Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1997-07-22
2001-01-30
Nguyen, Chau (Department: 2739)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S524000
Reexamination Certificate
active
06181709
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method and apparatus for the enlargement of the range of the transmission channel between functional groups of the ISDN-user interface with reference to an ISDN interface as it is standardized, for example, according to CCITT I.400—ISDN User Network Interface and I.430—Basic User Network Interface. This invention enables the varied ISDN services to be transmitted over long distances with a minimized bandwidth.
BACKGROUND AND OBJECTS OF THE INVENTION
The ISDN (Integrated Services Digital Network), which allows, in addition to speech transmission, the rapid transmission of data, texts, and pictures also enables NT and TE apparatus as well as other distribution nets to be connected at its interfaces. Irrespective of a net-side interconnection of ISDN terminal equipment (TE) or network terminations (NT), the enlargement of the range of the transmission channel between functional groups of the ISDN-user interface with reference to an ISDN interface is of advantage for the transmission of the information of the net over a longer distance. However, the range achievable with traditional means is significantly limited due to the electrical features of the ISDN interfaces and connection ways.
From DE 44 07 214 C1, a technical solution is known which in spite of the restrictions of the physical state existing at the interface of an ISDN-user interface, allows to enlarge the range of the transmission channel between functional groups of the ISDN-user interface. In this solution, the ISDN-specific coded data incoming or, respectively, being required at the ISDN interfaces are converted into binary-coded data on the net (or network; as used herein, net refers to network) side as well as on the terminal side. The binary-coded data are grouped into blocks and directed to a transmission means to be corresponded on the net- or terminal-side, respectively. Due to the standardized structure of, for example, an ISDN basic terminal with 2×64 kbit/s of the B-channels or 1×16 kbit/s of the D-channel and the necessary signaling and control information the transmission means transmits, according to DE 44 07 214 C1, information with a bandwidth of 160 kbit/s, which is a considerable and expensive bandwidth of the data transmission via, for example, a satellite channel. Data transmission, particularly via satellite channels, considerably demands reduced bandwidths or, respectively, exactly defined bandwidths of, for example, 64 or 128 kbit/s. A number of satellite services run terminals with 64 kbit/s channels.
Therefore, it is the object of the invention to create a method and apparatus which allow the range of the transmission channel between functional groups of the ISDN-user interface in relation to an ISDN interface to be extended under the condition of a minimized bandwidth. This is achieved maintaining all ISDN-specific features, such as
maintenance of the network timing
multiple access to the interface bus
activation and deactivation of the interface.
SUMMARY OF THE INVENTION
According to the invention, the problem of the enlargement of the range of the transmission channel between functional groups of the ISDN-user interface in relation to an ISDN interface with a minimized bandwidth is solved by a method in which
a) the data transmission on the net side is performed in such a way that the ISDN-specific coded data incoming at an ISDN interface are converted by means of a code converter into binary-coded data separatedly for B- and D-channel information,
b) the data of the B-channels are separated for B
1
- and B
2
-channel data, sections of equal length for the B
1
- and the B
2
-channel data are provided in a buffer device, and are then fed with a bit timing derived from the ISDN network timing with the B
1
- and B
2
-channel data alternating, to the receiver side in which process the data coming from the buffer device are checked for data identity and are compressed,
c) blocks are formed from the incoming data of the D-channel and are fed to the transmission means to transmit them to the receiver side instead of the B-channel data preferably with the bit timing derived from the ISDN network timing,
d) the ISDN-specific timings required for the communication of the transmitter and receiver are regained on the terminal side be means of a timing recovery device from the time sequence of the transmitted data bits,
e) the received data are analysed, identified D-channel blocks are resolved and directly fed to a code converter, and identified B-channel data are decompressed and buffered separatedly for B
1
- and B
2
-channel data and are fed to the code converter in accordance with the regained timing, and the binary-coded data are converted into ISDN-specific data,
f) on the terminal side, the data transmission is performed similarly to the process steps a) to c) with a timing of the process steps b) and c) equal to the timing regained in process step d), and
g) on the network side, the received data are analysed, identified D-channel blocks are resolved and directly fed to a code converter, and identified B-channel data are decompressed and buffered separatedly for B
1
- and B
2
-channel data and are fed to the code converter in accordance with the ISDN network timing, and the binary-coded data are converted into ISDN-specific data.
The compression or decompression, respectively, of the B-channel data according to the process step b) is preferably performed such that during compression, identical characters are provided with a repetition counter and a flag, and during decompression character sequences marked that way are resolved.
Advantageously, in those periods of time in which no B
1
- and/or B
2
-channel is used for the transmission, no B-channel data are fed to the transmission means. If, for example, only one B-channel is active, only the B-channel data of the active B-channel are processed. Hence, the data rate required in the transmission means is reduced to the data rate of the active B-channel.
The natural variations of the required data rate for the transmission of the B- and D-channel information and the compression information are leveled out during data transmission by intermediately buffering the transmitted binary-coded data in a FIFO-structured buffer device of suitable depth on the terminal- or network side. By the process according to this invention, the bandwidth required for the data transmission can advantageously be reduced to the net data rate of the B-channels to be transmitted.
To carry out the compression the character repetitions occurring in the B
1
-channel and B
2
-channel data stream are utilized. If such character repetitions are identified, an accordingly labeled compression block is formed for the appropriate channel, which block contains an information about the number of the identical data within the output stream. A compression block is formed also in case the data stream would not be reduced by the compression. This block ensures the byte boundary synchronization of the B-channel data stream. Advantageously, on process step b) B-channel sections of fixed length are formed and transmitted with a minimum length of the D-channel blocks and B-channel compression blocks is one quarter of the B-channel sections and the D-channel blocks can have a multiple of the minimum length.
If D-channel blocks and B-channel compression blocks are formed, the transmission of the B-channel sections is interrupted, and instead of the B-channel sections these blocks are fed to the transmission means to be transmitted to the receiver side with the transmission of the D-channel blocks being preferred. Advantageously, the transmission of the B-channel sections is interrupted at a place divisible by 4.
The formed B-channel sections are transmitted to the receiver side having a timing derived from the ISDN network timing, by means of known transmission means via satellite or other transmission channels. This bit timing is regained on the terminal side from the bit transmission timing by means of a PLL circuit (phase locked l
Helbig Klaus
Wulst Norbert
DICA Technologies AG
Hyun Soon-Dong
Nguyen Chau
Robert W. Becker & Associates
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