Pulse or digital communications – Receivers – Particular pulse demodulator or detector
Reexamination Certificate
2001-01-18
2004-10-26
Chin, Stephen (Department: 2634)
Pulse or digital communications
Receivers
Particular pulse demodulator or detector
C375S232000, C375S347000
Reexamination Certificate
active
06810096
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a reception apparatus and replica signal generating method, and more particularly, to a reception apparatus and replica signal generating method that adaptively updates tap coefficients of an array combining section and of an equalizer.
BACKGROUND ART
A conventional reception apparatus updates tap coefficients of an array combining section and of an equalizer adaptively, and thereby cancels interfering signal components and compensates for a distortion of a received signal generated on a propagation path. An example of the conventional reception apparatus is disclosed in Japanese Laid Open Patent Publication HEI10-336083.
The conventional reception apparatus is explained below using
FIGS. 1
to
6
.
FIG. 1
is a partial block diagram illustrating a schematic configuration of the conventional reception apparatus.
FIG. 2
is a partial block diagram illustrating a schematic configuration of a plural array combining section in the conventional reception apparatus.
FIG. 3
is a partial block diagram illustrating a schematic configuration of a propagation path estimating section in the conventional reception apparatus.
FIGS. 4A
to
4
D illustrate one example of a delay profile.
FIG. 5
is a partial block diagram illustrating a schematic configuration of a Viterbi equalizer in the conventional reception apparatus.
FIG. 6
is a partial block diagram illustrating a schematic configuration of a replica generating section in the conventional reception apparatus.
The entire configuration of the conventional reception apparatus is first explained using FIG.
1
. In
FIG. 1
, plural array combining section
12
has processing systems, of which the number is the same as that of antennas, which combine signals received at respective antennas
11
, and further combines resultants weighted and then combined for each antenna.
Timing control section
13
acquires symbol synchronization timings from outputs of reception processing sections provided for each antenna in plural array combining section
12
. In addition, timing control section
13
is capable of acquiring a symbol synchronization timing from an output from one of the reception processing sections.
Propagation path estimating section
14
estimates a delay profile from outputs of the reception processing sections provided for each antenna in plural array combining section
12
, and recognizes a spread condition of received signal components on the time axis. That is, propagation path estimating section
14
performs propagation path estimation. In order to converge the spread of received signal components in a range enabling delay compensation in Viterbi equalizer
16
described later, propagation path estimating section
14
calculates a time adjustment amount (&tgr; shown in
FIG. 4D
) for a delayed wave to output to time adjustment section
22
in plural array combining section
12
. Propagation path estimating section
14
is capable of performing the propagation path estimation from an output from one of the reception processing sections.
Tap coefficient estimating section
15
estimates a coefficient that minimizes a mean square of an error between a replica signal and a received signal (i.e., a weight based on the least square method), and outputs the estimated coefficient to feed forward filter (FFF)
23
in plural array combining section
12
and replica generating section
56
in Viterbi equalizer
16
. The coefficients are used in FFF
23
and multipliers
65
to
69
in replica generating section
56
.
Viterbi equalizer
16
generates the replica signal, and makes a decision on the received signal using the Viterbi algorithm with the difference between a received signal component subjected to array combining and the replica signal as likelihood information.
A configuration of plural array combining section
12
is next explained using FIG.
2
. While a case is explained herein, for example, where the number of array elements is
2
, and the number of path groups is
2
, any numbers of array elements and of path groups may be applicable.
In
FIG. 2
, reception processing sections
21
perform reception processing on received signals from respective antennas. Time adjustment section
22
delays a reception-processing processed received signal based on an output from propagation path estimating section
14
. FFF
23
performs weighting processing on the received signal based on the tap coefficient designated from tap coefficient estimating section
15
. Combining section
24
combines all the FFF processed signals of respective paths from all antennas.
A configuration of propagation path estimating section
14
is next explained using FIG.
3
. In
FIG. 3
, delay profile estimating section
31
estimates a delay profile of received signals components. An example of the delay profile is illustrated in FIG.
4
A. In addition, in order to estimate a delay profile it may be possible to use the correlation value of a received signal with a known signal, or to use an impulse response value.
Maximum detecting section
32
detects a maximum level among power levels of the received signal components spread on the time axis in the estimated delay profile. Based on the maximum level of the power, threshold setting section
33
sets a threshold level to select only a path with excellent received condition. Any method may be applicable to determine the threshold level, for example, there is considered a method of obtaining predetermined percentages of the maximum level, or of subtracting a predetermined value from the maximum level. The delay profile with the threshold level set is illustrated in FIG.
4
B.
Extracting section
34
extracts only a path with a received power level exceeding the threshold level set by threshold setting section
33
. The delay profile with extracted paths is illustrated in FIG.
4
C.
Classifying section
35
classifies the extracted paths into groups (groups of paths). The classification is performed so that the number of states in the Viterbi algorithm becomes as small as possible in consideration of a maximum delay time enabling compensation in Viterbi equalizer
16
.
For example, in
FIG. 4C
, a delay time of a component having the greatest delay among extracted paths is
6
T. Assuming herein that the maximum delay time enabling compensation in Viterbi equalizer
16
is up to
4
T delay, when a received signal with the delay profile as illustrated in
FIG. 4C
is input to Viterbi equalizer
16
without any time adjustment, reception performance deteriorates largely due to an effect of the delayed wave beyond a compensation range.
Then, when a group is determined for each
3
T delay interval (every 4 components), as illustrated in
FIG. 4D
, two groups of group A and group B are set. When time adjustment section
22
performs time adjustment on these groups later, since the delay time of the greatest delay component is
3
T, signals of the groups can be efficiently equalized in Viterbi equalizer
16
capable of compensating up to
4
T delay signal.
Further, when a received signal component group in which the delay time of the greatest delay component is
3
T is input to Viterbi equalizer
16
capable of compensating up to
4
T delay signal, the number of states in the Viterbi algorithm equals 4
3
=64, for example, at the time the modulation scheme is QPSK. The smaller the number of states is, the smaller the calculation amount is, and the more the processing rate is increased. Accordingly, in order to decrease the calculation amount, classifying section
35
may set the number of states to be as small as possible by determining a group for each delay time interval that is as small as possible in a range allowed by a spread condition of received signal components exceeding the threshold level. In addition, the number of groups is not limited to 2, and is determined arbitrarily.
Time adjustment amount detecting section
36
detects a time adjustment amount. That is, based on the classification result, time adjustment amount detecting section
36
Saito Yoshiko
Uesugi Mitsuru
Chin Stephen
Stevens Davis Miller & Mosher LLP
Ware Cicely
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