or
may be downloaded to the memory F02, as needed, from a detachable
recording medium or a communication medium (a communication network
including a radio network or a carrier along a communication
network) that can be accessed by the terminal.
[0054] The terminal arrangement support function of the relay
terminal will be explained while referring to the flowcharts in
FIGS. 4 and 5 showing the terminal arrangement support function. A
communication object terminal (hereinafter referred to as an object
terminal), which is the starting point for the expansion of a radio
network, is registered with a relay terminal (e.g., 101) that has
been shifted to the terminal arrangement support state. The object
terminal in this embodiment is the communication terminal 105 in
FIG. 1.
[0055] The relay terminal 101, which is in the terminal arrangement
support state, performs the object terminal entry acceptance
process (300). The object terminal may be designated in advance for
the relay terminal 101.
[0056] The object terminal entry acceptance process (300) is shown
in the flowchart in FIG. 6.
[0057] The relay terminal 101 performs a process (400) to determine
whether the object terminal has been registered. When the object
terminal has been registered, the relay terminal 101 advances to
the next process without performing any intervening processes. When
the object terminal has not been registered, the red lighting
process (401), for example, is performed to indicate that the relay
terminal 101 is in the terminal arrangement support state and that
the object terminal has not yet been registered. In order to
register the object terminal, the relay terminal 101 performs a
survey packet transmission process (402). In this case, survey
packets are broadcast to all the terminals within the radio
communication range of the relay terminal 101.
[0058] The format for a survey packet is as shown in FIG. 7.
[0059] The format includes a packet type 500, an object terminal ID
501 and the ID 502 of the relay terminal 101 at the packet
transmission source. A special ID (e.g., 0) is entered for an
object terminal so that the object terminal for the relay terminal
101 is not yet registered. When the timer F00 is started following
the transmission of a survey packet and a wait time has elapsed, it
is assumed that a response packet has not been received and program
control returns to the survey packet transmission process (402).
When a response packet is received within the wait time, the object
terminal is registered, and the light-emitting unit F03 performs a
process (404) for changing from the red to a second light color,
such as green.
[0060] The supervisory person 106 confirms that the color of the
light emitted by the light-emitting unit F03 has been changed from
red to green, and goes toward the supervisory target 104.
[0061] Next, the survey packet transmission process (301) is
performed to determine the location.
[0062] A check is performed to determine whether a response to the
survey packet has been received within a wait time. When no
response has been received (no at 302), a blinking red light is
emitted (304), indicating that communication with the object
terminal is disabled. Program control thereafter returns to the
survey packet transmission process (301). At this time, since
communication with the object terminal 105 is disabled, the
supervisory person 106 begins to return to the supervisory hub
100.
[0063] A warning sound may be produced when a light is blinking.
When a response is received (yes at 302), the signal intensity of
the response packet is measured, the communication quality level is
determined based on a reference value defined in advance, and the
communication quality level and the response source ID are entered
in an accessible relay terminal list (303).
[0064] In this embodiment, two reference values are designated.
Communication quality L1 is defined as being higher than a
reference value indicated by the circle 201 in FIG. 2;
communication quality L2 is defined as being lower than the
reference value indicated by the circle 201 and higher than a
reference value indicated by the circle 200; and communication
quality L3 is defined for all other cases. Instead of the signal
intensity, a signal-to-noise ratio may be employed as the reference
for the communication quality.
[0065] An example accessible relay terminal list is shown in FIG.
8. In this embodiment, when the location of the supervisory person
106 is between the relay terminals 101 and 102, as is shown in FIG.
3, the ID of the relay terminal 101 is registered in a block 700,
the quality of communication with the relay terminal 101 is
registered in a block 705, the ID of the relay terminal 102 is
registered in a block 701, and the quality of communication with
the relay terminal 102 is registered in a block 706. Further, on
the accessible relay terminal list, the ID of the terminal that has
received a response is registered in a column 703, and the quality
of communication with this terminal is registered in a column 704,
aligned with the ID column 703.
[0066] The process for determining whether the location of the
terminal is appropriate will now be explained while referring to
FIGS. 1, 4 and 5.
