U.S. patent application number 12/547403 was filed with the patent office on 2010-05-06 for method and device for controlling data connections in a data network having a plurality of data network nodes.
Invention is credited to SVEN HISCHKE, Erik Weiss, Bangnan Xu.
Application Number | 20100110919 12/547403 |
Document ID | / |
Family ID | 33494773 |
Filed Date | 2010-05-06 |
United States Patent
Application |
20100110919 |
Kind Code |
A1 |
HISCHKE; SVEN ; et
al. |
May 6, 2010 |
METHOD AND DEVICE FOR CONTROLLING DATA CONNECTIONS IN A DATA
NETWORK HAVING A PLURALITY OF DATA NETWORK NODES
Abstract
A method and a device for controlling data connections in a data
network including a plurality of data network nodes. The quality of
a first data connection is evaluated on the basis of the
adaptations of at least one coding used for the first data
connection, and a second data connection is established according
to the evaluation and used as a replacement for the first data
connection.
Inventors: |
HISCHKE; SVEN; (Troisdorf,
DE) ; Weiss; Erik; (Vaals, NL) ; Xu;
Bangnan; (Darmstadt, DE) |
Correspondence
Address: |
KENYON & KENYON LLP
ONE BROADWAY
NEW YORK
NY
10004
US
|
Family ID: |
33494773 |
Appl. No.: |
12/547403 |
Filed: |
August 25, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10559071 |
Jun 7, 2006 |
7580421 |
|
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PCT/DE04/01037 |
May 17, 2004 |
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12547403 |
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Current U.S.
Class: |
370/252 ;
370/400 |
Current CPC
Class: |
H04L 47/822 20130101;
H04L 47/70 20130101; H04L 47/15 20130101; H04L 47/745 20130101;
H04L 47/824 20130101 |
Class at
Publication: |
370/252 ;
370/400 |
International
Class: |
H04L 12/26 20060101
H04L012/26; H04L 12/56 20060101 H04L012/56 |
Foreign Application Data
Date |
Code |
Application Number |
May 30, 2003 |
DE |
10324470.0 |
Claims
1-18. (canceled)
19. A method for controlling data connections in a data network
having a plurality of data network nodes, comprising: assessing a
quality of a first data connection in the light of an adaptation of
at least one coding used for the first data connection, wherein,
depending on the assessing of the quality of the first data
connection, setting up a second data connection to be used as
replacement for the first data connection.
20. The method as recited in claim 19, wherein the assessment of
the quality of the first data connection is made in that, in the
light of the codings used, at least one first data network node,
participating in the first data connection, makes a statement as to
whether the first data connection is becoming unstable.
21. The method as recited in claim 20, wherein in response to the
statement that the first data connection is becoming unstable, the
at least one first data network node initiates the search for a
second data connection.
22. The method as recited in claim 21, wherein the search is
initiated by sending a first message from the at least one first
data network node to second data network nodes.
23. The method as recited in claim 22, wherein the message is
processed having a different coding than the coding(s) used in the
first data connection.
24. The method as recited in claim 23, wherein the other coding is
a higher coding than the coding(s) used in the first data
connection.
25. The method as recited in claim 19, wherein the second data
connection is utilized when the first data connection is
disconnected.
26. A device for controlling data connections in a data network,
comprising: a plurality of data network nodes; and a first data
connection having a quality, wherein the plurality of data network
nodes which are developed so that the quality of the first data
connection is assessed in view of an adaptation of at least one
coding used for the first data connection, and, depending on the
assessment, a second data connection is set up that is used as
replacement for the first data connection.
27. The device as recited in claim 26, wherein at least one first
data network node, of the plurality of data network nodes,
participating in the first data connection is developed to
undertake the assessment of the quality of the first data
connection in that, in view of the coding used, makes a statement
as to whether the first data connection is becoming unstable.
28. The device as recited in claim 27, wherein the at least one
first data network node may be additionally designed so that, in
response to the statement that the first data connection is
becoming unstable, the at least one first data network node
initiates a search for the second data connection.
29. The device as recited in claim 28, wherein the at least one
first data network node is developed to initiate the search by
sending a first message to at least one second data network
node.
