JP2003051806A - Transmitter for multicarrier-cdma modulation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a receiver side to detect and correct the carrier frequency errors equivalent to ±1/2 or more the subcarrier interval (1/T). SOLUTION: A storage circuit 21 stores a long preamble subcarrier modulation signal S12 to generate a preamble signal PL with a length T, a storage circuit 22 stores a short preamble subcarrier modulation signal S13 to generate a preamble signal PS with a length T/2 for example, a signal S12-S13-S2 comprising 4 consecutive signals S13, 2 consecutive signals S12 and a signal S2 resulting from modulating the subcarrier with data and arranged in this order is serial- parallel converted, a plurality of parallel signals S5 are copied on the frequency base, a spread code S7 is multiplied with copy outputs S6, the multiplication output is subjected to inverse fast Fourier transform, and a multicarrier modulation signal is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a digital radio communication system, and is a multicarrier-CDMA in which a subcarrier (subcarrier) is modulated by input data and the subcarrier modulation signal is spread by a spreading code.
(Multi Carrier-Codedivisi
MC-CDMA transmission apparatus for transmitting a signal of an on multiple access modulation scheme, and in particular, a preamble signal transmitted in addition to a data signal at the beginning of the transmission signal for use in detection and correction of carrier frequency error Related to the generation configuration of.

[0002]

2. Description of the Related Art A multi-carrier modulation / demodulation method is a method of transmitting information using a plurality of subcarriers. The plurality of subcarriers are, for example, quadrature phase modulation: QPSK according to different input data signals for each subcarrier.
(Quadrature phase shift k
eyeing) or the like. In this multi-carrier modulation method, the orthogonal multi-carrier modulation method in which the frequencies of the sub-carriers have an orthogonal relationship is the orthogonal frequency division multiplexing (O
FDM: Orthogonal frequency
It is also called an "ivition multiplexing" modulation method, and is widely applied to a wireless communication system in which multipath (multipath) propagation is a problem.

The multi-carrier modulation system is a modulation system that is not easily affected by multipath and is suitable for wideband transmission.
Wideband transmission is realized under a limited frequency, and, for example, the frequency utilization area (cell) in the mobile communication system is
In the case of expanding in a plane and separating the usages by repeating the used frequency, the occupied bandwidth per carrier (main carrier) is large and the frequency becomes insufficient. In this case, if an attempt is made to expand the area by frequency segregation, the same frequency will be repeatedly used in neighboring cells, and co-channel interference cannot be avoided. In this case, the characteristics of the multi-carrier modulation method are greatly deteriorated.

On the other hand, there is an MC-CDMA modulation system as a modulation system for performing multi-carrier transmission by separating each user (user) or each cell by code separation at the same frequency. This is a modulation method that adopts a code division method using a spread code before inputting to an inverse fast Fourier transform (IFFT) stage that generates a multicarrier modulation signal. In the MC-CDMA modulation method, the subcarrier modulation signal after serial / parallel conversion is duplicated over a plurality of N subcarriers in the frequency axis direction. The N sub-carrier modulated signals thus duplicated are multiplied by the spreading code in the frequency axis direction. For this spread subcarrier modulation signal, I
FFT is performed to generate a multi-carrier modulated signal. However, if this is left as it is, the transmission speed will be reduced to 1 / N.

To avoid this, MC-CD is usually used.
Since the spreading code of MA is an orthogonal code, it is possible to prevent a decrease in transmission rate due to spreading processing by performing code multiplexing using a plurality of spreading codes at the same time in the local station. Alternatively, segregation using a spreading code can be realized by allocating orthogonal codes to other users and cells. MC-CDM
The A modulation method is basically the same as OFDM, and in order to improve the frequency utilization efficiency, each subcarrier is narrowed, and the frequency spacing fsub of the subcarriers is fsub = 1 / T at which orthogonality is satisfied. (Where T = window time of the inverse Fourier transform circuit used to generate the multicarrier batch modulation signal). Therefore,
Compared with the single carrier modulation method, it is more susceptible to the carrier frequency error caused by the error of the local oscillator between the transmitter and the receiver, and an automatic frequency control (AFC) circuit for correcting the carrier frequency error is essential.

