Data processing: structural design – modeling – simulation – and em – Simulating electronic device or electrical system
Reexamination Certificate
1999-03-19
2001-09-25
Teska, Kevin J. (Department: 2123)
Data processing: structural design, modeling, simulation, and em
Simulating electronic device or electrical system
C703S023000, C370S229000, C710S060000
Reexamination Certificate
active
06295516
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a data transmission apparatus and a data transmission system, and more particularly to a data transmission apparatus suitable for use for transmission of audio visual data for which a protocol of the IEEE (Institute of Electrical and Electronics Engineers) 1394 High Performance Serial Bus Standards (hereinafter referred to as IEEE 1394 serial bus) is used.
It is highly anticipated that the IEEE 1394 serial bus will be spread widely in the future as a digital interface for connection between a world of digital audio visual apparatuses and a world of a personal computers. The reason why such high anticipation is directed to the IEEE 1394 serial bus is that it has such significant characteristics as given below. In particular, while a related art audio visual apparatus (hereafter referred to as AV apparatus) normally employs a DS link wherein data transmission is performed by two-value difference driving, the IEEE 1394 serial bus realizes three-value difference driving at a high data transfer rate of 100, 200, 400 Mbps by simultaneous driving of two nodes linked to each other by a shielded 6-pin cable including a twisted line and a power supply line in a pair.
Where the IEEE 1394 bus is used to communicate audio digital data (hereinafter referred to as AV data) between two arbitrary nodes, communication data are divided into packets and transmitted in time division in cycles of the interval of 125 &mgr;s. More particularly, isochronous communication in which an isochronous packet is used and asynchronous communication in which an asynchronous packet is used are performed suitably. AV data are transmitted basically with isochronous packets. For example, two nodes which intend to communicate AV data using isochronous communication access, in order to secure a data transmission band for the isochronous communication when they act as a transmitter and a receiver, utilize a predetermined address of a node (hereinafter referred to as route), which serves also as a management apparatus of a transmission line, by asynchronous communication in a time band which remains in each cycle and is not used for data transmission of isochronous communication to request for a bandwidth (channel) to be used for the isochronous communication.
In response to the request, the route performs arbitration (allocation of a bandwidth) and provides an isochronous reference (hereinafter referred to as IR) issued from an isochronous resource manager (hereinafter referred to as IRM) built therein to each of the nodes successively beginning with the node to which the route has assured a bandwidth for communication. Each of the nodes on the IEEE 1394 serial bus performs isochronous communication with the IR supplied thereto and consequently can transmit or receive AV data connected thereto to or from the other node. After the communication of AV data is completed, each of the nodes returns its IR to the IRM of the route.
According to the transmission system described above, however, also when a codec has a variable compression ratio of transmission data such as a wavelet transform codec used to transmit AV data in accordance with an image compression/decompression protocol having a variable transmission bandwidth, AV data are transmitted by isochronous communication corresponding to the fixed used bandwidth determined by the IRM upon establishment of connection between the nodes. Consequently, the related art transmission system described above has a subject to be solved in that, even when the occupied bandwidth of the bus varies during the communication of AV data and a greater margin appears with the bandwidth of the transmission line or the margin of the bandwidth of the transmission line disappears, it is difficult to suitably vary the transmission bit rate of transmission data in response to the variation of the occupied bandwidth of the bus.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a data transmission apparatus and a data transmission system which allow transmission of data with a higher efficiency.
In order to attain the object described above, according to the present invention, each node suitably varies its setting of a bandwidth to be used for isochronous communication in response to a variation of a bandwidth.
In particular, according to an aspect of the present invention, there is provided a data transmission apparatus for communicating data with a variable transmission bandwidth over a data transmission line, including a detection means for detecting a bandwidth of data transmission actually used in the transmission line, a calculation means for calculating a bandwidth required for transmission of data to be transmitted and a requesting means for requesting, when the bandwidth of data transmission actually used in the transmission line varies, a management apparatus for the transmission line to set a bandwidth in the transmission line in response to the bandwidth calculated by the calculation means.
According to another aspect of the present invention, there is provided a data transmission system comprising a first data transmission apparatus including a detection means for detecting a bandwidth of data transmission actually used in a data transmission line, a calculation means for calculating a bandwidth required for the data transmission, and a requesting means for requesting, when the bandwidth of data transmission actually used in the transmission line varies, a management apparatus for the transmission line to set a bandwidth in the transmission line in response to the bandwidth calculated by the calculation means, and a second data transmission apparatus for communicating data with the first data transmission apparatus over the data transmission line, wherein the first data transmission apparatus controls the calculation means to calculate a bandwidth required for data transmission with the second data transmission apparatus and requests, when the bandwidth of the data transmission line actually used varies, the management apparatus to set a bandwidth of the transmission line connected to the second data transmission apparatus in response to the bandwidth calculated by the calculation means.
The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings in which like parts or elements denoted by like reference symbols.
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Maioli Jay H.
Sergent Douglas W.
Sony Corporation
Teska Kevin J.
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