 |
Claims  |
|
|
What is claimed is:
1. A spread spectrum communication apparatus comprising:
generation means for generating a plurality of different spread codes in
parallel;
modulation means for modulating transmission information of parallel bits
using the plurality of spread codes generated by said generation means;
and
transmission means for transmitting the transmission information modulated
by said modulation means,
wherein said modulation means modulates each bit of the parallel bits using
each of the plurality of spread codes in parallel.
2. The apparatus according to claim 1, wherein said generation means
comprises a plurality of delay means having different delay times, and
supplies a common spread code to said plurality of delay means to generate
a plurality of spread codes having different phases.
3. The apparatus according to claim 1, wherein said generation means
further generates a synchronization spread code, and said transmission
means multiplies the signal accumulated by said accumulation means with
the synchronization spread code generated by said generation means, and
transmits the product signal.
4. The apparatus according to claim 3, wherein said generation means
generates the synchronization spread code having the same length as that
of the plurality of spread codes.
5. The apparatus according to claim 1, further comprising conversion means
for converting serial data into parallel data, and wherein said modulation
means modulates parallel data converted by said conversion means.
6. The apparatus according to claim 1, further comprising conversion means
for converting serial transmission information into the transmission
information of the parallel bits.
7. A spread spectrum communication apparatus comprising:
reception means for receiving a reception signal;
generation means for generating a plurality of different despread codes in
parallel;
demodulation means for demodulating the reception signal using the
plurality of despread codes generated by said generation means,
respectively; and
conversion means for converting the reception signal demodulated by said
demodulation means into parallel bits.
8. The apparatus according to claim 7, wherein said generation means
comprises a plurality of delay means having different delay times, and
supplies a common inverse spread code to said plurality of delay means to
generate a plurality of inverse spread codes having different phases.
9. The apparatus according to claim 7, wherein said generation means
comprises means for generating a synchronization spread code in
synchronism with the plurality of inverse spread codes, and correlation
means for checking a correlation between the synchronization spread code
and a reception signal, and generates the plurality of inverse spread
codes according to the correlation between the synchronization spread code
and the reception signal.
10. The apparatus according to claim 9, wherein said generation means
generates the synchronization spread code having the same length as that
of the plurality of inverse spread codes.
11. The apparatus according to claim 7, further comprising conversion means
for converting parallel data into serial data, said conversion means
converting a parallel signal demodulated by said demodulation means into a
serial signal.
12. A spread spectrum transmission apparatus comprising:
generation means for generating a plurality of spread codes;
demultiplexing means for demultiplexing transmission information, generated
by multiplexing data from a plurality of channels, to data from each of
the plurality of channels;
spread means for spreading the data from each of the plurality of channels
demultiplexed by said demultiplexing means on the basis of the plurality
of spread codes generated by said generation means; and
transmission means for transmitting the data from the plurality of channels
spread by said spread means.
13. The apparatus according to claim 12, further comprising conversion
means for converting serial transmission information into the transmission
information consisting of the plurality of bits.
14. The apparatus according to claim 12, wherein said demultiplexing means
demultiplexes information from a digital network.
15. The apparatus according to claim 12, wherein said demultiplexing means
demultiplexes information from a digital terminal.
16. A spread spectrum reception apparatus comprising:
reception means for receiving a reception signal;
generation means for generating a plurality of despread codes;
a plurality of despread means for despreading the reception signal on the
basis of the plurality of despread codes generated by said generation
means, respectively;
supply means for supplying the reception signal to said plurality of
despread means; and
conversion means for converting a plurality of outputs of the plurality of
despread means into parallel data.
17. The apparatus according to claim 16, wherein said supply means supplies
the reception signal to the plurality of despread means in parallel.