30. The device as recited in claim 29, wherein the first message
includes a number of transmissions, an address of a transmitter,
and an address of a receiver of data of the first data connection,
and wherein the first message has a different coding than the
coding used in the first data connection.
31. The device as recited in claim 30, wherein the different coding
is a higher coding than the coding used in the first data
connection.
32. The device as recited in claim 26, wherein if the first data
connection is threatening to disconnect then a switchover to the
second data connection occurs.
33. The device as recited in claim 26, wherein if a specified
coding is used for the first data connection then a switchover to
the second data connection occurs.
34. The device as recited in claim 26, wherein the data network
includes a radio data network and at least two data network nodes
are radio terminals.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S. patent
application Ser. No. 10/559,071, issuing as U.S. Pat. No.
7,580,421, which was the national stage of PCT/DE2004/001037 filed
on May 17, 2004, which claimed priority to German Patent
Application No. DE 10324470.0 filed on May 30, 2003, each of which
is expressly incorporated herein in its entirety by reference
thereto.
FIELD OF THE INVENTION
[0002] The present invention relates to a method for controlling
data connections in a data network having a plurality of data
network nodes.
BACKGROUND INFORMATION
[0003] In data networks having a plurality of data network nodes, a
data connection takes place from a source to a destination via a
route, link, or path, in the data network which includes a certain
number of data network nodes. In an end-to-end connection in such a
data network, therefore, data packets run from the source to the
destination via a plurality of data network nodes. These data
network nodes work like relay stations.
[0004] In a data network having dynamic or mobile data network
nodes, for example, a radio communications network having mobile
radio terminals as data network nodes, the transmission quality of
a data connection fluctuates as a rule. Such data networks are
expected to gain increasing importance in the future, for example,
because of the wide distribution of wireless LAN networks occurring
in the meantime, and the introduction of UMTS (universal mobile
telecommunications system). Therefore, when working with such data
networks one desires to achieve a high data transmission rate, in
spite of the fluctuating transmission quality.
[0005] In radio communications networks, a distinction is made
between subscriber networks and ad hoc networks. Ad hoc networks
permit a self-organizing organization. Since, the radio range in
radio systems having a high data rate is limited, so-called
multihop data connections are increasingly used in data networks.
For example, in an ad hoc radio communications network, individual
laptop computers may be used as data network nodes which are
provided with a radio interface operated in ad hoc mode. Multihop
data connections are used, above all, when the destination is not
located in the direct radio range of the source. The connection
setup, the connection finding and the restoration of connections
are ensured by special routing protocols.
[0006] As soon as a data connection between a source and a
destination has been found and set up, it may be used for data
transport. Depending on the dynamics of the data network nodes
participating in the data connection, the quality of the data
connection may now change continuously. The data connection may be
interrupted if a data network node participating in the data
connection moves out of the radio range of its adjacent data
network node. In such a case, a data network node adjacent to the
breaking point informs the source about the breaking point in the
data connection. The source then tries again to set up a new
connection to the destination. To do this, the source initiates the
renewed transmission of a so-called connection search message,
which is sent through the entire data network. In this case, one
speaks of "flooding" the data network, since the connection search
message "floods" the entire data network. This "flooding" is a high
requirement for network capacity. In addition, the network capacity
required for the "flooding" is not available to other network
connections.
[0007] Moreover, upon breaking a data connection, no data transport
is possible any longer between source and destination. Data packets
which were already sent from the source to the destination, but
which could not pass the breaking point in time, are lost. Thus,
such data packets must be sent again by the source to the
destination, resulting in an increase in packet delay as well as a
waste of capacity in packet-oriented data networks. In transport
protocols, such as TCP (transport control protocol) used on the
Internet, these great delays lower the throughput of a data
connection, and therewith of the entire data network.
[0008] In order to achieve an especially high quality in a data
connection, one desires the continuity of an end-to-end connection.
This applies if commercial services are to be offered over such
data networks.
SUMMARY OF THE INVENTION
[0009] Embodiments of the present invention may provide a method
and a device for controlling data connections in a data network
having a plurality of data network nodes, which are able to ensure
an end-to-end data connection that is as free of interruptions as
possible.
