Pulse or digital communications – Multilevel
Reexamination Certificate
1999-04-06
2003-06-10
Chin, Stephen (Department: 2634)
Pulse or digital communications
Multilevel
C375S264000
Reexamination Certificate
active
06577684
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to transmission methods and more specifically to a method for transmitting a well direct-current (hereinafter referred to as DC) balanced multilevel code through a transmission path.
2. Description of the Background Art
In transmission devices, a transmitting end transmits data to be transmitted to a receiving end to a transmission path. The transmitting end may further transmit a command to the transmission path to instruct the receiving end to execute a predetermined operation. The data and the command may be multiplexed and transmitted as various types of information, as shown in FIG.
11
. In a symbol string
111
of
FIG. 11
, COM
112
and COM
113
are symbols of commands. DATA
114
is a symbol of data.
When the transmitting end continuously transmits COM
112
of
FIG. 11
, the average value of the signal scintillates depending on the characteristics of the transmission path. That is, the transmission path cannot correctly transmit a signal with the same successive codes. Therefore, transmission path codes are adopted for the transmission device. The transmitting end converts a symbol (command or data) with excessively successive identical codes into a symbol with different codes moderately mixed according to predetermined encoding rules. Such encoding allows transmission of a well DC balanced signal to the transmission path.
One of the types of transmission path encoding is disclosed in U.S. Pat. No. 4,530,088. This patent discloses the so-called 4B5B encoding. Described below is the 4B5B encoding referring to FIG.
12
. An encoding portion
121
of
FIG. 12
is provided at a transmitting end. To the encoding portion
121
, DATA
114
COM
112
or COM
113
of
FIG. 11
are inputted. Data to be transmitted by the transmitting end is generated, being divided into four-bit blocks. Therefore, DATA
114
of four bits is represented as any one of 16 (=2
4
) types of symbols. When two commands of COM
112
and COM
113
are to be transmitted, each of them represents only one symbol even though they are divided in blocks with a length corresponding to four bits. That is, the transmitting end can transmit 18 types of symbols in total as to DATA
114
COM
112
and COM
113
to the receiving end.
In 4B5B encoding, of 32 types of symbols represented with five bits, 18 types of symbols having good DC balance are preselected. The selected symbols of five bits are assigned to the symbols of four bits, thereby determining 4B5B encoding rules.
As shown in FIG.
13
(
a
), the encoding portion
121
waits until the whole symbol of four bits (COM
112
, COM
113
or DATA
114
) is inputted. The encoding portion
121
encodes based on the 4B5B encoding rules, thereby converting the symbol of four bits to a symbol of five bits (represented as “Xcode” in the drawing)
115
. This symbol of five bits
115
is transmitted through the transmission path to the receiving end. The receiving end is provided with a decoding portion, which, as shown in FIG.
13
(
b
), waits until the whole symbol of five bits
115
is inputted. The decoding portion decodes based on the 4B5B encoding rules, and thereby restores the symbol of five bits
115
to its original symbol of four bits (DATA
114
, etc.).
As described above, even when a poorly DC balanced signal string is generated at the transmitting end, adopting the transmission path codes allows a well DC balanced signal string to be transmitted to the transmission path. Therefore, information can be transmitted correctly between the transmitting end and the receiving end. Furthermore, it is also possible in the 4B5B encoding to multiplex a plurality of types of information (typically, command and data).
However, in the 4B5B encoding, the transmitting and receiving ends have to wait until the whole symbols of four bits and five bits are completely inputted. As a result, transmission delay in encoding and decoding is caused. Therefore, in a data transmission device with limited transmission delay, it is disadvantageously impossible to make time for processing of converting a signal string into a well DC balanced signal string.
Note that in the above U.S. patent, the signal string of four bits is inputted in parallel into the encoding portion
121
and the signal string of five bits is outputted in parallel from the encoding portion
121
. However, the front end of the encoding portion
121
performs serial-parallel conversion, in which transmission delay occurs. That is, in the conventional transmission path encoding, the above transmission delay occurs in any part of the processing.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to a transmission method and a transmitting/receiving device capable of multiplexing various types of information and transmitting the information with small transmission delay. The object of the present invention is achieved by the following first to fortieth aspects.
A first aspect is directed to a method for transmitting multilevel codes represented by a plurality of amplitude values from a transmitting end to a receiving end through a transmission path. The method includes, at the transmitting end, encoding information to be transmitted to the receiving end according to encoding rules defined based on a relation between a previously-generated multilevel code and a currently-generated multilevel code, generating a multilevel code string, and transmitting the generated multilevel code string to the transmission path. The method also includes, at the receiving end, receiving the multilevel code string through the transmission path, decoding the received multilevel code string according to decoding rules corresponding to the encoding rules based on a relation between a currently-received multilevel code and a previously-received multilevel code, and reproducing the information.
In accordance with the first aspect, the transmitting end encodes information based on a relation between a previous multilevel code and the current multilevel code, and transmits to the receiving end. That is, unlike in the 4B5B encoding method, the transmitting end of the present invention can encode information without waiting until the whole block of four bits is completely inputted, thereby allowing short processing time from occurrence of information to be transmitted to the end of encoding in the transmitting end. On the other hand, the receiving end can decode and reproduce the information from the transmitting end based on the currently-received multilevel code and a previously-received multilevel code. That is, unlike in the 4B5B encoding method, the receiving end can decode and reproduce information without waiting until the whole block of five bits is completely inputted, thereby allowing a short processing time from the time when the multilevel codes are received to the end of decoding in the receiving end. Therefore, according to the transmission method of the first aspect, it is possible to transmit information with a small amount of delay.
Further, in accordance with the first aspect, the transmitting end converts transmission information to multilevel codes. The multilevel codes can create a large number of relationship patterns of combination between a previous multilevel code and the current multilevel code. It is therefore possible to assign different amplitude value patterns to various types of information, thereby allowing transmission and multiplexing of various types of information with a small amount of delay.
According to a second aspect, in the first aspect, the transmitting end encodes the information according to encoding rules defined based on a relation between a currently-generated multilevel code and a multilevel code generated immediately before and the receiving end decodes based on a relation between the currently-received multilevel code and a multilevel code received immediately after.
In accordance with the first aspect, the transmitting end and the receiving end have to latch the amplitude values of previou
Furusawa Satoshi
Hirano Jun
Morikura Susumu
Chin Stephen
Fan Chieh M.
Matsushita Electric - Industrial Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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