Location based vehicle multihop protocol unicast apparatus and routing method using the apparatus

12 Pages·2013·0.93 MB·English

US008570930B2
(12) Ulllted States Patent (10) Patent N0.: US 8,570,930 B2
Kim et al. (45) Date of Patent: Oct. 29, 2013
(54) LOCATION BASED VEHICLE MULTIHOP (58) Field of Classi?cation Search
PROTOCOL UNICAST APPARATUS AND USPC ........ .. 370/313, 338, 395.21; 455/414.1, 428,
ROUTING METHOD USING THE 455/556~1
APPARATUS See application ?le for complete search history.
(75) Inventors: Min Jung Kim, Daejeon (KR); (56) References Clted
Sangwoo Lee, Daejeon (KR); Hyun U.S. PATENT DOCUMENTS
Kyun Choi, Daejeon (KR); Han Byeog
Cho, Daejeon (KR); Hyun S90 ()h, 2008/0186869 A1 8/2008 Jeon et a1.
Daejeon (KR)
FOREIGN PATENT DOCUMENTS
(73) Assignee: Electronics and Telecommunications
. - KR 10-0810662 7/2008
Research Institute, Daejeon (KR) KR l 0_2009_0054163 5/2009
( * ) Notice: Subject to any disclaimer, the term of this OTHER PUBLICATIONS
gage? 11S sizfgltdeg 1O8r didjsusted under 35 Valery Naumov et 211., “Connectivity-Aware Routing (CAR)in
' ' ' y y ' Vehicular Ad-Hoc Networks”, INFOCOM’07, 2007.
(21) Appl' N05 12/949,362 Primary Examiner * Yemane Mes?n
. Assistant Examiner * Wanda Z Russell
22 Fld: N .18 2010
( ) 1 e 0V ’ (74) Attorney, Agent, or Firm * Staas & Halsey LLP
(65) Prior Publication Data (57) ABSTRACT
Us 2011/0134840 A1 11111- 9, 2011 In order for a source node including a Vehicle multihop pro
_ _ _ _ _ tocol unicast apparatus to route data to a destination node, the
(30) Forelgn Apphcatlon Pnonty Data source node broadcasts a location request message to neigh
bor node and receives a location response message from the
Dec. 8, 2009 (KR) ...................... .. 10-2009-0121379 neighbornodesinresponseto thelocationrequestmessage'
Mar‘ 9’ 2010 (KR) """"""""""" " 10'2010'0020962 Therefore, the source node routes unicast data on the basis of
the location information of the destination node included in
(51) Int. Cl. the locat.l on response message. At th1. s t.l me, the source node
(52) HU0 54 QC l7 /00 (2006.01) uses a locat.l on based forwarder select.i ng algor.i thm i. n order
‘ ‘ ‘ t l t f d .