[0067] A check is performed to determine whether a terminal, for
which the communication quality is L2, is registered on the
accessible relay terminal list. When the terminal has not yet been
registered (no at 305), a blinking red light is emitted (304),
indicating that communication with the object terminal is disabled,
and program control returns to the survey packet transmission
process (301). The supervisory person 106 identifies the disable
communication by confirming the red light is blinking, and begins
to return to the supervisory hub 100. When the terminal has been
registered (yes at 305), a check is performed to determine whether
at least two terminals for which the communication quality is L1
are present on the accessible relay terminal list (i.e., whether
the location of the supervisory person 106 is within the range that
is included in both the circles 201 and 202 of the relay terminals
101 and 102 in FIG. 3). When at least two terminals are present
(yes at 306), program control returns to the survey packet
transmission process (301). So long as the second color light is
blinking, the supervisory person 106 continues to advance toward
the supervisory target 104.
[0068] When two terminals for which the communication quality is L1
are not present (no at 306), a check is performed to determine
whether only one terminal having a communication quality of L2 or
higher is on the accessible relay terminal list. When there is only
one terminal (e.g., only the relay terminal 102 in FIG. 1) (yes at
307), a check is performed to determine whether the communication
quality level of the terminal is L1 or L2 (310). When the
communication quality is L2, the second color light, i.e., a green
light, is blinked at (309), and program control returns to the
survey packet transmission process (301). When the communication
quality is L1, the green light blinks slower than it does at (309)
(311).
[0069] When no terminal has a communication quality of L2 or higher
(no at 307), the green light blinks slower than it does at (311)
(308), and program control returns to the survey packet
transmission process (301). During the processes 309 and 308, a
warning sound may be intermittently generated at the same speed as
that at which the light is blinking.
[0070] In order to prevent communication from being cut off due to
the failure of a relay terminal, when the supervisory person 106
desires to arrange a relay terminal at a location accessible by at
least two terminals, as shown in FIG. 3, the supervisory person 106
advances toward the supervisory target 104, and arranges the relay
terminal 103 when the green light begins to blink slower during the
process (308). Or when the supervisory person 106 desires to
arrange a relay terminal at a location accessible by at least one
terminal, as is shown in FIG. 1, the supervisory person 106
advances toward the supervisory target 104 until the green light
starts blinking during the process (309), and arranges the relay
terminal 103 when the green light starts blinking during the
process (309). For this arrangement, the relay terminal 103 is set
to the relay state by depressing the switch F08. The supervisory
person 106 also employs this process when arranging the relay
terminals.
[0071] The relay function G01 of the relay terminal will now be
described while referring to FIG. 9. FIG. 9 is an example flowchart
showing the relay function G01 of a relay terminal.
[0072] The relay terminal 101, which is in the relay state, starts
the route control software for controlling a communication route,
and permits the light-emitting unit F03 to emit a light having a
third color, such as blue (800). When a survey packet or a
collection packet, which will be described later, is received (yes
at 801), a check is performed to determine whether the received
packet is a survey packet or a retrieval packet (802). When a
retrieval packet is received, a blue light begins to blink (804).
At the same time, sounds may also be generated. Then, a retrieval
response packet is transmitted.
[0073] The format of a retrieval response packet is shown in FIG.
11. This format includes a packet type A00 and the ID A01 of a
packet transmission source.
[0074] When the packet received in the process 802 is a survey
packet, the ID of the object terminal 105 included in the survey
packet is examined to determine whether the object terminal 105 is
accessible using a ping packet (803). When the object terminal 105
is accessible (yes at 805), an accessible response is transmitted
(806). When the object terminal 105 is not accessible (no at 805),
program control returns to the process (801) where it waits for the
next packet. During the determination process 803, a routing table
may be examined to determine whether the object terminal 105 is
registered.
[0075] The format of a survey response packet is shown in FIG. 10.
This format includes a packet type 900, the ID 901 of the object
terminal 105 and the ID 902 of the transmission source 101. When
the relay terminal is shifted to a state other than the relay
state, execution of the route control software is halted,
terminating the route control process.
[0076] The terminal retrieval support function of the relay
terminal will now be described. An example retrieval process is
shown in FIG. 12. When the supervisory person 106 retrieves the
relay terminals 101 and 102 that have been arranged, the relay
terminal 103 is set to the terminal retrieval support state to
notify the supervisory person 106 that the terminals are present,
so that the retrieval of the relay terminals can be supported.