18. A spread spectrum communication apparatus comprising:
first generation means for generating a first spread code;
a plurality of delay means for delaying the first spread code to generate a
plurality of spread codes having different phases;
modulation means for modulating transmission information signals of a
plurality of parallel channels using the plurality of spread codes
generated by said plurality of delay;
accumulation means for accumulating the signals of the channels modulated
by said modulation means;
second generation means for generating a second spread code;
multiplication means for multiplying a signal accumulated by said
accumulation means with the second spread code generated by said second
generation means; and
transmission means for transmitting the signal multiplied by said
multiplication means.
19. A spread spectrum communication apparatus comprising:
first generation means for generating a first inverse spread code;
second generation means for generating a second inverse spread code;
correlation means for checking a correlation between the second inverse
spread code and a reception signal;
third generation means for delaying the first inverse spread code according
to the correlation between the second inverse spread code and the
reception signal to generate a plurality of inverse spread codes having
different phases; and
modulation means for parallelly modulating the reception signal using the
plurality of inverse spread codes generated by said third generation
means.
20. A telephone exchange system having an extension connected by radio,
comprising:
reception means for receiving a signal from a terminal;
demodulation means for despreading the signal received by said reception
means to demodulate the signal into a speech signal;
exchange means for exchanging the speech signal demodulated by said
demodulation means;
transmission means for transmitting the speech signal exchanged by said
exchange means to a communication partner; and
control means for controlling said exchange means on the basis of the
signal received by said reception means.
21. The system according to claim 20, wherein said demodulation means
despreads the reception signal using a plurality of inverse spread codes.
22. The system according to claim 21, wherein said demodulation means
converts the data despread by the plurality of inverse spread codes into
serial data, and outputs the serial data.
23. The system according to claim 21, wherein said demodulation means
converts the data despread by the plurality of inverse spread codes into
Alternate Mark Inversion code data, and outputs the Alternate Mark
Inversion code data.
24. A telephone exchange system having an extension connected by radio,
comprising:
receiving means for receiving a speech signal from a communication partner;
exchange means for exchanging the speech signal received by said receiving
means;
spread means for spreading the speech signal exchanged by said exchange
means; and
transmission means for transmitting the signal spread by said means to a
terminal.
25. The system according to claim 24, wherein said transmission means
spreads the speech signal using a plurality of spread codes.
26. The system according to claim 25, wherein said transmission means
converts the speech signal into parallel data, and spreads channels of the
parallel data using a plurality of different spread codes, respectively.
27. The system according to claim 25, wherein said transmission means
demultiplexes a speech signal coded by Alternate Mark Inversion in units
of channels, and spreads the demultiplexed data using different spread
codes in units of channels.
28. A telephone exchange system having an extension connected by radio,
comprising:
reception means for receiving a signal;
demodulation means for despreading the signal received by said reception
means to demodulate the signal into a speech signal;
exchange means for exchanging the speech signal;
control means for controlling said exchange means on the basis of the
signal received by said reception means;
spread means for spreading the speech signal exchanged by said exchange
means; and
transmission means for transmitting the signal spread by said spread means.
29. A telephone exchange system connected to a plurality of mobile
terminals by radio, comprising:
selection means for selecting one of a plurality of spread codes;
information means for informing the spread code selected by said selection
means to one of the plurality of mobile terminals by radio;
demodulation means for despreading the signal from the mobile terminal
informed by said information means in accordance with the spread code
selected by selection means to demodulate the signal into a speech signal;
and
transmission means for transmitting the speech signal to a communication
partner.
30. The system according to claim 29, wherein said selection means
comprises storage means for storing use conditions of the plurality of
spread codes, and looks up said storage means to select an unused spread
code.
31. A telephone exchange system connected to a plurality of mobile
terminals by radio, comprising:
selection means for selecting one of a plurality of spread codes;
receiving means for receiving a speech signal from a communication partner:
exchange means for exchanging the speech signal received by said receiving
means;
modulation means for modulating the speech signal exchanged by said
exchange means in accordance with the spread code selected by said
selection means; and
transmission means for transmitting the signal modulated by said modulation
means.
32. A spread spectrum communication apparatus comprising:
storage means for storing a plurality of sets of spread codes;
selection means for selecting one set of the plurality of sets of spread
codes stored in said storage means; and
communication means for performing a communication on the basis of the set
of spread codes selected by said selection means.