USPC 370/313; 370/338; 370/395.31; 455/404.2; 0 Se e0 a Omar er
455/428 13 Claims, 5 Drawing Sheets
First neighbor Second neighbor Destination
some node node node node
Generate location
request message T5100
Broadcast location /5110
request messageL 5115
Broadcast location request message /
Broadcast location 5120
request message
Transfer location /S130
response message
5140
Transfer location response message)
S150
Transferunicastdata /
Transfer unicast
data \
S160
US. Patent 0a. 29, 2013 Sheet 1 of5 US 8,570,930 B2
FIG.1
AD
uni-1n Int-In:
____________ ____ __________
’C ,,
_ __ _ _ _ [I] __m _1_] — ml 1 _________ — a
S I
/
I
US. Patent 0a. 29, 2013 Sheet 2 of5 US 8,570,930 B2
6w6ec
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US. Patent
Oct. 29, 2013 Sheet 3 0f 5 US 8,570,930 B2
FIG.3
First neighbor Second neighbor Destination
Source node
node node node
Generate location
request message ~S100
Broadcast location‘
/s11o
request messageC
5115
Broadcast location request message
Broadcast location S120
request messagei
Transfer location S130
‘response message
S140
Transfer location response message)
S150
Transfer unicast data 2
Transfer unicast
data
5160
US. Patent
Oct. 29, 2013 Sheet 4 0f 5 US 8,570,930 B2
FIG.4
Generate and broadcast hello
message “5200
ll
Acquire second node information ~5210
l
Identify coordinator ~5220
i
Calculate traffic state index ~5230
l
Transmit hello message @5240
US. Patent 0a. 29, 2013 Sheet 5 of5 US 8,570,930 B2
FIG.5
Receive location re uest
message q “5300
Generate location res onse
message p “5340
ll
Select forwarder ~S350
S320
Broadcast after the maximum Does Source ID ex''s t'v
allowable number of ~S33O
multlhops decreases No
Select forwarder based on
v 5370” location
End _ r _
5380f Transmrt locatlon response <
message
US 8,570,930 B2
1 2
LOCATION BASED VEHICLE MULTIHOP An exemplary embodiment of the present invention pro
PROTOCOL UNICAST APPARATUS AND vides a VMP-unicast apparatus that includes:
ROUTING METHOD USING THE a message processing unit extracting ?rst node information
APPARATUS on at least one neighbor node by broadcasting a hello mes sage
to the neighbor node, and generating and transmitting a uni
CROSS-REFERENCE TO RELATED cast message on the basis of the ?rst node information; a
APPLICATION location information processing unit receiving location infor
mation data on a node and verifying second node information
This application claims priority to and the bene?t of of the node included in the location information data; a
Korean Patent Application Nos. 10-2009-0121379 and vehicle location processing unit storing the second node
10-2010-0020962 ?led in the Korean Intellectual Property information received from the location information process
O?ice on Dec. 8, 2009 and Mar. 9, 2010, the entire contents of ing unit, verifying the location of a destination node to which
which are incorporated herein by reference. the unicast message will be transmitted, and routing the uni
cast message; and a forwarder selecting unit verifying a loca
BACKGROUND OF THE INVENTION tion of a destination node, transferring a location response
message to a source node by unicast based on the ?rst node
(a) Field of the Invention information, and selecting a forwarder to forward a packet.
The present invention relates to a location based vehicle Another embodiment of the present invention provides a
multihop protocol (VMP)-unicast apparatus for two vehicles 20 method in which a source node including a VMP-unicast
out of a communication Zone to perform a unicast communi apparatus routes data to a destination node that includes:
cation by using a multihop routing function in a vehicular allowing the source node to broadcast a location request
ad-hoc network (VANET) and a routing method using the (LREQ) message to neighbor nodes; receiving a location
apparatus. response (LRES) message in response to the location request
(b) Description of the Related Art 25 message from the neighbor nodes and verifying location
Topology is rapidly changed in a communication environ information of the destination node included in the location
ment between vehicles unlike a network environment. There response message; and routing unicast data on the basis of the
fore, it is di?icult to consistently maintain a routing path up to location information of the destination node.
a destination of the vehicle. As a result, a node to which data
will be forwarded is should be designated according to the 30 BRIEF DESCRIPTION OF THE DRAWINGS
situation on the basis of location information of the destina
tion. FIG. 1 is an exemplary diagram setting a routing path in
Greedy perimeter stateless routing (GPSR) is generally vehicle unicast multihop communication according to an
used among unicast routing algorithms based on the location exemplary embodiment of the present invention;
information. The GPSR is a routing algorithm in which 35 FIG. 2 is a block diagram of an apparatus for a vehicle
assumed that the location of the destination node is known, a multihop protocol unicast according to an exemplary
node among nodes in the communication Zone, which is close embodiment of the present invention;
to the destination node is selected and a packet is forwarded to FIG. 3 is a ?owchart of message processing in vehicle
the selected node. unicast multihop communication according to an exemplary
The GPSR may be smoothly operated under a condition 40 embodiment of the present invention;
without an obstacle like an expressway. However, when the FIG. 4 is a ?owchart showing a procedure of generating
node close to the destination node is just selected as the hello messages exchanged between nodes according to an
forwarding node in the state in which communication is exemplary embodiment of the present invention; and
invalid due to surrounding buildings like an urban environ FIG. 5 is a ?owchart of ?nding the location of a destination
ment, the packet may not be transferred to the destination. 45 node according to an exemplary embodiment of the present
Greedy perimeter coordinator routing (GPCR) is a routing invention.
