Pulse or digital communications – Receivers – Particular pulse demodulator or detector
Reexamination Certificate
1999-03-19
2003-09-09
Pham, Chi (Department: 2731)
Pulse or digital communications
Receivers
Particular pulse demodulator or detector
Reexamination Certificate
active
06618450
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a receiving apparatus for and receiving method of receiving a digitally modulated digital signal, and more specifically to a receiving apparatus for and receiving method of receiving a digital signal in which real data and information indicating a transfer method therefor are multiplexed therein and decoding the real data step by step while decoding the transfer system.
BACKGROUND OF THE INVENTION
The history of development in the field of integrated circuits enabling high speed processing of digital data and a coding technology in recent years indicates a trend of shifting of technology from an analog system to that based on a digital system. Especially, the trend is remarkable in the field of telecommunications, and services such as television broadcasting or satellite broadcasting are now shifting to those based on the digital system.
In a case of the digital broadcasting, the digitizing processing is executed to a signal indicating service information, and the resultant digital data is transferred. Among them, in the digital satellite broadcasting a carrier wave is modulated using digital data indicating contents of information to be transferred (digital modulation), the resultant signal is transmitted via a satellite and is directly received by a receiver installed in each house.
In a case where a signal subjected to digital modulation is transferred by means of cable communication, sometimes the signal can not accurately be received due to a quality of the transfer path, a transfer distance, or noise environment around the transfer path. On the contrary in a case where a modulated signal is transferred through a radio system like in the television broadcasting, because electric waves are used as carrier waves a quality of a transfer space as a transfer path becomes lower due to the influence of the climate or the like and sometimes the receiving conditions become worst.
To execute the modulation/demodulation with high reproducibility in transmitting and receiving signals and to overcome the problems as described above, in the radio communication, whether it be an analog or a digital communication system it is necessary to divide the radio frequency band to narrower frequency bands in order to realize a plurality of communication paths and to use each band area as one communication path.
Like in a case of the digital satellite broadcasting as described above, when a digitally modulated signal is transmitted through radio communications, as higher reproducibility is required for each bit constituting the digital data, generally to provide redundancy in transmission, the digital data to be digitally modulated is encoded with redundancy added to the real data. In the following description, digital data obtained by means of encoding the real data is defined as a data stream.
When redundancy of the digital data is increased its error correction capability is improved. Namely, even if a data stream with high redundancy includes many error bits in receiving, the error bits can be corrected, and the data stream can correctly be reproduced in transmission. At the same time, the data stream with high redundancy as described above has redundancy data added to the real data and the amount of data increases so that the transmission efficiency becomes disadvantageously lower.
For instance, when information such as an image or voice is transferred as a data stream including a few errors, the information is acceptable even if the data stream is disturbed a little in receiving, so that the information may be transferred by lowering the redundancy to a relatively low level to raise the transfer efficiency. On the other hand, in a data stream expressing a computer program or the like in which it is not admissible to have an error of even one bit, accurate reproduction of the information is required in receiving by raising the redundancy to a relatively high level.
As described above, even in a case of digital data with redundancy added to the real data, it is recognized simply as a bit array in receiving, and the redundancy included in the data stream can not be extracted. Therefore, information indicating what type of redundancy is included in which section of a multiplexed data (data configuration control signal) is further added to the data stream in transmission.
This data configuration control signal is generally called as TMCC (Transmission & Multiplexing Configuration Control), and the term TMCC signal is used also in the following description.
In a receiving apparatus for receiving a digital signal in which a data stream and a TMCC signal are multiplexed, the TMCC signal must accurately be received without fail to recognize redundancy of the data stream according to information indicating the TMCC signal and also to execute decoding processing for extracting and correcting real data from the data stream. Redundancy given to this TMCC signal is set to a relatively high level and also the redundancy is previously obtained in the receiving apparatus which insures recognition of the TMCC signal.
FIG. 1
is a block diagram showing general configuration of a transmitter based on the conventional technology.
FIG. 1
especially shows an example of a transmitter for digital satellite transmission. In
FIG. 1
, the transmitter comprises an outer coding error control signal adding circuit
101
for encoding input signals TS
1
, TS
2
, . . . (described as input signal TS hereinafter), a frame forming circuit
102
, an energy dispersal circuit
103
, an interleaver
104
, an inner coding error control signal adding circuit
105
, a TMCC signal generating circuit
106
for encoding a TMCC signal, an outer coding error control signal adding circuit
107
, an energy dispersal circuit
108
, an inner coding error control signal adding circuit
109
and a modulating circuit
110
.
It should be noted that, in
FIG. 1
, the input signal TS as an example of digital data is a digital data stream (transport stream) compressed by MPEG2 (Motion Picture Expert Group 2) which is one of the motion picture compressing systems. In this case, multiplexing means that, when 8 types of input signals TS
1
to TS
8
each indicating different information contents (such as programs provided by broadcasting stations), a data stream comprising an array of these input signals TS
1
to TS
8
is transferred using one carrier wave.
At first, a TMCC signal as transfer information for the input signal TS is generated in the TMCC signal generating circuit
106
. The transfer information for the input signal TS indicates a position (timing) of each of the input signals TS multiplexed on a carrier wave and the transfer system (including the redundancy or the like).
The input signal TS is first inputted to the outer coding error control signal adding circuit
101
. The outer coding error control signal adding circuit
101
is a circuit for adding a redundancy signal (an outer coding error control signal) enabling correction of an error byte by byte in a receiving apparatus to each input signal TS and outputting the added signal (described as input signal TS′ hereinafter). Namely, the outer coding error control signal adding circuit
101
is a circuit for adding redundancy to the input signal TS, and for instance the Reed Solomon encoding system is used for encoding the input signals TS.
The input signal TS′ outputted from the outer coding error control signal adding circuit
101
is inputted into the frame forming circuit
102
. The frame forming circuit
102
is a circuit for forming a frame as a multiplexed data unit by multiplexing each input signal TS′ according to the transfer information indicated by a TMCC signal outputted from the TMCC signal generating circuit
106
.
A signal outputted from the frame forming circuit in the units of frame is inputted into the energy dispersal circuit
103
. The energy dispersal circuit
103
is a circuit for adding (scrambling) a pseudo random signal (an energy dispersal signal) to the digital data so that digital d
Bayard Emmanuel
Fujitsu Limited
Pham Chi
Staas & Halsey , LLP
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