33. The apparatus according to claim 32, wherein said selection means
comprises reception means for receiving a selection signal for selecting
one set of the plurality of sets of spread codes.
34. The apparatus according to claim 32, wherein said selection means
comprises second storage means for storing data indicating whether or not
each of the plurality of sets of spread codes is in use, and selects a
spread code, corresponding data of which is stored in said second storage
means to indicate that the spread code is not in use.
35. A spread spectrum transmission apparatus comprising:
generation means for generating a plurality of different spread codes in
parallel corresponding to parallel bits of transmission information;
a plurality of modulation means for modulating parallel bits of
transmission information using spread codes generated by said generation
means;
transmission means for transmitting output of said plurality of modulation
means;
wherein each of said plurality of modulation means modulates each bit of
the parallel bits of transmission information using each of the plurality
of spread codes.
36. A spread spectrum communication apparatus comprising:
reception means for receiving a reception signal;
generation means for generating a plurality of different despread codes in
parallel;
demodulation means for demodulating the reception signal using the
plurality of despread codes generated by said generation means, to output
a plurality of demodulated signals corresponding to the plurality of
despread codes;
multiplexing means for multiplexing the plurality of demodulated signals
demodulated by said demodulation means to output a multiplexed signal; and
transmission means for transmitting the multiplexed signal multiplexed by
said multiplexing means via a digital signal line.
37. The apparatus according to claim 36, wherein said transmission means
transmits the multiplexed signal to a digital network via the digital
signal line.
38. The apparatus according to claim 36, wherein said transmission means
transmits the multiplexed signal to a digital terminal via the digital
signal line. |
|
 |
|
 |
Claims |
|
|
|
Description |
|
|
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spread spectrum communication apparatus
and a telephone exchange system for performing communications through
radio channels.
2. Description of the Prior Art
Conventionally, as a communication system capable of attaining a multiple
access based on code division, a spread spectrum communication is known.
In the spread spectrum communication, a transmitter converts a baseband
signal to be transmitted into a baseband signal having a larger band width
than that of original data based on a PN (Pseudo Noise) code having a
sufficiently larger spectral width than that of the baseband signal to be
transmitted. Furthermore, the transmitter modulates the converted signal
based on, e.g., PSK (Phase Shift Keying) or FSK (Frequency Shift Keying)
to form a high-frequency signal, and transmits the high-frequency signal.
However, the conventional spread spectrum communication suffers from a low
data transmission speed since data is serially transmitted.
A conventional telephone exchange system performs an extension
communication by radio based on FM (Frequency Modulation). Another
conventional apparatus performs a data communication by radio based on
PSK.
FIG. 21 shows the arrangement of a data conversion apparatus in a
conventional telephone exchange system.
A case will be described below with reference to FIG. 21 wherein a
conventional speech communication is performed. When speech data input
from an exchange controller to a data conversion apparatus is to be
transmitted, speech data, i.e., transmission baseband data 171 is mixed
with an output signal from a transmission local oscillator 173 by a mixer
172 so as to be FM-modulated. The intermediate frequency of the output
signal from the mixer 172 is amplified by an IF (Intermediate Frequency)
amplifier 174, and the amplified signal is then filtered by a transmission
filter 175. The filtered signal is input to a multiplexer 176, and is then
transmitted from an antenna 177. A carrier wave upon modulation is
assigned in units of 12.5 kHz, and an FM modulation factor is designed so
that an occupied frequency after modulation does not exceed 12.5 kHz.
When an FM signal is to be received, an FM signal received at the antenna
177 is input to a mixer 179 through the multiplexer 176, and is mixed with
an output signal from a reception local oscillator 178. Thereafter, the
mixed signal is amplified by an IF amplifier 180, and the amplified signal
is demodulated by a demodulator 181 into a baseband data output.
