KR100574125B1 - Orthogonal frequency-division multiplex transmission system, and its transmitter and receiver - Google Patents

Abstract

The received OFDM signal is transformed from the time domain to the frequency domain by Fourier transform 12 to obtain a vector sequence for each carrier in the frequency domain. The necessary distributed and terminated pilot signals are extracted from this vector sequence (13), divided by modulated complex vectors (15) to estimate the channel characteristics for the distributed / terminated pilot signals, and the channel characteristics are interpolated (16) to synchronize. The channel characteristics of the information transmission carrier of the detection segment are estimated. On the other hand, the vector sequence obtained by the Fourier transform is delayed by one symbol (17), the interpolation output is selected in the case of the synchronous detection segment, and the delay output is selected in the case of the differential detection segment (18). Divide by the selective output to perform synchronous or differential detection (19) and demodulate to obtain digital information (20). As a result, high quality demodulation and demodulation suitable for mobile reception can be realized.

Description

Transmission method, reception method, transmission apparatus, and reception apparatus {ORTHOGONAL FREQUENCY-DIVISION MULTIPLEX TRANSMISSION SYSTEM, AND ITS TRANSMITTER AND RECEIVER}

1 is a diagram showing an arrangement example of synchronous detection or differential detection segments (13 segments in total) and band-ended pilot signals in Embodiments 1 and 2 of the OFDM transmission method according to the present invention;

2 shows arrangement of additional information transmission signals, arrangement of distributed pilot signals in a synchronous detection segment, and termination pilot signals in a differential detection segment in Embodiments 1 and 2 of the OFDM transmission method according to the present invention. An example drawing,

3 shows arrangement of a continuous pilot signal and a control information signal, arrangement of distributed pilot signals in a synchronous detection segment, and termination pilot signals in a differential detection segment in Embodiment 2 of the OFDM transmission method according to the present invention. Drawing showing an arrangement example,

4 is a time-amplitude characteristic diagram showing an inverse Fourier transform pair in frequency configuration of a continuous pilot signal of a synchronous detection segment shown in Table 2 in Embodiment 2 of the OFDM transmission scheme according to the present invention;

FIG. 5 is a time-amplitude characteristic diagram showing an inverse Fourier transform pair in frequency configuration of a continuous pilot signal of a differential detection segment shown in Table 2 in Embodiment 2 of the OFDM transmission scheme according to the present invention; FIG.

6 is a time-amplitude characteristic diagram showing an inverse Fourier transform pair in frequency configuration of a control information signal of a synchronous detection segment shown in Table 3 in Embodiment 2 of the OFDM transmission scheme according to the present invention;

7 is a time-amplitude characteristic diagram showing an inverse Fourier transform pair in frequency configuration of a control information signal of a differential detection segment shown in Table 3 in Embodiment 2 of the OFDM transmission scheme according to the present invention;

8 is a block circuit diagram showing a structure of a transmission apparatus used for an OFDM transmission method according to Embodiment 5 of the present invention;

9 is a block circuit diagram showing the structure of a receiving apparatus used for the OFDM transmission method according to the sixth embodiment of the present invention;

10 is a block circuit diagram showing the configuration of a receiving apparatus used in a conventional OFDM transmission method.

Explanation of symbols for the main parts of the drawings

11: tuner 12: Fourier transform circuit

13 distributed / terminated pilot extraction circuit 14 vector generating circuit

15: division circuit 16: interpolation circuit

17: delay circuit 18: selection circuit

19: division circuit 20: demodulation circuit

21: continuous pilot extraction circuit 22: vector generation circuit

23 division circuit 24 inverse Fourier transform circuit

51: information transmission signal generation circuit 52: additional information signal generation circuit

53: Distributed Pilot Signal Generation Circuit 54: Terminated Pilot Signal Generation Circuit

55: band termination pilot signal generation circuit

56: control information generation circuit 57: carrier arrangement circuit

58: inverse Fourier transform circuit 59: quadrature modulation circuit

60: frequency conversion circuit

The present invention relates to an orthogonal frequency division multiplexing scheme in which signals suitable for fixed reception and mobile reception are mixed and transmitted on one channel. The present invention also relates to a transmitting apparatus for forming and transmitting an OFDM signal based on the orthogonal frequency division multiplexing method, and a receiving apparatus for receiving and demodulating OFDM signals formed and transmitted based on the orthogonal frequency division multiplexing method.

Currently, a transmission method using orthogonal frequency division multiplexing (hereinafter, referred to as OFDM) technology has been studied as a digital broadcasting method in terrestrial TV broadcasting. This OFDM transmission method is a kind of a multi-carrier modulation method, which modulates a plurality of carriers in a frequency relationship orthogonal to each other to transmit digital information. As described above, since the digital information is divided into a plurality of carriers and transmitted, as described above, the symbol period length of the divided digital information for modulating one carrier becomes long and is affected by delay waves such as multipath. It has a difficult characteristic.

As a digital broadcasting method of a TV signal using a conventional OFDM transmission technique, for example, the DVB-T standard in Europe, that is, ETSI 300 744 (ETSI: European Telecommunication Standards Institute).

The conventional OFDM transmission method uses a carrier of 1705 carriers in all transmission bands in, for example, 2k mode (2k means 2048 samples of fast Fourier transforms when generating an OFDM signal). 142 carriers in a scattered pilot signal, 45 carriers in a continuous pilot signal, 17 carriers in a control information (TPS) signal, 1512 carriers in an information transmission signal We use for.

However, among the continuous pilot signals of the carrier of 45 carriers, the continuous pilot signals of the 11 carrier carriers are arranged overlapping with the distributed pilot. In addition, the distributed pilot signal is arranged in 12 carrier periods in frequency arrangement in one symbol, and is arranged in shifts of three carriers in each symbol, and the time arrangement is in 4 symbol periods.

Specifically, when carrier number k is set from 0 to 1704 and symbol number n in the frame is 0 to 67 in order from the end, the distributed pilot signal is arranged on the carrier of carrier number k according to equation (1). In Formula (1), mod represents a surplus operation and p is an integer of 0 or more and 141 or less.

Continuous pilot signals include carrier number k = {0, 48, 54, 87, 141, 156, 192, 201, 255, 279, 282, 333, 432, 450, 483, 525, 531, 618, 636, 714, 759 , 765, 780, 804, 873, 888, 918, 939, 942, 969, 984, 1050, 1101, 1107, 1110, 1137, 1140, 1146, 1206, 1269, 1323, 1377, 1491, 1683, 1704 Disposed on the carrier.