algorithm developed to overcome the problem of the GPSR.
When a node at an intersection is set as a coordinator and the DETAILED DESCRIPTION OF THE
packet is forwarded to the coordinator, the packet may be EMBODIMENTS
transferred to the destination even though a line of sight 50
(LOS) is not secured due to the building like an urban. In the following detailed description, only certain exem
However, in the case of the GPCR, when the nodes at an plary embodiments of the present invention have been shown
intersection are selected as the coordinator, tra?ics are con and described, simply by way of illustration. As those skilled
centrated on the nodes, such that the packet may not be in the art would realiZe, the described embodiments may be
normally transferred. 55 modi?ed in various different ways, all without departing from
The above information disclosed in this Background sec the spirit or scope of the present invention. Accordingly, the
tion is only for enhancement of understanding of the back drawings and description are to be regarded as illustrative in
ground of the invention and therefore it may contain infor nature and not restrictive. Like reference numerals designate
mation that does not form the prior art that is already known like elements throughout the speci?cation.
in this country to a person of ordinary skill in the art. 60 In the speci?cation, unless explicitly described to the con
trary, the word “comprise” and variations such as “com
SUMMARY OF THE INVENTION prises” or “comprising”, will be understood to imply the
inclusion of stated elements but not the exclusion of any other
The present invention has been made in an effort to provide elements.
a location based vehicle multihop protocol (V MP) unicast 65 Hereinafter, a location based VMP-unicast routing method
apparatus adoptable in an expressway and an urban environ will be described with reference to the accompanying draw
ment, and a routing method using the apparatus. 1ngs.
US 8,570,930 B2
3 4
FIG. 1 is an exemplary diagram setting a routing path in data, etc. included in the location information data. The veri
vehicle unicast multihop communication according to an ?ed second node information is transferred to and stored in
exemplary embodiment of the present invention. the vehicle location database 111. Although GPS data is used
As shown in FIG. 1, a location based vehicle multihop as the location information data in the embodiment of the
protocol unicast (hereinafter, for convenience of description, present invention, the GPS data is not necessarily limited
referred to as “VMP-unicast”) routing algorithm ?nds a cur thereto.
rent location of a vehicle destination and determines a for When the vehicle location processor 112 receives the uni
warder that will forward data by using a location based for
cast message to be transmitted to the destination node, which
ward selecting module up to the current location to transfer
is generated by the unicast message processor 152, the
the data up to a ?nal destination.
vehicle location processor 112 searches whether or not the
A coordinatorpositioned at an intersection is preferentially
?rst node information of the destination node is stored in the
considered in selecting the forwarder. When a plurality of
neighbor table stored in the neighbor table database 121 in
coordinators are present, the forwarder is selected consider
order to ?nd the location of the destination node before trans
ing directions of the coordinators, current communication
mitting the unicast message.
traf?cs of the coordinators, etc. On the contrary, when no
If the destination node to which the unicast message will be
coordinator is present, a node closest to a destination is
selected as the forwarder. This may be applied to a condition transmitted is not stored in the neighbor table database 121,
that is, if the destination node is not a neighbor node of a
such as an expressway.