However, in the above-mentioned radio data communication, a high-speed data
communication cannot be performed due to a problem of a limited use
frequency band. More specifically, when there are a plurality of users,
carrier waves of respective channels are set to have different frequencies
to prevent interference among users, and at the same time, the use
frequency band of each channel is limited. Therefore, when a high-speed
data communication is performed, a spurious signal is generated. Thus, a
simultaneous communication by a plurality of users suffers from a problem
about frequency utilization.
When a very weak radiowave is utilized to solve the problem about frequency
utilization, a transmission distance is undesirably shortened.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above problem, and has as
its object to provide a spread spectrum communication apparatus, which can
increase a data transmission speed.
It is another object of the present invention to provide a spread spectrum
communication apparatus comprising generation means for parallelly
generating a plurality of different spread codes, modulation means for
modulating transmission information signals of a plurality of parallel
channels using the plurality of spread codes generated by the generation
means, respectively, accumulation means for accumulating the signals of
the channels modulated by the modulation means, and transmission means for
transmitting a signal accumulated by the accumulation means.
It is still another object of the present invention to provide a spread
spectrum communication apparatus comprising generation means for
parallelly generating a plurality of different inverse spread codes, and
modulation means for parallelly modulating reception signals using the
plurality of inverse spread codes generated by the generation means,
respectively.
It is still another object of the present invention to provide a spread
spectrum transmission apparatus comprising generation means for generating
a plurality of spread codes, a plurality of spread means for spreading
transmission information on the basis of the plurality of spread codes
generated by the generation means, and supply means for supplying bits of
the transmission information consisting of a plurality of bits to the
plurality of spread means.
It is still another object of the present invention to provide a spread
spectrum reception apparatus comprising generation means for generating a
plurality of inverse spread codes, a plurality of inverse spread means for
performing inverse spread on the basis of the plurality of inverse spread
codes generated by the generation means, and supply means for parallelly
supplying a reception signal to the plurality of inverse spread means.
It is still another object of the present invention to provide a spread
spectrum communication apparatus comprising first generation means for
generating a first spread code, a plurality of delay means for delaying
the first spread code to generate a plurality of spread codes having
different phases, modulation means for modulating transmission information
signals of a plurality of parallel channels using the plurality of spread
codes generated by the first generation means, accumulation means for
accumulating the signals of the channels modulated by the modulation
means, second generation means for generating a second spread code,
multiplication means for multiplying a signal accumulated by the
accumulation means with the second spread code generated by the second
generation means, and transmission means for transmitting the signal
multiplied by the multiplication means.
It is still another object of the present invention to provide a spread
spectrum communication apparatus comprising first generation means for
generating a first inverse spread code, second generation means for
generating a second inverse spread code, correlation means for checking a
correlation between the second inverse spread code and a reception signal,
third generation means for delaying the first inverse spread code
according to the correlation between the second inverse spread code and
the reception signal to generate a plurality of inverse spread codes
having different phases, and modulation means for parallelly modulating
the reception signal using the plurality of inverse spread codes generated
by the third generation means.
It is still another object of the present invention to provide a telephone
exchange system having an extension connected by radio, comprising
reception means for receiving a signal from a terminal, demodulation means
for inversely spreading the signal received by the reception means to
demodulate the signal into a speech signal, exchange means for exchanging
the speech signal demodulated by the demodulation means, and control means
for controlling the exchange means on the basis of the signal received by
the reception means.
It is still another object of the present invention to provide a telephone
exchange system having an extension connected by radio, comprising
exchange means for exchanging a speech signal, spread means for spreading
the speech signal exchanged by the exchange means, and transmission means
for transmitting the signal spread by the spread means to a terminal.
It is still another object of the present invention to provide a telephone
exchange system having an extension connected by radio, comprising
reception means for receiving a signal, demodulation means for inversely
spreading the signal received by the reception means to demodulate the
signal into a speech signal, exchange means for exchanging the speech
signal, control means for controlling the exchange means on the basis of
the signal received by the reception means, spread means for spreading the
speech signal exchanged by the exchange means, and transmission means for
transmitting the signal spread by the spread means.