These distributed and continuous pilot signals are obtained by modulating a carrier wave by a complex vector c _{k, n} shown in Equation 2 on the basis of the PN (pseudo random number) series w _k corresponding to the carrier number k arranged, respectively. Lose. In Equation 2, Re {c _{k, n} } represents a real part of a complex vector c _{k, n} corresponding to a carrier number k and a symbol number n, and Im {c _{k, n} } represents an imaginary part.

In addition, a control information signal called TPS (Transmission Parameter Signaling) includes carrier number k = {34, 50, 209, 346, 413, 569, 595, 688, 790, 901, 1073, 1219, 1262, 1286, 1469, 1594. 1687}, and transmits one bit of control information for each symbol.

If the control information bit transmitted in the symbol of symbol number n is Sn, the control information signal is obtained by modulating the carrier wave by the complex vector c _{k, n} shown in equation (3). That is, the carrier wave transmitting the control information signal is differentially shifted keyed (PSK) modulated between symbols.

However, at the head symbol (symbol number n = 0) of the frame, the carrier wave for transmitting control information is modulated by the complex vector c _{k, n} shown in Equation 4 based on the above-described PN series w _k .

The carrier of the 1512 carrier used for the information transmission signal other than the above is QPSK, 16QAM, or 64QAM modulated based on digital information. All modulation methods are also absolute phase modulation.

Fig. 10 shows an example of a conventional receiving apparatus for receiving the OFDM signal generated in this way and demodulating digital information.

In FIG. 10, the received OFDM signal is frequency-converted by the tuner 101, time-frequency-converted by the Fourier transform circuit 102, and becomes a vector sequence for each carrier in the frequency domain. This vector string is supplied to the distributed pilot extraction circuit 103 and the continuous pilot extraction circuit 109.

The distributed pilot extraction circuit 103 extracts the distributed pilot signal from the vector string output by the Fourier transform circuit 102. The vector generation circuit 104 generates a modulated complex vector c _{k, n} corresponding to the distributed pilot signal extracted by the distributed pilot extraction circuit 103. The division circuit 105 divides the distributed pilot signal extracted by the distributed pilot extraction circuit 103 into a complex vector generated by the vector generation circuit 104, and estimates transmission path characteristics relating to the distributed pilot signal from the division result.

The interpolation circuit 106 interpolates the channel characteristics relating to the distributed pilot signal obtained by the division circuit 105, and estimates these channel characteristics for all carriers. The division circuit 107 performs synchronous detection by dividing the vector sequence output from the Fourier transform circuit 102 by the transmission path characteristics estimated by the interpolation circuit 106 for the corresponding carrier. The demodulation circuit 108 demodulates the synchronous detection signal output from the division circuit 107 in accordance with a modulation method (QPSK, 16QAM, 64QAM, etc.) when generating the information transmission signal, to obtain the transmitted digital information.

In addition, the continuous pilot extraction circuit 109 extracts the continuous pilot signal from the vector string output by the Fourier transform circuit 102. The vector generation circuit 110 generates a modulation complex vector c _{k, n} corresponding to the continuous pilot signal extracted by the continuous pilot extraction circuit 109. The division circuit 111 estimates transmission path characteristics of the continuous pilot signal by dividing the continuous pilot signal extracted by the continuous pilot extraction circuit 109 into a complex vector generated by the vector generation circuit 110. The inverse Fourier transform circuit 112 frequency-time converts the transmission path characteristics of the continuous pilot signal estimated by the division circuit 111 to obtain an impulse response characteristic of the transmission path.

However, in the conventional OFDM transmission system, absolute phase modulation by QPSK, 16QAM, 64QAM, etc. is performed to modulate a carrier wave for transmitting digital information, and a transmission path characteristic estimated from a distributed pilot whose time is sparse in the demodulation is performed. Since it is assumed that the transmission path characteristics obtained by smooth interpolation are used, sufficient transmission quality may not be obtained in mobile reception in which the transmission path characteristics change rapidly due to fading or the like.

In addition, in the conventional OFDM transmission method, since a single modulation method for each carrier is defined in the entire band, it is suitable for mobile reception for modulation of a carrier for transmitting digital information so that some digital information can be received while moving. Even if differential QPSK modulation is introduced, the overall transmission capacity is reduced, resulting in poor efficiency.

In addition, since the continuous pilot signal is disposed on any one of carriers of a predetermined carrier interval A, the effective symbol period length (inverse of the minimum frequency interval of the carrier) is applied to the impulse response characteristic of the transmission path that can be estimated from the continuous pilot signal. Occurs the return of A / 1.

Therefore, the present invention solves the above problems, introduces a modulation scheme suitable for partial mobile reception in modulation of a carrier wave for transmitting digital information while maintaining the overall transmission capacity, and also estimates a transmission path from a continuous pilot signal. It is an object of the present invention to provide an OFDM transmission method in which a continuous pilot signal is arranged so that a return does not occur in an impulse response, and a transmitter and a receiver suitable for the present method.

In order to solve the above problems, the OFDM transmission method according to the present invention is configured as follows.

(1) In the OFDM transmission method in which digital information is transmitted by modulating a plurality of carriers in a frequency relationship orthogonal to each other at every symbol period,

A predetermined number of carriers are assigned to one or more segments of one of the plurality of carriers, one or more carriers are assigned to a band-ended pilot signal, and the one or more segments are respectively used for synchronous detection or differential detection for each segment. As a method used as either of the dragons,

In the synchronous detection segment, a distributed pilot signal for modulating the carrier with a specific phase and amplitude is disposed on a carrier whose symbol time and frequency are periodically dispersed, and the corresponding carrier is added to a carrier having the same frequency in every symbol according to additional information. M (M is a natural number of two or more) phase-shift keying (M-phase PSK) or a side information transmission signal modulated by differential M-phase phase shift keying in the symbol direction, and the carrier is applied to a carrier other than the above. Arranging an information transmission signal modulated according to the information,

In the differential detection segment, an additional information transmission signal for modulating the corresponding carrier by M phase phase shift keying or differential M phase phase shift keying in the symbol direction is applied to a carrier of the same frequency in every symbol, A terminal pilot signal for modulating the carrier with a specific phase and amplitude is disposed on a carrier whose frequency satisfies the periodicity of frequency allocation of the distributed pilot signal of an adjacent sync detection segment, and the carrier is applied to a carrier other than the above. Arranging an information transmission signal modulated according to the information,

The band-ended pilot signal is arranged at a carrier frequency at the end of a transmission frequency band at a frequency satisfying the periodicity of frequency allocation of the distributed pilot signal in the synchronous detection segment, and modulating the carrier with a specific phase and amplitude. To do so.