Next, the structure of an apparatus installed in a vehicle for source node, a location request (LREQ) message for ?nding
the VMP-unicast described in FIG. 1 will be described with 20 the current location of the destination node on the basis of the
reference to FIG. 2. ID of the destination node is generated and broadcasted to the
FIG. 2 is a block diagram of an apparatus for a VMP adjacent node.
unicast according to an exemplary embodiment of the present However, if the destination node is stored in the neighbor
invention. table database 121, that is, the destination node is the neigh
As shown in FIG. 2, the VMP-unicast apparatus 100 25 bor node of the source node, the unicast message is transmit
includes a vehicle location processing unit 110, a neighbor ted. The neighbor node receiving the unicast message com
management unit 120, a coordinator identifying unit 130, a pares its own ID with the ID of the destination node included
forwarder selecting unit 140, a message processing unit 150, in the unicast message.
and a location information processing unit 160. In addition, when its own ID does not coincide with the ID
The vehicle location processing unit 110 includes a vehicle 30 of the destination node, the unicast message is broadcasted to
location database 111 and a vehicle location processor 112, the neighbor node again. However, when its own ID coincides
and receives location information data and veri?es second with the ID of the destination node, a node receiving the
node information included in the location information data. LREQ message becomes the destination node, such that the
The message processing unit 150 includes a hello message neighbor node transfers a location response message includ
processor 151 and a unicast message processor 152, and 35 ing its own location information to the source node to notify
extracts node information by broadcasting a hello message to its current location.
adjacent nodes and generates and transmits a unicast message The vehicle location database 111 stores ?rst node infor
on the basis of the node information. In addition, the neighbor mation of the adjacent node received from the vehicle loca
management unit 120 includes a neighbor table database 121 tion processor 112 or second node information received from
and a neighbor table manager 122, and stores and manages 40 the location information processing unit 160.
node information on adjacent nodes. When the forwarder selecting unit 140 veri?es the location
First, the hello message processor 151 of the message of the destination node through the location response mes
processing unit 150 broadcasts the hello message to the adja sage, the forwarder selecting unit 140 receives the ?rst node
cent nodes at a predetermined cycle. In addition, the hello information of the destination node from the neighbor table
message processor 151 extracts ?rst node information includ 45 database 121 and transfers the location response message to
ing current node location information, current speed informa the source node by the unicast. In addition, the forwarder
tion, etc. of the adjacent nodes from a response message for selecting unit 140 selects a forwarder to which a packet will
the hello message received from the adjacent nodes. A frame be forwarded among neighbor nodes recogniZed as the coor
structure of the hello message and information included in the dinator. Herein, a method of selecting the forwarder will now
hello message will be described afterwards. 50 be described.
The unicast message processor 152 generates and trans The coordinator identifying unit 130 judges whether or not
mits a unicast message for transferring data up to an actual it corresponds to the coordinator node on the basis of the
destination node on the basis of ?rst node information of the current location of the vehicle. A forwarder selecting algo
adjacent nodes, which is stored in the neighbor table database rithm is performed in order to judge to correspond to the
121 when the location of the destination node is determined. 55 coordinator and it will be described afterwards.
The unicast message includes an ID of the destination node A method of supporting the VMP-unicast through the
and location information of the destination node. above-mentioned apparatus will be described with reference
The neighbor table database 121 constitutes a neighbor to FIG. 3. In the embodiment of the present invention, for
table by the ?rst node information of the adjacent nodes convenience of description, a node transmitting unicast data
included in the hello message received by the hello message 60 is referred to as the source node and a node receiving unicast
processor 151. The neighbor table manager 122 controls to data is referred to as the destination node. In addition, a
periodically update the neighbor table database 121. neighbor node receiving the message broadcasted from the
The location information processing unit 160 receives source node in order to ?nd the destination node is referred to
location information data from the outside through an inter as a ?rst neighbor node and a second neighbor node.
face and veri?es the second node information on a current a 65 FIG. 3 is a ?owchart of message processing in vehicle
current node location, a vehicle speed, a vehicle moving unicast multihop communication according to an exemplary
direction, a current time receiving the location information embodiment of the present invention.