[0010] Embodiments of the present invention may provide a method
and a device for controlling data connections in a data network
possessing a plurality of data network nodes.
[0011] Embodiments of the present invention may involve the judging
of the quality of a data connection in a data network having a
plurality of data network nodes according to the coding used. Here,
the term coding is used for the combinations of physical
transmission methods employed. For example, the combination of
modulation and puncturation in the OFDM method, or the various chip
rates in the CDMA method. In this context, a high coding
corresponds to a high data rate. The data are transmitted in
differently coded fashion over a data connection so as to assure a
transmission that is as secure and interference-resistant as
possible, as a function of channel quality. Especially in radio
communications networks that are used as data networks, coding is
useful for a sufficient transmission quality. In most data
networks, various coding methods are used, which may be adapted
dynamically to the quality of a data connection. This means that,
when there is a deterioration in the quality of a data connection,
the coding method is adapted to the deteriorated data connection.
This is the case in radio communications networks such as WLAN's,
according to the IEEE 802.11 standard or the ETSI HIPERPLAN/2
standard in GSM/GPRS, CDMA and UMTS mobile radio networks. Thus,
the coding method used for a data connection reflects the quality
of the data connection. By evaluating the coding methods used for a
data connection, for example, with the characteristic of the coding
methods used, it is now possible to assess the quality of a first
data connection, and depending on that, a second data connection
may be set up which is used as a substitute data connection in case
of the breakdown or in the case of a severe interference in the
first data connection.
[0012] Embodiments of the present invention may detect the
breakdown of a data connection, or a threatening interruption in
the data connection, in timely fashion, and ensure that an
alternative data connection is searched for and found. In some
embodiments of the present invention, at the moment of a
disconnection of the first data connection, or even earlier, it may
be possible to change to a second data connection without any
delay. This leads to a reduction of the control signals in the data
network, especially of connection search messages which, up to now,
were sent out by a source after the disconnection of a data
connection for the purpose of finding a new data connection. In
addition, packet losses are minimized or considerably reduced, if
not really completely eliminated. Finally, data or data packets are
also prevented from having to be transmitted again in response to a
disconnection of the data connection.
[0013] Embodiments of the present invention relate to a method and
a device for controlling data connections in a data network having
a plurality of data network nodes, in which the quality of a first
data connection is assessed in light of the adaptations of one or
more codings used for the first data connection, and, depending on
the assessment, a second data connection is set up that is used as
replacement for the first data connection. Radio terminals that act
like data relay stations may serve here as data network nodes. The
coding of data of a data connection here is to be dynamic, that is,
can be adapted as a function of the transmission quality of the
data connection used. By the assessment of the adaptations of one
or even several codings, a prediction may be made as to whether the
first data connection will be interrupted in future.
[0014] In embodiments of the present invention, the assessment of
the quality of the first data connection may be made in that, in
light of the codings used, at least one first data network node,
participating in the first data connection, makes a statement as to
whether the first data connection is becoming unstable. For
example, in a radio communications network, a first radio terminal,
acting as a data network node, is able to evaluate the quality of
the data connection to an adjacent second radio terminal by the
coding method used for the data transmission between the two radio
terminals. If the radio connection deteriorates, the transmitting
terminal changes the coding for its partial connection. If this
occurs several times in succession, it may be assumed that the data
connection between these two radio terminals will possibly be
interrupted in the future. Since the receiving terminal also
detects these changes in light of the coding that the transmitting
terminal is using, each of the two terminals is able to make the
statement as to whether the data connection will become
unstable.
[0015] In embodiments of the present invention, in response to a
statement that the data connection will become unstable, it is able
to initiate the search for a second data connection. The search may
be initiated, for example, by the emitting of a first message by
the at least one first data network node that has made the
statement that the first data connection is becoming unstable. In
this context, the first message is sent to second data network
nodes, for instance, to the data network nodes adjacent to the
first data network node.
[0016] In embodiments of the present invention, the message may
include the number of transmissions, the address of a transmitter
and the address of a receiver of data of the first data connection.
The number of transmissions ("time to life": TTL) is understood to
mean the number of partial transmissions for which data packets of
the first data connection are able to be transmitted and maintained
until they are discarded or become invalid.
