U.S. patent application number 10/571129 was filed with the patent office on 2007-07-12 for signal transmitting method and transmitter in radio multiplex transmission system.
This patent application is currently assigned to NTT DoMo , Inc.. Invention is credited to Takahiro Asai, Kenichi Higuchi, Junichiro Kawamoto, Mamoru Sawahashi.
Application Number | 20070162819 10/571129 |
Document ID | / |
Family ID | 34269853 |
Filed Date | 2007-07-12 |
United States Patent
Application |
20070162819 |
Kind Code |
A1 |
Kawamoto; Junichiro ; et
al. |
July 12, 2007 |
Signal transmitting method and transmitter in radio multiplex
transmission system
Abstract
A disclosed signal transmission method in a radio multiplex
transmission system comprises the steps of: serial-to-parallel
converting serial data to be transmitted into N (N: two or more)
parallel data series; independently performing an error-correcting
encoding process on the parallel signals of the N data series
serial-to-parallel converted; parallel-to-serial converting the
parallel signals encoded with error-correcting codes; performing an
interleaving process on the parallel-to-serial converted signals;
serial-to-parallel converting the interleaved signals into L (L:
two or more) parallel data series and transmitting each of the L
data series using L antennas; receiving the transmitted signals;
separating the received signals into M (M: two or more) data series
and parallel-to-serial converting the M data series; performing a
deinterleaving process on the parallel-to-serial converted signals;
serial-to-parallel converting the deinterleaved signals into N data
series; independently performing an error-correcting decoding
process on the parallel signals of the N data series
serial-to-parallel converted; and parallel-to-serial converting the
signals in which the error-correcting codes are decoded, thereby
recovering the transmitted data.
Inventors: |
Kawamoto; Junichiro;
(Kanagawa, JP) ; Asai; Takahiro; (Kanagawa,
JP) ; Higuchi; Kenichi; (Kanagawa, JP) ;
Sawahashi; Mamoru; (Kanagawa, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
NTT DoMo , Inc.
11-1, Nagatacho 2-chome, Chiyoda-ku
Tokyo
JP
100-6150
|
Family ID: |
34269853 |
Appl. No.: |
10/571129 |
Filed: |
September 7, 2004 |
PCT Filed: |
September 7, 2004 |
PCT NO: |
PCT/JP04/12966 |
371 Date: |
December 26, 2006 |
Current U.S.
Class: |
714/758 |
Current CPC
Class: |
H04L 1/0043 20130101;
H04B 7/0854 20130101; H04L 1/0625 20130101; H04L 1/0071
20130101 |
Class at
Publication: |
714/758 |
International
Class: |
H03M 13/00 20060101
H03M013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 9, 2003 |
JP |
2003-317464 |
Claims
1. A signal transmission method in a radio multiplex transmission
system, the signal transmission method comprising the steps of:
serial-to-parallel converting serial data to be transmitted into N
(N: two or more) parallel data series; independently performing an
error-correcting encoding process and/or an interleaving process on
parallel signals of the N data series serial-to-parallel converted;
transmitting each of the processed signals using a plurality of
transmission antennas; receiving the transmitted signals;
separating the received signals into M (M: two or more) data
series; independently performing a deinterleaving process and/or an
error-correcting decoding process on each of the separated signals;
and parallel-to-serial converting the processed signals, thereby
recovering the transmitted data.
2. A signal transmission method in a radio multiplex transmission
system, the signal transmission method comprising the steps of:
serial-to-parallel converting serial data to be transmitted into M
(M: two or more) parallel data series; independently performing an
error-correcting encoding process on parallel signals of the M data
series serial-to-parallel converted; parallel-to-serial converting
the parallel signals encoded with error-correcting codes;
performing an interleaving process on the parallel-to-serial
converted signals; and serial-to-parallel converting the
interleaved signals into N (N: two or more) parallel data series
and transmitting the N parallel data series using a plurality of
transmission antennas.
3. A signal reception method in a radio multiplex transmission
system, the signal reception method comprising the steps of:
receiving signals transmitted from a transmitter, using a plurality
of antennas; separating the received signals into N (N: two or
more) data series and parallel-to-serial converting the N data
series; performing a deinterleaving process on the
parallel-to-serial converted signals; serial-to-parallel converting
the deinterleaved signals into M parallel data series;
independently performing an error-correcting decoding process on
the parallel signals of the M data series serial-to-parallel
converted; and parallel-to-serial converting the signals in which
error-correcting codes are decoded, thereby recovering the
transmitted data.