US 8,570,930 B2
5 6
As shown in FIG. 3, it is assumed that a source node Since the hello message is generated and broadcasted at a
previously knows an ID of a destination node for transferring predetermined cycle, the hello message may be generated and
a message to the destination node by the unicast. In addition, broadcasted while the message is processed in the vehicle
when node information on the destination node is stored in a unicast multihop communication described in FIG. 3 or
neighbor table database 121, the destination node is within a
before the message is generated or after the message is pro
communication range of the source node. In this case, the
cessed. First, a hello message generation procedure will be
source node directly transmits data to the destination node.
described with reference to FIG. 4.
However, when the node information on the destination
node is not stored in the neighbor table database 121, a vehicle FIG. 4 is a ?owchart showing a procedure of generating
location processor 112 generates a location request (LREQ) hello messages exchanged between nodes according to an
exemplary embodiment of the present invention.
message in order to ?nd the location of the destination node
on the basis of the already known ID of the destination node As shown in FIG. 4, the hello message processor 151
(S100). In addition, the generated LREQ message is broad generates the hello message and broadcasts the generated
hello message to neighbor nodes (S200). At this time, the
casted to neighbor nodes (S110 and S115). Herein, the LREQ
hello message processor 151 acquires second node informa
message includes the ID of the destination node, the location
tion in order to broadcast the hello message including the
information of the source node, and sequence number infor
second node information such as a current location, speed,
mation.
direction, time information, and node’s own ID information
A ?rst neighbor node and a second neighbor node that
20 that are included in GPS information received by the location
receive the LREQ message verify the ID of the destination information processing unit 160 (S210). Herein, a message
node included in the LREQ message and compare their own frame of the hello message is shown in Table 1.
IDs with the ID of the destination node. If the ?rst neighbor
node or the second neighbor node, which receives the LREQ TABLE 1
25
message, itself is not the destination node, it is veri?ed
Control Source Time Loca- Speed Direc- Coordi- Traf?c
whether or not the ?rst node information of the destination type node stamp tion tion nator state
node is stored in the neighbor table database 121 and when the ID index
?rst node information is stored in the neighbor table database Time value Description
121, the LREQ message is broadcasted to the neighbor nodes 30
0 Hello
again (S120).
I Multihop broadcast frame
However, if the ?rst node information is not stored in the 2 Single hop broadcast frame
3 Unicast frame
neighbor table database 121, the LREQ message is discarded.
4 Geo broadcast frame
In the embodiment of the present invention, it is assumed that
35
the ?rst node information of the destination node is not stored
In the embodiment of the present invention, the hello mes
in the ?rst neighbor node and the ?rst node information of the
sage including information indicating whether or not the node
destination node is stored in the second neighbor node.
transmitting the hello message is the coordinator node posi
If an ID of another node receiving the LREQ message
tioned at the intersection area is broadcasted. Therefore,
40
coincides with the ID of the destination node, it is veri?ed that through an algorithm identifying whether or not the nodes are
the corresponding node is the destination node. In this case, the coordinator node, it is identi?ed whether or not the nodes
the corresponding node generates a location response (LRES) are the coordinator (S220).
message and includes location information of the current
In addition, the nodes judge their own tra?ic states and
destination node to transfer it to a node broadcasting the 45 include a capability to forward a packet in the hello message
LREQ message (S130). Through such a procedure, the LRES so as to refer to it at the time of selecting the forwarder. For
message is transferred to the source node ?rstly transmitting this, a tra?ic state index is calculated (S230) and the hello
the LREQ message by using the unicast communication to message is transmitted (S240). Therefore, it is possible to
notify the destination node’s own location (S140). prevent tra?ic for a forwarding packet from being increased
50
When the source node transmitting the LREQ message in a predetermined coordinator. Herein, a method of calcu
receives the LRES message, the source node knows the cur lating the traf?c state index has been already known and thus,
rent location of the destination node. In addition, unicast data will not be described in detail in the embodiment of the
is transmitted based on the location information of the desti present invention.