[0017] In embodiments of the present invention, the message is sent
with a different coding than the coding(s) used in the first data
connection. Because of this, only those data network nodes which
are able to receive and decode the differently encoded messages,
are able to process the message. For example, data network nodes
are not able to process the message if they are outside the
reception range of the coding used. This procedure can effectively
prevent data network nodes of the first data connection from
becoming a part of the second data network connection.
[0018] In embodiments of the present invention, the new coding may
be a higher coding than the coding(s) used in the first data
connection, which means the message is not able to be transmitted
over connections between data network nodes that have a bad
transmission quality. This avoids routes that are not considered
stable.
[0019] In embodiments of the present invention, the second data
connection may be utilized when the first data connection is
disconnected. Alternatively, the second data connection may also
already be utilized if a prespecified coding is used for the first
data connection, for instance, an especially robust, that is, low
coding at a very poor transmission quality.
[0020] Embodiments of the present invention may relate to a device
for controlling data connections in a data network having a
plurality of data network nodes, which are designed in such a way
that the quality of a first data connection is assessed in light of
the adaptations of one or more codings used for the first data
connection, and, depending on the assessment, a second data
connection is set up that is used as replacement for the first data
connection.
[0021] In embodiments of the present invention, at least one first
data network node participating in the first data connection is
designed to assess the quality of the first data connection in
that, in light of the codings used, it makes a statement as to
whether the first data connection is becoming unstable. The at
least one first data network node may, for example, be set up by
program technology for carrying out the aforementioned assessment.
If the at least one first data network node includes a radio
interface, such as a plug-in card for a personal computer such as a
PCI card or a PC card for a laptop computer or a USB radio adapter,
its(their) operating program may be correspondingly set up. Radio
interfaces that are already present, having an operating software
in a programmable memory may be updated correspondingly.
[0022] In embodiments of the present invention, the at least one
first data network node may be designed so that, in response to a
statement that the first data connection is becoming unstable, it
initiates the search for the second data connection.
[0023] In embodiments of the present invention, the at least one
first data network node may be designed to initiate the search by
sending a first message to second data network nodes.
[0024] In embodiments of the present invention, the message may
include the number of transmissions, the address of a transmitter
and the address of a receiver of data of the first data
connection.
[0025] In embodiments of the present invention, the message may
have a different coding than the coding(s) used in the first data
connection.
[0026] In embodiments of the present invention, the different
coding may have a higher coding than the coding(s) used in the
first data connection.
[0027] Embodiments of the present invention may be designed to
switch over to the second data connection if the first data
connection is disconnected.
[0028] Alternatively, or even additionally, the device may be
designed to switch over to the second data connection if a
prespecified coding is used for the first data connection.
[0029] In embodiments of the present invention, the data network
may include a radio data network and at least two of the data
network nodes are radio terminals. This means that a data
connection in such a data network is able to include a radio
transmission link whose transmission quality depends, among other
things, on the motion of at least one of the terminals
participating in the radio transmission link.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 shows an exemplary embodiment of the present
invention having a first data network having a plurality of data
network nodes.
[0031] FIG. 2 shows an exemplary embodiment of the present
invention having a second data network having a plurality of data
network nodes.
[0032] FIG. 3 shows an exemplary embodiment of the present
invention having a third data network having a plurality of data
network nodes.
DETAILED DESCRIPTION
[0033] Some exemplary embodiments of the present invention,
described below, for the dynamic adaptation of multihop data
connections in data networks having a plurality of data network
nodes are, in principle, independent of a predictive method for the
behavior of a data connection. In the exemplary embodiments, the
assumption is made that a data network node, which is part of a
data connection, monitors the quality of the data connection with
respect to the coding method(s) used according to the present
invention. This data network node divides the data connection into
two parts: an input side part, which is the part of the data
connection on the side of the source between either the source or a
predecessor data network node and the data network node, and an
output side part, which is the part of the data connection between
the data network node and either the destination or a subsequent
data network node in the direction towards the destination.
Therefore, it is able to recognize the three following different
situations with respect to the input-side and the output-side part
of the data connection:
[0034] 1. The quality of the output-side data connection part
deteriorates, and, accordingly, more stable coding methods are
selected for the partial data connection. The conditions of the
input-side data connection part remain constant. From this, the
data network node is able to conclude that the destination or a
data network node that belongs to the output-side part of the data
connection is distancing itself from it.
