Interactive video distribution systems – Video distribution system with upstream communication
Reexamination Certificate
1996-04-10
2001-05-29
Miller, John W. (Department: 2611)
Interactive video distribution systems
Video distribution system with upstream communication
C725S122000, C725S127000, C348S014010, C348S014110
Reexamination Certificate
active
06240554
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to local area networks, and, in particular, to a local area network for the simultaneous, bi-directional transmission of video bandwidth signals.
Local area networks which can transmit video bandwidth signals are known.
FIGS. 1-3
show some prior art networks. In
FIG. 1
, there is a hub
10
, which includes a central processor and an N×N crosspoint switch, with N being the number of user paths
18
(the number of inputs and the number of outputs) to be connected to the hub
10
. The N×N crosspoint switch in the hub
10
permits all the users
12
on the hub
10
to communicate with each other, but it is limited to N users.
FIG. 2
shows one way in which the arrangement of
FIG. 1
can be expanded to include more users. In that arrangement, three users
12
have been removed from each hub
10
, and the other user ports have been used to connect to other hubs
10
along the paths
14
. In this way, more users can be interconnected, but there is a limit to the number of users that can be connected to this system, because every time a new hub is added, a user has to be subtracted from all the other hubs.
FIG. 3
shows a way in which many hubs
10
can be interconnected by connecting them to a bus
20
along the paths
16
. With this arrangement, a user
12
A connected to the hub
10
A on the left can communicate with a user
12
C connected to the hub
10
C on the right by transmitting a signal along its respective path
18
A to its hub
10
A, along the path
16
A to the bus
20
, where it occupies a channel along the entire bus
20
, which can be received by a user
12
C by passing along the path
16
C to the hub
10
C and then to the user
12
C. This arrangement is limited in that, once all the channels on the bus
20
are used up, no additional signals can be transmitted from hub to hub. If a video conference is being conducted between a user
12
A and a user
12
C on channel
1
, then users
12
F and
12
G (off the page to the right) cannot conduct another video conference on channel
1
at the same time.
The arrangement of
FIG. 3
is also severely limited in the number of connecting lines
16
between each hub
10
and the bus
20
, so that, if there is only one connecting line
16
A between the hub
10
A and the bus
20
, then only one channel of the bus
20
can be used by the users
12
A at any one time. This means that, if a user
12
A is conducting a video conference with a user
12
C on channel
1
, then another user
12
A cannot watch a video on another channel of the bus
20
at the same time. In order to provide more connecting lines to the bus
20
, users
12
would have to be removed from the hub
10
, which again limits the function of the network.
Another problem with prior art networks is that, if they use twisted pair wiring, they are very limited in the distance over which they can carry signals before the signal degrades to the point that it is not useful.
SUMMARY OF THE INVENTION
The present invention provides a local area network for the simultaneous, bi-directional transmission of video bandwidth signals which is very versatile while also being very cost-effective.
The present invention provides a local area network which can be used for video-conferencing, for remote control and viewing of video tapes or video cameras, and so forth.
The present invention provides a local area network which permits channel segmentation, so that a signal may be stopped at a switching matrix and replaced by another signal which travels on the same channel to the next switching matrix. This permits greater flexibility than does a typical bus, in which the same signal is transmitted to all users on a given channel.
The present invention also provides for the automatic equalization of signals to compensate for signal degradation, so that signals can be sent over twisted pair wiring for long distances.
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Miller John W.
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