In order to detect a carrier frequency error between transmission and reception, there is a method of repeatedly transmitting a preamble signal at the beginning of a transmission signal (Reference: Shin et al., Study of "broadband packet" radio access, IEICE). Technical Report on Communication, RCS2000-136, 2000-1
0). In order to detect the carrier frequency error from this repetitive signal, there are various error detection methods in the demodulator (reference document: Onizawa et al., "OFDM modulation / demodulation circuit", Japanese Patent No. 3097634), which are repeatedly transmitted. A general method is to detect and correct the phase rotation caused by the carrier frequency error between the preamble signals.

A block diagram of a conventional transmitter for MC-CDMA modulation system is shown in FIG. 5, and its operation will be described below. Further, FIG. 6B shows an explanation of the preamble signal under the frame control in the prior art. The input data S1 is
It is input to the subcarrier signal modulator 11,
For example, the QPSK subcarrier modulation signal S2 is output. This subcarrier signal S2 is a complex signal sequence.
The preamble signal S3 is input to the switching circuit 12, the subcarrier modulation signal S2 is sequentially input, and the subcarrier signal S4 is output. The subcarrier signal S4 is input to the serial / parallel conversion circuit 13, and the subcarrier signal S4 input in time series is serial / parallel converted to be a subcarrier signal S5 arranged in parallel. In the subcarrier signal duplication circuit 14, each of the subcarrier signals arranged in parallel is copied in the frequency axis direction by an amount corresponding to the spread code length N, and becomes the subcarrier copy signal S6. The spreading code generation circuit 15 generates a spreading code S7 having a code length N, and the multiplication circuit 16 multiplies each subcarrier copy signal S6 by the spreading code S7 to form a spreading subcarrier signal S8. These spread subcarrier signals S8 are input to the IFFT circuit 17 and subjected to inverse fast Fourier transform to generate a multicarrier (batch) modulated signal, which is output as a multicarrier signal S9. The guard interval addition control circuit 18 outputs a guard interval addition control signal S10. In the parallel-serial conversion circuit 19, the multicarrier modulation signal S9
And the guard interval addition control signal S10 are input, the guard interval GI is inserted and added for each symbol of the multi-carrier modulation signals S9 and S8, and output as the transmission signal S11.

Thus, for example, as shown in FIG. 6B, the guard interval GI and the symbol of length T are repeated after the two preamble signals P of length T to form the data portion. As described above, in the conventional MC-CDMA transmitter shown in FIG. 5, MC-CDMA is used.
A preamble signal is added to the beginning of the signal for transmission. The demodulator on the receiving side uses this preamble signal to detect and correct the carrier frequency error, which is essential for demodulation in the multicarrier modulation method.

[0009]

The MC-CDMA modulation system, which is one of the multi-carrier modulation systems, is affected by the carrier frequency error of the local oscillator between transmission and reception, and the error rate characteristic is greatly deteriorated. AFC that suppresses influence
Is required on the receiving side. This AFC is detection-corrected based on the preamble signal, which is repeatedly transmitted to the head of the transmission signal. The amount of phase rotation between the preamble signals is detected to detect and correct the carrier frequency error.

However, in the conventional MC-CDMA modulation system transmitter, the preamble signal P having the same time length T as the window time length T used in the IFFT circuit 17 is repeatedly transmitted. In the example of FIG. 6B, the number of preamble signals is two. The repeatable period T of the preamble signal determines the range of detectable carrier frequency error. When the time length of the preamble signal P is set to the same time length T as the transmission data symbol, the carrier frequency is limited to a very limited range of ± 1/2 of the subcarrier interval (= 1 / T). No error can be detected.
When a carrier frequency error that is ± 1/2 or more of the subcarrier interval is added to the received signal, the carrier frequency error cannot be detected and corrected, and the characteristic is significantly deteriorated. There is also a problem that the packet synchronization may not be possible.

Particularly, in the packet signal transmitted at an arbitrary timing, not when the frame is assembled and the transmission is continuously performed as in the prior art, the timing synchronization must be established only by the one packet. I won't. Since the carrier frequency error also has a great influence on this timing synchronization, the characteristic deterioration when the carrier frequency error is large is serious in the reception of the packet signal. In the packet communication, when the packet does not reach the receiver, there is a problem that the upper layer packet retransmission function operates according to an arbitrary algorithm and the throughput decreases.