[0035] 2. Both on the input-side part and the output-side part of
the data connection, the transmission quality is deteriorating, and
therefore more stable coding methods are selected. This means that
the data network node itself is moving.
[0036] 3. The quality of the input-side part of the data connection
is deteriorating, and a more stable coding method is selected.
However, the quality of the output-side part of the data connection
remains the same. From this, it may be concluded that the source or
a data network node of the input-side part of the data connection
is moving away from the data network node.
[0037] All the above-named situations are now able to be recognized
and evaluated, as will be shown below in light of the explanation
of various exemplary embodiments.
[0038] The first exemplary embodiment of the method according to
the present invention is based on a well-timed data connection
adaptation. This will also be designated below as early route
rearrangement (ERRA). An appropriate ERRA protocol relates, for
example, to a method that changes the route or the data connection
if it is predicted that an interruption of an existing data
connection threatens. The ERRA method is started before a data
connection is disconnected, for instance, if a data network node of
the data connection moves out of the radio range of its adjacent
data network nodes. In addition, the ERRA protocol uses a special
coding method for sending connection change messages, which are
designated as ERRA Request (ERRA_REQ), for short.
[0039] For example, FIG. 1 shows the sequence of the ERRA protocol
in light of a first data network having altogether 14 data network
nodes (numbered through from 1-14). In the data network shown,
there is a first data connection (shown as a broken line) from a
source terminal 0 to a destination terminal 14. The first data
network is a radio network and the data network nodes are
accordingly radio terminals.
[0040] At the beginning, a routing protocol such as, for instance,
AODV, has set up a multihop data connection from source terminal 0
to destination terminal 14 (in FIG. 1 designated as {circle around
(1)}). After setting up this data connection, and after the
beginning of a data transport over this data connection, a data
network node or a radio terminal 10 moves away from the set-up
route (designated in FIG. 1 as {circle around (2)}). The quality of
the data connection between the adjacent data network nodes or
radio terminals 5 and 10 thereby changes. A coding adaptation used
in the data network may react to this, in that the coding of
transmitted data between the two data network nodes 5 and 10 is
adapted in such a way that, in spite of the reduced data connection
quality, a sufficiently stable data transmission is able to take
place between the two data network nodes 5 and 10. These changes or
adaptations of the coding are observed by data network node 5. If a
prespecified boundary value is exceeded, that is, for example, in
response to the use of a prespecified coding based on a
particularly bad connection quality between data network nodes 5
and 10, data network node 5 initiates the ERRA protocol
mentioned.
[0041] To do this, data network node 5 emits an ERRA_REQ message
(denoted by {circle around (3)} in FIG. 1) that is addressed to all
data network nodes which are able to receive this message, in the
present case, data network nodes 3, 4, 6, 7 and 10. The ERRA_REQ
message includes the following entries: The number of transmissions
(also designated as time to life (TTL)) and the IP address of the
destination terminal and the source terminal 14 and 0,
respectively.
[0042] Each data network node or each radio terminal that receives
this message and knows a route to destination terminal 14, or which
may even be the destination terminal itself, replies with an
ERRA_REP message (in FIG. 1, the ERRA REP message is denoted by
{circle around (4)}; in FIG. 1 it is also denoted as ERRA_REPL). If
a data network node receives the ERRA_REQ message without knowing
destination terminal 14, it reduces the TTL field contained in the
message by 1, and, on its part, transmits the message thus changed
to all its adjacent data network nodes. If a data network node
receives an ERRA_REQ message having a TTL field that is 0, this
message is no longer passed on by the receiving data network
node.
[0043] The ERRA method provides that the ERRA_REQ message is more
sensitive, i.e., is coded higher than the data packets transmitted
between the two data network nodes 5 and 10. This prevents data
network node 10 from being able to receive the ERRA_REQ message on
a direct path, that is, by its old predecessor, and from replying
using its current route, which, to be sure, is supposed to be
changed in the future. This method leads to a second data
connection which uses a higher coding, and which accordingly has a
better channel quality than the first data connection (denoted in
FIG. 1 by {circle around (5)}).