It is still another object of the present invention to provide a telephone
exchange system connected to a plurality of mobile terminals by radio,
comprising selection means for selecting one of a plurality of spread
codes, information means for informing the spread code selected by the
selection means to the mobile terminals by radio, and demodulation means
for inversely spreading the signal from the mobile terminals informed by
the information means in accordance with the spread code selected by
selection means to demodulate the signal into a speech signal.
It is still another object of the present invention to provide a telephone
exchange system connected to a plurality of mobile terminals by radio,
comprising selection means for selecting one of a plurality of spread
codes, exchange means for exchanging a speech signal, modulation means for
modulating the speech signal exchanged by the exchange means in accordance
with the spread code selected by the selection means, and transmission
means for transmitting the signal modulated by the modulation means.
Other features and advantages of the present invention will be apparent
from the following description taken in conjunction with the accompanying
drawings, in which like reference characters designate the same or similar
parts throughout the figures thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part
of the specification, illustrate embodiments of the invention and,
together with the description, serve to explain the principles of the
invention.
FIG. 1 is a block diagram showing the arrangement of a telephone exchange
system according to the first embodiment of the present invention;
FIG. 2 is a block diagram showing the arrangement of a data conversion
apparatus (transmission side) in the telephone exchange system of the
first embodiment;
FIG. 3 is a block diagram showing the arrangement of a data conversion
apparatus (reception side) in the telephone exchange system of the first
embodiment;
FIG. 4 is a block diagram showing the arrangement of a data conversion
apparatus (transmission side) in a telephone exchange system according to
the second embodiment of the present invention;
FIG. 5 is a block diagram showing the arrangement of a data conversion
apparatus (reception side) in the telephone exchange system of the second
embodiment;
FIG. 6A is a block diagram showing the arrangement of a telephone exchange
system according to the third embodiment of the present invention;
FIG. 6B is a block diagram showing the arrangement of an extension terminal
connected to the telephone exchange system of the third embodiment;
FIG. 7 is a block diagram showing the arrangement of a radio processor in
the telephone exchange system of the third embodiment;
FIG. 8 is a block diagram showing the arrangement of an extension interface
of an exchange controller of the third embodiment;
FIG. 9A is a block diagram showing the arrangement of a telephone exchange
system according to the fourth embodiment of the present invention;
FIG. 9B is a block diagram showing the arrangement of an extension terminal
connected to the telephone exchange system of the fourth embodiment;
FIG. 10 is a block diagram showing the arrangement of a data conversion
apparatus in the telephone exchange system of the fourth embodiment;
FIG. 11 is a block diagram showing the arrangement of a data conversion
apparatus in a telephone exchange system according to the fifth embodiment
of the present invention;
FIG. 12 is a block diagram showing the arrangement of a telephone exchange
system according to the sixth embodiment of the present invention;
FIG. 13 is a block diagram showing the arrangement of a fixed terminal of
the telephone exchange system of the sixth embodiment;
FIG. 14 is a block diagram showing the arrangement of a mobile terminal of
the telephone exchange system of the sixth embodiment;
FIG. 15 is a block diagram showing the arrangement of a
transmitter/receiver unit of the telephone exchange system of the sixth
embodiment;
FIG. 16 is a call termination sequence chart of the telephone exchange
system of the sixth embodiment;
FIG. 17 is a call generation sequence chart of the telephone exchange
system of the sixth embodiment;
FIG. 18 is a flow chart of a main apparatus of the telephone exchange
system of the sixth embodiment;
FIG. 19 is a flow chart of the fixed terminal of the telephone exchange
system of the sixth embodiment;
FIG. 20 is a flow chart of the mobile terminal of the telephone exchange
system of the sixth embodiment; and
FIG. 21 is a block diagram showing the arrangement of a data conversion
apparatus of a conventional telephone exchange system.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[First Embodiment (FIGS. 1, 2, and 3)]
The first embodiment of the present invention is a telephone exchange
system utilizing a spread spectrum communication.