4. A signal transmission method in a radio multiplex transmission
system, the signal transmission method comprising the steps of:
performing an error-correcting encoding process on serial data to
be transmitted; serial-to-parallel converting the serial signals
encoded with error-correcting codes into N (N: two or more)
parallel data series; independently performing an interleaving
process on the parallel signals of the N data series
serial-to-parallel converted; and transmitting the
interleaved-signals using a plurality of transmission antennas.
5. A signal reception method in a radio multiplex transmission
system, the signal reception method comprising the steps of:
receiving signals transmitted from a transmitter, using a plurality
of antennas; separating the received signals into L (L: two or
more) data series; independently performing a deinterleaving
process on each of the separated signals; parallel-to-serial
converting the deinterleaved signals; and performing an
error-correcting decoding process on the parallel-to-serial
converted signals, thereby recovering the transmitted data.
6. A transmitter used in a radio multiplex transmission system, the
transmitter comprising: a first serial-to-parallel converter for
inputting serial data to be transmitted and for serial-to-parallel
converting the input serial data into M (M: two or more) parallel
data series; M error-correcting encoders for independently
performing an error-correcting encoding process on the parallel
signals of the M data series output from the first
serial-to-parallel converter; a parallel-to-serial converter for
parallel-to-serial converting the M parallel signals output from
the M error-correcting encoders; an interleaver for performing an
interleaving process on the serial signals output from the
parallel-to-serial converter; a second serial-to-parallel converter
for serial-to-parallel converting the signals output from the
interleaver into N (N: two or more) parallel data series; and a
plurality of transmission antennas for transmitting the N parallel
signals output from the second serial-to-parallel converter.
7. A transmitter used in a radio multiplex transmission system, the
transmitter comprising: an error-correcting encoder for performing
an error-correcting encoding process on serial data to be
transmitted; a serial-to-parallel converter for serial-to-parallel
converting serial signals output from the error-correcting encoder
into N (N: two or more) parallel data series; N interleavers for
independently performing an interleaving process on the parallel
signals of the N data series output from the serial-to-parallel
converter; and a plurality of transmission antennas for
transmitting the N signals output from each interleaver.
8. A signal transmission method in a radio multiplex transmission
system, the signal transmission method comprising the steps of:
selecting, in accordance with predetermined transmission control
information, whether to perform an error-correcting encoding
process on serial data to be transmitted in a parallel manner or in
a serial manner; and selecting whether to perform an interleaving
process on the data encoded with error-correcting codes in a
parallel manner or in a serial manner.
9. A signal reception method in a, radio multiplex transmission
system, the signal reception method comprising the steps of:
selecting, in accordance with predetermined reception control
information, whether to perform a deinterleaving process on
received signals in a parallel manner or in a serial manner; and
selecting whether to perform an error-correcting decoding process
on the deinterleaved signals in a parallel manner or in a serial
manner.
10. A transmitter used in a radio multiplex transmission system,
the transmitter comprising: a plurality of selecting switches for
selecting a connection relationship between serial data and a
plurality of error-correcting encoders and a plurality of
interleavers; a control information demodulating unit for receiving
predetermined transmission control information from a receiver and
for demodulating the received transmission control information; a
structure determining unit for determining, in accordance with the
demodulated transmission control information, whether to connect to
the error-correcting encoders in a parallel manner for serial data
to be transmitted and whether to connect to the interleavers in a
parallel manner for the data encoded with error-correcting codes;
and a switching control unit for controlling the plural selecting
switches in accordance with the determined information.
11. A receiver used in a radio multiplex transmission system, the
receiver comprising: is a plurality of selecting switches for
selecting a connection relationship between received signals and a
plurality of deinterleavers and a plurality of error-correcting
decoders; a control information demodulating unit for receiving
predetermined reception control information from a transmitter and
for demodulating the received reception control information; a
switching control unit for controlling the plurality of selecting
switches in order to select, in accordance with the demodulated
reception control information, whether to connect to the
deinterleavers in a parallel manner for received signals and
whether to connect to the error-correcting decoders in a parallel
manner for the deinterleaved signals.
Description
TECHNICAL FIELD
[0001] The present invention generally relates to a signal
transmission method and a transmitter in a radio multiplex
transmission system and more particularly to a transmission method
and a transmitter in a MIMO transmission system, in which the
amount of processing for error-correcting encoding, interleaving,
and deinterleaving and/or error-correcting decoding is reduced.
