Packet communication system

Details Packet communication system Packet communication system

1999-01-28

2003-05-13

Ton, Dang (Department: 2666)

Multiplex communications

Pathfinding or routing

Combined circuit switching and packet switching

C370S216000

Reexamination Certificate

active

06563815

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to a packet communication system used for packet mode communication of a signal, such as, an audio signal or a video signal through a communication network, and more particularly to a packet communication system suitable for packet mode communication of a signal, such as, a speech signal between communication networks using signal types different from each other.
With the recent progress of the architecture of a LAN (local area network), the network system connecting small size computers, such as, personal computers using the LAN is also increasing. Thus, an attempt is now being made for integration of communications by permitting voice communication on the LAN too in addition to a conventional telephone network (including a PBX network that is a private branch exchange network).
As an example of such an attempt, there is a “voice communication system” as shown in FIG.
4
. This voice communication system is composed of telephones connected to a conventional telephone network, packet communication units connected to a packeted speech signal communication network (referred to hereinafter as a packet communication network), and a communication gateway used to realize mutual connections between the telephones and the packet communication units. A network carrying such a speech packet on the LAN described above is an example of the packet communication network.
Referring to
FIG. 4
, the reference numerals
21
and
22
designate telephones connected to a private branch exchange network (a PBX network)
13
and a public telephone network
20
,
104
designates a subscriber line of the private branch exchange network
13
,
105
designates a subscriber line of the public telephone network
20
, and they have the same interface. On the other hand, the reference numeral
101
designates a packeted speech signal transmission network in the form of, for example, a LAN based on the CSMA/CD (carrier sense multiple access with collision detection) scheme according to the standards defined in the IEEE 802. 3. A plurality of packet communication units
14
,
15
and
16
are connected to this LAN
101
.
The packet communication units
14
,
15
and
16
are in the form of small size computers, such as, personal computers provided with handsets
17
,
18
and
19
respectively. These packet communication units
14
,
15
and
16
have, on one hand, functions of packeting speech signal inputs from the handsets
17
to
19
and sending out the packeted speech signals onto the LAN
101
and, on the other hand, functions of converting the packeted speech signals received via the LAN
101
into ordinary voice streams again and reproducing the original speech by the handsets
17
,
18
and
19
.
The reference numeral
11
designates a mail box connected to the LAN
101
to store a filed voice mail. The packet communication units
14
,
15
and
16
can store such filed voice mails in the mail box
11
through the LAN
101
and can also fetch such voice mails, transmitted from the other packet communication units and stored in the mail box
11
, so as to internally convert the stored voice mails into voice streams again and reproduce the original speech signals by the handsets
17
,
18
and
19
.
The reference numeral
12
designates a communication gateway which controls communication between the LAN
101
that is the packet communication network and the private branch exchange network
13
that is the conventional telephone network. In this case, a subscriber line accommodating an existing telephone is commonly used as a connection line
102
between the private branch exchange network
13
and the communication gateway
12
. However, this connection line
102
may be an interface between the telephones in the private branch exchange network.
Suppose now the case where voice communication is made among the packet communication units
14
,
15
and
16
in the LAN
101
in the voice communication system having the structure described above. In the case of making voice communication between, for example, the packet communication units
14
and
16
, the speech packet is transferred through a communication path
121
. On the other hand, in the case of making communication between the packet communication unit
14
and the private branch exchange network
13
or the telephone
21
or
22
connected to the public telephone network
20
, the speech packet is transmitted through a communication path
122
in the LAN
101
. In this case, the packeted speech signal on the LAN
101
is converted by the communication gateway
12
into the corresponding voice stream before being transferred to the private branch exchange network
13
or the public telephone network
20
. In the case of a speech signal transmitted from the side of the private branch exchange network
13
or the public telephone network
20
toward the packet communication unit
14
in the LAN
101
, its voice stream is packeted by the communication gateway
12
to be sent out to the LAN
101
.
In the case of integration of voice communication in a packet communication network in the form including a conventional telephone network, it is an undeniable fact that the number of users having their telephones connected to the conventional telephone network is actually predominantly large although the number of terminals connected to the packet communication network is increasing. Therefore, when the desired integration of the voice communication is considered, the amount of communication between the telephones connected to the conventional telephone network and the terminals connected to the packet communication network is expected to considerably increase.
On the other hand, when the future of the packet communication network is reviewed, an undeniable situation will appear in which the users possessing their telephones already become new members of the packet communication network. For example, although specific users, such as, persons holding administrative positions in a company only possess the packet communication units in the LAN in the company at present, it is apparent that there will be an increasing tendency of introducing the packet communication units in future so that all the members of the company can possess the packet communication units.
However, the prior art packet communication units connected in the packet communication network are basically considered to make communication in packet form. Thus, the desired integration of the voice communication in the form including the conventional telephone network will bring forth such a problem that the communication gateway tends to be overloaded due to concentration of loads, resulting in impossibility of connection or communication.
Further, when the packet communication unit is newly provided for the user possessing his telephone already, the same user possesses both the telephone and the packet communication unit. As a result, the cost inevitably increases, and such a problem arises that the user cannot deal with simultaneous occurrence of a communication request from both the telephone and the packet communication unit. The same applies also to the case where the telephone is newly provided for the user who possesses the packet communication unit only.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a packet communication system which can reliably and economically ensure communication between communication units connected in a conventional telephone network and those connected in a packet mode network.
Another object of the present invention is to provide a packet communication system which is constructed to be accommodated in the prior art network by adding a function of connection to the conventional telephone network in addition to the function of connection to the packet mode network, so as to lighten loads imposed on a communication gateway, to decrease the amount of materials of an interface circuit or parts for connection to the conventional telephone network, and to reduce the cost of the syste

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