Telephonic communications – Telephone line or system combined with diverse electrical... – Having transmission of a digital message signal over a...
Reexamination Certificate
2001-10-04
2003-11-11
Woo, Stella (Department: 2643)
Telephonic communications
Telephone line or system combined with diverse electrical...
Having transmission of a digital message signal over a...
C379S093080
Reexamination Certificate
active
06647098
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to communications devices and communications systems connected to a device for data transmission/reception and, more specifically, a communications device and a communications system connected to a device and capable of switching a data transmission scheme among nodes.
2. Description of the Background Art
A conventional communications device is described with reference to the drawings.
FIG. 8
is a block diagram showing the structure of the conventional communications device. In
FIG. 7
, a communications device
604
forms one node including a network interface unit
600
, a network controller
602
, and a CPU (Central Processing Unit)
603
.
The network controller
602
transmits/receives data to/from a device
605
, such as a CD (Compact Disk) player or a speaker, that is connected to the communications device
604
. The network controller
602
also transmits/receives data to/from devices of other nodes through the network interface unit
600
. The CPU
603
controls the network controller
602
, and communicates with the device
605
and the network controller
602
.
The network interface unit
600
is coupled to a network
601
, and includes a transmission signal processing unit
606
and a reception signal processing unit
607
. The transmission signal processing unit
606
converts data outputted from the network controller
602
into data in a predetermined transmission format appropriate for use over the network
601
. The reception signal processing unit
607
converts the data in the transmission format received through the network
601
into data processable by the network controller
602
.
FIG. 8
is a block diagram illustrating an exemplary case where six nodes similar in structure to the communications device
604
shown in
FIG. 7
are coupled to each other, forming a ring shape network. In
FIG. 8
, first to sixth nodes
701
to
706
are coupled to each other via the network
601
by each connecting to its adjacent nodes, thereby forming a ring-typed network. Also, the first to sixth nodes
701
to
706
are respectively connected to corresponding first to sixth devices
751
to
756
for communications over the network
601
.
In
FIG. 8
, data outputted from the first device
751
such as a CD player is supplied to the first node
701
, and then forwarded to the second node
702
through the network
601
. If the destination of the data is not the second node
702
, the second node
702
forwards the data to the third node
703
. In this manner, the data is transferred clockwise until it reaches the destination.
Consider a case, for example, where the third device
753
is a right speaker and the fifth device
755
is a left speaker. In this case, right and left audio data outputted from the first device
751
such as a CD player is forwarded, through the first node
701
and the second node
702
, to the third node
703
. In the third node
703
, audio data for the right speaker is extracted, and then forwarded to the third device
753
. The right and left audio data is further forwarded through the fourth node
704
to the fifth node
705
. In the fifth node
705
, audio data for the left speaker is extracted, and then forwarded to the fifth device
755
.
Here, in the communications device
604
shown in
FIG. 7
, the transmission signal processing unit
606
and the reception signal processing unit
607
each require some time for processing signals. Also, the network controller
602
requires some processing time. Furthermore, communications with the device
605
requires a predetermined time. Therefore, if the first to sixth nodes
701
to
706
similar in structure to the device
604
are coupled in a ring shape as shown in
FIG. 8
, a time lag occurs between the time when data outputted from the first node
701
reaches the third node
702
and the time when the data reaches the fifth node
705
.
More specifically, if the output data from the first node
701
is digital stereo audio data, a time lag occurs between the time when right audio data reaches the third device
753
and the time when left audio data reaches the fifth device
755
. As a result, right audio and left audio are reproduced with a time lag, sounding strange to listeners. This also occurs in the case of three or more speakers, even more than in the case of two speakers.
To reduce such time lag, a predetermined delay is applied to the device (or node) side which data should reach earlier. However, if the lag varies with changes of the data transmission scheme or other factors, the predetermined fixed delay cannot be used.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a communications system and a communications device that can accurately correct, with a simple structure, a delay to be applied in order to reduce the difference in reaching time of data that should simultaneously reach respective destinations, thereby providing audio reproduction without making listeners feel strange.
The present invention has the following features to attain the object above.
A first aspect of the present invention is directed to a communications system comprising a plurality of nodes including at least one transmission scheme variable node that selects a transmission scheme for use from a plurality of transmission schemes, and a network coupling the transmission nodes, wherein
the transmission scheme variable node carries out communications for transmitting, before using the selected transmission scheme, information about the selected transmission scheme to another node by using a previously set transmission scheme, thereby correcting reaching times of data that should almost simultaneously reach respective two or more different nodes.
As described above, in the first aspect, it is possible, with a simple structure, to accurately correct a delay to be applied in order to reduce the difference in reaching time of data that should simultaneously reach respective destinations, such as data for the right speaker and data for the left speaker. Thus, a communications system capable of reproducing audio without making listeners feel strange.
According to a second aspect, in the first aspect,
the transmission scheme variable node includes
a network controller for communicating with a device externally provided, and controlling data communications with the other node;
a central processing unit for controlling the network controller for communications;
a transmission signal processing unit for converting data coming from the network controller into a transmission signal over the network;
a reception signal processing unit for converting a reception signal received over the network into data processable by the network controller;
a transmission scheme determination part for selecting the transmission scheme for use in the transmission signal processing unit and reporting information about the selected transmission scheme to the other node, and setting the transmission scheme for use in the transmission signal processing unit and the reception signal processing unit; and
a switching unit for switching, after the information about the transmission scheme selected by the transmission scheme determination part is transmitted to the other node, connection of the transmission signal processing unit and the reception signal processing unit to the network.
As described above, in the second aspect, even if the transmission scheme is changed in each node, the information about the transmission scheme for use is transmitted to another node, thereby accurately correcting the delay to be applied in order to reduce the difference in reaching time of data that should simultaneously reach respective destinations.
According to a third aspect, in the second aspect,
the central processing unit receives the information about the transmission scheme selected by the transmission scheme determination part, and calculates a delay time for correcting the reaching time of the data.
As described above, in the third
Katta Noboru
Kawada Hirotsugu
Mizuguchi Yuji
Sakai Takahisa
Wenderoth , Lind & Ponack, L.L.P.
Woo Stella
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