BACKGROUND ART
[0002] In a radio communication method such as CDMA, for example,
it is important to realize a high-speed information rate. One known
signal transmission method uses MIMO (Multiple-Input
Multiple-Output) channels with plural transmission/reception
antennas in order to achieve such a rate. In the MIMO transmission
method, both a transmission side and a reception side have N
disposed antennas and plural different signals are efficiently
transmitted at the same time using the same frequency band through
a network with N port inputs and N port outputs connected via a
radio circuit. In other words, the method is intended to enlarge
the capacity of transmission by increasing the numbers of
transmission antennas and reception antennas so as to use space in
a multiple manner.
[0003] In the MIMO multiplexing method as shown in FIG. 1, when
plural different transmission symbols are transmitted at the same
time with each of the N transmission antennas 124 using the same
frequency and the same spread code, these transmission symbols are
synthesized in space. This can be interpreted that the transmission
symbols are multiple-valued in space in a certain-sense, so that
the information rate can be increased to several times that of the
transmission antennas.
[0004] In this MIMO multiplexing method, known techniques for
realizing a high-reliability transmission employ error-correcting
encoding and interleaving. For example, conventional techniques are
disclosed in "Takumi ITO, Xiaodong WANG, Yoshikazu KIMURA, Mohammad
MADIHIAN, and Akihisa USHIROKAWA "MF and MMSE Combined Iterative
Soft Interference Canceller for MIMO/OFDM Systems" The Technical
Report of the Institute of Electronics, Information and
Communication Engineers of Japan, RCS2002-295, pp. 117-124, March,
2003" (Non-patent Document 1).
[0005] FIG. 2 shows an example of a conventional MIMO transmission
system. A transmitter 210 comprises an error-correcting encoder
214, an interleaver 218, a serial-to-parallel converter 212, and N
antennas 224. A receiver 240 comprises N antennas 254, a signal
separator 252, a parallel-to-serial converter 242, a deinterleaver
248, and an error-correcting decoder 244. Interleaving is a process
for switching the order of encoded bit data series prior to
modulation and performing the reverse operation after demodulation.
The interleaving is used to separate and relocate burst errors
exceeding several code words (block codes) or a constraint length
(trellis codes) in order to accurately decode exact random errors
with a high probability in accordance with designed codes.
[0006] In the transmitter 210, transmission data 211 are encoded
with error-correcting codes, interleaved, and then resultant serial
data is serial-to-parallel converted, thereby gaining N parallel
data sets. Each parallel data set is transmitted using the
corresponding transmission antenna 224.
[0007] Then, each of the antennas 254 of the receiver 240 receives
signals transmitted from the transmitter 210. The received signals
are separated into N parallel signals using the signal separator
252 of the receiver 240. The N parallel signals after the signal
separation are parallel-to-serial converted, deinterleaved, and the
error-correcting codes are decoded.
[0008] In this example of conventional techniques, information
before the serial-to-parallel conversion is encoded with
error-correcting codes and interleaved, so that improved effects on
the characteristics of an error rate are expected using a space
diversity effect.
[0009] Non-patent Document 1: "MF and MMSE Combined Iterative Soft
Interference Canceller for MIMO/QFDM Systems" by Takumi ITO,
Xiaodong WANG, Yoshikazu KIMURA, Mohammad MADIHIAN, and Akihisa
USHIROKAWA, The Technical Report of the Institute of Electronics,
Information and Communication Engineers of Japan, RCS2002-295, pp.
117-124, March, 2003
[0010] For example, in a CDMA mobile communication system such as
WCDMA, CDMA 2000, and the like, it is required that an ultra
high-speed information rate be realized. And regarding that
requirement, it is possible to increase the information rate by
applying the MIMO multiplexing method as mentioned above in which
parallel transmission of information is performed using plural
transmission antennas. However, when a conventional structural
method as shown in FIG. 2 is used, very high-speed processing is
required in the error-correcting encoder 214 and the interleaver
218 of the transmitter 210, and in the deinterleater 248 and the
error-correcting decoder 244 of the receiver 240. Also, the size of
the interleaver and the deinterleaver must be enlarged. For
example, when information is transmitted on the assumption that the
number of the transmission antennas is N=4 and the information is
transmitted at 250 Mbps in each antenna, it is required that the
error-correcting encoder 214 and the interleaver 218 of the
transmitter 210, and the deinterleaver 248 and the error-correcting
decoder 244 of the receiver 240 process data at 250.times.4=1000
Mbps=1 Gbps. This high-speed processing imposes a heavy work load
in terms of implementation and thus poses a problem.