(2) In the OFDM transmission method in which digital information is transmitted by modulating a plurality of carriers in a frequency relationship orthogonal to each other at every symbol period,

A predetermined number of carriers are assigned to one or more segments of one of the plurality of carriers, one or more carriers are assigned to a band-ended pilot signal, and the one or more segments are respectively used for synchronous detection or differential detection for each segment. As a method used as either of the dragons,

In the synchronous detection segment, a distributed pilot signal for modulating the carrier with a specific phase and amplitude is disposed on a carrier whose symbol time and frequency are periodically dispersed, and the carrier is assigned a specific phase and amplitude to a carrier of the same frequency in all symbols. A continuous pilot signal modulated by a symbol, and each symbol modulates a carrier information of the same frequency by using M phase phase shift keying or differential M phase phase shift keying in the symbol direction according to additional information. An information transmission signal for modulating the carrier according to the digital information on a carrier other than the above,

In the differential detection segment, a continuous pilot signal for modulating the carrier with a specific phase and amplitude is arranged on a carrier of the same frequency in every symbol, and every symbol is a phase M phase according to additional information. A sub information transmission signal modulated by shift keying or differential M phase phase shift keying in a symbol direction is arranged, and the carrier is replaced with a carrier whose frequency satisfies the periodicity of the frequency arrangement of the distributed pilots of adjacent synchronous detection segments. A terminal pilot signal for modulating at a specific phase and amplitude, and an information transmission signal for modulating the carrier according to the digital information on a carrier other than the above,

The band-ended pilot signal is arranged at a carrier frequency at the end of a transmission frequency band at a frequency satisfying the periodicity of frequency allocation of the distributed pilot signal in the synchronous detection segment, and modulating the carrier with a specific phase and amplitude. To do so.

(3) In the configuration of (1) or (2), the frequency configuration of the additional information transmission signal in the synchronous detection segment and the frequency configuration of the additional information transmission signal in the differential detection segment are partially common. It is decided to arrange.

(4) In the configuration of (1) or (2), in the synchronous detection segment, the frequency configuration of the additional information transmission signal is part of the frequency configuration of the additional information transmission signal of the differential detection segment.

(5) In the configuration of (2), the frequency arrangement of the continuous pilot signal in the synchronous detection segment and the frequency arrangement of the continuous pilot signal in the differential detection segment are partly in common arrangement.

(6) In the configuration of (2), in the synchronous detection segment, the frequency configuration of the continuous pilot signal is a part of the frequency configuration of the continuous pilot signal of the differential detection segment.

(7) In any one of (1) to (6), the additional information includes control information.

(8) In the configuration of (7), the control information is transmitted by differential two-phase phase shift keying (DBPSK) in the symbol direction.

(9) In the configuration of (7), the frequency arrangement of the control information in the synchronous detection segment and the frequency arrangement of the control information in the differential detection segment are partly in common arrangement.

(10) In the configuration of (7), in the synchronous detection segment, the frequency configuration of the control information is part of the frequency configuration of the control information of the differential detection segment.

(11) In any one of (1) to (10), in the synchronous detection segment, the number of carriers is a multiple of N (N is a natural number of two or more), and the distributed pilot signal is an N carrier interval, Each symbol is placed on a carrier wave shifted by L (L is a weak number of N) carriers.

(12) In any one of (1) to (11), in the synchronous detection and differential detection segment, each of the additional information transmission signals is inverse Fourier transform of the frequency configuration of the additional information transmission signal. The pair is placed on a carrier of the same frequency as that of the impulse.

(13) In the configuration of (2), in the synchronous detection and differential detection segments, each of the continuous pilot signals has a frequency equal to that of an inverse Fourier transform pair in frequency configuration of the continuous pilot signal. Place it on the carrier.

(14) In the configuration of (2), in the synchronous detection and differential detection segments, the inverse frequency arrangement in which the additional information transmission signal and the continuous pilot signal are added together with the additional information transmission signal and the continuous pilot signal, respectively. Fourier transform pairs are placed on a carrier with the same frequency as the impulse shape.

(15) In any one of (1) to (14), the same number of carriers are used in the synchronous detection segment and the differential detection segment.

(16) In any one of (1) to (15), the terminal pilot signal is disposed only at a carrier of the band end of the differential detection segment.

(17) In the configuration of (1), a band-ended pilot using 13 segments and 1 carrier is used, one segment is composed of 108 carriers, and a carrier of 1405 carriers is used in the entire band. ,

The synchronous detection segment is composed of a distributed pilot signal using a carrier of 9 carriers per symbol, an additional information transmission signal using a carrier of 3 carriers, and an information transmission signal using a carrier of 96 carriers,

The differential detection segment is composed of an additional information signal using a carrier of 11 carriers, a terminal pilot signal using a carrier of 1 carrier, and an information transmission signal using a carrier of 96 carriers.

(18) In the configuration of (2), the band termination pilot using 13 segments and one carrier is used, one segment is composed of 108 carriers, and a carrier of 1405 carriers is used in the entire band. ,

The synchronous detection segment includes a distributed pilot signal using a carrier of 9 carriers per symbol, an additional information transmission signal using a carrier of 1 carrier, a continuous pilot signal using a carrier of 2 carriers, and a carrier of 96 carriers. Consisting of information transmission signals,

The differential detection segment includes an additional information signal using a carrier of 5 carriers, a continuous pilot signal using a carrier of 6 carriers, a terminal pilot signal using a carrier of 1 carrier, and an information transmission signal using a carrier of 96 carriers. To be configured.

Moreover, the transmission apparatus which concerns on this invention is comprised as follows.

(19) An apparatus for generating an OFDM signal by the orthogonal frequency division multiplex transmission scheme in any one of (1) to (18).

