Pulse or digital communications – Synchronizers – Frequency or phase control using synchronizing signal
Reexamination Certificate
2000-02-29
2004-02-03
Chin, Stephen (Department: 2734)
Pulse or digital communications
Synchronizers
Frequency or phase control using synchronizing signal
C375S366000, C370S324000, C370S509000, C714S707000, C714S751000, C714S758000, C714S789000
Reexamination Certificate
active
06687318
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the synchronization of two devices with a data transmission method.
In the transmission of compressed data, for instance audio-visual data, textual data, video data or control information, errors in the transmission can disrupt a subsequent decompression such that the data can no longer be reconstructed correctly.
In the context of the transmission of highly compressed data currents, the following communication system architecture is known, which is illustrated in
FIG. 2
(cf. [1]):
Applications of a predeterminable number of application layers Ai (i=1 . . . n) generate data Di, which are to be transmitted from a first device V
1
to a second device V
2
.
The data Di that are to be transmitted are respectively delivered to what is known as an adaptation layer Ali, which is allocated to the respective application Ai.
The different types of adaptation layers described in [1] serve for processing different characteristic data.
Data should be understood here as, for instance, audio data, video data, textual data (in particular, data that are coded according to ASCII code)—generally any kind of data that can be transmitted in digital form.
From the respective adaptation layer Ali, adapted data Adi are fed to a multiplexer MUX/DEMUX for purposes of forming a combined, i.e. multiplexed, data current XD.
Via a transmission unit UE, for instance a wirebound network or a mobile radio network, the data current XD is transmitted to the second device V
2
. The second device V
2
has the same structure as the first device V
1
. In the second device V
2
the multiplexed data current XD is split into the individual adaptive data adi again; that is, demultiplexed. The adapted data Adi is fed by the multiplexer/demultiplexer MUX/DEMUX to the elements of the adaptation layer Ali of the second device V
2
. The double arrows in the individual communication paths indicate that the communication between the first device V
1
and the second device V
2
can occur bidirectionally.
In the method taught in ITU-T Recommendation H.223
, Multiplexing Protocol for Low-Bitrate Multimedia Communication
1996, a separate error detection method and/or error correction method is carried out for the data in the adaptation layer.
The more higher-level or robust the error detection method, or the error correction method, (i.e. the more errors can be detected, or corrected in the transmission), the greater the demand for bandwidth in the transmission of the data currents grows, due to additional redundancy information that is required for error correction, or error detection. Furthermore, the complexity of the error detection, or error correction method, grows with rising executions which leads to an elevated demand for computing time both for the encoding at the sender and for the decoding at the receiver.
For this reason, documents ITU-T Recommendation H.223
, Multiplexing Protocol for Low-Bitrate Multimedia Communication
1996 (cf. Reference 1); ITU-T Draft Recommendation H.223/Annex A, Multiplexing Protocol for Low-Bitrate Mobile Multimedia Communication, Level 1, Draft version, July, 1997 (cf. Reference 2); ITU-T Draft Recommendation H.223/Annex B,
Multiplexing Protocol for Low-Bitrate Mobile Multimedia Communication
, Level 2, Draft version, July, 1997 (cf. Reference 3); and ITU-T Draft Recommendation H.223/Annex C,
Multiplexing Protocol for Low-Bitrate Mobile Multimedia Communication
, Level 3, Draft version, July, 1997 (cf. Reference 4) teach the provision of various error detection methods, or respectively, error correction methods, that are more or less robust, depending on requirements, but are less or more complex, accordingly.
Reference 1, Reference 2, Reference 3, Reference 3 and Reference 4 define various methods of different levels henceforth referred to as data transmission methods (level 0 . . . 3). A first data transmission method (level 0) (corresponding to Reference 1), which every device must have implemented; a second data transmission method (level 1)(corresponding to Reference 2); a third data transmission method (level 2); and a fourth data transmission method (level 3). The error robustness, that is, the level of the method with respect to error protection (error detection, or error correction), rises from the first transmission method (level 0) to the fourth transmission method.
Every device that functions according to the method taught in ITU-T Recommendation H.223
, Multiplexing Protocol for Low-Bitrate Multimedia Communication
1996 therefor; must be able to guarantee at least the first data transmission method (level 0). The additional data transmission (level 0 . . . 3)methods are optional, which means that different devices can communicate with one another that do not have the same maximal capability of error protection implemented. Problems can arise in this case, since at the beginning of the communication connection it must first be worked out according to which data transmission method the data transmission is to occur (synchronization with a data transmission method).
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method and a communication system for synchronizing two devices with a predeterminable data transmission method from a set of data transmission methods, whereby the synchronization can be accomplished simply and automatically.
This object is achieved in accordance with the present invention in a method for synchronizing two devices with a predeterminable data transmission method from a set of data transmission methods that differ with respect to their error protection for transmitted data, said method comprising the steps of: a first device and a second device respectively exchanging a first synchronization message and a second synchronization message, said first synchronization message having an item of information identifying a data transmission method having a highest-level error protection that can be executed by said first device, said second synchronization message having an item of information identifying a data transmission method having a highest-level error protection that can be executed by said second device; determining said data transmission method of said received first synchronization message at said second device from said received first synchronization message; determining said data transmission method of said received second synchronization message at said first device from said received second synchronization message; forming an additional synchronization message at one of said first and second devices by which said respectively determined data transmission method can be executed, said additional synchronization message identifying said data transmission method that can be executed by both said first device and said second device; sending said additional synchronization message to an other of said first and second devices; determining said data transmission method of said additional synchronization message at said other of said first and second devices from said additional synchronization method; and synchronizing said first device and said second device with said determined data transmission method. This object is also achieved in accordance with the present invention in a communication system for synchronizing two devices with a predeterminable data transmission method from a set of data transmission methods that differ with respect to their error protection for data to be transmitted, said communication system comprising:
a first device; and
a second device connected to said first device,
said first device and said second device respectively for exchanging a first synchronization message and a second synchronization message, said first synchronization message having an item of information identifying a data transmission method having a highest-level error protection that can be executed by said first device, said second synchronization message having an item of information identifying a data transmission method having a high
Kaup Andre
Pandel Jürgen
Wimmer Bernhard
Chin Stephen
Ha Dac V.
Siemens Aktiengesellschaft
Staas & Halsey , LLP
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