DISCLOSURE OF THE INVENTION
[0011] The present invention has been made in view of the
aforementioned problem. It is a general object of the present
invention to provide an improved and useful MIMO transmission
system in which the above-mentioned problem is eliminated.
[0012] A more specific object of the present invention is to
provide a MIMO transmission system in which the amount of
processing for error-correcting encoding, interleaving, and/or
error-correcting decoding is reduced in a transmitter and/or a
receiver.
[0013] Another object of the present invention is to provide a MIMO
transmission system as mentioned above such that even a space
diversity effect is obtained.
[0014] In order to achieve the aforementioned objects, according to
one aspect of the present invention, a signal transmission method
in a radio multiplex transmission system comprises the steps of:
serial-to-parallel converting serial data to be transmitted into N
(N: two or more) parallel data series; independently performing an
error-correcting encoding process and/or an interleaving process on
the parallel signals of the N data series serial-to-parallel
converted; transmitting each of the processed signals using plural
transmission antennas; receiving the transmitted signals;
separating the received signals into M (M: two or more) data
series; independently performing a deinterleaving process and/or an
error-correcting decoding process on each of the separated signals;
and parallel-to-serial converting the processed signals, thereby
recovering the transmitted data.
[0015] Accordingly, it is possible to conduct the error-correcting
encoding/decoding process and the interleaving/deinterleaving
process in a parallel manner. Thus, it is possible to reduce the
amount of processing in each encoder/decoder and
interleaver/deinterleaver to one Nth or one Mth.
[0016] According to another aspect of the present invention, a
signal transmission method in a radio multiplex transmission system
comprises the steps of: serial-to-parallel converting serial data
to be transmitted into M (M: two or more) parallel data series;
independently performing an error-correcting encoding process on
the parallel signals of the M data series serial-to-parallel
converted; parallel-to-serial converting the parallel signals
encoded with error-correcting codes; performing an interleaving
process on the parallel-to-serial converted signals;
serial-to-parallel converting the interleaved signals into N (N:
two or more) parallel data series and transmitting each of the N
data series using plural transmission antennas; receiving the
transmitted signals; separating the received signals into M (M: two
or more) data series and parallel-to-serial converting the M data
series: performing a-deinterleaving process on the
parallel-to-serial converted signals; serial-to-parallel converting
the deinterleaved signals into N data series; independently
performing an error-correcting decoding process on the parallel
signals of the N data series serial-to-parallel converted; and
parallel-to-serial converting the signals in which error-correcting
codes are decoded, thereby recovering the transmitted data.
[0017] A signal reception method in a radio multiplex transmission
system comprises the steps of: receiving signals transmitted from a
transmitter, using plural antennas; separating the received signals
into N (N: two or more) data series and parallel-to-serial
converting the N data series; performing a deinterleaving process
on the parallel-to-serial converted signals; serial-to-parallel
converting the deinterleaved signals into M parallel data series;
independently performing an error-correcting decoding process on
the parallel signals of the M data series serial-to-parallel
converted; and parallel-to-serial converting the signals in which
error-correcting codes are decoded, thereby recovering the
transmitted data.
[0018] Accordingly, it is possible to perform the error-correcting
encoding/decoding process in a parallel manner. Thus, it is
possible to reduce the amount of processing in each encoder/decoder
to one Mth and also to gain a space diversity effect.
[0019] According to the transmission method and the transmitter of
embodiments of the present invention, the following effects can be
obtained.
[0020] (1) On the transmission side, the error-correcting encoding
process and the interleaving process are performed for each of the
transmission antennas after information is serial-to-parallel
converted into the same number of data series as the transmission
antennas. On the reception side, the deinterleaving process and the
error-correcting decoding process are performed on each of the
signal data series after the signal separation. Transmitted
information is recovered after the parallel-to-serial conversion.
Thus, it is possible to reduce the processing speed required for
each error-correcting encoder, error-correcting decoder, and
interleaver and/or deinterleaver.