Further, in the MC-CDMA modulation system, since it is possible that the frequency band is used simultaneously with other cells and other users, it may be mixed with a transmitter to which an inexpensive local oscillator is applied. In this environment, when the code used by the transmitter of another user is detected and the multi-user detection-like signal processing that performs separation based on the detection result is considered, the carrier frequency error is large. The inability to detect signals from other user transmitters is a very big problem because multi-user detection becomes impossible. Furthermore, wireless LA
In a system in which it is desirable to use an inexpensive product while allowing some performance degradation such as N (Local Area Network), the detection range of the carrier frequency error is extremely limited as described above. If a compensation function that improves frequency stability accuracy is essential,
This is a big problem that forces you to choose expensive devices.

In addition, in the prior art, the IFFT circuit, which requires a long time to process the preamble signal, is also operated. When signals are continuously transmitted by forming frames, there is a low demand for shortening the time required for synchronization. However, CSMA / CA (Carrier Sen)
se multiple access / Collis
If the operation is performed according to a protocol such as Ion Aviation, SIFS (Short in
Shortening the unit time called ter frame space is important for improving the throughput. However, even for the preamble signal of the known signal as in the prior art,
Performing the IFFT process every time leads to a decrease in throughput.

A first object of the present invention is that a carrier frequency error, which occurs when various compensation functions in an oscillator for improving frequency stability are not used, is as large as ± 1/2 or more of a subcarrier interval. Even when a carrier frequency error is added, the receiver side includes a preamble signal generation circuit that can detect and correct the carrier frequency error.
An object of the present invention is to provide a transmitter for MC-CDMA modulation system. A second object of the present invention is to provide a transmitter for MC-CDMA modulation system that can achieve the first object and can generate a preamble signal in a short time.

[0015]

According to the present invention, before the repetitive transmission of the preamble signal having the same time length as the window time length T of the IFFT transmitted by the prior art, the repetitive time Ts (where Ts <T) is set. The first pre-amble signal is configured to be repeatedly transmitted.
Achieve the purpose of. In addition, the second object is achieved by using a preamble signal that has been converted into a signal on the time axis in advance. According to the present invention, by using the short preamble signal repeatedly transmitted, the detection range of the carrier frequency error can be expanded to (± 1/2) × (1 / Ts). For example, when 4 × Ts = T,
Since the short preamble signal that is repeatedly transmitted in 1/4 time of the conventional preamble signal is also transmitted, it is possible to detect and correct an error up to 4 times the carrier frequency error.

In particular, when the present invention is applied to a packet signal which is transmitted fragmentarily rather than a signal which is continuously transmitted in a frame, there is a problem in the prior art (± 1/2). When a carrier frequency error of × (1 / T) or more is added, the influence of the carrier frequency error on the timing synchronization can be suppressed. In packet communication in which frames are not transmitted and received, synchronization of packets is not established, which means that the packets do not arrive. If the packet does not reach the receiver, the upper layer retransmission function operates according to an arbitrary algorithm,
Since packet retransmission is started, the throughput decreases. In the reception of a packet signal, the characteristic deterioration is serious when the carrier frequency error is large, but this problem can be solved fairly.

Furthermore, in the MC-CDMA modulation system, it is possible that the frequency band is used simultaneously with other cells and other users, so that it may be mixed with a transmitter to which an inexpensive local oscillator is applied. Even in this environment, it is possible to detect the signal of the transmitter of another user having a large carrier frequency error, and there is an effect that the feasibility of multi-user detection and the like is also increased. Further, by applying the present invention, it becomes possible to use a low-cost product such as a wireless LAN with reduced power consumption. To increase the frequency stability of the carrier frequency,
For example, in order to suppress frequency stability, an oscillator using a temperature compensation circuit called TCXO (temperature compensated crystal oscillator) is used. Besides, there are various compensation functions, but there is a great practical effect that the requirement for these compensation functions can be relaxed.