[0044] As shown in FIG. 1, the second data connection includes
terminals 1, 2, 3, 5, 7, 12 and 13 as data network nodes. In place
of data network node 10 of the first data connection, in the second
data connection the data traffic between source terminal and
destination terminal 0 and 14, respectively, is now conducted via
data network node 7.
[0045] As an alternative to sending the ERRA_REQ message with a
higher coding than the coding that is used between data network
nodes 5 and 10 of the first data connection, data network node 5
may discard a direct reply from data network node 10, since it
knows that data network node 10 is replying using the route that is
to be replaced, or rather the first data connection.
[0046] After data network node 5 has received the ERRA REP message,
having an alternative route proposal or rather a second data
connection, it is able to decide whether it wishes to use the
alternative route or the second data connection, or whether the old
route or the first data connection should continue to be used. The
basis of this decision may, for example, be the number of data
network nodes which participate in the second data connection or
alternative route. If the new route or the second data connection
includes more data network nodes or source terminals than the old
route or the first data connection, data network node 5 or the
initiator of the search for an alternative route may communicate
this to source terminal 0, using a so-called ERRA_INFO message.
Based on this message, source terminal 0 is able to decide whether
the new route or second data connection should be accepted or
whether a search should be made for an additional new route or
third data connection as an alternative to the first data
connection.
[0047] As shown in FIG. 1, a BSPK (binary phase shift keying) 1/2
method is used as the coding method of the part of the data
connection between data network nodes 5, 10 and 12. The ERRA_REQ
message is 1/2 encoded using 16 QAM (quadrature amplitude
modulation). It is thereby not possible for data network node 10 to
decode the ERRA_REQ message from data network node 5. Thus, in this
case, the emitted ERRA_REQ message from data network node 5 is
encoded differently than the data packets that are able to be
received by data network node 10, if they were sent by data network
node 5.
[0048] The exemplary embodiment of the method according to the
present invention, shown in FIG. 2, utilizes a special situation
that is created by the prediction of the behavior of the quality of
a data connection. At a point in time at which the prediction
reports the imminent disconnection of a data connection, this data
connection still exists. The data network nodes of the data
connection that are situated within the region of the interruption
of the data connection may have the possibility to jointly search
for a second data connection that will bridge the gap occurring due
to the interruption of the first data connection. The method and
device designated below as early connection renewal or early route
update (ERU) makes use of this.
[0049] Again, it is assumed that, in a second data network having a
source terminal 0 and a destination terminal 7 as well as data
network nodes, at the beginning a first data connection exists
between source terminal 0 and destination terminal 7, (denoted in
FIG. 2 by {circle around (1)}). The first data connection is shown
as a broken line and includes data network nodes 1, 2, 3, 4 and
5.
[0050] Data network node 3 moves away from its adjacent data
network nodes 2 and 4, so that, in this region, the first data
connection deteriorates, or, stated more precisely, its quality
deteriorates (designated in FIG. 2 by {circle around (2)}).
Adjacent data network node 2 on the input-side part of the first
data connection, which includes source terminal 0, is informed of
this. From that, data network node 2 knows that the connection to
adjacent data network node 3 will soon disconnect. Thus, it is able
to make the prediction that the first data connection will
disconnect.
[0051] The ERU method assumes that almost every data network node
permanently checks its connection to adjacent data network nodes
and constantly has a current list in which all its adjacent data
network nodes are entered, that are located within radio reach.
This table is also designated as a neighborhood table. If the
functionality of the permanent monitoring of the connections to the
adjacent data network nodes is not available, a data network node
is able to search actively for adjacent data network nodes, using
so-called ERU_HELLO messages.
[0052] The initiator of the ERU method, data network node 2, is now
able to add data of its adjacent data network nodes, designated
also as PATCH_INFO, to a normal data packet (designated as {circle
around (3)} in FIG. 2). In the data network shown in FIG. 2, data
network node 2 would add to a data packet as PATCH_INFO that its
adjacent data network nodes are 1, 3, 9, 10, 11 and 12. This
represents the neighborhood table that was mentioned. Furthermore,
PATCH_INFO includes the address of the initiator data network node,
in the present case, the address of data network node 2, as well as
a sequence number and a counter for the length of the breaking
point of the first data connection. The counter for the length of
the breaking point is also denoted as breakage hop counter (BHC).