nation node (S150). At this time, when a forwarder selecting 55 Meanwhile, the coordinator identifying algorithm
unit 140 selects a forwarder which is a node forwarding data, executed at step S220 may be variously present and for
the unicast data is transferred to the corresponding forwarder example, when the hello message is received from three or
and ?nally, data reaches the destination node which is the more directions based on directions of the nodes in the neigh
destination (S160). bor table, the node receiving the hello message may set itself
Next, a method for the forwarder selecting unit 140 to 60 as the coordinator. Alternately, the node may be set as the
coordinator by the tra?ic state index’ s counting the number of
generate a hello message exchanged between nodes where a
currently transmitted and received messages and the node
hello message processing 151 is present in a communication
may be set as the coordinator on the basis of the number of
radius and select the forwarder in order to collect node infor data of a currently occupying queue. In the embodiment of the
mation of a node, in particular, to identify a coordinator node 65 present invention, the algorithm to set the node as the coor
positioned at an area such as an intersection area will be dinator is not limited to any one algorithm. In addition, the
described. neighbor table is shown in Table 2.
US 8,570,930 B2
7 8
TABLE 2
Source node ID Time stamp Location Speed Direction Coordinator TCI valid
123xxxx . .. Sep. 5, 2012 29.12736, 30 N C High Y
12:13:05 130.18263
000xxxx . .. Sep. 5, 2012 29.12736, 40 E N Low Y
12:13:30 130.18264
Next, a method for neighbor nodes receiving the LREQ 10 -Continued
message to ?nd the location of the destination node and
transmit the LRES message will be described with reference If (C%:m==1) then FID =. CID .
(number of Coordinator is more than 1)
IO FIG. 5. For each coordinator m in NT
FIG. 5 is a ?owchart of ?nding the location of a destination FID = miH(Pi*POS(LOC(IH)-LOC(deS(1D)) + PJ'*TCI(IH))
node according to an exemplary embodiment of the present 15
invention. . . Here1.n , C(N T) represents the number of coord1. nators and
The LREQ message generated by the veh1cle locat1on pro- . .
. . . GPSR(N T) represents greedy per1meter stateless rout1ng
cessor 112 1ncludes the ID of the dest1nat1on node together . . .
. . . . . wh1ch 1s the rout1ng protocol. FID represents the ID of the
w1th 1nformat1on 1nclud1ng the ID of the source node, the . . .
. . . . 20 forwarder, CID 1s the ID of the coord1nator, and P1 represents
locat1on1nformat1on of the source node, the max1mum allow- . . . . .
. a pr1or1ty of locat1on vector d1fference. Further, Pj represents
able number of mult1hops, etc. The LREQ message generated . . . . .
. . a priority of tra?ic cond1t1on1ndex (TCI) and Pos(loc1, loc2)
as above 1s broadcasted to the ne1ghbor nodes. . . .
- - represents locat1on vector d1fference between a ?rst locat1on
When the ne1ghbor node rece1ves the LREQ message d d 1 _
(S300), the neighbor node compares its own ID with the ID of 25 an a Secon Ocanon'
the destination node and judges whether or not the IDs coin- The location based fOrWarder selecting algorithm accord
cide with each other (S310). If two IDs do not coincide with ing to the embodiment of the present invention selects the
each other, the neighbor node judges whether the received node closest to the destination node by using the existing
LREQ message is the already received LREQ message or a GPSR algorithm when the coordinator node is not present in
heWty reeelVed LREQ hlessage ($320) 30 the neighbor table. However, when the number of coordinator
1h Order to Judge 1t, the hede Compares ahd Cheeks nodes is one, the corresponding coordinator node is selected
sequences numbers of the LREQ messages w1th each other. If as the forwarder and the packet is forwarded to the Cone
the received LREQ message is the newly received LREQ Spending Coordinator node_
message, the max1mum allowable number of mult1hops 1s . .