Further, among various conceivable configurations of the present invention, for example, a configuration in which a preamble signal is stored as a signal on a time axis for transmission and is transmitted before the conventional preamble signal without performing IFFT processing. If it is realized by using, it is possible to shorten the processing time in the IFFT. Therefore, it becomes possible to shorten the SIFS time, which has a great influence on the throughput of the wireless LAN, and it is expected that the throughput is improved. In the invention described in claim 1, the subcarrier is modulated by the input data by the modulation means, and the long preamble subcarrier modulation signal for generating the long preamble signal is stored in the first storage means, A short preamble subcarrier modulation signal for generating a short preamble signal shorter than the long preamble signal is stored in a second storage means, and is provided between the first storage means and the first switching means. A first switching unit is provided, and the short preamble subcarrier modulation signal from the second storage unit and the long preamble subcarrier modulation signal from the first storage unit are sequentially switched by the second switching unit and output. And a short preamble subcarrier modulation signal output from the first switching means, Ng preamble subcarrier modulation signal, the data subcarrier modulation signal from the modulation means is sequentially switched by the second switching means, the output signal of the first switching means serial-parallel conversion by the serial-parallel conversion means, A plurality of the serial-parallel converted subcarrier modulated signals are copied in the frequency axis direction by the duplicating means, and the spreading code produced by the spreading code producing means and each output signal of the duplicating means are produced by the multiplying means in the frequency direction. The spread subcarrier signals, which are multiplied by these multiplication output signals, are inverse-Fourier-transformed by the inverse-Fourier-transforming means to perform multicarrier batch modulation, and a guard interval addition operation is performed in parallel-serial conversion on the multicarrier-modulated signal. And a transmission signal is generated.

According to the first aspect of the present invention, in the MC-CDMA modulation type transmitter for the packet signal transmitted at an arbitrary timing, the short preamble signal is transmitted before the long preamble signal, and the carrier frequency error It is possible to widen the detection range beyond the subcarrier interval. Further, since the long preamble subcarrier modulation signal and the short preamble subcarrier modulation signal are stored respectively, the processing time as a whole becomes shorter than the case where these are generated each time. According to the invention described in claim 2, on the premise of the invention described in claim 1, the frame synchronization control means outputs a control signal for performing frame synchronization control from the frame synchronization signal, and the control signal outputs the input data. The transmission control to the modulation means is performed by the data transmission control means, and the first storage means and the second storage means are controlled by the control signal from the frame synchronization control means, and reading from these is performed. Done.

According to the second aspect of the present invention, in the MC-CDMA modulated signal transmitting apparatus which is transmitted under the frame synchronization control, the carrier is transmitted by transmitting the short preamble signal before the long preamble signal. It is possible to widen the detection range of the frequency error beyond the subcarrier interval. In the invention described in claim 3, the subcarriers are modulated by the input data by the modulation means, the data subcarrier modulation signals are serial-parallel converted by the serial-parallel conversion means, and these parallel data subcarrier modulation signals are copied by the duplication means. Multiple copies are made in the frequency axis direction,
The multiplication unit multiplies the output signal of the duplication unit and the spreading code generated by the spreading code generation unit in the frequency direction, and the inverse Fourier transform unit inverts the spread subcarrier signal that is the output signal of the multiplication unit. Fourier transform is performed to perform multi-carrier batch modulation, operation of adding a guard interval to the multi-carrier modulation signal is performed by the parallel-serial conversion means, and the signal in the time domain of the long preamble signal is stored in the first storage means. The signal in the time domain of the short preamble signal, which is shorter than the long preamble signal, is stored in the second storage means, and the long preamble signal from the first storage means and the second storage means are stored. And the short preamble signal of are sequentially switched by the first switching means, and the output of the first switching means Sequentially by the output multi-carrier modulated signal and the second switching means preamble signal and the parallel-serial converting means, and output is switched.

According to the third aspect of the present invention, in the MC-CDMA modulation type transmitter for the packet signal transmitted at an arbitrary timing, the carrier frequency is transmitted by transmitting the short preamble signal before the long preamble signal. It is possible to widen the error detection range to a subcarrier interval or more, and prepare a preamble signal on the time axis and perform IFFT processing to prevent a decrease in throughput. In the invention described in claim 4, on the premise of the invention of claim 3, the frame synchronization control means outputs a control signal for performing frame synchronization control from the frame synchronization signal, and the control signal causes the input data Transmission control to the subcarrier modulation means is performed by the data transmission control means, and read-out to the first storage means and the second storage means is controlled by a control signal from the frame synchronization control means.