[0077] FIG. 13 is an example flowchart for the terminal retrieval
support function. When the relay terminal 103 is set to the
terminal retrieval support state, the relay terminal 103 permits
the light-emitting unit F03 to emit a light having a fourth color,
such as yellow (C00). Then, a collection packet is transmitted
(C01), and when a response to this packet is not received (no at
C02), program control returns to the retrieval packet transmission
process (C01).
[0078] When a response is received (yes at C02), the signal
intensity of the response packet is measured, the communication
quality level is determined, and the response source ID and the
communication quality level are entered in a retrieved terminal
list (C03). Instead of the signal intensity, a signal-to-noise
ratio may be employed as the communication quality. Further, the
same reference as in the process 303, or another reference value,
may be employed to determine the communication quality level.
Furthermore, the fourth color light, i.e., the yellow light, blinks
at the speed that is consonant with the terminal that is registered
on the collected terminal list and that has the highest
communication quality level (C04). In this embodiment, since three
communication quality levels, L1, L2 and L3, are provided, a high
blinking speed may be set for the communication quality L1, an
intermediate speed may be set for the communication quality L2 and
a low speed may be set for the communication quality L3. In
addition, instead of, or at the same time as the blinking of light,
sounds may be generated. At this time, the pitch and the volume of
a tone may be changed in accordance with the communication quality
level.
[0079] An example format for the retrieval packet is shown in FIG.
14. This format includes a packet type D00 and the ID D01 of a
packet transmission source. An example retrieved terminal list is
shown in FIG. 15. In this embodiment, the ID of the terminal 101 is
entered in a block E00; the quality of the communication with the
terminal 101 is entered in a block E05; the ID of the terminal 102
is entered in a block E01; and the quality of the communication
with the terminal 102 is entered in a block E06. Further, in the
retrieved terminal list, the ID of a retrieved terminal is entered
in a column E03, and the quality of the communication with the
retrieved terminal is entered in a column E04 aligned with the ID
column E03.
[0080] The supervisory person 106 in charge of the retrieval of
relay terminals confirms that a light is blinking on his or her
relay terminal 103, which is in the terminal retrieval support
state, and from this can ascertain that the terminal 101 or 102 to
be retrieved is located nearby. At this time, since it can be
determined that the relay terminal 101 or 102 is located nearby
when the communication quality level is high, the distance to the
relay terminal can be estimated when the light is blinking rapidly.
And after the supervisory person 106 enters the radio communication
range and a light on the relay terminal 101 or 102 blinks or sounds
are generated through the process 804 in FIG. 9, the supervisory
person 106, using the light or the sounds, and easily divine the
location of the relay terminal 101 or 102.
[0081] An example flowchart for the communication terminal 105 is
shown in FIG. 18. When a survey packet is received via the relay
terminal (e.g., 101) (yes at H00), a check is performed to
determine whether the object terminal ID 901 included in the survey
packet has not yet been registered. When the object terminal ID 901
has not yet been registered (no at H01), the ID of the
communication terminal (e.g., 105) is entered as the object
terminal ID 901 for the survey packet to indicate that the
pertinent communication terminal is an object terminal, the
response is transmitted to the relay terminal 101 (H03), and the
arrival of the next packet is waited for.
[0082] When the object terminal indicated by the survey packet
matches the communication terminal 105 (yes at H01), a response
indicating that it is accessible is returned (H02), and the arrival
of the next packet is waited for. The format of the survey response
packet is as shown in FIG. 10.
[0083] According to this embodiment, for the expansion of a radio
network, the relay terminals can be arranged without a radio status
survey being performed.
[0084] Further, for the retrieval of arranged relay terminals, the
presence of peripheral relay terminals can be detected.
[0085] Furthermore, since the arrangement support function, the
relay function for communications with a communication terminal,
and the retrieval support function can be switched, a single
terminal can perform the arrangement support function, the relay
function and the retrieval support function.
[0086] The use of colors and the manner in which blinking lights
are employed in this embodiment are merely examples, and other ways
may be employed so long as the individual states can be identified.
Further, means other than light and sounds may be employed.
[0087] The specification and drawings are, accordingly, to be
regarded in an illustrative rather than a restrictive sense. It
will, however, be evident that various modifications and changes
may be made thereto without departing from the spirit and scope of
the invention as set forth in the claims.
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