[0021] (2) On the transmission side, the error-correcting encoding
process is independently performed for each of the transmission
antennas in a parallel manner after information is
serial-to-parallel converted into the same number of data series as
the transmission antennas. The interleaving process is performed
after the parallel-to-serial conversion. On the reception side, the
deinterleaving process is performed on each of the separated signal
data series after the parallel-to-serial conversion. Further, the
error-correcting decoding process is independently performed on
each of the signal data series in a parallel manner after the
serial-to-parallel conversion. Transmitted information is recovered
after the parallel-to-serial conversion. Thus, it is possible to
reduce the processing speed required for each error-correcting
encoder and error-correcting decoder and to gain a space diversity
effect.
[0022] (3) On the transmission side, the error-correcting encoding
process is performed before information is serial-to-parallel
converted into the same number of data series as the transmission
antennas. The interleaving process is performed for each of the
transmission antennas after the serial-to-parallel conversion on
the reception side, the deinterleaving process is performed on each
of the separated signal data series. Further, the error-correcting
decoding process is performed after the parallel-to-serial
conversion, thereby recovering transmitted information. Thus, it is
possible to reduce the amount of processing in each interleaver and
deinterleaver.
[0023] (4) On the transmission side, whether to perform the
error-correcting encoding process on information to be transmitted
in a parallel manner or in a serial manner is selected. Also,
whether to perform the interleaving process on the signals encoded
with error-correcting codes in a parallel manner or in a serial
manner is selected. Thus, it is possible to select an
optimum-transmission rate and channel encoding/interleaving method
in accordance with the propagation state of radio waves and control
information about the state of the receiver.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a conceptual diagram of a MIMO transmission system
to which an embodiment of the present invention can be applied;
[0025] FIG. 2 is a block diagram of a conventional MIMO
transmission system;
[0026] FIG. 3 is a schematic block diagram of a MIMO transmission
system according to a first embodiment;
[0027] FIG. 4 is a schematic block diagram of a MIMO transmission
system according to a second embodiment;
[0028] FIG. 5 is a schematic block diagram of a MIMO transmission
system according to a third embodiment;
[0029] FIG. 6 is a comparative graph of a conventional MIMO
transmission system and MIMO transmission systems according to
embodiments;
[0030] FIG. 7 is a block diagram of a transmitter performing a
control method according to the fourth and fifth embodiments;
and
[0031] FIG. 8 is a block diagram of a receiver performing a control
method according to the fourth and fifth embodiments.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] In the following, embodiments of the present invention are
described with reference to the drawings.
Embodiment 1
[0033] FIG. 3 is a schematic block diagram of a MIMO transmission
system according to a first embodiment of the present invention. A
transmitter 310 comprises a serial-to-parallel converter 312, N
error-correcting encoders 314, N interleavers 318, and N antennas
324. A receiver 340 comprises N antennas 354, a signal separator
352, N deinterleavers 348, N error-correcting decoders 344, and a
parallel-to-serial converter 342.
[0034] In the transmitter 310, first, serial transmission data 311
are serial-to-parallel converted. N parallel data series gained
through the serial-to-parallel conversion are encoded with
error-correcting codes and interleaved. Thereafter, each parallel
data series is transmitted using the corresponding antenna 324.
[0035] Then, each of the antennas 354 of the receiver 340 receives
signals transmitted from the transmitter 310. The received signals
are separated into N parallel signals using the signal separator
352 of the receiver 340. The N parallel signals after the signal
separation are first deinterleaved, and then the error-correcting
codes are decoded. The N parallel signals are parallel-to-serial
converted, thereby gaining data 341 in which the transmitted
information is recovered.
[0036] According to this structure, it is possible to perform the
error-correcting encoding process and the interleaving process on
the transmission side on the N signal data series corresponding to
the N transmission antennas in a parallel manner. Also, it is
possible to perform the deinterleaving process and the
error-correcting decoding process on the N signal data series in a
parallel manner due to the signal separator 352 using the reception
signals on the reception side. Thus, the processing speed required
for each error-correcting encoder, decoder, interleaver, and
deinterleaver is reduced to one Nth in comparison with the example
of a conventional MIMO transmission system. Accordingly, the size
of the interleaver and the deinterleaver can be reduced.
Embodiment 2
[0037] FIG. 4 is a schematic block diagram of a MIMO transmission
system according to a second embodiment of the present invention. A
transmitter 410 comprises a serial-to-parallel converter 412, M
error-correcting encoders 414, a parallel-to-serial converter 416,
an interleaver 418, a serial-to-parallel converter 420, and N
antennas 424. A receiver 440 comprises N antennas 454, a signal
separator 452, a parallel-to-serial converter 450, a deinterleaver
448, a serial-to-parallel converter 446, M error-correcting
decoders 444, and a parallel-to-serial converter 442.