FIG. 1 is a block diagram showing the arrangement of a telephone exchange
system adopting the present invention, and FIGS. 2 and 3 are block
diagrams of a data conversion apparatus.
A case will be described below wherein data is transmitted from a
communication terminal 13 in the telephone exchange system shown in FIG.
1.
When the communication terminal 13 performs transmission, control data
including a call generation procedure and the like is input to a data
conversion apparatus 11. The data signal input to the data conversion
apparatus 11 is a baseband data signal. The data conversion apparatus 11
converts the baseband signal into parallel data, and spread-modulates
parallel bits using different spread codes, respectively, thus obtaining a
high transmission rate.
FIGS. 2 and 3 are block diagrams showing the arrangement of a radio
processor in the data conversion apparatus for realizing a spread spectrum
communication of parallel data.
FIG. 2 is a block diagram showing the arrangement of a transmission system
in the radio processor of the telephone exchange system of this
embodiment, and FIG. 3 is a block diagram showing the arrangement of a
reception system of the radio processor.
A case will be explained below wherein 64-kbps speech PCM (Pulse Code
Modulation) data is input as a baseband signal.
In FIGS. 2 and 3, a baseband signal 131 is input to a serial/parallel
converter 132, and is converted into parallel 8-bit data in synchronism
with 64-kHz clocks. The converted 8-bit data is spread-modulated using
different spread codes in units of bits. The spread codes are generated by
eight PN code generators 134 to 136, and are respectively input to eight
spread modulators 133 to 135 arranged in correspondence with bits. The
eight PN code generators 134 to 136 generate spread codes in synchronism
with a common clock. The eight spread signals are added to each other by
an adder 137, and the sum signal is mixed with a signal generated by a
local oscillator 139 by a mixer 138 so as to be modulated to a radio
frequency. The modulated signal is amplified by an amplifier 140, and the
amplified signal is transmitted as a radiowave. Control data can also be
transmitted in the same manner as speech data.
The transmitted data is received by a data conversion apparatus 12. The
received signal is input to a SAW (Surface Acoustic Wave) convolver 151.
The convolver 151 also receives a PN code, which is generated by a PN code
generator 159, and is modulated by the output signal from a local
oscillator 158. The convolver 151 detects a correlation between the two
input signals, and outputs a pulse. A detector 152, a peak detector 153, a
phase comparator 154, a loop filter 155, a VCO 157, and a frequency
divider 156 constitute a phase synchronization circuit. The phase
synchronization circuit synchronizes the reception signal and spread codes
using the output pulse from the convolver 151. As long as a
synchronization is attained, the reception signal can be inversely spread.
The spread codes are generated by eight PN code generators 159 to 160, and
are mixed with a signal generated by the local oscillator 158. Then, the
codes are input to inverse-spread demodulators 162 to 163. The reception
signal is also input to the inverse-spread demodulators 162 to 163, and is
inversely spread. Note that the spread codes used for inverse spread are
different in units of code generators, and correspond to those at the
transmission side in units of bits of parallel data. Since each spread
code is generated in synchronism with an output signal from one VCO 157,
if synchronization is attained for one spread code (in this case, the code
generated by the code generator 159), synchronization can be attained for
all the eight spread codes.
In this manner, synchronization is maintained, and the reception signal is
inversely spread by the eight spread codes. After inverse-spread
demodulation, the eight bits are parallel/serial-converted to obtain
speech PCM data 165. Note that data exchanged between the data conversion
apparatuses 11 and 12 is obtained by multiplexing speech data and control
data. The received PG,16 control data is used in control of the data
conversion apparatus.
As described above, data to be transmitted from the data conversion
apparatus is converted into parallel data, and the parallel data is spread
in units of bits to transmit the spread bits, thus increasing a
transmission speed.
In this embodiment, serial data is converted into 8-bit parallel data.