(20) A transmitter for generating an OFDM signal by the orthogonal frequency division multiplexing transmission method of (1),

A predetermined number of carriers are assigned to one or more segments of one of the plurality of carriers, one or more carriers are assigned to a band-ended pilot signal, and the one or more segments are respectively used for synchronous detection or differential detection for each segment. Array means for assigning to either

Signal generation means for generating the distributed pilot signal, the additional information transmission signal, the information transmission signal, the termination pilot signal, and the band termination pilot signal, respectively;

In the arranging means, the band-ended pilot signal is a frequency that satisfies the periodicity of the frequency arrangement of the distributed pilot signals in the synchronous detection segment, and is arranged on a carrier wave in the transmission frequency band stage. For the segment, the distributed pilot signal is disposed on a carrier whose symbol time and frequency are periodically dispersed, the additional information transmission signal is placed on a carrier of the same frequency in every symbol, and the information transmission signal is a carrier other than the above. In the differential detection segment, the additional information transmission signal is placed on a carrier of the same frequency in every symbol, and the terminal pilot signal is periodic in frequency arrangement of the distributed pilot signal of the adjacent synchronous detection segment. On a carrier with a frequency satisfying It was so.

(21) A transmitter for generating an OFDM signal by the orthogonal frequency division multiplexing transmission method of (2),

A predetermined number of carriers are assigned to one or more segments of one of the plurality of carriers, one or more carriers are assigned to a band-ended pilot signal, and the one or more segments are respectively used for synchronous detection or differential detection for each segment. Array means for assigning to either

Signal generation means for generating the distributed pilot signal, the additional information transmission signal, the information transmission signal, the termination pilot signal, the band termination pilot signal, and the continuous pilot signal,

In the arranging means, the band-ended pilot signal is a frequency that satisfies the periodicity of the frequency arrangement of the distributed pilot signals in the synchronous detection segment, and is arranged on a carrier wave in the transmission frequency band end, and the synchronous detection segment For the above, the distributed pilot signal is disposed on a carrier whose symbol time and frequency are periodically dispersed, the continuous pilot signal is placed on a carrier of the same frequency in every symbol, and the additional information transmission signal is placed on the same frequency in every symbol. The carrier is arranged on a carrier, and the information transmission signal is placed on a carrier other than the above. For the differential detection segment, the continuous pilot signal is placed on a carrier of the same frequency in every symbol, and the additional information transmission signal is placed on every symbol. All on a carrier of the same frequency And was to be placed in a carrier wave of the frequency that satisfies the periodicity of the frequency arrangement of the scattered pilot signal for the synchronous detector segment adjacent to the termination pilot signal.

Moreover, the receiving device which concerns on this invention is comprised as follows.

(22) An apparatus for receiving and demodulating an OFDM signal generated by any one of the OFDM transmission schemes (1) to (18).

(23) A reception apparatus for receiving and demodulating an OFDM signal generated by any one of (1) to (18) OFDM transmission methods,

Fourier transform means for obtaining a vector sequence representing the phase and amplitude for each carrier by converting the received OFDM signal from a time domain to a signal in a frequency domain by Fourier transform;

First extraction means for extracting a vector group of carriers corresponding to the distributed pilot signal, the termination pilot signal, and the band termination pilot signal from the vector sequence obtained by this means;

First dividing means for dividing the vector group extracted by the means into the specific phase and amplitude modulating the distributed pilot signal, the terminated pilot signal, and the band terminated pilot signal;

Filter means for smoothing and interpolating the output of the means in the frequency direction and the symbol time direction;

Delay means for delaying the vector sequence obtained by the Fourier transform means by one symbol period;

Selection means for selecting and outputting the output of the filter means when processing the signal of the synchronous detection segment, and outputting the output of the delay means when processing the signal of the differential detection segment;

And second dividing means for dividing the vector sequence output from the Fourier transforming means into the output signal of the selecting means to obtain a detection vector sequence and output the detection vector sequence.

(24) A receiving apparatus for receiving and demodulating an OFDM signal generated by the OFDM transmission method of (13),

Fourier transform means for obtaining a vector sequence representing the phase and amplitude for each carrier by converting the received OFDM signal from a time domain to a signal in a frequency domain by Fourier transform;

Second extraction means for extracting a vector group of carrier waves corresponding to the continuous pilot signal of the synchronous detection segment and the differential detection segment from the vector sequence obtained by this means;

Third dividing means for dividing the vector group extracted by this means into the specific phase and amplitude modulating the continuous pilot signal;

Inverse Fourier transform means for obtaining the impulse response characteristic of the transmission path by converting the output of the means from the frequency domain to the time domain by an inverse Fourier transform.

Hereinafter, embodiments of an OFDM transmission method according to the present invention, and a transmission device and a reception device suitable for the OFDM transmission method will be described in detail.

(Example 1)

In the OFDM transmission method of the present embodiment, 13 segments and a band-ended pilot using one carrier are used, and one segment is composed of 108 carriers. Each segment is comprised of either a synchronous detection segment or a differential detection segment. In the entire band, a carrier of 1405 carriers is used.

Fig. 1 shows an arrangement example of a synchronous detection or differential detection segment (13 segments in total) and a band-ended pilot signal. The horizontal axis represents the frequency axis (carrier arrangement), and the vertical axis represents the time axis (symbol direction). Carrier number k 'in each segment is made into an integer of 0-107, and one segment consists of a carrier of 108 carriers.

The synchronous detection segment is composed of a distributed pilot signal using a carrier of 9 carriers per symbol, an additional information transmission signal using a carrier of 3 carriers, and an information transmission signal using a carrier of 96 carriers.

The differential detection segment is composed of an additional information transmission signal using a carrier of 11 carriers, an end pilot signal using a carrier of 1 carrier, and an information transmission signal using a carrier of 96 carriers.

As described above, the same number of carriers are used in the synchronous detection segment and the differential detection segment, so that the required transmission band is not changed by the combination of the segments.

Here, the carrier number k in the entire band is an integer of 0 to 1404, the segment number i is an integer of 0 to 12, and the carrier number k 'in each segment is an integer of 0 to 107, and k = i.108 + k'. Shall be satisfied.

The distributed pilot signal provided in the synchronous detection segment is also arranged in the carrier of carrier number k 'in the segment according to equation (5) with each segment. In Equation 5, mod represents a surplus operation, n representing a symbol number is an integer of 0 or more, p is an integer of 0 or more and 8 or less.