[0038] In the transmitter 410, first, serial transmission data 411
is serial-to-parallel converted. M parallel data series gained
through the serial-to-parallel conversion are encoded with
error-correcting codes independently in a parallel manner.
Thereafter, the encoded parallel data series are parallel-to-serial
converted and interleaved. The interleaved serial data are
serial-to-parallel converted, and then each of the parallel data
series is transmitted using the corresponding N transmission
antenna 424.
[0039] Then, each of the N antennas 454 of the receiver 440
receives signals transmitted from the transmitter 410. The received
signals are separated into N parallel signals using the signal
separator 452 of the receiver 440. The N parallel signals after the
signal separation are first parallel-to-serial converted and the
obtained serial data are deinterleaved. Thereafter, the
deinterleaved serial data are serial-to-parallel converted again
and an error-correcting decoding is performed on the M signal data
series independently in a parallel manner. The decoded parallel
data are parallel-to-serial converted, thereby gaining data 441 in
which the transmitted information is recovered.
[0040] The numbers N and M may or may not be the same.
[0041] According to the structure of the second embodiment, it is
possible to perform the error-correcting encoding process on each
signal data series after the serial-to-parallel conversion on the
transmission side. Also, it is possible to perform the
error-correcting decoding process on each of the signal data series
after the signal separation in a parallel manner on the reception
side. Thus, the amount of processing required for each
error-correcting encoder and error-correcting decoder is reduced to
one Mth in comparison with the example of a conventional MIMO
transmission system.
[0042] Further, a space diversity effect on the interleaving can be
obtained by performing the interleaving process on serial
information before the serial-to-parallel conversion into signals
for each of the transmission antennas. Thus, the characteristics of
an error rate are improved in comparison with the first
embodiment.
Embodiment 3
[0043] FIG. 5 is a schematic block diagram of a MIMO transmission
system according to a third embodiment of the present invention. A
transmitter 510 comprises an error-correcting encoder 514, a
serial-to-parallel converter 520, an interleaver 518, and N
antennas 524. A receiver 540 comprises N antennas 554, a signal
separator 552, a deinterleaver 548, a parallel-to-serial converter
542, and an error-correcting decoder 544.
[0044] In the transmitter 510, first, serial transmission data 511
are encoded with error-correcting codes. Then, the encoded data are
serial-to-parallel converted and N parallel data series gained
through the serial-to-parallel conversion are interleaved
independently in a parallel manner. Thereafter, each parallel data
series is transmitted using the corresponding antenna 524.
[0045] Then, each of the N antennas 554 of the receiver 540
receives signals transmitted from the transmitter 510. The received
signals are separated into N parallel signals using the signal
separator 552 of the receiver 540. The N parallel signals after the
signal separation are first deinterleaved and then
parallel-to-serial converted. An error-correcting decoding is
performed on the gained serial data, thereby gaining data 541 in
which the transmitted information is recovered.
[0046] According to this structure, it is possible to perform the
interleaving process on each signal data series after the
serial-to-parallel conversion on the transmission side. Also, it is
possible to, perform the deinterleaving process on each of the
signal data series after the signal separation in a parallel manner
on the reception side. Thus, the processing speed required for each
interleaver and deinterleaver is reduced to one Nth in comparison
with the example of a conventional MIMO transmission system.
[0047] FIG. 6 shows a result of computer simulation regarding the
characteristics of average packet error rates of received Eb/No
(Eb: electric power of received signals per one bit of information,
No: noise power density) in the MIMO transmission systems according
to the example of conventional techniques and the first through the
third embodiments. In this evaluation, the number of the
transmission antennas is N=4, a turbo encoding process with a
constraint length of 4 is used as an error-correcting encoding
process on the transmission side, and a symbol interleaving process
is used as an interleaving process on the basis of the document by
N. Maeda, H. Atarashi, and M. Sawahashi, "Performance comparison of
channel interleaving methods in frequency domain for VSF-OFCDM
broadband wireless access in forward link," IEICE Trans. Commun.,
vol. E86-B, no. 1, pp. 300-313, January 2003. On the reception
side, signal separation is performed on the basis of maximum
likelihood detection and Max Log-MAP algorithm with 8 iterations is
used for error-correcting. In addition, a one-path Rayleigh fading
channel with a maximum Doppler frequency of 20 Hz is used as a
propagation channel model.