However, the present invention is not limited to 8-bit data. If the
serial/parallel converter 132 is an n-bit converter, serial data input to
the serial/parallel converter 132 is converted into n-channel parallel
data. In order to spread n-channel data, n different spread codes (PN
codes) are prepared, and data in the respective channels are
spread-modulated using different spread codes. After modulation, the
spread data are added by the adder 137 in an analog manner, and
thereafter, the sum signal is modulated. The modulated signal is then
transmitted as a radio signal.
At the reception side, a correlation between reception data and n
difference inverse spread codes generated by the PN code generator 159 is
detected to acquire and maintain synchronization. As long as
synchronization is maintained, reception data can be demodulated by
inverse spread using the n different inverse spread codes prepared in
advance. The data demodulated by inverse spread are converted into serial
data by a parallel/serial converter 164.
With the above arrangement, a spread spectrum communication terminal can be
accommodated in an extension of the telephone exchange system.
In the arrangement of this embodiment, since a communication is performed
using parallel data, the transmission speed of spread-modulated data can
be 1/n that of data to be actually transmitted. Therefore, the processing
gain can be increased, and high quality can be obtained.
When parallel data are directly processed in the reception and transmission
systems, the serial/parallel converter 132 and the parallel/serial
converter 164 can be omitted.
Since n-bit parallel data are transmitted, a communication can be performed
at a speed n times that in a serial communication.
When the data conversion apparatus shown in FIGS. 2 and 3 is connected to a
personal computer and a printer, a high-quality communication can be
performed between the personal computer and the printer.
[Second Embodiment (FIGS. 4 and 5)]
FIG. 4 is a block diagram showing the arrangement of a transmission system
of a radio processor of a telephone exchange system according to the
second embodiment of the present invention, and FIG. 5 is a block diagram
showing the arrangement of a reception system of the radio processor. This
embodiment exemplifies a telephone exchange system in which the number of
spread code generators in the first embodiment is decreased, and its
overall arrangement is the same as that shown in FIG. 1.
A data transmission operation will be described below with reference to
FIGS. 1, 4, and 5.
In the transmission system shown in FIG. 4, a serial baseband signal 201 is
converted into n-channel parallel data by a serial/parallel converter 202
comprising, e.g., shift registers. In this process, a data transmission
speed can be decreased to 1/n.
On the other hand, a first spread code generated by a first spread code
generator 203 is input to n different delay circuits 241 to 243. A delay
time is selected to be shorter than a time corresponding to one period of
a spread code pattern, and the delay circuits have different delay times.
Furthermore, a second spread code generator 208 generates a second spread
code in synchronism with the first spread code. The second spread code is
used to attain synchronization at the reception side, and has the same
length as that of the first spread code.
The n-channel parallel data output from the serial/parallel converter 202
are spread-modulated using the n spread codes having different phases by
spread modulators 251 to 253. More specifically, each data is modulo-2
added to the corresponding spread code. The spread-modulated data are
added to each other by an adder 206 in an analog manner so as to be
converted into 1-channel data.
A mixing circuit 210 mixes the output from the second spread code generator
208 and an output from a local oscillator 209, and a multiplier 211
multiplies the output from the adder 206 with the output from the mixing
circuit 210. The product data is amplified by an amplifier 212, and the
amplified data is transmitted as a radio signal from a multiplexer to an
external circuit.
The reception system shown in FIG. 5 also uses two different inverse spread
codes like in the transmission system. A first inverse spread code
generated by the first inverse spread code generator 222 is input to n
different delay circuits 261 to 263, thereby generating n inverse spread
codes having different phases. Furthermore, a second inverse spread code
generator 223 generates a second inverse spread code in synchronism with
the first inverse spread code.
The code patterns of the first and second inverse spread codes and the
delay times of the delay circuits 261 to 263 of the reception side
coincide with those of the transmission side.
When a radio signal transmitted from the transmission side is received, the
reception signal is input to an SAW (Surface Acoustic Wave) convolver 215.
The SAW convolver 215 also receives a signal 225 obtained by mixing the
output from the second | | |