The additional information transmission signals provided in the synchronization segment and the differential detection segment are arranged on the carrier of carrier number k 'in each segment shown in Table 1, respectively. Table 1 shows that the additional information transmission signal of the synchronous detection segment is included in the additional information transmission signal of the differential detection segment.

With the above configuration, even if the synchronous detection segment and the differential detection segment are in a mixed state, the additional information transmission signal is necessarily arranged on the carrier wave defined as the additional information transmission signal of the synchronous detection segment. Identification of other transmission signals is facilitated at the receiving side. In addition, the carrier may be allocated based on the additional information transmitted so as not to cause a subset arrangement.

The terminal pilot signal provided in the differential detection segment is arranged on a carrier whose carrier number k 'in each segment is zero. The arrangement of the termination pilot signals is a position that maintains the periodicity of the frequency arrangement of the distributed pilot signals of the adjacent sync detection segments. Each end pilot signal supplements a corresponding distributed pilot signal.

2 shows an example of arrangement of distributed pilot signals in the synchronous detection segment and arrangement of termination pilot signals in the differential detection segment. The horizontal axis represents the frequency axis (carrier arrangement), and the vertical axis represents the time axis (symbol direction). Carrier number k 'in each segment is made into an integer of 0-107, and one segment consists of a carrier of 108 carriers. The side information transmission signal is assigned to a carrier different from that of the distributed pilot signal.

These distributed pilot signals and the end pilot signals are assigned to the PN (pseudo random number) series w _k (wk = 0, 1) corresponding to the carrier number k (determined by segment number i and carrier number k 'in each segment) disposed, respectively. On the basis of this, it is obtained by modulating the carrier wave by the complex vector c _{k, n} shown in the equation (6). In Equation 6, Re {c _{k, n} } represents a real part of a complex vector c _{k, n} corresponding to a carrier number k and a symbol number n, and Im {c _{k, n} } represents an imaginary part.

The additional information transmission signal provided in the synchronous detection segment and the differential detection segment is used to transmit additional information different from the information transmission signal transmitted using a carrier of 96 carriers. For example, control information defining a transmission mode (number of segments, carrier modulation scheme, etc.), information used as a broadcasting station (for example, control information used by a relay station, and low time delay voice used for a live broadcast conversation). Information, a broadcast station identification signal, and the like). One bit of additional information may be transmitted for each symbol or a plurality of bits of additional information may be transmitted. It is also possible to transmit only control information that defines the transmission mode.

Here, if the control information bit transmitted by the symbol of symbol number n is Sn, the control information signal is obtained by modulating the carrier wave by the complex vector c _{k, n} shown in equation (7). That is, in this case, the carrier wave transmitting the control information signal is differentially shifted keyed (PSK) modulated between symbols.

However, at the head symbol of the frame (symbol number n = 0), the carrier wave which transmits the control information is modulated by the complex vectors c _{k, n} shown in Equation 8 based on the PN series w _k described above.

In addition, in the case of transmitting 2 bits of control information for each symbol, for example, differential 4-phase PSK modulation between symbols is used, or a plurality of carriers for transmitting control information are divided into two groups, respectively, for each symbol. It may be allocated to transmit one bit at a time.

The information transmission signal provided in the synchronous detection segment is disposed on carriers other than the above-described distributed pilot signal and additional information transmission signal of the synchronous detection segment, and absolute phase modulation is performed based on digital information. For example, QPSK, 16QAM, 64QAM modulation, or the like is used for this absolute phase modulation.

The information transmission signal of the synchronous detection segment is demodulated by the following processing. First, the distributed pilot signal, the required termination pilot signal, and the band termination pilot signal are inversely modulated by a complex vector modulating the corresponding dispersion pilot, the termination pilot signal, and the band termination pilot signal, and the frequencies related to the distributed pilot signal, the termination pilot signal, and the like. Estimate the channel characteristics from the area. In addition, the transmission path characteristics of the information transmission signal are estimated by interpolation in the frequency direction and the symbol direction by the filter. The information transmission signal is divided by the transmission path characteristics thus obtained. Accordingly, the information transmission signal can be demodulated from the synchronous detection segment.

The information transmission signal provided in the differential detection segment is disposed on a carrier other than the terminal pilot signal of the aforementioned differential detection segment and the additional information transmission signal, and is differential between adjacent symbols of the same carrier number based on digital information. Modulation is performed.

For example, DBPSK, DQPSK, DAPSK, or the like is used for this differential modulation. The information transmission signal of the differential detection segment can be demodulated by dividing by the information transmission signal of the same carrier number of the previous symbol.

As described above, the OFDM transmission method of this embodiment has a fast change in transmission path characteristics due to the effect of a filter in the synchronous detection segment in the receiving device, and differential demodulation between symbols in the differential detection segment. The reception suitable for mobile reception can be performed. Further, by arbitrarily combining the synchronous detection segment and the differential detection segment for each segment, a flexible service form can be realized without involving fluctuations in transmission bands.

(Example 2)

In the OFDM transmission method of the present embodiment, 13 segments and a band-ended pilot using one carrier are used, and one segment is composed of 108 carriers. Each segment is composed of either a synchronous detection segment or a differential detection segment. In the entire band, a carrier of 1405 carriers is used.

The synchronous detection segment includes a distributed pilot signal using a carrier of 9 carriers per symbol, a continuous pilot signal using a carrier of 2 carriers, and an additional information transmission signal using a carrier of 1 carrier (hereinafter, referred to as a control information signal). And information transmission signal using a carrier of 96 carriers.

The differential detection segment is composed of a continuous pilot signal using a 6 carrier carrier, a control information signal using a 5 carrier carrier, an end pilot signal using a carrier carrier of 1 carrier, and an information transmission signal using a carrier carrier of 96 carriers. do.

Here, carrier number k in the whole band is an integer of 0-1404, segment number i is an integer of 0-12, carrier number k 'in each segment is an integer of 0-107, k = i * 108 + k Shall be satisfied.

The distributed pilot signal provided in the synchronous detection segment is arranged in the carrier of carrier number k 'in the segment according to Equation 5a. In Equation 5a, mod represents a surplus operation, and p is an integer of 0 or more and 8 or less.

The continuous pilot signals provided in the synchronization segment and the differential detection segment are arranged on the carrier of carrier number k 'in each segment shown in Table 2, respectively. Table 2 shows that the continuous pilot signal of the synchronous detection segment is included in the differential pilot continuous pilot signal.