According to the invention of claim 4, in the MC-CDMA modulated signal transmitting apparatus which is transmitted under the frame synchronization control, by transmitting the short preamble signal before the long preamble signal, the carrier is transmitted. It is possible to widen the detection range of the frequency error beyond the subcarrier interval, and by preparing the preamble signal on the time axis and performing the IFFT process, it is possible to avoid a decrease in throughput. In the present invention, with the configuration described above, the repetition time Ts (however, Ts <T) is transmitted before repeatedly transmitting the preamble signal having the same time length as the window time length T of the IFFT transmitted by the conventional technique.
The short preamble signal transmitted in step S1 is repeatedly transmitted, and the problem of the prior art when the carrier frequency error is detected and corrected by the receiver is solved.

That is, according to the invention, the subcarrier spacing ±
It is possible to realize an MC-CDMA modulation signal transmission device including a preamble signal generation circuit capable of generating a short preamble signal, which enables detection and correction of a carrier frequency error when a carrier frequency error of ½ or more is added.

[0024]

DETAILED DESCRIPTION OF THE INVENTION MC-CD according to the invention of claim 1.
FIG. 1 shows an embodiment of a transmission device for MA modulation system. The parts corresponding to those of the conventional device shown in FIG. 5 are designated by the same reference numerals. In this embodiment, a frequency domain long preamble signal storage circuit 21 is provided, and this storage circuit 21 is provided.
The long preamble subcarrier modulation signal S12 for generating the long preamble signal is stored in the. Further, a frequency domain short preamble signal storage circuit 22 is provided, and the storage circuit 22 stores the short preamble subcarrier modulation signal S13. The switching circuit 23 sequentially switches the short preamble subcarrier modulation signal S13 for generating the short preamble signal and the long preamble subcarrier modulation signal S12 from the storage circuit 22 and outputs the short preamble subcarrier modulation signal S12.

The preamble subcarrier modulation signal S14 output from the switching circuit 23 and the data subcarrier modulation signal S2 from the subcarrier signal modulator 11 are sequentially switched by the switching circuit 12 and are serially paralleled as a subcarrier modulation signal S4. It is input to the conversion circuit 13. The serial-parallel conversion circuit 13 performs serial-parallel conversion, and further, in the subcarrier signal duplication circuit 14, the parallel subcarrier signal S5 is copied in the frequency axis direction by an amount corresponding to the spread code length N. Signal S6 and spreading code S
7 is performed, and the multiplied and spread subcarrier signal 8 is converted into an inverse fast Fourier transform, that is, multicarrier batch modulation is performed, and a multicarrier signal S8 is generated.
Further, under the control of the guard interval addition control signal S10, the guard interval GI is inserted and added to the multicarrier modulation signal S9, and the transmission signal S11 is output.

In the frame structure of the transmission signal S11 in this case, as shown in FIG. 6A, for example, a plurality of short preamble signals P _s are first repeated, and four short preamble signals P _s are repeated in the figure, and then a plurality of long preambles, two long preambles in the figure. The length Ts of the short preamble signal P _S is shorter than the length T of the long preamble signal P _L , in which the signal P _L is repeated, followed by a data portion in which a pair of guard interval GI and symbol data is repeated. In the example shown, 2Ts = T. T is 1 symbol length to guard interval GI
It is equal to the value after subtracting.

FIG. 2 shows an embodiment of a transmission device for MC-CDMA modulation system according to the invention of claim 2, and parts corresponding to those in FIG. 1 and FIG. In this embodiment, the frame synchronization signal S16 is input to the frame synchronization control circuit 25, and the control signal S17 for controlling the transmission of the signal synchronized with the frame is output. The frequency domain long preamble signal storage circuit 21 is read out and controlled by the control signal S17, and the long preamble subcarrier modulation signal S12 is output in a predetermined section in the frame. The frequency domain short preamble signal storage circuit 22 is also read-controlled in accordance with the control signal S17, and the short preamble subcarrier modulation signal S13 is output in a predetermined section in the frame.

On the other hand, the input data S1 is input to the data transmission control circuit 26. Here, the input data S1 is transmitted as the data S18 as the subcarrier signal modulator so that the transmission is performed at the timing of the transmittable frame according to the control signal S17. 11 is supplied. The processing after the data subcarrier modulation signal S2 and the preamble subcarrier modulation signal S14 are sequentially switched and output by the switching circuit 12 is the same as that shown in FIG. In this case, the transmission signal S11 is not a packet, but one frame is made up of a short preamble signal P _S , a long preamble signal P _L, and a data portion following it, as shown in FIG. 6A, and this is continuously repeated.