[0048] In FIG. 6, the structure of the MIMO transmission system
according to the first embodiment (black triangles) shows the
degradation of the characteristics of a packet error rate by about
1.5 dB as compared with the conventional structure (outlined
rhombuses). However, the processing speed required for each decoder
and deinterleaver on the reception side can be reduced to 1/4, so
that processing delay in the decoder and deinterleaver can be
reduced to 1/4.
[0049] Next, the structure of the MIMO transmission system
according to the second embodiment (black squares) is capable of
reducing the processing speed required for each decoder on the
reception side to 1/4 as compared with the conventional structure
(outlined rhombuses). Also, the structure of the MIMO transmission
system according to the second embodiment is capable of controlling
the degradation of the characteristics of a packet error rate
within 0.5 dB relative to the conventional structure in accordance
with the improved characteristics due to a space interleaving
effect.
[0050] Further, the structure of the MIMO transmission system
according to the third embodiment (black circles) is capable of
reducing the amount of processing required for each deinterleaver
on the reception side to 1/4 as compared with the conventional
structure (outlined rhombuses). Also, the structure of the MIMO
transmission system according to the third embodiment is capable of
gaining substantially the same characteristics of a packet error
rate as that of the conventional structure.
[0051] In the aforementioned embodiments, the number of antennas on
the transmission side and the number of antennas on the reception
side are the same. However, the present invention is not limited to
the same number of antennas but may employ different numbers of
antennas on the transmission side and the reception side.
Embodiment 4
[0052] In a fourth embodiment, a transmitter changes the
transmission rate in response to the reception status of radio
waves in a receiver and the transmitter selects and uses an
appropriate channel encoding/interleaving method in accordance with
the change.
[0053] According to the first embodiment, the information bit rate
of the error-correcting encoding process and the error-correcting
decoding process can be reduced to one Nth and the size of the
interleaver and the deinterleaver can be reduced. In addition, the
work load in terms of the apparatus structure is most reduced.
However, there is a disadvantage in that a diversity effect using
the transmission antennas is not obtained and thus the reception
quality is reduced.
[0054] According to the second embodiment, the information bit rate
of the error-correcting encoding process and the error-correcting
decoding process can be reduced to one Mth. Also, a diversity
effect using the transmission antennas can be obtained to a certain
extent by performing the interleaving across the transmission
antennas. However, there is a disadvantage in that the size of the
interleaven is increased as compared with the first embodiment.
[0055] According to the third embodiment, the size of the
interleaver and the deinterleaver can be reduced. Also, optimum
reception characteristics in the aforementioned embodiments can be
obtained due to the space diversity effect. However, there is a
disadvantage in that the error-correcting encoding and the
error-correcting decoding must be processed at the speed of the
information bit rate.
[0056] In the above-mentioned three embodiments, each has a
trade-off between merits and demerits. Thus, in the fourth
embodiment, the above-mentioned three embodiments are switched and
used in accordance with the transmission rate. When the
transmission rate is low (400 Mbps, for example), the amount of
processing does not have a great influence, so that the third
embodiment is used so as to obtain the optimum reception
characteristics. When the transmission rate is high (1 Gbps, for
example), the amount of processing has a great influence, so that
the second embodiment is used so as to reduce the work load on the
apparatus even at the sacrifice of the reception characteristics to
a certain extent. When the reception status is good and the
reception quality does not have a great influence while the
apparatus structure is limited, the first embodiment can be
used.
[0057] In the following, the procedure of controlling the fourth
embodiment is described. [0058] (1) The receiving station measures
the reception status of radio waves (received SIR, for example).
[0059] (2) The receiving station notifies the transmitting station
of the reception status of radio waves as an example of
transmission control information using a reverse radio link. [0060]
(3) The transmitting station determines the transmission rate on
the basis of the reception status of radio waves. [0061] (4) The
transmitting station determines a channel encoding/interleaving
method on the basis of the determined transmission rate. [0062] (5)
The transmitting station performs the channel encoding/interleaving
on data with the determined transmission rate, and then transmits
the resultant transmission data. At the same time, transmission
rate information (including a modulation method and a channel
encoding rate) and information about which channel
encoding/interleaving method is used are transmitted as the
transmission control information. [0063] (6) The receiving station
identifies the transmission rate information and the information
about which channel encoding/interleaving method is used from
reception control information and receives the transmission
data.