With the above configuration, even when the synchronous detection segment and the differential detection segment are in a mixed state, the continuous pilot signal is necessarily arranged on the carrier defined as the continuous pilot of the synchronous detection segment, and the continuous pilot signal or the other transmission is performed. Identification of the signal is facilitated on the receiving side. In addition, you may allocate a carrier so that it may not become a subset arrangement.

A continuous pilot signal that modulates the carrier with a specific phase and amplitude to a carrier of the same frequency in every symbol can be used as a reference carrier on the receiving side because the frequency, phase, and amplitude are specified.

The terminal pilot signal provided in the differential detection segment is arranged on a carrier whose carrier number k 'in each segment is zero. The arrangement of the termination pilot signals is a position that maintains the periodicity of the frequency arrangement of the distributed pilot signals of the adjacent sync detection segments. Each end pilot signal supplements a corresponding distributed pilot signal.

3 shows an arrangement of the continuous pilot signal and the control information signal, an arrangement of the distributed pilot signal in the synchronous detection segment, and an arrangement example of the termination pilot signal in the differential detection segment. The horizontal axis represents the frequency axis (carrier arrangement), and the vertical axis represents the time axis (symbol direction). Carrier number k 'in each segment is made into an integer of 0-107, and one segment consists of a carrier of 108 carriers. The continuous pilot signal and the control information signal are assigned to carriers different from the distributed pilot signal.

These distributed pilot signals, continuous pilot signals, and end pilot signals are each PN (pseudo random number) series w _k (w _k = corresponding to the carrier number k (determined by segment number i and carrier number k 'in each segment) disposed. Based on 0, 1), a carrier wave is modulated by the complex vectors c _{k and n} shown in Equation 6a. In Equation 6a, Re {c _{k, n} } represents a real part of a complex vector c _{k, n} corresponding to a carrier of carrier number k and symbol number n, and Im {c _{k, n} } represents an imaginary part.

The control information signals provided in the synchronous detection segment and the differential detection segment are each arranged on a carrier of carrier number k 'in each segment shown in Table 3, and transmit one bit of control information for each symbol.

If the control information bit transmitted by the symbol of symbol number n is Sn, the control information signal is obtained by modulating the carrier wave by the complex vector c _{k, n} shown in equation (7a). In other words, the carrier for transmitting the control information signal is differentially shift keyed (PSK) modulated between symbols.

However, at the head symbol of the frame (symbol number n = 0), the carrier wave for transmitting control information is modulated by the complex vector c _{k, n} shown in Equation 8a based on the above-described PN series w _k .

In addition, when transmitting 2-bit control information per symbol, for example, differential four-phase PSK modulation between symbols is used.

The information transmission signal provided in the synchronous detection segment is disposed on carriers other than the distributed pilot signal, the continuous pilot signal, and the control information signal of the synchronous detection segment described above, and absolute phase modulation is performed based on digital information. For example, QPSK, 16QAM, 64QAM modulation, or the like is used for this absolute phase modulation.

The information transmission signal of the synchronous detection segment is demodulated by the following processing. First, the distributed pilot signal, the required termination pilot signal, and the band termination pilot signal are inversely modulated by a complex vector modulating the corresponding dispersion pilot, the termination pilot signal, and the band termination pilot signal. Estimate the channel characteristics from The filter also estimates transmission line characteristics for the information transmission signal by interpolating in the frequency direction and the symbol direction. The information transmission signal is divided by the transmission path characteristics thus obtained. Accordingly, the information transmission signal can be demodulated from the synchronous detection segment.

The information transmission signal provided in the differential detection segment is disposed on a carrier other than the continuous pilot signal, the termination pilot signal, and the control information signal of the differential detection segment described above, and is located between adjacent symbols of the same carrier number based on digital information. Differential modulation is performed.

For example, DBPSK, DQPSK, DAPSK, or the like is used for this differential modulation. The information transmission signal of the differential detection segment can be demodulated as divided by the information transmission signal of the same carrier number of the previous symbol.

As described above, in the OFDM transmission method of the present embodiment, the transmission device has a high quality reception due to the effect of a filter in the synchronous detection segment, and differential demodulation between symbols in the differential detection segment. Receiving suitable for fast mobile reception can be performed. Furthermore, by arbitrarily combining the synchronous detection segment and the differential detection segment for each segment, a flexible service form can be realized.

In addition, since every symbol has a continuous pilot signal for modulating the carrier wave in a specific phase and amplitude on a carrier wave of the same frequency, the frequency, phase, and amplitude are specified, so that the receiver can be used as a reference carrier.

4 and 5 show inverse Fourier transform pairs in frequency configuration of continuous pilot signals of the synchronous detection segment (13 segments, 26 carriers) and the differential detection segment (13 segments, 78 carriers) shown in Table 2, respectively. 4 and 5 show that these are impulse shapes, and the frequency arrangement of the continuous pilot signals shown in Table 2 does not have periodicity.

From this, the OFDM transmission method of this embodiment can prevent the entire continuous pilot signal from disappearing by delay waves such as multipath. In addition, the inverse Fourier transform can be used to obtain the impulse response of the transmission path. In addition, the frequency configuration of the continuous pilot signal is a configuration that is strong in autocorrelation.

6 and 7 show inverse Fourier transform pairs of frequency configuration of the control information signals of the synchronous detection segment and the differential detection segment shown in Table 3, respectively. It can be seen from FIG. 6 and FIG. 7 that these have an impulse shape and that the frequency arrangement of the control information signals shown in Table 3 has no periodicity.

As described above, the OFDM transmission method of the present embodiment can prevent the entire control information signal from disappearing by delay waves such as multipath.

In addition, the frequency configuration of the additional information transmission signal including the control information signal can be set similarly.

(Example 3)

Fig. 8 shows a configuration of an embodiment of a transmitter for generating an OFDM signal based on the OFDM transmission schemes of the first and second embodiments.

In Fig. 8, the information transmission signal generation circuit 51 performs error control processing (error correction code (ECC) conversion, interleaving, energy diffusion, etc.) and digital modulation as necessary for the digital information to be input. In addition, the basic error control processing method and the digital modulation method generally used in digital transmission are omitted since they are well known techniques.

