Distributed infrastructure for wireless data communications

Details Distributed infrastructure for wireless data communications Distributed infrastructure for wireless data communications

1998-09-22

2001-04-10

Vincent, David R. (Department: 2732)

Multiplex communications

Communication over free space

Having a plurality of contiguous regions served by...

Reexamination Certificate

active

06215779

ABSTRACT:

TECHNICAL FIELD
This invention pertains to wireless communications systems and, in particular, to wireless packet data networks.
BACKGROUND ART
FIG. 1
FIG. 1
shows a conventional single-router wireless packet data network
100
. A packet router
102
receives data packets from the remainder of a network
104
and routes them to one or more network access points
106
-
110
. The network access points
106
-
110
transmit the packets forward to a user terminal
112
over forward wireless links
114
-
116
. The user terminal
112
transmits packets back to the network access points
106
-
110
over reverse wireless links
118
-
120
. The user terminal
112
may be a cellular telephone carried by a person, a portable computer, a mobile telephone in an automobile, or any other mobile device which must continue to provide connectivity even while it moves.
A control point
122
is connected to the packet router
102
. It manages the wireless links
114
-
120
. Management includes many functions. For example, as the user terminal
112
moves around the path loss between it and the network access points
106
-
110
changes. In the situation shown in
FIG. 1
, the control point
122
must cause the user terminal
112
to transmit with the minimum amount of power required to be received by at least one of network access points
106
-
108
. Mobile station transmit power is minimized since it causes interference to transmissions from other mobile stations. When the user terminal moves from the area served by network access point
106
to the area served by network access point
108
, there will be a handoff of the user terminal
112
from network access point
106
to network access point
108
. The control point
122
must manage the handoff. Other management functions are known to those with skill in the art.
FIG. 2
FIG. 2
shows a conventional multiple-router wireless packet data network
200
supporting a mobility protocol such as Mobile IP as described in the Internet Engineering Task Force RFC 2002. A second packet router
202
is connected to the first packet router
102
, to the rest of the network
104
, or (as shown) to both. Second packet router
202
is connected to network access points
204
-
206
. In
FIG. 2
, the user terminal
112
is moving from the area served by network access point
110
(where it is served by forward link
208
) to the area served by network access point
204
(where it is served by forward link
210
). Control point
122
manages the wireless links during this handoff (including the management of reverse links
212
-
214
) in much the same way as during the handoff shown in FIG.
1
. If desired, control can be passed from first control point
122
to second control point
222
. These control points are connected to first and second packet routers
102
and
202
, respectively.
FIG. 2
also shows a home agent
224
and a foreign agent
226
. Home agent
224
is connected to first packet router
102
, and foreign agent
226
is connected to second packet router
202
.
User terminal
112
has a network address for which packet router
102
advertises reachability. A packet intended for user terminal
112
is therefore sent to first packet router
102
. When user terminal
112
is in the coverage area of network access points associated with packet router
102
(
106
-
110
), packet router
102
will forward the packet to control point
122
which will send the packet for transmission to the network access points that currently provide a forward wireless link to the user terminal
112
.
User terminal
112
may leave the area served by first packet router
102
and may enter the area served by second packet router
202
. The net
104
will send packets destined to user terminal
112
to packet router
102
which will then forward them to home agent
224
which maintains track of user terminal
112
's current location in the form of a “care-of” address. The home agent will then encapsulate these packets in packets destined to the care-of address of the user terminal (e.g., foreign agent
226
) and send these packets through packet routers
102
and
202
. Upon receiving these packets, foreign agent
226
will de-capsulate the packets and forward the packets destined for transmission to user terminal
112
to control point
222
. Control point
222
will then forward the packets for transmission to the network access points that currently provide a forward wireless link to the user terminal
112
.
In this method, control of the network access points for a data connection has moved from control point
122
to control point
222
. In another conventional method, control does not move between the two control points, in which case packet router
102
continues to forward packets for transmission to user terminal
112
to control point
122
which then sends the packets directly to whatever network access points provide a forward wireless link to user terminal
112
, regardless of the system in which these network access points are located. E.g., control point
122
may forward packets for transmission to network access points
106
-
110
as well as
204
-
206
.
This architecture suffers from several fundamental problems: the control points for each part of the network are single points of failure which must be made highly reliable, increasing their cost. Furthermore, since they are unique for each network, the architecture does not scale well as the number of network access points increase, increasing with it the population of mobile terminals that can be served and consequently, the load presented to the control points. Last, emerging high speed wireless protocols require low-latency control by the control point which is not possible due to the transmission and queuing delays between the control points and the network access points.
DISCLOSURE OF INVENTION
Applicants provide a solution to the shortcomings of the previously described architecture by distributing the functionality of the control points and allowing the co-location of a control point with every network access point. The architecture proposed by the applicants is further optimized by co-locating foreign agents with the network access points and control points.


REFERENCES:
patent: 5384826 (1995-01-01), Amitay
patent: 5726984 (1998-03-01), Kubler et al.
patent: 6094740 (2000-07-01), Boccuzzi et al.
patent: 0813346 (1997-12-01), None
patent: 2247811 (1992-03-01), None
Platt, et al. “Distributed Management of Mobility for Mobile Cellular Networks” Proceedings fo Int'l Conf. On Computer Communication 13:351-357 (1997).
Yokoyama, Mitsuo “Decentralization and Distribution in Network Control of Mobile Radio Communications” The Transactions of the IEICE:E73(10): 1579-1586 (1990).

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