This PATCH_INFO message is transmitted with a data packet from data
network node 2, for instance, to data network node 3.
[0053] With the first transmission, the BHC is set to 1. Data
network node 3 has meanwhile been informed by its own prediction
unit about the quality of the data connection to adjacent data
network nodes via the change in the qualities of the data
connections input to it and output from it. Data network node 3
thereby detects that the data connections threaten to disconnect,
increases the BHC by 1 and forwards the PATCH_INFO message,
together with the data packet received from data network node 2, to
data network node 4.
[0054] Data network node 4 recognizes the PATCH-INFO message and
furthermore recognizes that only its incoming data connection, that
is, the data connection between it and data network node 3, is
changing. It may conclude from this that its position is remaining
stable, but that data network node 3 is moving away. It separates
the PATCH-INFO message from the received data packet, and sends an
ERU_REQ message to all its adjacent data network nodes (denoted by
{circle around (4)} in FIG. 2). The number of hops (TTL) for this
multi-address message is selected as a function of the BHC (in this
case, TTL=2). The ERU_REQ message to all adjacent data network
nodes includes two additional counters, one for the hops of the
alternative second data connection (alternative route hop counter
AHRC) and one for the hops to destination terminal 7 (destination
hop counter DHC). The ARHC is 1 at the first transmission, and is
increased by 1 at each additional transmission. The DHC includes
the distance to destination terminal 7 in hops. The TTL is reduced
by 1 at each dispatch. The ERU_REQ message is dispatched as long as
the TTL is greater than 0.
[0055] In the situation shown in FIG. 2, the ERU_REQ message may be
dispatched once by data network node 4, since data network node 8
knows one of the adjacent data network nodes and replies directly
in the direction of the initiator with an ERU_REP message (denoted
by {circle around (5)} in FIG. 2). The other adjacent data network
nodes pass on the ERU_REQ message according to the TTL.
[0056] If the initiating data network node 2 receives the ERU_REP
message with an alternative route, it may decide whether it wishes
to use it. If the DHC and ARHC are different, that is, the number
of hops is changing, then initiating data network node 2 must
inform source terminal 0 about it using a message ERU_INFO.
[0057] In the ERU_REQ message, the address of source terminal 0 is
also included. If this address is known to a data network node,
that is, if source terminal 0 is directly adjacent to this data
network node, this data network node may reply directly to source
terminal 0, which informs the initiating data network node by an
ERU_INFO message. In light of the DHC, source terminal 0 is then
able to recognize whether and how the number of hops has changed.
Using the ERU method, the alternative data connection maximally may
reach the length of the breaking point of the first data connection
plus 2 hops. The alternative route is denoted by {circle around
(6)} in FIG. 2.
[0058] The third exemplary embodiment of the method according to
the present invention shown in FIG. 3 may be suitable for breaking
points in a data connection which are triggered by individual data
network nodes that are moving away from the data connection. At the
beginning, as shown in FIG. 3, a first data connection from a
source terminal 0 to a destination terminal 5 exists in a third
data network having several mobile data network nodes. The data
connection includes data network nodes 1, 2, 3 and 4, and is shown
by a broken line in FIG. 3, as well as being denoted by {circle
around (1)}. Data network node 3 of the first data connection now
moves away from its original place (denoted in Figure by {circle
around (2)}). The third exemplary embodiment of the method
according to the present invention may be based on an optimized
early connection renewal, also designated as optimized early route
update (OPERU). The OPERU method is initiated by data network node
3, that is moving. With the aid of its prediction unit, data
network node 3 learns that all data connections incoming to it and
outgoing from it will soon disconnect because of its movement.
[0059] Data network node 3 reacts to this by sending an OPERU_REQ
message (denoted by {circle around (3)} in FIG. 3). This message
includes the address of predecessor data network node 2 of moving
data network node 3, of successor data network node 4 of moving
data network node 3, and of destination terminal 5, as well as a
counter for the number of hops to the destination. In addition, it
includes a sequence number. The OPERU_REQ message is sent only
locally to the adjacent data network nodes by moving data network
node 3, i.e., to data network nodes 2 and 4.