In the synchronous detection segment, absolute phase modulation is performed as digital modulation. For example, QPSK, 16QAM, 64QAM modulation, or the like is used for this absolute phase modulation. In the differential detection segment, differential modulation is performed between adjacent symbols of the same carrier number based on digital information. For example, DBPSK, DQPSK, DAPSK, or the like is used for this differential modulation.

The additional information signal generation circuit 52 performs error control processing (error correction code (ECC) conversion, interleaving, energy diffusion, etc.) and digital modulation as necessary for the additional information to be input. As digital modulation, M (M is two or more natural numbers) phase PSK (Phase Shift Keying) modulation, differential M phase PSK modulation in the symbol direction, or the like is used.

The control information generation circuit 56 generates transmission mode information (various information for defining the transmission mode such as the number of synchronous detection segments, the number of differential detection segments, and the carrier modulation method) required on the receiving side. Although this information is subjected to error control processing and digital modulation in the additional information signal generation circuit 52, error control processing and digital modulation different from other additional information may be performed.

The distributed pilot signal generation circuit 53 is a pseudo random number (PN) sequence w corresponding to the carrier number k (determined by the segment number i and the carrier number k 'in each segment) whose arrangement is defined by the carrier arrangement circuit 57. Generate a distributed pilot signal modulated based on _k (w _k = 0, 1).

The termination pilot signal generation circuit 54 is a pseudo random number (PN) sequence w corresponding to the carrier number k (determined by the segment number i and the carrier number k 'in each segment) in which the arrangement is defined in the carrier arrangement circuit 57. Generate a modulated termination pilot signal based on _k (w _k = 0, 1).

The band termination pilot signal generation circuit 55 generates a band termination pilot signal modulated based on the PN (pseudo random number) sequence w _k (w _k = 0, 1) corresponding to the carrier number k of the band termination.

Although the continuous pilot signal is not specifically described, it is assumed that the additional information signal generation circuit 52 modulates the carrier with the same phase and amplitude of the symbol.

In the carrier arrangement circuit 57, the information transmission signal generation circuit 51, the additional information signal generation circuit 52, the distributed pilot signal generation circuit 53, the termination pilot signal generation circuit 54, and the band termination pilot signal generation circuit Each output (complex vector string) of 55 is arranged at a carrier position in the frequency domain defined by the transmission mode.

For example, the output of the distributed pilot signal generation circuit 53 is disposed on a carrier shifted by N (N is a natural number of two or more) carrier intervals and L (L is a weak number of N) carriers per symbol in the synchronous detection segment. . The output of the termination pilot signal generation circuit 54 is disposed in the carrier whose carrier number k '= 0 in the segment in the differential detection segment. In addition, the output of the additional information signal generation circuit 52 is allocated according to the frequency arrangement shown in Table 1, for example. The vector sequence for each carrier wave of the base frequency band arranged in this way is input to the inverse Fourier transform circuit 58.

The inverse Fourier transform circuit 58 converts the vector sequence from the frequency domain to the time domain for each carrier of the base frequency band generated by the carrier arrangement circuit 57, and adds a guard interval period that is normally used. The quadrature modulation circuit 59 orthogonally modulates the output of the inverse Fourier transform circuit 58 and converts it into an intermediate frequency band. The frequency conversion circuit 60 converts the frequency band of the orthogonally modulated OFDM signal from the intermediate frequency band to the radio frequency band and supplies it to an antenna or the like.

According to the transmission apparatus having the above configuration, it is possible to generate an OFDM signal based on the OFDM transmission scheme described in the first and second embodiments.

(Example 4)

Fig. 9 shows a configuration of a receiving apparatus capable of receiving an OFDM signal formed based on the OFDM transmission schemes of the first and second embodiments and estimating an impulse response in the time domain of the transmission path.

In Fig. 9, the tuner 11 converts the frequency band of the received OFDM signal from the radio frequency band to the base frequency band. The Fourier transform circuit 12 converts the OFDM signal in the base frequency band from the time domain to the frequency domain and outputs it as a vector string for each carrier in the frequency domain.

The distributed / terminated pilot extraction circuit 13 extracts the distributed pilot signal, the necessary termination pilot signal, and the band termination pilot signal from the vector sequence outputted by the Fourier transform circuit 12. The vector generation circuit 14 generates a modulation complex vector c _{k, n} corresponding to the distributed pilot signal, the end pilot signal, and the band end pilot signal extracted by the distributed / end pilot extraction circuit 13.

The division circuit 15 divides the distributed pilot signal, the termination pilot signal, and the band termination pilot signal extracted by the dispersion / end pilot extraction circuit 13 into a complex vector generated by the vector generation circuit 14, The channel characteristics of the end pilot signal and the band end pilot signal are estimated. The interpolation circuit 16 interpolates the transmission characteristics of the distributed pilot signal, the termination pilot signal, and the band termination pilot signal obtained by the division circuit 15, and the transmission characteristics of the carrier of the information transmission signal of the synchronous detection segment. Estimate

The delay circuit 17 delays the vector string output by the Fourier transform circuit 12 by one symbol. The selection circuit 18 outputs the output of the interpolation circuit 16 in the case of the synchronous detection segment and the output of the delay circuit 17 in the case of the differential detection segment according to the type of the segment separately transmitted by the control information. Select and print.

The division circuit 19 divides the vector sequence output from the Fourier transform circuit 12 into the output of the selection circuit 18, respectively. In the division circuit 19, in the synchronous detection segment, the synchronous detection is performed by dividing by the transmission line characteristics for each corresponding carrier estimated by the interpolation circuit 16, and in the differential detection segment, the delay circuit 17 is output. The differential detection is performed by dividing by one carrier vector sequence corresponding to one symbol before.

The demodulation circuit 20 demodulates the detection signal output from the division circuit 19 according to a modulation method (QPSK, 16QAM, 64QAM, DBPSK, DQPSK, DAPSK, etc.) when generating the information transmission signal, and transmits the transmitted digital information. Get

With the above configuration, it is possible to receive and demodulate an OFDM signal based on the OFDM transmission method described in the first embodiment. The configuration described below is for receiving and demodulating an OFDM signal based on the OFDM transmission method described in the second embodiment.

First, the continuous pilot extraction circuit 21 extracts the continuous pilot signal from the vector string output by the Fourier transform circuit 12. At this time, even when the synchronous detection segment and the differential detection segment are mixed, at least the continuous pilot signal of the synchronous detection segment is always mixed, so that the continuous pilot signal can be extracted at all times.