Embodiment 5
[0064] In the fourth embodiment, the transmission rate is changed
in accordance with the reception status of radio waves in the
receiver. Then the channel encoding/interleaving method is selected
and used in accordance with the transmission rate. In a fifth
embodiment, information about the processing capacity of the
receiving station is used as the transmission control information
in addition to the reception status of radio waves. The
transmission rate is changed in accordance with the reception
status and the processing capacity, and the channel
encoding/interleaving method is selected and used in accordance
with the transmission rate.
[0065] In the following, the procedure of controlling of the fifth
embodiment is described. [0066] (1) The receiving station measures
the reception status of radio waves (received SIR, for example).
[0067] (2) The receiving station notifies the transmitting station
of the reception status of radio waves and the processing capacity
(the interleaving capacity and the error-correcting decoding
capacity) of the receiving station as the transmission control
information using the reverse radio link. [0068] (3), (4) The
transmitting station determines the combination of the transmission
rate and the channel encoding/interleaving method on the basis of
the reception status of radio waves and the processing capacity of
the receiving station. When the reception quality is particularly
good, the error-correcting encoding may not be performed. [0069]
(5) The transmitting station performs the channel
encoding/interleaving on data with the determined transmission
rate, and then transmits the resultant transmission data. At the
same time, transmission rate information (including a modulation
method and a channel encoding rate) and information about which
channel encoding/interleaving method is used are transmitted as the
reception control information. [0070] (6) The receiving station
identifies the transmission rate information and the information
about which channel encoding/interleaving method is used from the
reception control information and receives the transmission
data.
Embodiment 6
[0071] FIG. 7 is a block diagram of a transmitter for performing
the control method according to the fourth and fifth embodiments. A
control information demodulating unit 760 of a transmitter 710
receives and demodulates signals regarding the reception status of
radio waves in the receiver and the processing capacity of the
receiver (an example-of the transmission control information). The
modulated transmission control information is supplied to a
transmission rate and structure determining unit 762.
[0072] On the basis of the transmission control information, the
transmission rate and structure determining unit 762 determines the
transmission rate of transmission signals and which structure of
the channel encoding/interleaving method is to be used. The
determined information is sent to a control information
multiplexing unit 768, multiplexed with transmission data, and
transmitted to the receiver.
[0073] Also, the determined information about which structure of
the channel encoding/interleaving method is to be used is supplied
to a switching control unit 764. The switching control unit 764
switches each of switches a, b, and c in accordance with the
determined information.
[0074] The switch a selects whether to perform the error-correcting
encoding on the transmission information in a parallel manner. The
switches b and c select whether to interleave the information
encoded with error-correcting codes in a parallel manner or in a
serial manner. By the selection of the switches a, b, and c in this
manner, it is possible to select the structures of the
aforementioned transmitters according to the first through third
embodiments.
Embodiment 7
[0075] FIG. 8 is a block diagram of a receiver for performing the
control method according to the fourth and fifth embodiments. A
reception status estimating unit 862 of a receiver 840 measures or
estimates the reception status of the receiver and the result is
transmitted to the transmitter 710 via a transmission unit. A
control information demodulating unit 860 of the receiver 840
receives and demodulates the reception control information about
the transmission rate and the channel encoding/interleaving method
transmitted from the transmitter. The demodulated information is
supplied to a switching control unit 864.
[0076] The switching control unit 864 switches each of switches d,
e, and f in accordance with the demodulated information.
[0077] The switch d is for selecting whether to deinterleave
received information in a parallel manner or in a serial manner.
The switch d corresponds to the operations of the switches b and c
of the transmitter. The switches e and f are switches for selecting
whether to perform the error-correcting decoding process in a
parallel manner or in a serial manner. The switches e and f
correspond to the operation of the switch a of the transmitter.
[0078] By the selection of the switches d, e, and f in this manner,
it is possible to select the structures of the aforementioned
receivers according to the first through third embodiments.
[0079] The present invention is not limited to the specifically
disclosed embodiments, and variations and modifications may be made
without departing from the scope of the present invention.
[0080] The present application is based on Japanese priority
application No. 2003-317464 filed Sep. 9, 2003, the entire contents
of which are hereby incorporated herein by reference.
INDUSTRIAL APPLICABILITY
[0081] The transmitter, the receiver, and the transmission system
according to the present invention can be applied to a high-speed
radio communication system such as WCDMA, and can also be used in
radio communication fields without imposing an excessive work load
on devices in a transmitter and a receiver, in which high-speed
transmission with a low error rate is required.
* * * * *