[0060] At this point, several situations may arise:
[0061] 1. At least one of the addressed data network nodes 2 and 4
replies with an OPERU_REP message to the OPERU_REQ message of
moving data network node 3. In this reply message, the
corresponding data network node 2 or 4 confirms that it knows the
predecessor data network node and the successor data network node
or destination terminal 5. An alternative route or a second data
connection is thereby found as replacement for the first data
connection.
[0062] 2. At least two data network nodes reply to the OPERU_REQ
message. One data network node replies that it knows the
predecessor data network node, and one data network node replies
that it knows the successor data network node or the destination
terminal. At this point, an additional case differentiation may be
carried out:
[0063] a) A data network node replies with an OPERU_REP message if
either predecessor data network node, successor network node or
destination terminal is known (denoted in FIG. 3 by {circle around
(4)}). If another data network node receives the OPERU_REP message
and if it knows the other side of the breaking point of the first
data connection, and has also received this OPERU_REP message, it
sends its own OPERU_REP message directly to the predecessor data
network node of the breaking point. A 3-hop connection may be set
up between two breaking points.
[0064] b) Several data network nodes reply to the OPERU_REQ
message. In this case, too, both sides of the breaking point of the
first data connection are represented; however, no alternative
second data connection is set up. In order, nevertheless, to be
able to find a route, data network node 3 sends a new OPERU_REQ
message. This includes the adjacent data network nodes that have
replied, and their known data network nodes. If there is a data
network node that has two data network nodes from the OPERU_REQ
message from both sides of the breaking point adjacent to it, then
there exists a 4 hop connection as an alternative. This data
network node replies with an OPERU_REP message directly in the
direction of the predecessor data network node.
[0065] 3. No data network node replies to the OPERU_REQ message, or
data network nodes reply with adjacent data network nodes of the
same side of the breaking point. In that case, the OPERU method
fails.
[0066] If the predecessor data network node receives an OPERU_REP
message with an alternative route, it is able to accept the route
or continue to use the previous route. If the predecessor data
network node accepts the new route, and if the number of hops of
the data connection between source terminal and destination
terminal thereby changes, the predecessor data node has to inform
source terminal 0 about the new situation, using an OPERU_INFO
message. Upon receiving the OPERU_INFO message, on its part, source
terminal 0 decides whether it accepts the changes in the route, or
whether, instead, it will initiate a new route search.
[0067] In summary, it should be mentioned that, of all the methods
explained above, the OPERU method requires the least signaling.
Therefore, the methods may also be used jointly, in a staggered
manner. In this case, there is the opportunity of using the OPERU
method as the first method. Within the OPERU method, the
predecessor data network node of a breaking point also notices
that, using the OPERU method, a second data connection or an
alternative route is being searched for. The predecessor data
network node then sets a timer OPERU_MAX_DURATION. If it receives
no reply within the time period specified by the timer, it then
triggers the ERU method. If this method also does not lead to
success, the ERRA method is started as the last local possibility,
since the ERRA method is able to make do even without a data
connection.
[0068] If all local methods for searching for a new data connection
fail, the source terminal is so informed. The latter will then
begin, as provided in the standard method, a new route search, or
it will notify the requesting service that, at the moment, no route
to the destination terminal is able to be found.
[0069] Thus, using the present invention, in data networks having
data connections that have a greatly fluctuating transmission
quality, it is possible to switch to alternative data connections
quickly and without great effort. Because of that, in spite of the
changing quality of data connections, one may achieve a high data
throughput and a low delay in data transmission, accompanied by a
small signalizing expenditure. The present invention is suitable
for use in multi-hop radio communications networks having mobile
radio terminals as relay stations or data network nodes. In such a
data network, the quality of an existing data connection can change
very rapidly, so that, without using the present invention, only a
small data throughput and great delays in transmission will occur.
On the other hand, using the present invention, it is possible to
achieve a relatively high data transmission rate and low delay
times, especially in the transmission of data packets, with only
little technical expenditure. This works out especially
advantageously for end-to-end connections via which, for example,
multimedia data are being transmitted.
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