Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1998-08-11
2001-12-04
Patel, Ajit (Department: 2732)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C375S340000, C714S758000
Reexamination Certificate
active
06327262
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a DSS (Distributed Sample Scrambling) system for scrambling and descrambling, and more particularly to a sample value extraction apparatus in the descrambling part which extracts two sample values from received data in order to synchronize PRBS data (Pseudo Random Binary Sequence) which are in the scrambler and descrambler each other.
2. Description of the Conventional Art
Generally, the DSS system is adopted for use in the cell-based physical layer of BISDN (Broadband Integrated Service Digital Network) by CCITT (International Telegraph and Telephone Consultative Committee). This system is composed of a scrambler and a descrambler, randomizing data. Therefore, in the scrambler, The PRBS data is generated and exclusively ORed with the data inputted. In addition, two sample values are latched from the PRBS data at a uniform interval. That is, One sample value is latched at the uniform interval too. And these two latched sample values are transmitted via scrambled data, inserting them in the HEC
8
and HEC
7
each.
In the descrambler, using the transmitted sample values, the descrambler PRBS data is corrected and become identical to the scrambler PRBS data state. Therefore this descrambler PRBS data is added to the scrambled data and the descrambled data is obtained.
For example, in the case of the scrambling of the transmitter, if an input data is formed of “111110101”, and the scrambler PRBS data is formed of “110101000”, then the scrambled data is formed of “001011101”.
In addition, in the case of the descrambling of the receiver, if the input data that is, received data is formed of “001011101”, and the descrambler PRBS data is formed of “110101000”, then the descrambled data is formed of “111110101” for thereby performing a binary arithmetic operation of 0 or 1 in accordance with the resultant data.
In the above-described DSS operation, PRBS data of the scrambler and the descrambler is generated, based on a creative polynomial expression of X
31
+X
28
+1, and the scrambling range is a header (4 bytes) and a payload (48 bytes) except for an HEC (1 byte).
In the sample latch method of transmitter, the sample value is latched from the PRBS data of the scrambler at every 212 bit through a 212 counter. And two sample values are inserted into the scrambled data HEC
8
and HEC
7
.
As shown in
FIG. 1
, the conventional transmitter includes a scrambler
1
having a PRBS data generator
2
for generating a PRBS data, and an exclusive OR-gate
3
for exclusively ORing the PRBS data from the PRBS data generator
2
and an input data from the exclusive OR-gate
3
, a HEC encoder
4
for encoding an output signal from the scrambler
1
, and a sample value latching unit
6
for latching the sample value from the PRBS data generator
2
, and an exclusive OR-gate
5
for exclusively ORing an output signal from the HEC encoder
4
and a sample value latched from the PRBS data generator
2
.
FIG. 2
illustrates a part of PRBS data from the PRBS data generator
2
. As shown in
FIG. 1
, the scrambler
1
performs a scrambling operation through entire input cell data interval except for an HEC 8-bit interval (HEC
1
-HEC
8
), as shown in FIG.
3
.
The scrambled data are CRC-computed with respect to 32 bits from a start point of a cell by the HEC encoder
4
, and the 8 bits which are the resultant value is inserted into the HEC 8 bit interval.
Next, two sample values (U
t+1
and U
t−211
), which are obtained by the sample value latching unit
6
by latching the PRBS data from the scrambler
1
by one bit at the interval of 212 bits are exclusively ORed in the HEC eighteenth interval and the HEC seventh interval for thereby transmitting the data.
Namely, two sample data are latched by the one cell which is formed of 424 bits, and such the latched two sample data are exclusively ORed for thereby generating a transmission data as shown in FIG.
3
. Here, U
t
represents the PRBS data generated at a current time, U
t+1
represents data after U
t
, U
t−211
represents data which is 211st earlier than U
t
, and HEC
8
, HEC
7
, . . . , HEC
1
are all 8-bits which are generated by CRC-computing 32-bit, namely, 4-byte.
Therefore, the PRBS data of the scrambler and the input data are exclusively ORed from the start point of the cell by one bit, and in the HEC interval, two sample values are exclusively ORed after the HEC 8-bit signal which is obtained by CRC-computing 32-bit data is inputted.
However, in the conventional art, the sample value from the transmitter is included in the receiving data. In addition, a method for extracting the above-described values in the descrambler is not disclosed.
In the descrambler of DSS system, key issue is to generate the PRBS data, which is identical to the PRBS data of the scrambler. So first, it is need to extract the sample values, which are transmitted via the input data.
Therefore, this invention is derived to resolve the above disadvantages and presents a method of catching the sample values in the descrambler in order to gain synchronization for the scrambler PRBS data and the descrambler PRBS data.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a novel sample value extraction apparatus in a DSS system which overcome the aforementioned problems encountered in the conventional art.
It is another object of the present invention to provide a novel sample value extraction apparatus in a DSS system, which is capable of easily extracting a sample value when synchronizing a descrambler PRBS data in a receiver using a sample value from a transmitter.
In order to achieve the above objects, there is provided a sample value extraction apparatus which includes a HEC decoder for decoding a data from a receiver, a sample value extraction part for extracting a sample value using a CRC calculation based on data received, and a descrambler for descrambling data stream from a transmitter and the sample value extraction part.
In order to achieve the above objects, there is provided a sample value extraction method which includes the steps of performing one more the operation that a CRC calculation which is performed in a receiver with respect to the first 4 bytes using a CRC regeneration circuit when a data received is processed by a HEC decoder, and exclusively ORing the first bit on which a sample value among the next 1 byte of the 4 bytes is carried and the second bit.
Additional advantages, objects and other features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.
REFERENCES:
patent: 5638408 (1997-06-01), Takaki
patent: 5784409 (1998-07-01), Coles
patent: 6126310 (2000-10-01), Osthoff et al.
patent: 6161207 (2000-12-01), Lockhart et al.
Hyundai Electronics Inds. Co. Ltd.
Nissen J. Harold
Patel Ajit
Phunkulh Bob A.
Siegel Lackenbach
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