. On the contrary, when a plural1ty of coord1nator nodes are
decreased and thereafter, the message 1s broadcasted to the . .
. . . . 35 present, any one of a node hav1ng the same movement d1rec
ne1ghbor nodes aga1n (S330). However, 1f the rece1ved mes- . . . .
. . . . t1on as the dest1nat1on node or a node hav1ng current low
sage 1s the already rece1ved message, the process 1s term1- . .
. . . traf?c 1s selected as the forwarder and the packet 1s forwarded
nated w1thout broadcast1ng the correspond1ng message to the . .
. to the correspond1ng node. When the LRES message 1s trans
ne1ghbor nodes. .
. . . . . . . ferred up to the source node, the source node can determ1ne
Meanwhile, 1f the ID of the dest1nat1on node co1nc1des w1th . . . . . .
, . . . 40 the locat1on of the dest1nat1on node. In add1t1on, the un1cast
the node s own ID, s1nce the node rece1v1ng the LREQ mes- . .
. . . . message can be transferred up to the dest1nat1on node by
sage 1s the dest1nat1on node, the correspond1ng node gener- . . . .
. . , . perform1ng the locat1on based forwarder select1ng algorithm.
ates an LRES message 1nclud1ng the node s own locat1on _ _ _ _ _ _
(S340). The node generates the LRES message and thereafter, Aeeehhhg t0 ah emhedhheht ofthe Present IhVehtlOh, _1t 15
selects the forwarder in the neighbor table through a location 45 Pesslhte t0 hler e stably transfer a message 1h a eehhhhhlea'
based forwarder Selecting algorithm (S350) tion environment between vehicles in which topology is rap
In addition, the node judges whether or not the ID of the ldly ehahged hy deeehtrahzlhg eeheehtratleh hf fel'wthhg
destination node included in the LRES message, that is, node trafhes Oh a predetenhlhedhede ehtenhg ah 1hter seetleh at
information corresponding to the ID of the forwarder is stored the thhe ef thahsferhhg a hhleast message to hhhtlheps 1h the
in the neighbor table database 121 (S360). If the source node 50 eehhhhhleatleh ehVlrOhIheht hetWeeh the Veh1e1e5~
information is stored, the LRES message is transferred to the The above-mentioned exemplary embodiments of the
forwarder by us1ng the un1cast (S380). When the forwarder present invention are not embodied only by an apparatus and
also receives a message designating itself as the forwarder, method~ Alternatively, the above-mentioned exemplary
the forwarder judges whether or not the node information embodiments may be embodied by a program performing
corresponding to the destination node is stored in the neigh- 55 functions, which correspond to the con?guration of the exem
bor table database 121. plary embodiments of the present invention, or a recording
However, when the node information on the destination medium on which the program is recorded These embodi
node 15 not stored 111 the ne1ghbor table database 121, a Sub- ments can be easily devised from the description of the above
sequent fOrWarder is Selected (S370) and the LRES message mentioned exemplary embodiments by those skilled in the art
is transmitted to the selected forwarder (S380). The location 60 to which the present invention pertains,
based 291mm“ selectmg ?‘lgo_nthni,p?oposed 1n the embodl' While this invention has been described in connection with
mem O t e present lnvemlon Is as 0 0W5‘ what is presently considered to be practical exemplary
embodiments, it is to be understood that the invention is not
limited to the disclosed embodiments, but, on the contrary, is
For each node n in NT 65 intended to cover various modi?cations and equivalent
If (C(NT ==0) then GPSR(NT) arrangements included within the spirit and scope of the
appended claims.