FIG. 3 shows an embodiment of a transmission device for MC-CDMA modulation system according to the invention of claim 3, parts corresponding to those in FIG. 5 are designated by the same reference numerals, and a duplicate description will be omitted.
In this embodiment, a time domain long preamble signal storage circuit 31 is provided, a preamble signal S21 in the time domain is held in this storage circuit 31, a time domain short preamble signal storage circuit 32 is provided, and a time domain short preamble signal is provided. The signal S22 is held.
The switching circuit 33 sequentially switches between the short preamble signal S22 from the storage circuit 32 and the long preamble signal S21 from the storage circuit 31, and outputs it as a preamble signal S23.

On the other hand, the data subcarrier modulation signal S2 from the subcarrier signal modulator 11 is immediately input to the serial / parallel conversion circuit 13. The serial-parallel conversion circuit 13 serial-parallel converts the subcarrier modulation signals, copies the subcarrier modulation signals S5 in the frequency axis direction, and further multiplies the subcarrier copy signal S6 with the spreading code S7 to obtain the spread subcarriers. As in the embodiment of FIG. 1, the signal S8 is subjected to multi-carrier batch modulation by IFFT, and the guard interval GI is additionally inserted to the multi-carrier signal S9. The multi-carrier signal S2 for which the addition of the guard interval has been controlled
Before 4, the switching circuit 34 adds the preamble signal S23 from the switching circuit 33 and outputs the transmission signal S11.

An embodiment of an MC-CDMA modulation system transmitter according to the invention of claim 4 is shown in FIG. 4, and FIG. 2 and FIG.
The same reference numerals are given to the parts corresponding to. In this embodiment, the example shown in FIG. 3 is a case in which frames are repeatedly and continuously transmitted. Therefore, as shown in FIG. 2, a frame synchronization control circuit 25 is provided, and the control signal S17 from this controls the supply of the input data S1 to the subcarrier signal modulator 11 in synchronization with the frame, and the data subcarrier Modulation signal directly, serial transmutation conversion circuit 1
3, and the time domain long preamble signal storage circuit 31 reads out the time domain long preamble signal S21 in accordance with the control signal S17 only in the section permitted to be transmitted in each frame, and the time domain short preamble signal storage circuit 32 also According to the control signal S17, the time domain short preamble signal S22 is read out only in the section permitted to be transmitted in each frame. Otherwise, the operation is similar to that shown in FIGS. Therefore, the transmission signal S11
The frame is, for example, as shown in FIG. 6A.

The length Ts of the short preamble signal is, for example, T / 2, T / 4, T / depending on the requirements of the system.
It may be 8, T / 16 or the like, and is preferably about T / 4. When the time domain long preamble signal and the time domain short preamble signal are used as shown in FIGS. 3 and 4, Ts can be set to an appropriate time of T / 2 to T / 16. Since the long preamble signal P _L and the short preamble signal P _S are transmitted, the receiver detects the carrier frequency error based on the short preamble signal P _S and relatively corrects the error, and then performs the long correction. Using the preamble signal P _L , the carrier frequency error can be detected and highly accurate correction can be performed. The long preamble signal P _L may be omitted in some cases. The number of repetitions of the long preamble signal P _L and the short preamble signal P _S is not limited to 2 and 4 shown in FIG. 6A, and various repetition numbers can be considered. In FIGS. 1 and 2, the memory circuits 21 and 22 are shown.
May be omitted, and a circuit for generating a long preamble subcarrier modulation signal and a short preamble subcarrier modulation signal may be provided. Similarly, in FIGS. 3 and 4, the storage circuits 31 and 32 may be omitted and a circuit for generating a time domain long preamble signal and a time domain short preamble signal may be provided.

[0033]

As described above, by using the multicarrier-CDMA modulation system transmitter of the present invention, it may occur when various compensation functions in an oscillator for improving frequency stability are not used. Subcarrier spacing ±
Even if a carrier frequency error of 1/2 or more is added,
It is possible to solve the problem that it was impossible to detect and correct a carrier frequency error in the past, and to realize a transmitting device including a preamble signal generation circuit capable of detecting and correcting a carrier frequency error using a short preamble signal in a receiver. .

