Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
2000-06-26
2004-10-12
Pham, Chi (Department: 2663)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C370S312000, C370S432000
Reexamination Certificate
active
06804221
ABSTRACT:
FIELD OF INVENTION
This invention is related to the field of wireless communication (e.g., cellular networks). More specifically, it relates to registering mobiles and routing packets to and from mobiles in both home and foreign domains.
BACKGROUND OF INVENTION
The Internet has revolutionized the way society does its day-to-day chores. Such day-to-day chores include reading our daily morning papers, trading stocks, keeping track of weather, buying clothes, etc. Furthermore, the technology of wireless communications continues to improve. Wireless communications transitioned from analog radio systems to digital systems back in the sixties and now offers broadband access. Furthermore, because of the Internet (along with associated Internet applications) the wireless networking revolution will continue its rapid growth.
Mobile IP [RFC2002]; IP
mobility support
, Charles Perkins (Editor), RFC 2002, October 1996, hereby incorporated by reference, provides a framework wherein mobile nodes (or mobile hosts or mobiles) can move from one point of attachment (e.g. a sub network in an enterprise) to another point of attachment (e.g. another sub-network in another enterprise) and still be able to communicate with other nodes. The reason mobile IP can do this is because it provides the means to keep track of the current location (called a binding in the Mobile IP specification [RFC2002], and have all the traffic forwarded to the mobile node's current location transparently. Whenever the mobile node moves from one sub-network to another, its location is updated by updating the tracking (i.e. the binding) which is maintained in its home network (e.g. the network in which the user is officially registered).
However, updated tracking comes at a cost. Overhead, in the form of handoffs, is incurred when updating the tracking. Everytime a mobile host performs a handoff in a foreign network, Mobile IP Registration Request and Response messages are exchanged between the mobile host and the home agent.
One solution to the problem of frequent registration request messages being sent to the home agent is to take advantage of the domain concept and the topology of the domain (usually Tree-like). (A domain refers to a collection of base stations and routers under a unique administrative authority). Domains can be arranged in a hierarchical or tree-like manner. A root system is connected to successively lower levels of systems or servers). The base stations in cellular networks are usually clustered together with routers in the upstream to form domains that determine that determine where packets are forwarded.
Several protocols, such as HAWAII [Lucent], Cellular IP [Ericsson], and Hierarchical Foreign Agent, have been proposed to decrease the amount of messages sent to the home agent (HA). Each of these protocols uses the domain concept to reduce the number of messages sent. The HAWAII and Cellular IP proposals are very similar, but HAWAII has greater appeal because it offers a more complete solution to the above stated problem. An overview of the design of the protocols used in each is given below. Brief descriptions of the proposals from Singapore University and Hierarchical Micro-mobility Management are also given.
1.1 Handoff Aware Wireless Access Internet Infrastructure [HAWAII]
Some of the features of HAWAII include:
Defined two-level hierarchy along domain boundaries and defined separate mechanisms for inter-domain and intra-domain mobility. A unique co-located care-of-address is assigned to the mobile host to provide for QoS support.
Special paths are established to maintain end-to-end connectivity as the mobile host moves. These paths are used to provide a hop-by-hop routing of packets in the domain.
Soft-state mechanisms are used to provide a degree of tolerance to router or link failures within the network.
Depending upon the capability of the mobile host (i.e., the wireless technology used by the mobile node), two different schemes for smooth handoffs are provided. First, a non-forwarding scheme for mobile nodes is used that can receive data simultaneously from two different base stations. Second, a forwarding scheme for nodes is used that can receive data from only one base station at a time.
1.1.1 Terminology Used in HAWAII
Home Domain: This is the domain to which a mobile node belongs.
Foreign Domain: Any domain that the mobile node visits that is not its home domain.
Domain Root Router (DRR): This is the gateway to a domain.
Update Messages: These are messages sent by the base station to the routers upstream to update the entries of a mobile node periodically (using a lifetime) or when a handoff occurs.
1.1.2 Principles
The gateway into each domain is called the domain root router. Each mobile host has an IP address and a home domain. A domain may cover an area containing a few hundred base-stations, thereby increasing the probability that the mobile host remains in the same domain as it moves around. Maintaining the mobile host within the home domain reduces greatly the home agent's job.
When a mobile node (MN) moves into a foreign domain, the usual mobile IP concepts come into play. Each mobile host is assigned a unique co-located care-of-address and the address is unchanged when moving within the foreign domain. The home agent (HA) tunnels the packets to the co-located care-of-address. (Tunneling is the technique by which datagrams are sent into the payload of a protocol of the same layer (e.g., IP layer). For example, tunneling occurs when an IP packet is put into another IP packet). The home agent is not notified of movements within the foreign domain and connectivity is maintained using dynamically established paths in the foreign domain.
1.1.2.1 Sequence of Operations—Power Up
The base station determines if the MN is at home or in a foreign domain by comparing the network access identifier (NAI) sent along with the registration request with the NAI of the current wireless domain. See
The Network Access Identifier
, B. Aboba, Microsoft Corporation, M. Beadles, WorldCom Advanced Networks, RFC 2486, January 1999, hereby incorporated by reference. If the mobile is at home, the base station creates a route entry in every node up to the domain root router. On the other hand, if the mobile is in a foreign domain, the base station must forward the registration request to the home agent and create a route entry in every node up to the domain root router.
Packets from a correspondent node (CN) are sent to the home network of the MN.
The packets are intercepted by the HA and then tunneled to the MN using the co-located care-of address (CCOA). When the packets reach the wireless domain they are routed using the hop-by-hop route entries previously created.
1.1.2.2 Sequence of Operations—Intra-Domain Handoff (Non-Forwarding Scheme)
Upon receiving a registration request from a MN, the base station (BS) determines the old BS IP address that the MN has moved out of as the MN sends the previous foreign agent node extension (PFANE), which includes the old BS address, along with the new registration request to the BS.
If the movement was an intra-domain movement, then the BS sends a Hawaii update message to the old BS, updating the cache of all the routers in the path between the new BS and the old BS.
The old BS then sends an acknowledgement back to the new BS.
The Above Operations Provide for Smooth-handoffs.
1.1.3 Sequence of Operations—Data Flow
Packets sent by the CN are sent to the MN's home network, the HA intercepts these packets and tunnels them to the CCOA. The DRR then sends the packets downstream through the appropriate interface on a hop-by-hop basis.
The crossover router then forwards the packets to the next hop router through the interface per the HAWAII entry.
1.2 Cellular IP [CIP]
Cellular IP allows the routing of IP datagrams to a mobile host. The cellular IP protocol, along with mobile IP, is intended to provide wide-area mobility support. Cellular IP has been designed for use on a local level, like in a ca
Choyi Vinod Kumar
Magret Vincent
Alcatel
Ferris Derrick W
Moskowitz Larry
Pham Chi
Sewell V. Lawrence
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