Multiplex communications – Data flow congestion prevention or control – Flow control of data transmission through a network
Reexamination Certificate
1998-09-22
2004-08-03
Hsu, Alpus H. (Department: 2665)
Multiplex communications
Data flow congestion prevention or control
Flow control of data transmission through a network
C455S433000
Reexamination Certificate
active
06771604
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to communications networks including mobile asynchronous transfer mode (ATM) and Internet-Protocol (IP) networks. More particularly, the invention relates to route optimization and location management in communication networks.
The term “calling party's switch,” as used herein, is the network node from which a call originates, i.e., a call is generated from one of the endpoints of the calling party's switch, or a network node along the path of the call that is enabled to perform route optimization or is mobility-enhanced.
The term “home switch,” as used herein, is the switch to which an endpoint is assumed to be connected in the default mode. The address of the endpoint is derived from the network address of its home switch.
The term “visiting switch” as used herein, is the switch at which an endpoint is currently located.
The term “local switch,” as used herein, is an intermediate node between the calling party's switch and the home switch to which a call is cranked back during call setup before continuing on to the visiting switch.
The term “network node,” as used herein, is a system in a communications network that performs a switching or routing functions. A network node can be an access node if it has links to endpoints (users). A network node can be a transit node if all its links are to other network nodes with no links to endpoints. Examples of network nodes are ATM switches, IP routers, SONET cross-connects, telephony switches, WDM (Wavelength Division Multiplexed) optical cross-connects and other similar systems.
In a mobile network, the term “network node,” refers to an access point or a base station (which may include an ATM switch).
The term “mobile user,” as used herein, refers to a person connected to (or who will be connecting to) a node that is not a mobile user's home switch. A mobile user doesn't necessarily need a wireless interface.
The term “call,” as used herein, refers to any connection (e.g., voice, data, etc.) between an originating party and a receiving party over a communication path.
The term “call-forwarding,” as used herein, refers to a method in which a connection set up is continued from the home switch to the visiting switch of a called user.
The term “communication path,” as used herein, refers to the path from the originating party to the receiving party over the network.
The term “crankback,” as used herein, refers to a backtracking of the connection setup procedure (partial release of reserved resources).
BACKGROUND OF THE INVENTION
The use of ATM and IP technology in mobile communication networks is becoming increasingly common. In mobile ATM networks, “handoff procedures” and “location management procedures” are needed to support user mobility.
Location management is the process of tracking mobile users and locating them for delivering yet-to-be-established incoming call to the mobile user. In the process of conducting location management, the paths proposed for establishing the connections can become “sub-optimal,” i.e., the paths to be used may not be the best paths between the two endpoints of the connections.
Mobile user tracking procedures update the home node of a mobile user with information about the location of the mobile user. This information is used to deliver incoming calls to mobile users at their current location.
One prior art location management method is called “complete release” and is described with reference to FIG.
1
A. By this method, a mobile user
110
has a home switch
116
, but mobile user
110
is located near a visiting switch
118
. A calling party
114
attempting to call mobile user
110
will have the call routed to home switch
116
along connection
112
. Location information will be transferred back to the calling party
114
“advising” calling party
114
that the mobile can be reached via visiting switch
118
, whereupon connection
112
will be completely dropped, and connection
120
will be established to connect the call.
In the method illustrated in
FIG. 1A
, since the entire connection is being rerouted (i.e., there is no common path between the first connection
112
and the second connection
120
), latency is an issue. Considerable time and network resources are spent establishing the new connection
120
over an entirely new path, while dropping the first connection
112
.
Another prior art location management method, “call forwarding,” is illustrated with reference to
FIG. 1B
, by which a call is forwarded from the home switch of the mobile user to the visiting switch of the mobile user. Referring to
FIG. 1B
, the path between calling switch
114
and the visiting switch
118
is established by simply extending a new path
122
(shown in dotted line) to the visiting switch
118
from the old network node
116
, in a “connect-the-dots” fashion. Using this method, lower call setup latencies can be achieved because the old and new base stations are simply interconnected as needed. However, the path taken by the connection will often be sub-optimal, because the new path added on to the old one may follow a circuitous route.
Another prior art scheme, called a two-phase crankback scheme, allows for the call setup procedure to be cranked back from the home switch to a local network node, and then rerouted. This crankback is executed at a local level, which means that the overall end-to-end path taken by the connection could still be sub-optimal.
None of the prior art location management methods determine whether the route established between the originating point and the network node closest to the mobile user is optimal, nor do they optimize the connection path to establish such an optimal route. Suboptimality that is introduced during connection setup is primarily due to lack of exact information about the location of the mobile user at the call originating switch, and suboptimality occurs after connection setup because of movements by communicating mobile user. These suboptimal paths result in an inefficient usage of network resources.
Thus, there exists a need for a location management system which provides an efficient location management scheme/method to optimize routes of connections such that an efficient usage of network sources results.
SUMMARY OF THE INVENTION
Two location management schemes are disclosed herein. In a first embodiment, a procedure for finding an optimal path between a calling switch and a visiting switch node is integrated in the call set up procedure. The connection set up procedure starts by setting up a connection path between the calling switch and the home switch. Then, an “optimal crossover node” is determined along the connection path and then the connection path is cranked back starting from the home switch and moving towards the optimal crossover node. Once the optimal crossover node is reached, the a connection set-up proceeds to set up a connection between the optimal crossover node and the visiting switch.
In an alternative embodiment, first a connection is set up between the calling switch and the home switch. Then the connection is extended to the visiting switch either by the call-forwarding or by two-phase crankback method. This results in a quickly routed, but sub-optimal connection. Once the connection extension is completed by call forwarding or by the two phase crankback scheme, the route is optimized by selecting a segment on the sub-optimal connection for route optimization and then utilizing the method of the first embodiment to establish an optimally routed connection.
The method of determining an optimal connection path and rerouting the existing connection path to this optimal connection path, as described in the first embodiment, is applicable to all communication networks deploying connection-oriented technologies. These communications networks include land-line networks and mobile networks. Similarly, the method of route optimization for optimizing a suboptimal connection, as described in the second embodiment, is applicable to all communication networks dep
Dommety Gopal
Veeraraghavan Malathi
Hsu Alpus H.
Lucent Technologies - Inc.
Tran Thien D
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