The vector generation circuit 22 generates a modulation complex vector c _{k, n} corresponding to the continuous pilot signal extracted by the continuous pilot extraction circuit 21. The division circuit 23 divides the continuous pilot signal extracted by the continuous pilot extraction circuit 21 into a complex vector generated by the vector generation circuit 22 to estimate the transmission path characteristics of the continuous pilot signal. The inverse Fourier transform circuit 24 converts the transmission path characteristic of the continuous pilot signal estimated by the division circuit 23 from the frequency domain to the time domain to obtain an impulse response characteristic of the transmission path.

As mentioned above, according to the structure of the receiving apparatus of this embodiment, in the demodulation circuit 20, in the synchronous detection segment, high quality demodulation can be realized by the filter effect by the interpolation process of the transmission line characteristics, and the differential detection segment By demodulating between symbols, demodulation suitable for mobile reception with fast change in transmission line characteristics can be realized. In addition, in the inverse Fourier transform circuit 24, an impulse response characteristic of a transmission path with no return can be obtained.

As described above, the orthogonal frequency division multiplexing scheme of the present invention may include a differential detection segment suitable for mobile reception. At this time, by including the termination pilot signal and the band termination pilot signal, the synchronous detection segment and the differential detection segment can be freely combined for each segment without impairing the synchronous detection characteristics of the adjacent synchronous detection segments. Accordingly, a flexible service type can be realized.

In addition, by using a continuous pilot signal having an inverse Fourier transform pair in frequency configuration, an impulse response characteristic of a transmission path without a return during a symbol period may be obtained as necessary.

Therefore, according to the present invention, a modulation scheme suitable for mobile reception is partially introduced into modulation of a carrier for transmitting digital information while maintaining the entire transmission capacity, and, for example, an impulse response of a transmission path estimated from a continuous pilot signal, for example. An OFDM transmission method in which a continuous pilot signal is arranged so that a return does not occur, and a transmitting device and a receiving device suitable for the present method can be provided.

As mentioned above, although the invention made by this inventor was demonstrated concretely according to the said Example, this invention is not limited to the said Example and can be variously changed in the range which does not deviate from the summary.

Claims (12)

A transmission method for transmitting digital information as an OFDM signal, The OFDM signal includes at least two segments composed of a plurality of carriers which are continuous in frequency, The segment is either a synchronous detection segment or a differential detection segment, The synchronous detection segment includes a carrier to which an information transmission signal is assigned, The differential detection segment includes a carrier to which an information transmission signal is assigned, The information transmission signal of the synchronous detection segment is an absolute phase modulation of each assigned carrier based on the digital information, The information transmission signal of the differential detection segment is a differential modulation of each assigned carrier based on the digital information, The number of carriers constituting the synchronous detection segment and the differential detection segment are the same, respectively. The number of carriers to which the information transmission signal is allocated is the same for the synchronous detection segment and the differential detection segment. Transmission method. The method of claim 1, The absolute phase modulation is any one of QPSK modulation, 16 QAM modulation, 64 QAM modulation. The method of claim 1, The differential modulation is DQPSK modulation. A reception method for receiving an OFDM signal and restoring digital information, The OFDM signal includes at least two segments composed of a plurality of carriers which are continuous in frequency, The segment is either a synchronous detection segment or a differential detection segment, The synchronous detection segment includes a carrier to which an information transmission signal is assigned, The differential detection segment includes a carrier to which an information transmission signal is assigned, The information transmission signal of the synchronous detection segment is an absolute phase modulation of each assigned carrier based on the digital information, The information transmission signal of the differential detection segment is a differential modulation of each assigned carrier based on the digital information, The number of carriers constituting the synchronous detection segment and the differential detection segment are the same, respectively. For the synchronous detection segment and the differential detection segment, the number of carriers to which the information transmission signal is allocated is the same, Receiving the OFDM signal and performing Fourier transform to restore the digital information. Receiving method. The method of claim 4, wherein The absolute phase modulation is any one of QPSK modulation, 16 QAM modulation, 64 QAM modulation. The method of claim 4, wherein And the differential modulation is DQPSK modulation. A transmitter for transmitting digital information as an OFDM signal, Carrier arranging means for allocating an information transmission signal to a predetermined carrier; Inverse Fourier transform means for generating the OFDM signal by inverse Fourier transforming the output of the carrier placement means, The OFDM signal includes at least two segments composed of a plurality of carriers which are continuous in frequency, The segment is either a synchronous detection segment or a differential detection segment, The synchronous detection segment includes a carrier to which an information transmission signal is assigned, The differential detection segment includes a carrier to which an information transmission signal is assigned, The information transmission signal of the synchronous detection segment is an absolute phase modulation of each assigned carrier based on the digital information, The information transmission signal of the differential detection segment is a differential modulation of each assigned carrier based on the digital information, The number of carriers constituting the synchronous detection segment and the differential detection segment are the same, respectively. The number of carriers to which the information transmission signal is allocated is the same for the synchronous detection segment and the differential detection segment. Transmitting device. The method of claim 7, wherein The absolute phase modulation is any one of QPSK modulation, 16 QAM modulation, and 64 QAM modulation. The method of claim 7, wherein The differential modulation is DQPSK modulation. A receiving device for receiving an OFDM signal and restoring digital information, The OFDM signal includes at least two segments composed of a plurality of carriers which are continuous in frequency, The segment is either a synchronous detection segment or a differential detection segment, The synchronous detection segment includes a carrier to which an information transmission signal is assigned, The differential detection segment includes a carrier to which an information transmission signal is assigned, The information transmission signal of the synchronous detection segment is an absolute phase modulation of each assigned carrier based on the digital information, The information transmission signal of the differential detection segment is a differential modulation of each assigned carrier based on the digital information, The number of carriers constituting the synchronous detection segment and the differential detection segment are the same, respectively. For the synchronous detection segment and the differential detection segment, the number of carriers to which the information transmission signal is allocated is the same, And Fourier transform means for receiving the OFDM signal and performing Fourier transform. Receiving device. The method of claim 10, The absolute phase modulation is any one of QPSK modulation, 16 QAM modulation, 64 QAM modulation. The method of claim 10, And the differential modulation is DQPSK modulation.

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