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the invention of claim 1;

FIG. 2 is a block diagram showing an embodiment of the invention of claim 2;

FIG. 3 is a block diagram showing an embodiment of the invention of claim 3;

FIG. 4 is a block diagram showing an embodiment of the invention of claim 4;

FIG. 5 is a block diagram showing a conventional MC-CDMA packet transmission device.

6A is a diagram showing an example of a frame structure of a signal transmitted by the device according to the present invention, and FIG. 6B is a diagram showing a frame structure of a signal transmitted by a conventional device.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masahiro Morikura             2-3-1, Otemachi, Chiyoda-ku, Tokyo             Inside Telegraph and Telephone Corporation F term (reference) 5K022 EE02 EE11 EE22 EE32 FF01

Claims (4)

[Claims] 1. A modulation means for modulating a subcarrier according to input data, a first storage means for storing a long preamble subcarrier modulation signal for generating a long preamble signal, and a storage means shorter than the long preamble signal. Second storage means for storing a short preamble subcarrier modulation signal for generating a short preamble signal; and a second storage means provided between the first storage means and the second storage means. A short preamble subcarrier modulation signal from the first storage means and a long preamble subcarrier modulation signal from the first storage means are input, and are sequentially switched and output, and are output from the first switching means. Short preamble subcarrier modulation signal, long preamble subcarrier modulation signal A second switching means to which the data subcarrier modulation signal from the modulating means is input and which is sequentially switched and output; a serial-parallel conversion means for converting the output signal of the second switching means to serial-parallel conversion; Copying means for copying a plurality of subcarrier modulated signals from the serial / parallel converting means in the frequency axis direction, spreading code generating means for generating spreading code, spreading code output from the spreading code generating means, and Multiplication means for multiplying the output signal in the frequency direction; inverse Fourier transform means for performing an inverse Fourier transform on the spread subcarrier modulation signal that is the output signal of the multiplication means to obtain a multicarrier modulation signal; The multi-carrier modulation signal from the Fourier transform means is input, and the multi-carrier modulation signal is converted while the guard interval is added. A multi-carrier-CDMA (Code division multi) having parallel-serial conversion means for outputting in time series and generating a transmission signal.
Ple access) Transmitter for modulation system. 2. The multi-carrier-CD according to claim 1.
In the MA transmitter, a frame synchronization signal is input, a frame synchronization control unit that outputs a control signal for performing frame synchronization control, and a control signal from the frame synchronization control unit are input.
A data transmission control means for controlling transmission of the input data to the modulation means, and a long preamble subcarrier modulation signal from the first storage means and the second storage means according to a control signal from the frame synchronization control means. A means for outputting the short preamble subcarrier modulated signal to the first switching means, and multi-carrier-CDMA.
Modulation transmitter. 3. Modulation means for modulating a subcarrier by input data, serial-parallel conversion means for converting an output data subcarrier modulation signal from the modulation means in serial-parallel, and data subcarrier modulation signal in the serial-parallel conversion means. Copying means for copying a plurality in the frequency axis direction, spreading code generating means for generating a spreading code, multiplication code for multiplying the spreading code from the spreading code generating means, and the output signal of the copying means in the frequency direction, An inverse Fourier transform unit for performing an inverse Fourier transform on the spread data subcarrier modulation signal from the multiplication unit to obtain a multicarrier modulation signal, and a multicarrier modulation signal from the inverse Fourier transform unit are input, and a guard Parallel-to-serial conversion that outputs multi-carrier modulated signals in time series while adding intervals Means, first storage means for storing a long preamble signal, second storage means for storing a short preamble signal shorter than the long preamble signal, and a long preamble signal from the first storage means,
First switching means for sequentially switching and outputting the short preamble signal from the second storage means, a preamble signal output from the first switching means, and a multicarrier modulation signal from the parallel-serial conversion means. And a second switching means for sequentially switching and outputting the multi-carrier-CDMA modulation method transmitting device. 4. Multi-carrier-CD according to claim 3.
In a modulator for MA, a frame synchronization signal is input, and a frame synchronization control unit that outputs a control signal for performing frame synchronization control; and a control signal from the frame synchronization control unit transmits the input data to the modulation unit. Data transmission control means for controlling, a long preamble signal from the first storage means and a short preamble signal from the second storage means according to the control signal from the frame synchronization control means, and the second switching means. And a means for outputting to the multicarrier-CDMA modulation system transmitter.