Error detection/correction and fault detection/recovery – Pulse or data error handling – Digital data error correction
Reexamination Certificate
2001-01-03
2003-09-02
Tu, Christine T. (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Digital data error correction
Reexamination Certificate
active
06615386
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an error correcting apparatus and, more particularly, to an error correcting apparatus which receives a signal subjected to a repetition processing for repeatedly transmitting a part of bits of an error-correction code train, and which restores the received signal to the original data train by subjecting the signal to a repetition regeneration processing and an error correcting decoding processing.
An error-correction coding technique is adopted so as to correct an error contained in received information or regenerated information and to restore it to the correct original information. Various codes such as a convolutional code and a turbo code are known as an error-correction code, and the error-correction coding technique is applied to various systems. In CDMA mobile communication, for example, an error-correction encoder
1
subjects information to be transmitted to an error-correction encoding processing, and a CDMA transmitter
2
subjects the code obtained with an error-correction code to a spread modulation processing and transmits it from an antenna, as shown in FIG.
12
A. On the other hand, on the reception side, a soft decision error-correction decoder
4
subjects a soft decision data train obtained by the despreading operation and the RAKE combining operation of a CDMA receiver
3
to an error-correction processing, decodes the data and outputs the original transmitted information before the error-correction encoding processing, as shown in
FIG. 12B. A
soft decision data a 1-bit data represented by a plurality of bits depending upon the level.
FIG. 13
shows the structure of a CDMA transmitter in a mobile station. The error-correction encoder
1
subjects a data to be transmitted to an error-correction encoding processing and inputs it into a mapping portion
21
. A control data generator
22
generates a control data such as a pilot PILOT and inputs it into the mapping portion
21
. The mapping portion
21
outputs an error-correction code as an in-phase component data, and the control data as quadrature component respectively for quadrature modulation at a constant symbol rate. Spreaders
23
a
,
23
b
subject the in-phase (I) component and the quadrature (Q) component which are input from the mapping portion
21
to spreading modulation by using a predetermined spreading code, and input the spread data into DA converters
25
a
,
25
b
, respectively, via waveform shaping filters
24
,
24
b
. A QPSK quadrature modulator
26
subjects an I
ch
signal, and a Q
ch
signal output from each DA converter to QPSK quadrature modulation, and a radio transmitter
27
converts the frequency of a baseband signal output from the quadrature modulator
26
into a radio frequency (IF→RF), amplifies the frequency, and transmits the signal from an antenna.
FIG. 14
shows the structure of a CDMA receiver
3
for 1 channel in a CDMA receiving apparatus at a base station. A radio receiver
31
converts the frequency of a high-frequency signal received from an antenna into a frequency of a baseband signal (RF→IF). A QPSK quadrature detector
32
subjects the baseband signal to quadrature detection and outputs an in-phase (I) component data and a quadrature (Q) component data. In the quadrature detector
32
, the reference numeral
32
a
denotes a receiving carrier generator,
32
b
a phase shifter for shifting the phase of a receiving carrier by &pgr;/2, and
32
c
and
32
d
multipliers for multiplying a baseband signal by a receiving carrier and outputting an I component signal and a Q component signal. Low-pass filters (LPF)
33
a
,
33
b
limit the band of an output signal, and AD converters
35
a
,
35
b
convert an I component signal and a Q component signal, respectively, into digital signals, and input them into a searcher
36
and each of the finger portions
37
a1
to
37
a4.
When a direct sequence signal (DS signal) influenced by a multi-path is input into the searcher
36
, the searcher
36
detects the multi-path by an autocorrelation operation using a matched filter (not shown), and inputs the data on the timing for starting the despreading operation and the data on the delay time adjustment in each path constituting the multi-path into the corresponding finger portions
37
a1
to
37
a4
. A despreading/adjustment time adjuster
41
of each of the finger portions
37
a1
to
37
a4
subjects a direct wave or a delayed wave which reaches via a predetermined path to a dispreading processing by using the same code as the spreading code for the purpose of dump integration, thereafter subjects it to a delay processing in accordance with the path and outputs a pilot signal (reference signal) and an information signal. A phase compensator (channel estimation unit)
42
averages the voltages of the I components and the Q components of the pilot signals for a predetermined number of slots, and outputs channel estimation signals I
t
, Q
t
. A synchronous detector
43
restores the phases of the despread information signals I′, Q′ to the original phases on the basis of the phase difference &thgr; between the pilot signal contained in the received signal and a known pilot signal. That is, since the channel estimation signals I
t
, Q
t
are the cos component and the sin component of the phase difference &thgr;, the synchronous detector
43
demodulates (executes synchronous detection of) the received information signals (I, Q) by applying a phase rotation processing to the received information signals (I′, Q′) by using the channel estimation signals I
t
, Q
t
in accordance with the following formula:
(
I
Q
)
=
(
I
t
Q
t
-
Q
t
I
t
,
)
(
I
′
Q
′
)
A Rake combiner
37
b
combines the signals output from the finger portions
37
a1
to
37
a4
, and outputs the combined signals to the soft decision error-correction decoder
4
(
FIG. 12
) as a soft decision data train.
FIG. 15
is an explanatory view of the frame format of an up signal transmitted from a mobile station to a base station. 1 frame is 10 msec and it is composed of 15 slots S
0
~S
14
. The data portion is mapped in an orthogonal I channel for QPSK quadrature modulation, and the portions other than the data portion are mapped in an orthogonal Q channel for QPSK quadrature modulation. The channel transmitting the data portion is called a DPDCH (Dedicated Physical Data Channel), and the channel transmitting the portions other than data is called a DPCCH (Dedicated Physical Control Channel). Each slot of the DPDCH (I channel) transmitting the data portion is composed of n bits, and n changes in accordance with a symbol rate.
FIG. 16A
shows the relationship among the symbol rate (ksps), the number n of bits per slot, and the data length Nm (=15×n) per frame in the data channel DPDCH. The data channel DPDCH multiplexes and transmits the data in more than 1 transport channels. For example, the data channel DPDCH divides sound data into a sound data portion with a high degree of importance and a sound data portion with a low degree of importance, allocates a predetermined number of bits per frame to the respective sound data, multiplexes and transmits the data in different transport channels.
Each slot of the DPCCH (Q channel) for transmitting a control data is composed of 10 bits (see FIG.
15
), and transmits a pilot PILOT, a transmission power control data TPC, a transport format combination indicator TFCI, and feedback information FBI at a constant symbol rate of 15 ksps. It is possible to change the number of bits of PILOT, TPC, TFCI, and FBI as occasion demands, as shown in FIG.
16
B. PILOT is utilized when the reception side performs synchronous detection or measures a signal interference ratio SIR, TPC is utilized for the control of a transmission power, TFCI indicates the symbol rate or the number of bits per frame of data, the number of bits of data which increases by repetition, etc., and FBI is used to control the diversity transmission in the base station.
FIGS. 17A and 17B
are
Obuchi Kazuhisa
Yano Tetsuya
Fujitsu Limited
Katten Muchin Zavis & Rosenman
Tu Christine T.
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